TGFβ signaling-induced miRNA participates in autophagic regulation by targeting PRAS40 in mesenchymal subtype of glioblastoma

Objective: Mesenchymal subtype of glioblastoma (mesGBM) is a refractory disease condition characterized by therapeutic failure and tumor recurrence. Hyperactive transforming growth factor-β (TGF-β) signaling could be a signature event in mesGBM, which leads to dysregulation of downstream targets and contribute to malignant transformation. In this study we aimed to investigate the hyperactive TGFβ signaling-mediated pathogenesis and possible downstream targets for the development of novel therapeutic interventions for mesGBM. Methods: GBM-BioDP is an online resource for accessing and displaying interactive views of the TCGA GBM data set. Transcriptomic sequencing followed by bioinformatic analysis was performed to identify dysregulated microRNAs. Target prediction by MR-microT and dual luciferase reporter assay were utilized to confirm the predicted target of novel_miR56. CCK-8 assays was used to assesse cell viability. The miRNA manipulation was proceeded by cell transfection and lentivirus delivery. A plasmid expressing GFP-LC3 was introduced to visualize the formation of autophagosomes. Orthotopic GBM model was constructed for in vivo study. Results: TGFβ1 and TGFβ receptor type II (TβRII) were exclusively upregulated in mesGBM (P < 0.01). Dysregulated miRNAs were identified after LY2109761 (a TβRI/II inhibitor) treatment in a mesGBM-derived cell line, and novel_miR56 was selected as a promising candidate for further functional verification. Novel_miR56 was found to potentially bind to PRAS40 via seed region complementarity in the 3′ untranslated region, and we also confirmed that PRAS40 is a direct target of novel_miR56 in glioma cells. In vitro, over expression of novel_miR56 in tumor cells significantly promoted proliferation and inhibited autophagy (P < 0.05). The expression levels of P62/SQSTM was significantly increased accompanied by the decrease of BECN1 and LC3B-II/I, which indicated that autophagic activity was reduced after novel_miR56 treatment. In addition, over expression of novel_miR56 also promoted tumor growth and inhibited autophagy in vivo, which is associated with worse prognosis (P < 0.05). Conclusions: In summary, we provide novel insight into TGFβ signaling-mediated pathogenesis in mesGBM and TGFβ signaling-induced novel_miR56 may be a novel target for mesGBM management.