bims-glucam 2024-08-04 papers

bims-glucam

Biomed News

on Glutamine cancer metabolism

Issue of 2024–08–04
fiveteen papers selected by
Sreeparna Banerjee, Middle East Technical University

Targeting YAP Activity and Glutamine Metabolism Cooperatively Suppresses Tumor Progression by Preventing Extracellular Matrix Accumulation.
Glutaminolysis is a Potential Therapeutic Target for Kidney Diseases.
ASCT2 is a major contributor to serine uptake in cancer cells.
The Glucose-Glutamine Metabolic Interplay in MCF-7 Cells, a Hormone-Sensitive Breast Cancer Model.
Stable isotope-resolved metabolomics analyses of metabolic phenotypes reveal variable glutamine metabolism in different patient-derived models of non-small cell lung cancer from a single patient.
Isocitrate dehydrogenases 2-mediated dysfunctional metabolic reprogramming promotes intestinal cancer progression via regulating HIF-1A signaling pathway.
The Warburg Effect Revisited through Blood and Electron Flow.
The significant role of amino acid metabolic reprogramming in cancer.
Hypoxia-induced cysteine metabolism reprogramming is crucial for the tumorigenesis of colorectal cancer.
Unresolved questions regarding cellular cysteine sources and their possible relationships to ferroptosis.
Glutathione overproduction mediates lymphoma initiating cells survival and has a sex-dependent effect on lymphomagenesis.
Glutamine deprivation in glioblastoma stem cells triggers autophagic SIRT3 degradation to epigenetically restrict CD133 expression and stemness.
Structural basis of the obligatory exchange mode of human neutral amino acid transporter ASCT2.
mTORC2-driven chromatin cGAS mediates chemoresistance through epigenetic reprogramming in colorectal cancer.
ABCC2 induces metabolic vulnerability and cellular ferroptosis via enhanced glutathione efflux in gastric cancer.

Cancer Res. 2024 Jul 29.

Targeting YAP Activity and Glutamine Metabolism Cooperatively Suppresses Tumor Progression by Preventing Extracellular Matrix Accumulation.

Mihyang Park, Jonghwa Jin, Da Young An, Dong-Ho Kim, Jaebon Lee, Jae Won Yun, Ilseon Hwang, Jae Seok Park, Mi Kyung Kim, You Mie Lee, Jun-Kyu Byun, Yeon-Kyung Choi, Keun-Gyu Park.

Cancer cells use multiple mechanisms to evade the effects of glutamine metabolism inhibitors. The pathways that govern responses to alterations in glutamine availability within the tumor may represent therapeutic targets for combinatorial strategies with these inhibitors. Here, we showed that targeting glutamine utilization stimulated Yes-associated protein (YAP) signaling in cancer cells by reducing cyclic adenosine monophosphate (cAMP)/protein kinase A (PKA)-dependent phosphorylation of large tumor suppressor (LATS). Elevated YAP activation induced extracellular matrix (ECM) deposition by increasing secretion of connective tissue growth factor (CTGF) that promoted production of fibronectin and collagen by surrounding fibroblasts. Consequently, inhibiting YAP synergized with inhibition of glutamine utilization to effectively suppress tumor growth in vivo, along with a concurrent decrease in ECM deposition. Blocking ECM remodeling also augmented the tumor suppressive effects of the glutamine utilization inhibitor. Collectively, these data reveal mechanisms by which targeting glutamine utilization increases ECM accumulation and identify potential strategies to reduce ECM levels and increase the efficacy of glutamine metabolism inhibitors.

DOI: https://doi.org/10.1158/0008-5472.CAN-23-3933
Diabetes Metab Syndr Obes. 2024 ;17 2789-2807

Glutaminolysis is a Potential Therapeutic Target for Kidney Diseases.

Li-Ping Ou, Yong-Jian Liu, Shi-Tong Qiu, Chen Yang, Ji-Xin Tang, Xiao-Yu Li, Hua-Feng Liu, Zhen-Nan Ye.

