APOBEC3B and cancer: Whereas many studies have focused on the molecular roles of APOBEC3B, and to some extent APOBEC3A, possible cumulative effects of action of APOBEC3A, APOBEC3B, UNG, REV1, and FHIT on generation of APOBEC3B-like mutation motifs and on drug sensitivity in cancer have not been clearly elucidated.