MIF and pancreatic neoplasm: There are several specific exosomes that can contribute to liver metastasis in pancreatic cancer via forming an inflammatory and immunosuppressive microenvironment in the liver, e.g., macrophage migration inhibitory factor (MIF) [49], Integrin ITG αvβ5 [50], Netrin-1 [28], Lin28B [51, 52] and CD44 [53, 54] (Fig. 1).