Abstract
BackgroundGrowing evidences indicate that circular RNAs (circRNAs) play an important role in the regulation of biological behavior of tumor. We aim to explore the role of circRNA in glioma and elucidate how circRNA acts.MethodsReal-time PCR was used to examine the expression of circPTN in glioma tissues and normal brain tissues (NBT). Assays of dual- luciferase reporter system, biotin label RNA pull-down and FISH were used to determine that circPTN could sponge miR-145-5p and miR-330-5p. Tumor sphere formation assay was performed to determine self- renewal of glioma stem cell (GSCs). Cell counting Kit-8 (CCK8), EdU assay and flow cytometry were used to investigate proliferation and cell cycle. Intracranial xenograft was established to determine how circPTN impacts in vivo. Tumor sphere formation assay was performed to determine self- renewal of glioma stem cell (GSCs).ResultsWe demonstrated circPTN was significantly higher expression in glioma tissues and glioma cell lines, compared with NBT and HEB (human astrocyte). In gain- and loss-of-function experiments, circPTN significantly promoted glioma growth in vitro and in vivo. Furthermore, we performed dual-luciferase reporter assays and RNA pull-down assays to verify that circPTN acts through sponging miR-145-5p and miR-330-5p. Increasing expression of circPTN rescued the inhibition of proliferation and downregulation of SOX9/ITGA5 in glioma cells by miR-145-5p/miR-330-5p. In addition, we found that circPTN promoted self-renewal and increased the expression of stemness markers (Nestin, CD133, SOX9, and SOX2) via sponging miR-145-5p. Moreover, this regulation was disappeared when circPTN binding sites in miR-145-5p were mutated.ConclusionsOur results suggest that circPTN is an oncogenic factor that acts by sponging miR-145-5p/miR-330-5p in glioma.
Highlights
Growing evidences indicate that circular RNAs play an important role in the regulation of biological behavior of tumor
The mechanism underlying the action of circular RNA (circRNA) is unknown, certain circRNAs have been reported to function via microRNA-sponging [11,12,13,14,15,16,17,18,19], binding to RNA-binding protein (RBP) [20,21,22], or by interacting with RNA-pol II to regulate transcription [23] and translation of peptides and proteins [24,25,26,27]
Considering the expression profiles in glioma cell lines compared with normal astrocytes-HEB, and considering the size of these circRNAs, we selected circPTN, which is derived from the pleiotrophin (PTN) gene, for further study
Summary
We aim to explore the role of circRNA in glioma and elucidate how circRNA acts. After demonstrating the impact of circPTN in vitro, we aimed to investigate whether circPTN influences the biological behavior of tumors in vivo. CircPTN sponges miR-145-5p and miR-330-5p and accelerates their degradation we aimed to investigate how circPTN promotes glioma proliferation. Previous studies have reported that miR-145-5p and miR-330-5p are tumor suppressive factors that inhibit cell proliferation [36, 37], we aimed to confirm this effect in our experimental system
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