PO-257 Loss of the mitochondrial pyruvate carrier drives ‘glutamine addiction’, a hallmark of aggressive ovarian cancers

Abstract

IntroductionOvarian cancer is the sixth most common cause of cancer deaths in females in the UK. High-grade serous ovarian cancer (HGSOC) comprises 75% of epithelial ovarian carcinomas. Patients with HGSOC initially respond well to platinum-based chemotherapy, but most relapse with therapy resistant disease.Cancer cells that adapt to their metabolic microenvironment, known as ‘metabolic flexibility’, are more likely to proliferate, metastasise, and be resistant to therapy. In the ascitic fluid of ovarian cancer, glucose concentrations are 3 times lower than in blood, although glutamine concentrations are comparable (0.4 mM vs 0.5 mM, respectively). Consequently, aggressive ovarian cancers have adapted to use glutamine rather than glucose as a fuel source. This phenomenon is termed ‘glutamine addiction’.Mitochondrial pyruvate carrier (MPC) is responsible for transporting pyruvate, generated through glycolysis, into mitochondria to enable oxidative phosphorylation (OXPHOS). Up to 90% of ovarian cancers have low MPC1 expression, which correlates strongly with poor prognosis across a wide variety of cancers. We postulated that deletion of MPC may force ovarian cancer cells to use glutamine as a fuel source enabling their survival in glucose limited environments.Material and methodsUsing ovarian cancer cell lines characterised as glutamine-addicted (SKOV3) or glutamine-independent (OVCAR3) as exemplars, the impact of MPC1 on ovarian cancer cell metabolism was investigated by quantitative PCR, Western blotting, metabolic assays and the Seahorse XF Analyzer.Results and discussionsThe importance of glutamine to an invasive phenotype is indicated by the observation that SKOV3 cells but not OVCAR3 cells were migratory in the presence of glutamine. The functional significance of MPC as an important link between glycolysis and OXPHOS was shown by inhibiting MPC biochemically with UK5099. UK5099 altered glutamine-independent OVCAR3 cells to emulate SKOV3 cells driving a switch to glutamine metabolism for OXPHOS. Whereas, non-inhibited OVCAR3 cells, even in glucose free media, did not utilise glutamine for OXPHOS.ConclusionThe ability to model the switch from glutamine-independent to glutamine-addicted in ovarian cancer cells will allow us to investigate the metabolic and genetic changes that occur in progression from a low- to a highly-invasive cancer phenotype of ovarian cancer. This in turn will provide therapeutic targets to halt or slow ovarian tumour progression.