Salinomycin inhibits SREBP1 to sensitize ferroptosis and ameliorate sorafenib resistance in clear cell renal cell carcinoma

Abstract

Backgrounds

Resistance to sorafenib, a frontline therapy for advanced ccRCC, is associated with decreased sensitivity to ferroptosis. Our research focuses on elucidating the mechanisms underlying ccRCC's resistance to sorafenib-induced ferroptosis and identifying potential new agents that could overcome this resistance.

Methods

The silencing of SREBP1 was employed to evaluate the role of this key transcription factor in lipid synthesis and its contribution to ferroptosis resistance in sorafenib-treated ccRCC cells. The ATF4-mediated induction of SREBP1 following salinomycin treatment was assessed by western blot, RT-PCR, immunohistochemistry, chromatin immunoprecipitation, and dual-luciferase reporter assays. In cultured ccRCC cells, the combined effects of salinomycin and sorafenib on ferroptosis induction were evaluated by assessing cell viability, glutathione levels, malondialdehyde levels, BODIPY fluorescence, and intracellular Fe²⁺ concentration. In an orthotopic ccRCC mouse model, the synergistic effects of salinomycin and sorafenib on both ferroptosis and tumor progression were examined.

Results

Overexpression of SREBP1 was observed in ccRCC tumor tissue, and induced by sorafenib treatment. Silencing SREBP1 reduced the resistance of ccRCC cells to ferroptosis induced by sorafenib. Salinomycin decreased ATF4 level, which in turn inhibited SREBP1 transcription. Treatment with salinomycin enhanced the sensitivity of ccRCC cells to sorafenib-induced ferroptosis. In the orthotopic xenograft mouse model of ccRCC, the combination of salinomycin and sorafenib showed a synergistic effect in inducing ferroptosis inhibiting tumor growth.

Conclusions

Salinomycin treatment mitigates resistance to sorafenib-induced ferroptosis by inhibiting SREBP1. The combination of salinomycin and sorafenib synergistically enhances ferroptosis and suppresses ccRCC growth.