  Metabolic reprogramming contributes to the progression and prognosis of various kidney diseases. Glutamine is the most abundant free amino acid in the body and participates in more metabolic processes than other amino acids. Altered glutamine metabolism is a prominent feature in different kidney diseases. Glutaminolysis converts glutamine into the TCA cycle metabolite, alpha-ketoglutarate, via a cascade of enzymatic reactions. This metabolic pathway plays pivotal roles in inflammation, maladaptive repair, cell survival and proliferation, redox homeostasis, and immune regulation. Given the crucial role of glutaminolysis in bioenergetics and anaplerotic fluxes in kidney pathogenesis, studies on this cascade could provide a better understanding of kidney diseases, thus inspiring the development of potential methods for targeted therapy. Emerging evidence has shown that targeting glutaminolysis is a promising therapeutic strategy for ameliorating kidney disease. In this narrative review, equation including keywords related to glutamine, glutaminolysis and kidney are subjected to an exhaustive search on Pubmed database, we identified all relevant articles published before 1 April, 2024. Afterwards, we summarize the regulation of glutaminolysis in major kidney diseases and its underlying molecular mechanisms. Furthermore, we highlight therapeutic strategies targeting glutaminolysis and their potential clinical applications.

Keywords:  glutamine; glutaminolysis; kidney diseases; therapeutic target

DOI:  https://doi.org/10.2147/DMSO.S471711
Cell Rep. 2024 Jul 26. pii: S2211-1247(24)00881-7. [Epub ahead of print]43(8): 114552

ASCT2 is a major contributor to serine uptake in cancer cells.

Kelly O Conger, Christopher Chidley, Mete Emir Ozgurses, Huiping Zhao, Yumi Kim, Svetlana E Semina, Philippa Burns, Vipin Rawat, Lina Lietuvninkas, Ryan Sheldon, Issam Ben-Sahra, Jonna Frasor, Peter K Sorger, Gina M DeNicola, Jonathan L Coloff.

  The non-essential amino acid serine is a critical nutrient for cancer cells due to its diverse biosynthetic functions. While some tumors can synthesize serine de novo, others are auxotrophic and therefore reliant on serine uptake. Importantly, despite several transporters being known to be capable of transporting serine, the transporters that mediate serine uptake in cancer cells are not known. Here, we characterize the amino acid transporter ASCT2 (SLC1A5) as a major contributor to serine uptake in cancer cells. ASCT2 is well known as a glutamine transporter in cancer, and our work demonstrates that serine and glutamine compete for uptake through ASCT2. We further show that ASCT2-mediated serine uptake is essential for purine nucleotide biosynthesis and that estrogen receptor α (ERα) promotes serine uptake by directly activating SLC1A5 transcription. Collectively, our work defines an additional important role for ASCT2 as a serine transporter in cancer and evaluates ASCT2 as a potential therapeutic target.

Keywords:  ASCT2; CP: Cancer; ERα; SLC1A5; amino acid uptake; breast cancer; cancer metabolism; diet; purine biosynthesis; serine starvation; serine transporter

DOI:  https://doi.org/10.1016/j.celrep.2024.114552
Front Biosci (Landmark Ed). 2024 Jul 16. 29(7): 251

The Glucose-Glutamine Metabolic Interplay in MCF-7 Cells, a Hormone-Sensitive Breast Cancer Model.

Sonia Carta, Maddalena Ghelardoni, Francesca Vitale, Silvia Ravera, Vanessa Cossu, Nadia Bertola, Serena Losacco, Jonathan Martinelli, Edoardo Dighero, Mattia Riondato, Anna Maria Orengo, Matteo Bauckneht, Sabrina Chiesa, Gianmario Sambuceti, Cecilia Marini.

