Oral streptococci S. anginosus and S. mitis induce distinct morphological, inflammatory, and metabolic signatures in macrophages.

Oral streptococci, key players in oral biofilm formation, are implicated in oral dysbiosis and various clinical conditions, including dental caries, gingivitis, periodontal disease, and oral cancer. Specifically, Streptococcus anginosus is associated with esophageal, gastric, and pharyngeal cancers, while Streptococcus mitis is linked to oral cancer. However, no study has investigated the mechanistic links between these Streptococcus species and cancer-related inflammatory responses. As an initial step, we probed the innate immune response triggered by S. anginosus and S. mitis in RAW264.7 macrophages. These bacteria exerted time- and dose-dependent effects on macrophage morphology without affecting cell viability. Compared with untreated macrophages, macrophages infected with S. anginosus exhibited a robust proinflammatory response characterized by significantly increased levels of inflammatory cytokines and mediators, including TNF, IL-6, IL-1ß, NOS2, and COX2, accompanied by enhanced NF-κB activation. In contrast, S. mitis-infected macrophages failed to elicit a robust inflammatory response. Seahorse Xfe96 analysis revealed an increased extracellular acidification rate in macrophages infected with S. anginosus compared with S. mitis. At the 24-h time point, the presence of S. anginosus led to reduced extracellular itaconate, while S. mitis triggered increased itaconate levels, highlighting distinct metabolic profiles in macrophages during infection in contrast to aconitate decarboxylase expression observed at the 6-h time point. This initial investigation highlights how S. anginosus and S. mitis, two Gram-positive bacteria from the same genus, can prompt distinct immune responses and metabolic shifts in macrophages during infection.IMPORTANCEThe surge in head and neck cancer cases among individuals devoid of typical risk factors such as Human Papilloma Virus (HPV) infection and tobacco and alcohol use sparks an argumentative discussion around the emerging role of oral microbiota as a novel risk factor in oral squamous cell carcinoma (OSCC). While substantial research has dissected the gut microbiome's influence on physiology, the oral microbiome, notably oral streptococci, has been underappreciated during mucosal immunopathogenesis. Streptococcus anginosus, a viridans streptococci group, has been linked to abscess formation and an elevated presence in esophageal cancer and OSCC. The current study aims to probe the innate immune response to S. anginosus compared with the early colonizer Streptococcus mitis as an important first step toward understanding the impact of distinct oral Streptococcus species on the host immune response, which is an understudied determinant of OSCC development and progression.

Glucose Limitation Alters Glutamine Metabolism in MUC1-Overexpressing Pancreatic Cancer Cells.

Pancreatic cancer cells overexpressing Mucin 1 (MUC1) rely on aerobic glycolysis and, correspondingly, are dependent on glucose for survival. Our NMR metabolomics comparative analysis of control (S2-013.Neo) and MUC1-overexpressing (S2-013.MUC1) cells demonstrates that MUC1 reprograms glutamine metabolism upon glucose limitation. The observed alteration in glutamine metabolism under glucose limitation was accompanied by a relative decrease in the proliferation of MUC1-overexpressing cells compared with steady-state conditions. Moreover, glucose limitation induces G1 phase arrest where S2-013.MUC1 cells fail to enter S phase and synthesize DNA because of a significant disruption in pyrimidine nucleotide biosynthesis. Our metabolomics analysis indicates that glutamine is the major source of oxaloacetate in S2-013.Neo and S2-013.MUC1 cells, where oxaloacetate is converted to aspartate, an important metabolite for pyrimidine nucleotide biosynthesis. However, glucose limitation impedes the flow of glutamine carbons into the pyrimidine nucleotide rings and instead leads to a significant accumulation of glutamine-derived aspartate in S2-013.MUC1 cells.

Developments in purification methods for obtaining and evaluation of collagen derived endogenous angioinhibitors.

Collagen constitutes one of the vital components of the basement membrane scaffolds. Non-collagenous domains (NC1) derived from collagens exhibit potent anti-angiogenic properties, thus attaining significance in regulation of angiogenesis promoted diseases. Individual NC1 domains essential for anti-angiogenic evaluations are generally obtained through purification of individual non-collagenous domains, which have undergone steady developments for enhancing the yields, purpose of biological evaluations and solubility based on the nature of different NC1 domains. This review focuses on the method developments in obtaining biologically active NC1 domains and for specific evaluations in different scenarios.

Ubiquitous Aberration in Cholesterol Metabolism across Pancreatic Ductal Adenocarcinoma.

