HAP1 and urinary bladder neoplasm: To determine whether APOBEC3A or APOBEC3B was the predominant deaminase, we compared our BKPyV infection models of urothelial carcinogenesis and patient bladder tumor data (21) to a Hap1 cell line model [with overexpression of APOBEC3A or APOBEC3B in isolation (18); Fig. 6].