bims-cagime Biomed News
on Cancer, aging and metabolism
Issue of 2021‒02‒21
seventy-six papers selected by
Kıvanç Görgülü
Technical University of Munich


  1. Sci Adv. 2021 Feb;pii: eabf0717. [Epub ahead of print]7(8):
    Schober FA, Moore D, Atanassov I, Moedas MF, Clemente P, Végvári Á, Fissi NE, Filograna R, Bucher AL, Hinze Y, The M, Hedman E, Chernogubova E, Begzati A, Wibom R, Jain M, Nilsson R, Käll L, Wedell A, Freyer C, Wredenberg A.
      Induction of the one-carbon cycle is an early hallmark of mitochondrial dysfunction and cancer metabolism. Vital intermediary steps are localized to mitochondria, but it remains unclear how one-carbon availability connects to mitochondrial function. Here, we show that the one-carbon metabolite and methyl group donor S-adenosylmethionine (SAM) is pivotal for energy metabolism. A gradual decline in mitochondrial SAM (mitoSAM) causes hierarchical defects in fly and mouse, comprising loss of mitoSAM-dependent metabolites and impaired assembly of the oxidative phosphorylation system. Complex I stability and iron-sulfur cluster biosynthesis are directly controlled by mitoSAM levels, while other protein targets are predominantly methylated outside of the organelle before import. The mitoSAM pool follows its cytosolic production, establishing mitochondria as responsive receivers of one-carbon units. Thus, we demonstrate that cellular methylation potential is required for energy metabolism, with direct relevance for pathophysiology, aging, and cancer.
    DOI:  https://doi.org/10.1126/sciadv.abf0717
  2. Sci Adv. 2021 Feb;pii: eabe0174. [Epub ahead of print]7(8):
    Augereau A, Mariotti M, Pousse M, Filipponi D, Libert F, Beck B, Gorbunova V, Gilson E, Gladyshev VN.
      The naked mole rat (NMR), a long-lived and cancer-resistant rodent, is highly resistant to hypoxia. Here, using robust cellular models wherein the mouse telomeric protein TRF1 is substituted by NMR TRF1 or its mutant forms, we show that TRF1 supports maximal glycolytic capacity under low oxygen, shows increased nuclear localization and association with telomeres, and protects telomeres from replicative stress. We pinpoint this evolutionary gain of metabolic function to specific amino acid changes in the homodimerization domain of this protein. We further find that NMR TRF1 accelerates telomere shortening. These findings reveal an evolutionary strategy to adapt telomere biology for metabolic control under an extreme environment.
    DOI:  https://doi.org/10.1126/sciadv.abe0174
  3. Cancer Discov. 2021 Feb 15. pii: candisc.1098.2020. [Epub ahead of print]
    Pitarresi JR, Norgard RJ, Chiarella AM, Suzuki K, Bakir B, Sahu V, Li J, Zhao J, Marchand B, Wengyn MD, Hsieh A, Kim IK, Zhang A, Sellin K, Lee V, Takano S, Miyahara Y, Ohtsuka M, Maitra A, Notta F, Kremer R, Stanger BZ, Rustgi AK.
      Pancreatic cancer metastasis is a leading cause of cancer-related deaths, yet very little is understood regarding the underlying biology. As a result, targeted therapies to inhibit metastasis are lacking. Here, we report that the parathyroid hormone-related protein (PTHrP encoded by PTHLH) is frequently amplified as part of the KRAS amplicon in pancreatic cancer patients. PTHrP upregulation drives the growth of both primary and metastatic tumors in mice and is highly enriched in PDAC metastases. Loss of PTHrP - either genetically or pharmacologically - dramatically reduces tumor burden, eliminates metastasis, and enhances overall survival. These effects are mediated in part through a reduction in epithelial-to-mesenchymal transition, which reduces the tumor cells' ability to initiate the metastatic cascade. Spp1, which encodes Osteopontin, is revealed to be a downstream effector of PTHrP. Our results establish a new paradigm in pancreatic cancer whereby PTHrP is a driver of disease progression and emerges as a novel therapeutic vulnerability.
    DOI:  https://doi.org/10.1158/2159-8290.CD-20-1098
  4. Mol Cell Proteomics. 2020 Dec 08. pii: S1535-9476(20)35126-4. [Epub ahead of print]20 100012
    McDowell CT, Klamer Z, Hall J, West CA, Wisniewski L, Powers TW, Angel PM, Mehta AS, Lewin DN, Haab BB, Drake RR.
      The early detection of pancreatic ductal adenocarcinoma (PDAC) is a complex clinical obstacle yet is key to improving the overall likelihood of patient survival. Current and prospective carbohydrate biomarkers carbohydrate antigen 19-9 (CA19-9) and sialylated tumor-related antigen (sTRA) are sufficient for surveilling disease progression yet are not approved for delineating PDAC from other abdominal cancers and noncancerous pancreatic pathologies. To further understand these glycan epitopes, an imaging mass spectrometry (IMS) approach was used to assess the N-glycome of the human pancreas and pancreatic cancer in a cohort of patients with PDAC represented by tissue microarrays and whole-tissue sections. Orthogonally, these same tissues were characterized by multiround immunofluorescence that defined expression of CA19-9 and sTRA as well as other lectins toward carbohydrate epitopes with the potential to improve PDAC diagnosis. These analyses revealed distinct differences not only in N-glycan spatial localization across both healthy and diseased tissues but importantly between different biomarker-categorized tissue samples. Unique sulfated biantennary N-glycans were detected specifically in normal pancreatic islets. N-glycans from CA19-9-expressing tissues tended to be biantennary, triantennary, and tetra-antennary structures with both core and terminal fucose residues and bisecting GlcNAc. These N-glycans were detected in less abundance in sTRA-expressing tumor tissues, which favored triantennary and tetra-antennary structures with polylactosamine extensions. Increased sialylation of N-glycans was detected in all tumor tissues. A candidate new biomarker derived from IMS was further explored by fluorescence staining with selected lectins on the same tissues. The lectins confirmed the expression of the epitopes in cancer cells and revealed different tumor-associated staining patterns between glycans with bisecting GlcNAc and those with terminal GlcNAc. Thus, the combination of lectin-immunohistochemistry and lectin-IMS techniques produces more complete information for tumor classification than the individual analyses alone. These findings potentiate the development of early assessment technologies to rapidly and specifically identify PDAC in the clinic that may directly impact patient outcomes.
    Keywords:  CA19-9; MALDI; N-glycans; biomarkers; glycosylation; imaging mass spectrometry; lectins; pancreatic cancer
    DOI:  https://doi.org/10.1074/mcp.RA120.002256
  5. Proc Natl Acad Sci U S A. 2021 Feb 23. pii: e2012469118. [Epub ahead of print]118(8):
    Moore AM, Zhou L, Cui J, Li L, Wu N, Yu A, Poddar S, Liang K, Abt ER, Kim S, Ghukasyan R, Khachatourian N, Pagano K, Elliott I, Dann AM, Riahi R, Le T, Dawson DW, Radu CG, Donahue TR.
      Emerging evidence suggests that intratumoral interferon (IFN) signaling can trigger targetable vulnerabilities. A hallmark of pancreatic ductal adenocarcinoma (PDAC) is its extensively reprogrammed metabolic network, in which nicotinamide adenine dinucleotide (NAD) and its reduced form, NADH, are critical cofactors. Here, we show that IFN signaling, present in a subset of PDAC tumors, substantially lowers NAD(H) levels through up-regulating the expression of NAD-consuming enzymes PARP9, PARP10, and PARP14. Their individual contributions to this mechanism in PDAC have not been previously delineated. Nicotinamide phosphoribosyltransferase (NAMPT) is the rate-limiting enzyme in the NAD salvage pathway, a dominant source of NAD in cancer cells. We found that IFN-induced NAD consumption increased dependence upon NAMPT for its role in recycling NAM to salvage NAD pools, thus sensitizing PDAC cells to pharmacologic NAMPT inhibition. Their combination decreased PDAC cell proliferation and invasion in vitro and suppressed orthotopic tumor growth and liver metastases in vivo.
    Keywords:  NAD; NAMPT; PARP; interferon; pancreatic cancer
    DOI:  https://doi.org/10.1073/pnas.2012469118
  6. J Biol Chem. 2021 Feb 15. pii: S0021-9258(21)00201-5. [Epub ahead of print] 100428
    Darling NJ, Arthur JSC, Cohen P.
      Cytokines and chemokines are important regulators of airway hyper-responsiveness, immune cell infiltration and inflammation, and are produced when mast cells are stimulated with interleukin-33 (IL-33). Here we establish that the Salt-Inducible Kinases (SIKs) are required for the IL-33-stimulated transcription of il13, gm-csf and tnf and hence the production of these cytokines. The IL-33-stimulated secretion of IL-13, GM-CSF and TNF was strongly reduced in foetal liver-derived mast cells from mice expressing a kinase-inactive mutant of SIK3 and abolished in cells expressing kinase-inactive mutants of SIK2 and SIK3. The IL-33-dependent secretion of these cytokines and several chemokines was also abolished in SIK2/3 double knock-out (KO) bone marrow-derived mast cells (BMMC), reduced in SIK3 KO cells but little affected in BMMC expressing kinase-inactive mutants of SIK1 and SIK2 or lacking SIK2 expression. In SIK2 KO BMMC the expression of SIK3 was greatly increased. Our studies identify essential roles for SIK2 and SIK3 in producing inflammatory mediators that trigger airway inflammation. The effects of SIKs were independent of IKKβ, IKKβ-mediated NF-κB-dependent gene transcription and activation of the MAP kinase family members p38α and JNKs. Our results suggest that dual inhibitors of SIK2 and SIK3 may have therapeutic potential for the treatment of mast cell-driven diseases.
    Keywords:  Asthma; chemokine; granulocyte-macrophage colony stimulating factor (GM-CSF); innate immunity; interleukin-13 (IL-13); interleukin-33 (IL-33); mast cells; protein kinase; salt-inducible kinase (SIK); tumour necrosis factor (TNF)
    DOI:  https://doi.org/10.1016/j.jbc.2021.100428
  7. Elife. 2021 Feb 17. pii: e62574. [Epub ahead of print]10
    Malaguti G, Ten Wolde PR.
      Living cells often need to measure chemical concentrations that vary in time, yet how accurately they can do so is poorly understood. Here, we present a theory that fully specifies, without any adjustable parameters, the optimal design of a canonical sensing system, in terms of two elementary design principles: (1) there exists an optimal integration time, which is determined by the input statistics and the number of receptors; (2) in the optimally designed system, the number of independent concentration measurements as set by the number of receptors and the optimal integration time, equals the number of readout molecules that store these measurements, and equals the work to store these measurements reliably; no resource is then in excess and hence wasted. Applying our theory to the E.coli chemotaxis system indicates that its integration time is not only optimal for sensing shallow gradients, but also necessary to enable navigation in these gradients.
    Keywords:  E. coli; physics of living systems
    DOI:  https://doi.org/10.7554/eLife.62574
  8. Proc Natl Acad Sci U S A. 2021 Feb 16. pii: e2020838118. [Epub ahead of print]118(7):
    Pienta KJ, Hammarlund EU, Brown JS, Amend SR, Axelrod RM.
      We present a unifying theory to explain cancer recurrence, therapeutic resistance, and lethality. The basis of this theory is the formation of simultaneously polyploid and aneuploid cancer cells, polyaneuploid cancer cells (PACCs), that avoid the toxic effects of systemic therapy by entering a state of cell cycle arrest. The theory is independent of which of the classically associated oncogenic mutations have already occurred. PACCs have been generally disregarded as senescent or dying cells. Our theory states that therapeutic resistance is driven by PACC formation that is enabled by accessing a polyploid program that allows an aneuploid cancer cell to double its genomic content, followed by entry into a nondividing cell state to protect DNA integrity and ensure cell survival. Upon removal of stress, e.g., chemotherapy, PACCs undergo depolyploidization and generate resistant progeny that make up the bulk of cancer cells within a tumor.
    Keywords:  drug resistance; evolution; metastasis; tumor microenvironment; whole-genome doubling
    DOI:  https://doi.org/10.1073/pnas.2020838118
  9. Curr Biol. 2021 Feb 09. pii: S0960-9822(21)00061-0. [Epub ahead of print]
    Adams SD, Csere J, D'angelo G, Carter EP, Romao M, Arnandis T, Dodel M, Kocher HM, Grose R, Raposo G, Mardakheh F, Godinho SA.
