Background: Neurotensin (NTS) and its primary receptor NTSR1 are implicated in cancer progression. Aberrant expression of NTS/NTSR1 contributes to the proliferation of glioblastoma cells; however, the mechanism is not fully understood.
Methods: Microarray and real-time PCR were performed to identify the NTS-regulated micro (mi)RNAs. The targets of the miRNAs were identified by luciferase assays and immunoblot analysis. The c-Myc binding sites in the miR-29b-1 and cyclin-dependent kinase (CDK)4 promoters were identified through chromatin immunoprecipitation assay. Cell proliferation was evaluated by Cell Counting Kit-8 assay and flow cytometry analysis. An orthotopic xenograft model demonstrated the role of NTS/NTSR1 and miRNAs in glioblastoma growth in vivo.
Results: Pharmacological inhibition or small interfering NTSR1 treatment blocked glioblastoma cell cycle progression in the G1 phase with a concomitantly decreased expression of CDK6, CDK4, and c-Myc. Knockdown of NTSR1 increased the expression of miR-29b-1 and miR-129-3p, which were responsible for the decreased CDK6 expression. NTS/NTSR1 signaling activated the transcription factor c-Myc in U87 cells, leading to increased CDK4 expression and repressed miR-29b-1 expression. Knockdown of NTSR1 decreased the glioblastoma growth in vivo and significantly prolonged the survival time of the tumor-bearing mice, an effect that can be largely reversed by antagomir.
Conclusions: Our study showed a novel regulatory mechanism of NTS/NTSR1, an upstream signaling of miRNAs and c-Myc, in glioblastoma progression. The inhibition of the NTSR1 function or the upregulation of miR-29b-1 and miR-129-3p expression impaired glioma cell proliferation. These results suggested that the NTS/NTSR1/c-Myc/miRNA axis may be a potential therapeutic target for glioblastoma therapy.
Keywords: cell cycle; glioblastoma; miRNAs; neurotensin; signal transduction.
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