TP53 and adenoma: Surprisingly, given the proposed role for loss of function mutations of the P53 gene in the development of human colorectal cancer, Clarke, Cummings & Harrison (1995) found no evidence for either an increase in the rate of adenoma formation in Apc+/-p53-/- animals, or an increased rate of progression to malignancy compared with Apc+/-p53+/+mice.