CCR4 knockout had a significant effect on tumor immune cell infiltration (CCR4−/−: 9341 ± 1777 CD45+ cells per 1 × 105 tumor cells vs. WT: 17,860 ± 2462 CD45+ cells per 1 × 105 tumor cells; n = 9, p = 0.0127). Here, CCR4 is linked to neoplasm.