Defective translocation of protein kinase C in multidrug-resistant HL-60 cells confers a reversible loss of phorbol ester-induced monocytic differentiation.
Previous studies have demonstrated that human HL-60 myeloid leukemia cells differentiate in response to phorbol esters. This event is associated with induction of the c-jun early response gene and appearance of a monocytic phenotype. The present studies have examined the effects of vincristine-selected, multidrug resistance on 12-O-tetradecanoylphorbol-13-acetate (TPA)-induced HL-60 cell differentiation. The results demonstrate that multidrug-resistant HL-60 cells, designated HL-60/vinc, fail to respond to TPA with an increase in c-jun transcripts or other phenotypic characteristics of monocytic differentiation. By contrast, treatment of HL-60/vinc cells with okadaic acid, an inhibitor of serine/threonine protein phosphatases, induces c-jun transcription, growth arrest, and expression of the c-fms gene. Studies were also performed with an HL-60/vinc revertant (HL-60/vinc/R) line that has regained partial sensitivity to vincristine. The finding that HL-60/vinc/R cells respond to TPA with induction of a monocytic phenotype, but not c-jun expression, suggests that c-jun induction is not obligatory for monocytic differentiation. Other studies further demonstrate that the jun-B and fra-1 genes are induced by TPA in both HL-60/vinc and HL-60/vinc/R cells, whereas c-fos expression is attenuated in the HL-60/vinc line. Since TPA activates protein kinase C (PKC), we examined translocation of PKC from the cytosol to the membrane fraction. Although HL-60 and HL-60/vinc/R cells demonstrated translocation of PKC activity, this subcellular redistribution was undetectable in HL-60/vinc cells. Activity of the mitogen-activated protein kinase family with associated phosphorylation of c-Jun Y-peptide was markedly diminished in TPA-treated HL-60/vinc cells, but not in response to okadaic acid. Taken together, these findings suggest that vincristine resistance confers insensitivity to TPA-induced differentiation and can include defects in PKC-mediated signaling events and induction of jun/fos early response gene expression.
Laboratory of Clinical Pharmacology, Dana-Farber Cancer Institute, Harvard Medical School, Boston, Massachusetts 02115.
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Slapak
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Kharbanda
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Saleem
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Kufe
D017871:Calcium-Calmodulin-Dependent Protein Kinases; D002448:Cell Adhesion; D002454:Cell Differentiation / Q000187:drug effects; D002467:Cell Nucleus / Q000378:metabolism; D004351:Drug Resistance; D004988:Ethers, Cyclic / Q000494:pharmacology; D015870:Gene Expression / Q000187:drug effects; D006801:Humans; D007700:Kinetics; D015473:Leukemia, Promyelocytic, Acute; D009000:Monocytes / Q000166:cytology*; D019319:Okadaic Acid; D010749:Phosphoprotein Phosphatases / Q000037:antagonists & inhibitors; D011493:Protein Kinase C / Q000378:metabolism*; D011494:Protein Kinases / Q000378:metabolism*; D011518:Proto-Oncogene Proteins / Q000096:biosynthesis*; D016760:Proto-Oncogene Proteins c-fos / Q000096:biosynthesis; D016755:Proto-Oncogene Proteins c-jun / Q000096:biosynthesis; D011519:Proto-Oncogenes; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology*; D014407:Tumor Cells, Cultured; D014750:Vincristine / Q000494:pharmacology*
D004988:Ethers, Cyclic; D011518:Proto-Oncogene Proteins; D016760:Proto-Oncogene Proteins c-fos; D016755:Proto-Oncogene Proteins c-jun; D019319:Okadaic Acid; D014750:Vincristine; D011494:Protein Kinases; D011493:Protein Kinase C; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D010749:Phosphoprotein Phosphatases; D013755:Tetradecanoylphorbol Acetate