[Exosomes: potential liquid biopsy in head and neck cancer]

Due to late diagnosis and poor treatment response, advanced head and neck squamous cell carcinoma (HNSCC) belongs to the tumor diseases with highest mortality worldwide. Although many biomarkers have been investigated over the past years, none have yet become established in clinical practice. There is thus an urgent need to introduce noninvasive liquid biopsies that not only give information about cancer activity but also enable early conclusions regarding treatment response. This underlines the biological importance of exosomes from the blood of HNSCC patients. Isolation of exosomes from cell line supernatants and human plasma can easily be performed by size-exclusion chromatography. Thus, protein content, expression patterns, and immunomodulatory effects on immune cells can be evaluated. Further separation of exosomes by cell of origin enables more detailed examination of tumor-derived exosomes (TEX) and exosomes from immune cells. The etiology of the disease, e.g., human papillomavirus (HPV) status, disease activity (active vs. no evident disease), and response to immunotherapies can be detected by exosomal protein expression and immunosuppressive effects of exosomes on different immune cell subtypes. In conclusion, the presented studies can make an essential contribution to the establishment of exosomes as liquid biopsies for head and neck cancer diagnosis and treatment monitoring.