Oral epithelial stem cells—Implications in normal development and cancer metastasis

• Oral epithelium contains a reservoir of stem cells.
• Stem cell markers have been localized mainly in the basal layer.
• Cancer stem cells have been localized in head and neck tumors.
• Cancer stem cells play a key role in oral cancer dissemination and metastasis.
• Targeting oral cancer stem cells may improve disease outcome.

Oral mucosa is continuously exposed to environmental forces and has to be constantly renewed. Accordingly, the oral mucosa epithelium contains a large reservoir of epithelial stem cells necessary for tissue homeostasis. Despite considerable scientific advances in stem cell behavior in a number of tissues, fewer studies have been devoted to the stem cells in the oral epithelium. Most of oral mucosa stem cells studies are focused on identifying cancer stem cells (CSC) in oral squamous cell carcinomas (OSCCs) among other head and neck cancers. OSCCs are the most prevalent epithelial tumors of the head and neck region, marked by their aggressiveness and invasiveness. Due to their highly tumorigenic properties, it has been suggested that CSC may be the critical population of cancer cells in the development of OSCC metastasis. This review presents a brief overview of epithelium stem cells with implications in oral health, and the clinical implications of the CSC concept in OSCC metastatic dissemination.