CCL4 and mesothelioma: Mesothelioma cells attract monocytes in the TME though releasing some chemokines, such as chemokine (C-C motif) ligand 2 (CCL2), chemokine (C-C motif) ligand 4 (CCL4), chemokine (C-C motif) ligand 5, and C-X-C motif chemokine ligand 12 (CXCL12).