Sequence variation of breast cancer genomes is shaped by a diversity of mutational processes [86], and further investigation is needed to establish whether the T(C>D)D motif in the breast cancer cell lines is predominantly generated by APOBEC3B and APOBEC3A and/or requires an additional role or REV1, UNG, and FHIT, or whether it involves other molecular mechanisms. Here, UNG is linked to breast cancer.