bims-cagime Biomed News
on Cancer, aging and metabolism
Issue of 2020‒10‒25
fifty-seven papers selected by
Kıvanç Görgülü
Technical University of Munich

  1. Mol Cancer Res. 2020 Oct 23. pii: molcanres.0336.2020. [Epub ahead of print]
      Elevated NF-κB activity is a contributory factor in many haematological and solid malignancies. Nucleolar sequestration of NF-κB/RelA represses this elevated activity and mediates apoptosis of cancer cells. Here we set out to understand the mechanisms that control the nuclear/nucleolar distribution of RelA and other regulatory proteins, so that agents can be developed that specifically target these proteins to the organelle. We demonstrate that RelA accumulates in intra-nucleolar aggresomes in response to specific stresses. We also demonstrate that the autophagy receptor, SQSTM1/p62, accumulates alongside RelA in these nucleolar aggresomes. This accumulation is not a consequence of inhibited autophagy. Indeed, our data suggest nucleolar and autophagosomal accumulation of p62 are in active competition. We identify a conserved motif at the N-terminus of p62 that is essential for nucleoplasmic-to nucleolar transport of the protein. Furthermore, using a dominant negative mutant deleted for this nucleolar localisation signal (NoLS), we demonstrate a role for p62 in trafficking RelA and other aggresome-related proteins to nucleoli, to induce apoptosis. Together, these data identify a novel role for p62 in trafficking nuclear proteins to nucleolar aggresomes under conditions of cell stress, thus maintaining cellular homeostasis. They also provide invaluable information on the mechanisms that regulate the nuclear/nucleolar distribution of RelA that could be exploited for therapeutic purpose. Implications: The data open up avenues for the development of a unique class of therapeutic agents that act by targeting RelA and other aberrantly active proteins to nucleoli, thus killing cancer cells.
  2. Cancers (Basel). 2020 Oct 16. pii: E3005. [Epub ahead of print]12(10):
      Autophagy is a mechanism of lysosomal proteolysis that is utilized to degrade damaged organelles, proteins, and other cellular components. Although key studies demonstrate that autophagy functions as a mechanism of tumor suppression via the degradation of defective pre-malignant cells, autophagy can also be used as a mechanism to break down cellular components under stress conditions to generate the required metabolic materials for cell survival. Autophagy has emerged as an important mediator of resistance to radiation, chemotherapy, and targeted agents. This series of articles highlight the role of autophagy in cancer progression and drug resistance and underscores the need for new and more effective agents that target this process.
    Keywords:  ROC-325; autophagy; cancer; drug resistance; lysosome
  3. Nat Commun. 2020 10 20. 11(1): 5297
      Extrachromosomal telomeric circles are commonly invoked as important players in telomere maintenance, but their origin has remained elusive. Using electron microscopy analysis on purified telomeres we show that, apart from known structures, telomeric repeats accumulate internal loops (i-loops) that occur in the proximity of nicks and single-stranded DNA gaps. I-loops are induced by single-stranded damage at normal telomeres and represent the majority of telomeric structures detected in ALT (Alternative Lengthening of Telomeres) tumor cells. Our data indicate that i-loops form as a consequence of the exposure of single-stranded DNA at telomeric repeats. Finally, we show that these damage-induced i-loops can be excised to generate extrachromosomal telomeric circles resulting in loss of telomeric repeats. Our results identify damage-induced i-loops as a new intermediate in telomere metabolism and reveal a simple mechanism that links telomere damage to the accumulation of extrachromosomal telomeric circles and to telomere erosion.
  4. Cancer Cell. 2020 Oct 21. pii: S1535-6108(20)30488-8. [Epub ahead of print]
      Most drugs entering clinical trials fail, often related to an incomplete understanding of the mechanisms governing drug response. Machine learning techniques hold immense promise for better drug response predictions, but most have not reached clinical practice due to their lack of interpretability and their focus on monotherapies. We address these challenges by developing DrugCell, an interpretable deep learning model of human cancer cells trained on the responses of 1,235 tumor cell lines to 684 drugs. Tumor genotypes induce states in cellular subsystems that are integrated with drug structure to predict response to therapy and, simultaneously, learn biological mechanisms underlying the drug response. DrugCell predictions are accurate in cell lines and also stratify clinical outcomes. Analysis of DrugCell mechanisms leads directly to the design of synergistic drug combinations, which we validate systematically by combinatorial CRISPR, drug-drug screening in vitro, and patient-derived xenografts. DrugCell provides a blueprint for constructing interpretable models for predictive medicine.
    Keywords:  cancer; drug synergy; interpretable deep learning; machine learning; network modeling; precision medicine
  5. Nature. 2020 Oct 21.
      The immune system uses two distinct defence strategies against infections: microbe-directed pathogen destruction characterized by type 1 immunity1, and host-directed pathogen containment exemplified by type 2 immunity in induction of tissue repair2. Similar to infectious diseases, cancer progresses with self-propagating cancer cells inflicting host-tissue damage. The immunological mechanisms of cancer cell destruction are well defined3-5, but whether immune-mediated cancer cell containment can be induced remains poorly understood. Here we show that depletion of transforming growth factor-β receptor 2 (TGFBR2) in CD4+ T cells, but not CD8+ T cells, halts cancer progression as a result of tissue healing and remodelling of the blood vasculature, causing cancer cell hypoxia and death in distant avascular regions. Notably, the host-directed protective response is dependent on the T helper 2 cytokine interleukin-4 (IL-4), but not the T helper 1 cytokine interferon-γ (IFN-γ). Thus, type 2 immunity can be mobilized as an effective tissue-level defence mechanism against cancer.
  6. Mol Cell Biol. 2020 Oct 19. pii: MCB.00512-20. [Epub ahead of print]
      Senescence is a state of long-term cell-cycle arrest that arises in cells that have incurred sub-lethal damage. While senescent cells no longer replicate, they remain metabolically active and further develop unique and stable phenotypes that are not present in proliferating cells. On one hand, senescent cells increase in size, maintain an active mTORC1 complex, and produce and secrete a substantial amount of inflammatory proteins as part of the senescence associated secretory phenotype (SASP). On the other hand, these pro-growth phenotypes contrast with the p53-mediated growth arrest typical of senescent cells that is associated with nucleolar stress and an inhibition of rRNA processing and ribosome biogenesis. In sum, translation in senescent cells paradoxically comprises both a global repression of translation triggered by DNA damage and a select increase in the translation of specific proteins, including SASP factors.
  7. Sci Adv. 2020 Oct;pii: eabc3175. [Epub ahead of print]6(43):
      The extracellular matrix (ECM), a major component of the tumor microenvironment, promotes local invasion to drive metastasis. Here, we describe a method to study whole-tissue ECM effects from disease states associated with metastasis on tumor cell phenotypes and identify the individual ECM proteins and signaling pathways that are driving these effects. We show that decellularized ECM from tumor-bearing and obese mammary glands drives TNBC cell invasion. Proteomics of the ECM from the obese mammary gland led us to identify full-length collagen VI as a novel driver of TNBC cell invasion whose abundance in tumor stroma increases with body mass index in human TNBC patients. Last, we describe the mechanism by which collagen VI contributes to TNBC cell invasion via NG2-EGFR cross-talk and MAPK signaling. Overall, these studies demonstrate the value of decellularized ECM scaffolds obtained from tissues to identify novel functions of the ECM.
  8. Proc Natl Acad Sci U S A. 2020 Oct 23. pii: 202006445. [Epub ahead of print]
      The Rac-GEF, P-Rex1, activates Rac1 signaling downstream of G protein-coupled receptors and PI3K. Increased P-Rex1 expression promotes melanoma progression; however, its role in breast cancer is complex, with differing reports of the effect of its expression on disease outcome. To address this we analyzed human databases, undertook gene array expression analysis, and generated unique murine models of P-Rex1 gain or loss of function. Analysis of PREX1 mRNA expression in breast cancer cDNA arrays and a METABRIC cohort revealed that higher PREX1 mRNA in ER+ve/luminal tumors was associated with poor outcome in luminal B cancers. Prex1 deletion in MMTV-neu or MMTV-PyMT mice reduced Rac1 activation in vivo and improved survival. High level MMTV-driven transgenic PREX1 expression resulted in apicobasal polarity defects and increased mammary epithelial cell proliferation associated with hyperplasia and development of de novo mammary tumors. MMTV-PREX1 expression in MMTV-neu mice increased tumor initiation and enhanced metastasis in vivo, but had no effect on primary tumor growth. Pharmacological inhibition of Rac1 or MEK1/2 reduced P-Rex1-driven tumoroid formation and cell invasion. Therefore, P-Rex1 can act as an oncogene and cooperate with HER2/neu to enhance breast cancer initiation and metastasis, despite having no effect on primary tumor growth.
