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

Integrated RNA and metabolite profiling of urine liquid biopsies for prostate cancer biomarker discovery

Sensitive and specific diagnostic and prognostic biomarkers for prostate cancer (PCa) are urgently needed. Urine samples are a non-invasive means to obtain abundant and readily accessible “liquid biopsies”. Herein we used urine liquid biopsies to identify and characterize a novel group of urine-enriched RNAs and metabolites in patients with PCa and normal individuals with or without benign prostatic disease. Differentially expressed RNAs were identified in urine samples by deep sequencing and metabolites in urine were measured by mass spectrometry. mRNA and metabolite profiles were distinct in patients with benign and malignant disease. Integrated analysis of urinary gene expression and metabolite signatures unveiled an aberrant glutamate metabolism and tricarboxylic acid (TCA) cycle node in prostate cancer-derived cells. Functional validation supported a role for glutamate metabolism and glutamate oxaloacetate transaminase 1 (GOT1)-dependent redox balance in PCa, which could be exploited for novel biomarkers and therapies. In this study, we discovered cancer-specific changes in urinary RNAs and metabolites, paving the way for the development of sensitive and specific urinary PCa diagnostic biomarkers either alone or in combination. Our methodology was based on single void urine samples (i.e., without prostatic massage). The integrated analysis of metabolomic and transcriptomic data from these liquid biopsies revealed a glutamate metabolism and tricarboxylic acid cycle node that was specific to prostate-derived cancer cells and cancer-specific metabolic changes in urine.

A covalent small molecule inhibitor of glutamate-oxaloacetate transaminase 1 impairs pancreatic cancer growth

Metabolic programs are rewired in cancer cells to support survival and tumor growth. Among these, recent studies have demonstrated that glutamate-oxaloacetate transaminase 1 (GOT1) plays key roles in maintaining redox homeostasis and proliferation of pancreatic ductal adenocarcinomas (PDA). This suggests that small molecule inhibitors of GOT1 could have utility for the treatment of PDA. However, the development of GOT1 inhibitors has been challenging, and no compound has yet demonstrated selectivity for GOT1-dependent cell metabolism or selective growth inhibition of PDA cell lines. In contrast, potent inhibitors that covalently bind to the transaminase cofactor pyridoxal-5'-phosphate (PLP), within the active site of the enzyme, have been reported for kynurenine aminotransferase (KAT) and gamma-aminobutyric acid aminotransferase (GABA-AT). Given the drug discovery successes with these transaminases, we aimed to identify PLP-dependent suicide substrate-type GOT1 inhibitors. Here, we demonstrate that PF-04859989, a known KAT2 inhibitor, has PLP-dependent inhibitory activity against GOT1 and shows selective growth inhibition of PDA cell lines.

Metastasis in Pancreatic Ductal Adenocarcinoma: Current Standing and Methodologies

Pancreatic ductal adenocarcinoma is an extremely aggressive disease with a high metastatic potential. Most patients are diagnosed with metastatic disease, at which the five-year survival rate is only 3%. A better understanding of the mechanisms that drive metastasis is imperative for the development of better therapeutic interventions. Here, we take the reader through our current knowledge of the parameters that support metastatic progression in pancreatic ductal adenocarcinoma, and the experimental models that are at our disposal to study this process. We also describe the advantages and limitations of these models to study the different aspects of metastatic dissemination.

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.

Transcriptomic profiling of gamma ray induced mutants from the CGL1 human hybrid cell system reveals novel insights into the mechanisms of radiation-induced carcinogenesis

BACKGROUND

Somatic cell hybrid systems generated by combining cancerous with non-cancerous cells provide useful model systems to study neoplastic transformation. Combined with recent advances in omics-based technologies, novel molecular signatures that drive radiation-induced carcinogenesis can be analyzed at an exceptional global level.

