Therefore, the expression of cyclin D1, a key regulator mainly of the G1/S [42] but also of the G2/M phases, was analysed by western blot experiments (Figure 6) on A375, HT-144 and M74 melanoma cells treated as reported for 24 h, 48 h and 72 h with (Bu2Sn)2TPPS and with (Bu3Sn)4TPPS. Here, CCND1 is linked to melanoma.