title: Monoclonal antibody to an external epitope of the human mdr1 P-glycoprotein.
abstract: A membrane glycoprotein, termed P-glycoprotein, has been shown to be responsible for cross-resistance to a broad range of structurally and functionally distinct cytotoxic agents. P-glycoprotein, encoded in humans by the mdr1 gene, functions as an energy-dependent efflux pump to exclude these cytotoxic agents from the resistant cell. In order to study the phenomenon of multidrug resistance in both normal and neoplastic cells, we have generated a mouse monoclonal antibody directed to an external epitope of the human P-glycoprotein. This monoclonal antibody, 4E3, is an IgG2a class antibody which specifically recognizes the human mdr1 P-glycoprotein but not the mdr3 gene product. The 4E3 monoclonal antibody immunoprecipitates both the glycosylated and nonglycosylated forms of P-glycoprotein under mild denaturation conditions. In addition, 4E3 can detect P-glycoprotein in immunocytochemical analysis of fixed tissue-cultured cells and in analysis of frozen sections of human tissue. Binding of the monoclonal antibody to multidrug-resistant cells does not significantly affect the intracellular accumulation or potentiate the cytotoxicity of daunomycin in multidrug-resistant cells. However, at high concentrations of antibody, 4E3 produces a mild potentiation of vinblastine and actinomycin cytotoxicity in multidrug-resistant cells. This monoclonal antibody will be useful both for analyzing P-glycoprotein expression in normal and neoplastic cells and for isolating live cells expressing the P-glycoprotein without significantly affecting the efflux functions of the transporter.
authors.affiliation: Dana-Farber Cancer Institute, Boston, Massachusetts 02115.
authors.forename: R J
authors.initials: RJ
authors.lastname: Arceci
authors.forename: K
authors.initials: K
authors.lastname: Stieglitz
authors.forename: J
authors.initials: J
authors.lastname: Bras
authors.forename: A
authors.initials: A
authors.lastname: Schinkel
authors.forename: F
authors.initials: F
authors.lastname: Baas
authors.forename: J
authors.initials: J
authors.lastname: Croop
mesh_terms: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D000911:Antibodies, Monoclonal / Q000276:immunology; D002455:Cell Division; D002469:Cell Separation; D004351:Drug Resistance; D000939:Epitopes; D005434:Flow Cytometry; D006031:Glycosylation; D006801:Humans; D008562:Membrane Glycoproteins / Q000737:chemistry / Q000276:immunology* / Q000648:ultrastructure; D011233:Precipitin Tests
chemical_list: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D000911:Antibodies, Monoclonal; D000939:Epitopes; D008562:Membrane Glycoproteins