Previous studies reported that CD11b+CD11c+ myeloid cells could impair the T cell-stimulating ability by arginase-1, lysosomal protease and COX-2 [53], promote the distant metastasis via CCL2/CCR2 in colorectal cancer [54] and suppress the tumor immune microenvironment and tumor growth through CSF1R/PD-L1 upregulation [55]. Here, CCL2 is linked to colorectal cancer.