UBE2E2-induced p62 overexpression promotes Snail-mediated epithelial-mesenchymal transition and metastasis in ovarian cancer

Dissemination of ovarian cancer (OvCa) cells can lead to inoperable metastatic lesions in the bowel and omentum, which have a poor prognosis despite surgical and chemotherapeutical options. A better understanding of the mechanisms underlying metastasis is urgently needed. In this study, bioinformatics analyses revealed that UBE2E2, a less-studied ubiquitin (Ub)-conjugating enzyme (E2), was upregulated in OvCa and was associated with poor prognosis. Subsequently, we performed western blot analysis and IHC staining with 26 HGSOC and 26 normal ovarian tissue samples, which further confirmed that UBE2E2 protein is highly expressed in OvCa tissue but almost not expressed in normal tissue. Furthermore, the silencing of UBE2E2 blocked OvCa cell migration, epithelial-mesenchymal transition (EMT) and metastasis in vitro, whereas UBE2E2 overexpression exerted the opposite effects. Mechanistically, UBE2E2 promoted p62 accumulation and increased the activity of the Nrf2-antioxidant response element (ARE) system, which ultimately activated the Snail signaling pathway by inhibiting the ubiquitin-mediated degradation of Snail. Furthermore, our results confirmed that mutations in the active site cysteine (Cys139) impaired both the function and cellular distribution of UBE2E2. More importantly, the deletion of UBE2E2 reduced tumorigenicity and metastasis in a xenograft ovarian cancer mouse model. Taken together, our study findings reveal the role of the UBE2E2-Nrf2-p62-Snail signaling axis in OvCa and thus provides novel therapeutic targets for the prevention of metastasis in OvCa.