    Keywords:  breast cancer; cell polarity; guanine nucleotide exchange factor (GEF); metastasis; transgenic mouse
  9. Mol Biol Cell. 2020 Oct 21. mbcE20090585
      Accurate chromosome alignment at metaphase facilitates the equal segregation of sister chromatids to each of the nascent daughter cells. Lack of proper metaphase alignment is an indicator of defective chromosome congression and aberrant kinetochore-microtubule attachments which in turn promotes chromosome missegregation and aneuploidy, hallmarks of cancer. Tools to sensitively, accurately and quantitatively measure chromosome alignment at metaphase will facilitate understanding of the contribution of chromosome segregation errors to the development of aneuploidy. In this work, we have developed and validated a method based on analytical geometry to measure several indicators of chromosome misalignment. We generated semi-automated and flexible ImageJ2/Fiji pipelines to quantify kinetochore misalignment at metaphase plates as well as lagging chromosomes at anaphase. These tools will ultimately allow sensitive and systematic quantitation of these chromosome segregation defects in cells undergoing mitosis.
  10. J Biol Chem. 2020 10 22. pii: jbc.REV120.013529. [Epub ahead of print]
      The two branches of the Kennedy pathways (CDP-choline and CDP-ethanolamine) are the predominant pathways responsible for the synthesis of the most abundant phospholipids, phosphatidylcholine and phosphatidylethanolamine, respectively, in mammalian membranes. Recently, hereditary diseases associated with single gene mutations in the Kennedy pathways have been identified. Interestingly, genetic diseases within the same pathway vary greatly, ranging from muscular dystrophy to spastic paraplegia to a childhood blinding disorder to bone deformations. Indeed, different point mutations in the same gene (PCYT1; CCTα) result in at least three distinct diseases. In this review article, we will summarize and review the genetic diseases associated with mutations in genes of the Kennedy pathway for phospholipid synthesis. These single gene disorders provide insight, indeed direct genotype-phenotype relationships, into the biological functions of specific enzymes of the Kennedy pathway. We discuss potential mechanisms of how mutations within the same pathway can cause disparate disease.
    Keywords:  genetic disease; inherited; lipid; membrane; metabolism; phosphatidylcholine; phosphatidylethanolamine; phospholipid
  11. Elife. 2020 Oct 20. pii: e58815. [Epub ahead of print]9
      The relationship between lipid metabolism and longevity remains unclear. Although fat oxidation is essential for weight loss, whether it remains beneficial when sustained for long periods, and the extent to which it may attenuate or augment lifespan remain important unanswered questions. Here, we develop an experimental handle in the Caenorhabditis elegans model system, in which we uncover the mechanisms that connect long-term fat oxidation with longevity. We find that sustained β-oxidation via activation of the conserved triglyceride lipase ATGL-1, triggers a feedback transcriptional loop that involves the mito-nuclear transcription factor ATFS-1, and a previously unknown and highly conserved repressor of ATGL-1 called HLH-11/AP4. This feedback loop orchestrates the dual control of fat oxidation and lifespan, and shields the organism from life-shortening mitochondrial stress in the face of continuous fat oxidation. Thus, we uncover one mechanism by which fat oxidation can be sustained for long periods without deleterious effects on longevity.
    Keywords:  C. elegans; cell biology; lifespan; lipid oxidation; mitochondrial stress; neuroscience
  12. Autophagy. 2020 Oct 19.
      Macroautophagy/autophagy delivers cytoplasmic cargo to lysosomes for degradation. In yeast, the single Atg8 protein plays a role in the formation of autophagosomes whereas in mammalian cells there are five to seven paralogs, referred to as mammalian Atg8s (mAtg8s: GABARAP, GABARAPL1, GABARAPL2, LC3A, LC3B, LC3B2 and LC3C) with incompletely defined functions. Here we show that a subset of mAtg8s directly control lysosomal biogenesis. This occurs at the level of TFEB, the principal regulator of the lysosomal transcriptional program. mAtg8s promote TFEB's nuclear translocation in response to stimuli such as starvation. GABARAP interacts directly with TFEB, whereas RNA-Seq analyses reveal that knockout of six genes encoding mAtg8s, or a triple knockout of the genes encoding all GABARAPs, diminishes the TFEB transcriptional program. We furthermore show that GABARAPs in cooperation with other proteins, IRGM, a factor implicated in tuberculosis and Crohn disease, and STX17, are required during starvation for optimal inhibition of MTOR, an upstream kinase of TFEB, and activation of the PPP3/calcineurin phosphatase that dephosphorylates TFEB, thus promoting its nuclear translocation. In conclusion, mAtg8s, IRGM and STX17 control lysosomal biogenesis by their combined or individual effects on MTOR, TFEB, and PPP3/calcineurin, independently of their roles in the formation of autophagosomal membranes.
    Keywords:  Crohn’s disease; GABARAP; HIV; LC3; MTOR; Mycobacterium tuberculosis; TFEB; autophagy; lysosome; metabolism
  13. Trends Pharmacol Sci. 2020 Oct 19. pii: S0165-6147(20)30214-5. [Epub ahead of print]
      Pancreatic ductal adenocarcinoma (PDAC) is one of the most lethal cancers in humans due to late detection and highly metastatic characteristics. PDAC cells vary in their tumorigenic capabilities with the presence of a subset of PDAC cells known as pancreatic cancer stem cells (CSCs), which are more resistant to currently used therapeutics. Here, we describe the role of CSCs and tumour stroma in developing therapeutic strategies for PDAC and suggest that developmental plasticity could be considered a hallmark of cancers. We provide an overview of the molecular targets in PDAC treatments, including targeted therapies of cellular processes such as proliferation, evasion of growth suppressors, activating metastasis, and metabolic effects. Since PDAC is an inflammation-driven cancer, we also revisit therapeutic strategies targeting inflammation and immunotherapy. Lastly, we suggest that targeting epigenetic mechanisms opens therapeutic routes for heterogeneous cancer cell populations, including CSCs.
    Keywords:  cancer hallmarks; cancer stem cells; cancer therapy; pancreatic ductal adenocarcinoma; signalling pathways; tumour stroma
  14. J Cell Sci. 2020 Oct 18. pii: jcs.247379. [Epub ahead of print]
      Survivin is a cancer-associated protein that is pivotal for cellular life and death: it is an essential mitotic protein and an inhibitor of apoptosis. In cancer cells, a small pool of survivin localises to the mitochondria, the function of which remains to be elucidated. Here, we report that mitochondrial survivin inhibits the selective form of autophagy, called "mitophagy", causing an accumulation of respiratory defective mitochondria. Mechanistically the data reveal that survivin prevents recruitment of the E3-ubiquitin ligase Parkin to mitochondria and their subsequent recognition by the autophagosome. The data also demonstrate that cells in which mitophagy has been blocked by survivin expression have an increased dependency on glycolysis. As these effects were found exclusively in cancer cells they suggest that the primary act of mitochondrial survivin is to steer cells towards the implementation of the Warburg transition by inhibiting mitochondrial turnover, which enables them to adapt and survive.
    Keywords:  Cancer; Mitochondria; Mitophagy; Respiration; Survivin
  15. Gut. 2020 Oct 21. pii: gutjnl-2020-320608. [Epub ahead of print]
      OBJECTIVE: Pancreatic ductal adenocarcinoma (PDAC) is the deadliest cancer. Cancer-associated thrombosis/thromboembolism (CAT), frequently observed in PDAC, is known as a poor prognostic factor. Here, we investigated the underlying mechanisms between PDAC and CAT, and performed a trial of therapeutic approach for PDAC using a genetically engineered mouse model, PKF (Ptf1acre/+;LSL-KrasG12D/+;Tgfbr2flox/flox ).DESIGN: Presence of CAT in PKF mice was detected by systemic autopsy. Plasma cytokines were screened by cytokine antibody array. Murine and human plasma atrial natriuretic peptide (ANP) and soluble vascular cell adhesion molecule 1 (sVCAM-1) were determined by ELISA. Distribution of VCAM-1 in PKF mice and human autopsy samples was detected by immunohistochemistry. PKF mice were treated with anti-VCAM-1 antibody and the effects on survival, distribution of CAT and the tumour histology were analysed.
    RESULTS: We found spontaneous CAT with cardiomegaly in 68.4% PKF mice. Increase of plasma ANP and sVCAM-1 was observed in PKF mice and PDAC patients with CAT. VCAM-1 was detected in the activated endothelium and thrombi. Administration of anti-VCAM-1 antibody to PKF mice inhibited tumour growth, neutrophil/macrophage infiltration, tumour angiogenesis and progression of CAT; moreover, it dramatically extended survival (from 61 to 253 days, p<0.01).
    CONCLUSION: Blocking VCAM-1/sVCAM-1 might be a potent therapeutic approach for PDAC as well as CAT, which can contribute to the prognosis. Increase of plasma ANP and sVCAM-1 might be a diagnostic approach for CAT in PDAC.
    Keywords:  cell adhesion molecules; pancreatic cancer
  16. Nat Metab. 2020 Oct 19.
      Enhanced growth and proliferation of cancer cells are accompanied by profound changes in cellular metabolism. These metabolic changes are also common under physiological conditions, and include increased glucose fermentation accompanied by elevated cytosolic pH (pHc)1,2. However, how these changes contribute to enhanced cell growth and proliferation is unclear. Here, we show that elevated pHc specifically orchestrates an E2F-dependent transcriptional programme to drive cell proliferation by promoting cyclin D1 expression. pHc-dependent transcription of cyclin D1 requires the transcription factors CREB1, ATF1 and ETS1, and the histone acetyltransferases p300 and CBP. Biochemical characterization revealed that the CREB1-p300/CBP interaction acts as a pH sensor and coincidence detector, integrating different mitotic signals to regulate cyclin D1 transcription. We also show that elevated pHc contributes to increased cyclin D1 expression in malignant pleural mesotheliomas (MPMs), and renders these cells hypersensitive to pharmacological reduction of pHc. Taken together, these data demonstrate that elevated pHc is a critical cellular signal regulating G1 progression, and provide a mechanism linking elevated pHc to oncogenic activation of cyclin D1 in MPMs, and possibly other cyclin D1~dependent tumours. Thus, an increase of pHc may represent a functionally important, early event in the aetiology of cancer that is amenable to therapeutic intervention.
