AIM: To study the effects of sense and antisense KAI1genes on the growth and invasion of human hepatocellularcarcinoma (HCC) cell line MHCC97-H.METHODS: KAI1 sense and antisense eukaryotic expression plasmids were constructed using subclone technique and transfected into MHCC97-H cells respectively by DOTAP liposome. After successful transfection was confirmed,in vitro growth curve, cell cycles, plate clone formation efficiency, invasive ability in Boyden Chamber assay and ultrastructural morphology were studied.RESULTS: KAI1 sense and antisense genes had no significant effects on the cell growth curve and cell cycles.After transfection with sense KAI1 gene, decreased invasive ability in Boyden Chamber assay and decreased amount of mitochondria, but no significant changes of plate clone formation efficiency were observed in MHCC97-H-S cells.The plate clone formation efficiency and invasive ability in Boyden Chamber assay were significantly increased in MHCC97-H-AS cells, after transfection with antisense KAI1 gene. Furthermore, increased amount of mitochondria,rough endoplasmic reticulum, Golgi apparatus and expanded endoplasmic reticulum were also noted in MHCC97-H-AS cells.CONCLUSION: Changes of KAI1 expression in HCC cells may alter their invasive and metastasis ability of the tumor.