CELL DIFFERENTIATION, GROWTH, AND APOPTOSIS IN ORAL CARCINOGENESIS

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Cancers of the oral cavity account for about 4% of new cancer cases and for 2% of deaths from cancer. The overall survival rate (50%) among these patients has remained unchanged for the last three decades. Clearly, there is an urgent need to develop approaches to the prevention and therapy of oral cancer. One of the strategies to suppress oral carcinogenesis is to use biologic agents that modulate cell growth and differentiation. Such agents include vitamin A analogs (retinoids) and sodium butyrate and its derivatives. Retinoids modulate the proliferation and differentiation of normal oral mucosa cells and some head and neck squamous cell carcinoma cells and may play important regulatory roles in oral cancer development and growth. Butyrate is a known modulator of cellular differentiation and can enhance squamous cell differentiation of epidermal keratinocytes, however, the potential of butyrate or its derivatives in prevention or treatment of oral cancer has not been investigated. The progress of research on oral carcinogenesis is hindered by the methods employed to investigate the modulation of cell growth and differentiation of normal, premalignant, and malignant oral cells. Most of the current systems rely on cell lines established from oral cancer in monolayer culture. The culturing of normal cells is quite complicated, and there are no successful methods for culturing genuine premalignant oral cells. Here we propose to use a unique tissue slice organ culture (TSOC) method to investigate the effects of retinoids and butyrate derivatives on normal, premalignant, and malignant oral tissue. The Objectives of this project are to establish the TSOC system for oral normal, premalignant, and malignant tissues and to identify and characterize biological agents that reverse abnormalities in cell proliferation and differentiation and induce apoptosis. The Hypotheses to be tested in this project are: A. Short-term organ culture of slices of oral premalignant and malignant tissues can provide a unique system to investigate effects of various agents on cell growth, apoptosis, and differentiation under conditions that preserve tissue organization, cellular interactions, and cell function and, therefore, resemble the in vivo conditions better than monolayer cell culture. B. Retinoids and butyrate derivatives alone or in combination can reverse aberrations in cell growth and differentiation and induce apoptosis in premalignant and malignant oral cancer. To test these hypotheses we will establish optimal conditions for short-term organ cultures of tissue slices of fresh human oral squamous cell carcinoma and adjacent dysplastic and normal tissue and investigate the effects of several retinoids, which exhibit nuclear receptor specificity, and butyrate and its derivative, and the combination of these agents on the expression of nuclear retinoid receptors, cell proliferation, differentiation, and apoptosis in short-term cultures of tissue slices. Such agent could be used alone or in combination with existing approaches and add new therapeutic approaches to the prevention and therapy of oral cancer.