The targeted expression of the human interleukin-2/interferon alpha 2b fused gene in alpha-fetoprotein-expressing hepatocellular carcinoma cells

This study explores the use of a liver-specific albumin promoter and a tumo r-specific a-fetoprotein (AFP) enhancer to achieve the regulated expression of the cytokine interleukin-2/interferon alpha 2b (IL-2/IFN alpha 2b) fuse d gene for treatment of hepatocellular carcinoma (HCC). The human AFP enhan cer (E-AFP) and albumin promoter (P-ALB) were amplified from human chromoso me DNA by the polymerase chain reaction. A re recombinant retrovirus was co nstructed including, as a selectable marker, the neo(R) gene and the IL-2/I FN alpha 2b fused gene controlled by E-AFP-P-ALB. The liver-targeted expres sion pattern of the IL-2/IFN alpha 2b fused gene was observed when this pro duct was tested in the culture medium of the infected cells (IL-2 activity was 850 IU/10(6) cells, IFN alpha activity was 320 IU/10(6) cells). Moreove r, The growth of the IL-2/IFN alpha 2b-fused-gene-infected HCC cells, SMMC7 721, was clearly suppressed by the second week after innoculation of nude m ice 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 s equences of E-AFP-P-ALB could control the targeted expression of cytokine g enes in AFP-positive human HCC cells, and the expression level of the IL-2/ IFN alpha 2b fused gene was positively correlated to the level of AFP expre ssion in the infected cells. The IL-2/IFNa2b fused protein that was express ed has the functions of both IL-2 and IFN alpha. Therefore, this study illu strates the superiority of using transcriptionally targeted recombinant ret rovirus vectors in cytokine-based gene therapy.