TRANSDUCTION OF NORMAL AND MALIGNANT ORAL EPITHELIUM BY AN ADENOVIRUSVECTOR - THE EFFECT OF DOSE AND TREATMENT TIME ON TRANSDUCTION EFFICIENCY AND TISSUE PENETRATION

We tested an adenovirus vector that carries a P-D-galactosidase marker gene for its ability to transduce normal oral mucosa and oral carcino ma cells. Topical application of adenovirus to normal oral mucosa of m ice at 1 x 10(10) plaque-forming units (pfu)/mL for 1 minute did not r esult in transduction of epithelial cells. Similarly, topical applicat ion to human oral mucosa ex vivo was not successful. However, systemic administration by intracardiac injection of hamsters did transduce no rmal oral mucosa effectively. To evaluate transduction of carcinomas, the Tu138 human oral cancer cell line was used. A single application o f virus at 1 x 10(8) pfu/ml in vitro resulted in 30% of oral carcinoma cells expressing the marker gene, and 2 x 10(8) pfu/ml transduced 60% of cells. After two applications of virus at 2 x 10(8) pfu/ml with an interval of 18 hours, 100% of oral carcinoma cells expressed the mark er gene. Topical application to a raft culture of Tu138 cells for 1 ho ur produced gene expression that penetrated up to four layers of cells . To emulate the effect of treating a carcinoma, Tu138 cells were impl anted subcutaneously in nude mice, allowed to grow to a tumor 1 cm in diameter, and then injected directly with virus. This produced diffuse transduction of around 30% of cells in the tumor, and expression was seen in cells at a significant distance from the injection site. Adeno virus vectors are therefore capable of transferring novel genetic info rmation to both normal and malignant oral mucosa. They may have potent ial for use in gene therapy in the prevention or treatment of oral squ amous carcinomas.