ACKR3 and metastatic malignant neoplasm: The expression of CXCL12, CXCR4 and CXCR7 is elevated in CRC and tissue samples from lung metastasis, while the expression of both CXCL12 and CXCR7 is significantly higher in tissue samples derived from metastatic cancer in comparison to primary lesions [47,50].