Attenuation of Mdm2-p53 negative feedback loop by inhibitor administration allows for induction of apoptosis in PTEN-cancer cells at irradiation dose equal 1.6 Gy per day (Fig. 4C), while without inhibitor these cells remain resistant to repeated dose equal 10 Gy per day that induces persistent DNA damage (Fig. 2C). This evidence concerns the gene TP53 and cancer.