bims-glucam Biomed News
on Glutamine cancer metabolism
Issue of 2021–02–28
sixteen papers selected by
Sreeparna Banerjee, Middle East Technical University
  1. Identification and Characterization of IMD-0354 as a Glutamine Carrier Protein Inhibitor in Melanoma.
  2. Oral glutamine inhibits tumor growth of gastric cancer bearing mice by improving immune function and activating apoptosis pathway.
  3. Circular RNA circDNM3OS Functions as a miR-145-5p Sponge to Accelerate Cholangiocarcinoma Growth and Glutamine Metabolism by Upregulating MORC2.
  4. Targeting YTHDF1 effectively re-sensitizes cisplatin-resistant colon cancer cells by modulating GLS-mediated glutamine metabolism.
  5. Differences in cell death in methionine versus cysteine depletion.
  6. Oxidative stress-mediated AMPK inactivation determines the high susceptibility of LKB1-mutant NSCLC cells to glucose starvation.
  7. Mechanism and reversal of drug-induced nephrotoxicity on a chip.
  8. Fructose reprogrammes glutamine-dependent oxidative metabolism to support LPS-induced inflammation.
  9. Dietary Intervention Impacts Immune Cell Functions and Dynamics by Inducing Metabolic Rewiring.
  10. An investigation of glutamate quantification with PRESS and MEGA-PRESS.
  11. In vivo CRISPR screening reveals nutrient signaling processes underpinning CD8+ T cell fate decisions.
  12. One-carbon metabolism in cancer cells: a critical review based on a core model of central metabolism.
  13. Transketolase regulates sensitivity to APR-246 in p53-null cells independently of oxidative stress modulation.
  14. Asparagine couples mitochondrial respiration to ATF4 activity and tumor growth.
  15. Insights into the novel function of system Xc- in regulated cell death.
  16. Glutathione Content Detection of Single Cells under Ingested Doxorubicin by Functionalized Glass Nanopores.
  1. Mol Cancer Ther. 2021 Feb 25. pii: molcanther.0354.2020. [Epub ahead of print]
    Identification and Characterization of IMD-0354 as a Glutamine Carrier Protein Inhibitor in Melanoma.
    Yongmei Feng, Gaurav Pathria, Susanne Heynen-Genel, Michael R Jackson, Brian James, Jun Yin, David A Scott, Ze'ev A Ronai.
      A key hallmark of cancer, altered metabolism, is central to cancer pathogenesis and therapy resistance. Robust glutamine metabolism is among cellular processes regulating tumor progression and responsiveness to therapy in a number of cancers, including melanoma and breast cancer. Among mechanisms underlying the increase in glutamine metabolism in tumors is enhanced glutamine uptake mediated by the glutamine transporters, with SLC1A5 (also known as ASCT2) shown to play a predominant role. Correspondingly, increased SLC1A5 expression coincides with poorer survival in breast cancer and melanoma patients. Therefore, we performed an image-based screen to identify small-molecules that are able to prevent the localization of SLC1A5 to the plasma membrane without impacting cell shape. From 7,000 small molecules, 9 were selected as hits, of which one (IMD-0354) qualified for further detailed functional assessment. IMD-0354 was confirmed as a potent inhibitor of glutamine uptake that attained sustained low intracellular glutamine levels. Concomitant with its inhibition of glutamine uptake, IMD-0354 attenuated mTOR signaling, suppressed 2D and 3D growth of melanoma cells, and induced cell cycle arrest, autophagy and apoptosis. Pronounced effect of IMD-0354 was observed in different tumor derived cell lines, compared with non-transformed cells. RNAseq analysis identified the unfolded protein response, cell cycle and DNA damage pathways to be affected by IMD-0354. Combination of IMD-0354 with GLS1 or LDHA inhibitors enhanced melanoma cell death. In vivo, IMD-0354 suppressed melanoma growth in a xenograft model. As a modulator of glutamine metabolism, IMD-0354 may serve as an important therapeutic and experimental tool that deserves further examination.
    DOI:  https://doi.org/10.1158/1535-7163.MCT-20-0354
  2. Tissue Cell. 2021 Feb 05. pii: S0040-8166(21)00024-0. [Epub ahead of print]71 101508
    Oral glutamine inhibits tumor growth of gastric cancer bearing mice by improving immune function and activating apoptosis pathway.
