Abstract
This study explores the use of a liver-specific albumin promoter and a tumor-specific alpha-fetoprotein (AFP) enhancer to achieve the regulated expression of the cytokine interleukin-2/interferon alpha2b (IL-2/IFNalpha2b) fused gene for treatment of hepatocellular carcinoma (HCC). The human AFP enhancer (E(AFP)) and albumin promoter (P(ALB)) were amplified from human chromosome DNA by the polymerase chain reaction. A recombinant retrovirus was constructed including, as a selectable marker, the neoR gene and the IL-2/IFNalpha2b fused gene controlled by E(AFP)-P(ALB). The liver-targeted expression pattern of the IL-2/IFNalpha2b fused gene was observed when this product was tested in the culture medium of the infected cells (IL-2 activity was 850 IU/10(6) cells, IFNalpha activity was 320 IU/10(6) cells). Moreover, The growth of the IL-2/IFNalpha2b-fused-gene-infected HCC cells, SMMC7721, was clearly suppressed by the second week after innoculation of nude mice compared to the control SMMC7721 cells infected with LXSN and untreated SMMC7721 cells (0.5 +/- 0.1 cm versus 1.4 +/- 0.2 cm and 1.6 +/- 0.2 cm, P < 0.05). The results showed that the combined transcriptional regulatory sequences of E(AFP)-P(ALB) could control the targeted expression of cytokine genes in AFP-positive human HCC cells, and the expression level of the IL-2/IFNalpha2b fused gene was positively correlated to the level of AFP expression in the infected cells. The IL-2/IFNalpha2b fused protein that was expressed has the functions of both IL-2 and IFNalpha. Therefore, this study illustrates the superiority of using transcriptionally targeted recombinant retrovirus vectors in cytokine-based gene therapy.