Epigenetic alterations of CDH1 and APC genes: relationship with activation of Wnt/beta-catenin pathway in invasive ductal carcinoma of breast.

Activation of canonical Wnt/beta-catenin pathway in Invasive Ductal Carcinoma of Breast (IDCs) was recently reported from our laboratory. Herein, we analyzed promoter methylation status of CDH1 and Adenomatous polyposis coli (APC) genes in 50 IDCs and correlated with expression of E-cadherin (E-CD) and APC proteins and with activation of oncogenic Wnt/beta-catenin signaling pathway components, Dvl, beta-catenin and CyclinD1. Further, Wnt/beta-catenin driven epithelial mesenchymal transition (EMT) was investigated by correlating the expression of Dvl, beta-catenin and CyclinD1 with vimentin expression in these IDCs. Promoter hypermethylation was observed in 25/50 (50%) IDCs for CDH1 and in 11/50 (22%) tumors for APC, associated with loss of expression of E-CD and APC proteins; concordant hypermethylation of these genes was observed in paired patients' sera. Further, 57% of tumors harboring CDH1 methylation and 50% tumors harboring the methylated APC gene showed nuclear localization of beta-catenin, suggesting activation of the canonical Wnt/beta-catenin pathway. Our study demonstrates significant association between vimentin expression and nuclear beta-catenin (p=0.001; Odds ratio (OR)=25.6) and Dvl (p=0.023; OR=8.0), suggesting that EMT may be driven by Wnt/beta-catenin activation in IDCs. In conclusion, we demonstrate correlation of CDH1 and APC promoter methylation with loss of E-CD and APC proteins and with activation of Wnt/beta-catenin signaling pathway. Association of nuclear Dvl and beta-catenin with vimentin expression suggests the importance of Wnt/beta-catenin pathway driven EMT in IDCs. The concordance between CDH1 and APC methylation in IDCs and paired circulating DNA underscores the utility of serum DNA as a non-invasive tool for methylation analysis in IDC patients.