Inflammation and Cancer: What Can We Therapeutically Expect from Checkpoint Inhibitors?

Programmed death-ligand 1 (PD-L1) is a cell surface protein which is mainly expressed on immune cells as well as on cancer cells and functions as a co-stimulatory molecule for T lymphocytes. It is capable of inducing apoptosis in T-cells via PD-1 which leads to impaired cytokine production and loss of cytotoxicity of activated T-cells. This represents a possible escape mechanism for cancer cells. Tumor infiltration by mononuclear cells and tumor aggressiveness was found to be associated with PD-L1 expression. In light of possible autoimmunological side effects, it remains currently unclear which patient will benefit most from this novel therapeutic approach. Furthermore, immunohistochemistry for PD-L1 has not been well standardized until now. In addition, the combination of chemotherapy with checkpoint inhibitors in different clinical settings needs to be established for the near future in order to avoid overtreatment and also unnecessary cost expenditures for the health care system.