CXCR4 and neoplasm: The direct effect of CXCL12/CXCR4 in tumor metastasis is that CXCL12 increases CXCR4-mediated motility, and the cell surface expression of integrins is mediated by the phosphorylation of extracellular signal regulated kinase (ERK) and downstream activation of the IKKαβ/NFκβ/RELA signaling (18).