bims-cagime Biomed News
on Cancer, aging and metabolism
Issue of 2022–11–20
28 papers selected by
Kıvanç Görgülü, Technical University of Munich



  1. Cell Rep Med. 2022 Nov 15. pii: S2666-3791(22)00374-3. [Epub ahead of print]3(11): 100815
      Over 90% of pancreatic cancers present mutations in KRAS, one of the most common oncogenic drivers overall. Currently, most KRAS mutant isoforms cannot be targeted directly. Moreover, targeting single RAS downstream effectors induces adaptive resistance mechanisms. We report here on the combined inhibition of SHP2, upstream of KRAS, using the allosteric inhibitor RMC-4550 and of ERK, downstream of KRAS, using LY3214996. This combination shows synergistic anti-cancer activity in vitro, superior disruption of the MAPK pathway, and increased apoptosis induction compared with single-agent treatments. In vivo, we demonstrate good tolerability and efficacy of the combination, with significant tumor regression in multiple pancreatic ductal adenocarcinoma (PDAC) mouse models. Finally, we show evidence that 18F-fluorodeoxyglucose (FDG) positron emission tomography (PET) can be used to assess early drug responses in animal models. Based on these results, we will investigate this drug combination in the SHP2 and ERK inhibition in pancreatic cancer (SHERPA; ClinicalTrials.gov: NCT04916236) clinical trial, enrolling patients with KRAS-mutant PDAC.
    Keywords:  ERK; Kras; MAPK; PDAC; SHP2; combination therapy; inhibitors; pancreatic cancer; preclinical models; targeted therapies
    DOI:  https://doi.org/10.1016/j.xcrm.2022.100815
  2. Mol Cancer Res. 2022 Nov 15. pii: MCR-22-0602. [Epub ahead of print]
      Cholesterol dependence is an essential characteristic of pancreatic ductal adenocarcinoma (PDAC). Cholesterol 25-hydroxylase (CH25H) catalyzes monooxygenation of cholesterol into 25-hydroxycholesterol, which is implicated in inhibiting cholesterol biosynthesis and in cholesterol depletion. Here we show that, within PDAC cells, accumulation of cholesterol was facilitated by the loss of CH25H. Methylation of the CH25H gene and decreased levels of CH25H expression occurred in human pancreatic cancers and was associated with poor prognosis. Knockout of Ch25h in mice accelerated progression of Kras-driven pancreatic intraepithelial neoplasia. Conversely, restoration of CH25H expression in human and mouse PDAC cells decreased their viability under conditions of cholesterol deficit, and decelerated tumor growth in immune competent hosts. Mechanistically, the loss of CH25H promoted autophagy resulting in downregulation of MHC-I and decreased CD8+ T cell tumor infiltration. Re-expression of CH25H in PDAC cells combined with immune checkpoint inhibitors notably inhibited tumor growth. We discuss additional benefits that PDAC cells might gain from inactivation of CH25H and the potential translational importance of these findings for therapeutic approaches to PDAC. Implications: Loss of CH25H by pancreatic cancer cells may stimulate tumor progression and interfere with immunotherapies.
    DOI:  https://doi.org/10.1158/1541-7786.MCR-22-0602
  3. Sci Adv. 2022 Nov 18. 8(46): eabq2733
      Adipogenesis is a tightly orchestrated multistep process wherein preadipocytes differentiate into adipocytes. The most studied aspect of adipogenesis is its transcriptional regulation through timely expression and silencing of a vast number of genes. However, whether turnover of key regulatory proteins per se controls adipogenesis remains largely understudied. Chaperone-mediated autophagy (CMA) is a selective form of lysosomal protein degradation that, in response to diverse cues, remodels the proteome for regulatory purposes. We report here the activation of CMA during adipocyte differentiation and show that CMA regulates adipogenesis at different steps through timely degradation of key regulatory signaling proteins and transcription factors that dictate proliferation, energetic adaptation, and signaling changes required for adipogenesis.
    DOI:  https://doi.org/10.1126/sciadv.abq2733
  4. Nat Metab. 2022 Nov 14.
      The tumour microenvironment possesses mechanisms that suppress anti-tumour immunity. Itaconate is a metabolite produced from the Krebs cycle intermediate cis-aconitate by the activity of immune-responsive gene 1 (IRG1). While it is known to be immune modulatory, the role of itaconate in anti-tumour immunity is unclear. Here, we demonstrate that myeloid-derived suppressor cells (MDSCs) secrete itaconate that can be taken up by CD8+ T cells and suppress their proliferation, cytokine production and cytolytic activity. Metabolite profiling, stable-isotope tracing and metabolite supplementation studies indicated that itaconate suppressed the biosynthesis of aspartate and serine/glycine in CD8+ T cells to attenuate their proliferation and function. Host deletion of Irg1 in female mice bearing allografted tumours resulted in decreased tumour growth, inhibited the immune-suppressive activities of MDSCs, promoted anti-tumour immunity of CD8+ T cells and enhanced the anti-tumour activity of anti-PD-1 antibody treatment. Furthermore, we found a significant negative correlation between IRG1 expression and response to PD-1 immune checkpoint blockade in patients with melanoma. Our findings not only reveal a previously unknown role of itaconate as an immune checkpoint metabolite secreted from MDSCs to suppress CD8+ T cells, but also establish IRG1 as a myeloid-selective target in immunometabolism whose inhibition promotes anti-tumour immunity and enhances the efficacy of immune checkpoint protein blockade.
