[Show abstract][Hide abstract] ABSTRACT: Radioimmunoguided surgery (RIGS) appears as an efficient tool for accurate tumor detection up to the level of micrometastases by detecting radiolabeled antibody-bound tumor cells during operation. Anti-CEA-specific T84.66 fragments were examined as to whether they efficiently detected gastric cancer cells in experimental RIGS. T84.66, anti-CEA-specific antibody, has widely been used as an immune carrier in the preclinical and clinical trials of radioimmunotherapy and radioimmunoscintiscan.
Fifty-one tumors from two human gastric carcinoma cell lines with profuse (MKN45) and low (RF48) CEA expression were successfully implanted subcutaneously in the backs of 32 nude mice. Tumors were localized after 125I-labeled T84.66 F(ab')2 and Fab' injection.
The radioactivity of F(ab')2-pretreated mice was greater than that of Fab'-pretreated in all organs and tumors (p<0.001-0.035). Localization indices of the tumor in various organs revealed 7.4 to 32.5 in F(ab')2-pretreated and 1 to 7.1 in Fab'-pretreated mice. Silver grains and immune staining were predominantly distributed in tumor cells regardless of fragment types and cell lines. There was no false-negative evaluation of tumor in F(ab')2-pretreated mice. Sensitivity and specificity of tumor localization by RIGS were the highest in the F(ab')2-pretreated mice (95% for MKN45- and 82% for RF46-xenografted mice) and the least in the Fab'-pretreated mice (66% for MKN45- and 67% for RF46-xenografted mice). In all organs, three quarters of the false-positive evaluations occurred from silver grains as radioimmune complex or dissociated nuclides in the circulation that can be eliminated with time.
Anti-CEA-specific T84.66 fragments achieved a great affinity and avidity with accurate localization of gastric carcinoma in experimental RIGS.
Full-text · Article · Mar 2004 · Anticancer research
[Show abstract][Hide abstract] ABSTRACT: Biparatopic CEA, carcinoembryonic antigen (MAb) was newly designed and tested as to whether it enhanced the accuracy of tumor detection by reducing non-specific binding in experimental radioimmunoguided surgery. Biparatopic MAb was prepared by using cross-linking of reduced Fab' fragments from PR1A3 and T84.66. Fifty-nine tumors from 2 human colorectal carcinoma cell lines with high (KM-12c) and low (Clone A) carcinoembryonic antigen (CEA) expression were successfully implanted subcutaneously on the backs of 42 nude mice. Tumors were localized using 125I-labeled MAbs: IgG, F(ab')(2) and Fab' of PR1A3, and biparatopic MAb of PR1A3 and T84.66. Radioactivity counted on a portable radioisotope detector correlated well with that counted on a gamma counter (p < 0.001). Accumulations of radioactivity in control mice without tumorigenesis were the greatest in PR1A3 IgG-pretreated mice and the least in biparatopic MAb-pretreated mice. Tumors of 2 cell lines did not differ in the distribution of radiolabeled MAbs. Localization indices of the tumor in various organs revealed 1.3 to 4.1 in PR1A3 IgG-pretreated mice, 2.4 to 6.6 in fragment MAbs of PR1A3-pretreated mice and 2 to 4.6 in biparatopic MAb-pretreated mice. Silver grains and immune staining were predominantly distributed in tumor cells of all types of MAb-pretreated mice. Sensitivity and specificity of tumor localization by radioimmunoguided surgery (RIGS) were the highest in the biparatopic MAb-pretreated mice (90.9% and 94.5%, respectively) and the least in the PR1A3 IgG-pretreated mice (50% and 72%). The biparatopic MAb using 2 anti-CEA MAbs against different epitopes achieved a great affinity and avidity with accurate localization of colorectal carcinoma in experimental radioimmunoguided surgery.
Full-text · Article · Feb 2002 · International Journal of Cancer