CCL2 and breast cancer: These CAFs promote tumor growth, invasion, metastasis and resistance to chemotherapeutics of breast cancer cells by secreting factors including CC-chemokine-ligand 2 (CCL2), C-X-C motif ligand 1–3 (CXCL1–3), and IL6, stiffening the ECM, affecting cancer cell metabolism [17], interacting with and influencing the functions of diverse stromal cells, such as MSCs, endothelial, and immune cells [16].