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

Abstract

MicroRNA-34a (miR-34a) is a master regulator of signaling networks that maintain 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 (OS); however, the molecular mechanisms underlying miR-34a activity in OS are not well defined. Therefore, this study evaluated the role of miR-34a in regulating signal transduction pathways that influence cell death in OS. Levels of miR-34a were attenuated in human OS cells and xenografts of the Pediatric Preclinical Testing Consortium (PPTC). Bioinformatics predictions identified stathmin 1 (STMN1) as a potential miR-34a target. Biotin pulldown assay and luciferase reporter analysis confirmed miR-34a target interactions within the STMN1 mRNA 3′UTR. Overexpression of miR-34a in OS cells suppressed STMN1 expression and reduced cell growth in vitro. Restoration of miR-34a led to microtubule destabilization and increased βIII-tubulin expression, with corresponding G1/G2 phase cell cycle arrest and apoptosis. Knockdown of the Sp1 transcription factor, by siRNA silencing, also upregulated βIII-tubulin expression in OS cells, suggesting 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 OS cells. These results demonstrate that miR-34a directly represses STMN1 gene and protein expression and upregulates βIII-tubulin, leading to disruption of the microtubule network and cell death. Implications The miR-34a/STMN1/βIII-tubulin axis maintains the microtubule cytoskeleton in osteosarcoma, and combining miR-34a with microtubule inhibitors can be investigated as a novel therapeutic strategy.

Epstein‐Barr virus‐encoded miR‐BART6‐3p inhibits cancer cell proliferation through the LOC553103‐STMN1 axis

“…In cell cycle progression, STMN1 integrates different signals to regulate microtubule polymerization and depolymerization to adapt to different stages of the cell cycle 55 . For example, STMN1 acts as an oncogene that promotes the proliferation of osteosarcoma cells 56 . STMN1 has been found to be an important tubulin that inhibits the stability of microtubules (MT), thereby enhancing tumor cell proliferation, invasion and metastasis 57 .…”

Identification of co-expression modules and pathways correlated with osteosarcoma and its metastasis

“…Significant modules were identified to be correlated with osteosarcoma. For the purple module, which was mainly related with microtubule bundle formation, drug metabolism-cytochrome P450, and IL-17 signaling pathway and was identified to be negatively correlated with the trait of osteosarcoma, while being positively correlated with the trait of metastasis in osteosarcoma, previous studies have reported that increase of microtubule destabilization was related with G1/G2 phase cell cycle arrest and apoptosis, and microtubule inhibitors could trigger autophagy and cell death in osteosarcoma cell line [10]. Besides, IL-17A/IL-17RA interaction promoted metastasis of osteosarcoma cells [11].…”

Exosomes in esophageal cancer: A review on tumorigenesis, diagnosis and therapeutic potential

“…Stathmin-1: Stathmin-1 is a microtubule-destabilizing cytosolic phosphoprotein that plays an important role in tumor cell proliferation and migration and may be regulated by miR-34a[30,31], miR-223[32] and miR-193b[33]. It is associated with cancer metastasis and poor prognosis in osteosarcoma[31,34], prostate cancer[35,36], head and neck squamous cell carcinoma[37], hepatocellular carcinoma[32], colorectal cancer[33,38], gallbladder carcinoma[39] and non-small-cell lung cancer[40]. In esophageal squamous cell carcinoma (ESCC), stathmin-1 is also vital for ESCC invasiveness and predicts a poor prognosis[41].…”