Pancreatic cancer (PC) is characterized by metabolic deregulations that often manifest as deviations in metabolite levels and aberrations in their corresponding metabolic genes across the clinical specimens and preclinical PC models. Cholesterol is one of the critical metabolites supporting PC, synthesized or acquired by PC cells. Nevertheless, the significance of the de novo cholesterol synthesis pathway has been controversial in PC, indicating the need to reassess this pathway in PC. We utilized preclinical models and clinical specimens of PC patients and cell lines and utilized mass spectrometry-based sterol analysis. Further, we also performed in silico analysis to corroborate the significance of de novo cholesterol synthesis pathway in PC. Our results demonstrated alteration in free sterol levels, including free cholesterol, across in vitro, in vivo, and clinical specimens of PC. Especially, our sterol analyses established consistent alterations in free cholesterol across the different PC models. Overall, this study demonstrates the significance and consistency in deviation of cholesterol synthesis pathway in PC while showing the aberrations in sterol metabolite intermediates and the related genes using preclinical models, in silico platforms, and the clinical specimens.

CD73 induces GM-CSF/MDSC-mediated suppression of T cells to accelerate pancreatic cancer pathogenesis.

Metabolic alterations regulate cancer aggressiveness and immune responses. Given the poor response of pancreatic ductal adenocarcinoma (PDAC) to conventional immunotherapies, we investigated the link between metabolic alterations and immunosuppression. Our metabolic enzyme screen indicated that elevated expression of CD73, an ecto-5'-nucleotidase that generates adenosine, correlates with increased aggressiveness. Correspondingly, we observed increased interstitial adenosine levels in tumors from spontaneous PDAC mouse models. Diminishing CD73 by genetic manipulations ablated in vivo tumor growth, and decreased myeloid-derived suppressor cells (MDSC) in orthotopic mouse models of PDAC. A high-throughput cytokine profiling demonstrated decreased GM-CSF in mice implanted with CD73 knockdowns. Furthermore, we noted increased IFN-γ expression by intratumoral CD4+ and CD8+ T cells in pancreatic tumors with CD73 knockdowns. Depletion of CD4+ T cells, but not CD8+ T cells abrogated the beneficial effects of decreased CD73. We also observed that splenic MDSCs from Nt5e knockdown tumor-bearing mice were incompetent in suppressing T cell activation in the ex vivo assays. Replenishing GM-CSF restored tumor growth in Nt5e knockout tumors, which was reverted by MDSC depletion. Finally, anti-CD73 antibody treatment significantly improved gemcitabine efficacy in orthotopic models. Thus, targeting the adenosine axis presents a novel therapeutic opportunity for improving the anti-tumoral immune response against PDAC.

Nuclear factor kappa-B contributes to cigarette smoke tolerance in pancreatic ductal adenocarcinoma through cysteine metabolism.

BACKGROUND: Retrospective studies revealed that cigarette smoking enhances risk of incidence and worsens prognosis in pancreatic cancer (PC) patients. Poor prognosis in smoker cohort of PC patients indicates prevalence of cigarette smoke stimulated survival mechanisms yet to be explored in PC. In this study, cigarette smoke induced metabolic pathways were explored and targeted in PC. METHODS: Human pancreatic ductal adenocarcinoma cell (PDAC) lines, genetically engineered mice models (GEMMs), mass spectrometry based heavy isotope-based metabolite analysis, cytotoxicity assays and Nuclear factor kappa-B (NF-kB) targeting were utilized in this study. Cigarette smoke extract (CSE) was prepared fresh each day by bubbling cell culture media with the smoke emitted from 85 mm, filtered, Code 1R6F reference cigarettes and used for in vitro procedures. High dose cigarette smoke exposure of GEMMs was achieved by daily exposure of animals to similar cigarettes, 6 h/day for a total period of 180 days. FINDINGS: We observed that PDAC cells upregulate glutathione anabolism through cysteine uptake and glutamate cysteine ligase (GCLM), supporting survival, upon CSE exposure. In vivo, cigarette smoke exposure leads to concomitant upregulation of GCLM and activated NF-kB in the PDAC consistent with in vitro, in CSE-exposed PDAC. Finally, either inhibition of NF-kB or depletion of cysteine impaired PDAC cell survival in cigarette smoke exposed conditions through suppression of glutathione and ROS enhancement, reverted by glutathione supplementation. INTERPRETATION: Our findings demonstrate scope for targeting smoke induced, NF-kB mediated, cysteine and glutathione metabolism for improving the survival of smoke addicted PDAC.

