This study was undertaken to analyze
keratin gene expression at both the
mRNA and
protein level in
oral hairy leukoplakia (OHL). Comparisons were made with normal lingual epithelium from a similar site, tongue biting, normal buccal mucosa and another condition which disturbs oral epithelial differentiation, white sponge
nevus. Combined immunocytochemical and in situ hybridization studies for
keratins 14 and 19 were carried out on 2 specimens of OHL from HIV-positive males and one sample each of the other cases.
Keratin 14 protein expression was uniform throughout all the epithelia. In normal epithelia and in lesions other than OHL,
keratin 14 mRNA was most strongly expressed in basal cells with weaker but still significant amounts in the spinous cell layer. In both cases of OHL there was weaker basal cell expression of
keratin 14 mRNA and frequent absence in koilocytoid cells.
Keratin 19 protein expression was heterogeneous in the basal layer of all specimens with suprabasal staining of occasional groups of cells. Its
mRNA was uniformly distributed in all cases. The findings indicate the
keratin mRNA expression does not always parallel that of
protein and that, in the case of
keratin 14, expression may be influenced by the presence of EBV.