The drug resistance proteins, multidrug resistance-associated protein and P-glycoprotein, do not confer resistance to Fas-induced cell death.
BACKGROUND
Multidrug resistance (MDR) is mediated by the drug resistance proteins, the multidrug resistance-associated protein (MRP) and P-glycoprotein, both of which confer resistance by the active efflux of chemotherapeutic drugs from the cell. Reduced Fas (CD95/APO-1) expression and resistance to Fas-mediated apoptosis have also been correlated with P-glycoprotein-mediated MDR.


METHODS
We investigated cell surface Fas expression (using anti-Fas monoclonal antibody DX2.1) in a series of MRP-expressing drug-resistant leukemia sublines, and P-glycoprotein-expressing leukemia sublines, and their susceptibility to apoptosis induced by anti-Fas treatment (CH-11 monoclonal antibody). Caspase-3 activation was detected by Western blot and apoptosis was determined by flow cytometry with 7-aminoactinomycin D (7-AAD) staining of cells.


RESULTS
Fas expression was not reduced in either the MRP- or P-glycoprotein-expressing drug-resistant cell lines, although expression was reduced by 15% in one low-level drug-resistant subline. Expression of MRP or P-glycoprotein did not confer resistance to caspase-3 activation or to anti-Fas-induced cell death.


CONCLUSIONS
MDR mediated by the drug transport proteins MRP and P-glycoprotein does not correlate with resistance to Fas-mediated cell death or resistance to caspase-3 activation.
Cullen
K
K
Cell and Molecular Biology Department, University of Technology, Sydney, Australia.
Davey
R
R
Davey
M
M
D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000235:genetics / Q000378:metabolism*; D018528:ATP-Binding Cassette Transporters / Q000235:genetics / Q000378:metabolism*; D000911:Antibodies, Monoclonal / Q000494:pharmacology; D017209:Apoptosis / Q000502:physiology*; D053148:Caspase 3; D020169:Caspases / Q000378:metabolism; D016923:Cell Death / Q000502:physiology; D003609:Dactinomycin / Q000031:analogs & derivatives; D018432:Drug Resistance, Multiple; D004789:Enzyme Activation; D005434:Flow Cytometry; D005456:Fluorescent Dyes; D006801:Humans; D020014:K562 Cells; D027425:ATP-Binding Cassette, Sub-Family C Proteins; D014407:Tumor Cells, Cultured; D014747:Vinblastine / Q000633:toxicity; D019014:fas Receptor / Q000235:genetics / Q000502:physiology*
D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D018528:ATP-Binding Cassette Transporters; D000911:Antibodies, Monoclonal; D053148:Caspase 3; D020169:Caspases; D003609:Dactinomycin; D005456:Fluorescent Dyes; D027425:ATP-Binding Cassette, Sub-Family C Proteins; D014747:Vinblastine; D019014:fas Receptor; C025942:7-aminoactinomycin D; C505407:CASP3 protein, human