   BACKGROUND: Selective deprivation of glutamine has been shown to accelerate the generation of reactive oxygen species (ROS) and to impair the activity of a specific pentose phosphate pathway (PPP) located within the endoplasmic reticulum (ER). The consequent oxidative damage suggests that glucose flux through this reticular pathway might contribute to the redox stress of breast cancer cells. We thus evaluated whether this response is reproduced when the glutamine shortage is coupled with the glucose deprivation.
METHODS: Cancer growth, metabolic plasticity and redox status were evaluated under saturating conditions and after 48 h starvation (glucose 2.5 mM, glutamine 0.5 mM). The Seahorse technology was used to estimate adenosine triphosphate (ATP)-linked and ATP-independent oxygen consumption rate (OCR) as well as proton efflux rate (PER). 18F-fluoro-deoxy-glucose (FDG) uptake was evaluated through the LigandTracer device. Proliferation rate was estimated by the carboxyfluorescein-diacetate-succinimidyl ester (CFSE) staining, while cell viability by the propidium iodide exclusion assay.
RESULTS: Starvation reduced the proliferation rate of MCF-7 cells without affecting their viability. It also decreased lactate release and PER. Overall OCR was left unchanged although ATP-synthase dependent fraction was increased under nutrient shortage. Glutaminolysis inhibition selectively impaired the ATP-independent and the oligomycin-sensitive OCR in control and starved cultures, respectively. The combined nutrient shortage decreased the cytosolic and mitochondrial markers of redox stress. It also left unchanged the expression of the reticular unfolded protein marker GRP78. By contrast, starvation decreased the expression of hexose-6P-dehydrogenase (H6PD) thus decreasing the glucose flux through the ER-PPP as documented by the profound impairment in the uptake rate of FDG.
CONCLUSIONS: When combined with glucose deprivation, glutamine shortage does not elicit the expected enhancement of ROS generation in the studied breast cancer cell line. Combined with the decreased activity of ER-PPP, this observation suggests that glutamine interferes with the reticular glucose metabolism to regulate the cell redox balance.

Keywords:  NADPH; cytosolic/reticular pentose phosphate pathway; glucose and glutamine metabolism; glucose-6-phosphate dehydrogenase; hexose-6-phosphate-dehydrogenase; hormone-sensitive breast cancer; redox status

DOI:  https://doi.org/10.31083/j.fbl2907251
Metabolomics. 2024 Jul 27. 20(4): 87

Stable isotope-resolved metabolomics analyses of metabolic phenotypes reveal variable glutamine metabolism in different patient-derived models of non-small cell lung cancer from a single patient.

Connor J Kinslow, Michael Bousamra Ll, Yihua Cai, Jun Yan, Pawel K Lorkiewicz, Ahmad Al-Attar, Jinlian Tan, Richard M Higashi, Andrew N Lane, Teresa W-M Fan.

   INTRODUCTION: Stable isotope tracers have been increasingly used in preclinical cancer model systems, including cell culture and mouse xenografts, to probe the altered metabolism of a variety of cancers, such as accelerated glycolysis and glutaminolysis and generation of oncometabolites. Comparatively little has been reported on the fidelity of the different preclinical model systems in recapitulating the aberrant metabolism of tumors.
OBJECTIVES: We have been developing several different experimental model systems for systems biochemistry analyses of non-small cell lung cancer (NSCLC1) using patient-derived tissues to evaluate appropriate models for metabolic and phenotypic analyses.
METHODS: To address the issue of fidelity, we have carried out a detailed Stable Isotope-Resolved Metabolomics study of freshly resected tissue slices, mouse patient derived xenografts (PDXs), and cells derived from a single patient using both 13C6-glucose and 13C5,15N2-glutamine tracers.
RESULTS: Although we found similar glucose metabolism in the three models, glutamine utilization was markedly higher in the isolated cell culture and in cell culture-derived xenografts compared with the primary cancer tissue or direct tissue xenografts (PDX).
CONCLUSIONS: This suggests that caution is needed in interpreting cancer biochemistry using patient-derived cancer cells in vitro or in xenografts, even at very early passage, and that direct analysis of patient derived tissue slices provides the optimal model for ex vivo metabolomics. Further research is needed to determine the generality of these observations.