      Bidirectional communication between cells and their surrounding environment is critical in both normal and pathological settings. Extracellular vesicles (EVs), which facilitate the horizontal transfer of molecules between cells, are recognized as an important constituent of cell-cell communication. In cancer, alterations in EV secretion contribute to the growth and metastasis of tumor cells. However, the mechanisms underlying these changes remain largely unknown. Here, we show that centrosome amplification is associated with and sufficient to promote small extracellular vesicle (SEV) secretion in pancreatic cancer cells. This is a direct result of lysosomal dysfunction, caused by increased reactive oxygen species (ROS) downstream of extra centrosomes. We propose that defects in lysosome function could promote multivesicular body fusion with the plasma membrane, thereby enhancing SEV secretion. Furthermore, we find that SEVs secreted in response to amplified centrosomes are functionally distinct and activate pancreatic stellate cells (PSCs). These activated PSCs promote the invasion of pancreatic cancer cells in heterotypic 3D cultures. We propose that SEVs secreted by cancer cells with amplified centrosomes influence the bidirectional communication between the tumor cells and the surrounding stroma to promote malignancy.
    Keywords:  PDAC; ROS; cancer; centrosome amplification; exosomes; extracellular vesicles; invasion; lysosomes; multivesicular bodies; stellate cells
    DOI:  https://doi.org/10.1016/j.cub.2021.01.028
  10. Trends Biochem Sci. 2021 Feb 13. pii: S0968-0004(21)00020-7. [Epub ahead of print]
    King KE, Losier TT, Russell RC.
      Autophagy is the primary catabolic program of the cell that promotes survival in response to metabolic stress. It is tightly regulated by a suite of kinases responsive to nutrient status, including mammalian target of rapamycin complex 1 (mTORC1), AMP-activated protein kinase (AMPK), protein kinase C-α (PKCα), MAPK-activated protein kinases 2/3 (MAPKAPK2/3), Rho kinase 1 (ROCK1), c-Jun N-terminal kinase 1 (JNK), and Casein kinase 2 (CSNK2). Here, we highlight recently uncovered mechanisms linking amino acid, glucose, and oxygen levels to autophagy regulation through mTORC1 and AMPK. In addition, we describe new pathways governing the autophagic machinery, including the Unc-51-like (ULK1), vacuolar protein sorting 34 (VPS34), and autophagy related 16 like 1 (ATG16L1) enzyme complexes. Novel downstream targets of ULK1 protein kinase are also discussed, such as the ATG16L1 subunit of the microtubule-associated protein 1 light chain 3 (LC3)-lipidating enzyme and the ATG14 subunit of the VPS34 complex. Collectively, we describe the complexities of the autophagy pathway and its role in maintaining cellular nutrient homeostasis during times of starvation.
    Keywords:  AMPK; ATG complexes; amino acids; glucose; mTORC1; oxygen
    DOI:  https://doi.org/10.1016/j.tibs.2021.01.006
  11. Front Physiol. 2020 ;11 615038
    Memme JM, Hood DA.
      Mitochondrial dysfunction is common to many organ system disorders, including skeletal muscle. Aging muscle and diseases of muscle are often accompanied by defective mitochondrial ATP production. This manuscript will focus on the pre-clinical evidence supporting the use of regular exercise to improve defective mitochondrial metabolism and function in skeletal muscle, through the stimulation of mitochondrial turnover. Examples from aging muscle, muscle-specific mutations and cancer cachexia will be discussed. We will also examine the effects of exercise on the important mitochondrial regulators PGC-1α, and Parkin, and summarize the effects of exercise to reverse mitochondrial dysfunction (e.g., ROS production, apoptotic susceptibility, cardiolipin synthesis) in muscle pathology. This paper will illustrate the breadth and benefits of exercise to serve as "mitochondrial medicine" with age and disease.
    Keywords:  aging; cancer; exercise as medicine; mitochondrial quality control; skeletal muscle
    DOI:  https://doi.org/10.3389/fphys.2020.615038
  12. Cancer Res. 2021 Feb 15. pii: canres.2370.2020. [Epub ahead of print]
    Yang B, Li X, Fu Y, Guo E, Ye Y, Li F, Liu S, Xiao R, Liu C, Lu F, Huang J, Qin T, Han L, Peng G, Mills GB, Sun C, Chen G.
      Mutant KRAS tumors are associated with poor outcomes at least in part due to decreased therapeutic sensitivity. Here we show that KRAS mutations are associated with resistance to monotherapy and combination therapy with Poly-(ADP-ribose) polymerase inhibitors (PARPi) and immune checkpoint blockade with anti-PD-L1 antibodies. In mutant KRAS tumors, inhibition of KRAS signaling with MEK inhibitors (MEKi) triggered and amplified PARPi-induced DNA damage, cytosolic double-stranded DNA accumulation, STING pathway activation and CD8+ T cell recruitment. Moreover, MEKi decreased myeloid-derived suppressor cell infiltration in part by inhibiting IL-6 and GM-CSF production. Importantly, addition of MEKi to PARPi and anti-PD-L1 resulted in marked tumor inhibition in immunocompetent mutant KRAS tumor models. These studies provide the underlying mechanistic data to support evaluation of PARPi, MEKi, and anti-PD-L1 combination in clinical trials of mutant KRAS tumors.
    DOI:  https://doi.org/10.1158/0008-5472.CAN-20-2370
  13. Sci Transl Med. 2021 Feb 17. pii: eabd8636. [Epub ahead of print]13(581):
    Lo JA, Kawakubo M, Juneja VR, Su MY, Erlich TH, LaFleur MW, Kemeny LV, Rashid M, Malehmir M, Rabi SA, Raghavan R, Allouche J, Kasumova G, Frederick DT, Pauken KE, Weng QY, Pereira da Silva M, Xu Y, van der Sande AAJ, Silkworth W, Roider E, Browne EP, Lieb DJ, Wang B, Garraway LA, Wu CJ, Flaherty KT, Brinckerhoff CE, Mullins DW, Adams DJ, Hacohen N, Hoang MP, Boland GM, Freeman GJ, Sharpe AH, Manstein D, Fisher DE.
      Although immune checkpoint inhibitors (ICIs), such as anti-programmed cell death protein-1 (PD-1), can deliver durable antitumor effects, most patients with cancer fail to respond. Recent studies suggest that ICI efficacy correlates with a higher load of tumor-specific neoantigens and development of vitiligo in patients with melanoma. Here, we report that patients with low melanoma neoantigen burdens who responded to ICI had tumors with higher expression of pigmentation-related genes. Moreover, expansion of peripheral blood CD8+ T cell populations specific for melanocyte antigens was observed only in patients who responded to anti-PD-1 therapy, suggesting that ICI can promote breakdown of tolerance toward tumor-lineage self-antigens. In a mouse model of poorly immunogenic melanomas, spreading of epitope recognition toward wild-type melanocyte antigens was associated with markedly improved anti-PD-1 efficacy in two independent approaches: introduction of neoantigens by ultraviolet (UV) B radiation mutagenesis or the therapeutic combination of ablative fractional photothermolysis plus imiquimod. Complete responses against UV mutation-bearing tumors after anti-PD-1 resulted in protection from subsequent engraftment of melanomas lacking any shared neoantigens, as well as pancreatic adenocarcinomas forcibly overexpressing melanocyte-lineage antigens. Our data demonstrate that somatic mutations are sufficient to provoke strong antitumor responses after checkpoint blockade, but long-term responses are not restricted to these putative neoantigens. Epitope spreading toward T cell recognition of wild-type tumor-lineage self-antigens represents a common pathway for successful response to ICI, which can be evoked in neoantigen-deficient tumors by combination therapy with ablative fractional photothermolysis and imiquimod.
    DOI:  https://doi.org/10.1126/scitranslmed.abd8636
  14. J Cell Mol Med. 2021 Feb 18.
    Luo X, Qiu Y, Dinesh P, Gong W, Jiang L, Feng X, Li J, Jiang Y, Lei YL, Chen Q.
      Autophagy is frequently induced in the hypoxic tumour microenvironment. Accumulating evidence reveals important functions of autophagy at the tumour-immune interface. Herein, we propose an update on the roles of autophagy in modulating tumour immunity. Autophagy promotes adaptive resistance of established tumours to the cytotoxic effects of natural killer cells (NKs), macrophages and effector T cells. Increased autophagic flux in tumours dampen their immunogenicity and inhibits the expansion of cytotoxic T lymphocytes (CTLs) by suppressing the activation of STING type I interferon signalling (IFN-I) innate immune sensing pathway. Autophagy in suppressive tumour-infiltrating immune subsets maintains their survival through metabolic remodelling. On the other hand, autophagy is involved in the antigen processing and presentation process, which is essential for anti-tumour immune responses. Genetic deletion of autophagy induces spontaneous tumours in some models. Thus, the role of autophagy is context-dependent. In summary, our review has revealed the dichotomous roles of autophagy in modulating tumour immunity. Broad targeting of autophagy may not yield maximal benefits. The characterization of specific genes regulating tumour immunogenicity and innovation in targeted delivery of autophagy inhibitors into certain tumours are among the most urgent tasks to sensitize cold cancers to immunotherapy.
    Keywords:  autophagy; immune cell; tumour cell; tumour immunity
    DOI:  https://doi.org/10.1111/jcmm.16331
  15. Oncogene. 2021 Feb 18.
    Yoon H, Tang CM, Banerjee S, Yebra M, Noh S, Burgoyne AM, Torre J, Siena M, Liu M, Klug LR, Choi YY, Hosseini M, Delgado AL, Wang Z, French RP, Lowy A, DeMatteo RP, Heinrich MC, Molinolo AA, Gutkind JS, Harismendy O, Sicklick JK.
      Targeted therapies for gastrointestinal stromal tumor (GIST) are modestly effective, but GIST cannot be cured with single agent tyrosine kinase inhibitors. In this study, we sought to identify new therapeutic targets in GIST by investigating the tumor microenvironment. Here, we identified a paracrine signaling network by which cancer-associated fibroblasts (CAFs) drive GIST growth and metastasis. Specifically, CAFs isolated from human tumors were found to produce high levels of platelet-derived growth factor C (PDGFC), which activated PDGFC-PDGFRA signal transduction in GIST cells that regulated the expression of SLUG, an epithelial-mesenchymal transition (EMT) transcription factor and downstream target of PDGFRA signaling. Together, this paracrine induce signal transduction cascade promoted tumor growth and metastasis in vivo. Moreover, in metastatic GIST patients, SLUG expression positively correlated with tumor size and mitotic index. Given that CAF paracrine signaling modulated GIST biology, we directly targeted CAFs with a dual PI3K/mTOR inhibitor, which synergized with imatinib to increase tumor cell killing and in vivo disease response. Taken together, we identified a previously unappreciated cellular target for GIST therapy in order to improve disease control and cure rates.
    DOI:  https://doi.org/10.1038/s41388-021-01685-w
  16. Sci Adv. 2021 Feb;pii: eabd6927. [Epub ahead of print]7(8):
    Dong L, Mao Y, Zhou A, Liu XM, Zhou J, Wan J, Qian SB.
      Translation is a crucial process in cancer development and progression. Many oncogenic signaling pathways target the translation initiation stage to satisfy the increased anabolic demands of cancer cells. Using quantitative profiling of initiating ribosomes, we found that ribosomal pausing at the start codon serves as a "brake" to restrain the translational output. In response to oncogenic RAS signaling, the initiation pausing relaxes and contributes to the increased translational flux. Intriguingly, messenger RNA (mRNA) m6A modification in the vicinity of start codons influences the behavior of initiating ribosomes. Under oncogenic RAS signaling, the reduced mRNA methylation leads to relaxed initiation pausing, thereby promoting malignant transformation and tumor growth. Restored initiation pausing by inhibiting m6A demethylases suppresses RAS-mediated oncogenic translation and subsequent tumorigenesis. Our findings unveil a paradigm of translational control that is co-opted by RAS mutant cancer cells to drive malignant phenotypes.
    DOI:  https://doi.org/10.1126/sciadv.abd6927
  17. Cancer Res. 2021 Feb 18. pii: canres.2976.2020. [Epub ahead of print]
    Assi M, Achouri Y, Loriot A, Dauguet N, Dahou H, Baldan J, Libert M, Fain JS, Guerra C, Bouwens L, Barbacid M, Lemaigre FP, Jacquemin P.
      Pancreatic acinar cells are a cell type of origin for pancreatic cancer that become progressively less sensitive to tumorigenesis induced by oncogenic Kras mutations after birth. This sensitivity is increased when Kras mutations are combined with pancreatitis. Molecular mechanisms underlying these observations are still largely unknown. To identify these mechanisms, we generated the first CRISPR-edited mouse models that enable detection of wild-type and mutant KRAS proteins in vivo. Analysis of these mouse models revealed that more than 75% of adult acinar cells are devoid of detectable KRAS protein. In the 25% of acinar cells expressing KRAS protein, transcriptomic analysis highlighted a slight upregulation of the RAS and MAPK pathways. However, at the protein level, only marginal pancreatic expression of essential KRAS effectors, including C-RAF, was observed. The expression of KRAS and its effectors gradually decreased after birth. The low sensitivity of adult acinar cells to Kras mutations resulted from low expression of KRAS and its effectors and the subsequent lack of activation of RAS/MAPK pathways. Pancreatitis triggered expression of KRAS and its effectors as well as subsequent activation of downstream signaling; this induction required the activity of EGFR. Finally, expression of C-RAF in adult pancreas was required for pancreatic tumorigenesis. In conclusion, our study reveals that control of the expression of KRAS and its effectors regulates the sensitivity of acinar cells to transformation by oncogenic Kras mutations.