    DOI:  https://doi.org/10.1038/s42255-022-00676-9
  5. J Cachexia Sarcopenia Muscle. 2022 Nov 17.
       BACKGROUND: Chronic mTORC1 activation in skeletal muscle is linked with age-associated loss of muscle mass and strength, known as sarcopenia. Genetic activation of mTORC1 by conditionally ablating mTORC1 upstream inhibitor TSC1 in skeletal muscle accelerates sarcopenia development in adult mice. Conversely, genetic suppression of mTORC1 downstream effectors of protein synthesis delays sarcopenia in natural aging mice. mTORC1 promotes protein synthesis by activating ribosomal protein S6 kinases (S6Ks) and inhibiting eIF4E-binding proteins (4EBPs). Whole-body knockout of S6K1 or muscle-specific over-expression of a 4EBP1 mutant transgene (4EBP1mt), which is resistant to mTORC1-mediated inhibition, ameliorates muscle loss with age and preserves muscle function by enhancing mitochondria activities, despite both transgenic mice showing retarded muscle growth at a young age. Why repression of mTORC1-mediated protein synthesis can mitigate progressive muscle atrophy and dysfunction with age remains unclear.
    METHODS: Mice with myofiber-specific knockout of TSC1 (TSC1mKO), in which mTORC1 is hyperactivated in fully differentiated myofibers, were used as a mouse model of sarcopenia. To elucidate the role of mTORC1-mediated protein synthesis in regulating muscle mass and physiology, we bred the 4EBP1mt transgene or S6k1 floxed mice into the TSC1mKO mouse background to generate 4EBP1mt-TSC1mKO or S6K1-TSC1mKO mice, respectively. Functional and molecular analyses were performed to assess their role in sarcopenia development.
    RESULTS: Here, we show that 4EBP1mt-TSC1mKO, but not S6K1-TSC1mKO, preserved muscle mass (36.7% increase compared with TSC1mKO, P < 0.001) and strength (36.8% increase compared with TSC1mKO, P < 0.01) at the level of control mice. Mechanistically, 4EBP1 activation suppressed aberrant protein synthesis (two-fold reduction compared with TSC1mKO, P < 0.05) and restored autophagy flux without relieving mTORC1-mediated inhibition of ULK1, an upstream activator of autophagosome initiation. We discovered a previously unidentified phenotype of lysosomal failure in TSC1mKO mouse muscle, in which the lysosomal defect was also conserved in the naturally aged mouse muscle, whereas 4EBP1 activation enhanced lysosomal protease activities to compensate for impaired autophagy induced by mTORC1 hyperactivity. Consequently, 4EBP1 activation relieved oxidative stress to prevent toxic aggregate accumulation (0.5-fold reduction compared with TSC1mKO, P < 0.05) in muscle and restored mitochondrial homeostasis and function.
    CONCLUSIONS: We identify 4EBP1 as a communication hub coordinating protein synthesis and degradation to protect proteostasis, revealing therapeutic potential for activating lysosomal degradation to mitigate sarcopenia.
    Keywords:  mRNA translation; mTORC1; mitochondrial dysfunction; protein degradation; sarcopenia
    DOI:  https://doi.org/10.1002/jcsm.13121
  6. Autophagy. 2022 Nov 17.
      The functions of mammalian Atg8 proteins (mATG8s) expand beyond canonical autophagy and include processes collectively referred to as Atg8ylation. Global modulation of protein synthesis under stress conditions is governed by MTOR and liquid-liquid phase separated condensates containing ribonucleoprotein particles known as stress granules (SGs). We report that lysosomal damage induces SGs acting as a hitherto unappreciated inhibitor of protein translation via EIF2A/eIF2α phosphorylation while favoring an ATF4-dependent integrated stress response. SGs are induced by lysosome-damaging agents, SARS-CoV-2 open reading frame 3a protein (ORF3a) expression, Mycobacterium tuberculosis infection, and exposure to proteopathic MAPT/tau. Proteomic studies revealed recruitment to damaged lysosomes of the core SG proteins NUFIP2 and G3BP1 along with the GABARAPs of the mATG8 family. The recruitment of these proteins is independent of SG condensates or canonical autophagy. GABARAPs interact directly with NUFIP2 and G3BP1 whereas Atg8ylation is needed for their recruitment to damaged lysosomes. At the lysosome, NUFIP2 contributes to MTOR inactivation together with LGALS8 (galectin 8) via the Ragulator-RRAGA-RRAGB complex. The separable functions of NUFIP2 and G3BP1 in SG formation vis-a-vis their role in MTOR inactivation are governed by GABARAP and Atg8ylation. Thus, cells employ membrane Atg8ylation to control and coordinate SG and MTOR responses to lysosomal damage.
