USP26-mediated stabilization of RAD51 promotes endometrial cancer progression and limits ferroptosis.

Background: Ferroptosis is increasingly implicated in endometrial cancer, but the role of the homologous recombination protein RAD51 in ferroptotic stress and its post-translational regulation remain unclear. Methods: RAD51 expression was assessed in GEO datasets, UCEC tissues, and endometrial cancer cell lines. RAD51 loss-of-function was evaluated using proliferation, cell-death, Transwell, ferroptosis-related, and xenograft assays. IP-MS, co-immunoprecipitation, cycloheximide chase, proteasome inhibition, ubiquitination assays, USP26-C304S, and RAD51 rescue experiments were used to define USP26-dependent RAD51 regulation. Results: RAD51 was upregulated in endometrial cancer and its depletion reduced proliferation and xenograft growth, lowered Transwell migration/invasion readouts, and increased ferroptosis-associated changes. USP26 associated with RAD51, reduced its ubiquitination, and stabilized RAD51 in a catalytic activity-dependent manner. RAD51 re-expression partially rescued the effects of USP26 depletion. Conclusions: The USP26-RAD51 axis supports endometrial cancer progression and limits ferroptosis-associated stress, identifying RAD51 protein stability as a potential mechanistic vulnerability.