CCL2 and neoplasm: Numerous immune cells (i.e., hepatic macrophages, dendritic cells, neutrophils, and natural killer cells) and inflammatory cytokines (i.e., TNF-α, IFN-γ, CCL2, and CCL5) constitute the inflammatory microenvironment of the liver and jointly motivate tumor immune evasion, tumor progression, and metastasis (49, 50).