TTBK2 circular RNA promotes glioma malignancy by regulating miR-217/HNF1β/Derlin-1 pathway

J Hematol Oncol. 2017 Feb 20;10(1):52. doi: 10.1186/s13045-017-0422-2.


Background: Circular RNAs are a subgroup of non-coding RNAs and generated by a mammalian genome. Herein, the expression and function of circular RNA circ-TTBK2 were investigated in human glioma cells.

Methods: Fluorescence in situ hybridization and quantitative real-time PCR were conducted to profile the cell distribution and expression of circ-TTBK2 and microRNA-217 (miR-217) in glioma tissues and cells. Immunohistochemical and western blot were used to determine the expression of HNF1β and Derlin-1 in glioma tissues and cells. Stable knockdown of circ-TTBK2 or overexpression of miR-217 glioma cell lines (U87 and U251) were established to explore the function of circ-TTBK2 and miR-217 in glioma cells. Further, luciferase reports and RNA immunoprecipitation were used to investigate the correlation between circ-TTBK2 and miR-217. Cell Counting Kit-8, transwell assays, and flow cytometry were used to investigate circ-TTBK2 and miR-217 function including cell proliferation, migration and invasion, and apoptosis, respectively. ChIP assays were used to ascertain the correlations between HNF1β and Derlin-1.

Results: We found that circ-TTBK2 was upregulated in glioma tissues and cell lines, while linear TTBK2 was not dysregulated in glioma tissues and cells. Enhanced expression of circ-TTBK2 promoted cell proliferation, migration, and invasion, while inhibited apoptosis. MiR-217 was downregulated in glioma tissues and cell lines. We also found that circ-TTBK2, but not linear TTBK2, acted as miR-217 sponge in a sequence-specific manner. In addition, upregulated circ-TTBK2 decreased miR-217 expression and there was a reciprocal negative feedback between them in an Argonaute2-dependent manner. Moreover, reintroduction of miR-217 significantly reversed circ-TTBK2-mediated promotion of glioma progression. HNF1β was a direct target of miR-217, and played oncogenic role in glioma cells. Remarkably, circ-TTBK2 knockdown combined with miR-217 overexpression led to tumor regression in vivo.

Conclusions: These results demonstrated a novel role circ-TTBK2 in the glioma progression.

Keywords: Circular RNAs; Glioma; MicroRNAs; circ-TTBK2; miR-217.

MeSH terms

  • Apoptosis
  • Biopsy
  • Cell Line, Tumor
  • Cell Movement
  • Cell Proliferation
  • Disease Progression
  • Glioma / pathology*
  • Hepatocyte Nuclear Factor 1-beta / metabolism*
  • Humans
  • Membrane Proteins / metabolism*
  • MicroRNAs / analysis
  • MicroRNAs / metabolism*
  • Neoplasm Invasiveness
  • Protein Serine-Threonine Kinases / genetics*
  • RNA / analysis
  • RNA / physiology*
  • RNA, Circular
  • Signal Transduction


  • DERL1 protein, human
  • HNF1B protein, human
  • MIRN217 microRNA, human
  • Membrane Proteins
  • MicroRNAs
  • RNA, Circular
  • Hepatocyte Nuclear Factor 1-beta
  • RNA
  • tau-tubulin kinase
  • Protein Serine-Threonine Kinases