CXCR4 and neoplasm: CXCL12/CXCR4 axis acts on the tumor microenvironment through the modulation of the expression and secretion of other CKs (i.e., CCL2, CXCL8) and, concomitantly, CXCR4 expression could be influenced by cytokines (TNFα, IFNγ, IL4-6-10) produced by cells in the microenvironment.