DNA promoter hypermethylation profiles in breast duct fluid

DNA methylation of tumor-suppressor genes occurs early in the molecular transformation of precursor events to breast cancer and is therefore of interest to screening in high-risk women. The aim of this study was to use tumor-suppressor genes that have previously been shown to be cancer predictive in tissue to evaluate the potential of DNA methylation assays in cells from duct lavage (DL) fluid. The frequency of target gene DNA methylation in tissue and DL of cancer and healthy control patients was assessed, and an association of DNA methylation between different duct systems in the same breast was explored. The cancer and control groups were identified in the outpatient clinic when surgical treatment was finalized. Tumor, adjacent tissue and bilateral DL samples for comparative DNA methylation studies were obtained during surgery from women with cancer. In the healthy control group, samples of tissue and DL were collected. Reverse transcriptase methylation-specific PCR was conducted on modified DNA purified from 42 cancer biopsies, 41 benign excision cavity biopsies (internal control), 29 benign biopsies (external control), and 119 DL specimens. A validated panel of cancer predictive genes was analyzed in the study bank of tissue and DL samples from cancer and healthy patients. The sensitivity of DNA methylation in DL samples compared with matched cancer tissue was highest for SCGB3A1 (90 %), CDH13 (91 %), and RARB (83 %). The genetic algorithm selected RASSF1A, RARB, and IGFBP7 as the optimum predictor set for detecting DNA methylation in cancer tissue. The optimum area under the ROC curve for DNA methylation in cancer compared with internal control healthy tissue from excision margins was 0.84. The area under the ROC curve for DNA methylation in cancer DL compared with contralateral benign DL was 0.76. DL cytology was not a helpful predictor of breast cancer. This study shows that relative patterns of tumor-suppressor gene hypermethylation in breast cancer tissue are significantly reflected in the DL from the cancer affected breast. Using DL, nonconcordant patterns of DNA methylation between different duct systems confer independent oncologic potential for distinct breast lobes. The approach of DNA methylation in DL may be substantiated by a larger trial of breast cancer biomarkers.