Cell death of human oral squamous cell carcinoma cell line induced by herpes simplex virus thymidine kinase gene and ganciclovir.

Suicide gene therapy combining herpes simplex virus thymidine kinase gene (HSVtk) and ganciclovir (GCV) is one strategy for the treatment of head and neck squamous cell carcinoma (HNSCC). The purpose of this study is to determine the mechanism of cell death that occurs in suicide gene therapy using HSVtk and GCV and to assess the safety of that therapy. The human oral squamous cell carcinoma cell line SAS was treated with adenovirus vector containing HSVtk gene (AdHSVtk) and GCV in vitro. Morphological changes including chromatin condensation, cell shrinkage, blebbing of cell membrane, and ballooning formations were observed. Changes in the localization of phospholipids in the cell membrane were also observed. The results of flow cytometry showed a maximum of about 65% of cells in the early phase of apoptosis. In addition, DNA fragmentation was investigated using the TUNEL method in vivo. Nude mice (BALB/c AJD(-nu-), aged 4 weeks) were implanted with SAS and treated with AdHSVtk and GCV. Tumor sections were then observed. The treatment group was confirmed to have DNA fragmentation-positive cells. These results suggest that suicide gene therapy using AdHSVtk and GCV led to apoptosis of the oral squamous cell carcinoma cell line.