APC and beta-catenin protein expression patterns in HNPCC-related endometrial and colorectal cancers

Objective: The adenomatouspolyposis coli (APC) and beta-catenin (CTNNB1) genes are the two major components of the Writ signaling pathway that has been shown to play an important role in the formation of certain cancers. The overactivation of the pathway, which results in abnormal accumulation of beta-catenin protein in nuclei, contributes to most colorectal cancers (CRCs), both sporadic and hereditary, as well as sporadic endometrial cancers (ECs). Here, we studied the involvement of APC and beta-catenin in hereditary nonpolyposis colorectal cancer (HNPCC)-related ECs, and compared the expression patterns to those in HNPCC-related CRCs. Materials and methods: Nineteen ECs and 31 CRCs derived from HNPCC patients were immunohistochemically stained with anti-APC- and anti-beta-catenin -antibodies. Results: Tumor-specific loss of APC was observed in 16\% of endometrial cancers (3 of 19) and in 39\% of colorectal cancers (12 of 31). Consistently, the loss of APC expression was associated with nuclear beta-catenin staining. Altogether, aberrant beta-catenin localization was observed in 53\% of ECs (10 of 19) as compared to 84\% of CRCs (26 of 31) (P = 0.02). Conclusion: Our results suggest a frequent overactivation of the Writ signaling pathway in hereditary endometrial cancer. In accordance with studies on sporadic cancers, abnormal accumulation of beta-catenin protein in nuclei occurred much less frequently in HNPCC-related ECs than CRCs, which may reflect organ-specific differences in their pathogenesis.