Though the function of CXCR2 in tumor progression has been widely investigated and reported to participate in angiogenesis [48], chemo-resistance [49], EMT [49] and anti-PD1 treatment efficiencyb [19], the precise function and mechanism of CXCR2 in tumor metastasis to lung or lymph node of CXCR2+ MDSCs need to be further investigation. This evidence concerns the gene PDCD1 and neoplasm.