(5) Other representative paracrine signaling pathways: Apart from mentioned above, various paracrine components or intercellular signaling are involved in PSCs activation and PSCs (or CAFs)-cancer cells interactions (Table 2), including Ca2+ signaling, VEGF, PDGF, Toll-like receptors (TLRs) signaling, HIF-1α signaling, TGF-β/Smad pathways, tumor necrosis factor-α (TNF-α), monocyte chemoattractant protein-1 (MCP-1), and periostin, which exert various influences on PDAC pathology [15, 34, 65–83] (Table 2). Here, CCL2 is linked to cancer.