Potential stem cell marker CD44 is constitutively expressed in permanent cell lines of head and neck cancer

Background: Despite significant advances in the use of diagnosis and therapy to treat head and neck squamous cell carcinoma (HNSCC), the prognosis has improved only marginally in the last decades. Thus, there is an enormous need for better understanding of tumor biology and reversely novel immunotherapeutic approaches. It is becoming increasingly obvious that stem cells play an important role in tumor development and progression. The identity of these cells and the underlying cellular and molecular mechanisms are mostly unknown in HNSCC to date. Materials and Methods: Solid HNSCC tumors, as well as permanent HNSCC cell lines, were analyzed by flow cytometry concerning the expression of different putative stem cell marker proteins. Results: Distinct populations of CD44 expressing potential stem cells could be identified in solid tumors of HNSCC patients with strong individual deviations. Surprisingly, the potential stem cell marker CD44 was found to be constitutively expressed on the surface of all the permanent HNSCC cell lines analyzed. Conclusion: CD44+ 'tumor stem cells' may play a key role in the establishment of permanent HNSCC cell lines, selecting especially robust cell entities that might drive the progression and metastasis of HNSCC. Individual analysis of 'tumor stem cell' markers will be an important tool for innovative therapies and for determining the prognosis of patients with HNSCC.