Drug repurposing opportunities for breast cancer and seven common subtypes.

Breast cancer is a substantial global health problem, and drug repurposing provides novel opportunities to address the urgent need for therapeutics. According to significant Mendelian randomization (MR) results, we identified 26 genes for overall breast cancer, 25 genes for ER+ breast cancer and 4 genes (CASP8, KCNN4, MYLK4, TNNT3) for ER- breast cancer. In order to explore the differences between 5 intrinsic subtypes, we found 29 actionable druggable genes for Luminal A breast cancer, 2 genes (IGF2 and TNNT3) for Luminal B breast cancer, 1 gene (FAAH) for Luminal B HER2 negative breast cancer, and 3 genes (CASP8, KCNN4, and TP53) for triple-negative breast cancer. After colocalization analysis, we determined OPRL1 as a prioritized target in both overall and Luminal A breast cancer. Additionally, FES and FAAH were considered prioritized targets for ER+ breast cancer. Through molecular docking, crizotinib stand out as a prioritized FES target drug repurposing opportunity with the lowest binding energy (-10.13 kJ·mol^-1) and CCK-8 assay showed ER+ cell groups were more sensitive to crizotinib than ER- cell groups. In conclusion, OPRL1 was identified as a prioritized target for both overall and Luminal A breast cancer. Moreover, FES and FAAH were recognized as prioritized targets for ER+ breast cancer.