CCL15 and colorectal carcinoma: Regarding the gene-chemokine relationship in CRC, we have shown that the loss of SMAD4 leads to the recruitment of myeloid cells via two critical pathways: CXCL1/8-CXCR2 axis and CCL9 (mouse)- or CCL15 (human)-CCR1 axis, promoting CRC progression [7–13, 20].