To investigate whether the dual blockade of CCR1 and CXCR2 has an additional effect in recruiting myeloid cells toward CRC tumors compared with the single blockade of each receptor, we generated double-knockout mice for CCR1 and CXCR2 (Ccr1−/−Cxcr2−/−) by crossing Ccr1−/− mice and Cxcr2−/− mice (Fig. 5a and Supplementary Fig. 2b). Here, CCR1 is linked to colorectal carcinoma.