CRC Cell-secreted Exosomal MiR-106a Promotes Angiogenesis And Increases Vascular Permeability By Targeting S1PR1

Colorectal Cancer(CRC)is one of the most common malignancies in clinical practice,which are the third most common type of cancer worldwide,just after lung cancer and breast cancer.The 5-year survival rate for colorectal cancer patients is 60-95%,while the 5-year survival rate for advanced colorectal cancer is only about 35%.Therefore,it's extremely important to explore the pathogenesis of colorectal cancer as well as inhibit the progression and metastasis of CRC.However,the pathogenesis of CRC is extremely complicated,with a variety of gene mutations and dysregulation of intracellular signaling networks,not mention the genetic variation among individuals.MicroRNAs(miRNAs)are a class of single-stranded non-coding small RNAs with a length about 19-23 nt.It has been reported that miRNAs can bind to the m RNA of the target gene,which lead to the inhibition of the translation or lead to the degradation of m RNA,and eventually reduce the expression level of the targeted protein.Thus,miRNAs can affect various physiological and pathological functions in the cell.The expression of miRNAs is highly conserved and has obvious spatiotemporal specificity.Studies have demonstrated that miRNAs are closely related to the development of human tumors.Exosomes are a kind of biofilm microvesicle structure with a diameter of 40-150 nm and can stay stable in almost all humoral environments.Exosomes can transfer miRNA,cytokine and other bioactive molecules to the receptor cells by membrane fusion.Thereby,alter the physiological function of the receptor cells.The stability and high efficiency of exosomes make them an important component of intercellular communication in tumor microenvironment.miRNA-contained exosomes are closely related to the development of colorectal cancer.The study of miRNAs with abnormal changes during the development of colorectal cancer can provide a new insight for the treatment of colorectal cancer and is of great significance for the investigation and treatment of colorectal cancer.Previous studies in our laboratory demonstrated that the expression level of miR-106 a in the plasma of CRC patients was elevated and correlated with prognosis.We first studied the existence form of miR-106 a in plasma and then analyzed the relationship between its expression level and the TNM stage of CRC patients.The results showed that miR-106 a was mainly existed in plasma exosomes and positively correlated with the stage of CRC patients.We further tested the expression level of miR-106 a in CRC cell lines,and then transfected miR-106 a inhibitors or mimics to different cells.We isolate their exosomes from culture media and finally obtained exosomes with different miR-106 a expression level.We then co-cultured the exosomes with vascular endothelial cells(HUVEC),and found that the co-culture with miR-106 a highly-expressed exosomes could promote the tube formation of the endothelial cells and increase the permeability of the endothelial monolayer,while the co-culture of exosomes with low expression level of miR-106 a could inhibit the tube formation of endothelial cells and reduce the permeability of endothelial monolayer.Animal experiments also showed that miR-106 a could promote angiogenesis and promote vascular permeability in tumor tissues and distant organs,such as liver and lung.Next,bioinformatic analysis showed that S1PR1 may be the downstream target gene of miR-106 a.Luciferase reporter assays confirmed that miR-106 a could directly bind to the 3'-UTR region of S1PR1,and Western-blot analysis also confirmed that miR-106 a could negatively regulate the expression of S1PR1.In addition,we found that the downregulation of S1PR1 inhibited the membrane location of VE-cadherin,thereby reducing the tight junction among endothelial cells.The reconstruction of S1PR1 completely convert the function of miR-106 a,which confirmed that S1PR1 was the target of miR-106 a in angiogenesis and vascular permeability.In summary,our findings demonstrated that CRC cells could transfer exosomal miR-106 a to endothelial cells,which inhibited the expression of S1PR1 in endothelial cells and inhibit the membrane localization of VE-cadherin,promoting angiogenesis and increasing the permeability of blood vessels,and ultimately promote CRC metastasis.