STAT3 and hepatocellular carcinoma: Cheng et al. [184] treated HCC cells with melatonin and detected that the secreted ExVs downregulated the expression of PD-L1 on macrophages and attenuated the expression of IL-6, IL-10, IL-1β and TNF-α so reducing the activation of STAT3, whereas control ExVs derived from untreated HCC cells upregulated the secretion of these inflammatory cytokines in macrophages.