Résumé
BACKGROUND: APC and E-cadherin are the key molecules in the Wnt/beta-catenin pathway. We attempted to define the epigenetic alteration of APC and CDH1 (the E-cadherin gene) and the expression of Wnt-related molecules in human mammary carcinomas. METHODS: Sixty-four mammary carcinomas, including 52 invasive ductal carcinomas (IDCs) and 12 invasive lobular carcinomas (ILCs), were evaluated using methylation-specific PCR and immunohistochemistry. We performed immunohistochemistry for E-cadherin, beta-catenin, APC, Wnt1, cyclin D1, ER, PR and C-erb B2. RESULTS: Hypermethylation of APC and CDH1 was observed in 38 (59%) and 28 (44%) cases, respectively. CDH1 hypermethylation in ILCs was increased compared to that in IDCs (p=0.002) and it was associated with the loss of E-cadherin (p=0.02) and beta-catenin (p=0.042). APC methylation was positively correlated with the ER expression (p=0.021). Abnormal cytoplasmic localization of beta-catenin was found in 10 cases and any expression was not detected in six cases. In ILCs, the E-cadherin or beta-catenin expression was markedly decreased compared to that in IDCs (p<0.001 in both). CONCLUSIONS: Methylation of APC or CDH1 was relatively frequent in mammary carcinomas. The loss of E-cadherin in mammary carcinoma was associated with CDH1 methylation, and abnormal beta-catenin expression was related to the loss of E-cadherin in ILC.