Compared with the neutrophils from naive mice, the neutrophils from cir-B16F0-mice expressed higher levels of genes that are related to tumor-promoting function of neutrophils, including Mmp9, Bv8, Arg1 and Nos2 (Figure 4A and Supplementary Figure 4), suggesting that CTCs could alter the expression of these genes to augment the tumor-promoting function of neutrophils. This evidence concerns the gene PROK2 and neoplasm.