In sum, these data indicated that SNAIL1 played a critical role in the growth of the primary tumor in the context of wild type p53, but also that tumor cell SNAIL1 influenced breast cancer metastasis in both a spontaneous MMTV-PyMT p53 wild type genetic model and a p53 null syngeneic orthotopic transplant model, suggesting a p53-independent role of Snail1 in metastastic progression. Here, TP53 is linked to breast cancer.