    Li-Bin Li, Tai-Yong Fang, Wen-Ji Xu.
      Gastric cancer is one of the most common cancers in the world. It has been shown that exogenous glutamine (GLN) can inhibit the growth of tumor in vivo, but the relationship between GLN and gastric cancer has not been studied. The gastric cancer bearing mouse model was constructed and taken GLN orally at the same time, and the results found that oral GLN (1 or 2 g/kg/d) significantly inhibited the growth rate of tumor and reduce the weight of tumor tissues. Immunohistochemistry showed that oral GLN significantly reduced the PCNA index, which further proved that GLN could inhibit the growth of tumor cells. At the same time, TUNEL assay showed that oral GLN significantly enhanced the apoptosis levels of tumor cells. In addition, GLN reduced GSH levels in tumor tissues, but increased the levels of GSH in plasma, improved the T-lymphocyte transformation rate and NK cell activity, significantly inhibited the secretion of TNF-α and promoted the secretion of IL-2, thus regulating the immune function in vivo. Further detection of apoptosis pathway showed that oral GLN significantly enhanced the expression of pro-apoptotic factor Bad and inhibited the expression of Bcl-2. Meanwhile, GLN significantly increased the activities of Caspase-3, Caspase-8, caspase-9 and PARP. GSH activator NAC had a similar effect to GLN, which could improve the immune function and activate apoptosis pathway, while GSH inhibitor BSO significantly blocked the regulation of GLN, destroyed the immune balance and inhibited apoptosis, but IL-2 significantly blocked the anti-apoptotic effect of BSO. Therefore, oral GLN can improve immune function and activate apoptosis pathway through GSH, and then inhibit the growth of tumor in vivo.
    Keywords:  Apoptosis; Gastric cancer; Glutamine; Glutathione; Immunity
    DOI:  https://doi.org/10.1016/j.tice.2021.101508
  3. Onco Targets Ther. 2021 ;14 1117-1129
    Circular RNA circDNM3OS Functions as a miR-145-5p Sponge to Accelerate Cholangiocarcinoma Growth and Glutamine Metabolism by Upregulating MORC2.
    Yongfeng Su, Ting Yu, Yaqi Wang, Xianming Huang, Xiaoyong Wei.
       Background: Cholangiocarcinoma (CCA) is the second most common liver malignant tumor. CircRNA hsa_circ_0005230 (circDNM3OS) has been reported to exert an oncogenic role in CCA. However, the mechanisms related to circDNM3OS in CAA progression have not been fully elucidated.
    Methods: The expression of circDNM3OS, microRNA (miR)-145-5p, and MORC2 (MORC Family CW-Type Zinc Finger 2) mRNA were analyzed by quantitative real-time polymerase chain reaction (qRT-PCR). Cell proliferation, colony formation, migration, invasion, and apoptosis were evaluated by Cell Counting Kit-8 (CCK-8), colony formation, transwell, wound-healing, and flow cytometry assays. The levels of glutamine, α-KG (α-ketoglutarate), and ATP (adenosine triphosphate) were detected using commercial kits. The relationship between circDNM3OS or MORC2 and miR-145-5p was verified by dual-luciferase reporter and/or RNA immunoprecipitation (RIP) assays. Protein level of MORC2 was measured by Western blotting. The role of circDNM3OS in CCA growth was verified by xenograft experiment.
    Results: CircDNM3OS and MORC2 were upregulated while miR-145-5p was downregulated in CCA tissues and cells. Inhibition of circDNM3OS reduced xenograft tumor growth in vivo and constrained proliferation, colony formation, migration, invasion, induced apoptosis, and reduced glutamine metabolism of CCA cells in vitro. CircDNM3OS sponged miR-145-5p to elevate MORC2 expression. MiR-145-5p silencing overturned circDNM3OS knockdown-mediated influence on malignancy and glutamine metabolism of CCA cells. Also, MORC2 overexpression reversed the repressive impact of miR-145-5p mimic on malignancy and glutamine metabolism of CCA cells.
    Conclusion: CircDNM3OS facilitates CCA growth and glutamine metabolism by regulating the miR-145-5p/MORC2 pathway, offering a novel mechanism to understand the progression of CCA.
