CTLA4 and hepatocellular carcinoma: HSC-derived exosomal WD repeat domain 25 circRNA (circWDR25) were shown to increase the expression of cytotoxic T lymphocyte-associated protein 4 (CTLA-4) in HSCs and PD-L1 in HCC cells via the circWDR25/miR-4474-3p/arachidonic acid 15-lipoxygenase (ALOX15) and epithelial–mesenchymal transition (EMT) axis.