Immune checkpoint biomarkers are molecules found in the tumor microenvironment or in the patient's bloodstream that can indicate how a cancer patient might respond to certain immunotherapies. These biomarkers are often proteins involved in the regulation of immune responses, helping to maintain self-tolerance and prevent autoimmune reactions. Immune checkpoints can either stimulate or inhibit immune responses, and in the context of cancer, they often act as brakes on the immune system, preventing it from attacking tumor cells.