Keywords:  Cancer metabolism; Non-small cell lung cancer; Patient-derived xenografts; Preclinical models; Primary cell culture; Stable isotope-resolved metabolomics

DOI:  https://doi.org/10.1007/s11306-024-02126-x
Int Immunopharmacol. 2024 Aug 01. pii: S1567-5769(24)01349-3. [Epub ahead of print]140 112828

Isocitrate dehydrogenases 2-mediated dysfunctional metabolic reprogramming promotes intestinal cancer progression via regulating HIF-1A signaling pathway.

Shixiong Liu, Yun Zhou, Yarong Chen, Yuqin Qiao, Lumucao Bai, Shenhua Zhang, Dongfang Men, Haibu Zhang, Fen Pan, Yongshen Gao, Jijing Wang, Yuping Wang.

  Changes in isocitrate dehydrogenases (IDH) lead to the production of the cancer-causing metabolite 2-hydroxyglutarate, making them a cause of cancer. However, the specific role of IDH in the progression of colon cancer is still not well understood. Our current study provides evidence that IDH2 is significantly increased in colorectal cancer (CRC) cells and actively promotes cell growth in vitro and the development of tumors in vivo. Inhibiting the activity of IDH2, either through genetic silencing or pharmacological inhibition, results in a significant increase in α-ketoglutarate (α-KG), indicating a decrease in the reductive citric acid cycle. The excessive accumulation of α-KG caused by the inactivation of IDH2 obstructs the generation of ATP in mitochondria and promotes the downregulation of HIF-1A, eventually inhibiting glycolysis. This dual metabolic impact results in a reduction in ATP levels and the suppression of tumor growth. Our study reveals a metabolic trait of colorectal cancer cells, which involves the active utilization of glutamine through reductive citric acid cycle metabolism. The data suggests that IDH2 plays a crucial role in this metabolic process and has the potential to be a valuable target for the advancement of treatments for colorectal cancer.

Keywords:  Citric acid cycle; Colorectal cancer; Glycolysis; Isocitrate dehydrogenases; α-ketoglutarate

DOI:  https://doi.org/10.1016/j.intimp.2024.112828
Cancer Res. 2024 Jul 02. 84(13): 2046-2048

The Warburg Effect Revisited through Blood and Electron Flow.

Yahui Wang, Chi V Dang.

The Warburg effect describes the propensity of many cancers to consume glucose avidly and convert it to lactate in the presence of oxygen. The benefit of the Warburg effect on cancer cells remains enigmatic, particularly because extracellular disposal of incompletely oxidized lactate is wasteful. However, lactate is not discarded from the body, but rather recycled as pyruvate for metabolism through the tricarboxylic acid cycle in oxidative tissues and cells. Hence, tissue and interorgan metabolism play important roles in tumor metabolism. The production of tumor lactate to be recycled elsewhere parallels the Cori cycle, in which lactate produced by muscle activity is shuttled to the liver, where it is converted to pyruvate and subsequently stored as glucose moieties in glycogen. This perspective will consider this organismal contextwhile discussing how glucose is used in tumors. We highlight several key articles published decades ago in Cancer Research that are foundational to our current understanding of cancer biology and metabolism.

DOI: https://doi.org/10.1158/0008-5472.CAN-24-0474
Cell Commun Signal. 2024 Jul 29. 22(1): 380

The significant role of amino acid metabolic reprogramming in cancer.

Xiaohong Liu, Bo Ren, Jie Ren, Minzhi Gu, Lei You, Yupei Zhao.