METHODS

Here, we present a complete whole-transcriptome analysis of gamma-induced mutants (GIM) and gamma irradiated control (CON) segregants isolated from the CGL1 (HeLa x normal fibroblast) human hybrid cell-system exposed to high doses of radiation. Using the Human Transcriptome Array 2.0 microarray technology and conservative discrimination parameters, we have elucidated 1067 differentially expressed genes (DEGs) between tumorigenic and non-tumorigenic cells.

RESULTS

Gene ontology enrichment analysis revealed that tumorigenic cells demonstrated shifts in extracellular matrix (ECM) and cellular adhesion profiles, dysregulation of cyclic AMP (cAMP) signaling, and alterations in nutrient transport and cellular energetics. Furthermore, putative upstream master regulator analysis demonstrated that loss of TGFβ1 signaling due to reduced SMAD3 expression is involved in radiation-induced carcinogenesis.

CONCLUSIONS

Taken together, this study presents novel insights into specific gene expression and pathway level differences that contribute to radiation-induced carcinogenesis in a human cell-based model. This global transcriptomic analysis and our published tumor suppressor gene deletion loci analyses will allow us to identify and functionally test candidate nexus upstream tumor suppressor genes that are deleted or silenced after exposure to radiation.

Aspulvinone O, a natural inhibitor of GOT1 suppresses pancreatic ductal adenocarcinoma cells growth by interfering glutamine metabolism

BACKGROUND

Distinctive from their normal counterparts, cancer cells exhibit unique metabolic dependencies on glutamine to fuel anabolic processes. Specifically, pancreatic ductal adenocarcinoma (PDAC) cells rely on an unconventional metabolic pathway catalyzed by aspartate transaminase 1 (GOT1) to rewire glutamine metabolism and support nicotinamide adenine dinucleotide phosphate (NADPH) production. Thus, the important role of GOT1 in energy metabolism and Reactive Oxygen Species (ROS) balance demonstrates that targeting GOT1 may serve as an important therapeutic target in PDAC.

METHODS

To assay the binding affinity between Aspulvinone O (AO) and GOT1 proteins, the virtual docking, microscale thermophoresis (MST), cellular thermal shift assay (CETSA) and drug affinity responsive target stability (DARTS) methods were employed. GOT1 was silenced in several PDAC cell lines. The level of OCR and ECR were assayed by seahorse. To evaluate the in vivo anti-tumor efficacy of AO, the xenograft model was built in CB17/scid mouse.

RESULTS

Screening of an in-house natural compound library identified the AO as a novel inhibitor of GOT1 and repressed glutamine metabolism, which sensitizes PDAC cells to oxidative stress and suppresses cell proliferation. Virtual docking analysis suggested that AO could bind to the active site of GOT1 and form obvious hydrophobic interaction with Trp141 together with hydrogen bonds with Thr110 and Ser256. Further in vitro validation, including MST, CETSA and DARTS, further demonstrated the specific combining capacity of AO. We also show that the selective inhibition of GOT1 by AO significantly reduces proliferation of PDAC in vitro and in vivo.

CONCLUSIONS

Taken together, our findings identify AO as a potent bioactive inhibitor of GOT1 and a novel anti-tumour agent for PDAC therapy.

PFOA and PFOS promote diabetic renal injury in vitro by impairing the metabolisms of amino acids and purines

BACKGROUND

Environmental pollutants, perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS), are common surfactants in various consumer products. Epidemiological studies have demonstrated the association of diabetic kidney diseases with PFOA and PFOS. However, mechanisms of metabolic alterations involved are still unclear.

METHODS

Considering their involvement of glomerular hemodynamics, rat mesangial cells (MCs) are used as an in vitro model of diabetic kidney diseases for exposure to PFOS/PFOA under diabetic condition. Non-targeted metabolomics studies based on liquid chromatography-high resolution mass spectrometry were conducted to determine how PFOA/PFOS promoted fibrotic and proinflammatory responses in the MCs under diabetic condition.

