MULTIPLE FACTORS IN THE ETIOLOGY OF ORAL CANCER

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Cancer of the mouth is associated with exposure to mutagens such as tobacco, alcoholic beverages, and herpes simplex virus type-1 (HSV-1). However the mechanisms of mutagenesis and the role of an individual's susceptibility to these agents is not understood. We will perform experiments with the following aims: First we will test the hypothesis that oral mutagens cause specific, targeted mutations in human cells. This will be done with shuttle vectors with small target genes that will be introduced into cultured cells. Mutation will be induced by exposing the shuttle vector to extracts of snuff, to mutagens such as are in red wine, by infecting the cells with HSV-1 or by transfecting the cells with cloned fragments of HSV-1 DNA. Combinations of agents will be tested. The mutated shuttle vectors will be recovered and mutations will be revealed by determination of their DNA sequence. This will show whether the mutations are at a consistent site within the target, or at random sites. It will show whether mutations are usually of the same type or different types. Host DNA that has been rearranged and inserted into the target will be sequenced and identified. Secondly, we will test the hypothesis that patients with oral cancer are more susceptible to oral mutagens than control subjects. Lymphocytes will be obtained from patients with oral cancer an control subjects and will be transformed to lymnphoblastoid cell lines. They will be transfected with a mutagenesis shuttle vector and be exposed to the oral mutagens either singly or in combinations. The frequency and types of mutations in cell from patients will be compared with those from matched control subjects. This will show whether cells from patients with oral cancer are particularly susceptible to one or all of the oral mutagens. It will show whether the mutagens produce different types of mutation in cells form patients as compared with controls. Thirdly, we will determine which oral mutagens, alone or in combination, can transform cells to a malignant phenotype. Specific oral mutagens will be tested for their ability to transform cells. Hamster embryo fibroblasts will be exposed to the mutagenic agents and specific combinations of agents. The numbers of transformed foci will be counted and the transformed cells will be tested for tumorigenicity by inoculation into hamsters. This will show which of the oral mutagens are likely to be tumorigenic either alone or in combination with other agents.