Accumulation of beta-catenin protein and mutations in exon 3 of beta-catenin gene in gastrointestinal carcinoid tumor.

The molecular basis of carcinogenesis in gastrointestinal carcinoid tumors is not well understood. To clarify the contribution of the Wnt/beta-catenin signaling to this type of carcinogenesis, we investigated 72 cases of gastrointestinal carcinoid tumor both immunohistochemically and by direct sequencing of beta-catenin. Accumulation of beta-catenin in the cytoplasm and/or nucleus was observed in 57 cases (79.2%). We also detected mutations in exon 3 of beta-catenin in 27 cases (37.5%) and one mutation in APC (1.4%). Our results suggest that alterations in the Wnt/beta-catenin signaling pathway may be involved in the development of gastrointestinal carcinoid tumors.