Retroviral vector pLXSN was employed to introduce human r-Interferon (IFN-?) gene into four human hepa-tocellular carcinoma cell lines (HCC). The G418-resistant colonies were isolated and cloned. PCR and RT-PCR analysis indicated that the integration and expression of IFN-? gene was shown only in the transduced cells. Using a bioassay method, we found that all genetically modified HCC cells can secrete varied amount of IFN-?. The results of flow cytome-try showed that the cell surface expression of HLA class I molecules significandy increased following transduction. Moreover , we firsdy indicated that the increase in the expression of one specific HLA class I antigen, HLA-A2, was almost in the same magnitude as that of the total HLA class I molecules after transduction with IFN-r gene.