Research progress of PD-1/PD-L1 immunotherapy in gastrointestinal tumors

Gastrointestinal tumor (GIT) is a common malignant tumor of the digestive system, which seriously threatens people's health and life. With the deepening of the study on the mechanism of tumor immune escape, programmed death receptor ligand 1 (PD-L1) has been proved to interact with the tumor microenvironment to mediate tumor immune escape. PD-L1 inhibitor is a hot spot in tumor immunotherapy in recent years, which can restore the activity of T cells, enhance the body's ability of immune response, and ultimately enable the immune system to effectively identify and kill gastric cancer cells, then achieve long-term tumor remission in patients with GITs. At present, variety of PD-L1 inhibitors such as pembrolizumab, nivolumab and avelumab have been approved for the market, and they have achieved good results in clinical studies on the GIT. This paper reviews the progress of PD-1/PD-L1 immunotherapy in GITs which include gastric cancer, colon cancer and rectal cancer.