While MCF-7-Control cells display molecular profiles characteristic of the luminal A (ER-positive, PR-positive, HER2-negative) breast cancer subtype, MCF-7-Snail cells were found to display molecular profiles characteristic of the aggressive triple-negative (ER-negative, PR-negative, HER2-negative), claudin-low breast cancer subtype. This evidence concerns the gene SNAI1 and breast cancer.