OBJECTIVE: Tumor-secreted exosomes are essential in driving tumor progression by releasing multivesicular bodies (MVBs), which are endosome organelles containing intraluminal vesicles (ILVs), as exosomes. However, the mechanisms controlling MVB biosynthesis, trafficking, and exosome exocytosis are not fully understood. METHODS: We examined the expression of vesicle-associated membrane protein 2 (VAMP2) and synaptosome-associated protein 25 (SNAP25) in head and neck cancer (HNC) tumor tissues using clinical analysis. Techniques, like nanoparticle tracking analysis (NTA), transmission electron microscopy (TEM), and exosome quantification, were used to study the roles of VAMP2 and SNAP25 in exosome secretion. Experiments involving overexpression or depletion of VAMP2 and SNAP25 were performed to observe effects on exosome release, MVB trafficking, and cellular behavior. RESULTS: Clinical data showed that VAMP2 and SNAP25 were significantly upregulated in HNC tissues and linked to tumor progression. Increased expression of these proteins boosted exosome secretion and enhanced HNC cell tumorigenicity. Conversely, depleting VAMP2 or SNAP25 impaired MVB release, causing intracellular buildup of MVBs and ILVs, and reduced exosome secretion, which was reversible by exosome degradation methods. Blocking exosome secretion by inhibiting MVB-plasma membrane fusion weakened tumorigenic capacities but triggered a compensatory Ras-related protein Rab-11A-myosin9-phosphatidylserine (PS) externalization pathway, releasing MVB-like extracellular vesicle (EV) clusters. CONCLUSIONS: VAMP2 and SNAP25 are key to exosome secretion and HNC tumor progression. Suppressing this pathway activated a compensatory Rab11a-myosin9-PS mechanism that sustained EV release. A dual-targeting strategy that blocks both VAMP2/SNAP25-mediated exosome secretion and the Rab11a-myosin9-PS pathway may improve tumor cell eradication, offering a potential treatment for HNC and other cancers.
Bai et al. (Tue,) studied this question.