The upregulation of PFKFB3/PDK4 enhances ovarian cancer stemness properties in tumor progression

Abstract

Background and Aims: Accumulating evidence shows that cancer stem cells (CSCs) in many cancers bear an altered metabolic phenotype, which relies on a switch from oxidative phosphorylation to glycolysis. However, such metabolic switch in ovarian CSCs remains unclear. Unlike other tumors, ovarian cancer prefers to metastasize through ascites. Here, roles of PFKFB3 and PDK4, two key enzymes involved in glycolysis, on CSCs properties in ovarian cancer cells derived from ascites were explored. Methods: Ovarian cancer cells/cell lines derived from primary ovarian tumor/ascites were used for sphere-forming culture and ALDH+CD44+ fluorescence-activated cell sorting. Effects of PFKFB3, PDK4, their inhibitors (PFK158, DCA) and miR-16-5p mimic on cancer cell glucose metabolism and stemness properties were studied using functional assays. mRNA and protein expression of related-genes were determined by qPCR and immunoblotting respectively. Results: Compared to primary ovarian tumor cells, cancer cells derived from ascites had increased sphere-forming and metastasis capacities, with increased ALDH and CD44 activities, and up-regulated PFKFB3 and PDK4 expression. ALDH+CD44+ cancer showed up-regulated PFKFB3 and PDK4 expression compared to ALDH-CD44- cells and showed enhanced tumor initiation and self-renewal in vitro and in vivo. We also found that miR-16-5p regulated PDK4 expression. PFKFB3 or PDK4 knock-down, inhibitors treatments and miR-16-5p mimic in ovarian CSCs led to decreased lactate production, sphere-forming, colony-forming and metastatic capacities, along with down-regulated stemness-genes expression. Overexpressed PFKFB3 or PDK4 in ALDH-CD44- cells displayed opposite effects. Conclusions: PFKFB3 and PDK4 play important roles in ovarian CSC properties and can be potential therapeutic molecular targets in cancer therapy.