Differential expression of cytokeratin mRNA in hamster squamous epithelia as observed by in situ hybridization using human cytokeratin cRNA probes.

In this hybridohistochemical study, we investigated the expression of cytokeratin (CK) mRNA in the keratinizing squamous epithelium of hamster cheek pouch and esophagus, using eight different digoxigenin-labelled RNA probes complementary to human CK mRNAs. CK 4, CK 6, CK 8, CK 14, and CK 15 RNA probe obviously hybridized with hamster counterpart mRNA(s) in the cheek pouch as well as in the esophageal epithelium. However, using the CK 10-specific RNA probe, only the cheek pouch epithelium exhibited a positive reaction. We were not able to detect any positive signal for the CK 18 or for the CK 19 RNA probe. We observed three different CK mRNA distribution patterns in the cheek pouch epithelium, and four in the esophageal epithelium. The differences in expression and distribution pattern of CK mRNAs between the two types of epithelia suggest that the hamster CK polypeptide family comprises at least six different species. We also conclude that human cRNA probes for CK mRNAs may provide a way to detect changes in CK expression and distribution during induced non-neoplastic and neoplastic changes in the hamster cheek pouch model. This may also help to elucidate the molecular pathogenesis of squamous-cell carcinoma.