CCL2 and hepatocellular carcinoma: The TME causes the overexpression of dynamin-related protein 1 (Drp1) in the HCC cells, which stimulates mitochondrial fission and induces cytoplasmic mitochondrial DNA (mtDNA) stress, activating the TLR9-mediated NF-κB signaling pathway and promoting the nuclear translocation of phosphorylated P65, thereby promoting the secretion of chemokine CCL2 (Bao et al., 2019).