APOBEC3A and cancer: However, a germline polymorphism that effectively deletes APOBEC3B and stabilizes expression of APOBEC3A has been associated with higher burdens of SBS2 and SBS13 in breast cancers and indicates that, at least in some cancers, APOBEC3B cannot be responsible (Caval et al., 2014, Nik-Zainal et al., 2014).