In vivo imaging and specific targeting of P-glycoprotein expression in multidrug resistant nude mice xenografts with [125I]MRK-16 monoclonal antibody Academic Article Article uri icon


MeSH Major

  • Antibodies, Monoclonal, Murine-Derived
  • Lymphoma, Follicular
  • Radioimmunotherapy
  • T-Lymphocyte Subsets
  • T-Lymphocytes


  • 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)

publication date

  • January 1995



  • Academic Article


Digital Object Identifier (DOI)

  • 10.1016/0969-8051(94)00127-6

PubMed ID

  • 7550027

Additional Document Info

start page

  • 497

end page

  • 504


  • 22


  • 4