Expression of tumor-associated polymorphic epithelial mucin and carcinoembryonic antigen in gastrointestinal carcinoid tumors. Implications for immunodiagnosis and immunotherapy.

BACKGROUND

Gastrointestinal neoplastic epithelium of glandular origin commonly produces N-linked and O-linked glycoproteins such as carcinoembryonic antigen (CEA) and tumor-associated polymorphic epithelial mucin (PEM). Antibodies to these glycoproteins increasingly are being used in immunodiagnosis and/or immunotherapy. Although GI carcinoid tumors have a neuroendocrine immunophenotype and generally have an indolent clinical course compared with their adenocarcinomatous counterparts, they also arise from undifferentiated crypt epithelium. The purpose of this study was to determine whether GI carcinoids similarly expressed epitopes for CEA and PEM.

METHODS

Thirty-nine GI carcinoid tumors from various topographic sites were analyzed by immunohistochemistry using the murine monoclonal antibodies B72.3, ACT19, and T84. The former two antibodies recognize epitopes in PEM, whereas the latter is an anti-CEA antibody, which was confirmed using enzyme-linked immunosorbent assays.

RESULTS

The majority of carcinoid tumors (74%), particularly jejunoileal carcinoids, reacted for ACT19 antibody, whereas considerably fewer reacted for B72.3 (31%) and T84 (26%). The extent of staining was also greatest with ACT19. The GI mucosa adjacent to or overlying the carcinoid tumors also stained for the various antibodies.

CONCLUSIONS

The extent and degree of positivity of carcinoid tumors for ACT19 raises the possibility that this antibody may be used in the future for the radioimmunodiagnosis and/or immunotherapy of these tumors, particularly in cases that are multicentric, unresectable, or with metastatic disease.