ESR1 and breast cancer: Other attempts at identifying epigenetic markers including targeted approach by examining gene-specific methylation markers including the use of PITX2 methylation to predict anthracycline-based chemotherapy for triple-negative breast cancer and high-risk breast cancer [38, 39], to examine changes in the methylation levels in estrogen receptor-α promoter regions among triple-negative breast cancer patients [40], as well as global approach to identify HSD17B4 methylation as predictor of HER2-positive breast cancer to trastuzumab and chemotherapy [41].