title: Overexpression of a 40-kDa protein in human multidrug resistant cells.
abstract: The use of anticancer drugs in the chemotherapeutic treatment of cancer patients frequently results in the emergence of drug resistant tumors. Selection of tumor cell lines in vitro has led to the identification of several proteins that mediate drug resistance to anticancer drugs. In this study, an immuno-dot blot method was used to isolate a monoclonal antibody (IPM96) which recognized a 40 kDa protein (or P-40) co-expressed with P-glycoprotein and MRP in several multidrug resistant cell lines (MCF-7/Adr, SKOV/VLB1.0, H69/Adr, and HL60/AR). Furthermore, P-40 levels dropped significantly in one revertant cell line (H69/PR) derived from H69/AR cells. Interestingly, the expression of P-40 was also higher in two tumor cell lines (SKTax6a and A2780CP) that were selected with paclitaxel or cisplatin but do not express P-gp or MRP. Immuno-fluorescence staining of cells with IPM96 showed both membrane and cytoplasmic staining. These results were confirmed by Western blot analysis of different subcellular fractions from MCF-7/Adr cells. The membrane bound P-40 was resistant to extraction with high salt, chelating agents, and denaturing agents, but was solubilized with 10 mM CHAPS. Taken together, the overexpression of P-40 in multidrug resistant cells has not been previously determined and therefore could be important in the expression of the drug resistance phenotype.
authors.affiliation: Institute of Parasitology, McGill University, Macdonald Campus, Ste-Anne de Bellevue, Quebec, Canada.
authors.forename: Y
authors.initials: Y
authors.lastname: Wang
authors.forename: X Q
authors.initials: XQ
authors.lastname: Pan
authors.forename: F
authors.initials: F
authors.lastname: Lheureux
authors.forename: E
authors.initials: E
authors.lastname: Georges
mesh_terms: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000378:metabolism; D018528:ATP-Binding Cassette Transporters / Q000378:metabolism; D000911:Antibodies, Monoclonal / Q000276:immunology*; D015153:Blotting, Western; D002451:Cell Compartmentation; D002462:Cell Membrane / Q000378:metabolism; D002478:Cells, Cultured; D018432:Drug Resistance, Multiple; D006801:Humans; D008565:Membrane Proteins / Q000276:immunology* / Q000378:metabolism; D008970:Molecular Weight; D027425:ATP-Binding Cassette, Sub-Family C Proteins
chemical_list: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D018528:ATP-Binding Cassette Transporters; D000911:Antibodies, Monoclonal; D008565:Membrane Proteins; D027425:ATP-Binding Cassette, Sub-Family C Proteins