[Experimental studies for immunoscintigraphy of adenocarcinoma of the prostate with 125I-labeled monoclonal antibody to gamma-seminoprotein].

: We established LNCaP tumor in male nude mice after inoculation of LNCaP cells. The tumor produces the organ-specific glycoproteins in the human prostate, gamma-seminoprotein (gamma-Sm), which has been verified by immunohistochemistry and enzyme immuno assay. The LNCaP tumor is composed of 2 distinct portions, namely GEL/FLUID portion and SOLID portion. The GEL/FLUID portion contains much more gamma-Sm than the SOLID portion does. The monoclonal antibody against gamma-Sm (murine IgG1, K) was radio-labeled with iodine-125 by lactoperoxidase method followed by passage over column chromatography. Finally the conjugates with specific activity of 49.8-56.6 KBq/micrograms were obtained. Biodistribution of 125I-labeled monoclonal antibody to gamma-Sm (125I-gamma MAb) was evaluated by whole-body autoradiography (ARG) and by determination of label uptake (DLU) by the LNCaP tumor using the well type gamma counter. The ARG were obtained 1-9 days after intravenous administrations of 32-38 micrograms of 125I-gamma MAb to 12 nude mice bearing LNCaP tumor. The DLU were evaluated 3, 4 and 7 days after intravenous administrations of 18-25 micrograms of 125I-gamma MAb to 9 nude mice bearing LNCaP tumor. The DLU by organs (GEL/FLUID portion, SOLID portion, liver, kidney, spleen, lung, etc.) were expressed as F-values (%) which were calculated by the following formula: F = radioactivity per gram of tissue (dpm/g) divided by injected dose per gram of animal (dpm/g) x 100 and tissue-to-blood ratios (T/B). The specific uptake by the LNCaP tumors, especially in the GEL/FLUID portion, was observed on ARG, with optimal images of the tumor evaluated 4-7 days after administrations. The F-values and T/B of the LNCaP tumors were always higher than those of other organs. Especially T/B of GEL/FLUID portion were of 6.7 and 6.3, evaluated 4 and 7 days after administration of 125I-gamma MAb respectively. These results suggest that the radio-labeled gamma MAb is applicable for immunoscintigraphy of adenocarcinoma of the prostate.