Development of Magnetite Conjugated to Monoclonal Antibodies for Cancer Diagnosis and Therapy

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Recently, aggressive lymph node dissection in conjunction with resection of main tumor for visceral malignancy has been reported to result in substantial improvements in survival. However, normal organs or lymph nodes without cancer involvment are resected simultaneously with cancerous tissues. It is difficult to differenciate cancerous tissues from normal tissues with CT scan ot MRI.We have developed monoclonal antibody (Mab) A7 against human colon cancer. MAbA7 has been reported to react with 88% of human colonic carcinomas tested. Recently, we also developed human/mouse chimeric Fab fragments of MabA7 (ChA7Fab) using recombinant DNA techniques. In this study, ChA7Fab was labeled with ^<131>I and administered to nude mice bearing human colon cancer. Radioactivities in the small tumors were measured using portable gamma detecting probe (GDP) two days after injection. Radioactivities in the small tumors were able to detected by GDP.In contrast, radioactivity of normal tissue was not detected. If these ideas could be applied to the human with colon cancer, cancerous tissues could be easily differenciated from normal tissues intraoperatively, because GDP is small device and can be used intraoperatively. Furthermore, if magnetite are used insted of ^<131>I and the device which measure the accumulation of mignetite, we will not be exposed to radioactivity.