Recently some studies have shown an association of herpes simplex virus (HSV) in human oral malignancies, and implied a link between chemical carcinogens found in tobacco and smoked tar and HSV in cancer induction. Furthermore many in vitro investigations have demonstrated the oncogenic capacity of HSV to be increased by chemical carcinogens. However, no study to date has examined the combined action of a chemical carcinogen and HSV on the oral carcinogenesis of laboratory animals. The specific aim of this proposal will be to investigate the combined action of a chemical carcinogen, 9,10-dimethyl-1,2-benzathracene (DMBA) and HSV on the development of oral cancer in hamsters. Hamster buccal pouches will be inoculated with HSV-1 or HSV-2, and a repeated topical application of DMBA on the inoculation site will be made for 15 weeks. HSV inoculation will be repeated during this period. At the end of the period, the pouches will be analyzed for the presence of infectious HSV and histopathologic changes. In order to study the effect of DMBA on the reactivation of latent HSV, a latent HSV infection will be established in the trigeminal ganglia of hamsters by primary HSV infection in buccal pouches. DMBA will then be repeatedly applied to the primary inoculation site. The presence of reactivated HSV will be determined and quantitated by swabbing of oral mucosa and homogenization of the sensory ganglia. Furthermore, we will examine the effect of DMBA on the development of oral cancer in hamsters with latent HSV infection in the trigeminal ganglia. Finally we will determine the presence of viral DNA and RNA in the developed tumor by in situ hybridization techniques. We expect to obtain significant information on the combined role of HSV and a chemical carcinogen on the development of oral cancer. Our long-term objective is to understand the mechanism of cocarcinogenic effect of HSV and to prevent it.