Long non-coding RNAs and nuclear factor-κB crosstalk in cancer and other human diseases.

The regulation of the pleiotropic transcription factor, nuclear factor-κB (NF-κB) by miRNAs and proteins is extensively studied. More recently, the NF-κB signaling was also reported to be regulated by several long non-coding RNAs (lncRNAs) that constitute the major portion of the noncoding component of the human genome. The common NF-κB associated lncRNAs include NKILA, HOTAIR, MALAT1, ANRIL, Lethe, MIR31HG, and PACER. The lncRNA and NF-κB signaling crosstalk during cancer and other diseases such as cardiomyopathy, celiac disease, cerebral infarction, chronic kidney disease, diabetes mellitus, Kawasaki disease, pregnancy loss, and rheumatoid arthritis. Some NF-κB related lncRNAs can affect gene expression without modulating NF-κB signaling. Most of the lncRNAs with a potential to modulate NF-κB signaling are regulated by NF-κB itself suggesting a feedback regulation. The discovery of lncRNAs have provided a new type of regulation for the NF-κB signaling and thus could be explored for therapeutic interventions. The manner in which lncRNA and NF-κB crosstalk affects human pathophysiology is discussed in this review. The challenges associated with the therapeutic interventions of this crosstalk are also discussed.

The Synergistic Effect of an ATP-Competitive Inhibitor of mTOR and Metformin on Pancreatic Tumor Growth.

BACKGROUND: The mechanistic target of rapamycin complex 1 (mTORC1) is a nutrient-sensing pathway and a key regulator of amino acid and glucose metabolism. Dysregulation of the mTOR pathways is implicated in the pathogenesis of metabolic syndrome, obesity, type 2 diabetes, and pancreatic cancer. OBJECTIVES: We investigated the impact of inhibition of mTORC1/mTORC2 and synergism with metformin on pancreatic tumor growth and metabolomics. METHODS: Cell lines derived from pancreatic tumors of the KPC (KrasG12D/+; p53R172H/+; Pdx1-Cre) transgenic mice model were implanted into the pancreas of C57BL/6 albino mice (n = 10/group). Two weeks later, the mice were injected intraperitoneally with daily doses of 1) Torin 2 (mTORC1/mTORC2 inhibitor) at a high concentration (TH), 2) Torin 2 at a low concentration (TL), 3) metformin at a low concentration (ML), 4) a combination of Torin 2 and metformin at low concentrations (TLML), or 5) DMSO vehicle (control) for 12 d. Tissues and blood samples were collected for targeted xenometabolomics analysis, drug concentration, and cell signaling. RESULTS: Metabolomic analysis of the control and treated plasma samples showed differential metabolite profiles. Phenylalanine was significantly elevated in the TLML group compared with the control (+426%, P = 0.0004), whereas uracil was significantly lower (-38%, P = 0.009). The combination treatment reduced tumor growth in the orthotopic mouse model. TLML significantly decreased pancreatic tumor volume (498 ± 104 mm3; 37%; P < 0.0004) compared with control (1326 ± 134 mm3; 100%), ML (853 ± 67 mm3; 64%), TL (745 ± 167 mm3; 54%), and TH (665 ± 182 mm3; 50%) (ANOVA and post hoc tests). TLML significantly decreased tumor weights (0.66 ± 0.08 g; 52%) compared with the control (1.28 ± 0.19 g; 100%) (P < 0.002). CONCLUSIONS: The combination of mTOR dual inhibition by Torin 2 and metformin is associated with an altered metabolomic profile and a significant reduction in pancreatic tumor burden compared with single-agent therapy, and it is better tolerated.

Amino Acids Regulate Cisplatin Insensitivity in Neuroblastoma.

Neuroblastoma are pediatric, extracranial malignancies showing alarming survival prognosis outcomes due to their resilience to current aggressive treatment regimens, including chemotherapies with cisplatin (CDDP) provided in the first line of therapy regimens. Metabolic deregulation supports tumor cell survival in drug-treated conditions. However, metabolic pathways underlying cisplatin-resistance are least studied in neuroblastoma. Our metabolomics analysis revealed that cisplatin-insensitive cells alter their metabolism; especially, the metabolism of amino acids was upregulated in cisplatin-insensitive cells compared to the cisplatin-sensitive neuroblastoma cell line. A significant increase in amino acid levels in cisplatin-insensitive cells led us to hypothesize that the mechanisms upregulating intracellular amino acid pools facilitate insensitivity in neuroblastoma. We hereby report that amino acid depletion reduces cell survival and cisplatin-insensitivity in neuroblastoma cells. Since cells regulate their amino acids levels through processes, such as autophagy, we evaluated the effects of hydroxychloroquine (HCQ), a terminal autophagy inhibitor, on the survival and amino acid metabolism of cisplatin-insensitive neuroblastoma cells. Our results demonstrate that combining HCQ with CDDP abrogated the amino acid metabolism in cisplatin-insensitive cells and sensitized neuroblastoma cells to sub-lethal doses of cisplatin. Our results suggest that targeting of amino acid replenishing mechanisms could be considered as a potential approach in developing combination therapies for treating neuroblastomas.

