GAS6 and cancer: CAFs have been reported to establish an immunosuppressive environment by secreting biomolecules, such as IL-6, CXCL12, TGF-β, growth arrest-specific protein 6 (GAS6), fibroblast growth factor 5 (FGF5), growth differentiation factor 15 (GDF15), and hepatocyte growth factor (HGF), which promotes invasive and proliferative behavior in cancer cells [63,64,65].