Similarly, previous studies by Montales et al. (2012) demonstrated that genistein inhibits the formation of CSC spheres originating from human breast tumors, showing that the lowest dose of genistein (40 nM) consistently attenuated the formation of primary and secondary mammospheres from transformed cell lines and primary epithelial cells isolated from BC cells (MCF-7 (expressing ERα) and MDA-MB-231). This evidence concerns the gene ESR1 and breast cancer.