Effect of radioiodination on the binding of monoclonal antibody DF3 to breast carcinoma cells

The murine monoclonal antibody (MAb) designated DF3 is an IgG1 prepared against a membrane enriched fraction of human breast carcinoma. MAb DF3 reacts with a family of large molecular weight glycoproteins expressed by 78% of breast cancer cells and 95% of epithelial ovarian cancer cells. Binding to the breast cancer cell line, MCF-7, of native MAb DF3 was compared to that of MAb DF3 exposed to different concentrations of Iodogen or Bolton-Hunter reagent. The amount of MAb DF3 required to obtain half-maximal binding (Bsub(1/2 max) with MCF-7 extract for native MAb DF3 IgG was 180 ng, while the Bsub(1/2 max) for MAb DF3 IgG exposed to 1 and 10 μg Iodogen was 580 ng and 1800 mg, respectively. In contrast, the Bsub(1/2 max) for MAb DF3 IgG treated with Bolton-Hunter reagent was not different from that for native MAb DF3 IgG. Similar results were obtained with F(ab')2. Immunoreactive fractions for the 125I-labeled MAb DF3 were 0.13, 0.24 and 0.65 for IgG after exposure to 1 μg Iodogen, 10 μg Iodogen and Bolton-Hunter, respectively. Immunoreactive fractions for F(ab')2 were 0.08, 0.08, and 0.53 for 1 and 10 μg Iodogen and Bolton-Hunter reagent, respectively. (author)