    Keywords:  Atg8ylation; MTOR; Mycobacterium tuberculosis; NUFIP2; PKR; SARS-CoV-2 ORF3a; integrated stress response; lysosomal damage; proteopathic tau; stress granules
    DOI:  https://doi.org/10.1080/15548627.2022.2148900
  7. Nature. 2022 Nov 16.
      Solid cancers exhibit a dynamic balance between cell death and proliferation ensuring continuous tumour maintenance and growth1,2. Increasing evidence links enhanced cancer cell apoptosis to paracrine activation of cells in the tumour microenvironment initiating tissue repair programs that support tumour growth3,4, yet the direct effects of dying cancer cells on neighbouring tumour epithelia and how this paracrine effect potentially contributes to therapy resistance are unclear. Here we demonstrate that chemotherapy-induced tumour cell death in patient-derived colorectal tumour organoids causes ATP release triggering P2X4 (also known as P2RX4) to mediate an mTOR-dependent pro-survival program in neighbouring cancer cells, which renders surviving tumour epithelia sensitive to mTOR inhibition. The induced mTOR addiction in persisting epithelial cells is due to elevated production of reactive oxygen species and subsequent increased DNA damage in response to the death of neighbouring cells. Accordingly, inhibition of the P2X4 receptor or direct mTOR blockade prevents induction of S6 phosphorylation and synergizes with chemotherapy to cause massive cell death induced by reactive oxygen species and marked tumour regression that is not seen when individually applied. Conversely, scavenging of reactive oxygen species prevents cancer cells from becoming reliant on mTOR activation. Collectively, our findings show that dying cancer cells establish a new dependency on anti-apoptotic programs in their surviving neighbours, thereby creating an opportunity for combination therapy in P2X4-expressing epithelial tumours.
    DOI:  https://doi.org/10.1038/s41586-022-05426-1
  8. Cancer Cell. 2022 Nov 14. pii: S1535-6108(22)00509-8. [Epub ahead of print]40(11): 1273-1275
      In this issue of Cancer Cell, Foster and colleagues explore the heterogeneity in cancer-associated fibroblasts (CAFs) across tissue types and species, and they identify mechanoresponsive (MR), immunomodulatory (IM), and steady-state-like (SSL) CAFs. They show that altering the relative abundance of these CAF subtypes influences tumor progression and response to anti-tumor therapy.
    DOI:  https://doi.org/10.1016/j.ccell.2022.10.018
  9. Nat Rev Cancer. 2022 Nov 16.
      Navigation through the bulk tumour, entry into the blood vasculature, survival in the circulation, exit at distant sites and resumption of proliferation are all steps necessary for tumour cells to successfully metastasize. The ability of tumour cells to complete these steps is highly dependent on the timing and sequence of the interactions that these cells have with the tumour microenvironment (TME), including stromal cells, the extracellular matrix and soluble factors. The TME thus plays a major role in determining the overall metastatic phenotype of tumours. The complexity and cause-and-effect dynamics of the TME cannot currently be recapitulated in vitro or inferred from studies of fixed tissue, and are best studied in vivo, in real time and at single-cell resolution. Intravital imaging (IVI) offers these capabilities, and recent years have been a time of immense growth and innovation in the field. Here we review some of the recent advances in IVI of mammalian models of cancer and describe how IVI is being used to understand cancer progression and metastasis, and to develop novel treatments and therapies. We describe new techniques that allow access to a range of tissue and cancer types, novel fluorescent reporters and biosensors that allow fate mapping and the probing of functional and phenotypic states, and the clinical applications that have arisen from applying these techniques, reporters and biosensors to study cancer. We finish by presenting some of the challenges that remain in the field, how to address them and future perspectives.
