Our results suggest that the PIAS1 epigenetic pathway, which has been previously shown to function in regulatory T cell differentiation [24], is up-regulated in breast cancer and is involved in promoting DNA methylation and epigenetic silencing of breast cancer signature genes such as ESR1 and CCND2, as well as the breast tumor suppressor WNT5A. This evidence concerns the gene PIAS1 and breast neoplasm.