RESUMEN
BACKGROUND AND AIMS: The adenomatous polyposis coli (APC) protein plays a crucial role in the regulation of beta-catenin, which is linked to the cell adhesion molecule E-cadherin. Furthermore, beta-catenin and cyclooxygenase-2 (COX-2) are both involved in the activation of nuclear transcription factors inducing cell proliferation. Germline mutations in the APC gene are the cause of familial adenomatous polyposis (FAP). To characterise the expression pattern of these proteins in FAP in comparison with sporadic adenomas, we studied 18 FAP-associated adenomas, 16 sporadic adenomas and seven normal colonic controls. METHODS: E-cadherin, beta-catenin, COX-2 expression and the proliferative index (Ki67) were assessed by immunohistochemistry (index of expressing cells / total number of cells) in adenomatous mucosa, adjacent non-neoplastic tissue and normal colonic controls. RESULTS: E-cadherin expression was significantly and homogeneously reduced in FAP adenomas (24%; 95%CI 16-32; sporadic adenomas 61%; 38-84; normal controls 98%; 96-100). Membraneous beta-catenin expression was significantly reduced in both FAP (30%; 11-49) and sporadic (42%; 19-65) adenomas (normal controls 96%; 88-104), whereas marked nuclear staining occurred in sporadic, but not in FAP adenomas. Stromal COX-2 expression and the proliferative index were increased only in sporadic adenomas (sporadic adenomas: COX-2 12%; 7-17, Ki67 24%; 15-33, FAP adenomas: COX-2 8%; 5-11, Ki67 5%; 2-9, normal controls: COX-2 4%; 2-7, Ki67 6%; 1-11). CONCLUSION: Proteins involved in cell adhesion and cell proliferation, especially E-cadherin, are expressed differently in FAP and sporadic adenoma, pointing to possible differences in the molecular pathways to adenoma.