E3 Ubiquitin Ligase RNF126 Promotes Ovarian Cancer Progression and Cisplatin Resistance Through Targeting Numb/Notch1...

RING finger protein 126 (RNF126) is an E3 ubiquitin ligase that is overexpressed in various malignancies. However, its role in ovarian cancer remains poorly understood.

Ovarian cancer cell lines, including SKOV3, A2780, and cisplatin-resistant SKOV3/DDP, were utilized in this study. RNF126 expression was modulated via lentiviral transduction. Cell viability, colony formation, and migration were assessed by cell counting kit-8 (CCK-8), colony formation, and Transwell assays. Protein and mRNA levels were measured by Western blotting and real-time quantitative PCR (qPCR). Protein interaction was evaluated by co-immunoprecipitation and ubiquitination assays. In vivo tumor growth and cisplatin response were examined using a xenograft model.

In SKOV3 and A2780 cells, RNF126 overexpression promoted proliferation, colony formation, and migration, while its knockdown produced the opposite effects. Notably, elevated RNF126 expression was observed in the cisplatin-resistant SKOV3/DDP line. Silencing RNF126 in these cells increased cisplatin sensitivity while concurrently reducing proliferative capacity, clonogenicity, and migratory potential. RNF126 depletion in SKOV3/DDP cells led to decreased mRNA and protein expression of Notch1 and its downstream targets Myc, Cyclin D3, and Hes1. Meanwhile, Numb mRNA levels remained unchanged, whereas its protein levels increased, indicating post-transcriptional regulation. Furthermore, Numb silencing increased cell viability, clonality, migration, and Notch signaling activation in RNF126 knockdown SKOV3/DDP cells. In vivo, silencing RNF126 markedly enhanced the sensitivity of cells to cisplatin, suppressed tumor growth, and inhibited Myc, Cyclin D3, Hes1, and Notch1 protein expression. Silencing Numb can reverse the inhibitory effects of RNF126 knockdown. Mechanistic studies showed that RNF126 directly binds to the Notch signaling inhibitor Numb and mediates its ubiquitination and proteasomal degradation, thereby activating the Notch1 signaling pathway and upregulating its downstream genes. In addition, analysis of the TCGA dataset revealed that elevated RNF126 expression is a significant prognostic factor associated with increased mortality risk in ovarian cancer.

These findings establish RNF126 as a critical contributor to cisplatin resistance in ovarian cancer via regulation of the Numb/Notch1 pathway and highlight its potential as a therapeutic target to counteract chemoresistance.