Exosomes in HNSCC Progression

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Exosomes are small extracellular vesicles (EVs) that are secreted from multivesicular endosomes (MVE) and have been recently recognized to promote cancer metastasis. Exosomes carry bioactive proteins, lipids and nucleic acids and are an important but poorly understood component of the tumor microenvironment. We recently discovered that actin-rich invasive structures called invadopodia are key docking sites for MVE in cancer cells, leading to enhanced exosome secretion. Furthermore, we found that the key invadopodia regulator cortactin enhances MVE docking and exosome secretion. Notably, cortactin is gene amplified and overexpressed in a number of cancers, especially in head and neck squamous cell carcinoma (HNSCC). Furthermore, cortactin overexpression in HNSCC is correlated with decreased patient survival and increased metastasis. Based on these data, we hypothesize that cortactin overexpression drives poor prognosis in HNSCC due to its key role in promoting exosome secretion. Furthermore, we hypothesize that key exosome cargoes synergize with cortactin to promote tumor-induced angiogenesis, lymphangiogenesis, and metastasis. Specifically, we have identified EphB-ephrinB signaling as a key angiogenic axis regulated by HNSCC-secreted exosomes. Thus, we propose that both the number and molecular cargo of exosomes drive aggressive HNSCC behavior in a synergistic manner. We will test these hypotheses and leverage our work to identify potential exosomal blood-and tissue-based biomarkers of regional and distant metastasis.