Abstract 31: Metabolic reprogramming in ovarian cancer

Ovarian cancer is currently the most lethal gynecologic malignancy, with no new significant changes in treatment options for these patients in the last 30 years. Importantly, ovarian cancer patients have increased levels of lysophosphatidic acid (LPA), a bioactive phospholipid in ascites and serum that has been linked to driving oncogenesis and progression of ovarian cancer. Accumulating evidence has implicated Hypoxia-inducible factor-1α (HIF-1α) as a critical mediator of the glycolytic shift observed in cancer cells. However, the precise biological role of LPA in regulating HIF-1α-mediated glycolytic shift is largely unknown. Therefore, we were interested in examining the potential role of LPA in promoting metabolic reprogramming in ovarian cancer via HIF-1α signaling. In this study, we identified a novel mechanism by which LPA upregulates HIF-1α expression via Gαi2 (the gip2 oncogene) in human ovarian cancer cells. This study demonstrates that LPA induces a glycolytic shift via LPA-mediated activation of Gαi2, which causes a subsequent upregulation of HIF-1α in ovarian cancer cells. Additionally, we show that LPA-signaling via Gαi2 induces an increase in the expression of Hexokinase-2 (HK2) and Glucose transporter 1 (GLUT1), which are known targets of HIF-1α. We also demonstrate that LPA induces an increase in extracellular acidification rate (ECAR) in a dose dependent manner in both ovarian cancer cell lines and in patient-derived cells taken from the ascites fluid of ovarian cancer patients using an XFe96 analyzer. Furthermore, we found that inhibition of Rac signaling caused a reduction in LPA-induced ECAR, identifying Rac as a critical downstream component of Gαi2-medidated increase of ECAR. Moreover, using NAC, an inhibitor of redox signaling, we found that this caused a decrease in LPA-induced ECAR in SKOV3-ip cells, indicating that inhibition of redox signaling abolishes LPA-induced ECAR in ovarian cancer cells. Similarly, the use of EUK-134, a scavenger of superoxide and H2O2, also decreased LPA-induced increase in ECAR. Altogether, these results indicate that LPA regulates glycolysis through redox signaling via a Gαi2-Rac-HIF1α-dependent signaling pathway. Most importantly, the Gαi2-Rac-dependent pathway identified in this study more than likely serves as a potential driver of HIF-1α-mediated metabolic changes in ovarian cancer cells and represents a potential target for therapy in these patients. Citation Format: JI HEE HA, Rangasudhagar Radhakrishnan, Jeremy D. Ward, Muralidharan Jayaraman, Danny N. Dhanasekaran. Metabolic reprogramming in ovarian cancer. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 31.