Understanding of Immune Escape Mechanisms and Advances in Cancer Immunotherapy

Figure 2

Multiple pathways of tumor immune escape mechanism. (a) IFN-γ--JAK1/JAK2-STAT1/2/3-IRF1 axis mainly regulates the expression of PD-L1 [13]. If the expression of IFN-γ increases, the expression of PD-L1 will increase. The PD-1/PD-L1 pathway was activated and induced T cell inactivation. (b) IFN-γ activates CTLA-4 expression through phosphorylation of Jak1/2-STAT1 and then competes with CD28 to bind to B7 [14] that inhibits T cell activation. (c) IDO suppresses the immune response by metabolizing tryptophan [15]. Its metabolites inhibit T cell activation and promote tumor proliferation. (d) IDO expression in THP-1 cells increased M2-type cell polarization [16]. M2-type macrophages inhibit the immune system and promote tumor proliferation and metastasis. (e) T cells combine with tumor-associated antigens expressed by tumor cells to exert an immune effect.