Upregulation of CXCR4 increases chemotaxis of tumor cells towards pro-metastatic CXCL12 promoting metastasis in solid tumors, as well as tumor angiogenesis and tumor growth through the activation of the mitogen-activated protein kinase/extracellular signal-regulated kinase (MAPK/ERK) and phosphatidylinositol 3-kinase/Ak strain transforming (PI3K/AKT) signaling pathways (63, 66–68). The gene discussed is CXCL12; the disease is neoplasm.