    DOI:  https://doi.org/10.1158/0008-5472.CAN-20-2976
  18. Nature. 2021 Feb 15.
    Watson MJ, Vignali PDA, Mullett SJ, Overacre-Delgoffe AE, Peralta RM, Grebinoski S, Menk AV, Rittenhouse NL, DePeaux K, Whetstone RD, Vignali DAA, Hand TW, Poholek AC, Morrison BM, Rothstein JD, Wendell SG, Delgoffe GM.
      Regulatory T (Treg) cells, although vital for immune homeostasis, also represent a major barrier to anti-cancer immunity, as the tumour microenvironment (TME) promotes the recruitment, differentiation and activity of these cells1,2. Tumour cells show deregulated metabolism, leading to a metabolite-depleted, hypoxic and acidic TME3, which places infiltrating effector T cells in competition with the tumour for metabolites and impairs their function4-6. At the same time, Treg cells maintain a strong suppression of effector T cells within the TME7,8. As previous studies suggested that Treg cells possess a distinct metabolic profile from effector T cells9-11, we hypothesized that the altered metabolic landscape of the TME and increased activity of intratumoral Treg cells are linked. Here we show that Treg cells display broad heterogeneity in their metabolism of glucose within normal and transformed tissues, and can engage an alternative metabolic pathway to maintain suppressive function and proliferation. Glucose uptake correlates with poorer suppressive function and long-term instability, and high-glucose conditions impair the function and stability of Treg cells in vitro. Treg cells instead upregulate pathways involved in the metabolism of the glycolytic by-product lactic acid. Treg cells withstand high-lactate conditions, and treatment with lactate prevents the destabilizing effects of high-glucose conditions, generating intermediates necessary for proliferation. Deletion of MCT1-a lactate transporter-in Treg cells reveals that lactate uptake is dispensable for the function of peripheral Treg cells but required intratumorally, resulting in slowed tumour growth and an increased response to immunotherapy. Thus, Treg cells are metabolically flexible: they can use 'alternative' metabolites in the TME to maintain their suppressive identity. Further, our results suggest that tumours avoid destruction by not only depriving effector T cells of nutrients, but also metabolically supporting regulatory populations.
    DOI:  https://doi.org/10.1038/s41586-020-03045-2
  19. Cancer Discov. 2021 Feb 19. pii: candisc.1325.2020. [Epub ahead of print]
    Cai H, Chew SK, Li C, Tsai MK, Andrejka L, Murray CW, Hughes NW, Shuldiner EG, Ashkin EL, Tang R, Hung KL, Chen LC, Lee SYC, Yousefi M, Lin WY, Kunder CA, Cong L, McFarland CD, Petrov DA, Swanton C, Winslow MM.
      Cancer genotyping has identified a large number of putative tumor suppressor genes. Carcinogenesis is a multi-step process, however the importance and specific roles of many of these genes during tumor initiation, growth and progression remain unknown. Here we use a multiplexed mouse model of oncogenic KRAS-driven lung cancer to quantify the impact of forty-eight known and putative tumor suppressor genes on diverse aspects of carcinogenesis at an unprecedented scale and resolution. We uncover many previously understudied functional tumor suppressors that constrain cancer in vivo. Inactivation of some genes substantially increased growth, while the inactivation of others increases tumor initiation and/or the emergence of exceptionally large tumors. These functional in vivo analyses revealed an unexpectedly complex landscape of tumor suppression that has implications for understanding cancer evolution, interpreting clinical cancer genome sequencing data, and directing approaches to limit tumor initiation and progression.
    DOI:  https://doi.org/10.1158/2159-8290.CD-20-1325
  20. Cell Metab. 2021 Feb 09. pii: S1550-4131(21)00013-9. [Epub ahead of print]
    Latorre-Muro P, O'Malley KE, Bennett CF, Perry EA, Balsa E, Tavares CDJ, Jedrychowski M, Gygi SP, Puigserver P.
      The architecture of cristae provides a spatial mitochondrial organization that contains functional respiratory complexes. Several protein components including OPA1 and MICOS complex subunits organize cristae structure, but upstream regulatory mechanisms are largely unknown. Here, in vivo and in vitro reconstitution experiments show that the endoplasmic reticulum (ER) kinase PERK promotes cristae formation by increasing TOM70-assisted mitochondrial import of MIC19, a critical subunit of the MICOS complex. Cold stress or β-adrenergic stimulation activates PERK that phosphorylates O-linked N-acetylglucosamine transferase (OGT). Phosphorylated OGT glycosylates TOM70 on Ser94, enhancing MIC19 protein import into mitochondria and promoting cristae formation and respiration. In addition, PERK-activated OGT O-GlcNAcylates and attenuates CK2α activity, which mediates TOM70 Ser94 phosphorylation and decreases MIC19 mitochondrial protein import. We have identified a cold-stress inter-organelle PERK-OGT-TOM70 axis that increases cell respiration through mitochondrial protein import and subsequent cristae formation. These studies have significant implications in cellular bioenergetics and adaptations to stress conditions.
    Keywords:  MIC19; PERK-OGT axis; TOM70; brown adipocytes; cold stress; cristae biogenesis; mitochondrial protein import; respiration
    DOI:  https://doi.org/10.1016/j.cmet.2021.01.013
  21. EMBO Rep. 2021 Feb 15. e51635
    Yousefi R, Fornasiero EF, Cyganek L, Montoya J, Jakobs S, Rizzoli SO, Rehling P, Pacheu-Grau D.
      Mitochondria possess a small genome that codes for core subunits of the oxidative phosphorylation system and whose expression is essential for energy production. Information on the regulation and spatial organization of mitochondrial gene expression in the cellular context has been difficult to obtain. Here we devise an imaging approach to analyze mitochondrial translation within the context of single cells, by following the incorporation of clickable non-canonical amino acids. We apply this method to multiple cell types, including specialized cells such as cardiomyocytes and neurons, and monitor with spatial resolution mitochondrial translation in axons and dendrites. We also show that translation imaging allows to monitor mitochondrial protein expression in patient fibroblasts. Approaching mitochondrial translation with click chemistry opens new avenues to understand how mitochondrial biogenesis is integrated into the cellular context and can be used to assess mitochondrial gene expression in mitochondrial diseases.
    Keywords:  gene expression; hippocampal neuron; mitochondria; synapse; translation
    DOI:  https://doi.org/10.15252/embr.202051635
  22. Cancer Discov. 2021 Jan 27. pii: candisc.1227.2020. [Epub ahead of print]
    Egan G, Khan DH, Lee JB, Mirali S, Zhang L, Schimmer AD.
      Mitochondria are involved in many biological processes including cellular homeostasis, energy generation and apoptosis. Moreover, mitochondrial and metabolic pathways are interconnected with gene expression to regulate cellular functions such as cell growth, survival, differentiation and immune recognition. Metabolites and mitochondrial enzymes regulate chromatin modifying-enzymes, chromatin remodeling, and transcription regulators. Deregulation of mitochondrial pathways and metabolism leads to alterations in gene expression that promotes cancer development, progression and evasion of the immune system. This review highlights how mitochondrial and metabolic pathways function as a central mediator to control gene expression, specifically on stem cell functions, differentiation and immune response in leukemia.
    DOI:  https://doi.org/10.1158/2159-8290.CD-20-1227
  23. Sci Transl Med. 2021 Feb 17. pii: eaav5928. [Epub ahead of print]13(581):
    Melki I, Allaeys I, Tessandier N, Lévesque T, Cloutier N, Laroche A, Vernoux N, Becker Y, Benk-Fortin H, Zufferey A, Rollet-Labelle E, Pouliot M, Poirier G, Patey N, Belleannee C, Soulet D, McKenzie SE, Brisson A, Tremblay ME, Lood C, Fortin PR, Boilard E.
      The accumulation of DNA and nuclear components in blood and their recognition by autoantibodies play a central role in the pathophysiology of systemic lupus erythematosus (SLE). Despite the efforts, the sources of circulating autoantigens in SLE are still unclear. Here, we show that in SLE, platelets release mitochondrial DNA, the majority of which is associated with the extracellular mitochondrial organelle. Mitochondrial release in patients with SLE correlates with platelet degranulation. This process requires the stimulation of platelet FcγRIIA, a receptor for immune complexes. Because mice lack FcγRIIA and murine platelets are completely devoid of receptor capable of binding IgG-containing immune complexes, we used transgenic mice expressing FcγRIIA for our in vivo investigations. FcγRIIA expression in lupus-prone mice led to the recruitment of platelets in kidneys and to the release of mitochondria in vivo. Using a reporter mouse with red fluorescent protein targeted to the mitochondrion, we confirmed platelets as a source of extracellular mitochondria driven by FcγRIIA and its cosignaling by the fibrinogen receptor α2bβ3 in vivo. These findings suggest that platelets might be a key source of mitochondrial antigens in SLE and might be a therapeutic target for treating SLE.
    DOI:  https://doi.org/10.1126/scitranslmed.aav5928
  24. Cell Metab. 2021 Feb 10. pii: S1550-4131(21)00056-5. [Epub ahead of print]
    Maguire OA, Ackerman SE, Szwed SK, Maganti AV, Marchildon F, Huang X, Kramer DJ, Rosas-Villegas A, Gelfer RG, Turner LE, Ceballos V, Hejazi A, Samborska B, Rahbani JF, Dykstra CB, Annis MG, Luo JD, Carroll TS, Jiang CS, Dannenberg AJ, Siegel PM, Tersey SA, Mirmira RG, Kazak L, Cohen P.
      Obesity is a major risk factor for adverse outcomes in breast cancer; however, the underlying molecular mechanisms have not been elucidated. To investigate the role of crosstalk between mammary adipocytes and neoplastic cells in the tumor microenvironment (TME), we performed transcriptomic analysis of cancer cells and adjacent adipose tissue in a murine model of obesity-accelerated breast cancer and identified glycine amidinotransferase (Gatm) in adipocytes and Acsbg1 in cancer cells as required for obesity-driven tumor progression. Gatm is the rate-limiting enzyme in creatine biosynthesis, and deletion in adipocytes attenuated obesity-driven tumor growth. Similarly, genetic inhibition of creatine import into cancer cells reduced tumor growth in obesity. In parallel, breast cancer cells in obese animals upregulated the fatty acyl-CoA synthetase Acsbg1 to promote creatine-dependent tumor progression. These findings reveal key nodes in the crosstalk between adipocytes and cancer cells in the TME necessary for obesity-driven breast cancer progression.
    Keywords:  Acsbg1; Gatm; breast cancer; creatine; hypoxia; obesity
    DOI:  https://doi.org/10.1016/j.cmet.2021.01.018
  25. Clin Cancer Res. 2021 Feb 16. pii: clincanres.4772.2020. [Epub ahead of print]
    Jones GD, Caso R, Tan KS, Mastrogiacomo B, Sanchez-Vega F, Liu Y, Connolly JG, Murciano-Goroff YR, Bott M, Adusumilli PS, Molena D, Rocco G, Rusch VW, Sihag S, Misale S, Yaeger R, Drilon A, Arbour KC, Riely GJ, Rosen N, Lito P, Zhang H, Lyden D, Rudin CM, Jones DR, Li BT, Isbell JM.
      PURPOSE: KRASG12C is the most common KRAS mutation in primary lung adenocarcinoma (LUAD). Phase I clinical trials have demonstrated encouraging clinical activity of KRASG12C inhibitors in the metastatic setting. We investigated disease-free survival (DFS) and tumor genomic features in patients with surgically resected KRASG12C-mutant LUAD.EXPERIMENTAL DESIGN: Patients who underwent resection of stage I-III LUAD and next-generation sequencing (NGS) were evaluated. Exclusion criteria were receipt of induction therapy, incomplete resection, and low-quality NGS. Mutations were classified as KRAS wild-type (KRASwt), G12C (KRASG12C), or non-G12C (KRASother). DFS was compared between groups using the log-rank test; factors associated with DFS were assessed using Cox regression. Mutual exclusivity and co-occurrence, tumor clonality, and mutational signatures were assessed.
    RESULTS: In total, 604 patients were included: 374 KRASwt (62%), 95 KRASG12C (16%), and 135 KRASother (22%). Three-year DFS was not different between KRAS-mutant and KRASwt tumors. However, 3-year DFS was worse in patients with KRASG12C than KRASother tumors (log-rank p=0.029). KRASG12C tumors had more lymphovascular invasion (51% vs. 37%; p=0.032) and higher tumor mutation burden (median [interquartile range], 7.0 [5.3-10.8] vs. 6.1 [3.5-9.7]; p=0.021), compared with KRASother tumors. KRASG12C mutation was independently associated with worse DFS on multivariable analysis. Our DFS findings were externally validated in an independent The Cancer Genome Atlas cohort.
