We have previously shown that protein kinase C (PKC) acts upstream of caspases to regulate cisplatin-induced apoptosis. Since extracellular signal-regulated kinases (ERKs) have also been implicated in DNA damage-induced apoptosis, we have examined if ERK signaling pathway acts downstream of PKC in the regulation of cisplatin-induced apoptosis. PKC activator PDBu induced ERK1/2 phosphorylation which was inhibited by general PKC inhibitor bisindolylmaleimide and Go 6983 as well as the MEK inhibitor U0126 but not by the PKC delta inhibitor rottlerin. Cisplatin caused a concentration-dependent activation of ERK1/2 in HeLa cells. The level of ERK2 was decreased in HeLa cells that acquired resistance to cisplatin (HeLa/CP). The MEK inhibitor U0126 inhibited cisplatin-induced ERK activation and attenuated cisplatin-induced cell death. Inhibition of PKC delta by rottlerin or depletion of PKC delta by siRNA inhibited cisplatin-induced ERK activation. These results suggest that cisplatin-induced DNA damage results in activation of ERK1/2 via PKC delta. (c) 2005 Elsevier Inc. All rights reserved.