Experiments conducted with mouse models of breast cancer and samples from patients with cancer have indicated that cytokines including C-C motif chemokine ligand 2 (CCL2), interleukin-6 (IL-6), chemokine (C-X-C motif) ligand 1 (CXCL1), and granulocyte-macrophage colony-stimulating factor (GM-CSF) interact with cancer-derived exosomes in the TME by binding to the glycosaminoglycan side chains of their proteoglycans. This evidence concerns the gene CXCL1 and breast cancer.