[Methylation of Runx3 promoter in different breast lesions]

To investigate the methylation status of Runx3 promoter and Runx3 expression in breast lesion tissues.

One hundred and fourteen breast lesions, including 35 cases of fibroadenoma, 39 cases of intraductal carcinoma, 40 cases of invasive ductal carcinoma, and 33 cases of normal breast tissue from Fabruary 2010 to August 2012 were included in this study. Runx3 protein expression was assessed by immunohistochemical SP method; whereas methylation of Runx3 promoter was assessed by high resolution melting (HRM) analysis.

Runx3 protein was mainly expressed in the cytoplasm of ductal epithelial cells. The expression rates of Runx3 in normal breast tissue, fibroadenoma, ductal carcinoma in situ, invasive ductal carcinoma were 87.9% (29/33), 85.7% (30/35), 53.8% (21/39), and 40.0% (16/40) respectively. The methylation rates of Runx3 promoter were 12.1% (4/33), 20.0% (7/35), 46.2% (18/39), and 57.5% (23/40), respectively. Correlation analysis between promoter methylation and protein expression of Runx3 in different breast tissue showed the r value in normal breast tissue, fibroadenoma, ductal carcinoma in situ and invasive ductal carcinoma was -0.431 (P = 0.012), -0.408 (P = 0.015), -0.589 (P = 0.000) and -0.743 (P = 0.000) respectively.

Runx3 protein expression shows a downward trend in ductal carcinoma in situ and invasive ductal carcinoma, meanwhile its promoter methylation increases significantly. The methylation of Runx3 promoter may be one of the important factors in the occurrence and development of breast cancer.