AIM:To elucidate the role of Rab23 in hepatocellular carcinoma(HCC)by assessing the expression of Rab23 in HCC tissue and in HCC cell lines.METHODS:Primary tumors(n = 100)were stained with Rab23 antibodies using immunohistochemistry and in situ hybridization in tissue microarrays.Relationships between gene expression and pathology parameters were analysed.The biological significance of Rab23 in Hep-3B cells was examined by knocking down Rab23 gene expression.We designed a pair of doublestranded RNAs against human rab23 and transfected siRNA into Hep-3B cells.Rab23 expression in these cells was examined using RT-PCR and Western blots.We investigated cell growth by MTT assays and fluorescenceactivated cell sorting.RESULTS:High cytoplasmic and nuclear expression of Rab23 was found in 38 of 71(53.5%)and in 49 of 68 HCC patients(72%)respectively,which correlated with tumor size.HCC cell lines expressed Rab23.In Hep3B cells,siRNA for Rab23 decreased Rab23 mRNA by 4.5-fold and protein expression by 2-fold.Survival rates at 24 and 48 h for Hep-3B cells transfected with siRNA were lower and about 30% Hep-3B cells were apoptotic.Knocking down rab23 suppressed Hep3B cell growth,suggesting that rab23 could play an important role in Hep3B cell growth.CONCLUSION:Rab23 is overexpressed and/or activated in HCC.Rab23 may be both a HCC predictor and a target for treating HCC.