In contrast to CXCR7 knocked-down tumors, sh-CXCR4 tumors grew less than control tumors (Fig. 3a), in accordance with the significant reduction in the percentage of proliferating tumor cells observed in the CXCR4-deficient tumors (Supplementary Fig. 3G and 3H). Here, CXCR4 is linked to neoplasm.