    DOI:  https://doi.org/10.1038/s41568-022-00527-5
  10. Cancer Res. 2022 Nov 15. 82(22): 4124-4125
      The role of exercise in cancer progression is an emerging field of research, with intriguing evidence for physical activity playing an inhibitory role in cancer onset. In their recent publication, Sheinboim and colleagues demonstrate the impact of physical exercise on melanoma primary tumor growth and metastasis. They establish that physical exercise decreases metastatic spread, using both human epidemiologic data and in vivo models of melanoma metastasis. Systemic metabolic reprogramming of organs, induced by exercise, leads to a decrease in melanoma growth and progression as healthy organs are able to outcompete melanoma cells for nutrients. Exercise led to systemic metabolic changes in carbohydrate metabolism, glycolysis, and oxidative phosphorylation as well as mitochondrial biogenesis. Interestingly, the "metabolic shield" created by exercise could be reversed using the mTOR inhibitor rapamycin. This study highlights the importance of metabolic plasticity in metastasis and uncovers a direct link between systemic metabolic reprogramming and mTOR signaling. Overall, the study by Sheinboim and colleagues provides a more detailed understanding of the metastatic requirements in the context of energy and nutrient availability and the impact of exercise on cancer progression, highlighting novel opportunities for therapeutic intervention. See related article by Sheinboim et al., p. 4164.
    DOI:  https://doi.org/10.1158/0008-5472.CAN-22-2898
  11. Mol Oncol. 2022 Nov 18.
      The modest clinical benefits of neoadjuvant chemotherapy (NAT) in pancreatic ductal adenocarcinoma (PDAC) are associated with a lack of robust data on treatment-induced changes in the tumor. To this end, comparative proteomic profiling of tumor tissue samples from treatment-naïve (TN, n=20) and NAT-treated (n=22) PDACs was performed. Differentially expressed proteins were identified and correlation with overall survival (OS) was performed. Tumors were also examined for histopathological changes and expression of cancer stem cell (CSC) markers. Serum from 33 matched patients was analyzed for metabolic markers. Cytotoxicity, proliferation, and expression of CSC markers were assessed in chemoresistant Panc-1 and Mia PaCa-2 cells. Of the 2,265 proteins identified, 227 and 144 proteins showed significantly altered expression and differential phosphorylation, respectively, in NAT compared to TN samples. The majority of these were metabolism-related proteins, and 14 of these correlated moderately with OS. NAT-treated tumors and chemoresistant cancer cells showed increased expression of CSC markers. Serum ALDH1A1 was higher in NAT compared to TN. Differentially phosphorylated proteins were mainly involved in cytoskeleton organization, cell locomotion, motility and migration, and 17 of these showed a strong positive correlation with OS. This study provides evidence of the effects of NAT on PDAC metabolism at both the tumor and the systemic levels. NAT-treated tumors showed significantly lower expression of metabolic proteins, and patients who underwent NAT showed reduced serum lactate and high-density lipoprotein (HDL)-cholesterol. Lastly, cancer cells that survived cytotoxic treatment expressed higher CSC markers, both in vivo and in vitro.
    Keywords:  Cancer stem cells; Metabolism; Neoadjuvant chemotherapy; Pancreatic cancer; Proteomics
    DOI:  https://doi.org/10.1002/1878-0261.13344
  12. Cancer Res Commun. 2022 Sep;2(9): 951-965
      Pancreatic ductal adenocarcinoma (PDAC) continues to be a major health problem. A ketogenic diet (KD), characterized by a very low carbohydrate and high fat composition, has gained attention for its anti-tumor potential. We evaluated the effect and mechanisms of feeding a strict KD alone or in combination with gemcitabine in the autochthonous LSL-KrasG12D/+; LSL-Trp53 R172H/+; Pdx1-Cre (KPC) mouse model. For this purpose, both male and female pancreatic tumor-bearing KPC mice were allocated to a control diet (CD; %kcal: 70% carb, 14% protein, 16% fat), a KD (%kcal: 14% protein, 1% carb, 85% fat), a CD + gemcitabine (CG), or a KD + gemcitabine (KG) group. Mice fed a KD alone or in combination with gemcitabine showed significantly increased blood β-hydroxybutyrate levels compared to mice fed a CD or CG. KPC mice fed a KG had a significant increase in overall median survival compared to KPC mice fed a CD (increased overall median survival by 42%). Interestingly, when the data was disaggregated by sex, the effect of a KG was significant in female KPC mice (60% increase in median overall survival), but not in male KPC mice (28% increase in median overall survival). Mechanistically, the enhanced survival response to a KD combined with gemcitabine was multifactorial, including inhibition of ERK and AKT pathways, regulation of fatty acid metabolism and the modulation of the gut microbiota. In summary, a KD in combination with gemcitabine appears beneficial as a treatment strategy in PDAC in KPC mice, deserving further clinical evaluation.