    CONCLUSIONS: KRASG12C mutations are associated with worse DFS after complete resection of stage I-III LUAD. These tumors harbor more-aggressive clinicopathologic and genomic features than other KRAS-mutant tumors. We identify a high-risk group for whom KRASG12C inhibitors may be investigated to improve survival.
    DOI:  https://doi.org/10.1158/1078-0432.CCR-20-4772
  26. J Cell Sci. 2021 Feb 18. pii: jcs.250225. [Epub ahead of print]
    Asadullah , Kumar S, Saxena N, Sarkar M, Barai A, Sen S.
      Phenotypic heterogeneity is increasingly appreciated to confer several advantages to cancer progression and drug resistance. Here we probe the collective importance of heterogeneity in cell size and deformability in breast cancer invasion. A computational model of invasion of a heterogeneous cell aggregate predicts that combined heterogeneity in cell size and deformability enhances invasiveness of the whole population, with maximum invasiveness at intermediate cell-cell adhesion. We then show that small cells of varying deformability-a sub-population predicted to be enriched at the invasive front-exhibit considerable overlap with biophysical properties of cancer stem cells (CSCs). In MDA-MB-231 cells, these include CD44 hi CD24- mesenchymal CSCs which are small and soft, and CD44 hi CD24+ hybrid CSCs which exhibit a wide range of size and deformability. We validate our predictions by tracking pattern of cell invasion from spheroids implanted in 3D collagen gels, wherein we show temporal enrichment of CD44 hi cells at the invasive front. Collectively, our results illustrate the advantages imparted by biophysical heterogeneity in enhancing cancer invasiveness.
    Keywords:  Biophysical heterogeneity; Breast cancer invasion; Cancer stem cells
    DOI:  https://doi.org/10.1242/jcs.250225
  27. Annu Rev Anim Biosci. 2021 Feb 16. 9 203-224
    St John JC.
      Our understanding of the interactions between the nuclear and mitochondrial genomes is becoming increasingly important as they are extensively involved in establishing early development and developmental progression. Evidence from various biological systems indicates the interdependency between the genomes, which requires a high degree of compatibility and synchrony to ensure effective cellular function throughout development and in the resultant offspring. During development, waves of DNA demethylation, de novo methylation, and maintenance methylation act on the nuclear genome and typify oogenesis and pre- and postimplantation development. At the same time, significant changes in mitochondrial DNA copy number influence the metabolic status of the developing organism in a typically cell-type-specific manner. Collectively, at any given stage in development, these actions establish genomic balance that ensures each developmental milestone is met and that the organism's program for life is established.
    Keywords:  DNA methylation; copy number; embryo; mitochondrial DNA; mtDNA; oocyte; tumor
    DOI:  https://doi.org/10.1146/annurev-animal-080520-083353
  28. Clin Cancer Res. 2021 Feb 16. pii: clincanres.3513.2020. [Epub ahead of print]
    Son M, Kim H, Han D, Kim Y, Huh I, Han Y, Hong SM, Kwon W, Kim H, Jang JY, Kim Y.
      PURPOSE: Pancreatic ductal adenocarcinoma (PDAC) subtypes have been identified using various methodologies. However, it is a challenge to develop classification system applicable to routine clinical evaluation. We aimed to identify risk subgroups based on molecular features and develop a classification model that was more suited for clinical applications.EXPERIMENTAL DESIGN: We collected whole dissected specimens from 225 patients who underwent surgery at Seoul National University Hospital, between October 2009 and February 2018, in Korea. Target proteins with potential relevance to tumor progression or prognosis were quantified with robust quality controls. We used hierarchical clustering analysis to identify risk subgroups. A random forest classification model was developed to predict the identified risk subgroups, and the model was validated using transcriptomic datasets from external cohorts (N = 700), with survival analysis.
    RESULTS: We identified 24 protein features that could classify the four risk subgroups associated with patient outcomes: Stable; Exocrine-like; Activated; and Extracellular matrix (ECM)-Remodeling. The "Stable" risk subgroup was characterized by proteins that were associated with differentiation and tumor suppressors. "Exocrine-like" tumors highly expressed pancreatic enzymes. Two high-risk subgroups, "Activated" and "ECM-Remodeling," were enriched in such terms as cell cycle, angiogenesis, immuno-competence, tumor invasion-metastasis, and metabolic reprogramming. The classification model that included these features made prognoses with relative accuracy and precision in multiple cohorts.
    CONCLUSIONS: We proposed PDAC risk subgroups and developed a classification model that may potentially be useful for routine clinical implementations, at the individual level. This clinical system may improve the accuracy of risk prediction and treatment guidelines.
    DOI:  https://doi.org/10.1158/1078-0432.CCR-20-3513
  29. Biochem J. 2021 Feb 12. 478(3): 597-617
    Perrotta RM, Bach CA, Salatino M, Rabinovich GA.
      A sequence of interconnected events known as the metastatic cascade promotes tumor progression by regulating cellular and molecular interactions between tumor, stromal, endothelial, and immune cells both locally and systemically. Recently, a new concept has emerged to better describe this process by defining four attributes that metastatic cells should undergo. Every individual hallmark represents a unique trait of a metastatic cell that impacts directly in the outcome of the metastasis process. These critical features, known as the hallmarks of metastasis, include motility and invasion, modulation of the microenvironment, cell plasticity and colonization. They are hierarchically regulated at different levels by several factors, including galectins, a highly conserved family of β-galactoside-binding proteins abundantly expressed in tumor microenvironments and sites of metastasis. In this review, we discuss the role of galectins in modulating each hallmark of metastasis, highlighting novel therapeutic opportunities for treating the metastatic disease.
    Keywords:  cancer; galectins; lectins; metastasis; tumor immunity
    DOI:  https://doi.org/10.1042/BCJ20200167
  30. EMBO J. 2021 Feb 19. e106524
    Ercan B, Naito T, Koh DHZ, Dharmawan D, Saheki Y.
      Cholesterol is essential for cell physiology. Transport of the "accessible" pool of cholesterol from the plasma membrane (PM) to the endoplasmic reticulum (ER) by ER-localized GRAMD1 proteins (GRAMD1a/1b/1c) contributes to cholesterol homeostasis. However, how cells detect accessible cholesterol within the PM remains unclear. We show that the GRAM domain of GRAMD1b, a coincidence detector for anionic lipids, including phosphatidylserine (PS), and cholesterol, possesses distinct but synergistic sites for sensing accessible cholesterol and anionic lipids. We find that a mutation within the GRAM domain of GRAMD1b that is associated with intellectual disability in humans specifically impairs cholesterol sensing. In addition, we identified another point mutation within this domain that enhances cholesterol sensitivity without altering its PS sensitivity. Cell-free reconstitution and cell-based assays revealed that the ability of the GRAM domain to sense accessible cholesterol regulates membrane tethering and determines the rate of cholesterol transport by GRAMD1b. Thus, cells detect the codistribution of accessible cholesterol and anionic lipids in the PM and fine-tune the non-vesicular transport of PM cholesterol to the ER via GRAMD1s.
    Keywords:  GRAM domain; cholesterol; lipid sensor; membrane contact sites; plasma membrane
    DOI:  https://doi.org/10.15252/embj.2020106524
  31. Nat Commun. 2021 Feb 19. 12(1): 1176
    Tran TH, Chan AH, Young LC, Bindu L, Neale C, Messing S, Dharmaiah S, Taylor T, Denson JP, Esposito D, Nissley DV, Stephen AG, McCormick F, Simanshu DK.
      The first step of RAF activation involves binding to active RAS, resulting in the recruitment of RAF to the plasma membrane. To understand the molecular details of RAS-RAF interaction, we present crystal structures of wild-type and oncogenic mutants of KRAS complexed with the RAS-binding domain (RBD) and the membrane-interacting cysteine-rich domain (CRD) from the N-terminal regulatory region of RAF1. Our structures reveal that RBD and CRD interact with each other to form one structural entity in which both RBD and CRD interact extensively with KRAS. Mutations at the KRAS-CRD interface result in a significant reduction in RAF1 activation despite only a modest decrease in binding affinity. Combining our structures and published data, we provide a model of RAS-RAF complexation at the membrane, and molecular insights into RAS-RAF interaction during the process of RAS-mediated RAF activation.
    DOI:  https://doi.org/10.1038/s41467-021-21422-x
  32. Cell Rep. 2021 Jan 26. pii: S2211-1247(20)31659-4. [Epub ahead of print]34(4): 108670
    Jiang Q, Isquith J, Ladel L, Mark A, Holm F, Mason C, He Y, Mondala P, Oliver I, Pham J, Ma W, Reynoso E, Ali S, Morris IJ, Diep R, Nasamran C, Xu G, Sasik R, Rosenthal SB, Birmingham A, Coso S, Pineda G, Crews L, Donohoe ME, Venter JC, Whisenant T, Mesa RA, Alexandrov LB, Fisch KM, Jamieson C.
      Inflammation-dependent base deaminases promote therapeutic resistance in many malignancies. However, their roles in human pre-leukemia stem cell (pre-LSC) evolution to acute myeloid leukemia stem cells (LSCs) had not been elucidated. Comparative whole-genome and whole-transcriptome sequencing analyses of FACS-purified pre-LSCs from myeloproliferative neoplasm (MPN) patients reveal APOBEC3C upregulation, an increased C-to-T mutational burden, and hematopoietic stem and progenitor cell (HSPC) proliferation during progression, which can be recapitulated by lentiviral APOBEC3C overexpression. In pre-LSCs, inflammatory splice isoform overexpression coincides with APOBEC3C upregulation and ADAR1p150-induced A-to-I RNA hyper-editing. Pre-LSC evolution to LSCs is marked by STAT3 editing, STAT3β isoform switching, elevated phospho-STAT3, and increased ADAR1p150 expression, which can be prevented by JAK2/STAT3 inhibition with ruxolitinib or fedratinib or lentiviral ADAR1 shRNA knockdown. Conversely, lentiviral ADAR1p150 expression enhances pre-LSC replating and STAT3 splice isoform switching. Thus, pre-LSC evolution to LSCs is fueled by primate-specific APOBEC3C-induced pre-LSC proliferation and ADAR1-mediated splicing deregulation.
    Keywords:  Enter keywords here
    DOI:  https://doi.org/10.1016/j.celrep.2020.108670
  33. Genes Dev. 2021 Feb 18.
    Innes AJ, Sun B, Wagner V, Brookes S, McHugh D, Pombo J, Porreca RM, Dharmalingam G, Vernia S, Zuber J, Vannier JB, García-Escudero R, Gil J.
      Senescence is a key barrier to neoplastic transformation. To identify senescence regulators relevant to cancer, we screened a genome-wide shRNA library. Here, we describe exportin 7 (XPO7) as a novel regulator of senescence and validate its function in telomere-induced, replicative, and oncogene-induced senescence (OIS). XPO7 is a bidirectional transporter that regulates the nuclear-cytoplasmic shuttling of a broad range of substrates. Depletion of XPO7 results in reduced levels of TCF3 and an impaired induction of the cyclin-dependent kinase inhibitor p21CIP1 during OIS. Deletion of XPO7 correlates with poorer overall survival in several cancer types. Moreover, depletion of XPO7 alleviated OIS and increased tumor formation in a mouse model of liver cancer. Our results suggest that XPO7 is a novel tumor suppressor that regulates p21CIP1 expression to control senescence and tumorigenesis.
    Keywords:  TCF3; XPO7; functional screen; p21CIP1; senescence; tumor suppressor
    DOI:  https://doi.org/10.1101/gad.343269.120
  34. Cancer Discov. 2021 Jan 27. pii: candisc.1211.2020. [Epub ahead of print]
    Dey P, Kimmelman AC, DePinho RA.
      Metabolic reprogramming enables cancer cell growth, proliferation, and survival. This reprogramming is driven by the combined actions of oncogenic alterations in cancer cells and host cell factors acting on cancer cells in the tumor microenvironment. Cancer cell intrinsic mechanisms activate signal transduction components that either directly enhance metabolic enzyme activity or upregulate transcription factors that in turn increase expression of metabolic regulators. Extrinsic signaling mechanisms involve host-derived factors that further promote and amplify metabolic reprogramming in cancer cells. This review describes intrinsic and extrinsic mechanisms driving cancer metabolism in the tumor microenvironment and how such mechanisms may be targeted therapeutically.
    DOI:  https://doi.org/10.1158/2159-8290.CD-20-1211
  35. Oncogene. 2021 Feb 18.
    Solan JL, Hingorani SR, Lampe PD.
