CXCL12 and neoplasm: In addition to CAF-derived soluble factors CXCL12, IL-6, and TGF-β, CAFs also inhibit antitumor cytotoxicity of CD8+ T cells through the acquisition of immune checkpoint molecules, such as programmed cell death ligand 1 (PD-L1), PD-L2, and Fas ligand in several tumor types [13,14].