Second, in a pathophysiologic context, this G-protein–coupled receptor and its ligand stromal cell–derived factor 1 also mediate metastatic spread via various subcellular mechanisms, including paracrine stimulation of angiogenesis or migration of CXCR4-positive tumor cells to other organs with increasing stromal cell–derived factor 1 expression (17). This evidence concerns the gene CXCR4 and neoplasm.