The down-regulation of RASD1 (RAS, dexamethasone-induced 1), a potential miR-375 target that negatively regulates ER alpha expression in breast cancer further confirms that the genes involved in the estrogen receptor regulated pathways could be under permanent transcriptional modification as a manifestation of a higher degree of cell differentiation of the parous breast, in spite of the lack of transcriptomic differences in the levels of the receptor between parous and nulliparous breast tissues. This evidence concerns the gene ESR1 and breast cancer.