RESULTS

Exposure of PFOA/PFOS (10 μM) increased oxidative stress and the levels of fibrotic and proinflammatory markers in MCs under diabetic condition. We demonstrated for the first time that PFOA and PFOS altered amino acid biosynthesis, citrate cycle, and purine metabolism in MCs under diabetic condition. Compared with diabetic condition, the exposure of PFOA and PFOS under diabetic condition more significantly altered the levels of 13 intracellular metabolites, including L-tyrosine, L-phenylalanine, L-arginine, L-tryptophan, AMP, ADP, UMP, inosine, and hypoxanthine, which have been reported to be related to kidney injury. In addition, PFOA/PFOS treatment significantly altered the expression levels of key enzymes involved in these metabolisms. Treatment with L-tyrosine, L-phenylalanine, L-arginine, and L-tryptophan reduced the levels of fibrotic and inflammatory markers induced by PFOA/PFOS.

CONCLUSION

Our results suggest that under diabetic condition, exposure of PFOA or PFOS aggravated diabetic kidney injury in vitro by impairing metabolisms of amino acids and purines to induce more fibrosis and inflammation in MCs.

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.

Chromatin accessibility changes are associated with enhanced growth and liver metastasis capacity of acid-adapted colorectal cancer cells

The acidic extracellular microenvironment, namely acidosis, is a biochemical hallmark of solid tumors. However, the tumorigenicity, metastatic potential, gene expression profile and chromatin accessibility of acidosis-adapted colorectal cancer cells remain unknown. The colorectal cancer cell SW620 was cultured in acidic medium (pH 6.5) for more than 3 months to be acidosis-adapted (SW620-AA). In comparison to parental cells, SW620-AA cells exhibit enhanced tumorigenicity and liver metastatic potential in vivo. Following mRNA and lncRNA expression profiling, we validated that OLMF1, NFIB, SMAD9, DGKB are upregulated, while SESN2, MAP1B, UTRN, PCDH19, IL18, LMO2, CNKSR3, GXYLT2 are downregulated in SW620-AA cells. The differentially expressed mRNAs were significantly enriched in DNA remodeling-associated pathways including HDACs deacetylate histones, SIRT1 pathway, DNA methylation, DNA bending complex, and RNA polymerase 1 chain elongation. Finally, chromatin accessibility evaluation by ATAC-sequencing revealed that the differentially opened peaks were enriched in pathways such as small cell lung cancer, pathways in cancer, ErbB signaling, endometrial cancer, and chronic myeloid leukemia, which were mainly distributed in intergenic regions and introns. These results suggest that the chromatin accessibility changes are correlated with enhanced growth and liver metastasis capacity of acid-adapted colorectal cancer cells.

Hypoxia-Mediated In Vivo Tumor Glucose Uptake Measurement and Analysis

Most solid tumors are hypoxic in nature due to the limited supply of oxygen to internal tissues. Hypoxia plays an important role in metabolic adaptations of tumors that contribute significantly to cancer pathogenesis. Among the several metabolic alterations induced by hypoxia, hypoxia-mediated increased glucose uptake serves as the hallmark of metabolic reprogramming. Hypoxia-mediated stabilization of hypoxia-inducible factor-1 alpha (HIF-1α) transcription factor leads to altered expression of several glycolytic genes and glucose transporters, which results in increased glucose uptake by tumor cells. Here we describe an easy and simple way of measuring the hypoxia-mediated tumor glucose uptake in vivo. The method is based on fluorescent imaging probe, RediJect 2-DG, which is a nonradioactive fluorescent-tagged glucose molecule. We have discussed orthotopic tumor implantation of HIF-1α knockdown and control pancreatic cancer cells and glucose uptake measurement in vivo by using IVIS imaging system along with reagent preparations.

