The role of BMI1 as a biomarker of cancer stem cells in head and neck cancer: a review.

Emerging studies show that BMI1 (B cell-specific Moloney murine leukemia virus integration site 1) has an important function as a biomarker of cancer stem cells (CSCs), i.e. cells with self-renewal characteristics, capable of tumor initiation, progression, invasion, metastasis, tumor recurrence and resistance to chemotherapy and radiotherapy. The failure of current anticancer therapies can be attributed to the relative ineffectiveness of drug and radiation treatments on CSCs, thereby preserving the full capacity of the cells to reproduce tumors. The development of new strategies is currently hindered by the lack of reliable markers for the identification of these CSCs. At present, they have been isolated from solid tumors at various locations using a variety of surface markers, including CD34, CD133, CD24, CD44, CD29 and CD31, in addition to the methods of isolation and cell culture via the Wnt, BMI1, Notch and Hedgehog pathways. The discovery of specific tumor targets for CSCs would constitute a big step in the research for the definitive therapy against cancer. More studies are being conducted that consider the role of CSCs in head and neck cancers with potential for an impact on clinical-surgical outcomes from the knowledge that is being gained. A promising intracellular marker of CSCs in head and neck cancer is the oncoprotein BMI1, with specific data about its prognostic value based on the specific location.