Exosomal lncRNA RAMP2-AS1 Derived from Chondrosarcoma Cells Promotes Angiogenesis Through miR-2355-5p/VEGFR2 Axis

Objective: Exosomes derived from cancer cells can alter the microenvironment and enhance cancer malignancy through the regulation of peripheral cell functions. The present study focused on the crosstalk between chondrosarcoma cells and human umbilical vein endothelial cells (HUVECs) mediated by exosomes derived from chondrosarcoma cells and aimed to explore the potential molecular mechanism. Materials and Methods: Chondrosarcoma cell-derived exosomes were isolated and characterized. Cell proliferation assay, tube formation assay and transwell migration assay were performed to characterize the effects of exosomes on HUVECs. The lncRNA microarray was used to select differentially expressed lncRNAs in HUVECs treated with or without exo-somes. Serum samples of patients with chondrosarcoma were collected to analyze the correlation between the RAMP2-AS1 level and the clinicopathological features. Online databases were used to predict the target microRNA of RAMP2-AS1. Dual luciferase reporter assay, Western blotting and qRT-PCR assays were performed to verify the interactions among RAMP2-AS1, miR-2355-5p and VEGFR2. Rescue experiments were conducted to validate the existence of the RAMP2-AS1/miR-2355-5p/VEGFR2 axis. Results: The exosomes secreted by chondrosarcoma cells could enhance HUVECs proliferation, migration and tube formation. LncRNA microarray analysis revealed that exosomes carried lncRNA RAMP2-AS1, and further verification showed that the level of RAMP2-AS1 was increased in the serum of chondrosarcoma patients and was closely related to local invasiveness, distant metastasis and poor prognosis. Subsequent experiments demonstrated that RAMP2-AS1 knockdown could partly abrogate the promoting effects on angiogenesis induced by exosomes derived from chondrosarcoma cells. Moreover, dual luciferase reporter assay and rescue experiments suggested that the RAMP2-AS1/miR-2355-5p/VEGFR2 axis was responsible for exosome-induced angiogenesis of HUVECs. Conclusion: Chondrosarcoma cell-derived exosomes carry lncRNA RAMP2-AS1, which acts as a ceRNA of miR-2355-5p to regulate VEGFR2 expression, thereby positively regulating the angiogenic ability of HUVECs. Thus, exosomal RAMP2-AS1 has the potential as a novel biomarker and therapeutic target for chondrosarcoma.