Intracellular sequestration of anti-tumor drugs by metallothionein.
Acquired drug resistance is one of the most important problems in cancer chemotherapy. One of the mechanisms proposed to contribute to this phenomenon is the sequestration of alkylating agents by metallothionein (MT) in vivo. In this study cadmium-induced human bladder tumor T24 cells were exposed to the therapeutic agents chlorambucil and melphalan. MT-2a, was shown by capillary electrophoresis to comprise 56% of the MT isoforms in induced cells, and drug adducts of MT-2a were isolated and characterized by HPLC and electrospray ionization mass spectrometry. One to four equivalents of drug were found to be covalently adducted. Major binding sites on metallothionein were located in the C-terminal domain by peptide mapping, consistent with previous studies in vitro.
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Dept of Chemistry and Biochemistry, University of Maryland Baltimore County, 21250, USA.
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Fabris
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Fenselau
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D000478:Alkylation; D000818:Animals; D000970:Antineoplastic Agents / Q000378:metabolism*; D019256:Cadmium Chloride / Q000494:pharmacology; D002470:Cell Survival / Q000187:drug effects; D002851:Chromatography, High Pressure Liquid; D006801:Humans; D013058:Mass Spectrometry; D008668:Metallothionein / Q000378:metabolism*; D008745:Methylation; D020033:Protein Isoforms; D011817:Rabbits; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; D014357:Trypsin / Q000494:pharmacology; D014407:Tumor Cells, Cultured; D001749:Urinary Bladder Neoplasms / Q000188:drug therapy*
D000970:Antineoplastic Agents; D020033:Protein Isoforms; D008668:Metallothionein; D014357:Trypsin; D019256:Cadmium Chloride