Author Correction: Combination of ERK and autophagy inhibition as a treatment approach for pancreatic cancer.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Evaluating the Metabolic Alterations in Pancreatic Cancer.

Metabolic reprograming is an established hallmark of cancer cells. Pancreatic cancer cells, by virtue of the underlying oncogenic drivers, demonstrate metabolic reprograming to sustain growth, invasiveness, and therapy resistance. The increased demands of the growing tumor cells alter the metabolic and signaling pathways to meet the growing nutrient requirements. Investigating the metabolic vulnerabilities of tumor cells can help in developing effective therapeutics to target pancreatic cancer. In this chapter, we explain in detail the methods to evaluate the metabolic changes occurring in the tumor. This includes the glucose/glutamine uptake assays and the measurement of reactive oxygen species, extracellular acidification rate, and oxygen consumption rate in the tumor cells. All these physiological assays help in understanding the metabolic nature of the tumor.

Metabolic Alterations in Pancreatic Cancer Progression.

Pancreatic cancer is the third leading cause of cancer-related deaths in the USA. Pancreatic tumors are characterized by enhanced glycolytic metabolism promoted by a hypoxic tumor microenvironment and a resultant acidic milieu. The metabolic reprogramming allows cancer cells to survive hostile microenvironments. Through the analysis of the principal metabolic pathways, we identified the specific metabolites that are altered during pancreatic cancer progression in the spontaneous progression (KPC) mouse model. Genetically engineered mice exhibited metabolic alterations during PanINs formation, even before the tumor development. To account for other cells in the tumor microenvironment and to focus on metabolic adaptations concerning tumorigenic cells only, we compared the metabolic profile of KPC and orthotopic tumors with those obtained from KPC-tumor derived cell lines. We observed significant upregulation of glycolysis and the pentose phosphate pathway metabolites even at the early stages of pathogenesis. Other biosynthetic pathways also demonstrated a few common perturbations. While some of the metabolic changes in tumor cells are not detectable in orthotopic and spontaneous tumors, a significant number of tumor cell-intrinsic metabolic alterations are readily detectable in the animal models. Overall, we identified that metabolic alterations in precancerous lesions are maintained during cancer development and are largely mirrored by cancer cells in culture conditions.

Fascin Controls Metastatic Colonization and Mitochondrial Oxidative Phosphorylation by Remodeling Mitochondrial Actin Filaments.

The deregulation of the actin cytoskeleton has been extensively studied in metastatic dissemination. However, the post-dissemination role of the actin cytoskeleton dysregulation is poorly understood. Here, we report that fascin, an actin-bundling protein, promotes lung cancer metastatic colonization by augmenting metabolic stress resistance and mitochondrial oxidative phosphorylation (OXPHOS). Fascin is directly recruited to mitochondria under metabolic stress to stabilize mitochondrial actin filaments (mtF-actin). Using unbiased metabolomics and proteomics approaches, we discovered that fascin-mediated mtF-actin remodeling promotes mitochondrial OXPHOS by increasing the biogenesis of respiratory Complex I. Mechanistically, fascin and mtF-actin control the homeostasis of mtDNA to promote mitochondrial OXPHOS. The disruption of mtF-actin abrogates fascin-mediated lung cancer metastasis. Conversely, restoration of mitochondrial respiration by using yeast NDI1 in fascin-depleted cancer cells is able to rescue lung metastasis. Our findings indicate that the dysregulated actin cytoskeleton in metastatic lung cancer could be targeted to rewire mitochondrial metabolism and to prevent metastatic recurrence.

The role of exosomes and MYC in therapy resistance of acute myeloid leukemia: Challenges and opportunities.

