Evaluation of an anti-carcinoembryonic monoclonal antibody suitable for immunoscintigraphy

Brazilian Journal of Medical and Biological Research

D.w. Moraes²  E.n.p. Lima¹  I.b. Prado²  C.r.w. Carneiro² 

[1] ,Instituto Ludwig de Pesquisa sobre o CâncerSão Paulo SP ,Brasil

关键词: monoclonal antibody;    carcinoembryonic antigen;    colorectal carcinoma;    immunoscintigraphy;    technetium-99m;   

DOI  :  10.1590/S0100-879X1999000800006

来源: SciELO

【 摘 要 】

An anti-carcinoembryonic antigen (CEA) monoclonal antibody (mAb 6D1.1) was evaluated in vitro and in vivo to determine its suitability as a tracer for immunoscintigraphy of colorectal carcinomas. Determination of mAb affinity for CEA showed a constant of association of 0.63 ± 0.11 x 109 M-1. Binding of technetium-99m (99mTc)-6D1.1, labeled by a direct method, to human cultured lineages was highly specific. Binding to only CEA-positive LS-174T cells resulted in a saturable curve inhibited by pre-incubation with unlabeled mAb. No binding at all was observed for the human lineages MeWo (melanoma) or ZR75-30 (breast carcinoma), neither of them expressing CEA cells. Intravenous injection of 99mTc-6D1.1 into nude mice xenografted with human LS-174T tumors resulted in planar images of excellent quality. Localization of an irrelevant mAb labeled with either 99mTc or iodine-125 was never observed in tumor masses. Biodistribution studies on excised tumoral tissue showed retention of 28.48% of the injected dose per gram of LS-174T tumor. The tumor-to-blood ratio was 3.46. The same analysis performed on the other three human xenografted tumors studied demonstrated that only the CEA-producing HT-29 (colorectal adenocarcinoma) retained 99mTc-6D1.1 while the other two (ZR75-30 and MeWo) did not. These data demonstrate that this mAb is an adequate tool for targeting CEA-expressing tumors in experimental models.

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