Several studies were conducted to evaluate the role of chemopreventatives during oral carcinogenesis in the hamster buccal pouch tumor model. Tissue sections and cells which were treated in vivo were analyzed using immunohistochemistry, flow cytometry, and Western immunoblotting. Treatment with the carotenoid, beta-carotene was administered to the hamsters producing fewer and smaller oral squamous cell carcinomas. The histopathology sections showed fewer areas of dysplasia and less invasive oral carcinomas once they did form. Results showed that nucleosome formation persisted from early to late carcinogenesis following treatment with beta-carotene. Levels of Bcl-2 expression in contrast was not elevated during carcinogenesis with chemopreventative treatment. Stress proteins(70, 90) were increased very early during carcinogenesis while p53 was reduced in expression. Cell cycle was altered with the majority of the cells in G1, and showing less expression of PCNA. Treatment with either vitamin E or reduced glutathione also produced similar results. Transforming growth factor alpha and epidermal growth factor receptor expression was also noted to be reduced in staining while transforming growth factor beta was seen to be increased. Neovascularization was also apparently reduced as distinguished by fewer factor VIII antigen endothelial vascular spaces observed. These studies indicated that chemopreventative agents inhibited oral carcinogenesis by inducing programmed cell death, reducing growth factor expression, and inhibiting the development of angiogenesis. These results could lead to the development of new markers for early neoplasia identification in clinical tissues.