  Amino acid metabolism plays a pivotal role in tumor microenvironment, influencing various aspects of cancer progression. The metabolic reprogramming of amino acids in tumor cells is intricately linked to protein synthesis, nucleotide synthesis, modulation of signaling pathways, regulation of tumor cell metabolism, maintenance of oxidative stress homeostasis, and epigenetic modifications. Furthermore, the dysregulation of amino acid metabolism also impacts tumor microenvironment and tumor immunity. Amino acids can act as signaling molecules that modulate immune cell function and immune tolerance within the tumor microenvironment, reshaping the anti-tumor immune response and promoting immune evasion by cancer cells. Moreover, amino acid metabolism can influence the behavior of stromal cells, such as cancer-associated fibroblasts, regulate ECM remodeling and promote angiogenesis, thereby facilitating tumor growth and metastasis. Understanding the intricate interplay between amino acid metabolism and the tumor microenvironment is of crucial significance. Expanding our knowledge of the multifaceted roles of amino acid metabolism in tumor microenvironment holds significant promise for the development of more effective cancer therapies aimed at disrupting the metabolic dependencies of cancer cells and modulating the tumor microenvironment to enhance anti-tumor immune responses and inhibit tumor progression.

Keywords:  Amino acid metabolism; Angiogenesis; Epigenetic regulation; Immune tolerance; Redox; Tumor microenvironment

DOI:  https://doi.org/10.1186/s12964-024-01760-1
Redox Biol. 2024 Jul 26. pii: S2213-2317(24)00264-7. [Epub ahead of print]75 103286

Hypoxia-induced cysteine metabolism reprogramming is crucial for the tumorigenesis of colorectal cancer.

Zhang Lin, Shiyi Yang, Qianqian Qiu, Gaoping Cui, Yanhua Zhang, Meilian Yao, Xiangyu Li, Chengkun Chen, Jun Gu, Ting Wang, Peng Yin, Longci Sun, Yujun Hao.

  Metabolic reprogramming is a hallmark of human cancer, and cancer-specific metabolism provides opportunities for cancer diagnosis, prognosis, and treatment. However, the underlying mechanisms by which metabolic pathways affect the initiation and progression of colorectal cancer (CRC) remain largely unknown. Here, we demonstrate that cysteine is highly enriched in colorectal tumors compared to adjacent non-tumor tissues, thereby promoting tumorigenesis of CRC. Synchronously importing both cysteine and cystine in colorectal cancer cells is necessary to maintain intracellular cysteine levels. Hypoxia-induced reactive oxygen species (ROS) and ER stress regulate the co-upregulation of genes encoding cystine transporters (SLC7A11, SLC3A2) and genes encoding cysteine transporters (SLC1A4, SLC1A5) through the transcription factor ATF4. Furthermore, the metabolic flux from cysteine to reduced glutathione (GSH), which is critical to support CRC growth, is increased due to overexpression of glutathione synthetase GSS in CRC. Depletion of cystine/cysteine by recombinant cyst(e)inase effectively inhibits the growth of colorectal tumors by inducing autophagy in colorectal cancer cells through mTOR-ULK signaling axis. This study demonstrates the underlying mechanisms of cysteine metabolism in tumorigenesis of CRC, and evaluates the potential of cysteine metabolism as a biomarker or a therapeutic target for CRC.

Keywords:  ATF4; Colorectal cancer; Cysteine/cystine; Hypoxia; ROS homeostasis; Transporter genes

DOI:  https://doi.org/10.1016/j.redox.2024.103286
Adv Cancer Res. 2024 ;pii: S0065-230X(24)00001-0. [Epub ahead of print]162 1-44

Unresolved questions regarding cellular cysteine sources and their possible relationships to ferroptosis.

Elias S J Arnér, Edward E Schmidt.

