Cell cycle arrest and cytochrome c-mediated apoptotic induction by MCS-5A is associated with up-regulation of p16(INK4a) in HL-60 cells

Abstract

MCS-5A, an analog of sangivamycin, selectively inhibits the cyclin-dependent kinases CDK1 and 4 in HL60 cells in vitro (IC50: 9.6 and 8.8 mu M, respectively), while weakly inhibiting other housekeeping protein kinases. MCS-5A effectively induces HL-60 cell cycle arrest at the G(1) and G(2)/M phases through direct inhibition of CDK1 and 4 activity. In addition, elevated expression of p16(INK4a) and a reduction in the level of hyperphosphorylated pRb showed that 3 mu M MCS-5A also induces p16(INK4a)-mediated cell cycle arrest at the G(1) phase. Furthermore, apoptotic induction in MCS-5A-treated HL-60 cells is associated with the release of cytochrome c from mitochondria, which, in turn, results in the activation of procaspase-8, -9 and -3, and the cleavage of poly(ADP-ribose) polymerase (PARP). In addition, the involvement of p16(INK4a) in this apoptotic induction was demonstrated using A549 cells with a homozygous deletion of p16(INK4a). Based on these results, we conclude that MCS-5A is a candidate therapeutic agent for the treatment of human promyelocytic leukemia via the up-regulation of p16(INK4a). (c) 2010 Elsevier Ltd. All rights reserved.