LRP6 Promotes Breast Cancer Proliferation,Invasion And Metastasis Through Wnt/β-catenin Pathway

BackgroundThe incidence of breast cancer occupies the first place in female malignant tumors,and it is also the main cause of female tumor deaths.Most type of the breast cancer are invasive breast cancer.Improving the overall survival rate and prognosis of patients of invasive breast cancer has increasingly become the focus of clinical diagnosis and treatment.Therefore,according to the mechanism of breast cancer,effective treatment is adopted through early detection of relevant molecular biomarkers to predict and improve the long-term prognosis of patients,which is very important for the patients with breast cancer.LRP6 belongs to the low-density lipoprotein receptor(LDLR)family and has special function.It is confirmed that LRP6 has a cancer-promoting effect on epithelial cell tumors through mouse model studies.However,It still need to be supplemented that related studies on the prognosis and tumor progression of LRP6 in patients with invasive breast cancer.This study is based on analyzing the effect of LRP6 over-expression on the prognosis of breast cancer and exploring the related effects of LRP6 on breast cancer cell proliferation,invasion and metastasis through the Wnt/β-catenin signaling pathway.MethodsImmunohistochemical method was used to detect the expression of 150 breast cancer specimens.The chi-square test was used to analyze the relationship between LRP6 expression and clinical pathological characteristics of breast cancer.The Kaplan-Meier method was used to perform survival analysis.And the Cox proportional hazard regression model was used to explore the potential risk factors of breast cancer.The expression level of LRP6 m RNA in breast cancer cell lines was verified by real-time fluorescent quantitative PCR(RT-q PCR).The small interfering RNA of LRP6(si-LRP6)was transfected into breast cancer cell lines.CCK8 and plate cloning experiment were used to detect the proliferation ability of transfected cells..Using transwell experiment and scratch experiment to detect after transfection.Transwell assays and scratch assays were used to detect the changes in the invasion and migration ability of cells after transfection.Western blotting was used to detect the changes of cells.Flow cytometry was used to detect the apoptosis of breast cancer cells after inhibiting the expression of LRP6.Breast cancer cells stably knockdown LRP6 were inoculated subcutaneously under the armpit of nude mice to establish subcutaneous tumor model of nude mice and the effect of LRP6 on the proliferation of breast cancer.The expression of LRP6 in subcutaneous tumors were detected by immunohistochemistry.The expression of ki-67 of nude mice cells was observed with immunofluorescence.ResultsHigh expression of LRP6 was observed in 89 out of 150(59.3%)breast cancer cases,as detected by microarray of breast cancer tissue.Chi-square tests showed no significant correlation between LRP6 expression and tumor size,lymph node staging,or mitosis.Survival analysis showed that the overall survival rate of tumor patients with high LRP6 expression was significantly lower than that of patients with low LRP6 expression.Univariate and multivariate regression analyses revealed that LRP6 was an independent risk factor for breast cancer and was negatively correlated with the prognosis of breast cancer.Compared with healthy human breast epithelial cell line,the expression of LRP6 in breast cancer cell line MCF-7 was increased.Compared with the control group,small interference RNA(si-RNA)knockdown of LRP6 significantly reduced the clonogenic rate as well as the migration and invasion abilities of MCF-7 cells.In the scratch experiment,the wound healing ability of the LRP6 knockdown was significantly weaker than that of the control group.After knocking down the expression of LRP6 in MCF-7 cells,the apoptosis rate of the cells increased.The downstream effector molecules(c-myc,MMP2,Cyclin D1,E-Cadherin,vimentin)of the Wnt/β-catenin pathway showed low expression,which could down-regulate the Wnt/β-catenin pathway.There were significant differences in tumor growth weight and volume between lentivirus transfected LRP6 knockdown MCF-7 cell line and control MCF-7 cell line in nude mice.The expression of ki-67 in nude mice subcutaneous tumor cells was decreased in LRP6 low expression group ConclusionsThe over-expression of LRP6 is related to the downstream effector molecules of Wnt/β-catenin pathway(c-myc,MMP2,Cyclin D1,E-Cadherin,vimentin),and it plays an important role in tumor growth,migration and invasion.LRP6 may be a key biomarker for poor prognosis of breast cancer.