BRCA1 and breast cancer: However, the altered methylation profile of many TSG promoter regions appears to have multiple functions as methylation markers: For example, the hypermethylation of the BRCA1 repair gene should serve as (i) a diagnostic marker where a methylation signature is proposed to predict a sporadic risk of developing breast cancer in BRCA1 mutation carriers; (ii) a prognostic marker that stratifies and predicts death in advanced diagnosis; (iii) a therapeutic marker that is also suggested to determine the sensitivity of breast and ovarian cancer to a cross-linking agent [19,20].