CX3CR1 and neoplasm: However, a significant difference in CX3CR1 expression in intratumour Mo-MDSCs between WT and p16/p21-DKO was not observed (Fig. 3c, d), although the number of intratumoural Mo-MDSCs in p16/p21-DKO mice was much smaller compared to WT mice, suggesting that CX3CR1 highly expressing Mo-MDSCs are concentrated in tumour site, regardless of the p16Ink4a and p21Cip1/Waf1 gene status.