Reversal of resistance to adriamycin by 8-chloro-cyclic AMP in adriamycin-resistant HL-60 leukemia cells is associated with reduction of type I cyclic AMP-dependent protein kinase and cyclic AMP response element-binding protein DNA-binding activities.
8-Chloro-cyclic AMP (8-Cl-cAMP) produces growth-inhibitory and differentiating activity in the promyelocytic leukemia cell line HL-60. Adriamycin (ADR)-resistant HL-60 (HL-60/AR) cells exhibit the multidrug-resistant phenotype but do not express the mdr1 gene product P-glycoprotein. To explore potential signaling processes that may be involved in this atypical form of drug resistance, 8-Cl-cAMP was used as a modulator of the cAMP second messenger signal transduction pathway. Treatment for 48 hr with a 10% inhibitory concentration of 8-Cl-cAMP potentiated ADR cytotoxicity 14-fold in HL-60/AR cells but not in the parental cell line. 8-Cl-cAMP was stable to hydrolysis in the medium after 48 hr and was present intracellularly predominantly as phosphorylated metabolites (70%) and the parent compound (30%). No difference occurred in ADR accumulation in HL-60/AR cells after treatment with 8-Cl-cAMP. Accompanying the 8-Cl-cAMP-mediated increase in ADR cytotoxicity in HL-60/AR cells was a reduction in the cytosolic type I cAMP-dependent protein kinase (PKA) and disappearance of the nuclear PKA holoenzyme. Coincident with these changes in drug-resistant cells was a marked reduction in the DNA-binding activity of the cAMP response element-binding protein to levels equivalent to those in sensitive cells. This effect appears to result from reduced phosphorylation of the cAMP response element-binding protein. These results suggest that the potentiation by 8-Cl-cAMP of ADR cytotoxicity in HL-60/AR cells occurs through down-regulation of nuclear type I PKA and cAMP response element-binding factors whose activities are regulated by PKA.
Department of Pharmacology, Georgetown University Medical Center, Washington, D.C. 20007.
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C
Rohlff
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Safa
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Rahman
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Cho-Chung
R W
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Klecker
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Glazer
D015124:8-Bromo Cyclic Adenosine Monophosphate / Q000031:analogs & derivatives* / Q000494:pharmacology; D002454:Cell Differentiation / Q000187:drug effects; D002851:Chromatography, High Pressure Liquid; D000242:Cyclic AMP / Q000378:metabolism; D017362:Cyclic AMP Response Element-Binding Protein / Q000378:metabolism*; D004273:DNA, Neoplasm / Q000378:metabolism; D015536:Down-Regulation; D004317:Doxorubicin / Q000494:pharmacology*; D004351:Drug Resistance; D004591:Electrophoresis, Polyacrylamide Gel; D006801:Humans; D015473:Leukemia, Promyelocytic, Acute / Q000378:metabolism; D011494:Protein Kinases / Q000378:metabolism*; D012045:Regulatory Sequences, Nucleic Acid; D015398:Signal Transduction / Q000187:drug effects*; D014407:Tumor Cells, Cultured
D017362:Cyclic AMP Response Element-Binding Protein; D004273:DNA, Neoplasm; D015124:8-Bromo Cyclic Adenosine Monophosphate; D004317:Doxorubicin; C044258:8-chloro-cyclic adenosine monophosphate; D000242:Cyclic AMP; D011494:Protein Kinases