Recent studies have identified tumor-derived microvesicles called exosomes as vehicles for long-distance communication, due to their complex content of proteins and microRNAs. In head and neck squamous cell carcinoma, as in many other cancers, exosome secretion is associated with advanced patient stage. In most cases, those vesicles are classified as exosomes, 50-100 nm vesicles that have been shown to mediate progression, metastasis, survival, drug resistance, immune modulation, and many other aggressive cancer phenotypes. The mechanisms by which exosomes are generated are poorly understood, although exosomes are known to derive from a late endocytic compartment. Our recent preliminary data suggest that invadopodia are sites of exosome secretion and that, conversely, canonical invadopodia regulators affect exosome secretion. Based on these and other findings, we hypothesize that exocytic late endosomal/lysosomal pathways that govern invadopodia activity and exosome secretion may be one and the same. Furthermore, these pathways are likely to be unregulated in the 30-40% of HNSCC tumors that carry amplification of the 11q13.3 amplicon, since we have shown that the 11q13-amplified cytoskeletal protein cortactin is a key regulator of invadopodia activity, exosome secretion, and tumor aggressiveness. In this project, we will test whether invadopodia represent docking sites for exosomes and identify key intracellular regulatory points for exosome secretion by HNSCC cells. We will also test the hypothesis that 11q13-amplification is an independent predictor of exosome secretion in HNSCC patients. Finally, we will determine whether inhibition of exosome secretion represents a viable therapeutic strategy in HNSCC.
This project will study the mechanism and impact of exosome secretion in head and neck squamous cell carcinoma progression. The project is relevant to public health because it will lead to a greater understanding of mechanisms that lead to head and neck cancer aggressiveness and test whether anti-exosome targeting is a promising therapeutic option.
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