We have demonstrated in a previous study that the M13HS-2 and -8 tumor hybrids co-expressed SNAIL and ZEB1, while parental human M13SV1-EGFP-Neo breast epithelial cells were only positive for SNAIL and human HS578T-Hyg breast cancer cells only expressed ZEB1 [52]. This evidence concerns the gene SNAI1 and breast cancer.