    Keywords:  CCA; MORC2; circDNM3OS; glutamine; miR-145-5p
    DOI:  https://doi.org/10.2147/OTT.S289241
  4. Mol Ther Oncolytics. 2021 Mar 26. 20 228-239
    Targeting YTHDF1 effectively re-sensitizes cisplatin-resistant colon cancer cells by modulating GLS-mediated glutamine metabolism.
    Ping Chen, Xi-Qiao Liu, Xiang Lin, Li-Ying Gao, Shuo Zhang, Xuan Huang.
      Colorectal cancer (CRC) has a high mortality rate and poor prognosis. Despite chemotherapeutic agents such as cisplatin, which has achieved a better prognosis and survival rate against cancer, drug resistance leads to significant challenges. Accumulating evidence suggests that YTHDF1, the N 6-methyladenosine (m6A) "reader," is an important regulator in tumor progresses. Herein, we report that YTHDF1 was significantly upregulated in human colon tumors and cell lines. Overexpression of YTHDF1 decreased the cisplatin sensitivity of colon cancer cells. From the established cisplatin-resistant CRC cell line (LoVo CDDP R), we detected that YTHDF1 was significantly upregulated in cisplatin-resistant CRC cells. Intriguingly, RNA sequencing (RNA-seq) results revealed that glutamine metabolism enzymes were clearly upregulated in LoVo CDDP R cells. Glutamine uptake, that is, glutaminase (GLS) activity, was upregulated in LoVo CDDP R cells. Furthermore, bioinformatics analysis indicated that the 3' UTR of GLS1 contained a putative binding motif of YTHDF1, and an interaction was further validated by a protein-RNA interaction assay (RNA immunoprecipitation [RIP]). Furthermore, we demonstrated that YTHDF1 promoted protein synthesis of GLS1. Inhibiting GLS1 effectively synergizes with cisplatin to induce colon cancer cell death. Finally, that YTHDF1 mediated cisplatin through the GLS1-glutamine metabolism axis was validated by an in vivo xenograft mouse model. In summary, our study reveals a new mechanism for YTHDF1-promoted cisplatin resistance, contributing to overcoming chemoresistant colon cancers.
    DOI:  https://doi.org/10.1016/j.omto.2021.01.001
  5. Environ Mol Mutagen. 2021 Feb 21.
    Differences in cell death in methionine versus cysteine depletion.
    Katherine F Wallis, Lauren C Morehead, Jordan T Bird, Stephanie Byrum, Isabelle R Miousse.
      Restriction of the sulfur amino acids methionine and cysteine has recently been proposed as potential adjuvant therapy in cancer. While cysteine depletion has been associated with ferroptotic cell death, methionine depletion has not. We hypothesized that comparing the response of melanoma cell lines to depletion of the amino acids methionine and cysteine would give us insight into the critical role in cancer of these two closely related amino acids. We analyzed the response to three conditions: methionine depletion, methionine replacement with homocysteine, and cysteine depletion. In cancer cells, the transcription factor ATF4 was induced by all three tested conditions. The replacement of methionine with homocysteine produced a strong ferroptotic gene signature. We also detected an activation of the NRF2 antioxidant pathway by both methionine and cysteine depletion. Total glutathione levels were decreased by 42% in melanoma cells grown without methionine, and by 95% in cells grown without cysteine. Lipid peroxidation was increased in cells grown without cysteine, but not in cells grown without methionine. Despite the large degree of overlap in gene expression between methionine and cysteine depletion, methionine depletion and replacement of methionine with homocysteine was associated with apoptosis while cysteine depletion was associated with ferroptosis. Glutamine depletion produced comparable gene expression patterns and was associated with a 28% decrease in glutathione. Apoptosis was detected in these cells. In this experiment, a strong ATF4-driven ferroptotic gene signature was insufficient to induce ferroptosis without a concomitant profound decrease in glutathione levels.
    DOI:  https://doi.org/10.1002/em.22428
  6. Free Radic Biol Med. 2021 Feb 23. pii: S0891-5849(21)00108-8. [Epub ahead of print]
    Oxidative stress-mediated AMPK inactivation determines the high susceptibility of LKB1-mutant NSCLC cells to glucose starvation.
    Yi Ren, Jiaqing Chen, Peishi Chen, Qi Hao, Leng-Kuan Cheong, Mingzhu Tang, Lian-Lian Hong, Xuan-Yu Hu, Celestial T Yap, Boon-Huat Bay, Zhi-Qiang Ling, Han-Ming Shen.
