Extracellular Vesicles Secreted by Cancer-Associated Fibroblasts Drive Non-Invasive Cancer Cell Progression to Metastasis via TGF-β Signalling Hyperactivation.

Metastasis is the leading cause of cancer-related deaths. Cancer-associated fibroblasts (CAFs) are abundant components within the tumour microenvironment, playing critical roles in metastasis. Although increasing evidence supports a role for small extracellular vesicles (sEVs) in this process, their precise contribution and molecular mechanisms remain unclear, compromising the development of antimetastatic therapies. Here, we establish that CAF-sEVs drive metastasis by mediating CAF-cancer cell interaction and hyperactivating TGF-β signalling in tumour cells. Metastasis is abolished by genetically targeting CAF-sEV secretion and consequent reduction of TGF-β signalling in cancer cells. Pharmacological treatment with dimethyl amiloride (DMA) decreases CAFs' sEV secretion, reduces TGF-β signalling levels in tumour cells and abrogates metastasis and tumour self-seeding. This work defines a new mechanism required by CAFs to drive cancer progression, supporting the therapeutic targeting of EV trafficking to disable the driving forces of metastasis.