Effect of alpha-interferon on P-glycoprotein expression and function and on verapamil modulation of doxorubicin resistance.
Human alpha-interferon (IFN-alpha) is one of the three major classes of interferons which possess antiviral, antiproliferative, and immunomodulatory activities. We recently reported synergism between IFN-alpha and tamoxifen in the modulation of doxorubicin (DOX) cytotoxicity and accumulation in multidrug resistant Chinese hamster ovary ChR C5 cells (Y. Kang and R. R. Perry, Cancer Res., 53: 3040-3045, 1993), but the mechanism was uncertain. In the present study, IFN-alpha (500 units/ml) pretreatment of ChR C5 cells similarly increased verapamil (VPL) modulation of DOX cytotoxicity in a time-dependent manner. Measurement of intracellular DOX fluorescence showed a parallel increase in DOX accumulation. Western blot analysis revealed that IFN-alpha induced a time-dependent increase in p-glycoprotein (p-gp) expression, accompanied by an increase of mdr-1 mRNA as measured using Northern analysis. MDR-1 gene copy number measured using Southern analysis remained unchanged. Assay of specific photoaffinity labeling of p-gp by [3H]-azidopine showed that, although IFN-alpha is not a substrate of p-gp, it significantly increased the ability of VPL to bind to p-gp. These data suggest that IFN-alpha may effect the expression of p-gp in multidrug-resistant ChR C5 cells by transcriptional or posttranscriptional control of mdr-1 gene expression. IFN-alpha enhances the ability of VPL to modulate DOX cytotoxicity and accumulation, possibly by altering the accessibility of p-gp binding site(s) to VPL. By using relatively low concentrations of IFN-alpha and VPL it may be possible to develop less toxic regimens to reverse multidrug resistance.
Kang
Y
Y
Division of Surgical Oncology, Eastern Virginia Medical School, Norfolk 23507.
Perry
R R
RR
D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D000345:Affinity Labels; D000818:Animals; D001386:Azides / Q000378:metabolism; D001667:Binding, Competitive; D002352:Carrier Proteins / Q000378:metabolism / Q000502:physiology*; D002460:Cell Line; D006224:Cricetinae; D004095:Dihydropyridines / Q000378:metabolism; D004317:Doxorubicin / Q000378:metabolism*; D004351:Drug Resistance / Q000235:genetics; D004357:Drug Synergism; D016898:Interferon-alpha / Q000494:pharmacology*; D008562:Membrane Glycoproteins / Q000378:metabolism / Q000502:physiology*; D012333:RNA, Messenger / Q000378:metabolism; D014700:Verapamil / Q000494:pharmacology*
D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D000345:Affinity Labels; D001386:Azides; D002352:Carrier Proteins; D004095:Dihydropyridines; D016898:Interferon-alpha; D008562:Membrane Glycoproteins; D012333:RNA, Messenger; C041130:azidopine; D004317:Doxorubicin; D014700:Verapamil