Cell lines are useful as models if they retain the relevant characteristics of the tissue of origin. We compared two human squamous carcinoma cell lines derived from tumors of the tongue that vary in their extent of differentiation, with human biopsies of carcinomas of the tongue that were either poorly or well-differentiated. The mRNA levels of suprabasal cell proteins (keratin K13, involucrin, transglutaminase) and of protein kinase C (PKC) isozymes were measured by RT-PCR. Apart from PKC beta and PKC delta (mostly expressed by Langerhans cells and missing in culture), qualitatively similar patterns were found in vitro and in vivo. The more differentiated cells had expression levels moderately lower to higher than the normal controls. The poorly differentiated cells generally had substantially lower levels.