  Cysteine is required for synthesis of glutathione (GSH), coenzyme A, other sulfur-containing metabolites, and most proteins. In most cells, cysteine comes from extracellular disulfide sources including cystine, glutathione-disulfide, and peptides. The thioredoxin reductase-1 (TrxR1)- or glutathione-disulfide reductase (GSR)-driven enzymatic systems can fuel cystine reduction via thioredoxins, glutaredoxins, or other thioredoxin-fold proteins. Free cystine enters cells thorough the cystine-glutamate antiporter, xCT, but systemically, plasma glutathione-disulfide might predominate as a cystine source. Erastin, inhibiting both xCT and voltage-dependent anion channels, induces ferroptotic cell death, so named because this type of cell death is antagonized by iron-chelators. Many cancer cells seem to be predisposed to ferroptosis, which has been proposed as a targetable cancer liability. Ferroptosis is associated with lipid peroxidation and loss of either glutathione peroxidase-4 (GPX4) or ferroptosis suppressor protein-1 (FSP1), which each prevent accumulation of lipid peroxides. It has been suggested that an xCT inhibition-induced cellular cysteine-deficiency lowers GSH levels, starving GPX4 for reducing power and allowing membrane lipid peroxides to accumulate, thereby causing ferroptosis. Aspects of ferroptosis are however not fully understood and need to be further scrutinized, for example that neither disruption of GSH synthesis, loss of GSH, nor disruption of glutathione disulfide reductase (GSR), triggers ferroptosis in animal models. Here we reevaluate the relationships between Erastin, xCT, GPX4, cellular cysteine and GSH, RSL3 or ML162, and ferroptosis. We conclude that, whereas both Cys and ferroptosis are potential liabilities in cancer, their relationship to each other remains insufficiently understood.

Keywords:  Cysteine; Cystine; Disulfide reduction; Erastin; Ferroptosis; Glutathione; Glutathione peroxidase 4; Iron; Lipid peroxide; RSL3

DOI:  https://doi.org/10.1016/bs.acr.2024.04.001
Cell Death Dis. 2024 Jul 27. 15(7): 534

Glutathione overproduction mediates lymphoma initiating cells survival and has a sex-dependent effect on lymphomagenesis.

Alberto H-Alcántara, Omar Kourani, Ana Marcos-Jiménez, Patricia Martínez-Núñez, Estela Herranz-Martín, Patricia Fuentes, María L Toribio, Cecilia Muñoz-Calleja, Teresa Iglesias, Miguel R Campanero.

Lymphoid tumor patients often exhibit resistance to standard therapies or experience relapse post-remission. Relapse is driven by Tumor Initiating Cells (TICs), a subset of tumor cells capable of regrowing the tumor and highly resistant to therapy. Growing cells in 3D gels is a method to discern tumorigenic cells because it strongly correlates with tumorigenicity. The finding that TICs, rather than differentiated tumor cells, grow in 3D gels offers a unique opportunity to unveil TIC-specific signaling pathways and therapeutic targets common to various cancer types. Here, we show that culturing lymphoid cells in 3D gels triggers reactive oxygen species (ROS) production, leading to non-tumor lymphoid cell death while enabling the survival and proliferation of a subset of lymphoma/leukemia cells, TICs or TIC-like cells. Treatment with the antioxidant N-acetylcysteine inhibits this lethality and promotes the growth of primary non-tumor lymphoid cells in 3D gels. A subset of lymphoma cells, characterized by an increased abundance of the antioxidant glutathione, escape ROS-induced lethality, a response not seen in non-tumor cells. Reducing glutathione production in lymphoma cells, either through pharmacological inhibition of glutamate cysteine ligase (GCL), the enzyme catalyzing the rate-limiting step in glutathione biosynthesis, or via knockdown of GCLC, the GCL catalytic subunit, sharply decreased cell growth in 3D gels and xenografts. Tumor cells from B-cell lymphoma/leukemia patients and λ-MYC mice, a B-cell lymphoma mouse model, overproduce glutathione. Importantly, pharmacological GCL inhibition hindered lymphoma growth in female λ-MYC mice, suggesting that this treatment holds promise as a therapeutic strategy for female lymphoma/leukemia patients.

DOI: https://doi.org/10.1038/s41419-024-06923-z
Apoptosis. 2024 Jul 28.

Glutamine deprivation in glioblastoma stem cells triggers autophagic SIRT3 degradation to epigenetically restrict CD133 expression and stemness.

