The miR-26a/AP-2?/Nanog signaling axis mediates stem cell self-renewal and temozolomide resistance in glioma.

ABSTRACT: Aberrant expression of transcription factor AP-2? has been functionally associated with various cancers, but its clinical significance and molecular mechanisms in human glioma are largely elusive. Methods: AP-2? expression was analyzed in human glioma tissues by immunohistochemistry (IHC) and in glioma cell lines by Western blot. The effects of AP-2? on glioma cell proliferation, migration, invasion and tumor formation were evaluated by the 3-(4,5-dimethyNCthiazol-2-yl)-25-diphenyltetrazolium bromide (MTT) and transwell assays in vitro and in nude mouse models in vivo. The influence of AP-2? on glioma cell stemness was analyzed by sphere-formation, self-renewal and limiting dilution assays in vitro and in intracranial mouse models in vivo. The effects of AP-2? on temozolomide (TMZ) resistance were detected by the MTT assay, cell apoptosis, real-time PCR analysis, western blotting and mouse experiments. The correlation between AP-2? expression and the expression of miR-26a, Nanog was determined by luciferase reporter assays, electrophoretic mobility shift assay (EMSA) and expression analysis. Results: AP-2? expression was downregulated in 58.5% of glioma tissues and in 4 glioma cell lines. AP-2? overexpression not only reduced the proliferation, migration and invasion of glioma cell lines but also suppressed the sphere-formation and self-renewal abilities of glioma stem cells in vitro. Moreover, AP-2? overexpression inhibited subcutaneous and intracranial xenograft tumor growth in vivo. Furthermore, AP-2? enhanced the sensitivity of glioma cells to TMZ. Finally, AP-2? directly bound to the regulatory region of the Nanog gene, reduced Nanog, Sox2 and CD133 expression. Meanwhile, AP-2? indirectly downregulated Nanog expression by inhibiting the interleukin 6/janus kinase 2/signal transducer and activator of transcription 3 (IL6/JAK2/STAT3) signaling pathway, consequently decreasing O6-methylguanine methyltransferase (MGMT) and programmed death-ligand 1 (PD-L1) expression. In addition, miR-26a decreased AP-2? expression by binding to the 3' untranslated region (UTR) of AP-2? and reversed the tumor suppressive role of AP-2? in glioma, which was rescued by a miR-26a inhibitor. TMZ and the miR-26a inhibitor synergistically suppressed intracranial GSC growth. Conclusion: These results suggest that AP-2? reduces the stemness and TMZ resistance of glioma by inhibiting the Nanog/Sox2/CD133 axis and IL6/STAT3 signaling pathways. Therefore, AP-2? and miR-26a inhibition might represent a new target for developing new therapeutic strategies in TMZ resistance and recurrent glioma patients.

SUBMITTER: Huang W 

PROVIDER: S-EPMC6735392 | biostudies-literature | 2019

REPOSITORIES: biostudies-literature