Acute myeloid leukemia (AML) is caused by abnormal production of white blood cells, red blood cells or platelets. The leukemia cells communicate with their microenvironment through nano-vesicle exosomes that are 30-100 nm in diameter. These nano-vesicles are released from body fluids upon fusion of an endocytic compartment with the cell membrane. Exosomes function as cargo to deliver signaling molecules to distant cells. This allows cross-talk between hematopoietic cells and other distant target cell environments. Exosomes support leukemia growth by acting as messengers between tumor cells and the microenvironment as well as inducing oncogenic factors such as c-Myc. Exosomes have also been used as biomarkers in the clinical diagnosis of leukemia. Glycogen synthase kinase-3 (GSK-3) and protein phosphatase 2A (PP2A) are two crucial signaling molecules involved in the AML pathogenesis and MYC stability. GSK-3 is a serine/threonine protein kinase that coordinates with over 40 different proteins during physiological/pathological conditions in blood cells. The dysregulation in GSK-3 has been reported during hematological malignancies. GSK-3 acts as a tumor suppressor by targeting c-MYC, MCL-1 and ß-catenin. Conversely, GSK-3 can also act as tumor promoter in some instances. The pharmacological modulators of GSK-3 such as ABT-869, 6-Bromoindirubin-3'-oxime (BIO), GS-87 and LY2090314 have shown promise in the treatment of hematological malignancy. PP2A is a heterotrimeric serine/threonine phosphatase involved in the regulation of hematological malignancy. PP2A-activating drugs (PADs) can effectively antagonize leukemogenesis. The discovery of exosomes, kinase inhibitors and phosphatase activators have provided new hope to the leukemia patients. This review discusses the role of exosomes, GSK-3 and PP2A in the pathogenesis of leukemia. We provide evidence from both preclinical and clinical studies.

RNA-Binding Protein HuR Regulates Both Mutant and Wild-Type IDH1 in IDH1-Mutated Cancer.

Isocitrate dehydrogenase 1 (IDH1) is the most commonly mutated metabolic enzyme in human malignancy. A heterozygous genetic alteration, arginine 132, promotes the conversion of α-ketoglutarate to D-2-hydroxyglutarate (2-HG). Although pharmacologic inhibitors of mutant IDH1 are promising, resistance mechanisms to targeted therapy are not understood. Additionally, the role of wild-type IDH1 (WT.IDH1) in cancer requires further study. Recently, it was observed that the regulatory RNA-binding protein, HuR (ELAVL1), protects nutrient-deprived cancer cells without IDH1 mutations, by stabilizing WT.IDH1 transcripts. In the present study, a similar regulatory effect on both mutant (Mut.IDH1) and WT.IDH1 transcripts in heterozygous IDH1-mutant tumors is observed. In ribonucleoprotein immunoprecipitation assays of IDH1-mutant cell lines, wild-type and mutant IDH1 mRNAs each bound to HuR. Both isoforms were profoundly downregulated at the mRNA and protein levels after genetic suppression of HuR (siRNAs or CRISPR deletion) in HT1080 (R132C IDH1 mutation) and BT054 cells (R132H). Proliferation and invasion were adversely affected after HuR suppression and metabolomic studies revealed a reduction in Pentose Phosphate Pathway metabolites, nucleotide precursors, and 2-HG levels. HuR-deficient cells were especially sensitive to stress, including low glucose conditions or a mutant IDH1 inhibitor (AGI-5198). IDH1-mutant cancer cells were rescued by WT.IDH1 overexpression to a greater extent than Mut.IDH1 overexpression under these conditions. This study reveals the importance of HuR's regulation of both mutant and wild-type IDH1 in tumors harboring a heterozygous IDH1 mutation with implications for therapy. IMPLICATIONS: This study highlights the HuR-IDH1 (mutant and wild-type IDH1) regulatory axis as a critical, actionable therapeutic target in IDH1-mutated cancer, and incomplete blockade of the entire HuR-IDH1 survival axis would likely diminish the efficacy of drugs that selectively target only the mutant isoenzyme.

Combination of ERK and autophagy inhibition as a treatment approach for pancreatic cancer.

Pancreatic ductal adenocarcinoma (PDAC) is characterized by KRAS- and autophagy-dependent tumorigenic growth, but the role of KRAS in supporting autophagy has not been established. We show that, to our surprise, suppression of KRAS increased autophagic flux, as did pharmacological inhibition of its effector ERK MAPK. Furthermore, we demonstrate that either KRAS suppression or ERK inhibition decreased both glycolytic and mitochondrial functions. We speculated that ERK inhibition might thus enhance PDAC dependence on autophagy, in part by impairing other KRAS- or ERK-driven metabolic processes. Accordingly, we found that the autophagy inhibitor chloroquine and genetic or pharmacologic inhibition of specific autophagy regulators synergistically enhanced the ability of ERK inhibitors to mediate antitumor activity in KRAS-driven PDAC. We conclude that combinations of pharmacologic inhibitors that concurrently block both ERK MAPK and autophagic processes that are upregulated in response to ERK inhibition may be effective treatments for PDAC.

