TIGIT and neoplasm: In the physiological state, CD155 is more highly expressed on antigen-presenting cells and is involved in various processes such as cell adhesion, migration and proliferation [15]; in the pathological state, it can be overexpressed on tumor cells, promoting tumor proliferation, invasion and immune escape; meanwhile, it can act as a ligand and bind to the receptor molecules, TIGIT and CD226, with the function of regulating the immunity of T cells and NK cells [16].