Cholesterol desensitizes the response of endometrial cancer to progestin by attenuating progestin signaling

Progestin is the primary fertility-preserving treatment for patients with endometrial cancer (EC) and its precursor lesions, endometrial atypical hyperplasia (EAH); however, a subset of patients exhibits a poor response. In this study, through the analysis of serum lipid differences, we found that progestin-resistant patients with EC/EAH exhibited reduced serum apolipoprotein A-I concentrations and increased cholesterol accumulation in endometrial tissue. Mechanistically, molecular docking simulations and cellular models confirmed that cellular cholesterol interfered with progestin-driven signaling by competing with progestin for binding to progesterone receptor B (PRB), thereby impairing its phosphorylation, nuclear translocation, and downstream gene activation. Substitution of leucine 887 with alanine 887 in PRB disrupted cholesterol binding but preserved progestin responsiveness. Furthermore, cholesterol-lowering therapy with rosuvastatin calcium restored progestin sensitivity in animal models and in a single-arm, open-label phase 2 clinical trial. Our work shows that cholesterol accumulation contributes to progestin resistance and that combining progestin with statins may enhance therapeutic efficacy in EC.