Biochem/physiol Actions
Pifithrin-α is a reversible inhibitor of p53-mediated apoptosis and p53-dependent gene transcription such as cyclin G, p21/waf1, and mdm2 expression. 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. The protective effect is not seen in p53-null mice or cells expressing a dominant negative mutant of the p53 gene. Protection is conferred by the transient expression of p53 in p53-deficient cell lines.