BRCA1 status was observed to be a determinant of the abundance of epithelial-like (ALDH1+) or mesenchymal-like (CD44+/24–/low) BCSCs, and the reconstitution of a full length, wild type BRCA1 in HCC1937 breast cancer cells possessing a mutated BRCA1, transforms them from ‘stem-like’ to more ‘mesenchymal’. This evidence concerns the gene ALDH1A1 and breast cancer.