CCL2 and cancer: TAM-derived IL-1β, TGF-β1, CCL2, and IL-6 can (a) inhibit cytotoxic T cell infiltration into the tumor stroma, (b) suppress the cytotoxic function of T cells and NK cells, (c) induce cytotoxic T cell exhaustion, (d) promote the transformation of normal fibroblasts into tumor-promoting, cancer-associated fibroblasts (CAFs), and (e) recruit myeloid-derived suppressor cells (MDSCs) and immune-suppressive Tregs to the TME.