APOBEC3B and neoplasm: The expression of A3B was also significantly elevated in tumor tissues from patients of all three genotypes, but its expression was about 5- to 20-fold lower than that of A3A. Next, we examined the prevalence and expressional consequence of this deletion polymorphism in the second cohort (143 of 188 individuals were genotyped: A3B−/−, n = 27; A3B+/−, n = 89; and A3B+/+, n = 27).