Figure 1.

Key immunosuppressive mechanisms of PDAC. A) Immune evasion tactics include 1) low levels of mutation resulting in few non-self antigens, 2) KRAS signaling lowers MHC I expression by tumor cells, 3) exosomes containing miRNA silence dendritic cell (DC) expression of MHC II molecules, and 4) increased expression of anti-phagocytic molecules like CD47 prevent APC processing and tumor clearance. B) The tumor suppresses immune responses through PD-L1 expression, MDSC recruitment, and high IDO expression. C) The highly fibrotic extracellular matrix of the tumor creates a physical barrier preventing T cell infiltration into the tumor.