microRNA-509-3p Intercepts Metabolic Reprogramming by Targeting Multiple Driver Genes of Glycolysis and Glutaminolysis to Sensitize Ovarian Tumors to Chemotherapy

Chemotherapy resistance is a recurring obstacle across cancer types, with over 90% of patient mortality related to drug-resistance. This dissertation explores the potential of microRNA-509-3p (miR-509-3p), a tumor suppressor microRNA, as a chemo-sensitizing agent in osteosarcoma (OS) as well as ovarian cancer. In the case of OS, migration and chemo-resistance are the biggest challenges to overall survival. Here, we demonstrate the potential of miR-509-3p in significantly disrupting the migration of primary and metastatic OS cell lines. We then show the potential of a critical down-stream target of miR-509-3p, AXL in chemo-sensitizing as well. Epithelial ovarian cancer (EOC) is one of the most responsive to chemotherapy initially. However, a majority of the patients relapse with drug-resistant tumors resulting in a low five-year survival rate of 30%. Tumors stressed by rounds of chemotherapy, undergo metabolic reprogramming and rely heavily on glycolysis for the rapid production of ATP to sustain the energy to maintain drug resistance. miR-509-3p is positively correlated with overall survival in the TCGA ovarian cancer cohort. Here, we show that miR-509-3p targets key drivers of metabolism sensitizing p53mut ovarian cancer xenografts to cisplatin. Six of the twelve driver genes of glycolysis, two of four driver genes of glutaminolysis and a critical protein involved in autophagy were strongly predicted miR-509-3p targets, down-regulated upon miR-509-3p over-expression treatment of EOC cell lines. Metabolomic studies revealed that miR-509-3p down-regulates metabolites in glycolysis, glutaminolysis and the TCA cycle. ETS1, PGM1, GLUD1, and LC3B were validated to be direct targets of miR-509-3p through dual-luciferase reporter assays. siRNA mediated knock-down of ETS1 was 94.8% as effective as miR-509-3p at chemo-sensitization, highlighting ETS1 as a critical down-stream effector of miR-509-3p and potential druggable target for chemo-sensitization of EOC. Finally, we show that miR-509-3p works with cisplatin to improve survival in p53-mutant ovarian cancer xenografts. Therapeutically targeting any one of the three major energy producing pathways is a popular strategy in clinical trials. However, since it can always be rescued by another metabolic pathway, the ability of miR-509-3p to cripple all three simultaneously reveals a new strategy for overcoming drug resistance through metabolic targeting of tumors treated with chemotherapy.