title: In vivo imaging and specific targeting of P-glycoprotein expression in multidrug resistant nude mice xenografts with [125I]MRK-16 monoclonal antibody.
abstract: Multidrug resistance (MDR) in tumors is associated with P-glycoprotein (Pgp) expression. In vivo quantitation of Pgp may allow MDR to be evaluated noninvasively prior to treatment planning. The purpose of this study was to radiolabel MRK-16, a monoclonal antibody that targets an external epitope of P-glycoprotein, and perform in vivo quantitation of P-glycoprotein in a MDR xenograft nude mouse model. MRK-16 was labeled with 125I by the iodogen method, with subsequent purification by size exclusion chromatography. Groups of 10 Balb c mice were each xenografted with colchicine-resistant or sensitive neuroblastoma cell lines, respectively. Whole body clearance and tumor uptake over time was quantitated by gamma camera imaging, and biodistribution studies were performed with [125I]MRK-16 and an isotype matched control antibody, A33. Quantitative autoradiography and immunohistochemistry analysis of tumors was also evaluated to confirm specific targetting of [125I]MRK-16. Peak tumor uptake was at 2-3 days post-injection, and was significantly greater in resistance compared to sensitive tumors (mean % injected dose/g +/- SD) (18.76 +/- 2.94 vs 10.93 +/- 0.96; p < 0.05). Quantitative autoradiography verified these findings (19.13 +/- 0.622 vs 12.08 +/- 0.38, p < 0.05). Specific binding of [125I]MRK-16 was confirmed by comparison to [131I]A33 in biodistribution studies, and localized to cellular components of tissue stroma by comparison of histologic and autoradiographic sections of sensitive and resistant tumors. Immunoblot analysis demonstrated a 4.5-fold difference in P-glycoprotein expression between sensitive and resistant cell lines without colchicine selective pressure. We conclude that in vivo quantitation of P-glycoprotein in MDR tumors can be performed with [125I]MRK-16.(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: Memorial Sloan-Kettering Cancer Center, New York, NY 10021, USA.
authors.forename: A M
authors.initials: AM
authors.lastname: Scott
authors.forename: E
authors.initials: E
authors.lastname: Rosa
authors.forename: B M
authors.initials: BM
authors.lastname: Mehta
authors.forename: C R
authors.initials: CR
authors.lastname: Divgi
authors.forename: R D
authors.initials: RD
authors.lastname: Finn
authors.forename: J L
authors.initials: JL
authors.lastname: Biedler
authors.forename: T
authors.initials: T
authors.lastname: Tsuruo
authors.forename: H
authors.initials: H
authors.lastname: Kalaigian
authors.forename: S M
authors.initials: SM
authors.lastname: Larson
mesh_terms: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000032:analysis* / Q000096:biosynthesis*; D000818:Animals; D000911:Antibodies, Monoclonal / Q000493:pharmacokinetics*; D001345:Autoradiography / Q000379:methods; D003078:Colchicine / Q000633:toxicity; D003609:Dactinomycin / Q000633:toxicity; D004317:Doxorubicin / Q000633:toxicity; D018432:Drug Resistance, Multiple; D005260:Female; D015870:Gene Expression; D006801:Humans; D007457:Iodine Radioisotopes; D051379:Mice; D008807:Mice, Inbred BALB C; D008819:Mice, Nude; D009447:Neuroblastoma / Q000000981:diagnostic imaging* / Q000473:pathology; D011877:Radionuclide Imaging; D014018:Tissue Distribution; D014183:Transplantation, Heterologous
chemical_list: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D000911:Antibodies, Monoclonal; D007457:Iodine Radioisotopes; D003609:Dactinomycin; D004317:Doxorubicin; D003078:Colchicine