Transcriptional activation of caspase-6 and -7 genes by cisplatin-induced p53 and its functional significance in cisplatin nephrotoxicity.

This study examined the role of cisplatin-induced p53 activation in regulation of caspases and cellular injury during cisplatin nephrotoxicity. The executioner caspase-6 and -7 but not caspase-3 were identified as transcriptional targets of p53 in cisplatin injury as revealed by chromatin immunoprecipitation, a reporter gene and electrophoretic mobility shift assays, and real-time PCR following overexpression and inhibition of p53. DNA binding by p53 involved the first introns of the human and mouse caspase-7 gene and the mouse caspase-6 gene. Studies in human kidney, breast, ovary, colon, and prostate tumor cell lines also validated these findings. Treatment of p53 (-/-) cells with cisplatin did not induce caspase-6 and -7 expression and subsequent activation. In caspase-3 (-/-) cells, inhibition of caspase-6 and -7 activations markedly prevented cisplatin-induced cell death. In an in vivo model of cisplatin nephrotoxicity inhibition of p53 activation by a p53 inhibitor suppressed transactivation of the caspase-6 and -7 genes and prevented renal failure. p53 (-/-) mice were resistant to cisplatin nephrotoxicity as assessed by renal function and histology. These studies provide first evidence for p53-dependent transcriptional control of the caspase-6 and -7 genes and its functional significance in cisplatin injury to renal cells and functional implication of cisplatin-induced p53 induction in vitro and in vivo in cisplatin nephrotoxicity.