Keratin 14 and 19 expression in normal, dysplastic and malignant oral epithelia: A study using in situ hybridization and immunohistochemistry

Specific mRNA and protein for two major keratins, K14 and K19, were investigated in normal, dysplastic and malignant oral epithelia by combined in situ hybridization and immunohistochemistry. In normal epithelia. K14 mRNA and protein were present almost exclusively in the basal layer of non-cornified, and in rete-processes of cornified, sites. Dysplastic epithelium showed irregular extension of the K14 transcript and protein into superficial cells. In squamous cell carcinoma (SCC), K14 transcript was abundant in most samples whilst in one poorly differentiated carcinoma mRNA but no protein was detected. K19 mRNA and its protein were present predominantly in basal cells of noncornified epithelium, whereas in cornified epithelium only mRNA was detected. In dysplasias, K19 transcript was detected in all specimens but its protein was absent in most cases. Even more variations of K19 expression were observed in SSC. These findings indicate differences in the control of expression of K14 and K19 in normal epithelia and show that regulation is further disturbed during dysplastic change and malignancy.