Zhengcao Xing, Xianguo Jiang, Yalan Chen, Tiange Wang, Xiaohe Li, Xiangyun Wei, Qiuju Fan, Jie Yang, Hongmei Wu, Jinke Cheng, Rong Cai.

  Glioblastoma multiforme (GBM) is a highly malignant brain tumor, and glioblastoma stem cells (GSCs) are the primary cause of GBM heterogeneity, invasiveness, and resistance to therapy. Sirtuin 3 (SIRT3) is mainly localized in the mitochondrial matrix and plays an important role in maintaining GSC stemness through cooperative interaction with the chaperone protein tumor necrosis factor receptor-associated protein 1 (TRAP1) to modulate mitochondrial respiration and oxidative stress. The present study aimed to further elucidate the specific mechanisms by which SIRT3 influences GSC stemness, including whether SIRT3 serves as an autophagy substrate and the mechanism of SIRT3 degradation. We first found that SIRT3 is enriched in CD133+ GSCs. Further experiments revealed that in addition to promoting mitochondrial respiration and reducing oxidative stress, SIRT3 maintains GSC stemness by epigenetically regulating CD133 expression via succinate. More importantly, we found that SIRT3 is degraded through the autophagy-lysosome pathway during GSC differentiation into GBM bulk tumor cells. GSCs are highly dependent on glutamine for survival, and in these cells, we found that glutamine deprivation triggers autophagic SIRT3 degradation to restrict CD133 expression, thereby disrupting the stemness of GSCs. Together our results reveal a novel mechanism by which SIRT3 regulates GSC stemness. We propose that glutamine restriction to trigger autophagic SIRT3 degradation offers a strategy to eliminate GSCs, which combined with other treatment methods may overcome GBM resistance to therapy as well as relapse.

Keywords:  Autophagic degradation; GBM; Glioblastoma stem cell; Glutamine deprivation; SIRT3

DOI:  https://doi.org/10.1007/s10495-024-02003-x
Nat Commun. 2024 Aug 03. 15(1): 6570

Structural basis of the obligatory exchange mode of human neutral amino acid transporter ASCT2.

Anna M Borowska, Maria Gabriella Chiariello, Alisa A Garaeva, Jan Rheinberger, Siewert J Marrink, Cristina Paulino, Dirk J Slotboom.

ASCT2 is an obligate exchanger of neutral amino acids, contributing to cellular amino acid homeostasis. ASCT2 belongs to the same family (SLC1) as Excitatory Amino Acid Transporters (EAATs) that concentrate glutamate in the cytosol. The mechanism that makes ASCT2 an exchanger rather than a concentrator remains enigmatic. Here, we employ cryo-electron microscopy and molecular dynamics simulations to elucidate the structural basis of the exchange mechanism of ASCT2. We establish that ASCT2 binds three Na+ ions per transported substrate and visits a state that likely acts as checkpoint in preventing Na+ ion leakage, both features shared with EAATs. However, in contrast to EAATs, ASCT2 retains one Na+ ion even under Na+-depleted conditions. We demonstrate that ASCT2 cannot undergo the structural transition in TM7 that is essential for the concentrative transport cycle of EAATs. This structural rigidity and the high-affinity Na+ binding site effectively confine ASCT2 to an exchange mode.

DOI: https://doi.org/10.1038/s41467-024-50888-8
Nat Cell Biol. 2024 Jul 30.

mTORC2-driven chromatin cGAS mediates chemoresistance through epigenetic reprogramming in colorectal cancer.

Guoqing Lv, Qian Wang, Lin Lin, Qiao Ye, Xi Li, Qian Zhou, Xiangzhen Kong, Hongxia Deng, Fuping You, Hebing Chen, Song Wu, Lin Yuan.

