TP53 and breast cancer: To date, only a small number of studies have investigated the role of the APOBEC family of enzymes in breast cancer tumourigenesis [32, 33], but indicate that over-activity of these enzymes can cause cell cycle deviation, DNA fragmentation and γH2AX accumulation, and C to T mutation implicating a chronic source of DNA damage that may select for TP53 inactivation [34].