CDKN1B and prostate intraepithelial neoplasia: As shown in Table 4, PIN was identified in all p27 genotypes, with the lowest value in p27+/+ (1 in 15 animals), and its incidence and frequency increased in p27+/- (40% for incidence and 0.7 ± 0.3 for frequency) and progressed further in p27-/- mice (80% for incidence and 2.3 ± 1.2 (p < 0.05) for frequency).