CAFs can generally promote metastasis by inducing cancer cell survival and proliferation at the primary site in a paracrine manner, through secreting a myriad of growth factors and cytokines including heparin-binding epidermal growth factor (EGF) [54], epiregulin [55], hepatocyte growth factor (HGF) [56], IGF [57], TGF-β [58], interleukin (IL)-6 [59], CXCL12 [60], and IL-17B [61] (Figure 3). Here, IGF1 is linked to cancer.