title: Immunohistochemical detection and quantitation of P-glycoprotein in multiple drug-resistant human myeloma cells: association with level of drug resistance and drug accumulation.
abstract: Using several multiple drug-resistant human myeloma cell lines as standards, we developed an immunohistochemical staining technique and means of quantitating P-glycoprotein in individual myeloma cells. The level of staining intensity for P-glycoprotein in individual myeloma cells was quantitated by measuring the average optical density of each cell with a microscopic computerized cell analysis system. Using this system, we observed that the level of P-glycoprotein for individual cells within a cell population of known drug sensitivity was very homogeneous (coefficient of variation less than or equal to 13%). Analysis of cell lines with gradually increasing levels of multidrug resistance (8226/S, 8226/Dox6 and 8226/Dox40) demonstrated a close association between the level of resistance to doxorubicin, defined by the mean lethal dose (D0) and the amount of P-glycoprotein on individual cells determined by the optical density (r = 0.82, P less than 0.0005). Intracellular doxorubicin (DOX) accumulation in the individual cell lines was inversely related to the level of drug resistance expressed as D0. P-glycoprotein was also detected in the marrow-derived myeloma cells of patients with drug refractory disease using immunohistochemical staining. The amount of P-glycoprotein in the cells of one patient was directly compared to the amount found in the simultaneously stained standard cell lines (8226/Dox6 and 8226/Dox40) by comparing the optical densities for individual cells. Using this immunohistochemical technique to detect and quantitate P-glycoprotein in patient myeloma cells and comparing it to standard multidrug resistant myeloma cell lines may be of value in determining the contribution of P-glycoprotein to clinical drug resistance in patients with multiple myeloma.
authors.affiliation: Department of Medicine, Arizona Cancer Center, University of Arizona, Tucson 85724.
authors.forename: W S
authors.initials: WS
authors.lastname: Dalton
authors.forename: T M
authors.initials: TM
authors.lastname: Grogan
authors.forename: J A
authors.initials: JA
authors.lastname: Rybski
authors.forename: R J
authors.initials: RJ
authors.lastname: Scheper
authors.forename: L
authors.initials: L
authors.lastname: Richter
authors.forename: J
authors.initials: J
authors.lastname: Kailey
authors.forename: H J
authors.initials: HJ
authors.lastname: Broxterman
authors.forename: H M
authors.initials: HM
authors.lastname: Pinedo
authors.forename: S E
authors.initials: SE
authors.lastname: Salmon
mesh_terms: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D000911:Antibodies, Monoclonal; D015153:Blotting, Western; D004317:Doxorubicin / Q000378:metabolism / Q000494:pharmacology; D004351:Drug Resistance; D006801:Humans; D007124:Immunoenzyme Techniques; D008562:Membrane Glycoproteins / Q000032:analysis*; D014407:Tumor Cells, Cultured / Q000032:analysis
chemical_list: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D000911:Antibodies, Monoclonal; D008562:Membrane Glycoproteins; D004317:Doxorubicin