BRCA1 and breast cancer: In addition, the growth of xenograft tumours with epigenetically silenced BRCA1 was reduced by PARP inhibitor treatment.41, 42 However, in a panel of 39 ovarian cancer cell lines representing all histologic subtypes, as well as in a panel of 21 breast cancer cell lines, methylation of the BRCA1 promoter was not detected.35, 43 Furthermore, according to The Cancer Genome Atlas (TCGA), unlike BRCA1/2 mutations, ovarian cancers with epigenetic silencing of BRCA1 through promoter hypermethylation appear not to respond as favourably to platinum and not to exhibit improved survival.