      Pancreatic ductal adenocarcinoma (PDA) is aggressive, highly metastatic and characterized by a robust desmoplasia. Connexin proteins that form gap junctions have been implicated in tumor suppression for over 30 years. Cx43, the most widely expressed connexin, regulates cell behaviors, including migration and proliferation. Thus, we hypothesized that Cx43 could regulate PDA progression. Phosphorylation of Cx43 by Casein Kinase 1 (CK1) regulates gap junction assembly. We interbred the well-established KrasLSL-G12D/+;p48Cre/+ (KC) mouse model of PDA with homozygous "knock-in" mutant Cx43 mice bearing amino acid substitution at CK1 sites (Cx43CK1A) and found profound and surprising effects on cancer progression. Crossing the Cx43CK1A mouse onto the KC background (termed KC;CxCK1A) led to significant extension of lifespan, from a median of 370 to 486 days (p = 0.03) and a decreased incidence of metastasis (p = 0.045). However, when we examined early stages of disease, we found more rapid onset of tissue remodeling in the KC;CxCK1A mouse followed by divergence to a cystic phenotype. During tumorigenesis, gap junctions are increasingly present in stromal cells of the KC mice but are absent from the KC;Cx43CK1A mice. Tail vein metastasis assays with cells derived from KC or KC;CxCK1A tumors showed that KC;CxCK1A cells could efficiently colonize the lung and downregulate Cx43 expression, arguing that inhibition of metastasis was not occurring at the distal site. Instead, stromal gap junctions, their associated signaling events or other unknown Cx43-dependent events facilitate metastatic capacity in the primary tumor.
    DOI:  https://doi.org/10.1038/s41388-021-01668-x
  36. Cancer Discov. 2021 Feb 15.
      Pancreatic injury plus oncogenic Kras mutation produced cancer-associated chromatin states in vivo.
    DOI:  https://doi.org/10.1158/2159-8290.CD-RW2021-019
  37. J Exp Med. 2021 Jan 04. pii: e20201606. [Epub ahead of print]218(1):
    Bian X, Liu R, Meng Y, Xing D, Xu D, Lu Z.
      Dysregulation in lipid metabolism is among the most prominent metabolic alterations in cancer. Cancer cells harness lipid metabolism to obtain energy, components for biological membranes, and signaling molecules needed for proliferation, survival, invasion, metastasis, and response to the tumor microenvironment impact and cancer therapy. Here, we summarize and discuss current knowledge about the advances made in understanding the regulation of lipid metabolism in cancer cells and introduce different approaches that have been clinically used to disrupt lipid metabolism in cancer therapy.
    DOI:  https://doi.org/10.1084/jem.20201606
  38. Nat Rev Mol Cell Biol. 2021 Feb 16.
    Kummer E, Ban N.
      Mitochondria are cellular organelles responsible for generation of chemical energy in the process called oxidative phosphorylation. They originate from a bacterial ancestor and maintain their own genome, which is expressed by designated, mitochondrial transcription and translation machineries that differ from those operating for nuclear gene expression. In particular, the mitochondrial protein synthesis machinery is structurally and functionally very different from that governing eukaryotic, cytosolic translation. Despite harbouring their own genetic information, mitochondria are far from being independent of the rest of the cell and, conversely, cellular fitness is closely linked to mitochondrial function. Mitochondria depend heavily on the import of nuclear-encoded proteins for gene expression and function, and hence engage in extensive inter-compartmental crosstalk to regulate their proteome. This connectivity allows mitochondria to adapt to changes in cellular conditions and also mediates responses to stress and mitochondrial dysfunction. With a focus on mammals and yeast, we review fundamental insights that have been made into the biogenesis, architecture and mechanisms of the mitochondrial translation apparatus in the past years owing to the emergence of numerous near-atomic structures and a considerable amount of biochemical work. Moreover, we discuss how cellular mitochondrial protein expression is regulated, including aspects of mRNA and tRNA maturation and stability, roles of auxiliary factors, such as translation regulators, that adapt mitochondrial translation rates, and the importance of inter-compartmental crosstalk with nuclear gene expression and cytosolic translation and how it enables integration of mitochondrial translation into the cellular context.
    DOI:  https://doi.org/10.1038/s41580-021-00332-2
  39. Nat Commun. 2021 02 15. 12(1): 1041
    Klein AB, Nicolaisen TS, Ørtenblad N, Gejl KD, Jensen R, Fritzen AM, Larsen EL, Karstoft K, Poulsen HE, Morville T, Sahl RE, Helge JW, Lund J, Falk S, Lyngbæk M, Ellingsgaard H, Pedersen BK, Lu W, Finan B, Jørgensen SB, Seeley RJ, Kleinert M, Kiens B, Richter EA, Clemmensen C.
      Growing evidence supports that pharmacological application of growth differentiation factor 15 (GDF15) suppresses appetite but also promotes sickness-like behaviors in rodents via GDNF family receptor α-like (GFRAL)-dependent mechanisms. Conversely, the endogenous regulation of GDF15 and its physiological effects on energy homeostasis and behavior remain elusive. Here we show, in four independent human studies that prolonged endurance exercise increases circulating GDF15 to levels otherwise only observed in pathophysiological conditions. This exercise-induced increase can be recapitulated in mice and is accompanied by increased Gdf15 expression in the liver, skeletal muscle, and heart muscle. However, whereas pharmacological GDF15 inhibits appetite and suppresses voluntary running activity via GFRAL, the physiological induction of GDF15 by exercise does not. In summary, exercise-induced circulating GDF15 correlates with the duration of endurance exercise. Yet, higher GDF15 levels after exercise are not sufficient to evoke canonical pharmacological GDF15 effects on appetite or responsible for diminishing exercise motivation.
    DOI:  https://doi.org/10.1038/s41467-021-21309-x
  40. J R Soc Interface. 2021 Feb;18(175): 20200823
    Grekas G, Proestaki M, Rosakis P, Notbohm J, Makridakis C, Ravichandran G.
      Through mechanical forces, biological cells remodel the surrounding collagen network, generating striking deformation patterns. Tethers-tracts of high densification and fibre alignment-form between cells, thinner bands emanate from cell clusters. While tethers facilitate cell migration and communication, how they form is unclear. Combining modelling, simulation and experiment, we show that tether formation is a densification phase transition of the extracellular matrix, caused by buckling instability of network fibres under cell-induced compression, featuring unexpected similarities with martensitic microstructures. Multiscale averaging yields a two-phase, bistable continuum energy landscape for fibrous collagen, with a densified/aligned second phase. Simulations predict strain discontinuities between the undensified and densified phase, which localizes within tethers as experimentally observed. In our experiments, active particles induce similar localized patterns as cells. This shows how cells exploit an instability to mechanically remodel the extracellular matrix simply by contracting, thereby facilitating mechanosensing, invasion and metastasis.
    Keywords:  ECM remodelling; densification patterns; fibre alignment; fibre buckling; phase transition; tumour biomarkers
    DOI:  https://doi.org/10.1098/rsif.2020.0823
  41. Med Hypotheses. 2021 Jan 27. pii: S0306-9877(21)00036-0. [Epub ahead of print]149 110518
    McCarty MF, Assanga SI, Lujan LL.
      During the last half of the twentieth century, age-adjusted mortality from pancreatic cancer in Japan rose about nine-fold in both sexes. Well-characterized risk factors such as smoking, obesity/metabolic syndrome, and heavy alcohol use appear to explain only a modest part of this rise. It is proposed that a diet relatively low in protein, and particularly low in animal protein, was a key determinant of the low risk for pancreatic cancer in mid-century Japan. It is further proposed that pancreatic acinar cells, owing to their extraordinarily high rate of protein synthesis, are at high risk for ER stress; that such stress plays a fundamental role in the induction of most pancreatic cancers; and that low-protein diets help to offset such stress by modulating activities of the kinases GCN2 and mTORC1 while increasing autocrine and systemic production of fibroblast growth factor 21. This model appears to clarify the role of various risk factors and protective factors in pancreatic cancer induction. A vegan or quasi-vegan low-protein diet may have broader potential for decreasing risk for a range of common "Western" cancers.
    Keywords:  Acinar cells; ER stress; FGF21; GCN2; Pancreatic cancer; Vegan diet
    DOI:  https://doi.org/10.1016/j.mehy.2021.110518
  42. Cell Calcium. 2021 Feb 01. pii: S0143-4160(21)00018-X. [Epub ahead of print]95 102364
    Delgado de la Herran HC, Cheng Y, Perocchi F.
      Human mitochondria are complex and highly dynamic biological systems, comprised of over a thousand parts and evolved to fully integrate into the specialized intracellular signaling networks and metabolic requirements of each cell and organ. Over the last two decades, several complementary, top-down computational and experimental approaches have been developed to identify, characterize and modulate the human mitochondrial system, demonstrating the power of integrating classical reductionist and discovery-driven analyses in order to de-orphanize hitherto unknown molecular components of mitochondrial machineries and pathways. To this goal, systematic, multiomics-based surveys of proteome composition, protein networks, and phenotype-to-pathway associations at the tissue, cell and organellar level have been largely exploited to predict the full complement of mitochondrial proteins and their functional interactions, therefore catalyzing data-driven hypotheses. Collectively, these multidisciplinary and integrative research approaches hold the potential to propel our understanding of mitochondrial biology and provide a systems-level framework to unraveling mitochondria-mediated and disease-spanning pathomechanisms.
    Keywords:  Functional associations; Integrative analyses; Mitochondrial system; Multiomics approaches
    DOI:  https://doi.org/10.1016/j.ceca.2021.102364
  43. Science. 2021 Feb 19. 371(6531): 839-846
    Sampaziotis F, Muraro D, Tysoe OC, Sawiak S, Beach TE, Godfrey EM, Upponi SS, Brevini T, Wesley BT, Garcia-Bernardo J, Mahbubani K, Canu G, Gieseck R, Berntsen NL, Mulcahy VL, Crick K, Fear C, Robinson S, Swift L, Gambardella L, Bargehr J, Ortmann D, Brown SE, Osnato A, Murphy MP, Corbett G, Gelson WTH, Mells GF, Humphreys P, Davies SE, Amin I, Gibbs P, Sinha S, Teichmann SA, Butler AJ, See TC, Melum E, Watson CJE, Saeb-Parsy K, Vallier L.
      Organoid technology holds great promise for regenerative medicine but has not yet been applied to humans. We address this challenge using cholangiocyte organoids in the context of cholangiopathies, which represent a key reason for liver transplantation. Using single-cell RNA sequencing, we show that primary human cholangiocytes display transcriptional diversity that is lost in organoid culture. However, cholangiocyte organoids remain plastic and resume their in vivo signatures when transplanted back in the biliary tree. We then utilize a model of cell engraftment in human livers undergoing ex vivo normothermic perfusion to demonstrate that this property allows extrahepatic organoids to repair human intrahepatic ducts after transplantation. Our results provide proof of principle that cholangiocyte organoids can be used to repair human biliary epithelium.
    DOI:  https://doi.org/10.1126/science.aaz6964
  44. Cancer Commun (Lond). 2021 Jan 27.
    Pan G, Liu Y, Shang L, Zhou F, Yang S.
      Epithelial-to-mesenchymal transition (EMT) is implicated in a wide array of malignant behaviors of cancers, including proliferation, invasion, and metastasis. Most notably, previou studies have indicated that both cancer stem-like properties and drug resistance were associated with EMT. Furthermore, microRNAs (miRNAs) play a pivotal role in the regulation of EMT phenotype, as a result, some miRNAs impact cancer stemness and drug resistance. Therefore, understanding the relationship between EMT-associated miRNAs and cancer stemness/drug resistance is beneficial to both basic research and clinical treatment. In this review, we preliminarily looked into the various roles that the EMT-associated miRNAs play in the stem-like nature of malignant cells. Then, we reviewed the interaction between EMT-associated miRNAs and the drug-resistant complex signaling pathways of multiple cancers including lung cancer, gastric cancer, gynecologic cancer, breast cancer, liver cancer, colorectal cancer, pancreatic cancer, esophageal cancer, and nasopharyngeal cancer. We finally discussed the relationship between EMT, cancer stemness, and drug resistance, as well as looked forward to the potential applications of miRNA therapy for malignant tumors.
    Keywords:  cancer; cancer stem cell; cancer stemness; drug resistance; epithelial-to-mesenchymal transition; microRNA
    DOI:  https://doi.org/10.1002/cac2.12138
  45. Autophagy. 2021 Feb 16.
    Robichaud S, Fairman G, Vijithakumar V, Mak E, Cook DP, Pelletier AR, Huard S, Vanderhyden BC, Figeys D, Lavallée-Adam M, Baetz K, Ouimet M.
      Macrophage autophagy is a highly anti-atherogenic process that promotes the catabolism of cytosolic lipid droplets (LDs) to maintain cellular lipid homeostasis. Selective autophagy relies on tags such as ubiquitin and a set of selectivity factors including selective autophagy receptors (SARs) to label specific cargo for degradation. Originally described in yeast cells, 'lipophagy' refers to the degradation of LDs by autophagy. Yet, how LDs are targeted for autophagy is poorly defined. Here, we employed mass spectrometry to identify lipophagy factors within the macrophage foam cell LD proteome. In addition to structural proteins (e.g., PLIN2), metabolic enzymes (e.g., ACSL) and neutral lipases (e.g., PNPLA2), we found the association of proteins related to the ubiquitination machinery (e.g., AUP1) and autophagy (e.g., HMGB, YWHA/14-3-3 proteins). The functional role of candidate lipophagy factors (a total of 91) was tested using a custom siRNA array combined with high-content cholesterol efflux assays. We observed that knocking down several of these genes, including Hmgb1, Hmgb2, Hspa5, and Scarb2, significantly reduced cholesterol efflux, and SARs SQSTM1/p62, NBR1 and OPTN localized to LDs, suggesting a role for these in lipophagy. Using yeast lipophagy assays, we established a genetic requirement for several candidate lipophagy factors in lipophagy, including HSPA5, UBE2G2 and AUP1. Our study is the first to systematically identify several LD-associated proteins of the lipophagy machinery, a finding with important biological and therapeutic implications. Targeting these to selectively enhance lipophagy to promote cholesterol efflux in foam cells may represent a novel strategy to treat atherosclerosis.
