CD8A and neoplasm: According to existing reports, activation of the MET signaling pathway can induce the state of an immunosuppressive microenvironment through diverse mechanisms, including reducing the infiltration of CD8+ cytotoxic T cells and NK cells (8), down-regulating the immune stimulatory factors CD137, CD252, and CD70 (9), inducing a high infiltration of Tregs in the tumor microenvironment (10, 11), and transforming M1 type TAM (immune activation type) into M2 type TAM (immunosuppressive type) (12, 13), thereby engendering resistance to immunotherapy.