  17. Mol Syst Biol. 2020 Oct;16(10): e9518
      Activating mutations in RAS are present in ~ 30% of human tumors, and the resulting aberrations in ERK/MAPK signaling play a central role in oncogenesis. However, the form of these signaling changes is uncertain, with activating RAS mutants linked to both increased and decreased ERK activation in vivo. Rationally targeting the kinase activity of this pathway requires clarification of the quantitative effects of RAS mutations. Here, we use live-cell imaging in cells expressing only one RAS isoform to quantify ERK activity with a new level of accuracy. We find that despite large differences in their biochemical activity, mutant KRAS isoforms within cells have similar ranges of ERK output. We identify roles for pathway-level effects, including variation in feedback strength and feedforward modulation of phosphatase activity, that act to rescale pathway sensitivity, ultimately resisting changes in the dynamic range of ERK activity while preserving responsiveness to growth factor stimuli. Our results reconcile seemingly inconsistent reports within the literature and imply that the signaling changes induced by RAS mutations early in oncogenesis are subtle.
    Keywords:  FRET biosensor; RAS disease; computational modeling; epidermal growth factor; single-cell kinetics
  18. Cancer Drug Resist. 2020 ;3 572-585
      Aim: Gemcitabine is a frontline agent for locally-advanced and metastatic pancreatic ductal adenocarcinoma (PDAC), but neither gemcitabine alone nor in combination produces durable remissions of this tumor type. We developed three PDAC patient-derived xenograft (PDX) models with gemcitabine resistance (gemR) acquired in vivo, with which to identify mechanisms of resistance relevant to drug exposure in vivo and to evaluate novel therapies.Methods: Mice bearing independently-derived PDXs received 100 mg/kg gemcitabine once or twice weekly. Tumors initially responded, but regrew on treatment and were designated gemR. We used immunohistochemistry to compare expression of proteins previously associated with gemcitabine resistance [ribonucleotide reductase subunit M1 (RRM1), RRM2, human concentrative nucleoside transporter 1 (hCNT1), human equilibrative nucleoside transporter 1 (hENT1), cytidine deaminase (CDA), and deoxycytidine kinase (dCK)] in gemR and respective gemcitabine-naive parental tumors.
    Results: Parental and gemR tumors did not differ in tumor cell morphology, amount of tumor-associated stroma, or expression of stem cell markers. No consistent pattern of expression of the six gemR marker proteins was observed among the models. Increases in RRM1 and CDA were consistent with in vitro-derived gemR models. However, rather than the expected decreases of hCNT1, hENT1, and dCK, gemR tumors expressed no change in or higher levels of these gemR marker proteins than parental tumors.
    Conclusion: These models are the first PDAC PDX models with gemcitabine resistance acquired in vivo. The data indicate that mechanisms identified in models with resistance acquired in vitro are unlikely to be the predominant mechanisms when resistance is acquired in vivo. Ongoing work focuses on characterizing unidentified mechanisms of gemR and on identifying agents with anti-tumor efficacy in these gemR models.
    Keywords:  cytidine deaminase; deoxycytidine kinase; gemcitabine resistance; human concentrative nucleoside transporter 1; human equilibrative nucleoside transporter 1; patient-derived xenograft; ribonucleotide reductase subunit M1; ribonucleotide reductase subunit M2
  19. J Cell Biol. 2020 Dec 07. pii: e202002144. [Epub ahead of print]219(12):
      Mitochondria are dynamic organelles with essential roles in signaling and metabolism. We recently identified a cellular structure called the mitochondrial-derived compartment (MDC) that is generated from mitochondria in response to amino acid overabundance stress. How cells form MDCs is unclear. Here, we show that MDCs are dynamic structures that form and stably persist at sites of contact between the ER and mitochondria. MDC biogenesis requires the ER-mitochondria encounter structure (ERMES) and the conserved GTPase Gem1, factors previously implicated in lipid exchange and membrane tethering at ER-mitochondria contacts. Interestingly, common genetic suppressors of abnormalities displayed by ERMES mutants exhibit distinct abilities to rescue MDC formation in ERMES-depleted strains and are incapable of rescuing MDC formation in cells lacking Gem1. Thus, the function of ERMES and Gem1 in MDC biogenesis may extend beyond their conventional role in maintaining mitochondrial phospholipid homeostasis. Overall, this study identifies an important function for ER-mitochondria contacts in the biogenesis of MDCs.
  20. FEBS J. 2020 Oct 22.
      Autophagy is the main catabolic process by which cells recycle cytoplasmic components and superfluous or damaged organelles to preserve metabolic homeostasis under normal conditions and promote survival under stress. As a tightly regulated and dynamic process, autophagy has critical roles in development and cell differentiation, immune function, organismal health and lifespan. Accumulating findings suggest that defective or dysregulated autophagy accelerates ageing and increases susceptibility to diseases, such as neurodegenerative disorders and cancer, among others. This virtual issue of the FEBS Journal on Autophagy includes a collection of articles that present recent advances on the regulation of autophagy and provide a view of its complex roles in physiological and pathological contexts.
  21. J Cell Sci. 2020 Oct 19. pii: jcs.248336. [Epub ahead of print]
      Lysosomes are compartments for the degradation of both endocytic and autophagic cargoes. The shape of lysosomes changes with cellular degradative demands, however, there is limited knowledge about the mechanisms or significance that underlies distinct lysosomal morphologies. Here, we found an extensive tubular autolysosomal network in Drosophila abdominal muscle remodeling during metamorphosis. The tubular network transiently appeared and exhibited the capacity to degrade autophagic cargoes. The tubular autolysosomal network was uniquely marked by the autophagic SNARE protein, Syntaxin 17, and its formation depended on both autophagic flux and degradative function, with the exception of the Atg12 and Atg8 ubiquitin-like conjugation systems. Among ATG-deficient mutants, the efficiency of lysosomal tubulation correlated with the phenotypic severity in muscle remodeling. The lumen of the tubular network was continuous and homogeneous across a broad region of the remodeling muscle. Altogether, we revealed that the dynamic expansion of a tubular autolysosomal network synchronizes the abundant degradative activity required for developmentally regulated muscle remodeling.
    Keywords:  Atrophy; Autolysosome; Drosophila; Metamorphosis; Muscle; Syntaxin17
  22. Biophys J. 2020 Oct 14. pii: S0006-3495(20)30777-3. [Epub ahead of print]
      Experimental evidence for age-dependent loss of intracellular water content as a widespread concomitant of cellular senescence is reviewed. Quantitative models are presented indicating that an age-dependent increase in macromolecular crowding resulting from water loss may be responsible for three observed phenomena: a general age-dependent loss of intracellular protein solubility, a delayed and rapid appearance of high molecular weight aggregates, and an age-dependent transfer of intracellular protein from dilute to concentrated or condensed phases.
    Keywords:  Excluded volume; hemoglobin A; hemoglobin S; intracellular phase transition; protein fibrillation; protein solubility
  23. Cell Stem Cell. 2020 Oct 10. pii: S1934-5909(20)30493-8. [Epub ahead of print]
      Aging is associated with reduced fitness and increased myeloid bias of the hematopoietic stem cell (HSC) compartment, causing increased risk of immune compromise, anemia, and malignancy. We show that mitochondrial membrane potential (MMP) can be used to prospectively isolate chronologically old HSCs with transcriptional features and functional attributes characteristic of young HSCs, including a high rate of transcription and balanced lineage-affiliated programs. Strikingly, MMP is a stronger determinant of the quantitative and qualitative transcriptional state of HSCs than chronological age, and transcriptional consequences of manipulation of MMP in HSCs within their native niche suggest a causal relationship. Accordingly, we show that pharmacological enhancement of MMP in old HSCs in vivo increases engraftment potential upon transplantation and reverses myeloid-biased peripheral blood output at steady state. Our results demonstrate that MMP is a source of heterogeneity in old HSCs, and its pharmacological manipulation can alter transcriptional programs with beneficial consequences for function.