Hypoxia-Induced Metabolomic Alterations in Pancreatic Cancer Cells.

Hypoxic conditions in the pancreatic tumor microenvironment lead to the stabilization of hypoxia-inducible factor-1 alpha (HIF-1α), which acts as the master regulator of cancer cell metabolism. HIF-1α-mediated metabolic reprogramming results in large-scale metabolite perturbations. Characterization of the metabolic intermediates and the corresponding metabolic pathways altered by HIF-1α would facilitate the identification of therapeutic targets for hypoxic microenvironments prevalent in pancreatic ductal adenocarcinoma and other solid tumors. Targeted metabolomic approaches are versatile in quantifying multiple metabolite levels in a single platform and, thus, enable the characterization of multiple metabolite alterations regulated by HIF-1α. In this chapter, we describe a detailed metabolomic approach for characterizing the hypoxia-induced metabolomic alterations using pancreatic cancer cell lines cultured in normoxic and hypoxic conditions. We elaborate the methodology of cell culture, hypoxic exposure, metabolite extraction, and relative quantification of polar metabolites from normoxia- and hypoxia-exposed cell extracts, using a liquid chromatography-coupled tandem mass spectrometry approach. Herein, using our metabolomic data, we also present the methods for metabolomic data representation.

MUC1 facilitates metabolomic reprogramming in triple-negative breast cancer.

BACKGROUND: Mucin1 (MUC1), a glycoprotein associated with chemoresistance and an aggressive cancer phenotype, is aberrantly overexpressed in triple-negative breast cancer (TNBC). Recent studies suggest that MUC1 plays a role in modulating cancer cell metabolism and thereby supports tumor growth. Herein, we examined the role of MUC1 in metabolic reprogramming in TNBC. METHODS: MUC1 was stably overexpressed in MDA-MB-231 TNBC cells and stably knocked down in MDA-MB-468 cells. We performed liquid chromatography-coupled tandem mass spectrometry-assisted metabolomic analyses and physiological assays, which indicated significant alterations in the metabolism of TNBC cells due to MUC1 expression. RESULTS: Differential analyses identified significant differences in metabolic pathways implicated in cancer cell growth. In particular, MUC1 expression altered glutamine dependency of the cells, which can be attributed in part to the changes in the expression of genes that regulate glutamine metabolism, as observed by real-time PCR analysis. Furthermore, MUC1 expression altered the sensitivity of cells to transaminase inhibitor aminooxyacetate (AOA), potentially by altering glutamine metabolism. CONCLUSIONS: Collectively, these results suggest that MUC1 serves as a metabolic regulator in TNBC, facilitating the metabolic reprogramming of glutamine utilization that influences TNBC tumor growth.

Correction: MUC1 facilitates metabolomic reprogramming in triple-negative breast cancer.

[This corrects the article DOI: 10.1371/journal.pone.0176820.].

GOT1-mediated anaplerotic glutamine metabolism regulates chronic acidosis stress in pancreatic cancer cells.

The increased rate of glycolysis and reduced oxidative metabolism are the principal biochemical phenotypes observed in pancreatic ductal adenocarcinoma (PDAC) that lead to the development of an acidic tumor microenvironment. The pH of most epithelial cell-derived tumors is reported to be lower than that of plasma. However, little is known regarding the physiology and metabolism of cancer cells enduring chronic acidosis. Here, we cultured PDAC cells in chronic acidosis (pH 6.9-7.0) and observed that cells cultured in low pH had reduced clonogenic capacity. However, our physiological and metabolomics analysis showed that cells in low pH deviate from glycolytic metabolism and rely more on oxidative metabolism. The increased expression of the transaminase enzyme GOT1 fuels oxidative metabolism of cells cultured in low pH by enhancing the non-canonical glutamine metabolic pathway. Survival in low pH is reduced upon depletion of GOT1 due to increased intracellular ROS levels. Thus, GOT1 plays an important role in energy metabolism and ROS balance in chronic acidosis stress. Our studies suggest that targeting anaplerotic glutamine metabolism may serve as an important therapeutic target in PDAC.