Use of recombinant adenovirus to transfer the herpes simplex virus thymidine kinase (HSVtk) gene to thoracic neoplasms: an effective in vitro drug sensitization system.

Transfer of the herpes simplex virus thymidine kinase (HSVtk) gene into tumor cells using retroviral vectors followed by administration of ganciclovir provides a potential strategy for the treatment of malignancy. Because of the limitations of using retroviral vectors for clinical application, the feasibility of using a recombinant adenovirus containing HSVtk was examined. Cell lines derived from human malignant mesotheliomas and non-small cell lung cancers infected with a recombinant adenovirus containing HSVtk showed strong expression of HSVtk protein as determined by immunohistochemical staining. Infection with a recombinant adenovirus containing HSVtk rendered cells sensitive to doses of ganciclovir that were 2-3 logs lower than uninfected cells or those infected with a control virus. A strong "bystander effect" was noted in mesothelioma lines; there was no diminution in the efficacy of ganciclovir treatment until the ratio of infected:uninfected cells fell below 1:10. This study thus demonstrates in vitro efficacy of an adenovirus-transduced HSVtk drug sensitization gene therapy system in thoracic malignancies. Recombinant adenovirus transfer of the HSVtk gene followed by ganciclovir may have promise as an in situ treatment for tumors.