TP53 and neoplasm: However, the notion that these are the sole tumor suppressive functions of p53 has been challenged by pivotal studies showing that certain p53 mutants, despite lacking the ability to transcriptionally regulate cell cycle and/or apoptosis, still retain tumor suppressor activity (Cosme-Blanco et al. 2007; Li et al. 2012; Liu et al. 2004; Valente et al. 2013).