Targeting SLC25A10 alleviates improved antioxidant capacity and associated radioresistance of cancer cells induced by chronic-cycling hypoxia

High tumor heterogeneity and increased therapy resistance acquired in a hypoxic tumor microenvironment remain major obstacles to successful radiotherapy. Others and we have shown that adaptation of cancer cells to cycling severe hypoxia and intermittent reoxygenation stress (chronic-cycling hypoxia) increases cellular antioxidant capacity thereby supporting resistance to chemotherapy and radiotherapy. Here we explored the involvement of antioxidant-associated mitochondrial transport-systems for maintenance of redox-homeostasis in adaptation to chronic-cycling hypoxia and associated radioresistance. Genetic or pharmacological inhibition of the mitochondrial dicarboxylate carrier (SLC25A10) or the oxoglutarate-carrier (SLC25A11) increased the cytotoxic effects of ionizing radiation (IR). But only targeting of SLC25A10 was effective in overcoming chronic-cycling hypoxia-induced enhanced death resistance in vitro and in vivo by disturbing increased antioxidant capacity. Furthermore, in silico analysis revealed that overexpression of SLC25A10 but not SLC25A11 is associated with reduced overall survival in lung- and breast-cancer patients. Our study reveals a role of SLC25A10 in supporting both, redox- and energy-homeostasis, ensuring radioresistance of cancer cells with tolerance to chronic-cycling hypoxia thereby proposing a novel strategy to overcome a mechanism of hypoxia-induced therapy resistance with potential clinical relevance regarding decreased patient survival.

Regulation of protein-coding gene and long noncoding RNA pairs in liver of conventional and germ-free mice following oral PBDE exposure

Gut microbiome communicates with the host liver to modify hepatic xenobiotic biotransformation and nutrient homeostasis. Polybrominated diphenyl ethers (PBDEs) are persistent environmental contaminants that are detected in fatty food, household dust, and human breast milk at worrisome levels. Recently, long noncoding RNAs (lncRNAs) have been recognized as novel biomarkers for toxicological responses and may regulate the transcriptional/translational output of protein-coding genes (PCGs). However, very little is known regarding to what extent the interactions between PBDEs and gut microbiome modulate hepatic lncRNAs and PCGs, and what critical signaling pathways are impacted at the transcriptomic scale. In this study, we performed RNA-Seq in livers of nine-week-old male conventional (CV) and germ-free (GF) mice orally exposed to the most prevalent PBDE congeners BDE-47 and BDE-99 (100 μmol/kg once daily for 4-days; vehicle: corn oil, 10 ml/kg), and unveiled key molecular pathways and PCG-lncRNA pairs targeted by PBDE-gut microbiome interactions. Lack of gut microbiome profoundly altered the PBDE-mediated transcriptomic response in liver, with the most prominent effect observed in BDE-99-exposed GF mice. The top pathways up-regulated by PBDEs were related to xenobiotic metabolism, whereas the top pathways down-regulated by PBDEs were in lipid metabolism and protein synthesis in both enterotypes. Genomic annotation of the differentially regulated lncRNAs revealed that majority of these lncRNAs overlapped with introns and 3'-UTRs of PCGs. Lack of gut microbiome profoundly increased the percentage of PBDE-regulated lncRNAs mapped to the 3'-UTRs of PCGs, suggesting the potential involvement of lncRNAs in increasing the translational efficiency of PCGs by preventing miRNA-3'-UTR binding, as a compensatory mechanism following toxic exposure to PBDEs. Pathway analysis of PCGs paired with lncRNAs revealed that in CV mice, BDE-47 regulated nucleic acid and retinol metabolism, as well as circadian rhythm; whereas BDE-99 regulated fatty acid metabolism. In GF mice, BDE-47 differentially regulated 19 lncRNA-PCG pairs that were associated with glutathione conjugation and transcriptional regulation. In contrast, BDE-99 up-regulated the xenobiotic-metabolizing Cyp3a genes, but down-regulated the fatty acid-metabolizing Cyp4 genes. Taken together, the present study reveals common and unique lncRNAs and PCG targets of PBDEs in mouse liver, and is among the first to show that lack of gut microbiome sensitizes the liver to toxic exposure of BDE-99 but not BDE-47. Therefore, lncRNAs may serve as specific biomarkers that differentiate various PBDE congeners as well as environmental chemical-mediated dysbiosis. Coordinate regulation of PCG-lncRNA pairs may serve as a more efficient molecular mechanism to combat against xenobiotic insult, and especially during dysbiosis-induced increase in the internal dose of toxicants.