    Keywords:  Aging; Hematopoietc Stem Cell; Lineage bias; Mitochondria; Mitochondrial Membrane Potential; Mitoquinol; Transcription Rate
  24. J Cell Sci. 2020 Oct 21. pii: jcs240341. [Epub ahead of print]133(20):
      All mammalian cells live in the aqueous medium, yet for many cell biologists, water is a passive arena in which proteins are the leading players that carry out essential biological functions. Recent studies, as well as decades of previous work, have accumulated evidence to show that this is not the complete picture. Active fluxes of water and solutes of water can play essential roles during cell shape changes, cell motility and tissue function, and can generate significant mechanical forces. Moreover, the extracellular resistance to water flow, known as the hydraulic resistance, and external hydraulic pressures are important mechanical modulators of cell polarization and motility. For the cell to maintain a consistent chemical environment in the cytoplasm, there must exist an intricate molecular system that actively controls the cell water content as well as the cytoplasmic ionic content. This system is difficult to study and poorly understood, but ramifications of which may impact all aspects of cell biology from growth to metabolism to development. In this Review, we describe how mammalian cells maintain the cytoplasmic water content and how water flows across the cell surface to drive cell movement. The roles of mechanical forces and hydraulic pressure during water movement are explored.
    Keywords:  Cell size regulation; Hydraulic pressure; Hydraulic resistance; Ion homeostasis; Osmotic engine model; Osmotic pressure; Two-phase model
  25. Cell Death Differ. 2020 Oct 21.
      Selective autophagic degradation of mitochondria (mitophagy) is important in maintaining proper cellular homeostasis. Here, we found that SPATA33 is a novel autophagy mediator for mitophagy in testis. The SPATA33 protein localizes on mitochondria via its binding of the carboxyl terminal with the outer mitochondrial membrane protein VDAC2. Upon starvation induction, SPATA33 is recruited to autophagosome by binding the autophagy machinery ATG16L1 via its N-terminal along with mitochondria. Notably, Spata33 knockout inhibited autophagy and overexpression can promote autophagosome formation for mitochondrial sequestration. Therefore, SPATA33 confers selectivity for mitochondrial degradation and promotes mitophagy in male germline cells.
  26. JCSM Rapid Commun. 2020 Jul-Dec;3(2):3(2): 44-55
      Background: Cancer cachexia is a multifactorial wasting syndrome that is characterized by the loss of skeletal muscle mass and weakness, which compromises physical function, reduces quality of life, and ultimately can lead to mortality. Experimental models of cancer cachexia have recapitulated this skeletal muscle atrophy and consequent decline in muscle force generating capacity. We address these issues in a novel transgenic mouse model Kras, Trp53 and Pdx-1-Cre (KPC) of pancreatic ductal adenocarcinoma (PDA) using multi-parametric magnetic resonance (mp-MR) measures.Methods: KPC mice (n = 10) were divided equally into two groups (n = 5/group) depending on the size of the tumor i.e. tumor size <250 mm3 and >250 mm3. Using mp-MR measures, we demonstrated the changes in the gastrocnemius muscle at the microstructural level. In addition, we evaluated skeletal muscle contractile function in KPC mice using an in vivo approach.
    Results: Increase in tumor size resulted in decrease in gastrocnemius maximum cross sectional area, decrease in T2 relaxation time, increase in magnetization transfer ratio, decrease in mean diffusivity, and decrease in radial diffusivity of water across the muscle fibers. Finally, we detected significant decrease in absolute and specific force production of gastrocnemius muscle with increase in tumor size.
    Conclusions: Our findings indicate that increase in tumor size may cause alterations in structural and functional parameters of skeletal muscles and that MR parameters may be used as sensitive biomarkers to noninvasively detect structural changes in cachectic muscles.
    Keywords:  Cachexia; Diffusion tensor imaging (DTI); Magnetic resonance imaging (MRI); Magnetization transfer ratio (MTR); Transverse relaxation time (T2)
  27. Pancreatology. 2020 Oct 16. pii: S1424-3903(20)30777-8. [Epub ahead of print]
      BACKGROUND: The identification of genetic risk factors for chronic pancreatitis, such as PRSS1, CFTR and SPINK1, provides the opportunity to define key pathologic hallmarks and etiologic-specific changes. For example, pancreata from PRSS1 and CFTR patients exhibit progressive lipomatous atrophy without significant fibrosis. Considering the pathology of SPINK1-associated pancreatitis is ill-defined, we examined the pancreata of SPINK1 patients with chronic pancreatitis.METHODS: Histologic sections after total pancreatectomy with islet autotransplantation and associated clinicopathologic data were collected from 28 patients with SPINK1 germline alterations. Clinical findings, germline data, anatomic anomalies and pathologic findings were descriptively evaluated.
    RESULTS: Patients ranged in age from 5 to 48 years (median, 21.6 years) with abdominal pain between 2 and 25 years (median, 5.8 years). Most patients were SPINK1 heterozygous and 14 (50%) had co-occurring CFTR (n = 12) and CTRC (n = 2) mutations. Other pancreatitis risk factors included anatomic anomalies (n = 9) and tobacco use (n = 1). Overall, 24 (86%) patients had additional pancreatitis-associated germline alterations, SPINK1 homozygosity, anatomic anomalies or environmental factors. Examination of pancreata revealed a sequential pattern of exocrine parenchymal loss and replacement by prominent fibrosis, dependent on the duration of abdominal pain. No malignancies were identified, but low-grade pancreatic intraepithelial neoplasia was present for 2 cases.
    CONCLUSIONS: Within this descriptive study, SPINK1-associated pancreatitis is characterized by parenchymal fibrosis and suggests divergent pathophysiologic mechanisms from PRSS1 and CFTR-associated pancreatitis. Moreover, SPINK1 patients frequently had additional etiologic factors that did not impact the development of pancreatic fibrosis and may implicate SPINK1 as a disease modifier gene.
    Keywords:  Alcohol; Fibrosis; Genetics; Pancreatitis; Pathology
  28. Cell Mol Gastroenterol Hepatol. 2020 Oct 17. pii: S2352-345X(20)30171-5. [Epub ahead of print]
      BACKGROUND & AIMS: Maintaining endoplasmic reticulum (ER) proteostasis is essential for pancreatic acinar cell function. Under conditions of severe ER stress, activation of pathogenic unfolded protein response pathways plays a central role in the development and progression of pancreatitis. Less is known, however, of the consequence of perturbing ER-associated post-translational protein modifications on pancreatic outcomes. Here, we examined the role of the ER acetyl-CoA transporter AT-1 on pancreatic homeostasis.METHODS: We utilized an AT-1S113R/+ hypomorphic mouse model, and generated an inducible, acinar-specific AT-1 knockout mouse model, and performed histological and biochemical analyses to probe the effect of AT-1 loss on acinar cell physiology.
    RESULTS: We found that AT-1 expression is significantly downregulated during both acute and chronic pancreatitis. Furthermore, acinar-specific deletion of AT-1 in acinar cells induces chronic ER stress marked by activation of both the XBP1s and PERK pathways, leading to spontaneous mild/moderate chronic pancreatitis evidenced by accumulation of intracellular trypsin, immune cell infiltration, and fibrosis. Induction of acute on chronic pancreatitis in the AT-1 model led to acinar cell loss and glad atrophy.
    CONCLUSIONS: These results indicate a key role for AT-1 in pancreatic acinar cell homeostasis, the unfolded protein response (UPR), and that perturbations in AT-1 function leads to pancreatic disease.
    Keywords:  AT-1; ER stress; unfolded protein response
  29. J Pathol. 2020 Oct 20.
      Cystic neoplasms of the pancreas are an increasingly important public health problem. The majority of these lesions are benign but some progress to invasive pancreatic ductal adenocarcinoma (PDAC). There is a dearth of mouse models of these conditions. The orphan nuclear receptor NR5A2 regulates development, differentiation, and inflammation. Germline Nr5a2 heterozygosity sensitizes mice to the oncogenic effects of mutant Kras in the pancreas. Here, we show that - unlike constitutive Nr5a2+/- mice - conditional Nr5a2 heterozygosity in pancreatic epithelial cells, combined with mutant Kras, (KPN+/- ) leads to a dramatic replacement of the pancreatic parenchyma with cystic structures and an accelerated development of high grade PanINs and PDAC. Timed histopathological analyses indicated that in KPN+/- mice PanINs precede the formation of cystic lesions and the latter precede PDAC. A single episode of acute caerulein pancreatitis is sufficient to accelerate the development of cystic lesions in KPN+/- mice. Epithelial cells of cystic lesions of KPN+/- mice express MUC1, MUC5AC, and MUC6 but lack expression of MUC2, CDX2 and acinar markers, indicative of a pancreato-biliary/gastric phenotype. In accordance with this, in human samples we found a non-significantly decreased expression of NR5A2 in mucinous tumours, compared with conventional PDAC. These results highlight that the effects of loss of one Nr5a2 allele are time- and cell context-dependent. KPN+/- mice represent a new model to study the formation of cystic pancreatic lesions and their relationship with PanINs and classical PDAC. Our findings suggest that pancreatitis could also contribute to acceleration of cystic tumour progression in patients. This article is protected by copyright. All rights reserved.
