CXCR2 and cancer: In line with these results, the elevation in the expression of CXCR4 on circulating neutrophils in tumor-bearing mice was substantially reduced on blockade of the aging-promoting chemokine receptor CXCR2, collectively suggesting that CXCR2 ligands released by malignant tumors uncouple biological from chronological aging of neutrophils in the systemic circulation by promoting excessive biological aging of these immune cells.