C-X-C motif chemokine ligand 1 (CXCL1) is the chemokine that TAMs secrete most abundantly [19], and TAMs/CXCL1 signaling has been demonstrated to aggravate breast cancer progression by enhancing the epithelial-mesenchymal transition and pre-metastatic niche formation [20]. Here, CXCL1 is linked to breast cancer.