ACKR3 and neoplasm: On the other hand, MTLn3 CXCR7 tumors showed significantly increased tumor size compared with the control MTLn3 JP tumors (P < 0.05), and similarly the MTLn3 CXCR4-CXCR7 double overexpressors were significantly bigger than either MTLn3 JP or MTLn3 CXCR4 tumors (P < 0.05); indicating that CXCR7 but not CXCR4 plays a role in enhancing tumor growth.