Potentiation of 1-beta-D-arabinofuranosylcytosine-mediated mitochondrial damage and apoptosis in human leukemia cells (U937) overexpressing bcl-2 by the kinase inhibitor 7-hydroxystaurosporine (UCN-01)

Biochem Pharmacol. 2000 Nov 15;60(10):1445-56. doi: 10.1016/s0006-2952(00)00463-9.


Antileukemic interactions between the nucleoside analog 1-beta-D-arabinofuranosylcytosine (ara-C) and the kinase inhibitor 7-hydroxystaurosporine (UCN-01) have been examined in relation to Bcl-2 expression/phosphorylation, mitochondrial damage, caspase activation, and loss of clonogenic potential. Subsequent exposure of ara-C-pretreated U937 cells (1 microM; 6 hr) to UCN-01 (300 nM; 24 hr) resulted in marked potentiation of pro-caspase-3 and -9 cleavage/activation, poly(ADP-ribose)polymerase degradation, diminished mitochondrial membrane potential (Deltapsi(m)), enhanced cytochrome c release, reduction in the S-phase fraction, and induction of classic apoptotic morphologic features. Enforced expression of full-length Bcl-2 significantly protected cells (at 24 hr) from ara-C/UCN-01-induced caspase activation and apoptosis, but was ineffective in preventing loss of Deltapsi(m) and cytochrome c release. Ectopic expression of a Bcl-2 N-terminal phosphorylation loop-deleted protein (Bcl-2Delta(32-80)) was more potent than its full-length counterpart in blocking drug-induced loss of Deltapsi(m, ) caspase activation, and apoptotic morphology, but not cytochrome c release. Examination of cells at later intervals revealed that ectopic expression of Bcl-2 or Bcl-2Delta(32-80) could only delay, but not prevent, mitochondrial damage, caspase activation, and cell death induced by ara-C/UCN-01 treatment. Despite their initial ability to inhibit apoptosis, neither full-length nor truncated Bcl-2 protein restored clonogenic potential to drug-treated cells. These findings indicate that subsequent exposure of ara-C-pretreated human leukemia cells to UCN-01 potently triggers mitochondrial damage and apoptosis, and that these events are postponed but not prevented by ectopic expression of Bcl-2 or its phosphorylation loop-deleted counterpart.

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Alkaloids / pharmacology*
  • Antineoplastic Agents / pharmacology*
  • Apoptosis*
  • Cytarabine / pharmacology*
  • Drug Synergism
  • Enzyme Inhibitors / pharmacology
  • Humans
  • Leukemia / drug therapy*
  • Leukemia / metabolism
  • Leukemia / pathology
  • Mitochondria / drug effects*
  • Protein Kinase C / antagonists & inhibitors
  • Proto-Oncogene Proteins c-bcl-2 / metabolism*
  • Proto-Oncogene Proteins c-bcl-2 / physiology
  • Staurosporine / analogs & derivatives
  • U937 Cells


  • Alkaloids
  • Antineoplastic Agents
  • Enzyme Inhibitors
  • Proto-Oncogene Proteins c-bcl-2
  • Cytarabine
  • 7-hydroxystaurosporine
  • Protein Kinase C
  • Staurosporine