ObjectiveTo investigate the possible effect of mouse intrahepatic biliary epithelial cell line (mIBEC) on cocultured human hepatoma cell lines HepG2.MethodsHepG2 and mIBEC cells were cocultured in a membraneseparated Transwell system. CellTiter 96R○ AQueous One Solution Cell Proliferation Assay (Promega Corporation,Madison,WI) was used to examine HepG2 cell proliferation in the system with or without cocultured mIBEC. Realtime PCR(RTPCR)was used to determine Ki67 and caspase3 mRNA expression in HepG2 cells in a system with or without cocultured mIBEC. Western blotting analysis was used to determine caspase3 protein level in HepG2 cells. ResultsThe proliferation of the cocultured HepG2 cells was significantly lower than those cultured alone(P<0.01). Expression of Ki67,a cell proliferation marker,was also significantly downregulated in mIBEC cocultured HepG2 cells (P<0.05). The levels of caspase3 mRNA and protein were significantly upregulated in mIBEC cocultured HepG2 cells compared with HepG2 cells cultured alone (P<0.05). ConclusionmIBEC can inhibit the proliferation of cocultured HepG2, and caspase3 activation might be one of the reasons for the inhibitory effect of mIBEC against HepG2 cells.