TP53 and cancer: Therefore, in contrast to oncogenes that have a limited number of residues that can lead to a gain of function and tumor suppressor genes that need more drastic modifications such as indel events to display a loss of function, 55% of potential missense variants that can occur in the DBD of the p53 protein have been found in human cancer (at least 10x) and display a loss of activity, either complete or partial.