PD-L1/PD-1 blockade in breast cancer: The immunotherapy era (Review)

[[abstract]]Breast cancer is a common malignant tumor in women. Triple‑negative breast cancer (TNBC) is highly invasive with a high rate of metastasis and poor prognosis. Programmed death ligand 1 (PD‑L1) plays an important role in mediating the escape of tumor cells from immune surveillance. There have been significant advances in understanding the biology of TNBC. This review presents a detailed discourse on the available data on the expression of PD‑L1 in breast cancer and preliminary clinical outcome of PD‑L1/PD‑1 inhibi‑ tors in breast cancer patients. Early clinical trials involving PD‑L1/PD‑1 inhibitors have exhibited efficacy in tumor response and/or disease control in patients with refractory metastatic breast cancer, particularly TNBC. Furthermore, the mechanisms and factors that influence the immunoediting process are summarized and their functions in detail are analyzed. Contents 1. Introduction 2. Overview of tumor immunotherapy 3. Biological characteristics of PD‑1/PD‑L1 4. Prognostic significance of PD‑1/PD‑L1 5. Significance of targeting PD‑1/PD‑L1 monoclonal antibody 6. Anti‑PD‑L1 therapy for breast cancer 7. Future perspectives