CAFs also express a variety of growth factors, cytokines, and chemokines that facilitate cancer cell invasion, including TGF-β1, leukemia inhibitory factor (LIF), growth arrest-specific protein 6 (GAS6), fibroblast growth factor 5 (FGF5), growth differentiation factor 15 (GDF15), and hepatocyte growth factor (HGF) [10]. Here, GAS6 is linked to cancer.