    Keywords:  ERK and AKT signaling pathways; Ketogenic diet; Lipid metabolism; gemcitabine; microbiome; pancreatic cancer; pancreatic ductal adenocarcinoma
    DOI:  https://doi.org/10.1158/2767-9764.crc-22-0256
  13. Nat Commun. 2022 Nov 18. 13(1): 7078
      Collagen I, the most abundant protein in humans, is ubiquitous in solid tumors where it provides a rich source of exploitable metabolic fuel for cancer cells. While tumor cells were unable to exploit collagen directly, here we show they can usurp metabolic byproducts of collagen-consuming tumor-associated stroma. Using genetically engineered mouse models, we discovered that solid tumor growth depends upon collagen binding and uptake mediated by the TEM8/ANTXR1 cell surface protein in tumor-associated stroma. Tumor-associated stromal cells processed collagen into glutamine, which was then released and internalized by cancer cells. Under chronic nutrient starvation, a condition driven by the high metabolic demand of tumors, cancer cells exploited glutamine to survive, an effect that could be reversed by blocking collagen uptake with TEM8 neutralizing antibodies. These studies reveal that cancer cells exploit collagen-consuming stromal cells for survival, exposing an important vulnerability across solid tumors with implications for developing improved anticancer therapy.
    DOI:  https://doi.org/10.1038/s41467-022-34643-5
  14. FEBS J. 2022 Nov;289(22): 6822-6831
      The major criterion that distinguishes eukaryotes from prokaryotes is the presence of organelles in the former. Organelles provide a compartment in which biochemical processes are corralled within bespoke biophysical conditions and act as storage depots, powerhouses, waste storage/recycling units and innate immune signalling hubs. A key challenge faced by organelles is to define, and then retain, their identity; this is mediated by complex proteostasis mechanisms including the import of an organelle-specific proteome, the exclusion of non-organellar proteins and the removal of misfolded proteins via dedicated quality control mechanisms. This Special Issue on Organelle Homeostasis provides an engaging, eclectic, yet integrative, perspective on organelle homeostasis in a range of organelles including those from the secretory and endocytic pathways, mitochondria, the autophagy-lysosomal pathway and the nucleus and its sub-compartments. Some lesser-known organelles including migrasomes (organelles that are released by migrating cells) and GOMED (a Golgi-specific form of autophagy) are also introduced. In the spirit of the principles of organelle biology, we hope you find the reviews in this Issue both encapsulating and captivating, and we thank the authors for their excellent contributions.
    Keywords:  endoplasmic reticulum; mitochondria; nucleus; organelle homeostasis; quality control
    DOI:  https://doi.org/10.1111/febs.16667
  15. Nat Metab. 2022 Nov 14.
      Food cues during fasting elicit Pavlovian conditioning to adapt for anticipated food intake. However, whether the olfactory system is involved in metabolic adaptations remains elusive. Here we show that food-odor perception promotes lipid metabolism in male mice. During fasting, food-odor stimulation is sufficient to increase serum free fatty acids via adipose tissue lipolysis in an olfactory-memory-dependent manner, which is mediated by the central melanocortin and sympathetic nervous systems. Additionally, stimulation with a food odor prior to refeeding leads to enhanced whole-body lipid utilization, which is associated with increased sensitivity of the central agouti-related peptide system, reduced sympathetic activity and peripheral tissue-specific metabolic alterations, such as an increase in gastrointestinal lipid absorption and hepatic cholesterol turnover. Finally, we show that intermittent fasting coupled with food-odor stimulation improves glycemic control and prevents insulin resistance in diet-induced obese mice. Thus, olfactory regulation is required for maintaining metabolic homeostasis in environments with either an energy deficit or energy surplus, which could be considered as part of dietary interventions against metabolic disorders.
    DOI:  https://doi.org/10.1038/s42255-022-00673-y
  16. Sci Immunol. 2022 Nov 25. 7(77): eabm8182
      T cell proliferation and cytokine production are bioenergetically and biosynthetically costly. The inability to meet these metabolic demands results in altered differentiation, accompanied by impaired effector function, and attrition of the immune response. Interleukin-17-producing CD4 T cells (TH17s) are mediators of host defense, autoimmunity, and antitumor immunity in the setting of adoptive T cell therapy. TH17s are long-lived cells that require mitochondrial oxidative phosphorylation (OXPHOS) for effector function in vivo. Considering that TH17s polarized under standardized culture conditions are predominately glycolytic, little is known about how OXPHOS regulates TH17 processes, such as their ability to persist and thus contribute to protracted immune responses. Here, we modified standardized culture medium and identified a culture system that reliably induces OXPHOS dependence in TH17s. We found that TH17s cultured under OXPHOS conditions metabolically resembled their in vivo counterparts, whereas glycolytic cultures were dissimilar. OXPHOS TH17s exhibited increased mitochondrial fitness, glutamine anaplerosis, and an antiapoptotic phenotype marked by high BCL-XL and low BIM. Limited mitophagy, mediated by mitochondrial fusion regulator OPA-1, was critical to apoptotic resistance in OXPHOS TH17s. By contrast, glycolytic TH17s exhibited more mitophagy and an imbalance in BCL-XL to BIM, thereby priming them for apoptosis. In addition, through adoptive transfer experiments, we demonstrated that OXPHOS protected TH17s from apoptosis while enhancing their persistence in the periphery and tumor microenvironment in a murine model of melanoma. Together, our work demonstrates how metabolism regulates TH17 cell fate and highlights the potential for therapies that target OXPHOS in TH17-driven diseases.
