The Microtubule Network and Cell Death Are Regulated by an miR-34a/Stathmin 1/beta III-Tubulin Axis

作者：Vetter Nancy S; Kolb E A; Mills Christopher C; Sampson Valerie B^*

来源：Molecular Cancer Research, 2017, 15(7): 953-964.

DOI：10.1158/1541-7786.MCR-16-0372

MicroRNA-34a (miR-34a) is a master regulator of signaling networks that maintains normal physiology and disease and is currently in development as a miRNA-based therapy for cancer. Prior studies have reported low miR-34a expression in osteosarcoma; however, the molecular mechanisms underlying miR-34a activity in osteosarcoma are not well-defined. Therefore, this study evaluated the role of miR-34a in regulating signal transduction pathways that influence cell death in osteosarcoma. Levels of miR-34a were attenuated in human osteosarcoma cells and xenografts of the Pediatric Preclinical Testing Consortium (PPTC). Bioinformatics predictions identified stathmin 1 (STMN1) as a potential miR-34a target. Biotin pull-down assay and luciferase reporter analysis confirmed miR-34a target interactions within the STMN1 mRNA 30-untranslated region. Overexpression of miR-34a in osteosarcoma cells suppressed STMN1 expression and reduced cell growth in vitro. Restoration of miR-34a led to microtubule destabilization and increased beta III-tubulin expression, with corre-sponding G1-G2 phase cell-cycle arrest and apoptosis. Knockdown of the Sp1 transcription factor, by siRNA silencing, also upregulated bIII-tubulin expression in osteosarcoma cells, suggesting that miR-34a indirectly affects Sp1. Validating the coordinating role of miR-34a in microtubule destabilization, when miR-34a was combined with either microtubule inhibitors or chemotherapy, STMN1 phosphorylation was suppressed and there was greater cytotoxicity in osteosarcoma cells. These results demonstrate that miR-34a directly represses STMN1 gene and protein expression and upregulates bIII-tubulin, leading to disruption of the microtubule network and cell death.

• 出版日期2017-7