    Keywords:  KRAS; NR5A2; cystic neoplasms; genetic mouse models; haploinsufficiency; orphan receptors; pancreas
  30. Nat Commun. 2020 10 20. 11(1): 5288
      Telomerase is a specialized reverse transcriptase that adds GGTTAG repeats to chromosome ends and is upregulated in most human cancers to enable limitless proliferation. Here, we uncover two distinct mechanisms by which naturally occurring oxidized dNTPs and therapeutic dNTPs inhibit telomerase-mediated telomere elongation. We conduct a series of direct telomerase extension assays in the presence of modified dNTPs on various telomeric substrates. We provide direct evidence that telomerase can add the nucleotide reverse transcriptase inhibitors ddITP and AZT-TP to the telomeric end, causing chain termination. In contrast, telomerase continues elongation after inserting oxidized 2-OH-dATP or therapeutic 6-thio-dGTP, but insertion disrupts translocation and inhibits further repeat addition. Kinetics reveal that telomerase poorly selects against 6-thio-dGTP, inserting with similar catalytic efficiency as dGTP. Furthermore, telomerase processivity factor POT1-TPP1 fails to restore processive elongation in the presence of inhibitory dNTPs. These findings reveal mechanisms for targeting telomerase with modified dNTPs in cancer therapy.
  31. Clin Cancer Res. 2020 Oct 22. pii: clincanres.2475.2020. [Epub ahead of print]
      PURPOSE: A subset of pancreatic ductal adenocarcinomas (PDACs) is highly resistant to systemic chemotherapy, but no markers are available in clinical settings to identify this subset. We hypothesized that a glycan biomarker for PDAC called sTRA could be used for this purpose.EXPERIMENTAL DESIGN: We tested for differences between PDACs classified by glycan expression in multiple systems: sets of cell lines, organoids, and isogenic cell lines; primary tumors; and blood plasma from human subjects.
    RESULTS: The sTRA-expressing models tended to have stem-like gene expression and the capacity for mesenchymal differentiation, in contrast to the non-expressing models. The sTRA cell lines also had significantly increased resistance to seven different chemotherapeutics commonly used against pancreatic cancer. Patients with primary tumors that were positive for a gene-expression classifier for sTRA received no statistically significant benefit from adjuvant chemotherapy, in contrast to those negative for the signature. In another cohort, based on direct measurements of sTRA in tissue microarrays, the patients who were high in sTRA again had no statistically significant benefit from adjuvant chemotherapy. Furthermore, a blood-plasma test for the sTRA glycan identified the PDACs that showed rapid relapse following neoadjuvant chemotherapy.
    CONCLUSIONS: This research demonstrates that a glycan biomarker could have value to detect chemotherapy-resistant PDAC in clinical settings. This capability could aid in the development of stratified treatment plans and facilitate biomarker-guided trials targeting resistant PDAC.
  32. Nat Microbiol. 2020 Oct 19.
      Sepsis is the most common cause of death for patients in intensive care worldwide due to a dysregulated host response to infection. Here, we investigate the role of sequestosome-1 (SQSTM1/p62), an autophagy receptor that functions as a regulator of innate immunity, in sepsis. We find that lipopolysaccharide elicits gasdermin D-dependent pyroptosis to enable passive SQSTM1 release from macrophages and monocytes, whereas transmembrane protein 173-dependent TANK-binding kinase 1 activation results in the phosphorylation of SQSTM1 at Ser403 and subsequent SQSTM1 secretion from macrophages and monocytes. Moreover, extracellular SQSTM1 binds to insulin receptor, which in turn activates a nuclear factor kappa B-dependent metabolic pathway, leading to aerobic glycolysis and polarization of macrophages. Intraperitoneal injection of anti-SQSTM1-neutralizing monoclonal antibodies or conditional depletion of Insr in myeloid cells using the Cre-loxP system protects mice from lethal sepsis (caecal ligation and puncture or infection by Escherichia coli or Streptococcus pneumoniae) and endotoxaemia. We also report that circulating SQSTM1 and the messenger RNA expression levels of SQSTM1 and INSR in peripheral blood mononuclear cells are related to the severity of sepsis in 40 patients. Thus, extracellular SQSTM1 has a pathological role in sepsis and could be targeted to develop therapies for sepsis.
  33. Nat Cancer. 2020 Oct;1(10): 976-989
      Oxidative phosphorylation (OXPHOS) defects caused by somatic mitochondrial DNA (mtDNA) mutations increase with age in human colorectal epithelium and are prevalent in colorectal tumours, but whether they actively contribute to tumorigenesis remains unknown. Here we demonstrate that mtDNA mutations causing OXPHOS defects are enriched during the human adenoma/carcinoma sequence, suggesting they may confer a metabolic advantage. To test this we deleted the tumour suppressor Apc in OXPHOS deficient intestinal stem cells in mice. The resulting tumours were larger than in control mice due to accelerated cell proliferation and reduced apoptosis. We show that both normal crypts and tumours undergo metabolic remodelling in response to OXPHOS deficiency by upregulating the de novo serine synthesis pathway (SSP). Moreover, normal human colonic crypts upregulate the SSP in response to OXPHOS deficiency prior to tumorigenesis. Our data show that age-associated OXPHOS deficiency causes metabolic remodelling that can functionally contribute to accelerated intestinal cancer development.
  34. iScience. 2020 Sep 25. 23(9): 101531
      Similarities between microbial and cancer cells were noticed in recent years and serve as a basis for an atavism theory of cancer. Cancer cells would rely on the reactivation of an ancestral "genetic program" that would have been repressed in metazoan cells. Here we argue that cancer cells resemble unicellular organisms mainly in their similar way to exploit cellular stochasticity to produce cell specialization and maximize proliferation. Indeed, the relationship between low stochasticity, specialization, and quiescence found in normal differentiated metazoan cells is lost in cancer. On the contrary, low stochasticity and specialization are associated with high proliferation among cancer cells, as it is observed for the "specialist" cells in microbial populations that fully exploit nutritional resources to maximize proliferation. Thus, we propose a model where the appearance of cancer phenotypes can be solely due to an adaptation and a speciation process based on initial increase in cellular stochasticity.
    Keywords:  Cancer; Ecology; Evolutionary Biology
  35. Br J Cancer. 2020 Oct 19.
      An urgent medical need to develop novel treatment strategies for patients with pancreatic ductal adenocarcinoma (PDAC) exists. However, despite various efforts in the histopathological and molecular subtyping of PDAC, novel targeted or specific therapies have not been established. Posttranslational modifications (PTMs) with ubiquitin-like proteins, including small ubiquitin-like modifiers (SUMOs), mediate numerous processes that can contribute to the fitness and survival of cancer cells. The contribution of SUMOylation to transcriptional control, DNA repair pathways, mitotic progression, and oncogenic signalling has been described. Here we review functions of the SUMO pathway in PDAC, with a special focus on its connection to an aggressive subtype of the disease characterised by high MYC activity, and discuss SUMOylation inhibitors under development for precise PDAC therapies.
  36. Aging (Albany NY). 2020 Oct 18. 12
      Evidence from clinical trials and observational studies suggests that both progressive resistance exercise training (PRT) and metformin delay a variety of age-related morbidities. Previously, we completed a clinical trial testing the effects of 14 weeks of PRT + metformin (metPRT) compared to PRT with placebo (plaPRT) on muscle hypertrophy in older adults. We found that metformin blunted PRT-induced muscle hypertrophic response. To understand potential mechanisms underlying the inhibitory effect of metformin on PRT, we analyzed the muscle transcriptome in 23 metPRT and 24 plaPRT participants. PRT significantly increased expression of genes involved in extracellular matrix remodeling pathways, and downregulated RNA processing pathways in both groups, however, metformin attenuated the number of differentially expressed genes within these pathways compared to plaPRT. Pathway analysis showed that genes unique to metPRT modulated aging-relevant pathways, such as cellular senescence and autophagy. Differentially expressed genes from baseline biopsies in older adults compared to resting muscle from young volunteers were reduced following PRT in plaPRT and were further reduced in metPRT. We suggest that although metformin may blunt pathways induced by PRT to promote muscle hypertrophy, adjunctive metformin during PRT may have beneficial effects on aging-associated pathways in muscle from older adults.
    Keywords:  aging; exercise-drug interaction; gene expression; metformin; strength training
  37. Trends Genet. 2020 Oct 19. pii: S0168-9525(20)30270-5. [Epub ahead of print]
      It is recognized that cell metabolism is tightly connected to other cellular processes such as regulation of gene expression. Metabolic pathways not only provide the precursor molecules necessary for gene expression, but they also provide ATP, the primary fuel driving gene expression. However, metabolic conditions are highly variable since nutrient uptake is not a uniform process. Thus, cells must continually calibrate gene expression to their changing metabolite and energy budgets. This review discusses recent advances in understanding the molecular and biophysical mechanisms that connect metabolism and gene regulation as cells navigate their growth, proliferation, and differentiation. Particular focus is given to these mechanisms in the context of organismal development.
    Keywords:  ATP; gene regulation; glucose metabolism
  38. Nat Rev Mol Cell Biol. 2020 Oct 22.
      Mitochondria contain about 1,000-1,500 proteins that fulfil multiple functions. Mitochondrial proteins originate from two genomes: mitochondrial and nuclear. Hence, proper mitochondrial function requires synchronization of gene expression in the nucleus and in mitochondria and necessitates efficient import of mitochondrial proteins into the organelle from the cytosol. Furthermore, the mitochondrial proteome displays high plasticity to allow the adaptation of mitochondrial function to cellular requirements. Maintenance of this complex and adaptable mitochondrial proteome is challenging, but is of crucial importance to cell function. Defects in mitochondrial proteostasis lead to proteotoxic insults and eventually cell death. Different quality control systems monitor the mitochondrial proteome. The cytosolic ubiquitin-proteasome system controls protein transport across the mitochondrial outer membrane and removes damaged or mislocalized proteins. Concomitantly, a number of mitochondrial chaperones and proteases govern protein folding and degrade damaged proteins inside mitochondria. The quality control factors also regulate processing and turnover of native proteins to control protein import, mitochondrial metabolism, signalling cascades, mitochondrial dynamics and lipid biogenesis, further ensuring proper function of mitochondria. Thus, mitochondrial protein quality control mechanisms are of pivotal importance to integrate mitochondria into the cellular environment.
