PARP1 and neoplasm: All the results we analyzed share a unique leitmotif, and apart for few nutraceuticals taken into exams, the best characterized molecular effects involved in radiosensitization of tumors are: The activation of pro-apoptotic signals as demonstrated by their overall ability to induce downregulation of BCL-2, increase of PARP and Caspase-3 cleavage; a wide-ranging increase of cells blocked in the G2/M cell cycle phase which is, in fact, the most responsive stage of mitosis to IR; a frequent inhibition of HIF-1α and VEGF and thus of tumor angiogenesis.