Therefore, the hypothesis that the melanoma cells treatment with nanomolar concentrations of (Bu2Sn)2TPPS and (Bu3Sn)4TPPS induces DNA damage, elicits the increased expression of PARP-1 that, however, is not sufficient to repair an overwhelming amount of DNA damage and to avoid the consequent block of cell cycle. The gene discussed is PARP1; the disease is melanoma.