Membrane vesicles from multidrug-resistant human cancer cells contain a specific 150- to 170-kDa protein detected by photoaffinity labeling.
Multiple drug resistance of tumor cells is a common problem in cancer therapy. We have demonstrated that membrane vesicles from highly multidrug-resistant human KB carcinoma cell lines exhibit increased specific and saturable binding of vinblastine. To identify the molecules that bind vinblastine, membrane vesicles from multidrug-resistant cells were exposed to two analogs of vinblastine, N-(p-azido-[3,5-3H]benzoyl)-N'-(beta-aminoethyl)vindesine and N-(p-azido-[3-125I]salicyl)-N'-(beta-aminoethyl)vindesine, that could be photoactivated. Our studies show the specific labeling of a 150- to 170-kDa protein in membrane vesicles from two independently selected multidrug-resistant KB cell lines, which was not seen in drug-sensitive parental or revertant cell lines. The labeling of the high molecular weight protein was inhibited in a dose-dependent manner by vinblastine with half-maximal inhibition at about 1 microM. Photolabeling was also inhibited by 100 microM vincristine or 100 microM verapamil but not by 100 microM colchicine or 100 microM dexamethasone. The data suggest that the 150- to 170-kDa protein may play an important role in the multidrug-resistance phenotype.
Cornwell
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MM
Safa
A R
AR
Felsted
R L
RL
Gottesman
M M
MM
Pastan
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I
D000345:Affinity Labels; D002460:Cell Line; D004351:Drug Resistance; D006801:Humans; D008565:Membrane Proteins / Q000378:metabolism*; D008970:Molecular Weight; D009363:Neoplasm Proteins / Q000378:metabolism*; D014747:Vinblastine / Q000031:analogs & derivatives / Q000378:metabolism
D000345:Affinity Labels; D008565:Membrane Proteins; D009363:Neoplasm Proteins; D014747:Vinblastine