      The liver kinase B1 (LKB1) is an important tumor suppressor and its loss-of-function mutations are observed in around 16% of non-small cell lung cancer (NSCLC) cases. One of the main functions of LKB1 is to activate AMP-activated protein kinase (AMPK) via direct phosphorylation. Under metabolic or energy stress conditions, the LKB1-AMPK axis inhibits the anabolic pathways and activates the catabolic pathways to maintain metabolic homeostasis for cell survival. In this study, we found that LKB1-mutant NSCLC cells are particularly susceptible to cell death induced by glucose starvation, but not by other forms of starvation such as amino acid starvation or serum starvation. Reconstitution of LKB1 in LKB1-mutant cells or LKB1 knockout in LKB1-wild type cells highlighted the importance of the LKB1-AMPK axis for cell survival under glucose starvation. Mechanistically, in LKB1-mutant cells, glucose starvation elicits oxidative stress, which causes AMPK protein oxidation and inactivation, and eventually cell death. Importantly, this process could be effectively reversed and rescued by 2DG (a glucose analog capable of producing NADPH, a key antioxidant), A769662 (an allosteric AMPK activator), and N-acetyl cysteine (NAC) (a ROS scavenger), indicating the presence of a vicious circle between AMPK inactivation and ROS in LKB1-mutant NSCLC cells under glucose starvation. Our study thus elucidates the critical role of redox balance in determining the susceptibility to cell death under glucose starvation in LKB1-mutant NSCLC cells. The findings from this study reveal important clues in search of novel therapeutic strategies for LKB1-mutant NSCLC by targeting glucose metabolism and redox balance.
    Keywords:  AMP-activated protein kinase; glucose starvation; liver kinase B1; non-small cell lung cancer; reactive oxygen species
    DOI:  https://doi.org/10.1016/j.freeradbiomed.2021.02.018
  7. Sci Transl Med. 2021 Feb 24. pii: eabd6299. [Epub ahead of print]13(582):
    Mechanism and reversal of drug-induced nephrotoxicity on a chip.
    Aaron Cohen, Konstantinos Ioannidis, Avner Ehrlich, Shaun Regenbaum, Merav Cohen, Muneef Ayyash, Sigal Shafran Tikva, Yaakov Nahmias.
      The kidney plays a critical role in fluid homeostasis, glucose control, and drug excretion. Loss of kidney function due to drug-induced nephrotoxicity affects over 20% of the adult population. The kidney proximal tubule is a complex vascularized structure that is particularly vulnerable to drug-induced nephrotoxicity. Here, we introduce a model of vascularized human kidney spheroids with integrated tissue-embedded microsensors for oxygen, glucose, lactate, and glutamine, providing real-time assessment of cellular metabolism. Our model shows that both the immunosuppressive drug cyclosporine and the anticancer drug cisplatin disrupt proximal tubule polarity at subtoxic concentrations, leading to glucose accumulation and lipotoxicity. Impeding glucose reabsorption using glucose transport inhibitors blocked cyclosporine and cisplatin toxicity by 1000- to 3-fold, respectively. Retrospective study of 247 patients who were diagnosed with kidney damage receiving cyclosporine or cisplatin in combination with the sodium-glucose cotransporter-2 (SGLT2) inhibitor empagliflozin showed significant (P < 0.001) improvement of kidney function, as well as reduction in creatinine and uric acid, markers of kidney damage. These results demonstrate the potential of sensor-integrated kidney-on-chip platforms to elucidate mechanisms of action and rapidly reformulate effective therapeutic solutions, increasing drug safety and reducing the cost of clinical and commercial failures.
    DOI:  https://doi.org/10.1126/scitranslmed.abd6299
  8. Nat Commun. 2021 02 22. 12(1): 1209
    Fructose reprogrammes glutamine-dependent oxidative metabolism to support LPS-induced inflammation.
    Nicholas Jones, Julianna Blagih, Fabio Zani, April Rees, David G Hill, Benjamin J Jenkins, Caroline J Bull, Diana Moreira, Azari I M Bantan, James G Cronin, Daniele Avancini, Gareth W Jones, David K Finlay, Karen H Vousden, Emma E Vincent, Catherine A Thornton.
