Progress on regulation of PD-L1 expression by major inflammatory cytokines in tumor microenvironment

Programmed cell death protein 1 ligand 1 （PD-L1） is an important immune checkpoint protein， and its high expression in tumors often affects the effect of immunotherapy and promotes the malignant progression of tumors. Besides the own factors of the cells， the expression of PD-L1 is regulated by a variety of factors. In recent years， many studies have shown that some inflammatory cytokines in the tumor microenvironment， such as interferon-γ （IFN-γ）， transforming growth factor-β （TGF-β）， tumor necrosis factor-α （TNF-α）， interleukin-6 （IL-6） and so on， regulate PD-L1 expression through various mechanisms， thus promoting the immune escape of tumor cells and affecting the prognosis of patients. In this article， we briefly review the regulatory effects of major inflammatory cytokines on tumor cell PD-L1 expression and the mechanisms in order to provide a reference for improving the clinical efficacy of anti-PD-L1 treatment and studying new tumor immunotherapy pathways.