ETV4 promotes ovarian cancer growth by regulating mitochondrial function through Mfn2 ubiquitination mediated by the E3 ubiquitin ligase MARCH9.

BACKGROUND: Mitochondrial dysfunction affects the development of ovarian cancer (OC). ETV4 is involved in mitochondrial fusion. The regulatory pathways of ETV4 in OC cells have not been further investigated. In this study, we aimed to explore the effects of ETV4 on OC development and analyze the downstream regulatory pathways of ETV4. METHODS: The expression of ETV4 in OC cell lines (SK-OV-3, HEY, A2780, and OVCAR-3) was verified. After silencing ETV4, indicators related to mitochondrial function, including ATP level, mitochondrial membrane potential, mitochondrial DNA (mtDNA), and mitochondrial ROS (mtROS), were analyzed. The expression of mitochondrial fission/fusion-related markers (Mfn1, Mfn2, OPA1, DRP1, MFF, and FIS1) was detected. In vivo experiments were used to verify the effect of ETV4 on OC development. RESULTS: The TCGA-OV data indicated that ETV4 was highly expressed in OC. Silencing ETV4 inhibited the proliferation of OC cells. Mitochondrial membrane potential and ATP levels increased after ETV4 silencing, while mtDNA and mtROS levels decreased. ETV4 silencing promoted Mfn2 protein expression but did not affect Mfn2 mRNA level. Mfn2-associated E3 ubiquitin ligase MARCH9 was targeted and regulated by ETV4. MARCH9 overexpression alleviated the regulation of ETV4 silencing on mitochondrial function in OC cells. Lysosomal inhibitor CQ blocked the degradation of ubiquitinated Mfn2 protein. MARCH9 was found to mediate robust ubiquitination of Mfn2 via the K63-linked ubiquitination. CONCLUSIONS: ETV4 was highly expressed in OC and involved in the regulation of mitochondrial function. ETV4 regulated Mfn2 ubiquitination linked by K63 by regulating MARCH9.