    Keywords:  Autophagy; cholesterol efflux; lipid droplet; lipolysis; lipophagy; macrophage foam cell
    DOI:  https://doi.org/10.1080/15548627.2021.1886839
  46. Physiol Rev. 2021 Feb 18.
    Szwed A, Kim E, Jacinto E.
      Cells metabolize nutrients for biosynthetic and bioenergetic needs to fuel growth and proliferation. The uptake of nutrients from the environment and their intracellular metabolism is a highly controlled process that involves crosstalk between growth signaling and metabolic pathways. Despite constant fluctuations in nutrient availability and environmental signals, normal cells restore metabolic homeostasis to maintain cellular functions and prevent disease. A central signaling molecule that integrates growth with metabolism is the mechanistic target of rapamycin (mTOR). mTOR is a protein kinase that responds to levels of nutrients and growth signals. mTOR forms two protein complexes, mTORC1, which is sensitive to rapamycin and mTORC2, which is not directly inhibited by this drug. Rapamycin has facilitated the discovery of the various functions of mTORC1 in metabolism. Genetic models that disrupt either mTORC1 or mTORC2 have expanded our knowledge on their cellular, tissue as well as systemic functions in metabolism. Nevertheless, our knowledge on the regulation and functions of mTORC2, particularly in metabolism, has lagged behind. Since mTOR is an important target for cancer, aging and other metabolism-related pathologies, understanding the distinct and overlapping regulation and functions of the two mTOR complexes is vital for the development of more effective therapeutic strategies. This review will discuss the key discoveries and recent findings on the regulation and metabolic functions of the mTOR complexes. We highlight findings from cancer models, but also discuss other examples of the mTOR-mediated metabolic reprogramming occurring in stem and immune cells, type 2 diabetes/obesity, neurodegenerative disorders and aging.
    Keywords:  cancer metabolism; mTOR; mTORC; metabolic reprogramming; metabolism
    DOI:  https://doi.org/10.1152/physrev.00026.2020
  47. Front Immunol. 2020 ;11 613815
    Schmiechen ZC, Stromnes IM.
      Pancreatic ductal adenocarcinoma (PDA) is a lethal malignancy with an overall 5-year survival rate of 10%. Disease lethality is due to late diagnosis, early metastasis and resistance to therapy, including immunotherapy. PDA creates a robust fibroinflammatory tumor microenvironment that contributes to immunotherapy resistance. While previously considered an immune privileged site, evidence demonstrates that in some cases tumor antigen-specific T cells infiltrate and preferentially accumulate in PDA and are central to tumor cell clearance and long-term remission. Nonetheless, PDA can rapidly evade an adaptive immune response using a myriad of mechanisms. Mounting evidence indicates PDA interferes with T cell differentiation into potent cytolytic effector T cells via deficiencies in naive T cell priming, inducing T cell suppression or promoting T cell exhaustion. Mechanistic research indicates that immunotherapy combinations that change the suppressive tumor microenvironment while engaging antigen-specific T cells is required for treatment of advanced disease. This review focuses on recent advances in understanding mechanisms limiting T cell function and current strategies to overcome immunotherapy resistance in PDA.
    Keywords:  PD-1; PD-L1; T cell; exhaustion; immunosuppression; immunotherapy; pancreatic cancer; pancreatic ductal adenocarcinoma
    DOI:  https://doi.org/10.3389/fimmu.2020.613815
  48. JAMA Oncol. 2021 Feb 18.
    Valero C, Lee M, Hoen D, Zehir A, Berger MF, Seshan VE, Chan TA, Morris LGT.
      Importance: In June 2020, the US Food and Drug Administration approved the anti-programmed cell death 1 drug pembrolizumab for patients with malignant solid tumors of any histologic type with high tumor mutational burden (TMB; ≥10 mutations per megabase). The predictive value of this universal cutoff for high TMB is not well understood.Objective: To examine the performance of a universal definition of high TMB in an independent cohort of patients with solid tumors treated with immune checkpoint inhibitors.
    Design, Setting, and Participants: This retrospective cohort study included 1678 patients at a single cancer referral center treated with immune checkpoint inhibitors from January 1, 2015, to December 31, 2018. Patients had 16 different cancer types and were treated with anti-programmed cell death 1 or programmed cell death ligand-1 immunotherapy. Tumors underwent next-generation sequencing.
    Exposures: At least 1 dose of immune checkpoint inhibitors.
    Main Outcomes and Measures: Best overall response to immune checkpoint inhibitor therapy. The hypothesis tested was formulated after data collection and prior to analysis.
    Results: Of 1678 patients, 924 (55%) were male, and the median age was 64 years (interquartile range, 55-71 years). Using the universal cutoff of 10 mutations per megabase, 416 tumors (25%) were categorized as having high TMB. Across cancer types, the proportion of TMB-high tumors ranged from 0% of kidney cancers to 53% of melanomas (113 of 214). Tumors categorized as TMB-high had higher response rates compared with TMB-low tumors in only 11 of 16 cancer types. In the entire cohort, response rates increased with higher cutoffs for TMB-high categorization, reaching 41% (169 of 416) for TMB more than 10 and 56% (90 of 161) for TMB more than 18, the highest TMB decile. Response rates also increased with TMB percentile within cancer type. Using cancer-specific cutoffs, 457 tumors (27%) were categorized as TMB-high. Response rates within cancer type ranged from 4% for pancreatic cancer (1 of 26) to 70% for melanoma (46 of 66). Cancer-specific cutoffs were associated with numerically higher response rates for TMB-high compared with TMB-low tumors in 14 of 16 cancer types.
    Conclusions and Relevance: The data from this cohort study validate the finding of generally higher response rates following immune checkpoint inhibitor therapy for tumors with TMB of 10 or more mutations per megabase, across multiple cancer types. However, the predictive value of a universal numerical threshold for TMB-high was limited, owing to variability across cancer types and unclear associations with survival outcomes. Further investigation will help define cancer type-specific TMB cutoffs to guide decision-making.
    DOI:  https://doi.org/10.1001/jamaoncol.2020.7684
  49. Mol Biol Cell. 2021 Feb 17. mbcE20110748
    Laborenz J, Bykov YS, Knöringer K, Räschle M, Filker S, Prescianotto-Baschong C, Spang A, Tatsuta T, Langer T, Storchová Z, Schuldiner M, Herrmann JM.
      For the biogenesis of mitochondria, hundreds of proteins need to be targeted from the cytosol into the various compartments of this organelle. The intramitochondrial targeting routes these proteins take to reach their respective location in the organelle are well understood. However, the early targeting processes, from cytosolic ribosomes to the membrane of the organelle, are still largely unknown. In this study, we present evidence that an integral membrane protein of the endoplasmic reticulum (ER), Ema19, plays a role in this process. Mutants lacking Ema19 show an increased stability of mitochondrial precursor proteins, indicating that Ema19 promotes the proteolytic degradation of non-productive precursors. The deletion of Ema19 improves the growth of respiration-deficient cells, suggesting that Ema19-mediated degradation can compete with productive protein import into mitochondria. Ema19 is the yeast representative of a conserved protein family. The human Ema19 homolog is known as sigma 2 receptor or TMEM97. Though its molecular function is not known, previous studies suggested a role of the sigma 2 receptor as a quality control factor in the ER, compatible with our observations about Ema19. More globally, our data provide an additional demonstration of the important role of the ER in mitochondrial protein targeting.
    DOI:  https://doi.org/10.1091/mbc.E20-11-0748
  50. Cell Death Differ. 2021 Feb 15.
    Samson AL, Fitzgibbon C, Patel KM, Hildebrand JM, Whitehead LW, Rimes JS, Jacobsen AV, Horne CR, Gavin XJ, Young SN, Rogers KL, Hawkins ED, Murphy JM.
      Necroptosis is a lytic, inflammatory cell death pathway that is dysregulated in many human pathologies. The pathway is executed by a core machinery comprising the RIPK1 and RIPK3 kinases, which assemble into necrosomes in the cytoplasm, and the terminal effector pseudokinase, MLKL. RIPK3-mediated phosphorylation of MLKL induces oligomerization and translocation to the plasma membrane where MLKL accumulates as hotspots and perturbs the lipid bilayer to cause death. The precise choreography of events in the pathway, where they occur within cells, and pathway differences between species, are of immense interest. However, they have been poorly characterized due to a dearth of validated antibodies for microscopy studies. Here, we describe a toolbox of antibodies for immunofluorescent detection of the core necroptosis effectors, RIPK1, RIPK3, and MLKL, and their phosphorylated forms, in human and mouse cells. By comparing reactivity with endogenous proteins in wild-type cells and knockout controls in basal and necroptosis-inducing conditions, we characterise the specificity of frequently-used commercial and recently-developed antibodies for detection of necroptosis signaling events. Importantly, our findings demonstrate that not all frequently-used antibodies are suitable for monitoring necroptosis by immunofluorescence microscopy, and methanol- is preferable to paraformaldehyde-fixation for robust detection of specific RIPK1, RIPK3, and MLKL signals.
    DOI:  https://doi.org/10.1038/s41418-021-00742-x
  51. Mol Cell. 2021 Feb 04. pii: S1097-2765(21)00049-6. [Epub ahead of print]
    Goldman DH, Livingston NM, Movsik J, Wu B, Green R.
      Translation of problematic mRNA sequences induces ribosome stalling, triggering quality-control events, including ribosome rescue and nascent polypeptide degradation. To define the timing and regulation of these processes, we developed a SunTag-based reporter to monitor translation of a problematic sequence (poly[A]) in real time on single mRNAs. Although poly(A)-containing mRNAs undergo continuous translation over the timescale of minutes to hours, ribosome load is increased by ∼3-fold compared to a control, reflecting long queues of ribosomes extending far upstream of the stall. We monitor the resolution of these queues in real time and find that ribosome rescue is very slow compared to both elongation and termination. Modulation of pause strength, collision frequency, and the collision sensor ZNF598 reveals how the dynamics of ribosome collisions and their recognition facilitate selective targeting for quality control. Our results establish that slow clearance of stalled ribosomes allows cells to distinguish between transient and deleterious stalls.
    Keywords:  SunTag; imaging; mRNA; protein synthesis; quality control; ribosome; single-molecule; translation
    DOI:  https://doi.org/10.1016/j.molcel.2021.01.029
  52. Nat Rev Cancer. 2021 Feb 15.
    Cox TR.
      The extracellular matrix is a fundamental, core component of all tissues and organs, and is essential for the existence of multicellular organisms. From the earliest stages of organism development until death, it regulates and fine-tunes every cellular process in the body. In cancer, the extracellular matrix is altered at the biochemical, biomechanical, architectural and topographical levels, and recent years have seen an exponential increase in the study and recognition of the importance of the matrix in solid tumours. Coupled with the advancement of new technologies to study various elements of the matrix and cell-matrix interactions, we are also beginning to see the deployment of matrix-centric, stromal targeting cancer therapies. This Review touches on many of the facets of matrix biology in solid cancers, including breast, pancreatic and lung cancer, with the aim of highlighting some of the emerging interactions of the matrix and influences that the matrix has on tumour onset, progression and metastatic dissemination, before summarizing the ongoing work in the field aimed at developing therapies to co-target the matrix in cancer and cancer metastasis.
    DOI:  https://doi.org/10.1038/s41568-020-00329-7
  53. Mol Cell Biochem. 2021 Feb 18.
    Mannarapu M, Dariya B, Bandapalli OR.
      Pancreatic cancer (PC) is the third lethal disease for cancer-related mortalities globally. This is mainly because of the aggressive nature and heterogeneity of the disease that is diagnosed only in their advanced stages. Thus, it is challenging for researchers and clinicians to study the molecular mechanism involved in the development of this aggressive disease. The single-cell sequencing technology enables researchers to study each and every individual cell in a single tumor. It can be used to detect genome, transcriptome, and multi-omics of single cells. The current single-cell sequencing technology is now becoming an important tool for the biological analysis of cells, to find evolutionary relationship between multiple cells and unmask the heterogeneity present in the tumor cells. Moreover, its sensitivity nature is found progressive enabling to detect rare cancer cells, circulating tumor cells, metastatic cells, and analyze the intratumor heterogeneity. Furthermore, these single-cell sequencing technologies also promoted personalized treatment strategies and next-generation sequencing to predict the disease. In this review, we have focused on the applications of single-cell sequencing technology in identifying cancer-associated cells like cancer-associated fibroblast via detecting circulating tumor cells. We also included advanced technologies involved in single-cell sequencing and their advantages. The future research indeed brings the single-cell sequencing into the clinical arena and thus could be beneficial for diagnosis and therapy of PC patients.
