CXCR4 and neoplasm: Moreover, in several well-controlled animal experimental models, it has been demonstrated that blockade of CXCR4 [4,33,34], CXCR7 [35], or c-Met [4,36] receptors by employing small-molecule inhibitors; downregulation of these receptors by shRNA strategies [27,37]; in vivo administration of blocking antibodies against SDF-1 [38] or MCP-1 [39,40]; or application of S1P-binding aptamers [6] significantly diminishes chemotherapy- or radiotherapy-related dissemination of tumor cells to various organs.