The Association Of BAG-1and EGFR Expression And The Influence Of BAG-1to Molecular Target Therapy In Breast Cancer

Objective:Breast cancer is a highly heterogeneous tumor at the molecular level, some patients emerge resistance in the molecular target therapy. At present, many researchers are focusing on apoptosis and its mechanisms. In our research, we test the expression of BAG-1in breast cancer cells, analyse its association with epidermal growth factor receptor (EGFR), and try to explore if there’s some influence of BAG-1expression to the sensitivity and resistance of molecular target therapy in breast cancer.Methods:First, we culture breast cancer cell lines with different expression of EGFR, such as T47D, MDA-MB-231, MCF-7and SKBR3cell line. Then, test the expression of BAG-1mRNA in breast cancer cells by RT-PCR and real-time PCR and the expression of BAG-1protein by Western blot. Next, to the EGFR(+) breast cancer cells which have high expression of BAG-1, down-regulated the expression of BAG-1by SiRNA technique and test the variation of EGFR and BAG-1expression by real-time PCR and Western blot. Last, to the BAG-1down-regulated breast cancer cell, give different concentration of Gefitinib (EGFR inhibitor) and test its reaction by MTT.Results:1. Compared to the EGFR(-) breast cancer cell lines (MCF-7and SKBR3), EGFR(+) breast cancer cell lines (T47D and MDA-MB-231) have higher expression of BAG-1(P<0.05), especially, T47D cell line have the highest expression of BAG-1.2. Select the effective SiRNA sequence and transfect to T47D breast cancer cells. When transfected BAG-1SiRNA with50nM,48h later total cellular RNA and protein were extracted. As a result, BAG-1SiRNA transfected cells dramatically decreased both BAG-1mRNA and protein expression compared to the negative control SiRNA-transfected cells (36.9%vs.100%, P<0.05). Relatively, both EGFR mRNA and protein expression were increased about1.56folds in BAG-1SiRNA transfected cells (P<0.05).3. To the BAG-1SiRNA transfected cells, give different concentration of Gefitinib. Along with the increased concentration of Gefitinib, the cell control rate also increased. The control rate of BAG-1SiRNA transfected cells is higher than the negative control SiRNA-transfected cells (P<0.05). Conclusion:1. In breast cancer cells, BAG-1and EGFR expression are related. When BAG-1mRNA and protein expression are decreased by BAG-1SiRNA, EGFR mRNA and protein expression are increased.2. Down-regulated BAG-1expression in breast cancer cells could increase the sensitivity of breast cancer cells to EGFR inhibitor. Initially proved that BAG-1can be as a potential target in the process of breast cancer molecular target therapy resistance.