Differential expression of carcinoembryonic antigen in early gastric adenocarcinomas versus benign gastric lesions defined by monoclonal antibodies reactive with restricted antigen epitopes

Murine monoclonal antibodies (MAbs) reactive with distinct epitopes on carcinoembryonic antigen (CEA) have been analyzed systematically by radioimmunoassays, Western blotting, and immunohistochemical assays to define CEA expression in adenocarcinomas, benign lesions, and normal tissues of the stomach. Each of four COL-MAbs (COL-1, COL-4, COL-6, and COL-12) reacted preferentially with cell extracts of adenocarcinomas versus those of normal mucosae in solid-phase radioimmunoassays. Using Western blotting analyses MAbs COL-1, COL-4, COL-6, and COL-12 detected only the M(r) 180,000 molecule characteristic of CEA in adenocarcinoma of the stomach; no reactivity was observed in an extract of normal gastric mucosa. Antibody competition radioimmunoassays were then carried out to define relations among COL-MAbs using ¹²⁵I-radiolabeled MAbs and nonradiolabeled MAbs as competitors. A spectrum of formalin-fixed, paraffin-embedded normal, benign, and malignant tissue sections of the stomach were examined for immunoreactivities with COL-MAbs using immunohistochemical assays to define whether the COL-MAbs were able to detect CEA expression in early foci of gastric carcinomas. All of the COL-MAbs generally demonstrated selective reactivities to adenocarcinomas (n = 40) versus benign lesions (n = 15) and normal mucosae (n = 6) of the stomach. From 72 to 100% of adenocarcinomas at early stage (n = 18) were reactive with the COL-MAbs, suggesting that these MAbs might serve as immunohistochemical diagnostic tools to detect early foci of gastric carcinoma. The data reported here indicate that the COL-MAbs can potentially be utilized as radioimmunological and immunohistochemical adjuncts to differentiate early adenocarcinomas from normal mucosae or benign lesions of the stomach on the basis of differential CEA expression.