Exosomal S100a9 Activates Fibroblasts To Promote Acc Lung Metastasis

To investigate the role of S100A9-enriched exosomes in lung metastasis of adenoid cystic carcinoma (ACC) and the underlying mechanism. Using microarrays on two ACC cell lines, exosome proteomics on their exosomes, and immunohistochemistry on ACC patient samples, we measured S100A9 levels and its association with ACC progression. Single-cell RNA sequencing analysis revealed interactions between CAFs and tumor cells in ACC, confirmed by multiplex immunohistochemistry staining. We further employed immunofluorescence, collagen contraction assays, and Transwell migration assays to evaluate the effects of S100A9-enriched exosomes on fibroblasts. RNA sequencing of fibroblasts treated with these exosomes indicated the activation of specific signaling pathways. The expression levels of E-cadherin, FAP, IL-17 and TNF-α in activated fibroblasts and tumor cells were subsequently determined using Western blotting, RT-PCR, and ELISA. Furthermore, NOD/SCID mice were used to assess the impact of exosomes on lung metastasis. S100A9 was enriched in the ACC cell line with high propensity for lung metastasis and was associated with advanced clinical stage. Moreover, a strong interaction was observed between specific myCAF subpopulations and EMT cells, highlighting their cooperative role in tumor progression. Exosomes derived from ACC tumor cells could activate fibroblasts in the TME, thereby activating the IL-17-TNF-NF-κB signaling pathways. In turn, activated CAFs further promote EMT and facilitate lung metastasis through IL-17 signaling in ACC. We identified S100A9 in exosomecrine way could activate fibroblasts in TME therefore promotes ACC lung metastasis, suggesting that targeting S100A9 might lead to new treatments.