Changes in CpG island promoter methylation pattern during ductal breast carcinoma

Aberrant promoter methylation of several known or pu-tative tumor suppressor genes occurs frequently during carcinogenesis, and this epigenetic change has been con-si der ed as a po ten ti al mol ec u la r ma rke r fo r ca nc er. We examined t he methylation status of n ine g enes ( APC, CDH1, CTNNB1, TIMP3, ESR1, GSTP1, MGMT, THBS1 , and TM S1 ), by quantitative methylation specific P CR . Synchronous preinvasive lesions (atypical ductal hyper-plasia and/or ductal carcinoma in situ ) and invasive duc-tal breast carcinoma from 52 patients, together with pure lesions from 24 patients and 12 normal tissues paired to tumor a nd 20 normal brea st distant from t umor were analyzed. Aberrant promoter methylation was detected in both preinvasive and invasive lesions for genes APC, CDH1, CTNNB1, TIMP3, ESR1 ,and GSTP1 . H ow ever, hierar chic al m ix ed model and Gener alized Estimating Equations model a nalyses show ed that only APC, CDH1, and CTNNB1 promoter regions showed a higher frequency and methylation levels in pathologic samples when compared with normal breast. Whereas APC and CTNNB1 did not show differences in methylation levels or frequencies, CDH1 showed higher methylation levels in invasive tumors as compared with preinvasive lesions (P < 0.0 4, Mann -Wh itn ey test wi th permu tat io n corr ec -tion). The analysis of APC, CDH1 , and CTNNB1 methyl-ation status was able to distinguish between normal and pathologic samples with a sensitivity of 67% (95% confi-dence i nterval, 60-71%) a nd a s pecificity of 75% (95% confidence interval, 69-81%). Our data point to the direct involveme nt of APC, CDH1 ,and CTNNB1 promoter methylation in the early stages of breast cancer progres-si on and su gge st th at th ey ma y re p re se n t a use ful to o l for t he detection of t umor cells in clinical specimens.