To obtain murine monoclonal antibodies (MAb), mice were immunized with the extract of a human fetal lung from the first trimester of gestation as initial immunogen followed by booster immunization with a human lung cancer cell line. MAb CF703 which reacted to the booster material was screened and selected. In adults, expression of the antigen defined by MAb CF703, CF703 antigen, was shown immunohistochemically in 78% of gastric carcinomas (14/18), 59% of ovarian adenocarcinomas (10/17), 50% of pancreatic carcinomas (5/10), 17% of lung carcinomas (4/24), 50% of uterine cervical adenocarcinomas (2/4), 20% of endometrial adenocarcinomas (1/5) and 10% of renal cell carcinomas (1/10). Other malignant tumors failed to demonstrate the reactivity. MAb CF703 was weakly reactive with only three adult normal tissues including surface lining of gastric mucosa, Brunner's glandular epithelia of the duodenum and columnar epithelia in the uterine endocervix. In fetal tissues, 5 of 23 tissues including squamous epithelia in lower portion of the;esophagus, surface epithelia of gastric mucosae and goblet cells in the small and large intestine were reactive. The CF703 antigen had a molecular weight over 500 kDa and its epitope was carbohydrate in nature by reason of the resistance to proteinase digestion and sensitivity to periodate oxidation, neuraminidase and alkaline-borohydrite. MAb CF703 recognizes probably a unique epitope in oncodevelopmental mucin glycoprotein. Additionally, this immunization method has the advantage of rapid acquirement of MAbs with restricted, narrow cancer spectrum and is a worthy strategy for generating the new MAbs.

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