The Role of Cancer Stem Cells in Head and Neck Squamous Cell Carcinoma and Its Clinical Implications

Worldwide, more than 550, 000 new cases of head and neck squamous cell carcinoma (HNSCC) are estimated to occur annually, making it the sixth most common human ma‐ lignancy. Since their discovery in 2007, cancer stem cells (CSCs) in HNSCC have garnered increased interest secondary to their properties of tumorigenicity, differentiation, prolif‐ eration, and self-renewal. CSCs are intrinsically more resistant to traditional treatments such as radiation and chemotherapy, contributing to potential metastasis and recurrence of HNSCC. This chapter focuses first on normal head and neck stem cells, providing background for the discussion of a number of topics pertaining to the study of HNSCC CSCs including molecular biomarkers and clinical implications. Continued research to elucidate the properties of CSCs will undoubtedly expand our knowledge surrounding the pathogenesis, metastasis, and relapse of HNSCC. Ultimately, a better understanding of CSC biomarkers, signaling pathways, and mechanisms of resistance will improve therapies and patient outcomes through targeted interventions.