Abstract
We established LNCaP tumor in male nude mice after inoculation of LNCaP cells. The tumor produces the organ-specific glycoproteins in the human prostate, γ-seminoprotein (γ-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 γ-Sm than the SOLID portion does. The monoclonal antibody against γ-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 49.8-56.6KBq/μg were obtained. Biodistribution of 125I-labeled monoclonal antibody to γ-Sm (125I-γMAb) 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 32-38μg of 125I-γMAb to 12 nude mice bearing LNCaP tumor. The DLU were evaluated 3, 4 and 7 days after intravenous administrations of 18-25μ/g of 125I-γMAb 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)÷injected dose per gram of animal (dpm/g)×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-γMAb respectively.
These results suggest that the radio-labeled γMAb is applicable for immunoscintigraphy of adenocarcinoma of the prostate.
