Clofibrate downregulates DNA damage response proteins via the MELK-AKT-mTOR axis in breast cancer.

A high-cholesterol diet is a risk factor for breast cancer (BC) progression. Clofibrate, a PPARα agonist, is implicated in lipid metabolism and tumor prevention, yet its precise mechanism in BC remains unclear. To investigate the mechanism of action of Clofibrate, we utilized the Therapeutic Target Database. We constructed models of MELK silencing and overexpression, and assessed the effects of Clofibrate, MELK silencing, and MELK overexpression on BC using clone formation assays, wound healing assays, apoptosis assays, and tumor-bearing mouse experiments. Western blot (WB) analysis was performed to detect the expression of HRD-related proteins (BRCA1, BRCA2, and RAD51) in BC cells after MELK silencing. Additionally, WB was used to examine the impact of Clofibrate on the expression of MELK protein and HRD-related proteins (BRCA1, BRCA2, and RAD51) in BC cells. Gene set enrichment analysis was conducted to explore the potential mechanism by which Clofibrate regulates HRD, with findings validated by WB. Clofibrate significantly inhibited proliferation, migration, and induced apoptosis in MDA-MB-231 cells. This anti-cancer effect was also observed in tumor-bearing mice. Mechanistically, Clofibrate treatment led to the downregulation of MELK and key HRD-related proteins (BRCA1, BRCA2, and RAD51). GSEA analysis and subsequent experimental validation further implicated the AKT-mTOR signaling axis as a potential downstream effector of MELK in this process. Taken together, our findings suggest that Clofibrate downregulates key DNA damage response proteins (BRCA1, BRCA2, and RAD51) in BC, an effect that is associated with suppression of the MELK-AKT-mTOR signaling pathway.