  39. Nat Rev Mol Cell Biol. 2020 Oct 22.
      Cell-cell interfaces are found throughout multicellular organisms, from transient interactions between motile immune cells to long-lived cell-cell contacts in epithelia. Studies of immune cell interactions, epithelial cell barriers, neuronal contacts and sites of cell-cell fusion have identified a core set of features shared by cell-cell interfaces that critically control their function. Data from diverse cell types also show that cells actively and passively regulate the localization, strength, duration and cytoskeletal coupling of receptor interactions governing cell-cell signalling and physical connections between cells, indicating that cell-cell interfaces have a unique membrane organization that emerges from local molecular and cellular mechanics. In this Review, we discuss recent findings that support the emerging view of cell-cell interfaces as specialized compartments that biophysically constrain the arrangement and activity of their protein, lipid and glycan components. We also review how these biophysical features of cell-cell interfaces allow cells to respond with high selectivity and sensitivity to multiple inputs, serving as the basis for wide-ranging cellular functions. Finally, we consider how the unique properties of cell-cell interfaces present opportunities for therapeutic intervention.
  40. Nat Rev Cancer. 2020 Oct 21.
      2-Oxoglutarate-dependent dioxygenases (2OGDDs) are a superfamily of enzymes that play diverse roles in many biological processes, including regulation of hypoxia-inducible factor-mediated adaptation to hypoxia, extracellular matrix formation, epigenetic regulation of gene transcription and the reprogramming of cellular metabolism. 2OGDDs all require oxygen, reduced iron and 2-oxoglutarate (also known as α-ketoglutarate) to function, although their affinities for each of these co-substrates, and hence their sensitivity to depletion of specific co-substrates, varies widely. Numerous 2OGDDs are recurrently dysregulated in cancer. Moreover, cancer-specific metabolic changes, such as those that occur subsequent to mutations in the genes encoding succinate dehydrogenase, fumarate hydratase or isocitrate dehydrogenase, can dysregulate specific 2OGDDs. This latter observation suggests that the role of 2OGDDs in cancer extends beyond cancers that harbour mutations in the genes encoding members of the 2OGDD superfamily. Herein, we review the regulation of 2OGDDs in normal cells and how that regulation is corrupted in cancer.
  41. J Cell Physiol. 2020 Oct 20.
      Genome instability in cancer drives tumor heterogeneity, undermines the success of therapies, and leads to metastasis and recurrence. Condensins are conserved chromatin-binding proteins that promote genomic stability, mainly by ensuring proper condensation of chromatin and mitotic chromosome segregation. Condensin mutations are found in human tumors, but it is not known how or even if such mutations promote cancer progression. In this study, we focus on condensin II subunit CAPH2 and specific CAPH2 mutations reported to be enriched in human cancer patients, and we test how CAPH2 cancer-specific mutations may lead to condensin II complex dysfunction and contribute to genome instability. We find that R551P, R551S, and S556F mutations in CAPH2 cause genomic instability by causing DNA damage, anaphase defects, micronuclei, and chromosomal instability. DNA damage and anaphase defects are caused primarily by ataxia telangiectasia and Rad3-related-dependent telomere dysfunction, as anaphase bridges are enriched for telomeric repeat sequences. We also show that these mutations decrease the binding of CAPH2 to the ATPase subunit SMC4 as well as the rest of the condensin II complex, and decrease the amount of CAPH2 protein bound to chromatin. Thus, in vivo the R551P, R551S, and S556F cancer-specific CAPH2 mutant proteins are likely to impair condensin II complex formation, impede condensin II activity during mitosis and interphase, and promote genetic heterogeneity in cell populations that can lead to clonal outgrowth of cancer cells with highly diverse genotypes.
    Keywords:  DNA damage; anaphase bridge; condensin; genome instability; telomere
  42. Aging Cell. 2020 Aug;19(8): e13192
      The aged systemic milieu promotes cellular and cognitive impairments in the hippocampus. Here, we report that aging of the hematopoietic system directly contributes to the pro-aging effects of old blood on cognition. Using a heterochronic hematopoietic stem cell (HSC) transplantation model (in which the blood of young mice is reconstituted with old HSCs), we find that exposure to an old hematopoietic system inhibits hippocampal neurogenesis, decreases synaptic marker expression, and impairs cognition. We identify a number of factors elevated in the blood of young mice reconstituted with old HSCs, of which cyclophilin A (CyPA) acts as a pro-aging factor. Increased systemic levels of CyPA impair cognition in young mice, while inhibition of CyPA in aged mice improves cognition. Together, these data identify age-related changes in the hematopoietic system as drivers of hippocampal aging.
    Keywords:  aging; cognition; cyclophilin A; hematopoietic system; hippocampus
  43. Nat Commun. 2020 10 19. 11(1): 5270
      Pancreatic cancer is often detected late, when curative therapies are no longer possible. Here, we present non-invasive detection of pancreatic ductal adenocarcinoma (PDAC) by 5-hydroxymethylcytosine (5hmC) changes in circulating cell free DNA from a PDAC cohort (n = 64) in comparison with a non-cancer cohort (n = 243). Differential hydroxymethylation is found in thousands of genes, most significantly in genes related to pancreas development or function (GATA4, GATA6, PROX1, ONECUT1, MEIS2), and cancer pathogenesis (YAP1, TEAD1, PROX1, IGF1). cfDNA hydroxymethylome in PDAC cohort is differentially enriched for genes that are commonly de-regulated in PDAC tumors upon activation of KRAS and inactivation of TP53. Regularized regression models built using 5hmC densities in genes perform with AUC of 0.92 (discovery dataset, n = 79) and 0.92-0.94 (two independent test sets, n = 228). Furthermore, tissue-derived 5hmC features can be used to classify PDAC cfDNA (AUC = 0.88). These findings suggest that 5hmC changes enable classification of PDAC even during early stage disease.
  44. J Cachexia Sarcopenia Muscle. 2020 Oct 08.
      BACKGROUND: Cancer cachexia (CCx) is a multifactorial energy-wasting syndrome reducing the efficiency of anti-cancer therapies, quality of life, and survival of cancer patients. In the past years, most studies focused on the identification of tumour and host-derived proteins contributing to CCx. However, there is still a lack of studies addressing the changes in bioactive lipids. The aim of this study was to identify specific lipid species as a hallmark of CCx by performing a broad range lipid analysis of plasma from well-established CCx mouse models as well as cachectic and weight stable cancer patients.METHODS: Plasma from non-cachectic (PBS-injected mice, NC26 tumour-bearing mice), pre-cachectic and cachectic mice (C26 and LLC tumour-bearing mice, ApcMin/+ mutant mice), and plasma from weight stable and cachectic patients with gastrointestinal cancer, were analysed using the Lipidyzer™ platform. In total, 13 lipid classes and more than 1100 lipid species, including sphingolipids, neutral and polar glycerolipids, were covered by the analysis. Correlation analysis between specific lipid species and readouts of CCx were performed. Lipidomics data were confirmed by gene expression analysis of metabolic organs to analyse enzymes involved in sphingolipid synthesis and degradation.
    RESULTS: A decrease in several lysophosphatidylcholine (LPC) species and an increase in numerous sphingolipids including sphingomyelins (SMs), ceramides (CERs), hexosyl-ceramides (HCERs) and lactosyl-ceramides (LCERs), were mutual features of CCx in both mice and cancer patients. Notably, sphingolipid levels gradually increased during cachexia development. Key enzymes involved in ceramide synthesis were elevated in liver but not in adipose, muscle, or tumour tissues, suggesting that ceramide turnover in the liver is a major contributor to elevated sphingolipid levels in CCx. LPC(16:1), LPC(20:3), SM(16:0), SM(24:1), CER(16:0), CER(24:1), HCER(16:0), and HCER(24:1) were the most consistently affected lipid species between mice and humans and correlated negatively (LPCs) or positively (SMs, CERs and HCERs) with the severity of body weight loss.
    CONCLUSIONS: High levels of sphingolipids, specifically ceramides and modified ceramides, are a defining feature of murine and human CCx and may contribute to tissue wasting and skeletal muscle atrophy through the inhibition of anabolic signals. The progressive increase in sphingolipids during cachexia development supports their potential as early biomarkers for CCx.