Inhibition of glutamate oxaloacetate transaminase 1 in cancer cell lines results in altered metabolism with increased dependency of glucose

BACKGROUND

Glutamate oxaloacetate transaminase 1 (GOT1) regulates cellular metabolism through coordinating the utilization of carbohydrates and amino acids to meet nutrient requirements. KRAS mutated cancer cells were recently shown to rely on GOT1 to support long-term cell proliferation. The aim of the present study was to address the role of GOT1 in the metabolic adaption of cancer cells.

METHODS

GOT1-null and knockdown cell lines were established through CRISPR/Cas9 and shRNA techniques. The growth properties, colony formation ability, autophagy and selected gene expression profiles were analysed. Glucose deprivation decreased the viability of the GOT1-null cells and rescue experiments were conducted with selected intermediates. The redox NADH/NAD⁺ homeostasis as well as lactate secretion were determined. GOT1 expression levels and correlation with survival rates were analysed in selected tumor databases.

RESULTS

Inhibition of GOT1 sensitized the cancer cells to glucose deprivation, which was partially counteracted by oxaloacetate and phosphoenol pyruvate, metabolic intermediates downstream of GOT1. Moreover, GOT1-null cells accumulated NADH and displayed a decreased ratio of NADH/NAD⁺ with nutrient depletion. The relevance of GOT1 as a potential target in cancer therapy was supported by a lung adenocarcinoma RNA-seq data set as well as the GEO:GSE database of metastatic melanoma where GOT1 expression was increased. High levels of GOT1 were further linked to poor survival as analysed by the GEPIA web tool, in thyroid and breast carcinoma and in lung adenocarcinoma.

CONCLUSIONS

Our study suggests an important role of GOT1 to coordinate the glycolytic and the oxidative phosphorylation pathways in KRAS mutated cancer cells. GOT1 is crucial to provide oxaloacetate at low glucose levels, likely to maintain the redox homeostasis. Our data suggest GOT1 as a possible target in cancer therapy.

The plasticity of pancreatic cancer metabolism in tumor progression and therapeutic resistance

Pancreatic ductal adenocarcinoma (PDA) is an aggressive cancer that is highly refractory to the current standards of care. The difficulty in treating this disease is due to a number of different factors, including altered metabolism. In PDA, the metabolic rewiring favors anabolic reactions which supply the cancer cell with necessary cellular building blocks for unconstrained growth. Furthermore, PDA cells display high levels of basal autophagy and macropinocytosis. KRAS is the driving oncogene in PDA and many of the metabolic changes are downstream of its activation. Together, these unique pathways for nutrient utilization and acquisition result in metabolic plasticity enabling cells to rapidly adapt to nutrient and oxygen fluctuations. This remarkable adaptability has been implicated as a cause of the intense therapeutic resistance. In this review, we discuss metabolic pathways in PDA tumors and highlight how they contribute to the pathogenesis and treatment of the disease.

Phosphoinositide 3-Kinase Signaling Pathway in Pancreatic Ductal Adenocarcinoma Progression, Pathogenesis, and Therapeutics

