Effects Of Exogenous ERβ Expression On The Cell Growth Properties And Endocrine Therapeutic Of Breast Cancer Cells

Breast cancer is one of the most common female malignancies. In breast cancerdevelopment and process, endogenous estrogen plays a main role, about50%of theprimary breast cancer associated with estrogen. For many years the presence ofimmunopositive ERα, alone or with expression of progesterone receptor （PR）, wasused as a criterion for treatment of patients with adjuvant antiestrogen therapy such astamoxifen. Only60%of patients with ERα-positive （ER+） tumors respond to adjuvantantiestrogen treatment, and there is about10%of patients with ERα negative respondto adjuvant antiestrogen treatment.Since ERβ was found by Mosselman, because of its potential role in breast cancer,and the value to predict the reaction of endocrine therapy, ERβ became researchfocus.Because ERβ and ERα are different in molecular structure and distribution,they have different biological function.Until recent reserch there are large differencesin ERβ’s biological function and it’s role in endocrine therapy. Research shows thatERβ’s biological function is affected by ERα,so we want to study ERβ’s biologicalfunction in different ERα Expression state.Purpose: to study the effects of exogenous ERβ on the growth of breast cancerMCF-7and MDA-MB-231cells under different treatment with estrogen or tamoxifen;to discuss ERβ’s biological function and the relation between ERα and ERβ;to explorethe possibility that ERβ can be used to predict the reaction of endocrine therapy togetherwith ERα.Methods:（1） Extract plasmid pReveicer-M72-ERβ which contains ER β gene, tested and verified through agarose gel electrophoresis experiment.（2）An eukaryoticexpression vector containing1.6kb of human entire coding sequence of ERβ（pReveicer-M72-ERβ） was transfected into MCF-7and MDA-MB-231cells usingLipofectmine LTX, setting up empty vector group and blank control group to twokinds of cells.（3）20hours later after transfection, using Fluorescencemicroscope,immunefluorescent, Western Blot to validate ER β expression.（4） settingsix groups of MCF-7，MCF-7^ERβ，MCF-7^<sup>空，MDA-MB-231，MDA-MB-231ERβ，MDA-MB-231^<sup>空,the growth properties of each group under different treatment,including E2and tamoxifen,were observed,using MTT, and set untreated group forcontrol.Results:（1） Extracted plasmid pReveicer-M72-ERβ was Consistent with expectedverified through agarose gel electrophoresis experiment.（2）Western blot analysisshowed that the protein level of ERβ in MCF-7^ERβand MDA-MB-231ERβweremarkedly increased compared with each control group.（3） MDA-MB-231ERβgroupcells growth faster than MDA-MB-231and MDA-MB-231^<sup>空,but there is no differenceamong three group cells under E2and tamoxifen.（4） ERβ expression in MCF-7^ERβinhibit cell growth,and inhibition of proliferation of MCF-7^ERβin the presence of E2was observed, MCF-7^ERβcells proliferated at the same rate as MCF-7^<sup>空and MCF-7inthe presence of tamoxifen.Conclusion:（1） In the presence of ERα, expression of ERβ inhibit cell growth,reduce the sensitivity of the cells to estrogen,but does not increase the resistance totamoxifen.（2） When there is no ERα exist, expression of ERβ can accelerate cell growth,but have no influence on cells under the treatment of estrogen and tamoxifen.