Abstract 3093: Nix mediated mitophagy maintains ovarian cancer cell stemness

Abstract

Abstract Ovarian cancer is the most frequent cause of death among gynecologic malignancies. Despite the availability of effective therapeutics against cancer, the overall 5-year survival rate of ovarian cancer is still ~30-40%. Most of the lethality are due to cancer relapse and drug resistance, where cancer stem cells (CSCs) are supposed to be the key regulators. CSCs also known as tumor-initiating cells, are a small subgroup of tumor cells that can develop tumors through their capability of self-renewal and differentiation. CSCs can canonically nurture therapeutic resistance, tumor invasion, metastasis, and recurrence, which tremendously attract the scientific community for the unique CSC-based cancer therapeutics. While changing phenotypical features of CSCs complicates their identification and thereby metabolism-based alternate strategy seems to be worthy anti CSC therapy. Though autophagic degradation of mitochondria (mitophagy) based mitochondrial dynamics endowed cancer cells with stemness, but wide informational gaps and missing mechanistic knowledge further necessitates the study on mitophagy dependent CSC regulation. In this study, we investigated the potential involvement of mitophagy in maintenance of cancer cell stemness. In our experimental conditions, FACS sorted CD117/44+/+, ALDHbr and ovarian cancer stem cell like cells (CSCLCs) from OVACR4 and OVCAR3 cells showed higher mitochondrial translocation of cytosolic LC3 that directly indicates the progression of mitophagy in these subpopulations. Reduced mitocontent in CSCLCs as compare to bulk cells also supports the mitochondrial degradation. To analyze the involvement of mitophagy in stemness, mitophagy has been targeted with mDIVI a well-known mitophagy inhibitor, which downregulate the sphere forming ability and protein levels of stemness marker such as SOX2 in ovarian cancer cells. Furthermore, the mechanistic detail of mitophagy involvement in cancer stemness were evaluated. Among different mitophagy proteins, BNIP3L/NIX is highly expressed in ALDHbr and CD117/44+/+ sorted cells as compare to ALDHdim and CD117/44-/- cells, respectively. The functional implication of NIX in ovarian CSCs was verified by gene silencing approach. NIX silencing diminished the sphere forming ability and stem cell marker OCT4 that supported its crucial involvement in ovarian cancer cells stemness. In summary, our findings provide a mechanistic detail of mitophagy underlying maintenance of the CSC population in ovarian cancer and suggest that targeting of NIX based mitophagy could be exploited for the eradication of CSC and thereby tumor recurrence and drug resistance in ovarian cancer. Citation Format: Tejinder Pal Khaket, Qi-En Wang. Nix mediated mitophagy maintains ovarian cancer cell stemness [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 3093.