BCSCs, breast cancer stem cells; CARM1, coactivator-associated arginine methyltransferase 1; ceRNA, competing endogeneous RNA; ChIP, chromatin immunoprecipitation; CSCs, cancer stem cells; EMT, epithelial-mesenchymal transition; lncRNAs, long non-coding RNAs; MET, mesenchymal-epithelial transition; miRNAs, microRNAs; ncRNA, non-coding RNA; PcG, Polycomb group; PR, progesterone receptor; PRC2, Ploycomb repressive complex 2; SIRT2, sirtuin 2; SP, side population. This evidence concerns the gene PGR and cancer.