Pifithrin-α

Pifithrin-α (PFTalpha) is a reversible inhibitor of p53-mediated apoptosis and p53-dependent gene transcription such as cyclin G, p21/waf1, and mdm2 expression. It prevents p53-mediated apoptosis induced by cytotoxic compounds in C8 cells at 10 μM and in human umbilical vein endothelial cells at 30 μM. Pifithrin-α enhances cell survival after genotoxic stress such as UV irradiation and treatment with cytotoxic compounds including doxorubicin, etopoxide, paclitaxel, and cytosine-β-D-arabinofuranoside. Pifithrin-α protects mice from lethal whole body γ-irradiation without an increase in cancer incidence. Pifithrin-α can also protect cells from DNA damage-induced apoptosis by a p53-independent mechanism that might involve cyclin D1. In addition to p53, PFTalpha can suppress heat shock and glucocorticoid receptor signaling but has no effect on nuclear factor-kappaB signaling. Pifithrin-α (PFTalpha) reduces activation of heat shock transcription factor (HSF1) and increases cell sensitivity to heat. Moreover, Pifithrin-α reduces activation of glucocorticoid receptor and rescues mouse thymocytes in vitro and in vivo from apoptotic death after dexamethasone treatment.