Hepatic stellate cells are promoted to secrete TGF-β and upregulate fibronectin production in the liver via PDAC-derived exosomes, while macrophages are recruited through macrophage migration inhibitory factor (MIF) to form premetastatic niches.377 Under hypoxic conditions, exosomal miR-301a secreted by pancreatic cancer cells has been demonstrated to mediate M2 macrophage polarization via the PTEN/PI3Kγ signaling pathway, thereby facilitating cancer metastasis.378. Here, MIF is linked to cancer.