PRG4 and hepatocellular carcinoma: To validate the in vivo findings in a less complex 2D HCC cell growth model, cell proliferation assays were performed using the same HCC cell lines used in in vivo experiments (HLC19 EV/PV), and an additional HCC cell line, HLF engineered in the same way (HLF EV/PV) to assess PRG4 + regorafenib synergism.