Assessment of Keratin Expression and Xenobiotic Metabolism in Cultured Normal and Transformed Human Oral Keratinocytes

Abstract

Normal (NOK), immortalized (SVpgC2a) and malignant (SqCC/Yl) human buccal keratinocytes were cultured in efforts to model oral epithelium in vitro, and further, to investigate keratin expression and metabolism related to cytochrome P450 (CYP). Organotypic epithelia were successfully derived from 10 days of culture at the air-liquid interface of collagen gels containing human oral fibroblasts using a standardized serum-free medium termed EMHA. The respective epithelia showed sharp differences in immunochemical expression of keratins, including those considered as being basal cell-specific or serving as markers of activated growth or early signs of terminal squamous differentiation (TSD). RT-PCR-based analysis of the oral keratinocyte lines demonstrated expression of mRNAs for all or a majority of the xenobiotic-metabolizing CYPs expressed in oral tissue. Active metabolism of several CYP substrates indicated that primarily NOK and SVpgC2a were also metabolically competent. Overall, the results demonstrated that various keratinocyte lines can serve in modeling of oral epithelium including the malignant process. NOK expressed many of the same keratins as normal tissue including those associated to TSD, whereas the loss of keratins in SVpgC2a and their retention in SqCC/Y1 showed similarities to the respective keratin profile of oral epithelial dysplasia and well-differentiated oral squamous cell carcinoma. Preserved and even activated ability for xenobiotic metabolism in long-term cultures of SVpgC2a indicated that this cell line may serve in development and safety assessment of consumer products, especially those related to oral health care.