CXCL12 and gastric cancer: Factors like SDF-1 (stromal derived factor-1), HGF (hepatocyte growth factor/scatter factor), VEGF (vascular/endothelial growth factor) secreted by stromal cells or tumor-associated macrophages (TAM) attract GC cells through the CXCR4, CXCR7, c-Met and KDR receptors [10,11].