    DOI:  https://doi.org/10.1126/sciimmunol.abm8182
  17. Nat Chem Biol. 2022 Nov 18.
      Cells are exquisitely compartmentalized to achieve precise spatiotemporal regulation of myriad processes and pathways. Phase separation offers one way to achieve territorial organization in the cellular context, via the creation of membrane-less organelles (MLOs). MLOs formed through phase separation are associated with numerous critical biological functions. Although hundreds of publications on related topics are produced each year, robust criteria for the determination of biologically meaningful phase separation are yet to be well established. Here we present some principles and propose a few guidelines for phase-separation studies in biology. Specifically, we provide an in-depth experiment pipeline for phase-separation studies, including mechanisms of the molecular driving forces, ways to correlate in vivo and in vitro observations, and strategies to relate the phase-separation phenomenon to biological functions. We also intend to contribute to streamlining the aforementioned diagnostic criteria by further stressing a few common caveats in the field.
    DOI:  https://doi.org/10.1038/s41589-022-01204-2
  18. Mol Cell. 2022 Nov 08. pii: S1097-2765(22)01058-9. [Epub ahead of print]
      Maintenance of energy level to drive movements and material exchange with the environment is a basic principle of life. AMP-activated protein kinase (AMPK) senses energy level and is a major regulator of cellular energy responses. The gamma subunit of AMPK senses elevated ratio of AMP to ATP and allosterically activates the alpha catalytic subunit to phosphorylate downstream effectors. Here, we report that knockout of AMPKγ, but not AMPKα, suppressed phosphorylation of eukaryotic translation elongation factor 2 (eEF2) induced by energy starvation. We identified PPP6C as an AMPKγ-regulated phosphatase of eEF2. AMP-bound AMPKγ sequesters PPP6C, thereby blocking dephosphorylation of eEF2 and thus inhibiting translation elongation to preserve energy and to promote cell survival. Further phosphoproteomic analysis identified additional targets of PPP6C regulated by energy stress in an AMPKγ-dependent manner. Thus, AMPKγ senses cellular energy availability to regulate not only AMPKα kinase, but also PPP6C phosphatase and possibly other effectors.
    Keywords:  AMPK; PPP6C; eEF2; energy level; phosphorylation
    DOI:  https://doi.org/10.1016/j.molcel.2022.10.030
  19. Biophys J. 2022 Nov 16. pii: S0006-3495(22)00942-0. [Epub ahead of print]
      Actin networks polymerize and depolymerize to construct highly organized structures, thereby, endowing the mechanical phenotypes found in a cell. It is generally believed that the amount of filamentous actin and actin network architecture determine cytoplasmic viscoelasticity of the whole cell. However, the intrinsic complexity of a cell and presence of endogenous cellular components make it difficult to study the differential roles of distinct actin networks in regulating cell mechanics. Here, we model a cell by using giant unilamellar vesicles (GUVs) encapsulating actin filaments and networks assembled by various actin crosslinker proteins. Perturbation of these cytoskeletal vesicles using AC electric fields revealed that deformability depends on actin network architecture. While actin-free vesicles exhibited large electromechanical deformations, deformations of GUVs encapsulating actin filaments were significantly dampened. The suppression of electrodeformation of actin-GUVs can be similarly recapitulated by using aqueous PEG 8000 solutions at different concentrations to modulate solution viscoelasticity. Furthermore, alpha actinin-crosslinked actin networks resulted in decreased GUV deformability in comparison to actin filament-encapsulating GUVs, and membrane-associated actin networks through the formation of dendritic actin cortex greatly dampened electrodeformation of GUVs. These results highlight the organization of actin networks regulates the mechanics of GUVs and shed insights into the origin of differential deformability of cells.
    Keywords:  Actin network reconstitution; Giant vesicle electrodeformation; Numerical analysis
    DOI:  https://doi.org/10.1016/j.bpj.2022.11.026
  20. Mol Oncol. 2022 Nov 16.
      KRASG12D is the most frequent KRAS mutation in human cancer with particularly high frequencies in pancreatic and colorectal cancer. Informed by the structure of the KRASG12C inhibitor adagrasib, Hallin et al have now, through multiple rounds of structure-based drug design, identified and validated a potent, selective, and non-covalent KRASG12D inhibitor, MRTX1133. This study demonstrated that MRTX1133 inhibited both the inactive and active state of KRASG12D and showed potent anti-tumor activity in several pre-clinical models of pancreatic and colorectal cancer, especially when combined with cetuximab, a monoclonal antibody against the EGFR, or BYL-719, a potent PI3Kα inhibitor.
