Cytokeratins 6 and 16 are Frequently Expressed in Head and Neck Squamous Cell Carcinoma Cell Lines and Fresh Biopsies

Abstract

Background: Cytokeratins (CK) are members of intermediate filaments, which are predominantly found in epithelial cells. Different types of epithelia are characterized by a distinct composition of CK. Recently immunohistochemical investigations demonstrated that, among others, CKs 6, 14, 16 and 17 are regularly expressed in benign stratified squamous epithelium of the head and neck as well as in squamous cell carcinoma of the head and neck (HNSCC) in contrast to CKs 1, 10 and 11, that were only rarely expressed in these tissues. Materials and Methods: Total RNA was isolated from 15 primary cell lines derived from HNSCC and from 15 tissue samples of oro- and hypopharyngeal carcinomas obtained from surgery specimens. CK expression was evaluated by RT-PCR, Western blot analysis and immunohistochemistry. Results: CK6 and 16 were found to be expressed in both groups at almost 100%. The expression level of CK14 remained constant (73%) in both groups, at the RNA and protein level. CK17 was more frequently present in tumour specimens than in HNSCC cell lines. The immunohistochemical results of the surgical tumour specimens confirmed the results of Western blot analysis. Conclusion: The presented results show high and stable expression rates for CK6 and CK16 in HNSCC. These results will serve as a basis for further investigations concerning the search for circulating tumour cells and micrometastases. In addition, we found that cytokeratin expression in HNSCC is different on the RNA level compared to the protein level.