Ovarian cancer (OvCa) patients respond to platinum and paclitaxel based therapies initially. However, almost 40-50% patients develop tumor recurrence within 3 years due to drug resistance. Therefore, newer drug targets and therapies are required. It is known that, metabolic alterations play crucial roles in the development of therapeutic resistance. Unlike normal cells, cancer cells metabolize glucose by aerobic glycolysis where glucose is converted to pyruvate and then to lactic acid which causes immunosuppression in tumor micro-environment. In contrast, in normal cells, the presence of oxygen inhibits glycolysis and pyruvate is converted to carbon dioxide (CO2) and water (H2O). Conversion of glucose to lactic acid even in the presence of oxygen is called aerobic glycolysis or the “Warburg effect”- named after the Nobel Laureate Otto Warburg. Warburg effect is connected to several molecular alterations like oncogenic activation and loss of tumor suppressor function. Therefore, pharmacologic inhibition of glycolysis has emerged as a novel strategy in cancer treatment since high rate of glycolysis is considered as metabolic hallmark of cancer. Some of these inhibitors have progressed into clinical trials but were not applied in routine clinical practice due to other complications. Hence, identifying other molecular alterations in OvCa and targeting them with novel molecular targets are critical. 6-phosphofructo-2-kinase/fructose-2,6-biphosphatase 3 (PFKFB3), a critical control point in glycolytic flux has been recently reported to be overexpressed in different cancers. However, the activity level of PFKFB3 in OvCa and the possibility of therapeutically targeting this molecule have not been tested. Our initial results showed a higher protein expression of phosphorylated (active) form of PFKFB3 in chemoresistant ovarian tumors. Our preliminary data also showed that, PFK-158, a novel drug, inhibits the active form of PFKFB3, decreases glucose uptake and induces more cell death in the resistant cells compared to their sensitive counterparts. Interestingly, we overserved a higher lipid accumulation in the form of cytoplasmic lipid droplets (LDs) in the chemoresistant cells. LDs contain triglycerides and neutral lipids, are associated to signaling, membrane trafficking and inflammation. LDs are often overexpressed in different cancers. PFKFB3 inhibition degraded LDs and decreased the protein expression of PLA2G3 (LD associated protein) whereas autophagy was elevated. Our findings indicate an intricate relationship between glycolytic inhibition, altered lipid metabolism and autophagy. Targeting both glycolytic and lipid pathways, shows a better potential of PFK-158 as a potent anti-cancerous drug. Therefore, we hypothesize that pharmacological inhibition of the active form of PFKFB3 could be useful to treat highly chemoresistant ovarian tumors. In this study, we will test the anticancer activity of PFK-158 both in vitro and in vivo. The proposed study will lead to better understanding of pathways regulated by metabolic inhibitors in promoting chemoresponse in resistant OvCa cells that can be translated into meaningful clinical trials.
This grant is made possible in part through a generous donation from Frances and Leon Hyman in memory of Barbara Skydel.