    Keywords:  KRASG12D; colorectal cancer; combination therapies; non-covalent binding; pancreatic ductal adenocarcinoma
    DOI:  https://doi.org/10.1002/1878-0261.13341
  21. Cell Metab. 2022 Nov 08. pii: S1550-4131(22)00489-2. [Epub ahead of print]
      Impairment of translation can lead to collisions of ribosomes, which constitute an activation platform for several ribosomal stress-surveillance pathways. Among these is the ribotoxic stress response (RSR), where ribosomal sensing by the MAP3K ZAKα leads to activation of p38 and JNK kinases. Despite these insights, the physiological ramifications of ribosomal impairment and downstream RSR signaling remain elusive. Here, we show that stalling of ribosomes is sufficient to activate ZAKα. In response to amino acid deprivation and full nutrient starvation, RSR impacts on the ensuing metabolic responses in cells, nematodes, and mice. The RSR-regulated responses in these model systems include regulation of AMPK and mTOR signaling, survival under starvation conditions, stress hormone production, and regulation of blood sugar control. In addition, ZAK-/- male mice present a lean phenotype. Our work highlights impaired ribosomes as metabolic signals and demonstrates a role for RSR signaling in metabolic regulation.
    Keywords:  AMPK; FGF21; ZAK-alpha; amino acid starvation; mTOR; metabolic regulation; mouse models; ribosome collision; ribotoxic stress response
    DOI:  https://doi.org/10.1016/j.cmet.2022.10.011
  22. Front Cell Dev Biol. 2022 ;10 1048630
      Genetic heterogeneity of metastatic dissemination has proven challenging to identify exploitable markers of metastasis; this bottom-up approach has caused a stalemate between advances in metastasis and the late stage of the disease. Advancements in quantitative cellular imaging have allowed the detection of morphological phenotype changes specific to metastasis, the morphological changes connected to the underlying complex signaling pathways, and a robust readout of metastatic cell state. This review focuses on the recent machine and deep learning developments to gain detailed information about the metastatic cell state using light microscopy. We describe the latest studies using quantitative cell imaging approaches to identify cell appearance-based metastatic patterns. We discuss how quantitative cancer biologists can use these frameworks to work backward toward exploitable hidden drivers in the metastatic cascade and pioneering new Frontier drug discoveries specific for metastasis.
    Keywords:  cellular morphology; deep learning; light microscopy; machine learning; metastasis; quantitative imaging
    DOI:  https://doi.org/10.3389/fcell.2022.1048630
  23. Cell Syst. 2022 Nov 16. pii: S2405-4712(22)00402-1. [Epub ahead of print]13(11): 911-923.e9
      Morphological and gene expression profiling can cost-effectively capture thousands of features in thousands of samples across perturbations by disease, mutation, or drug treatments, but it is unclear to what extent the two modalities capture overlapping versus complementary information. Here, using both the L1000 and Cell Painting assays to profile gene expression and cell morphology, respectively, we perturb human A549 lung cancer cells with 1,327 small molecules from the Drug Repurposing Hub across six doses, providing a data resource including dose-response data from both assays. The two assays capture both shared and complementary information for mapping cell state. Cell Painting profiles from compound perturbations are more reproducible and show more diversity but measure fewer distinct groups of features. Applying unsupervised and supervised methods to predict compound mechanisms of action (MOAs) and gene targets, we find that the two assays not only provide a partially shared but also a complementary view of drug mechanisms. Given the numerous applications of profiling in biology, our analyses provide guidance for planning experiments that profile cells for detecting distinct cell types, disease phenotypes, and response to chemical or genetic perturbations.
    Keywords:  Cell Painting; L1000; benchmark; drug discovery; high-dimensional profiling; images; systems biology
    DOI:  https://doi.org/10.1016/j.cels.2022.10.001
  24. Eur J Epidemiol. 2022 Nov 17.
      Sir Richard Peto is well known for proposing puzzling paradoxes in cancer biology-some more well-known than others. In a 1984 piece, Peto proposed that after decades of molecular biology in cancer research, we are still ignorant of the biology underpinning cancer. Cancer is a product of somatic mutations. How do these mutations arise and what are the mechanisms? As an epidemiologist, Peto asked if we really need to understand mechanisms in order to prevent cancer? Four decades after Peto's proposed ignorance in cancer research, we can simply ask, are we still ignorant? Did the great pursuit to uncover mechanisms of cancer eclipse our understanding of causes and preventions? Or can we get closer to treating and preventing cancer by understanding the underlying mechanisms that make us most vulnerable to this disease?
