Biology and immunology of cancer stem(-like) cells in head and neck cancer

• Cancer stem(-like) cells (CSCs) represent a subpopulation of head and neck cancer.
• CSCs contribute to resistance to current therapies.
• The immune system can recognize CSCs.
• In turn CSC may evade the hosts’ immune response and induce immune suppression.
• Ways of improving immune responses to CSC are explored for immunotherapy.

Immunological approaches against tumors including head and neck squamous cell carcinoma (HNSCC) have been investigated for about 50 years. Such immunotherapeutic treatments are still not sufficiently effective for therapy of HNSCC. Despite the existence of immunosurveillance tumor cells may escape from the host immune system by a variety of mechanisms. Recent findings have indicated that cancer stem(-like) cells (CSCs) in HNSCC have the ability to reconstitute the heterogeneity of the bulk tumor and contribute to immunosuppression and resistance to current therapies. With regard to the CSC model, future immunotherapy possibly in combination with other modes of treatment should target this subpopulation specifically to reduce local recurrence and metastasis. In this review, we will summarize recent research findings on immunological features of CSCs and the potential of immune targeting of CSCs.