Mitochondrial Quality Control Adaptations Support Malignant Progression of Serous Ovarian Cancer Cells and Spheroids

Serous ovarian cancer is the 5th leading cause of cancer-related deaths in women, with a 30% survival rate when spread into the highly hypoxic and visceral peritoneal cavity. Despite efforts to treat this highly metastatic disease, traditional chemotherapeutic and cytoreductive therapies are unable to diminish or induce cell death of circulating metastases from colonizing secondary sites due to their genetic and histologic heterogeneity and development of drug resistance. The dissemination route for primary metastasis, however, is most often conserved to the peritoneal cavity, which is low in nutrients and hypoxic (1-2% O2). Cells exfoliated from the primary tumor will aggregate during migration, which elicits a survival signal to maintain viability in this environment. The underlying cellular and molecular changes involved with aggregation have yet to be determined. We have previously found that aggregation of murine ovarian surface epithelial (MOSE) cells present a more suppressed metabolic phenotype upon aggregation. My research sought to identify how the mitochondria were internally regulated to support malignant transformation, migration, and invasion through modulation of quality control, mitochondrial dynamics, mitophagy, and mitobiogenesis. We have shown that aggregation of cancer cells supports increased mitochondrial fragmentation localized to the hypoxic core of our spheroid models. Further, aggregation supports enhanced viability through an upregulation of cancer genetic pathways associated with cell death, proliferation, stemness, and epithelial mesenchymal transition (EMT). Nutrient deprivation during migration further enhanced mitochondrial fragmentation and induction of mitophagy to prevent activation of apoptosis. Additionally, we have identified a phenotypic switch from enhanced mitophagy during peritoneal dissemination that supports survival of ovarian cancer cell aggregates to mitochondrial biogenesis during secondary tissue colonization that enables proliferation upon invasion. We have associated these changes with an increased bioenergetic proliferative niche through inhibition of proliferation, migration, and mitochondrial translation. This research has contributed to the understanding for the role of mitophagy as a survival rather than apoptotic signal in cancer cells as adaptation to nutrient-deprived environments, while also identifying how these processes can be reversed upon adhesion to support invasion and metastatic capacity during secondary colonization. This research is significant because it will identify molecular adaptations associated with the viability of disseminating cancer metastases as well as promote novel preventative therapeutics that can be used to limit the mortality of highly aggressive ovarian cancer in women.