The effects of chemotherapeutic drugs on PD-L1 gene expression in breast cancer cell lines

Breast cancer is the most common cancer among women in terms of prevalence and mortality, and chemotherapy is one of the most effective treatments at higher stages. However, resistance to chemotherapy is the main obstacle in the treatment of this cancer. Accumulated evidence identified the PD-L1 protein as an essential protein in the development of different cancers. Abnormal expression of this protein in various tumor cells is linked to cancer development and inhibiting the function of immune cells, which correlated with reduced beneficial effects of chemotherapy drugs. In the present study, the effects of common chemotherapy drugs including doxorubicin, paclitaxel, and docetaxel on the expression of the PD-L1 gene were investigated by qRT-PCR before and after the treatment with these drugs in MD231, MD468, SKBR3 breast cancer cell lines. Also, the MTT test was applied to examine the effects of drugs on the growth and proliferation of cancer cells considering PD-L1 expression. The expression of the PD-L1 gene increased after 24 and 48 h of treatment with chemotherapy drugs. The obtained results indicate the enhancing effects of chemotherapy drugs on PD-L1 gene expression, which have a suppressive effect on the immune system against breast cancer. The use of these drugs as the first line of chemotherapy in triple-negative breast cancer is not recommended. However, there is still a need for further experimental and clinical research on the exact effects of these drugs on undesired immune cells exhaustion in breast cancer therapy.