BBC3 and colorectal cancer: The mechanisms by which p53 causes apoptosis include the regulation of PUMA expression, free radicals generation within mitochondrial components, reduction of COX-2, PGE2 synthesis and the induction of death receptor 5 [54] The mutation in p53 leads to oncogenesis, and about half of all colorectal cancers are associated with Tp53 mutations [55] (Fig. 2).