The cytotoxicity of Ad.DD3.D55-PTEN was evaluated by MTT assay in three prostate cancer cell lines CL1, LNCaP, DU145, 22RV1, PC3 and two non-prostate cancer cell lines T24(human urinary bladder carcinoma cell line) and BEL-7404(human liver cancer cell line). This evidence concerns the gene PTEN and Familial prostate cancer.