TP53 and intestinal neoplasm: The Trp53flox allele is functionally Trp53-null, and treatment of ApcΔ716Trp53+/flox and ApcΔ716Trp53flox/flox mice with tamoxifen results in the expression of mutant p53R270H in intestinal tumor cells (hereafter, ApcΔ716Trp53+/R270H and ApcΔ716Trp53R270H/R270H).