Oral cancer represents up to 5% of all malignant tumors in the Western Hemisphere, but the process by which oral epithelial cells become invasive has not been studied in detail. Recent data obtained in other epithelial malignancies suggests an important role for stromal cells in modulating keratinocyte invasion, but the role of stromal cells in oral cancer is not understood. Specifically, the role of proteinases secreted by epithelial cells and their regulation by stromal cell factors has not yet been elucidated. In addition, several studies have determined that human papillomavirus DNA can be detected in a large subset of oral cancers. However, the role that HPV plays in the pathogenesis of these tumors is not understood, and little is known of biological differences between HPV-positive and HPV-negative oral cancers. This is a three- phase study. In the first phase, the expression of proteinases (MMP-2, MMP-3, MMP-9 and urokinase plasminogen activator) at the mRNA and protein levels will be characterized in archival oral tissue specimens ranging from benign to invasive cancer. It will be determined if HPV DNA is present in the tissues, and if the two known oncogenes, E6 and E7, are being expressed. Based on these results, in the second phase, oral cancer tissues collected in a prospective manner, along with accompanying clinical data, will be studied to determine the prognostic significance of proteinase and HPV gene expression. In the third phase, an in vitro invasion model and a nude mouse tumor model will be used to study mechanisms of interaction between epithelial and stromal cells in modulating invasion by oral keratinocytes. The role of epithelial and stromal interactions in vitro will be studied by incorporating oral fibroblasts, derived from normal oral tissue or oral cancer tissue, into the Matrigel invasion model. Proteinase and growth factor expression by keratinocytes and fibroblasts will be characterized. Modulation of proteinase expression in different keratinocyte cell lines by different growth factors will be measured. Then proteinase and growth factor expression in nude mouse tumors induced by the HSC3 oral cancer cell line will be characterized. Mouse fibroblast lines from normal and cancerous tissues as described above will be established and studied for their ability to modulate invasion of the tumor cells in the Matrigel model. Factors of interest will be transfected into oral keratinocyte cell lines that have been shown to be nontumorigenic in this model. The transfected cells will then be studied in the nude mouse, as well as in the Matrigel in model, to determine if expression has altered their invasive capability and tumorigenicity. Together, it is expected that the data generated by these studies will provide important new information on the mechanism of interaction between epithelial and stromal cells in the pathogenesis of oral cancer, as well as provide information on the prognostic value of detection of factors mediating these interactions. Ultimately it is expected that this information will be of value in prevention and/or treatment of this disease.
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