Oral cancer stem cells: Drivers of local recurrence and metastasis

Oral squamous cell carcinoma (OSCC) is one of the most feared human cancers due to its aggressiveness and high mortality rate. One of the reasons for its treatment failure is thought to be related to the presence of a subpopulation of cells within the tumor called cancer stem cells (CSCs) which are highly tumorogenic, capable of self-renewal, and have the ability to differentiate into cells that constitute the bulk of tumors. Recent evidence suggests that CSCs are especially, resistant to conventional therapy and are the "drivers" of local recurrence and metastatic spread. Research in the recent years has been aimed at the application of stem cell biology to clinical medicine, particularly its role in the evolution and metastasis of tumors. Several stem cell markers are known to be expressed, mainly in the basal layers of oral mucosa which are necessary for tissue homeostasis. These specific markers for CSCs have been investigated in head and neck SCC in the hope of developing a deeper understanding of the role of CSCs in oral cancer pathogenesis, diagnosis, and developing newer therapeutic strategies. This review aims at presenting CSC and their biomarkers with a special emphasis on their role in oral tumorogenesis and OSCC metastasis. It also aims to explain the potential role of these CSC in improving the diagnosis, prognosis, and treatment of OSCC patients.