Biosynthetic circ-PLEKHA5 stabilized by SRSF7 promotes the vasculogenic mimicry of glioblastoma cells by encoding a novel protein 622aa

Background: Increasing studies have been demonstrated that circRNAs play vital regulatory roles in the biological behaviors of glioblastoma cells, and increasing circRNAs are found to have the capacity of encoding small peptides, which are involved in the regulatory process.Methods: Western blot and qRT-PCR were conducted to confirm the expression of SRSF7 and circ-PLEKHA5 respectively. RNase R digestion assay and fluorescence in situ hybridization assays were conducted to evaluate the existence and cellular location of circ-PLEKHA5. RIP assay was used to access the relationship between SRSF7 and circ-PLEKHA5. Dual-luciferase assay and FLAG tag assays were performed to test the coding capability of circ-PLEKHA5. Immunofluorescence assay was conducted to evaluate the location of circ-PLEKHA5-622aa. CCK-8, vasculogenic mimicry (VM) formation and transwell assays were used to evaluate the roles of SRSF7, circ-PLEKHA5, circ-PLEKHA5-622aa on proliferation, VM formation, migration and invasion. Nude mice xenograft studys with PAS-CD34 staining were used to clarify the functional roles of SRSF7 and circ-PLEKHA5 on VM formation in vivo.Results: SRSF7 was up-regulated in glioma, and promoted the proliferation, migration, invasion, VM formation and the expression of VM-associated proteins of glioma cells by increasing the expression of circ-PLEKHA5. Circ-PLEKHA5 was mainly localized in cytoplasm and promoted the proliferation, migration, invasion, VM formation and the expression of VM-associated proteins of glioma cells by encoding a novel protein circ-PLEKHA5-622aa. The application of SRSF7 and circ-PLEKHA5 inhibitor significantly suppressed the tumor growth and VM formation in vivo.Conclusions: This study first demonstrated the coding ability of circ-PLEKHA5, and identified the regulatory roles of SRSF7/circ-PLEKHA5/circ-PLEKHA5-622aa pathway in VM formation of glioblastoma cells. Our findings might provide a novel strategy for glioma treatment.