Cancer-secreted exosomal miR-1825 induces angiogenesis to promote colorectal cancer metastasis.

Background: Angiogenesis is one of the important factors related to tumorigenesis, invasion, and metastasis. Cancer-secreted exosomes are essential mediators of intercellular cross-talk and participate in angiogenesis and metastasis. Unveiling the mechanism of angiogenesis is an important way to develop anti-angiogenesis therapeutic strategies to against cancer progression.

Methods: miR-1825 expression and relationship with microvascular density were validated in colorectal cancer (CRC) by in situ hybridization (ISH) staining and immunohistochemistry (IHC). Sequential differential centrifugation, transmission electron microscopy, and western blotting analysis were used to extract and characterize exosomes. The effort of exosomal miR-1825 on endothelial cells was examined by transwell assay, wound healing assay, tube formation assay, and aortic ring assay. The relationship of miR-1825, ING1 and the downstream pathway were analyzed by western blot, RT-PCR, Immunofluorescence, and dual-luciferase reporter system analysis.

Results: Exosomal miR-1825 is associated with angiogenesis in CRC and is enriched in exosomes extracted from the serum of CRC patients. The CRC-secreted exosomal miR-1825 can be transferred into vascular endothelial cells, promoting endothelial cell migration and tube formation in vitro, and facilitating angiogenesis and tumor metastasis in vivo. Mechanistically, exosomal miR-1825 regulates angiogenesis and tumor metastasis by suppressing inhibitor of growth family member 1 (ING1) and activating the TGF-β/Smad2/Smad3 signaling pathway in the recipient HUVECs.

Conclusions: Our study demonstrated the CRC-secreted exosomal miR-1825 could be transferred to vascular endothelial cells, subsequently leads to the inhibition of ING1 and the activation of the TGF-β/Smad2/Smad3 signaling pathway, thereby promoting angiogenesis and liver metastasis in CRC. Exosomal miR-1825 is thus a potential diagnostic and therapeutic target for CRC patients.