The long-term objective of this application is to elucidate the cellular and molecular mechanisms by which transforming growth factor-alpha (TGF- alpha) and its receptor, epidermal growth factor receptor (EGFR), can influence the malignant transformation of human oral mucosal tissues. This renewal application aims to extend the findings of the previous funding period to detail the cellular forms and bioactivity of the TGF- alpha expressed by human eosinophils and oral keratinocytes. TGF-alpha is a growth factor/cytokine-peptide molecule which can be expressed as soluble and/or membrane-anchored forms. During the current funding period, our laboratory has made the novel observations that oral cancer- associated human eosinophils can express TGF-alpha and that human malignant oral keratinocytes express higher levels of TGF-alpha than the normal counterpart. In this continuation application, we hypothesize that the infiltrating eosinophils and malignant oral keratinocytes express both the soluble as well as the membrane anchored forms of TGF-alpha. We further propose that both of these cellular forms are biologically active, and there are differences in the biosynthesis of TGF-alpha by the normal versus malignant human oral keratinocytes. We will perform detailed studies to elucidate the biosynthesis, cellula forms, as well as the biological activities of the TGF-alpha expressed by the eosinophils, normal and malignant human oral keratinocytes. Because normal peripheral blood eosinophils do not express TGF-alpha, a panel of eosinophil-specific cytokines will be examined to determine their ability to activate TGF- alpha expression by these granulocytes. These studies should provide important mechanistic insights into how eosinophils and malignant oral keratinocytes can influence the malignant transformation of human oral keratinocytes via the TGF-alpha/EGFR pathway. The proposed work is based on a body of data derived from our laboratory, and will employ experimental approaches already established in the laboratories of the applicants. Thus, the work has a high likelihood of success in providing new information to elucidate the potential significance of the eosinophil and oral keratinocyte in the production of TGF-alpha in the microenvironment of developing human oral cancer.
