Radioimmunoscintigraphy of xenografted human thyroid carcinoma.

We developed monoclonal antibodies against human thyroid cancer-associated antigen by fusing mouse myeloma cells with mouse spleen cells immunized by insoluble fraction of homogenized thyroid papillary carcinoma cells. One monoclonal antibody (KTC-3, IgM) was selected to evaluate basic usefulness for radioimmunoscintigraphy in xenografted human thyroid carcinoma. KTC-3 was labeled with 131I by Iodogen method of 20 to 1 Iodogen to IgM molar ratio. It was also labeled with 111In by cyclic DTPA anhydride method of 20 to 1 DTPA to IgM molar ratio. The labeling efficiency and specific activity for 131I labeling were 16.5% and 0.66 mCi/mg IgM respectively, and those for 111In labeling were 12.7% and 1.6 mCi/mg IgM. Imaging and biodistribution of labeled KTC-3 were evaluated in nude mice bearing thyroid anaplastic carcinoma (THC-5-JCK). The tumors were well visualized 3 and 5 days after injection of 131I KTC-3. Tumor uptake of 131I KTC-3 on day 7 was 0.52 +/- 0.27% ID/g and tumor to blood ratio was 1.98 +/- 0.76 (n = 6). Those of 111In KTC-3 were 0.88 +/- 0.09% ID/g and 5.51 +/- 3.36 (n = 6). In conclusion, KTC-3 is promising for radioimmunoscintigraphy of thyroid cancer.