Gene Transfer of Herpes Simplex Virus Type I Thymidine Kinase Gene as a Drug Sensitivity Gene into Human Lung Cancer Cell Lines using Retroviral Vectors

One of the recent strategies for gene therapy as a cancer control is the targeted introduction of a drug-sensitivity gene into tumor cells. We investigated the gene transfer of herpes simplex virus type I thymidine kinase (HSV-TK) gene as a drug-sensitivity gene into human lung cancer cell lines. We used a recombinant retroviral vector derived from Moloney murine leukemia virus (MuLV) as one of potential vectors for gene therapy. The amphotropic retroviral vector consisted of the HSV-TK gene and the neomycin-resistant gene under Rous sarcoma virus (RSV) promoter control. The antiherpes drugs, acyclovir (ACV) and ganciclovir (GCV), were chosen for testing the activity of HSV-TK that was transferred into human lung cancer cell lines. ACV and GCV are nucleoside analogs specifically converted by HSV-TK to a toxic form capable of inhibiting DNA synthesis. The cytotoxicity was determined by using a tetrazolium-based colorimetric assay (MTT assay). The results obtained from our experiments demonstrated that the retroviral vector-mediated HSV-TK gene transfer leads to ACV- and GCV-dependent cytotoxicity in human lung cancer cell lines, which were both small cell carcinoma and non-small cell carcinoma established from human specimens. These findings suggest that the gene transfer of HSV-TK gene into tumor cells would be one of the models for the use of gene therapy to control lung cancer.