Three such human-viral homologs are used in the analysis: V-ABL of the acutely transforming retrovirus A-MuLV, Bo17 of herpesvirus BoHV-4 (a model virus for oncogenic gammaherpesviruses such as EBV and KSHV and implied in several animal cancers [69]) and gag of HERV-K(HML2)22I, a class of human endogenous retroviruses associated with some forms of breast cancer [70]). This evidence concerns the gene ABL1 and breast cancer.