Pancreatic ductal adenocarcinoma (PDAC) is a highly aggressive malignancy characterized by its sudden manifestation, rapid progression, poor prognosis, and limited therapeutic options. Genetic alterations in key signaling pathways found in early pancreatic lesions are pivotal for the development and progression of pancreatic intraepithelial neoplastic lesions into invasive carcinomas. More than 90% of PDAC tumors harbor driver mutations in K-Ras that activate various downstream effector-signaling pathways, including the phosphoinositide-3-kinase (PI3K) pathway. The PI3K pathway also responds to stimuli from various growth factor receptors present on the cancer cell surface that, in turn, modulate downstream signaling cascades. Thus, the inositide signaling acts as a central node in the complex cellular signaling networks to impact cancer cell growth, motility, metabolism, and survival. Also, recent publications highlight the importance of PI3K signaling in stromal cells, whereby PI3K signaling modifies the tumor microenvironment to dictate disease outcome. The high incidence of mutations in the PI3K signaling cascade, accompanied by activation of parallel signaling pathways, makes PI3K a promising candidate for drug therapy. In this review, we describe the role of PI3K signaling in pancreatic cancer development and progression. We also discuss the crosstalk between PI3K and other major cellular signaling cascades, and potential therapeutic opportunities for targeting pancreatic ductal adenocarcinoma.

Targeting of stress response pathways in the prevention and treatment of cancer

The hallmarks of tumor tissue are not only genetic aberrations but also the presence of metabolic and oxidative stress as a result of hypoxia and lactic acidosis. The stress activates several prosurvival pathways including metabolic remodeling, autophagy, antioxidant response, mitohormesis, and glutaminolysis, whose upregulation in tumors is associated with a poor survival of patients, while their activation in healthy tissue with statins, metformin, physical activity, and natural compounds prevents carcinogenesis. This review emphasizes the dual role of stress response pathways in cancer and suggests the integrative understanding as a basis for the development of rational therapy targeting the stress response.

Evaluating the Metabolic Impact of Hypoxia on Pancreatic Cancer Cells

Hypoxia is frequently observed in human cancers and induces global metabolic reprogramming that includes an increase in glucose uptake and glycolysis, alterations in NAD(P)H/NAD(P)⁺ and intracellular ATP levels, and increased utilization of glutamine as the major precursor for fatty acid synthesis. In this chapter, we describe in detail various physiological assays that have been adopted to study the metabolic shift propagated by exposure to hypoxic conditions in pancreatic cell culture model that includes glucose uptake, glutamine uptake, and lactate release by pancreatic cancer cell lines. We have also elaborated the assays to evaluate the ratio of NAD(P)H/NAD(P)⁺ and intracellular ATP estimation using the commercially available kit to assess the metabolic state of cancer cells.

De Novo Lipid Synthesis Facilitates Gemcitabine Resistance through Endoplasmic Reticulum Stress in Pancreatic Cancer

Pancreatic adenocarcinoma is moderately responsive to gemcitabine-based chemotherapy, the most widely used single-agent therapy for pancreatic cancer. Although the prognosis in pancreatic cancer remains grim in part due to poor response to therapy, previous attempts at identifying and targeting the resistance mechanisms have not been very successful. By leveraging The Cancer Genome Atlas dataset, we identified lipid metabolism as the metabolic pathway that most significantly correlated with poor gemcitabine response in pancreatic cancer patients. Furthermore, we investigated the relationship between alterations in lipogenesis pathway and gemcitabine resistance by utilizing tissues from the genetically engineered mouse model and human pancreatic cancer patients. We observed a significant increase in fatty acid synthase (FASN) expression with increasing disease progression in spontaneous pancreatic cancer mouse model, and a correlation of high FASN expression with poor survival in patients and poor gemcitabine responsiveness in cell lines. We observed a synergistic effect of FASN inhibitors with gemcitabine in pancreatic cancer cells in culture and orthotopic implantation models. Combination of gemcitabine and the FASN inhibitor orlistat significantly diminished stemness, in part due to induction of endoplasmic reticulum (ER) stress that resulted in apoptosis. Moreover, direct induction of ER stress with thapsigargin caused a similar decrease in stemness and showed synergistic activity with gemcitabine. Our in vivo studies with orthotopic implantation models demonstrated a robust increase in gemcitabine responsiveness upon inhibition of fatty acid biosynthesis with orlistat. Altogether, we demonstrate that fatty acid biosynthesis pathway manipulation can help overcome the gemcitabine resistance in pancreatic cancer by regulating ER stress and stemness. Cancer Res; 77(20); 5503-17. ©2017 AACR.