To investigate possible mechanisms underlying this radiosensitizing effect, we evaluated the induction of DNA double-stranded breaks (DSB) by detecting 53BP1, a protein that co-localizes with DSB, 0.5 h after irradiation with 2Gy as well as residual DSB levels 24 h following irradiation in tumor cells treated or not with 0.2 μM Pt-ctpy. Here, TP53BP1 is linked to neoplasm.