Radioimmunodetection of carcinoma of the stomach and colorectum by monoclonal antibodies

使用肿瘤相关抗原单克隆抗体的放射免疫检测具有鉴别诊断恶性和良性组织的潜力。我们在实验室生产了胃癌单克隆抗体GC302和结直肠癌单克隆抗体CEA102。GC302识别的抗原为40K，是胃内的癌胎抗原，也是一种分化抗原，其定位区分了中肠和外肠起源的胃肠道。CEA102能与正常的胎儿结肠上皮及几乎所有结直肠癌发生反应。其他癌症或正常组织如黑色素瘤、白血病细胞和纤维组织呈阴性。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。在使用异种移植物的放射免疫显像技术可以成功完成后，我们应用这种方法检测结直肠癌患者的转移部位。6例患者用^<131>I标记CEA102，其中2例经显像显示抗体明显积聚。此外，我们还比较了F（ab’）_2和全CEA102在肿瘤中的抗体分泌和积累情况。结果表明，F(ab')_2具有较好的排泄和抗体积累作用。因此F(ab')_2允许我们使用^<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.