Radioimmunodetection of carcinoma of the stomach and colorectum by monoclonal antibodies

用抗肿瘤相关抗原的单抗进行放射免疫检测，有可能鉴别良、恶性组织。本实验室研制了抗胃癌单抗GC302和抗结直肠癌单抗CEA102。GC302识别的抗原大小为40K，是胃中的癌胚抗原，也是一种分化抗原，其定位区别于前肠道和中肠来源的胃肠道。CEA102与正常的胎儿结肠上皮和几乎所有的结直肠癌均呈阳性反应。其他癌症或正常组织，如黑色素瘤、白血病细胞和纤维组织均为阴性。因此，GC302和CEA102分别是检测胃癌和结直肠癌转移部位的良好工具。在异种移植的放射免疫核素显像成功后，我们将该方法应用于结直肠癌患者的转移部位检测。对6例患者进行了~(131)I标记CEA102的研究，其中2例核素显影显示抗体显著累积。此外，我们还比较了F(ab‘)_2和整个CEA102中抗体的排泄和对肿瘤的蓄积。结果表明，F(ab‘)2具有较好的抗体排泄和蓄积能力。因此，F(ab‘)_2允许我们使用^&lt；123；I和发射CT。

Radioimmunodetection using monoclonal antibody to tumor-associated antigen has the potential for the differential deagnosis between malignant and benign tissues. We produced the monoclonal antibodies, GC302 to gastric cancer, and CEA102 to colorectal cancer in our laboratory. The antigen recognized by GC302 is 40K and characterized as an oncofetal antigen in stomach,and also as a differentiation antigen whose localization discriminates between the gastrointestinal tracts of the forgut origin and midgut origin. CEA102 reacted with normal epitherium of fetal colon and almost all cancer of the colorectum. Other cancers or normal tissues such as melanoma, leukemic cells, and fibrous tissues were negative. Therefore GC302and CEA102 are good tool to detect metatatic sites of gastric and colorectal cancer, respectively.After radioimmunoscintigraphy using xenografts could be done successfully, we applied this method to detect metastatic sites of patients with colorectal cancer. Six patients were studied with ^<131>I labeled CEA102, and two showed significant accunulation of antibody by scintigraphy. Moreover, we investigate to compare the excretion of antibody, and its accumulation to tumor between F(ab')_2 and whole CEA102. The results showed F(ab')_2 is better in excretion and accumulation of antibody. Therefore F(ab')_2 allows us to use^<123>I and Emission CT.