Colorectal cancer-derived small extracellular vesicles induce TGF?1-mediated epithelial to mesenchymal transition of hepatocytes

Background Metastatic disease is the major cause of cancer-related deaths. Increasing evidence shows that pri- mary tumor cells can promote metastasis by preparing the local microenvironment of distant organs, inducing the formation of the so-called "pre-metastatic niche". In recent years, several studies have highlighted that among the tumor-derived molecular components active in pre-metastatic niche formation, small extracellular vesicles (sEVs) play a crucial role. Regarding liver metastasis, the ability of tumor-derived sEVs to affect the activities of non-parenchymal cells such as Kupffer cells and hepatic stellate cells is well described, while the effects on hepatocytes, the most con- spicuous and functionally relevant hepatic cellular component, remain unknown. Methods sEVs isolated from SW480 and SW620 CRC cells and from clinical samples of CRC patients and healthy sub- jects were used to treat human healthy hepatocytes (THLE-2 cells). RT-qPCR, Western blot and confocal microscopy were applied to investigate the effects of this treatment. Results Our study shows for the first time that TGF?1-carrying CRC_sEVs impair the morphological and func- tional properties of healthy human hepatocytes by triggering their TGF?1/SMAD-dependent EMT. These abilities of CRC_sEVs were further confirmed by evaluating the effects elicited on hepatocytes by sEVs isolated from plasma and biopsies from CRC patients. Conclusions Since it is known that EMT of hepatocytes leads to the formation of a fibrotic environment, a well- known driver of metastasis, these results suggest that CRC_sEV-educated hepatocytes could have an active and until now neglected role during liver metastasis formation.