    Keywords:  Circulating tumor cells; Intratumor heterogeneity; Metastasis; Pancreatic cancer; Single-cell sequencing; Transcriptome
    DOI:  https://doi.org/10.1007/s11010-021-04095-4
  54. Semin Cell Dev Biol. 2021 Feb 12. pii: S1084-9521(21)00025-2. [Epub ahead of print]
    Simovic M, Ernst A.
      Chromothripsis is a unique form of genome instability characterized by tens to hundreds of DNA double-strand breaks on one or very few chromosomes, followed by error-prone repair. The derivative chromosome(s) display massive rearrangements, which lead to the loss of tumor suppressor function and to the activation of oncogenes. Chromothripsis plays a major role in cancer as well as in other conditions, such as congenital diseases. In this review, we discuss the repair processes involved in the rejoining of the chromosome fragments, the role of DNA repair and checkpoint defects as a cause for chromothripsis as well as DNA repair defects resulting from chromothripsis. Finally, we consider clinical implications and potential therapeutic vulnerabilities that could be utilized to eliminate tumor cells with chromothripsis.
    Keywords:  Chromothripsis; Complex genome rearrangements; DNA repair; Genome instability
    DOI:  https://doi.org/10.1016/j.semcdb.2021.02.001
  55. Front Oncol. 2020 ;10 617109
    Gonçalves RC, Freire PP, Coletti D, Seelaender M.
      Cachexia is a syndrome that affects the entire organism and presents a variable plethora of symptoms in patients, always associated with continuous and involuntary degradation of skeletal muscle mass and function loss. In cancer, this syndrome occurs in 50% of all patients, while prevalence increases to 80% as the disease worsens, reducing quality of life, treatment tolerance, therapeutic response, and survival. Both chronic systemic inflammation and immunosuppression, paradoxically, correspond to important features in cachexia patients. Systemic inflammation in cachexia is fueled by the interaction between tumor and peripheral tissues with significant involvement of infiltrating immune cells, both in the peripheral tissues and in the tumor itself. Autophagy, as a process of regulating cellular metabolism and homeostasis, can interfere with the metabolic profile in the tumor microenvironment. Under a scenario of balanced autophagy in the tumor microenvironment, the infiltrating immune cells control cytokine production and secretion. On the other hand, when autophagy is unbalanced or dysfunctional within the tumor microenvironment, there is an impairment in the regulation of immune cell's inflammatory phenotype. The inflammatory phenotype upregulates metabolic consumption and cytokine production, not only in the tumor microenvironment but also in other tissues and organs of the host. We propose that cachexia-related chronic inflammation can be, at least, partly associated with the failure of autophagic processes in tumor cells. Autophagy endangers tumor cell viability by producing immunogenic tumor antigens, thus eliciting the immune response necessary to counteract tumor progression, while preventing the establishment of inflammation, a hallmark of cachexia. Comprehensive understanding of this complex functional dichotomy may enhance cancer treatment response and prevent/mitigate cancer cachexia. This review summarizes the recent available literature regarding the role of autophagy within the tumor microenvironment and the consequences eliciting the development of cancer cachexia.
    Keywords:  DAMPs; autophagy; cachexia; lymphocyte infiltration; metabolism; systemic inflammations; tumor microenvironment
    DOI:  https://doi.org/10.3389/fonc.2020.617109
  56. Nature. 2021 Feb 15.
    Zappasodi R, Serganova I, Cohen IJ, Maeda M, Shindo M, Senbabaoglu Y, Watson MJ, Leftin A, Maniyar R, Verma S, Lubin M, Ko M, Mane MM, Zhong H, Liu C, Ghosh A, Abu-Akeel M, Ackerstaff E, Koutcher JA, Ho PC, Delgoffe GM, Blasberg R, Wolchok JD, Merghoub T.
      Limiting the metabolic competition in the tumor microenvironment (TME) may increase the effectiveness of immunotherapy. Because of its critical role in glucose metabolism of activated T cells, CD28 signaling has been proposed as a T-cell metabolic biosensor1. Conversely, CTLA-4 engagement has been shown to down-regulate T-cell glycolysis1. Here, we investigated the impact of CTLA-4 blockade on the metabolic fitness of intra-tumor T cells in relationship to the tumor glycolytic capacity. We found that CTLA-4 blockade promotes immune cell infiltration and metabolic fitness especially in glycolysis-low tumors. Accordingly, anti-CTLA-4 achieved better therapeutic outcomes in mice bearing glycolysis-defective tumors. Intriguingly, tumor-specific CD8+ T-cell responses correlated with phenotypic and functional destabilization of tumor-infiltrating regulatory T cells (Tregs) toward IFN-γ- and TNF-α-producing cells in glycolysis-defective tumors. By mimicking the highly and poorly glycolytic TME in vitro, we show that the effect of CTLA-4 blockade to promote Treg destabilization is dependent on Treg glycolysis and CD28 signaling. These findings indicate that decreasing tumor competition for glucose may facilitate the therapeutic activity of CTLA-4 blockade, thus supporting its combination with inhibitors of tumor glycolysis. Moreover, these results reveal a new mechanism through which anti-CTLA-4 interferes with Treg function in the presence of glucose.
    DOI:  https://doi.org/10.1038/s41586-021-03326-4
  57. Sci Transl Med. 2021 Jan 27. pii: eaba7308. [Epub ahead of print]13(578):
    Zhang H, Li F, Cao J, Wang X, Cheng H, Qi K, Wang G, Xu K, Zheng J, Fu YX, Yang X.
      Although chimeric antigen receptor (CAR)-modified T cells have shown great success in the treatment of B cell malignancies, this approach has limited efficacy in patients with solid tumors. Various modifications in CAR structure have been explored to improve this efficacy, including the incorporation of two costimulatory domains. Because costimulatory signals are transduced together with T cell receptor signals during T cell activation, we engineered a type of CAR-T cells with a costimulatory signal that was activated independently from the tumor antigen to recapitulate physiological stimulation. We screened 12 costimulatory receptors to identify OX40 as the most effective CAR-T function enhancer. Our data indicated that these new CAR-T cells showed superior proliferation capability compared to current second-generation CAR-T cells. OX40 signaling reduced CAR-T cell apoptosis through up-regulation of genes encoding Bcl-2 family members and enhanced proliferation through increased activation of the NF-κB (nuclear factor κB), MAPK (mitogen-activated protein kinase), and PI3K-AKT (phosphoinositide 3-kinase to the kinase AKT) pathways. OX40 signaling not only enhanced the cytotoxicity of CAR-T cells but also reduced exhaustion markers, thereby maintaining their function in immunosuppressive tumor microenvironments. In mouse tumor models and in patients with metastatic lymphoma, these CAR-T cells exhibited robust amplification and antitumor activity. Our findings provide an alternative option for CAR-T optimization with the potential to overcome the challenge of treating solid tumors.
    DOI:  https://doi.org/10.1126/scitranslmed.aba7308
  58. Elife. 2021 Feb 16. pii: e64693. [Epub ahead of print]10
    Chi J, Lin Z, Barr W, Crane A, Zhu XG, Cohen P.
      While beige adipocytes have been found to associate with dense sympathetic neurites in mouse inguinal subcutaneous white fat (iWAT), little is known about when and how this patterning is established. Here, we applied whole-tissue imaging to examine the development of sympathetic innervation in iWAT. We found that parenchymal neurites actively grow between postnatal day 6 (P6) and P28, overlapping with early postnatal beige adipogenesis. Constitutive deletion of Prdm16 in adipocytes led to a significant reduction in early postnatal beige adipocytes and sympathetic density within this window. Using an inducible, adipocyte-specific Prdm16 knockout model, we found that Prdm16 is required for guiding sympathetic growth during early development. Deleting Prdm16 in adult animals, however, did not affect sympathetic structure in iWAT. Together, these findings highlight that beige adipocyte-sympathetic neurite communication is crucial to establish sympathetic structure during the early postnatal period but may be dispensable for its maintenance in mature animals.
    Keywords:  developmental biology; medicine; mouse
    DOI:  https://doi.org/10.7554/eLife.64693
  59. Sci Adv. 2021 Feb;pii: eabe1122. [Epub ahead of print]7(8):
    Thiemicke A, Neuert G.
      Exposure of cells to diverse types of stressful environments differentially regulates cell fate. Although many types of stresses causing this differential regulation are known, it is unknown how changes over time of the same stressor regulate cell fate. Changes in extracellular osmolarity are critically involved in physiological and pathophysiological processes in several tissues. We observe that human cells survive gradual but not acute hyperosmotic stress. We find that stress, caspase, and apoptosis signaling do not activate during gradual stress in contrast to acute treatments. Contrary to the current paradigm, we see a substantial accumulation of proline in cells treated with gradual but not acute stresses. We show that proline can protect cells from hyperosmotic stress similar to the osmoprotection in plants and bacteria. Our studies found a cell fate switch that enables cells to survive gradually changing stress environments by preventing caspase activation and protect cells through proline accumulation.
    DOI:  https://doi.org/10.1126/sciadv.abe1122
  60. Cancer Cell. 2020 Dec 14. pii: S1535-6108(20)30606-1. [Epub ahead of print]38(6): 753-756
    Krummel M, Hu K, de Vries EGE, Goetz JG, Passaro D, Subramaniam S, Misteli T, Skala M, Bravo-Cordero JJ, Sutcliffe JL.
      Imaging has had a profound impact on our ability to understand and treat cancer. We invited some experts to discuss imaging approaches that can be used in various aspects of cancer research, from investigating the complexity and diversity of cancer cells and their environments to guiding clinical decision-making.
    DOI:  https://doi.org/10.1016/j.ccell.2020.11.014
  61. Nature. 2020 Jan 29.
    Cormick C.
      
    Keywords:  Careers; Communication; Lab life
    DOI:  https://doi.org/10.1038/d41586-020-00239-6
  62. Sci Rep. 2021 Feb 15. 11(1): 3802
    Alexander JI, Vendramini-Costa DB, Francescone R, Luong T, Franco-Barraza J, Shah N, Gardiner JC, Nicolas E, Raghavan KS, Cukierman E.
      Pancreatic Ductal Adenocarcinoma (PDAC) has a five-year survival under 10%. Treatment is compromised due to a fibrotic-like stromal remodeling process, known as desmoplasia, which limits therapeutic perfusion, supports tumor progression, and establishes an immunosuppressive microenvironment. These processes are driven by cancer-associated fibroblasts (CAFs), functionally activated through transforming growth factor beta1 (TGFβ1). CAFs produce a topographically aligned extracellular matrix (ECM) that correlates with reduced overall survival. Paradoxically, ablation of CAF populations results in a more aggressive disease, suggesting CAFs can also restrain PDAC progression. Thus, unraveling the mechanism(s) underlying CAF functions could lead to therapies that reinstate the tumor-suppressive features of the pancreatic stroma. CAF activation involves the f-actin organizing protein palladin. CAFs express two palladin isoforms (iso3 and iso4) which are up-regulated in response to TGFβ1. However, the roles of iso3 and iso4 in CAF functions remain elusive. Using a CAF-derived ECM model, we uncovered that iso3/iso4 are required to sustain TGFβ1-dependent CAF activation, secrete immunosuppressive cytokines, and produce a pro-tumoral ECM. Findings demonstrate a novel role for CAF palladin and suggest that iso3/iso4 regulate both redundant and specific tumor-supportive desmoplastic functions. This study highlights the therapeutic potential of targeting CAFs to restore fibroblastic anti-tumor activity in the pancreatic microenvironment.
    DOI:  https://doi.org/10.1038/s41598-021-82937-3
  63. Clin Cancer Res. 2021 Jan 27. pii: clincanres.3929.2020. [Epub ahead of print]
    Kim Y, Yeo I, Huh I, Kim J, Han D, Jang JY, Kim Y.
      PURPOSE: To develop and validate a protein-based, multi-marker panel that provides superior pancreatic ductal adenocarcinoma (PDAC) detection abilities with sufficient diagnostic performance.EXPERIMENTAL DESIGN: A total of 959 plasma samples from patients at multiple medical centers were used. To construct an optimal, diagnostic, multi-marker panel, we applied data preprocessing procedure to biomarker candidates. The multi-marker panel was developed using a training set comprised of 261 PDAC cases and 290 controls. Subsequent evaluations were performed in a validation set comprised of 65 PDAC cases and 72 controls. Further validation was performed in an independent set comprised of 75 PDAC cases and 47 controls.