    Keywords:  Cancer cachexia; Ceramides; Lipidomics; Signalling lipids; Sphingolipids
  45. Cells. 2020 10 16. pii: E2308. [Epub ahead of print]9(10):
      Aberrant metabolism is a major hallmark of cancer. Abnormal cancer metabolism, such as aerobic glycolysis and increased anabolic pathways, has important roles in tumorigenesis, metastasis, drug resistance, and cancer stem cells. Well-known oncogenic signaling pathways, such as phosphoinositide 3-kinase (PI3K)/AKT, Myc, and Hippo pathway, mediate metabolic gene expression and increase metabolic enzyme activities. Vice versa, deregulated metabolic pathways contribute to defects in cellular signal transduction pathways, which in turn provide energy, building blocks, and redox potentials for unrestrained cancer cell proliferation. Studies and clinical trials are being performed that focus on the inhibition of metabolic enzymes by small molecules or dietary interventions (e.g., fasting, calorie restriction, and intermittent fasting). Similar to genetic heterogeneity, the metabolic phenotypes of cancers are highly heterogeneous. This heterogeneity results from diverse cues in the tumor microenvironment and genetic mutations. Hence, overcoming metabolic plasticity is an important goal of modern cancer therapeutics. This review highlights recent findings on the metabolic phenotypes of cancer and elucidates the interactions between signal transduction pathways and metabolic pathways. We also provide novel rationales for designing the next-generation cancer metabolism drugs.
    Keywords:  Cancer metabolism; cell signaling; drug development; metabolic plasticity
  46. Nat Cell Biol. 2020 Oct 19.
      Tumour growth and invasiveness require extracellular matrix (ECM) degradation and are stimulated by the GALA pathway, which induces protein O-glycosylation in the endoplasmic reticulum (ER). ECM degradation requires metalloproteases, but whether other enzymes are required is unclear. Here, we show that GALA induces the glycosylation of the ER-resident calnexin (Cnx) in breast and liver cancer. Glycosylated Cnx and its partner ERp57 are trafficked to invadosomes, which are sites of ECM degradation. We find that disulfide bridges are abundant in connective and liver ECM. Cell surface Cnx-ERp57 complexes reduce these extracellular disulfide bonds and are essential for ECM degradation. In vivo, liver cancer cells but not hepatocytes display cell surface Cnx. Liver tumour growth and lung metastasis of breast and liver cancer cells are inhibited by anti-Cnx antibodies. These findings uncover a moonlighting function of Cnx-ERp57 at the cell surface that is essential for ECM breakdown and tumour development.
  47. J Cachexia Sarcopenia Muscle. 2020 Oct 19.
      BACKGROUND: Neurofibromatosis type 1 (NF1) is a multi-organ disease caused by mutations in neurofibromin 1 (NF1). Amongst other features, NF1 patients frequently show reduced muscle mass and strength, impairing patients' mobility and increasing the risk of fall. The role of Nf1 in muscle and the cause for the NF1-associated myopathy are mostly unknown.METHODS: To dissect the function of Nf1 in muscle, we created muscle-specific knockout mouse models for NF1, inactivating Nf1 in the prenatal myogenic lineage either under the Lbx1 promoter or under the Myf5 promoter. Mice were analysed during prenatal and postnatal myogenesis and muscle growth.
    RESULTS: Nf1Lbx1 and Nf1Myf5 animals showed only mild defects in prenatal myogenesis. Nf1Lbx1 animals were perinatally lethal, while Nf1Myf5 animals survived only up to approximately 25 weeks. A comprehensive phenotypic characterization of Nf1Myf5 animals showed decreased postnatal growth, reduced muscle size, and fast fibre atrophy. Proteome and transcriptome analyses of muscle tissue indicated decreased protein synthesis and increased proteasomal degradation, and decreased glycolytic and increased oxidative activity in muscle tissue. High-resolution respirometry confirmed enhanced oxidative metabolism in Nf1Myf5 muscles, which was concomitant to a fibre type shift from type 2B to type 2A and type 1. Moreover, Nf1Myf5 muscles showed hallmarks of decreased activation of mTORC1 and increased expression of atrogenes. Remarkably, loss of Nf1 promoted a robust activation of AMPK with a gene expression profile indicative of increased fatty acid catabolism. Additionally, we observed a strong induction of genes encoding catabolic cytokines in muscle Nf1Myf5 animals, in line with a drastic reduction of white, but not brown adipose tissue.
    CONCLUSIONS: Our results demonstrate a cell autonomous role for Nf1 in myogenic cells during postnatal muscle growth required for metabolic and proteostatic homeostasis. Furthermore, Nf1 deficiency in muscle drives cross-tissue communication and mobilization of lipid reserves.
    Keywords:  AMPK; Muscle atrophy; Muscle fibre type; Muscle metabolism; Myopathy; Neurofibromatosis / NF1
  48. Cancer Sci. 2020 Oct 18.
      Recent studies of the cancer genome have identified numerous patients harboring multiple mutations (MMs) within individual oncogenes. These MMs (de novo MMs) in cis synergistically activate the mutated oncogene and promote tumorigenesis, indicating a positive epistatic interaction between mutations. The relatively frequent de novo MMs suggest that intramolecular positive epistasis is widespread in oncogenes. Studies also suggest that negative and higher-order epistasis affects de novo MMs. Comparison of de novo MMs and MMs associated with drug-resistant secondary mutations (secondary MMs) revealed several similarities with respect to allelic configuration, mutational selection and functionality of individual mutations; these two types of MMs may have shared molecular mechanisms. Conversely, they have several differences, most notably the difference in drug sensitivities. Secondary MMs usually confer resistance to molecularly targeted therapies, whereas several de novo MMs are associated with increased sensitivity, implying that both can be useful as therapeutic biomarkers. Unlike secondary MMs in which specific secondary resistant mutations are selected, minor (infrequent) functionally weak mutations are convergently selected in de novo MMs, which may provide an explanation as to why such mutations accumulate in cancer. The third type of MM is MMs from different subclones. This type of MM is associated with parallel evolution, which may contribute to relapse and treatment failure. Collectively, MMs within individual oncogenes are diverse, but all types of MMs are associated with cancer evolution and therapeutic response. Further evaluation of oncogenic MMs is warranted to gain a deeper understanding of cancer genetics and evolution.
    Keywords:  drug sensitivity; epistasis; multiple mutations (MMs); precision medicine; synergy
  49. Aging Cell. 2020 Oct 20. e13253
      The biological bases of longevity are not well understood, and there are limited biomarkers for the prediction of long life. We used a high-throughput, discovery-based proteomics approach to identify serum peptides and proteins that were associated with the attainment of longevity in a longitudinal study of community-dwelling men age ≥65 years. Baseline serum in 1196 men were analyzed using liquid chromatography-ion mobility-mass spectrometry, and lifespan was determined during ~12 years of follow-up. Men who achieved longevity (≥90% expected survival) were compared to those who died earlier. Rigorous statistical methods that controlled for false positivity were utilized to identify 25 proteins that were associated with longevity. All these proteins were in lower abundance in long-lived men and included a variety involved in inflammation or complement activation. Lower levels of longevity-associated proteins were also associated with better health status, but as time to death shortened, levels of these proteins increased. Pathway analyses implicated a number of compounds as important upstream regulators of the proteins and implicated shared networks that underlie the observed associations with longevity. Overall, these results suggest that complex pathways, prominently including inflammation, are linked to the likelihood of attaining longevity. This work may serve to identify novel biomarkers for longevity and to understand the biology underlying lifespan.
    Keywords:  aging; biomarker; inflammation; longevity; men; proteomics
  50. Nat Cell Biol. 2020 Oct 19.
      Mutant KRAS modulates the metabolic plasticity of cancer cells to confer a growth advantage during hypoxia, but the molecular underpinnings are largely unknown. Using a lipidomic screen, we found that PLCγ1 is suppressed during hypoxia in KRAS-mutant human lung adenocarcinoma cancer cell lines. Suppression of PLCγ1 in hypoxia promotes a less oxidative cancer cell metabolism state, reduces the formation of mitochondrial reactive oxygen species and switches tumour bioenergetics towards glycolysis by impairing Ca2+ entry into the mitochondria. This event prevents lipid peroxidation, antagonizes apoptosis and increases cancer cell proliferation. Accordingly, loss of function of Plcg1 in a mouse model of KrasG12D-driven lung adenocarcinoma increased the expression of glycolytic genes, boosted tumour growth and reduced survival. In patients with KRAS-mutant lung adenocarcinomas, low PLCγ1 expression correlates with increased expression of hypoxia markers and predicts poor patient survival. Thus, our work reveals a mechanism of cancer cell adaptation to hypoxia with potential therapeutic value.
