RARRES1 and breast cancer: In order to seek a proof that methylated region P indeed silenced RARRES1 expression, we correlated the methylation of RARRES1 promoter with expression of transcript in not only breast cancer cell lines classified into 3 different subtypes, i.e. luminal, basal and mesenchymal [15], [18], but also in the non-neoplastic breast cell line (MCF10A) and primary normal human mammary epithelial cells derived from different women (HMEC-1, -2, and -3).