      Fructose intake has increased substantially throughout the developed world and is associated with obesity, type 2 diabetes and non-alcoholic fatty liver disease. Currently, our understanding of the metabolic and mechanistic implications for immune cells, such as monocytes and macrophages, exposed to elevated levels of dietary fructose is limited. Here, we show that fructose reprograms cellular metabolic pathways to favour glutaminolysis and oxidative metabolism, which are required to support increased inflammatory cytokine production in both LPS-treated human monocytes and mouse macrophages. A fructose-dependent increase in mTORC1 activity drives translation of pro-inflammatory cytokines in response to LPS. LPS-stimulated monocytes treated with fructose rely heavily on oxidative metabolism and have reduced flexibility in response to both glycolytic and mitochondrial inhibition, suggesting glycolysis and oxidative metabolism are inextricably coupled in these cells. The physiological implications of fructose exposure are demonstrated in a model of LPS-induced systemic inflammation, with mice exposed to fructose having increased levels of circulating IL-1β after LPS challenge. Taken together, our work underpins a pro-inflammatory role for dietary fructose in LPS-stimulated mononuclear phagocytes which occurs at the expense of metabolic flexibility.
    DOI:  https://doi.org/10.1038/s41467-021-21461-4
  9. Front Immunol. 2020 ;11 623989
    Dietary Intervention Impacts Immune Cell Functions and Dynamics by Inducing Metabolic Rewiring.
    Takuma Okawa, Motoyoshi Nagai, Koji Hase.
      Accumulating evidence has shown that nutrient metabolism is closely associated with the differentiation and functions of various immune cells. Cellular metabolism, including aerobic glycolysis, fatty acid oxidation, and oxidative phosphorylation, plays a key role in germinal center (GC) reaction, B-cell trafficking, and T-cell-fate decision. Furthermore, a quiescent metabolic status consolidates T-cell-dependent immunological memory. Therefore, dietary interventions such as calorie restriction, time-restricted feeding, and fasting potentially manipulate immune cell functions. For instance, intermittent fasting prevents the development of experimental autoimmune encephalomyelitis. Meanwhile, the fasting response diminishes the lymphocyte pool in gut-associated lymphoid tissue to minimize energy expenditure, leading to the attenuation of Immunoglobulin A (IgA) response. The nutritional status also influences the dynamics of several immune cell subsets. Here, we describe the current understanding of the significance of immunometabolism in the differentiation and functionality of lymphocytes and macrophages. The underlying molecular mechanisms also are discussed. These experimental observations could offer new therapeutic strategies for immunological disorders like autoimmunity.
    Keywords:  AMPK; GCN2; calorie restriction; dietary intervention; fasting; mTOR; metabolic rewiring
    DOI:  https://doi.org/10.3389/fimmu.2020.623989
  10. NMR Biomed. 2021 Feb;34(2): e4453
    An investigation of glutamate quantification with PRESS and MEGA-PRESS.
    Hu Cheng, Amanda Wang, Sharlene Newman, Ulrike Dydak.
      Glutamate is an important neurotransmitter. Although many studies have measured glutamate concentration in vivo using magnetic resonance spectroscopy (MRS), researchers have not reached a consensus on the accuracy of glutamate quantification at the field strength of 3 T. Besides, there is not an optimal MRS protocol for glutamate measurement. In this work, both simulation and phantom scans indicate that glutamate can be estimated with reasonable accuracy (<10% error on average) using the standard Point-RESolved Spectroscopy (PRESS) technique with TE 30 ms; glutamine, however, is likely underestimated, which is also suggested by results from human scans using the same protocol. The phantom results show an underestimation of glutamate and glutamine for PRESS with long TE and MEGA-PRESS off-resonance spectra. Despite the underestimation, there is a high correlation between the measured values and the true values (r > 0.8). Our results suggest that the quantification of glutamate and glutamine is reliable but can be off by a scaling factor, depending on the imaging technique. The outputs from all three PRESS sequences (TE = 30, 68 and 80 ms) are also highly correlated with each other (r > 0.7) and moderately correlated (r > 0.5) with the results from the MEGA-PRESS difference spectra with moderate to good shimming (linewidth < 16 Hz).
    Keywords:  MEGA‐PRESS; MRS; PRESS; glutamate; phantom; simulation
    DOI:  https://doi.org/10.1002/nbm.4453
  11. Cell. 2021 Feb 22. pii: S0092-8674(21)00171-9. [Epub ahead of print]
    In vivo CRISPR screening reveals nutrient signaling processes underpinning CD8+ T cell fate decisions.
