PPM1D and osteosarcoma: Previously, it was reported that the increased γH2AX levels correlates not only with more severe damage to DNA, but also with elevated DDR, including initiation of cell death program.24 Knowing the fact that, on one hand, Wip1 directly dephosphorylates γH2AX and, on another hand, Wip1 increases cytotoxicity of cisplatin, we decided to verify that in p53-negative Saos2-Wip1-ON osteosarcoma cells, levels of p-Ser139 γH2AX do not correlate with cisplatin-induced cell death.