Objective:To investigate the expression of estrogen receptor in breast cancer cell and its effect on epidermal growth factor.Methods:The membrane estrogen receptor(m ER)expression at m RNA and protein levels in human breast cancer cell line MCF-7

MDA-MB-231 and MDA-MB-435 were detected by real time fluorescent quantitative PCR and Western blot. Stable m ER knowdown cell lines were constructed by lentiviral mediated m ER sh RNA. The effect of membrane estrogen(m E2) and traditional estrogen on growth of(ERα+ and ERα-)as well as on expression of epithelial growth factor receptor(EGFR)and epidermal growth factor(EGF)were analyzed by MTT. Results:m ER was expressed in MCF-7

MDA-MB-231 and MDA-MB-435 cell lines

with MCF-7 cell having the highest expression. m ER m RNA and protein levels in knowdown stable cells by lentiviral mediated sh RNA were significantly lower than those of MCF-7 cells(P<0.05). Estrogen can promote proliferation of MCF-7 and MCF-7/ER- cell and there was not statistical significance among three lines(P>0.05). But after treatment by m E2

the proliferation of MCF-7/ER- was significantly lower than that of MCF-7 cells(P<0.05). After MCF-7 and MCF-7/ER alpha cells being stimulated by estrogen

there was no statistical difference in EGF m RNA and protein levels between MCF-7/ER- cells and MCF-7(P>0.05). But after being stimulated by m ER

EGF m RNA and protein levels was significantly decreased in MCF-7/ER- cells than in MCF-7(P<0.05). Conclusion:This study is expected to provide a molecular therapeutic targeting for the treatment of breast cancer.