    Hongling Huang, Peipei Zhou, Jun Wei, Lingyun Long, Hao Shi, Yogesh Dhungana, Nicole M Chapman, Guotong Fu, Jordy Saravia, Jana L Raynor, Shaofeng Liu, Gustavo Palacios, Yong-Dong Wang, Chenxi Qian, Jiyang Yu, Hongbo Chi.
      How early events in effector T cell (TEFF) subsets tune memory T cell (TMEM) responses remains incompletely understood. Here, we systematically investigated metabolic factors in fate determination of TEFF and TMEM cells using in vivo pooled CRISPR screening, focusing on negative regulators of TMEM responses. We found that amino acid transporters Slc7a1 and Slc38a2 dampened the magnitude of TMEM differentiation, in part through modulating mTORC1 signaling. By integrating genetic and systems approaches, we identified cellular and metabolic heterogeneity among TEFF cells, with terminal effector differentiation associated with establishment of metabolic quiescence and exit from the cell cycle. Importantly, Pofut1 (protein-O-fucosyltransferase-1) linked GDP-fucose availability to downstream Notch-Rbpj signaling, and perturbation of this nutrient signaling axis blocked terminal effector differentiation but drove context-dependent TEFF proliferation and TMEM development. Our study establishes that nutrient uptake and signaling are key determinants of T cell fate and shape the quantity and quality of TMEM responses.
    Keywords:  GDP-fucose; Notch; T cell memory; cell cycle exit; immunometabolism; in vivo pooled CRISPR screening; metabolic heterogeneity; nutrient signaling; systems immunology; terminal effector cell
    DOI:  https://doi.org/10.1016/j.cell.2021.02.021
  12. Biochem Soc Trans. 2021 Feb 22. pii: BST20190008. [Epub ahead of print]
    One-carbon metabolism in cancer cells: a critical review based on a core model of central metabolism.
    Jean-Pierre Mazat.
      One-carbon metabolism (1C-metabolism), also called folate metabolism because the carbon group is attached to folate-derived tetrahydrofolate, is crucial in metabolism. It is at the heart of several essential syntheses, particularly those of purine and thymidylate. After a short reminder of the organization of 1C-metabolism, I list its salient features as reported in the literature. Then, using flux balance analysis, a core model of central metabolism and the flux constraints for an 'average cancer cell metabolism', I explore the fundamentals underlying 1C-metabolism and its relationships with the rest of metabolism. Some unreported properties of 1C-metabolism emerge, such as its potential roles in mitochondrial NADH exchange with cytosolic NADPH, participation in NADH recycling, and optimization of cell proliferation.
    Keywords:  average cancer cell; cancer cells’ metabolism; flux balance analysis; metabolic model; one-carbon metabolism
    DOI:  https://doi.org/10.1042/BST20190008
  13. Sci Rep. 2021 Feb 24. 11(1): 4480
    Transketolase regulates sensitivity to APR-246 in p53-null cells independently of oxidative stress modulation.
    Julia V Milne, Bonnie Z Zhang, Kenji M Fujihara, Swati Dawar, Wayne A Phillips, Nicholas J Clemons.
      The prevalence and dire implications of mutations in the tumour suppressor, p53, highlight its appeal as a chemotherapeutic target. We recently showed that impairing cellular antioxidant systems via inhibition of SLC7A11, a component of the system xc- cystine-glutamate antiporter, enhances sensitivity to mutant-p53 targeted therapy, APR-246. We investigated whether this synergy extends to other genes, such as those encoding enzymes of the pentose phosphate pathway (PPP). TKT, one of the major enzymes of the PPP, is allegedly regulated by NRF2, which is in turn impaired by accumulated mutant-p53 protein. Therefore, we investigated the relationship between mutant-p53, TKT and sensitivity to APR-246. We found that mutant-p53 does not alter expression of TKT, nor is TKT modulated directly by NRF2, suggesting a more complex mechanism at play. Furthermore, we found that in p53null cells, knockdown of TKT increased sensitivity to APR-246, whilst TKT overexpression conferred resistance to the drug. However, neither permutation elicited any effect on cells overexpressing mutant-p53 protein, despite mediating oxidative stress levels in a similar fashion to that in p53-null cells. In sum, this study has unveiled TKT expression as a determinant for sensitivity to APR-246 in p53-null cells.
