Exosome-transmitted miR-29a induces colorectal cancer metastasis by destroying the vascular endothelial barrier.

Metastasis is the leading cause of colorectal cancer treatment failure and mortality. Communication between endothelium and tumor cells in the tumor microenvironment is required for cancer metastasis. Tumor-derived exosomes have been shown to increase vascular permeability by delivering microRNA (miRNA) to vascular endothelial cells, facilitating cancer metastasis. The mechanism by which Epithelial-mesenchymal transition (EMT) tumor cell-derived exosomes influence vascular permeability remains unknown. MicroRNA-29a (miR-29a) expression is up-regulated in colorectal cancer (CRC) tissues, which is clinically significant in metastasis. Exosomal miR-29a secreted by EMT-CRC cells has been found to decrease the expression of Zonula occlusion 1 (ZO-1), Claudin-5, and Occludin via targeting Kruppel-like factor 4 (KLF4). In vitro co-culture investigations further revealed that EMT-cancer cells release exosomal miR-29a, which alters vascular endothelial permeability. Furthermore, exosomal miR-29a promoted liver metastases in CRC mice. Our findings demonstrate that EMT-CRC cells may transport exosomal miR-29a to endothelial cells in the tumor microenvironment (TME). As a result, increased vascular permeability promotes the development and metastasis of CRC. Exosomal miR-29a has the potential to be a predictive marker for tumor metastasis as well as a viable therapeutic target for CRC.