A significant reduction in p53 transcript levels (compared to wild type) was noted in the tumor (P = 0.0003) as well as tissue surrounding the tumor (tumor microenvironment) (P = 0.0001) taken from the ESPL1+/hyp p53+/− mice, suggesting that loss of p53 function in the tumor tissue itself as well as tumor microenvironment was a rate limiting step in the progression of these tumors. This evidence concerns the gene TP53 and neoplasm.