Survival role of protein kinase C (PKC) in chronic lymphocytic leukemia and determination of isoform expression pattern and genes altered by PKC inhibition

Am J Hematol. 2005 Jun;79(2):97-106. doi: 10.1002/ajh.20352.


Recent studies have suggested that protein kinase C (PKC) activation plays an important role in survival of chronic lymphocytic leukemia (CLL). In order to characterize the role of PKC in CLL, we investigated the expression pattern of PKC isoforms in CLL cells (7 cases) and evaluated the effect of PKC inhibition on the survival of CLL cells (20 cases). Expression of the classical PKC isoforms beta and gamma, the novel isoform delta and the atypical isoform zeta was seen in all analyzed patient samples by Western blot analysis. Expression of the PKC isoforms alpha, epsilon, and iota was variable. Following incubation with the PKC inhibitor, safingol, CLL cells underwent marked apoptosis in all cases. In order to characterize the molecular events associated with the apoptotic effect of PKC inhibition, gene expression patterns in CLL cells were evaluated by cDNA-microarray analysis. Following safingol treatment, several genes showed marked downregulation and PKC-related proteins demonstrated decreased hybridization signals. Among these proteins, CREB and Daxx were further studied by using Western blotting, nuclear binding assay and confocal immunofluorescent microscopy. These studies showed significant inhibition of these proteins, consistent with the results of microarray gene analysis. Overall, these findings suggest that PKC activation is important for CLL cell survival and that inhibitors of PKC may have a role in the treatment of patients with CLL.

MeSH terms

  • Adaptor Proteins, Signal Transducing
  • Apoptosis / drug effects
  • Apoptosis / genetics
  • Blotting, Western
  • Carrier Proteins / genetics
  • Carrier Proteins / metabolism
  • Cell Survival / drug effects
  • Co-Repressor Proteins
  • Cyclic AMP Response Element-Binding Protein / genetics
  • Cyclic AMP Response Element-Binding Protein / metabolism
  • Down-Regulation / drug effects
  • Enzyme Inhibitors / pharmacology*
  • Humans
  • Intracellular Signaling Peptides and Proteins / genetics
  • Intracellular Signaling Peptides and Proteins / metabolism
  • Isoenzymes / genetics
  • Isoenzymes / metabolism
  • Leukemia, Lymphocytic, Chronic, B-Cell / enzymology
  • Leukemia, Lymphocytic, Chronic, B-Cell / physiopathology*
  • Molecular Chaperones
  • Nuclear Proteins / genetics
  • Nuclear Proteins / metabolism
  • Oligonucleotide Array Sequence Analysis
  • Protein Kinase C / antagonists & inhibitors
  • Protein Kinase C / genetics*
  • Protein Kinase C / metabolism*
  • Sphingosine / analogs & derivatives*
  • Sphingosine / pharmacology*


  • Adaptor Proteins, Signal Transducing
  • Carrier Proteins
  • Co-Repressor Proteins
  • Cyclic AMP Response Element-Binding Protein
  • DAXX protein, human
  • Enzyme Inhibitors
  • Intracellular Signaling Peptides and Proteins
  • Isoenzymes
  • Molecular Chaperones
  • Nuclear Proteins
  • Protein Kinase C
  • Sphingosine
  • safingol