    RESULTS: A multi-marker panel containing 14 proteins was developed. The multi-marker panel achieved areas under the curve (AUCs) of 0.977 and 0.953 for the training set and validation set, respectively. In an independent validation set, the multi-marker panel yielded an AUC of 0.928. The diagnostic performance of the multi-marker panel showed significant improvements compared with carbohydrate antigen (CA) 19-9 alone (training set AUC = 0.977 vs. 0.872, P < 0.001; validation set AUC = 0.953 vs. 0.832, P < 0.01; independent validation AUC = 0.928 vs. 0.771, P < 0.001). When the multi-marker panel and CA 19-9 were combined, the diagnostic performance of the combined panel was improved for all sets.
    CONCLUSIONS: This multi-marker panel and the combined panel showed statistically significant improvements in diagnostic performance compared with CA 19-9 alone and has the potential to complement CA19-9 as a diagnostic marker in clinical practice.
    DOI:  https://doi.org/10.1158/1078-0432.CCR-20-3929
  64. Sci Adv. 2021 Feb;pii: eabe1969. [Epub ahead of print]7(8):
    Krajina BA, LeSavage BL, Roth JG, Zhu AW, Cai PC, Spakowitz AJ, Heilshorn SC.
      Living tissues embody a unique class of hybrid materials in which active and thermal forces are inextricably linked. Mechanical characterization of tissues demands descriptors that respect this hybrid nature. In this work, we develop a microrheology-based force spectrum analysis (FSA) technique to dissect the active and passive fluctuations of the extracellular matrix (ECM) in three-dimensional (3D) cell culture models. In two different stromal models and a 3D breast cancer spheroid model, our FSA reveals emergent hybrid dynamics that involve both high-frequency stress stiffening and low-frequency fluidization of the ECM. We show that this is a general consequence of nonlinear coupling between active forces and the frequency-dependent viscoelasticity of stress-stiffening networks. In 3D breast cancer spheroids, this dual active stiffening and fluidization is tightly connected with invasion. Our results suggest a mechanism whereby breast cancer cells reconcile the seemingly contradictory requirements for both tension and malleability in the ECM during invasion.
    DOI:  https://doi.org/10.1126/sciadv.abe1969
  65. Nat Methods. 2021 Feb 15.
    Lawson M, Elf J.
      Mapping a genetic perturbation to a change in phenotype is at the core of biological research. Advances in microscopy have transformed these studies, but they have largely been confined to examining a few strains or cell lines at a time. In parallel, there has been a revolution in creating synthetic libraries of genetically altered cells with relative ease. Here we describe methods that combine these powerful tools to perform live-cell imaging of pool-generated strain libraries for improved biological discovery.
    DOI:  https://doi.org/10.1038/s41592-020-01053-8
  66. J Clin Invest. 2021 Feb 16. pii: 135963. [Epub ahead of print]
    Ferrara PJ, Rong X, Maschek JA, Verkerke AR, Siripoksup P, Song H, Green TD, Krishnan KC, Johnson JM, Turk J, Houmard JA, Lusis AJ, Drummond MJ, McClung JM, Cox JE, Shaikh SR, Tontonoz P, Holland WL, Funai K.
      Aberrant lipid metabolism promotes the development of skeletal muscle insulin resistance, but the exact identity of lipid-mediated mechanisms relevant to human obesity remains unclear. A comprehensive lipidomic analysis of primary myocytes from lean insulin-sensitive (LN) and obese insulin-resistant (OB) individuals revealed several species of lysophospholipids (lyso-PL) that were differentially-abundant. These changes coincided with greater expression of lysophosphatidylcholine acyltransferase 3 (LPCAT3), an enzyme involved in phospholipid transacylation (Lands cycle). Strikingly, mice with skeletal muscle-specific knockout of LPCAT3 (LPCAT3-MKO) exhibited greater muscle lyso-PC/PC, concomitant with improved skeletal muscle insulin sensitivity. Conversely, skeletal muscle-specific overexpression of LPCAT3 (LPCAT3-MKI) promoted glucose intolerance. The absence of LPCAT3 reduced phospholipid packing of cellular membranes and increased plasma membrane lipid clustering, suggesting that LPCAT3 affects insulin receptor phosphorylation by modulating plasma membrane lipid organization. In conclusion, obesity accelerates the skeletal muscle Lands cycle, whose consequence might induce the disruption of plasma membrane organization that suppresses muscle insulin action.
    Keywords:  Insulin signaling; Metabolism; Muscle Biology; Skeletal muscle
    DOI:  https://doi.org/10.1172/JCI135963
  67. Cancer Metab. 2021 Feb 19. 9(1): 10
    Pacheco-Torres J, Penet MF, Mironchik Y, Krishnamachary B, Bhujwalla ZM.
      BACKGROUND: Harnessing the power of the immune system by using immune checkpoint inhibitors has resulted in some of the most exciting advances in cancer treatment. The full potential of this approach has, however, not been fully realized for treating many cancers such as pancreatic and breast cancer. Cancer metabolism influences many aspects of cancer progression including immune surveillance. An expanded understanding of how cancer metabolism can directly impact immune checkpoints may allow further optimization of immunotherapy. We therefore investigated, for the first time, the relationship between the overexpression of choline kinase-α (Chk-α), an enzyme observed in most cancers, and the expression of the immune checkpoint PD-L1.METHODS: We used small interfering RNA to downregulate Chk-α, PD-L1, or both in two triple-negative human breast cancer cell lines (MDA-MB-231 and SUM-149) and two human pancreatic ductal adenocarcinoma cell lines (Pa09C and Pa20C). The effects of the downregulation were studied at the genomic, proteomic, and metabolomic levels. The findings were compared with the results obtained by the analysis of public data from The Cancer Genome Atlas Program.
    RESULTS: We identified an inverse dependence between Chk-α and PD-L1 at the genomic, proteomic, and metabolomic levels. We also found that prostaglandin-endoperoxide synthase 2 (COX-2) and transforming growth factor beta (TGF-β) play an important role in this relationship. We independently confirmed this relationship in human cancers by analyzing data from The Cancer Genome Atlas Program.
    CONCLUSIONS: Our data identified previously unknown roles of PD-L1 in cancer cell metabolic reprogramming, and revealed the immunosuppressive increased PD-L1 effect of Chk-α downregulation. These data suggest that PD-L1 regulation of metabolism may be mediated through Chk-α, COX-2, and TGF-β. The observations provide new insights that can be applied to the rational design of combinatorial therapies targeting immune checkpoints and cancer metabolism.
    Keywords:  Breast cancer; COX-2; Choline kinase alpha; Immune checkpoints; PD-L1
    DOI:  https://doi.org/10.1186/s40170-021-00245-w
  68. Nutr Res. 2020 Dec 24. pii: S0271-5317(20)30602-3. [Epub ahead of print]88 1-18
    Wirkus J, Ead AS, Mackenzie GG.
      A significant number of pancreatic cancer cases are due to modifiable risk factors, with many being attributed to increased body fatness. This has sparked investigators to examine the role played by high dietary fat intake in pancreatic cancer development and the mechanisms driving this connection. However, there is currently no consensus on how dietary fat quantity and composition specifically affect pancreatic carcinogenesis. The objective of this narrative review is to discuss the link between high total fat consumption and fatty acid composition (saturated, mono-, or poly-unsaturated fats) with pancreatic cancer incidence and progression. Following our detailed analysis of the strengths and weaknesses of recent preclinical and human studies, we discuss existing research gaps and opportunities, and provide recommendations for future studies. Numerous studies suggest that diets high in omega-3 polyunsaturated fatty acids are associated with reduced pancreatic cancer risk. However, the current evidence appears insufficient for a general conclusion regarding the impact of other types of fat in pancreatic carcinogenesis, with many studies providing inconclusive findings due to study limitations. Thus, we recommend future studies to include detailed methodology of the animal experiments, not limited to the diet composition, type of ingredients, formulations, and administration of the diets. Moreover, human studies should include a diverse population and well-characterized biomarkers for accurate determination of dietary fat intake. Ultimately, this will aid the study rigor, and improve our understanding of the impact of fat quantity and composition in pancreatic carcinogenesis.
    Keywords:  Diet; Fat; Lipids; Obesity; Pancreatic cancer; Pancreatic cancer risk
    DOI:  https://doi.org/10.1016/j.nutres.2020.12.018
  69. Br J Surg. 2021 Feb 20. pii: znaa115. [Epub ahead of print]
    Pausch TM, Mitzscherling C, Aubert O, Liu X, Gesslein B, Bruckner T, Kommoss FKF, Golriz M, Mehrabi A, Hackert T.
      Leaking pancreatic fluid can contribute to postoperative pancreatic fistula (POPF), which can complicate pancreatic surgery. Surgeons lack reliable tools to identify pancreatic leaks, so a novel hydrogel indicator called SmartPAN was developed for intraoperative application. In this preclinical efficacy assessment study, SmartPAN was capable of detecting sites associated with biochemical leak and POPF-related symptoms, thereby guiding effective closure. Thus, SmartPAN may help to reduce POPF development in upcoming clinical trials.
    DOI:  https://doi.org/10.1093/bjs/znaa115
  70. Mol Cell. 2021 Feb 18. pii: S1097-2765(21)00053-8. [Epub ahead of print]81(4): 708-723.e5
    Mukherjee R, Vanaja KG, Boyer JA, Gadal S, Solomon H, Chandarlapaty S, Levchenko A, Rosen N.
      The PI3K pathway regulates cell metabolism, proliferation, and migration, and its dysregulation is common in cancer. We now show that both physiologic and oncogenic activation of PI3K signaling increase the expression of its negative regulator PTEN. This limits the duration of the signal and output of the pathway. Physiologic and pharmacologic inhibition of the pathway reduces PTEN and contributes to the rebound in pathway activity in tumors treated with PI3K inhibitors and limits their efficacy. Regulation of PTEN is due to mTOR/4E-BP1-dependent control of its translation and is lost when 4E-BP1 is deleted. Translational regulation of PTEN is therefore a major homeostatic regulator of physiologic PI3K signaling and plays a role in reducing the pathway activation by oncogenic PIK3CA mutants and the antitumor activity of PI3K pathway inhibitors. However, pathway output is hyperactivated in tumor cells with coexistent PI3K mutation and loss of PTEN function.
    Keywords:  4E-BP; BYL-719; PI3K signaling; PTEN regulation; PTEN translation; computational model of PI3K signaling; growth factor signaling; mTOR; negative feedback; resistance to PI3K inhibition
    DOI:  https://doi.org/10.1016/j.molcel.2021.01.033
  71. Nature. 2021 Feb 17.
    Ibbett D.
      
    Keywords:  Arts; Careers; Physics
    DOI:  https://doi.org/10.1038/d41586-021-00398-0
  72. Phys Rev E. 2021 Jan;103(1-1): 012610
    Chieco AT, Durian DJ.
      We present high-precision data for the time evolution of bubble area A(t) and circularity shape parameter C(t) for several bubbles in a quasi-two-dimensional foams consisting of bubbles squashed between parallel plates. In order to fully compare with earlier predictions, foam wetness is systematically varied by controlling the height of the sample above a liquid reservoir which in turn controls the radius r of the inflation of the Plateau borders. For very dry foams, where the borders are very small, classic von Neumann behavior is observed where a bubble's growth rate depends only on its number n of sides. For wet foams, the inflated borders impede gas exchange and cause deviations from von Neumann's law that are found to be in accord with the generalized coarsening equation. In particular, the overall growth rate varies linearly with the film height, which decrease as surface Plateau borders inflate. More interestingly, the deviation from dA/dt∝(n-6) von Neumann behavior grows in proportion to nCr/sqrt[A]. This is highlighted definitively by data for six-sided bubbles, which are forbidden to grow or shrink except for the existence of this term. It is tested quantitatively by variation of all four relevant quantities: n, C, r, and A.
    DOI:  https://doi.org/10.1103/PhysRevE.103.012610
  73. Nature. 2021 Feb 17.
    Arnould C, Rocher V, Finoux AL, Clouaire T, Li K, Zhou F, Caron P, Mangeot PE, Ricci EP, Mourad R, Haber JE, Noordermeer D, Legube G.
      The repair of DNA double-strand breaks (DSBs) is essential for safeguarding genome integrity. When a DSB forms, the PI3K-related ATM kinase rapidly triggers the establishment of megabase-sized, chromatin domains decorated with phosphorylated histone H2AX (γH2AX), which act as seeds for the formation of DNA-damage response foci1. It is unclear how these foci are rapidly assembled to establish a 'repair-prone' environment within the nucleus. Topologically associating domains are a key feature of 3D genome organization that compartmentalize transcription and replication, but little is known about their contribution to DNA repair processes2,3. Here we show that topologically associating domains are functional units of the DNA damage response, and are instrumental for the correct establishment of γH2AX-53BP1 chromatin domains in a manner that involves one-sided cohesin-mediated loop extrusion on both sides of the DSB. We propose a model in which H2AX-containing nucleosomes are rapidly phosphorylated as they actively pass by DSB-anchored cohesin. Our work highlights the importance of chromosome conformation in the maintenance of genome integrity and demonstrates the establishment of a chromatin modification by loop extrusion.
    DOI:  https://doi.org/10.1038/s41586-021-03193-z