Cancer stem cells in moderately differentiated oral tongue squamous cell carcinoma express components of the renin–angiotensin system

INTRODUCTION Oral cancers are the 10th most common cancer worldwide, with oral tongue squamous cell carcinoma (OTSCC) having the highest incidence. Surgery and radiotherapy (RT), the mainstay treatments for OTSCC, impact on the patients’ quality of life and the 50% 5-year survival has remained unchanged for 40 years. Cancer stem cells (CSCs) have been proposed to be the origin of many cancers, including oral cavity squamous cell carcinoma (OCSCC). CSCs express the embryonic stem cell (ESC) markers OCT4, NANOG, SOX2, SALL4 and STAT3, the more ‘downstream’ CSC marker CD44 and the epithelial cell marker p63, suggesting a diverse phenotype. The relative abundance and co-expression of these markers and their localisation within OCSCC remain unclear.