In healthy tumor-free mice, cell surface expression of CXCR4 was significantly higher in chronologically aged (BrdUneg) than in non-aged (BrdUpos) blood neutrophils (figure 1D), whereas cell surface expression of L-selectin/CD62L and CXCR2 was significantly decreased (online supplemental figure S2). Here, CXCR2 is linked to neoplasm.