A novel approach for inducing enhanced and selective transgene expression in hepatocellular-carcinoma cells

Utility of the alpha-fetoprotein (afp) promoter for gene therapy against he patocellular carcinoma (HCC) is limited because of the weak promoter activi ty. To circumvent this, the 5.1-kb 5'-flanking sequence of the human afp ge ne including the entire enhancer and silencer regions as well as the promot er region was employed for achieving strong, HCC-selective transgene expres sion. To thoroughly inhibit the promoter activity of the 5'-flanking sequen ce of the human afp gene, the afp 5'-flanking region was inserted downstrea m of the human interleukin-2 (il-2) gene controlled by the simian-virus-40 (SV40) early promoter, il-2-production ability of HCC cells transduced with the construct was significantly enhanced compared with that transduced wit h the same construct lacking the afp 5'-flanking region, Importantly, il-2 production of non-HCC cells was substantially inhibited by the addition of the afp 5'-flanking region to the construct, When the afp 5'-flanking regio n was inserted downstream of the human tumor-necrosis-factor-alpha (tnf-alp ha) gene controlled by the retrovirus long-terminal-repeat (LTR) enhancer/p romoter, tnf-alpha production ability of HCC cells was significantly enhanc ed and that of non-HCC cells was significantly suppressed compared with tha t transduced with the same construct lacking the afp 5'-flanking region. Ou r results indicated that the afp 5'-flanking region gave the enhanced HCC-s elective activity to the non-tissue specific SV40 early promoter and LTR en hancer/promoter. It is essential for successful gene therapy to induce stro ng, target-cell-selective transgene expression. This novel strategy, theref ore, may contribute to the establishment of HCC-selective cancer gene thera py, Int. J. Cancer 87:247-252, 2000. (C) 2000 Wiley-Liss, Inc.