Cyclic GMP-AMP synthase (cGAS), a cytosolic DNA sensor that initiates a STING-dependent innate immune response, binds tightly to chromatin, where its catalytic activity is inhibited; however, mechanisms underlying cGAS recruitment to chromatin and functions of chromatin-bound cGAS (ccGAS) remain unclear. Here we show that mTORC2-mediated phosphorylation of human cGAS serine 37 promotes its chromatin localization in colorectal cancer cells, regulating cell growth and drug resistance independently of STING. We discovered that ccGAS recruits the SWI/SNF complex at specific chromatin regions, modifying expression of genes linked to glutaminolysis and DNA replication. Although ccGAS depletion inhibited cell growth, it induced chemoresistance to fluorouracil treatment in vitro and in vivo. Moreover, blocking kidney-type glutaminase, a downstream ccGAS target, overcame chemoresistance caused by ccGAS loss. Thus, ccGAS coordinates colorectal cancer plasticity and acquired chemoresistance through epigenetic patterning. Targeting both mTORC2-ccGAS and glutaminase provides a promising strategy to eliminate quiescent resistant cancer cells.

DOI: https://doi.org/10.1038/s41556-024-01473-0
Clin Transl Med. 2024 Aug;14(8): e1754

ABCC2 induces metabolic vulnerability and cellular ferroptosis via enhanced glutathione efflux in gastric cancer.

Yiding Wang, Xuejun Gan, Xiaojing Cheng, Yongning Jia, Gangjian Wang, Xiaohuan Tang, Hong Du, Xiaomei Li, Xijuan Liu, Xiaofang Xing, Jiafu Ji, Ziyu Li.

   BACKGROUND: Although it is traditionally believed that ATP binding cassette subfamily C member 2 (ABCC2) is a multidrug resistance-associated protein correlated with a worse prognosis, our previous and several other studies demonstrated the contrary to be true in gastric cancer (GC). We aim to explore the underlying mechanism of this discovery.
METHODS: Our study utilized whole-exome sequencing (WES), RNA sequencing, and droplet digital PCR (ddPCR) analysis of 80 gastric cancer samples, along with comprehensive immunohistochemical (IHC) analysis of 1044 human GC tissue samples.By utilizing CRISPRCas9 to genetically modify cell lines with the ABCC2-24C > T (rs717620) point mutation and conducting dual-luciferase reporter assays, we identified that transcription factors SOX9 and ETS1 serve as negative regulators of ABCC2 expression. Seahorse assay and mass spectrometry were used to discover altered metabolic patterns. Gain and loss-of-function experiments in GC cell lines and preclinical models were carried out to validate ABCC2 biological function.
RESULTS: ABCC2 high expression correlated with better prognosis, and rs717620 can influence ABCC2 expression by disrupting the binding of ETS1 and SOX9. Gain and loss-of-function experiments in GC cell lines demonstrated amino acid deprivation reduces proliferation, migration, and drug resistance in ABCC2-high GC cells. ABCC2 leads to reduced intracellular amino acid pools and disruption of cellular energy metabolism. This phenomenon depended on ABCC2-mediated GSH extrusion, resulting in alterations in redox status, thereby increasing the cell's susceptibility to ferroptosis. Furthermore, patient-derived organoids and patient-derived tumor-like cell clusters were used to observe impact of ABCC2 on therapeutic effect. In the xenograft model with high ABCC2 expression, we observed that constricting amino acid intake in conjunction with GPX4 inactivation resulted in notable tumor regression.
CONCLUSIONS: Our findings demonstrate a significant role of ABCC2 in amino acid metabolism and ferroptosis by mediating GSH efflux in GC. This discovery underlines the potential of combining multiple ferroptosis targets as a promising therapeutic strategy for GC with high ABCC2 expression.
HIGHLIGHTS: ABCC2 plays a crucial role in inducing metabolic vulnerability and ferroptosis in gastric cancer through enhanced glutathione efflux. The ABCC2 24C > T polymorphism is a key factor influencing its expression. These results highlight the potential of ABCC2 as a predictive biomarker and therapeutic target in gastric cancer.

Keywords:  ABCC2; amino acid metabolism; ferroptosis; gastric cancer; glutathione

DOI:  https://doi.org/10.1002/ctm2.1754