  51. Rev Physiol Biochem Pharmacol. 2020 Oct 17.
      Lipid droplets have a unique structure among organelles consisting of a dense hydrophobic core of neutral lipids surrounded by a single layer of phospholipids decorated with various proteins. Often labeled merely as passive fat storage repositories, they in fact have a remarkably dynamic life cycle. Being formed within the endoplasmic reticulum membrane, lipid droplets rapidly grow, shrink, traverse the cytosol, and engage in contacts with other organelles to exchange proteins and lipids. Their lipid and protein composition changes dynamically in response to cellular states and nutrient availability. Remarkably, their biogenesis is induced when cells experience various forms of nutrient, energy, and redox imbalances, including lipid excess and complete nutrient deprivation. Cancer cells are continuously exposed to nutrient and oxygen fluctuations and have the capacity to switch between alternative nutrient acquisition and metabolic pathways in order to strive even during severe stress. Their supply of lipids is ensured by a series of nutrient uptake and scavenging mechanisms, upregulation of de novo lipid synthesis, repurposing of their structural lipids via enzymatic remodeling, or lipid recycling through autophagy. Importantly, most of these pathways of lipid acquisition converge at lipid droplets, which combine different lipid fluxes and control their usage based on specific cellular needs. It is thus not surprising that lipid droplet breakdown is an elaborately regulated process that occurs via a complex interplay of neutral lipases and autophagic degradation. Cancer cells employ lipid droplets to ensure energy production and redox balance, modulate autophagy, drive membrane synthesis, and control its composition, thereby minimizing stress and fostering tumor progression. As regulators of (poly)unsaturated fatty acid trafficking, lipid droplets are also emerging as modulators of lipid peroxidation and sensitivity to ferroptosis. Clearly, dysregulated lipid droplet turnover may also be detrimental to cancer cells, which should provide potential therapeutic opportunities in the future. In this review, we explore how lipid droplets consolidate lipid acquisition and trafficking pathways in order to match lipid supply with the requirements for cancer cell survival, growth, and metastasis.
    Keywords:  Autophagy; Cancer; Fatty acid; Ferroptosis; Lipid droplets; Metabolism; Stress
  52. Sci Adv. 2020 Oct;pii: eaaz4452. [Epub ahead of print]6(43):
      Heat shock factor-1 (HSF-1) is a master regulator of stress responses across taxa. Overexpression of HSF-1 or genetic ablation of its conserved negative regulator, heat shock factor binding protein 1 (HSB-1), results in robust life-span extension in Caenorhabditis elegans Here, we found that increased HSF-1 activity elevates histone H4 levels in somatic tissues during development, while knockdown of H4 completely suppresses HSF-1-mediated longevity. Moreover, overexpression of H4 is sufficient to extend life span. Ablation of HSB-1 induces an H4-dependent increase in micrococcal nuclease protection of both nuclear chromatin and mitochondrial DNA (mtDNA), which consequently results in reduced transcription of mtDNA-encoded complex IV genes, decreased respiratory capacity, and a mitochondrial unfolded protein response-dependent life-span extension. Collectively, our findings reveal a previously unknown role of HSB-1/HSF-1 signaling in modulation of mitochondrial function via mediating histone H4-dependent regulation of mtDNA gene expression and concomitantly acting as a determinant of organismal longevity.
  53. Ann Surg. 2020 Oct 19.
      OBJECTIVE: To describe PNI and to evaluate its impact on disease-free (DFS) and overall survival (OS) in patients with resected pancreatic ductal adenocarcinoma (PDAC).SUMMARY OF BACKGROUND DATA: Although PNI is a prognostic factor for survival in many GI cancers, there is limited knowledge regarding its impact on tumor recurrence, especially in "early stage disease" (PDAC ≤20 mm, R0/N0 PDAC).
    METHODS: This multicenter retrospective study included patients undergoing PDAC resection between 2009 and 2014. The association of PNI with DFS and OS was analyzed using Cox proportional-hazards models.
    RESULTS: PNI was found in 87% of 778 patients included in the study, with lower rates in PDAC ≤20 mm (78.7%) and in R0/N0 tumors (70.6%). PNI rate did not differ between patients who underwent neoadjuvant therapy and upfront surgery (88% vs 84%, P = 0.08). Although not significant at multivariate analysis (P = 0.07), patients with PNI had worse DFS at univariate analysis (median DFS: 20 vs 15 months, P < 0.01). PNI was the only independent predictor of DFS in R0/N0 tumors (hazard ratio [HR]: 2.2) and in PDAC ≤20 mm (HR: 1.8). PNI was an independent predictor of OS in the entire cohort (27 vs 50 months, P = 0.01), together with G3 tumors, pN1 status, carbohydrate antigen (CA) 19.9 >37 and pain.
    CONCLUSIONS: PNI represents a major determinant of tumor recurrence and patients' survival in pancreatic cancer. The role of PNI is particularly relevant in early stages, supporting the hypothesis that invasion of nerves by cancer cells has a driving role in pancreatic cancer progression.
  54. Clin Cancer Res. 2020 Oct 21. pii: clincanres.1422.2020. [Epub ahead of print]
      PURPOSE: Concurrent gemcitabine and nab-paclitaxel treatment is one of the preferred chemotherapy regimens for metastatic and locally-advanced pancreatic ductal adenocarcinoma (PDAC). Previous studies demonstrate that caveolin-1 (Cav-1) expression is critical for nab-paclitaxel uptake into tumors and correlates with response. Gemcitabine increases nab-paclitaxel uptake by increasing Cav-1 expression. Thus, we hypothesized that pre-treatment with gemcitabine would further enhance the sensitivity of PDAC to nab-paclitaxel by increasing Cav-1 expression and nab-paclitaxel uptake.EXPERIMENTAL DESIGN: We investigated the sensitivity of different gemcitabine and nab-paclitaxel treatment regimens in a panel of PDAC cell lines and orthotopic xenograft models. The sensitivity of different treatment regimens was compared to the standard concurrent treatment.
    RESULTS: Pre-treatment with gemcitabine before nab-paclitaxel increased Cav-1 and albumin uptake and significantly decreased proliferation and clonogenicity compared to concurrent treatment, which correlated with increased levels of apoptosis. Cav-1 silencing reduced the uptake of albumin and therapeutic advantage observed when cells were pre-treated with gemcitabine prior to nab-paclitaxel. Additionally, we observed that pre-treatment with gemcitabine resulted in partial synchronization of cells in the G2/M phase at the time of nab-paclitaxel treatment, providing another mechanism for the benefit of altered scheduling. In heterotopic and orthotopic xenograft models, the altered schedule of gemcitabine prior to nab-paclitaxel significantly delayed tumor growth compared to concurrent delivery without added toxicity.
    CONCLUSIONS: Pre-treatment with gemcitabine significantly increased nab-paclitaxel uptake and correlated with an increased treatment efficacy and survival benefit in preclinical models, compared to standard concurrent treatment. These results justify preclinical and clinical testing of this altered scheduling combination.
  55. Trends Cell Biol. 2020 Oct 19. pii: S0962-8924(20)30190-2. [Epub ahead of print]
      Cell fate determination requires faithful execution of gene expression programs, which are increasingly recognized to respond to metabolic inputs. In particular, the family of α-ketoglutarate (αKG)-dependent dioxygenases, which include several chromatin-modifying enzymes, are emerging as key mediators of metabolic control of cell fate. αKG-dependent dioxygenases consume the metabolite αKG (also known as 2-oxoglutarate) as an obligate cosubstrate and are inhibited by succinate, fumarate, and 2-hydroxyglutarate. Here, we review the role of these metabolites in the control of dioxygenase activity and cell fate programs. We discuss the biochemical and transcriptional mechanisms enabling these metabolites to control cell fate and review evidence that nutrient availability shapes tissue-specific fate programs via αKG-dependent dioxygenases.
    Keywords:  2-hydroxyglutarate; alpha-ketoglutarate; cell fate; chromatin modifications; succinate; αKG-dependent dioxygenases
  56. Elife. 2020 Oct 23. pii: e59996. [Epub ahead of print]9
      Exercise has a wide range of systemic effects. In animal models, repeated exertion reduces malignant tumor progression, and clinically, exercise can improve outcome for cancer patients. The etiology of the effects of exercise on tumor progression are unclear, as are the cellular actors involved. We show here that in mice, exercise-induced reduction in tumor growth is dependent on CD8+ T cells, and that metabolites produced in skeletal muscle and excreted into plasma at high levels during exertion in both mice and humans enhance the effector profile of CD8+ T-cells. We found that activated murine CD8+ T cells alter their central carbon metabolism in response to exertion in vivo, and that immune cells from trained mice are more potent antitumor effector cells when transferred into tumor-bearing untrained animals. These data demonstrate that CD8+ T cells are metabolically altered by exercise in a manner that acts to improve their antitumoral efficacy.
    Keywords:  cancer biology; exercise; human; immunology; immunotherapy; inflammation; metabolism; mouse
  57. Sci Adv. 2020 Oct;pii: eabe5310. [Epub ahead of print]6(43):
      The nicotinamide adenine dinucleotide (NAD+/NADH) pair is a cofactor in redox reactions and is particularly critical in mitochondria as it connects substrate oxidation by the tricarboxylic acid (TCA) cycle to adenosine triphosphate generation by the electron transport chain (ETC) and oxidative phosphorylation. While a mitochondrial NAD+ transporter has been identified in yeast, how NAD enters mitochondria in metazoans is unknown. Here, we mine gene essentiality data from human cell lines to identify MCART1 (SLC25A51) as coessential with ETC components. MCART1-null cells have large decreases in TCA cycle flux, mitochondrial respiration, ETC complex I activity, and mitochondrial levels of NAD+ and NADH. Isolated mitochondria from cells lacking or overexpressing MCART1 have greatly decreased or increased NAD uptake in vitro, respectively. Moreover, MCART1 and NDT1, a yeast mitochondrial NAD+ transporter, can functionally complement for each other. Thus, we propose that MCART1 is the long sought mitochondrial transporter for NAD in human cells.