title: PCK2 activation mediates an adaptive response to glucose depletion in lung cancer.
abstract: Cancer cells are reprogrammed to utilize glycolysis at high rates, which provides metabolic precursors for cell growth. Consequently, glucose levels may decrease substantially in underperfused tumor areas. Gluconeogenesis results in the generation of glucose from smaller carbon substrates such as lactate and amino acids. The key gluconeogenic enzyme, phosphoenolpyruvate carboxykinase (PEPCK), has been shown to provide metabolites for cell growth. Still, the role of gluconeogenesis in cancer is unknown. Here we show that the mitochondrial isoform of PEPCK (PCK2) is expressed and active in three lung cancer cell lines and in non-small cell lung cancer samples. PCK2 expression and activity were enhanced under low-glucose conditions. PEPCK activity was elevated threefold in lung cancer samples over normal lungs. To track the conversion of metabolites along the gluconeogenesis pathway, lung cancer cell lines were incubated with (13)C₃-lactate and label enrichment in the phosphoenolpyruvate (PEP) pool was measured. Under low glucose, all three carbons from (13)C₃-lactate appeared in the PEP pool, further supporting a conversion of lactate to pyruvate, via pyruvate carboxylase to oxaloacetate, and via PCK2 to phosphoenolpyruvate. PCK2 small interfering RNA and the pharmacological PEPCK inhibitor 3-mercaptopicolinate significantly enhanced glucose depletion-induced apoptosis in A549 and H23 cells, but not in H1299 cells. The growth of H23 multicellular spheroids was significantly reduced by 3-mercaptopicolinate. The results of this study suggest that lung cancer cells may utilize at least some steps of gluconeogenesis to overcome the detrimental metabolic situation during glucose deprivation and that in human lung cancers this pathway is activated in vivo.
authors.affiliation: Division of Pulmonology, Department of Internal Medicine, Medical University of Graz, Graz, Austria.
authors.forename: K
authors.initials: K
authors.lastname: Leithner
authors.affiliation: 1] Division of Pulmonology, Department of Internal Medicine, Medical University of Graz, Graz, Austria [2] Ludwig Boltzmann Institute for Lung Vascular Research, Graz, Austria.
authors.forename: A
authors.initials: A
authors.lastname: Hrzenjak
authors.affiliation: Core Facility Mass Spectrometry and Lipidomics, Center for Medical Research, Medical University of Graz, Graz, Austria.
authors.forename: M
authors.initials: M
authors.lastname: Trötzmüller
authors.affiliation: Institute of Molecular Biosciences, Karl Franzens University, Graz, Austria.
authors.forename: T
authors.initials: T
authors.lastname: Moustafa
authors.affiliation: Core Facility Mass Spectrometry and Lipidomics, Center for Medical Research, Medical University of Graz, Graz, Austria.
authors.forename: H C
authors.initials: HC
authors.lastname: Köfeler
authors.affiliation: Division of Pulmonology, Department of Internal Medicine, Medical University of Graz, Graz, Austria.
authors.forename: C
authors.initials: C
authors.lastname: Wohlkoenig
authors.affiliation: Institute of Pathology, Medical University of Graz, Graz, Austria.
authors.forename: E
authors.initials: E
authors.lastname: Stacher
authors.affiliation: Division of Thoracic and Hyperbaric Surgery, Department of Surgery, Medical University of Graz, Graz, Austria.
authors.forename: J
authors.initials: J
authors.lastname: Lindenmann
authors.affiliation: Weatherall Institute of Molecular Medicine, University of Oxford, Oxford, UK.
authors.forename: A L
authors.initials: AL
authors.lastname: Harris
authors.affiliation: 1] Ludwig Boltzmann Institute for Lung Vascular Research, Graz, Austria [2] Experimental Anesthesiology, University Clinic for Anesthesiology and Intensive Care Medicine, Medical University of Graz, Graz, Austria.
authors.forename: A
authors.initials: A
authors.lastname: Olschewski
authors.affiliation: Division of Pulmonology, Department of Internal Medicine, Medical University of Graz, Graz, Austria.
authors.forename: H
authors.initials: H
authors.lastname: Olschewski
mesh_terms: D000091162:AMP-Activated Protein Kinase Kinases; D000222:Adaptation, Physiological / Q000235:genetics; D002289:Carcinoma, Non-Small-Cell Lung / Q000378:metabolism* / Q000473:pathology; D004305:Dose-Response Relationship, Drug; D005943:Gluconeogenesis / Q000235:genetics; D005947:Glucose / Q000172:deficiency* / Q000494:pharmacology; D006801:Humans; D008175:Lung Neoplasms / Q000378:metabolism* / Q000473:pathology; D019764:Phosphoenolpyruvate Carboxykinase (ATP) / Q000235:genetics / Q000378:metabolism*; D017346:Protein Serine-Threonine Kinases / Q000235:genetics; D011518:Proto-Oncogene Proteins / Q000235:genetics; D016283:Proto-Oncogene Proteins p21(ras); D014407:Tumor Cells, Cultured; D016159:Tumor Suppressor Protein p53 / Q000235:genetics; D018631:ras Proteins / Q000235:genetics
chemical_list: C117307:KRAS protein, human; D011518:Proto-Oncogene Proteins; C495901:TP53 protein, human; D016159:Tumor Suppressor Protein p53; D017346:Protein Serine-Threonine Kinases; C109790:STK11 protein, human; D000091162:AMP-Activated Protein Kinase Kinases; D016283:Proto-Oncogene Proteins p21(ras); D018631:ras Proteins; C000597251:PCK2 protein, human; D019764:Phosphoenolpyruvate Carboxykinase (ATP); D005947:Glucose