CD33 and cancer: Consistent with the results in tumor mouse models, the expression of CCL20 was positively correlated with the expression of CD33 (a MDSC marker in human, p value = 1.2e-15, R = 0.24) but not CD68 (a pan-macrophage marker in human, p value = 0.011, R = 0.077) in patients’ breast tumors from GEPIA2 database (Supplementary Fig. S5), indicating that CCL20 overexpression facilitated cancer cells to create a tolerogenic environment.