CCR2 and neoplasm: HDAC5 inhibits suppressor of cytokine signaling 3 (SOCS3), which leads to an increase of C-C motif chemokine ligand 2 (CCL2), recruits CCR2+ macrophages, promotes macrophages to reaggregate into tumor microenvironments, and promotes tumor recurrence (Cheng et al., 2014a; Hou et al., 2020).