Background: Glioblastoma (GBM) is the most aggressive brain tumor. Reportedly, circular RNAs (circRNAs) participate in regulation of the development and progression of diverse cancers, including GBM.
Methods: Dysregulated circRNAs in GBM tissues were screened out from GEO database. The expression of candidate circRNAs in GBM cells was measured by qRT-PCR. Loss-of function assays, including colony formation assay, EdU assay, TUNEL assay, and flow cytometry analysis were conducted to determine the effects of circ-AHCY knockdown on GBM cell proliferation and apoptosis. Animal study was further used to prove the inhibitory effect of circ-AHCY silencing on GMB cell growth. Mechanistic experiments like luciferase reporter, RNA pull-down and RNA-binding protein immunoprecipitation (RIP) assays were performed to unveil the downstream molecular mechanism of circ-AHCY. Nanosight Nanoparticle Tracking Analysis (NTA) and PKH67 staining were applied to identify the existence of exosomes.
Results: Circ-AHCY was confirmed to be highly expressed in GBM cells. Circ-AHCY silencing suppressed GBM cell proliferation both in vitro and in vivo. Mechanistically, circ-AHCY activates Wnt/β-catenin signaling pathway by sequestering miR-1294 to up-regulate MYC which activated CTNNB1 transcription. It was also found that circ-AHCY recruited EIF4A3 to stabilize TCF4 mRNA. Enhanced levels of TCF4 and β-catenin contributed to the stability of TCF4/β-catenin complex. In turn, TCF4/β-catenin complex strengthened the transcriptional activity of circ-AHCY. Exosomal circ-AHCY derived from GBM cells induced abnormal proliferation of normal human astrocytes (NHAs).
Conclusion: Exosomal circ-AHCY forms a positive feedback loop with Wnt/β-catenin signaling pathway to promote GBM cell growth.
© 2023 The Authors. Annals of Clinical and Translational Neurology published by Wiley Periodicals LLC on behalf of American Neurological Association.