    DOI:  https://doi.org/10.1038/s41598-021-83979-3
  14. Cell Metab. 2021 Feb 17. pii: S1550-4131(21)00057-7. [Epub ahead of print]
    Asparagine couples mitochondrial respiration to ATF4 activity and tumor growth.
    Abigail S Krall, Peter J Mullen, Felicia Surjono, Milica Momcilovic, Ernst W Schmid, Christopher J Halbrook, Apisadaporn Thambundit, Steven D Mittelman, Costas A Lyssiotis, David B Shackelford, Simon R V Knott, Heather R Christofk.
      Mitochondrial respiration is critical for cell proliferation. In addition to producing ATP, respiration generates biosynthetic precursors, such as aspartate, an essential substrate for nucleotide synthesis. Here, we show that in addition to depleting intracellular aspartate, electron transport chain (ETC) inhibition depletes aspartate-derived asparagine, increases ATF4 levels, and impairs mTOR complex I (mTORC1) activity. Exogenous asparagine restores proliferation, ATF4 and mTORC1 activities, and mTORC1-dependent nucleotide synthesis in the context of ETC inhibition, suggesting that asparagine communicates active respiration to ATF4 and mTORC1. Finally, we show that combination of the ETC inhibitor metformin, which limits tumor asparagine synthesis, and either asparaginase or dietary asparagine restriction, which limit tumor asparagine consumption, effectively impairs tumor growth in multiple mouse models of cancer. Because environmental asparagine is sufficient to restore tumor growth in the context of respiration impairment, our findings suggest that asparagine synthesis is a fundamental purpose of tumor mitochondrial respiration, which can be harnessed for therapeutic benefit to cancer patients.
    Keywords:  asparaginase; asparagine; cancer metabolism; cancer treatment; dietary restriction; metformin; respiration
    DOI:  https://doi.org/10.1016/j.cmet.2021.02.001
  15. Eur Rev Med Pharmacol Sci. 2021 Feb;pii: 24876. [Epub ahead of print]25(3): 1650-1662
    Insights into the novel function of system Xc- in regulated cell death.
    H Tu, L-J Tang, X-J Luo, K-L Ai, J Peng.
      System Xc-, also named cystine/glutamate antiporter, is an important intracellular antioxidant element. It is composed of the light chain SLC7A11 (xCT) and the heavy chain SLC3A2 (4F2hc) and functions as raw materials for the synthesis of glutathione (GSH). Recent studies have demonstrated that system Xc- plays an important role in different types of regulated cell death, which is referred to cell death controlled by dedicated molecular machinery. It has been shown that system Xc- involves in ferroptosis, apoptosis, and autophagy-dependent cell death, contributing to different diseases and drug resistance, such as cancer, neurological disorders, and cisplatin resistance to cancers. To date, the intervention of system Xc- by its inhibitors or activators displays a beneficial effect on the treatment of certain diseases. In this review, we summarize recent findings on the role of system Xc- in regulated cell death, including molecular mechanisms and potential therapeutic applications.
    DOI:  https://doi.org/10.26355/eurrev_202102_24876
  16. Anal Chem. 2021 Feb 24.
    Glutathione Content Detection of Single Cells under Ingested Doxorubicin by Functionalized Glass Nanopores.
    Ping Hu, Ying Zhang, Dandan Wang, Guohua Qi, Yongdong Jin.
      Glutathione (GSH) level in cells maintains redox homeostasis, so the detection of intracellular GSH is crucial for many pathological processes. In the present study, we developed a cystamine-functionalized glass nanopore (cG-nanopore) for the specific detection of GSH in single cells through the Michael addition reaction between the amino group of cystamine and polydopamine adhered to the inner wall of the glass nanopore. The cellular GSH will cleave the disulfide bond of cystamine and induce a negative charge increase on the residual surface of the modified nanopore, thus producing a sensitive response on the current-voltage curves. The developed sensing platform showed a good response relationship with the GSH concentration and an excellent selectivity against interfering substances in cells. The variation of GSH content in single HeLa and H8 cells incubated with DOX was then further quantified by this method.
    DOI:  https://doi.org/10.1021/acs.analchem.0c05004
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