Effect of Bromodomain 4 protein on epithelial-mesenchymal transition of breast cancer cells and its relationship with prognosis after operation

Abstract

Objective To investigate the effect of Bromodomain 4 (BRD4) protein on epithelial-mesenchymal transition of breast cancer cells and its relationship with prognosis after operation. Methods BRD4 knockdown cell lines (experimental group) and control group were established by BRD4 short hairpin RNA (shRNA) lentivirus and vector lentivirus in MCF-7 breast cancer cells, respectively. The expression levels of E-cadherin and Vimentin were analyzed by Western blotting and the invasive ability of cells in control group and observation group was analyzed by Transwell. The expression of BRD4, E-Cadherin and Vimentin in breast cancer tissues was analyzed by immunohistochemistry. The relationship between the expression of BRD4 and recurrence was analyzed. Results BRD4 knockdown cell lines were successfully established in this study. Western blotting analysis showed that the expression levels of E-Cadherin and Vimentin in the control group (0.57±0.12 and 0.64±0.18) were significantly higher than those in the observation group (0.26±0.09 and 0.31±0.08, t=3.990, P<0.01; t=4.109, P<0.01). The invasive ability of the control group (128.43±15.32) was significantly higher than that in the experimental group (39.76±9.12) (t=3.132, P<0.01). Among 138 patients, 51 had high expression of BRD4 (36.96%), and 87 had low expression (63.04%). The expression of BRD4 protein was positively correlated with the expression of E-Cadherin and Vimentin (r=0.591 and 0.981 respectively, P<0.05). The 3-year recurrence rate (45.10%) in the BRD4 overexpression group was significantly lower than that in the low expression group (19.54%) (LogRank=3.011, P<0.01). Conclusion BRD4 protein is involved in the epithelial-mesenchymal transition of breast cancer cells and is closely related to the recurrence of breast cancer after operation. Key words: Breast cancer; Bromodomain 4; Epithelial mesenchymal transition; Recurrence