    Keywords:  Cancer; Evolutionary theory; Peto’s paradox; Somatic mutations
    DOI:  https://doi.org/10.1007/s10654-022-00936-8
  25. Cancer Epidemiol. 2022 Nov 14. pii: S1877-7821(22)00200-4. [Epub ahead of print]82 102295
       BACKGROUND: Previous studies of dietary patterns and pancreatic cancer risk have been inconclusive; we aimed to investigate the association of Mediterranean Diet Score (MDS), Alternative Healthy Eating Index-2010 (AHEI-2010), and Dietary Inflammatory Index (DII®) with risk of pancreatic cancer.
    METHODS: We used data from the Melbourne Collaborative Cohort Study including 33,690 men and women aged 40-69 years at recruitment in 1990-1994. A total of 258 incident cases of pancreatic cancer was identified over an average of 23.7 years of follow-up. Hazard ratios (HR) were estimated using Cox regression, with age as the underlying time metric, adjusting for potential confounders including sex, height, country of birth, education, socio-economic position, physical activity, energy intake, smoking status, pack-years smoking, years since quitting smoking, and alcohol intake.
    RESULTS: A healthier diet as assessed by the AHEI-2010 was associated with a lower risk of pancreatic cancer [HRQuartile4 vs Quartile1 = 0.58; 95%CI 0.40 - 0.85; p for trend 0.003]. Weaker but consistent evidence was observed for the other indexes [DII® HRQuartile4 vs Quartile1 = 1.30; 95%CI 0.82 - 2.06; p for trend 0.1], [MDS HRCategory3 vs Category1 = 0.79; 95%CI 0.49 - 1.26; p for trend 0.06].
    CONCLUSION: Adherence to a healthier diet, as assessed by the AHEI-2010, may reduce the risk of pancreatic cancer.
    Keywords:  Diet; Epidemiology; Inflammation; Pancreatic cancer; Prospective cohort
    DOI:  https://doi.org/10.1016/j.canep.2022.102295
  26. J Cell Biol. 2023 Jan 02. pii: e202111053. [Epub ahead of print]222(1):
      Maintaining long, energetically demanding axons throughout the life of an animal is a major challenge for the nervous system. Specialized glia ensheathe axons and support their function and integrity throughout life, but glial support mechanisms remain poorly defined. Here, we identified a collection of secreted and transmembrane molecules required in glia for long-term axon survival in vivo. We showed that the majority of components of the TGFβ superfamily are required in glia for sensory neuron maintenance but not glial ensheathment of axons. In the absence of glial TGFβ signaling, neurons undergo age-dependent degeneration that can be rescued either by genetic blockade of Wallerian degeneration or caspase-dependent death. Blockade of glial TGFβ signaling results in increased ATP in glia that can be mimicked by enhancing glial mitochondrial biogenesis or suppressing glial monocarboxylate transporter function. We propose that glial TGFβ signaling supports axon survival and suppresses neurodegeneration through promoting glial metabolic support of neurons.
    DOI:  https://doi.org/10.1083/jcb.202111053
  27. Methods Mol Biol. 2023 ;2587 513-526
      Plasma membrane injury activates membrane trafficking and remodeling events that are required for the injured membrane to repair. With the rapidity of the membrane repair process, the repair response needs to be monitored at high temporal and spatial resolution. In this chapter, we describe the use of live cell optical imaging approaches to monitor injury-triggered bulk and individual vesicle endocytosis. Use of these approaches allows quantitatively assessment of the rate of retrieval of the injured plasma membrane by bulk endocytosis as well as by endocytosis of individual caveolae following plasma membrane injury.
    Keywords:  Caveolae; Confocal; Live cell imaging; Membrane repair; Muscle; Muscular dystrophy
    DOI:  https://doi.org/10.1007/978-1-0716-2772-3_27
  28. Biophys J. 2022 Nov 14. pii: S0006-3495(22)00936-5. [Epub ahead of print]
      Unfavorable lipid-lipid pairwise (PW) interactions between HiTm and LowTm lipids drive liquid-disordered (Ld) + liquid-ordered (Lo) phase separation. Large size of phase domains is opposed by lipid dipole repulsions, which are more significant compared to the PW interactions for naturally abundant LowTm lipids such as palmitoyl oleoyl phosphatidylcholine (POPC). During the nano-to-macro domain size transition, no lipid phase transition occurs, and measured properties of Ld + Lo nanodomains are found to be essentially the same as those of macrodomains. Use of macrodomains in mixtures to model cell plasma membranes (PM) is helpful, enabling study by optical microscopy. Use of asymmetric GUVs to model a PM reveals that ordered phase domains in one leaflet induce ordered domains in an otherwise uniform phase in the apposing leaflet that models a cytoplasmic leaflet. Because macro and nano phase properties are so similar, we conclude that a cell PM that has nano-scale Ld + Lo phase domains in the exoplasmic leaflet, is likely to induce nano-scale ordered domains in the cytoplasmic leaflet.
    DOI:  https://doi.org/10.1016/j.bpj.2022.11.020