MIF and neoplasm: The exosomes secreted by tumor cells carry various inflammatory factors and immunosuppressive factors (“fertilizer”), such as macrophage migration inhibitory factor (MIF) (57) and PD-L1 (58), which perform in the surrounding or distant normal tissues or organs, causing vascular leakiness (59), inflammation infiltration (60), extracellular matrix (ECM) remodeling (61), and immune suppression (62).