BMP2 and breast cancer: Based on the facts that CAFs are enriched in the breast cancer microenvironment and can induce EMT in breast cancer cells [12] and that BMP2 is elevated in primary breast cancer tissues [19], we hypothesized that the ectopically co-expressed BRGs may be derived from epithelial cancer cells that have undergone EMT and acquired cancer stem cells (CSCs) properties, followed by BMP2 induction in the tumor microenvironment.