CXCR4 and neoplasm: 2The mechanism of antipain effect of APC is closely related to reduce the expression of VEGF protein, CXCL12, and its receptor CXCR4 in tumor tissues; reduce NO content in the hypothalamus, pituitary, and lumbar spinal cord; increase β-endorphin (β-EP) in peripheral blood and decrease 5-hydroxytryptamine (5-HT) and prostaglandin E2 (PGE2) in serum; inhibit cyclo-oxygenase (COX) activity, spinal necrosis factor (TNF)-α), and IL-1 expression; and reduce c-fos and SP release [72].