To define the nature by which Sag deficiency suppressed the development of prostate cancer, we determined the effect of Sag on proliferation and apoptosis by immuno-staining the prostate tissues from 6 month-old mice with genotypes of PtenPC-/-;SagPC-/- vs. PtenPC-/-;Sag+/+ with proliferation markers Ki67 and BrdU, and apoptosis markers caspase-3 and TUNEL. This evidence concerns the gene MKI67 and prostate carcinoma.