Abstract: Abstract： Objective To investigate the correlationship between DNMT3a, DNMT3b protein expressions and the state of promoter methylation of ERα gene and ERα protein expression in the development of sporadic breast cancer. Methods A total of 180 patients with sporadic breast cancer and 30 patients with breast fibroadenoma were included in this study. The expressions of DNMT3a and DNMT3b protein were detected by immunohistochemical method. The state of promoter methyla⁃ tion of ERα gene was detected by methylation specific PCR in 97 patients with sporadic breast cancer. Results There were no significant differences in positive expression rates of DNMT3a and DNMT3b protein between breast fibroadenoma and breast cancer. There were higher expression levels of DNMT3a and DNMT3b in breast cancer patient of Ⅲ~Ⅳ stages than those ofⅠ~Ⅱstages. The expression of DNMT3a was significantly higher in patients with lymph node metastasis than that of patients without lymph node metastasis (P < 0.05). Of 97 cases of breast cancer patients, ERα gene promoter methylation oc⁃ curred in 39 cases (40.2%). The positive expression of DNMT3a protein was positively correlated with the ERα gene methyla⁃ tion (rS=0.250). The DNMT3a protein expression showed a significant influence to the overall survival (OS) in patients of breast cancer (P=0.035), no significant influence to the disease-free survival (DFS) (P=0.064). DNMT3b protein expression showed no significant influence to OS and DFS of patients with breast cancer (P = 0.914 and 0.961). Conclusion The posi⁃ tive expressions of DNMT3a and DNMT3b are correlated with the invasion, metastasis and poor prognosis of sporadic breast cancer. DNMT3a was positively correlated with the state of ERα gene promoter methylation. The inhibition of DNMT3a and DNMT3b may have advantages in the prevention and treatment of sporadic breast cancer.

Key words: sporadic breast cancer, DNMT3a, DNMT3b, ERα, DNA methylation, promoter regions (genetics)