TP53 and neoplasm: Wild-type TP53 clearly acts as a negative regulator of cell growth, but considering TP53 mutations solely as LOF mutations would prevent a full understanding of how TP53 mutations drive tumor growth, as TP53 status in human cancer is often defined in binary terms, wild-type versus inactivated, despite accumulating evidence that the majority of mutant p53 proteins are heterogeneous oncogenic proteins with multiple GOF activities and with potential as therapeutic targets.