SQUAMOUS-CELL DIFFERENTIATION MARKERS IN NORMAL, PREMALIGNANT, AND MALIGNANT EPITHELIUM - EFFECTS OF RETINOIDS

Vitamin A and some of its analogs (retinoids) maintain normal differen tiation of epithelial tissues by preventing aberrant squamous differen tiation of cells in nonkeratinizing epithelia. They can also reverse s quamous metaplasia, which develops in vivo during vitamin A deficiency . These effects are the result of the ability of retinoids to suppress the expression of genes associated with squamous differentiation (e.g ., transglutaminase type I, loricrin, involucrin, filaggrin, and kerat in K1). In addition, retinoids reverse keratinizing premalignant lesio ns in the oral cavity, and inhibit the growth and squamous differentia tion of head and neck squamous cell carcinomas (HNSCCs) in vitro. Nucl ear retinoic acid receptors, which function as DNA-binding, trans-acti ng, transcription-modulating factors, are considered to be the proxima te mediators of the effects of retinoids on gene expression and may me diate the re-regulation of aberrant differentiation and growth of prem alignant and some malignant cells, thereby suppressing the development of head and neck cancer. (C) 1993 Wiley-Liss, Inc.