TIGIT and neoplasm: The suppression of T cell function may be exerted by the overactivation of TIGIT, which is caused by the overexpression of its ligand, CD155, thus creating an immunosuppressive microenvironment and inducing tumor escape.104 Additionally, studies show that increased expression of TREM-1 elicits T cell dysfunction through the modulation of PD-L1, which impairment fails to improve the related immunosuppression.176 Additionally, HSCs141,142 and CAFs152 can also contribute to the development of an immunosuppressive framework.