CXCL12 and nasopharyngeal carcinoma: The immunohistochemical method revealed high expression of α-SMA fibroblasts in NPC stroma, together with increased intensities of the chemokine stroma-derived factor-1 (SDF-1, also known as CXCL12), a mediator of the recruitment of endothelial progenitor cells, and its receptor CXCR4 in NPC cells.