TIGIT and neoplasm: Understanding the importance of TIGIT in the complex regulatory network of positive and negative immunomodulatory receptors on T lymphocytes, tumor cells, and antigen-presenting cells, as well as the negative relationship between CD155 expression and the response to anti-PD-1 treatment, offered hope for the possibility of improving the efficacy of treatment by using further signaling pathways in the immune system [21,29] Figure 1.