PRG4 and hepatocellular carcinoma: To identify the cell types responsible for PRG4 production in HCC, we treated ex vivo cultured surgical tumor specimens, CAFs, and five HCC cell lines with TGFβ, the TGFβRI inhibitor LY2157299 (galunisertib), or both, for 48 hours, and then analyzed the PRG4 gene transcriptional response (Fig. 2).