| Breast cancer is one of the most serious diseases that threaten life expectancy and quality of women in the world.The etiology of breast cancer is not very clear.Genetic,hormonal,immune and various environmental factors interact with each other and participate in the evolution process of breast cancer.It is recognized that mammary gland is one of the main target organs for gonadal hormone.Both endohormone and ectohormone having effects on it and play a specific role in the development of breast cancer.But the relationship between gonadal hormone and breast cancer is controversial,and clinical conclusions of the risk of breast cancer induced by estrogen are inconsistent.Breast cancer is the malignant tumor from lobular epithelial cell of the breast terminal ductal.During tumor development,mammary epithelial cells can obtain migration ability when they obtained mesenchymal characteristics and lost their typical adhesion and polarity ability,which contributes to the depachment of tumor cells from the original site and their metastasis through blood vessel and lymphatic[1].At present,tight junction(TJs)is thought to have close relationship with cell metastatic phenotype such as cell adhesion,motility, invasiveness.TJs locates on the top of the junction complex among epithelial cells and endothelial cells.TJs presents a lot of functions.It can close intracellular gap,maintain cell polarity,adhesion,permeability and regulate cell proliferation,differentiation.Recent studies showed that abnormality of the structure and function of TJs could induce mammary tumor cells to obtain invasive and metastatic phenotype.Structure and functions of TJs could be regulated by estrogen.Currently,the mechanism of breast cancer invasion and metastasis regulated by estrogen is still unclear.TJs mainly consists of claudins, occludin,junctional adhesion molecules(JAM).Claudin-6 is one of 24 members of claudin family,which located on chromosome 16 p13.3.It encodes a 23 kDa membrane protein which has 4 transmembrane domain, which constructed by 219 amino acids.Currently,it is reported that claudin-6 functions in the embryo and fat formation,differentiation of skin epidermal cells and permeability barrier. However,the relationship between tumor progression and claudin-6 is rarely reported.Our preliminary studies showed that the expression of claudin-6 reduced in human breast cancer cells but increased in ovarian cancer cells.We speculated that the abnormal expression of claudin-6 played a role in the process of incidence,invasion and metastasis of hormone-related tumors.In this study,expression of claudin-6 and estrogen receptor alpha(ERα)in breast cancer were detectd by immunohistochemical staining,their relationship with the clinical indicators of breast cancer were analysed to explore their correlation and clinical significance.Then,expression of claudin-6 in 17β-E2 stimulated MCF-7 cells were detected by RT-PCR and immunofluorescence. Proliferation of 17β-E2 stimulated MCF-7 cells were detected by CCK-8 kit assay.Migration ability of 17β-E2 stimulated MCF-7 cells were detected by cell scrach method.Effects of 17β-E2 on biological behavior of MCF-7 cells were analysed through these tests.The results were as follows:Immunohistochemical staining results showed that:1.The expression of claudin-6 in breast cancer was significantly lower than the control group,P＜0.05.It is negative correlation with pathologic classification,clinical stage and lymph node metastasis in breast cancer.We speculated that claudin-6 funtioned the process of occurrence,development and metastasis in breast cancer.It could be a indicator to evaluate the metastasis of breast cancer.2.The expression of ERa in breast cancer tissue was significantly higher than control group,P＜0.05.It is negative correlation With pathologic classification,clinical stage and lymph node metastasis in breast cancer.It suggested that ERa played a role in the process of occurrence,in breast cancer.It could be a marker for hormone-dependent breast cancer diagnosis and prognosis.3.Expression of claudin-6 and ERa in breast cancer was significantly relevant,P＜0.01.The study of effects of 17β-E2 on MCF-7 cells showed that:1.RT-PCR analysis showed that the expression of claudin-6 in 17β-E2 stimulated MCF-7 cells presented a concentration and time dependent manner.Expression of claudin-6 became the highest when MCF-7 cells were stimulated by 17β-E2 for 24h with the concentration of 5×10-9mol/L.2.Immunofluorescence assay showed that expression of claudin-6 is higher than the control group when when MCF-7 cells were stimulated by 17β-E2 for 24h with the concentration of 5×10-9mol/L.3.CCK-8 analysis showed that growth capacity of MCF-7 cells decreased campared with control group when the expression of claudin-6 is induced by the estrogen.4.Cells scratch test results showed that MCF-7 cell migration ability is decreased compared with control group when the expression of claudin-6 is induced by the estrogenConclusion:The decreased expression of claudin-6 and increased expression of ERαmay present effects on development of breast cancer.They could be a reference indicator for prognosis evaluation of breast cancer.The inhibitory effects of 17β-E2 on growth and migration of MCF-7 cells may be related to claudin-6 expression regulated by 17β-E2. |
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