CXCL12 and cancer: In many types of cancers, tumor cells secrete the chemokine CXCL12 to induce the infiltration of a large number of immature pDCs, and the cytokines of VEGF, TNF-α, TGF-β and IL-10 secreted in tumor microenvironment inhibit the maturation and activation of pDCs, then make it unable to produce IFN-α.