アルブミン遺伝子エンハンサーおよびプロモーターを制御因子とする組換えレトロウイルスを用いた肝癌に対する遺伝子治療の基礎的研究

Abstract

Recent remarkable developments in molecular biology and in vitro culture techniques have provided a promising new treatment, gene therapy, for cancer and congenital genetic diseases. For in vivo gene therapy toward cancer, it is indispensable to direct the expression of exogenous genes exclusively to cancer cells. I have constructed a recombinant retroviral vector in which a tissue-specific regulatory element is used as an internal promoter. It contains the murine albumin enhancer and promoter as an internal promoter and the lacZ gene coding bacterial β-galactosidase as a reporter between the two Moloney murine leukemia virus long terminal repeats. This vector was introduced into ecotropic retroviral ψ2 packaging cells to produce recombinant retroviral particles. Various cell lines were infected with the recombinant retrovirus to assess its tissue specificity in vitro. Expression of the lacZ gene was detected solely in hepatoma cell lines but not in fibroblasts nor in B lymphoma cells. In vivo infection was carried out to evaluate tissue specificity of this system. The recombinant retrovirus was injected into a murine subcutaneous hepatoma and expression of the lacZ gene was observed in hepatoma cells but not in surrounding connective tissues. Then the retrovirus was injected into murine livers and no expression was detected in normal hepatocytes. The retrovirus was again injected into the livers of partially hepatectomized mice, resulting in the gene expression in only a few regenerating hepatocytes. Ratio of expression of the exogenous gene was, however, much lower than that in subcutaneous hepatoma. Finally, the gene expression of higher efficiency was confirmed as the retroviral infections were repeated. These results indicate that repeated gene transfer by means of the recombinant retrovirus which contains a tissue-specific regulatory element as an internal promoter should possess high potential for selective elimination of hepatoma cells in vivo.