Furthermore, APOBEC3A was recently reported to have stronger deamination activity in breast cancer cell lines under certain conditions and to be the better correlate with mutation load in breast tumours compared with APOBEC3B24; to promote tumorigenesis in mouse models predisposed to cancer after overexpression25; and to contribute to recurrent mutations at DNA hairpins in cancer26,27. The gene discussed is APOBEC3A; the disease is breast cancer.