Hypoxic Pancreatic Cancer Cell-derived Exosomal LncRNA-UCA1 Promotes Angiogenesis Via Mediating MiR-96-5p/AMOTL2 Axis

Background: Hypoxia microenvironment,as an important feature of solid tumors,promotes tumor cells to release exosomes and enhances tumor angiogenesis.However,the detail functions and underlying mechanisms of hypoxic exosomes in pancreatic cancer(PC)remain largely unknown.Methods: Exosomes derived from pancreatic cancer cells cultured under normoxic and hypoxic conditions were isolated by ultracentrifugation and kit assay and identified by transmission electron microscopy,nanoparticle tracking analysis and western blot analysis.The abilities of cell migration and tube formation of HUVEC were evaluated by wound healing,transwell migration assay and an in vitro matrigel tube formation assay.The expression levels of lncRNA-UCA1 in cells and exosomes were examined by qRT-PCR.The expression level of exosomal lncRNA-UCA1 derived from serum of PC patients was also assessed by qRT-PCR and the correlation between exosomal lncRNA-UCA1 and clinicopathological parameters as well as prognosis was further analyzed.Luciferase reporter assay,RNA immunoprecipitation and rescued assays were employed to confirm the interactions between lncRNA-UCA1,miR-96-5p and AMOTL2.The functions of hypoxic exosomal lncRNA-UCA1 in angiogenesis and tumor growth were also indicated in a mouse xenograft model.Results: We found that hypoxia exosomes derived from pancreatic cancer cells significantly promoted cell migration and tube formation of HUVEC.Importantly,lncRNA-UCA1 was highly expressed in exosomes derived from hypoxic PC cells and exosomes and could be transferred to HUVEC through the exosomes.In addition,the expression level of lncRNA-UCA1 in the human serum-derived exosomes of PC patients was higher than that in the healthy controls and predicted poor survival of PC patients.Moreover,hypoxic exosomal lncRNA-UCA1 could promote angiogenesis and tumor growth in vitro and in vivo.In terms of mechanism,lncRNA-UCA1 acted as a miR-96-5p sponge to relieve the repressive effects of miR-96-5p on its target gene AMOTL2.Conclusion: LncRNA-UCA1 was highly expressed in exosomes derived from hypoxic PC cells and PC patients' serum,and positively correlated with the poor prognosis of PC patients.Hypoxic exosomal lncRNA-UCA1 could promote angiogenesis through miR-96-5p/AMOTL2 axis.