Cancer Stem Cells in Head and Neck Squamous Cell Carcinoma-Treatment Modalities

Head and neck squamous cell carcinoma (HNSCC) belongs to the most frequent cancer subtypes in the world. Mutations due to genetic and chromosomal instability, syndromes such as Fanconi anemia and the Bloom syndrome, environmental risk factors such as tobacco smoking, alcohol and human papillomavirus infection (HPV) subtypes 16,18,31,33,35,52,58 are implicated in its pathogenesis. The HNSCC belongs to the solid tumors of epithelial origin and consists of stromal, inflammatory, cancer cells and most importantly a fraction of them, the cancer stem cells (CSCs). The identification of the CSCs through their biomarkers such as CD44, CD10, CD166, CD133, CD271, ALDH, Oct4, Nanog, Sox2 and Bmi1, the maintenance of their subpopulation through epithelial to mesenchymal transition, the role of HPV infection regarding their prognosis and of their microenvironment regarding their resistance to therapy, all constitute key elements that must be taken thoroughly into consideration in order to develop an effective targeted therapy. There are already therapies in place targeting specific related biomarkers, important biochemical pathways and growth factors. The aim of this literature review is to illustrate the treatment modalities available against the cancer stem cells of head and neck squamous cell carcinoma.