TP53 and neoplasm: Because increased metastatic potential has also been commonly observed with gain-of-function mutants of p53 [43,44], and p53 R175H was shown to promote in vitro cell migration as well as in vivo tumor metastasis [44], we looked for genes that may contribute to these activities among the list of genes most highly expressed in the MMTV-Hras/p53R172H/R172H tumors.