Submitted May 1, 2009
Accepted August 13, 2009
BMS-214662 induces mitochondrial apoptosis in CML stem/progenitor cells, including CD34+38- cells, through activation of protein kinase C
Francesca Pellicano, Mhairi Copland, Heather G. Jorgensen, Joanne Mountford, Brian Leber, and Tessa L. Holyoake*
Paul O'Gorman Leukaemia Research Centre, Medical Faculty, University of Glasgow, Glasgow, United Kingdom
McMaster University, Hamilton, Ontario, Canada
* Corresponding author; email: tlh1g{at}clinmed.gla.ac.uk.
Chronic myeloid leukaemia (CML) is a haemopoietic stem cell disorder maintained by cancer stem cells. To target this population, we investigated the mechanism of action of BMS-214662, developed as a farnesyl transferase inhibitor (FTI) and unique in inducing apoptosis in these cells. By contrast, a related congener and equally effective FTI, BMS-225975, does not induce apoptosis, indicating a novel mechanism of action. BMS-214662 significantly and selectively induced apoptosis in primitive CD34+38- CML compared to normal cells. Apoptosis proceeded via the intrinsic pathway: Bax conformational changes, loss of mitochondrial membrane potential, generation of reactive oxygen species, release of Cytochrome c and Caspase-9/3 activation were noted. Up-regulation of protein kinase C
(PKC), down-regulation of E2F1 and phosphorylation of Cyclin A-associated Cyclin-dependent kinase 2 preceded these changes. Co-treatment of CML CD34+ and CD34+38- cells with PKC modulators, bryostatin-1 or hispidin, markedly decreased these early events and the subsequent apoptosis. None of these events were elicited by BMS-214662 in normal CD34+ cells or by BMS-225975 in CML CD34+ cells. These data suggest that BMS-214662 selectively elicits a latent apoptotic pathway in CML stem cells that is initiated by up-regulation of PKC and mediated by Bax activation, providing a molecular framework for development of novel therapeutics.
