An experimental immunoscintigraphic study with anti-CEA monoclonal antibody (DG2)

Monoclonal antibody D11-DG2 (DG2) against carcinoembryonic antigen (CEA) was examined for suitability in radioimmunodetection of human tumors grown in nude mice. Antibodies DG2 and a control antibody of the same IgG1 subclass were labelled with 131I and injected into mice bearing one of three types of CEA-containing tumors (cell lines LS 174T, HT-29 and Rec S) and/or a CEA-negative tumor (Rec R). Gamma camera imaging and distribution studies revealed that CEA-containing tumors selectively accumulated DG2 but Rec R did not. As the tumors differ in the CEA content, the highest accumulation of 131I-DG2 (corresponding to the best scintigraphic imaging) was found in LS 174T tumors, medium in Rec S and the lowest in HT-29 tumors. The mean tumor-to-blood ratios on the sixth day after antibody administration were 4.6, 3.2, and 2.1, respectively; in the control experiments the value of this parameter was always lower than 1. The results showed the applicability of DG2 in immunoscintigraphic studies in patients. A positive correlation was found between the uptake of anti-CEA antibody and the CEA content in the tumors. (author). 4 figs., 1 tab., 24 refs