Docetaxel treatment together with CTLA-4 knockdown enhances reduction of cell viability and amplifies apoptosis stimulation of MCF-7 breast cancer cells.

Breast cancer is the most frequent cancer in women with a 20% mortality rate. The fate of patients suffering from breast cancer can be influenced by immune cells and tumor cells interaction in the tumor microenvironment (TME). Immune checkpoints such as Cytotoxic T-lymphocyte-associated antigen-4 (CTLA-4) are regulators of the immune system and defend normal tissues from immune cell attacks but they can be expressed in breast cancer tissue and facilitate immune evasion of tumoral cells. Based on this, here we studied the role of CTLA-4 silencing by specific siRNA in MCF-7 breast cancer cell line together with Docetaxel treatment which is one of the robust chemotherapy agents to demonstrate the significance of combining chemotherapy with efficient targeted therapy in tumor regression. The MCF-7 breast cancer cell line was transfected with CTLA-4-siRNA through the electroporation method, then received an appropriate dose of Docetaxel determined by MTT assay. Flow cytometry was utilized to investigate the consequence of simultaneous CTLA-4 gene silencing and Docetaxel treatment on the apoptosis and cell cycle of MCF-7 cells. The expression levels of Bax and Bcl-2 were also investigated using quantitative real-time PCR. Compared to control groups, CTLA-4-suppressed and Docetaxel-treated cells became more susceptible to apoptosis and cell cycle arrest at the G2-M phase. The additive effect of CTLA-4 knockdown together with Docetaxel treatment significantly downregulated BCL-2 level and upregulated BAX expression. Our findings support the idea that combining chemotherapy such as Docetaxel with efficient targeted therapy against inhibitory immune checkpoints can be a promising strategy in cancer treatment.