CCL21 and colorectal cancer: In addition, the levels of DC-associated cytokine CCL21 and B cell-associated cytokine CXCL12 were upregulated in the tumor diameter ≥3 cm group (Student’s t-test, CCL21, p = 0.0471; CXCL12, p = 0.0432), suggesting that as the primary colorectal cancer lesion grows, the tumor secretes more cytokines, such as CCL21 and CXCL12, into the peripheral blood to recruit APCs (Figure 6G).