Curr Cancer Drug Targets. 2013; 13(2):221-31.

The miR-183/96/182 Cluster Regulates Oxidative Apoptosis and Sensitizes Cells to Chemotherapy in Gliomas

Hailin Tang a, b, Yanhui Biana ,b, Chaofeng Tu a,b,c, Zeyou Wanga ,b, Zhibin Yua, b, Qing Liu b, Gang Xua, Minghua Wu a,b* , Guiyuan Li a

a Cancer Research Institute, Central South University, Changsha, Hunan, China;

Key Laboratory of Carcinogenesis and Cancer Invasion, Ministry of Education;

Key Laboratory of Carcinogenesis, Ministry of Health

b The Center for Skull Base Surgery and Neurooncology, Hunan Province, P.R. China

c Institute of Biotechnology, Guilin Medical College, Guangxi Province, P.R. China

PMID: 23252827

Abstract   

Many microRNAs reside in clusters in the genome, are generally similar in sequence, are transcribed in the same direction, and usually function synergistically. The miR-183/96/182 cluster is composed of 3 miRNA genes, and increased expression of miR-183, 96 and 182 are implicated in glioma carcinogenesis. Knockdown of individual components or of the entire miR-183/96/182 cluster inhibits the survival of glioma cells by regulating the ROS-induced apoptosis pathway. Furthermore, inhibition of the miR-183/96/182 cluster induced ROS-mediated AKT/survival independent of three target genes FGF9, CPEB1, and FOXO1, and inhibition of the miRNA cluster induced p53/apoptosis signaling, which was dependent on these same genes. In addition, knockdown of the miR-183/96/182 cluster enhanced the anticancer effect of Temozolomide on glioma cells by the ROS-mediated apoptosis pathway. Therefore, the miR-183/96/182 cluster may be a pleiotropic target for glioma therapy.

Key words: Glioma, microRNA, miR-183, miR-182, miR-96, AKT, P53, Temozolomide, Apoptosis, Mitochondrial membrane potential

PMID: 23252827

 

Supplement: 

Human miRNA gene clustering is significantly higher than what is expected at random. The coordinate expression of the members of the mouse miRNA-183/96/182 cluster has been demonstrated to play an important role in sensorineural fates in the mouse inner ear and in the maintenance and survival of hair cells and post-mitotic photoreceptors of the retina. The human miR-183/96/182 cluster is overexpressed in several tumors, and this overexpression is a good marker for bladder cancer, prostate cancer and urinary cytology. The pleiotropic effects of the miR-183/96/182 cluster converge to regulate cell survival, proliferation and migration in medulloblastomas. However, the effects of their coordinate expression on mechanisms of tumorigenesis and the progression of gliomas are not well known.

We provide evidence that the miR-183/96/182 cluster is highly expressed and promotes cell proliferation in gliomas by regulating the ROS-induced apoptosis pathway. Our data indicate that each individual miRNA within this enigmatic cluster has distinct inhibitory properties, and the combined biological effects of all three miRNAs as a unit are especially significant because they have the same directional transcription and highly conserved “seed sequences”.

miRNAs, as posttranslational regulatory factors, are involved in the cell survival, proliferation and apoptosis by regulating expression of its target genes. Here, we confirm that FGF9 and CPEB1 are common targets of the miR-183/96/182 cluster. FGF9 is a potent mitogen and induces MAPK and mTOR phosphorylation, which are independent of phosphatidylinositol 3-kinase and Akt. CPEB1 is a sequence-specific, translational regulatory RNA-binding protein, and CPEB-regulated translation is a key process involved in insulin signaling that results in AKT phosphorylation, CPEB-regulated human cellular senescence, energy metabolism, and p53 mRNA translation. FOXO1 is a verified target of the miR-183/96/182 cluster, and Forkhead box O (FoxO) transcription factors are downstream targets of the serine/threonine protein kinase B (PKB)/Akt. Our data show that the miR-183/96/182 cluster could inhibit the expression of FGF9, CPEB1 and FOXO1 at the post-transcriptional level.

ROS are known to modulate a variety of cellular functions, such as cancer cell biology.   Modulating the regulatory mechanisms of ROS generation is a useful strategy to destroy cancer stem cells. Additionally, our findings highlight a potential role for the miR-183/96/182 cluster in the process of ROS accumulation in glioma cells, and a significant induction of apoptosis was found by inhibiting the major components of the miR-183/96/182 cluster. Treatment with an ROS inhibitor, NAC, or interference with endogenous expression of FGF9, CPEB1 and FOXO1 relieved the effect of knockdown of the major components or of a pool of components of the miR-183/96/182 cluster on ROS production, which suggested that inhibition of the miR-183/96/182 cluster promoted ROS production to induce apoptosis by targeting FGF9, CPEB1 and FOXO1.

 Two of the most influential signal transduction pathways that are activated by ROS are those involving AKT and P53 signaling. ROS signaling appears to be triggered by activation of the mitochondria-dependent cell death pathway through the AKT pathways, whereas p53 mediates ROS-induced antiproliferative actions and early senescence or apoptosis. Our results also indicated that inhibition of the miR-183/96/182 cluster induced cell apoptosis through the ROS-mediated AKT and P53 pathway, but inhibition of the miR-183/96/182 cluster induced ROS-mediated AKT/apoptosis signaling independent of its three target genes: FGF9, CPEB1 and FOXO1. However, deletion of the clusters induced ROS-mediated P53/apoptosis signaling, and this action was dependent on FGF9, CPEB1 and FOXO1.

Temozolomide (TMZ) is an oral alkylating agent that is widely used in the treatment of refractory glioma. However, poor cancer cell penetration and drug resistance limit the efficacy of this drug. miRNA, as a peiotropic therapeutic targets, could influence sensitivity of human glioma cells to TMZ. We found that knockdown of the miR-183/96/182 cluster could inhibit proliferation, and increased TMZ induced ROS production and apoptosis ability in glioma. Therefore, we speculated that knockdown of the miR-183/96/182 cluster increased the TMZ chemsensitivity by inducing the apoptosis of glioma cells by the ROS-mediated apoptosis pathway. Token together, knockdown of the miR-183/96/182 cluster may enhance the anticancer effect of TMZ on gliomas.

 

Acknowledgements: This study was supported by grants from the National Science Foundation of China (81171932), the Hunan Province Natural Sciences Foundations of China (11JJ1013).

Contact: Minghua Wu, Cancer Research Institute, Central South University, Changsha 410078, Hunan, P.R.China. Tel: 86-731-82355401. Fax: 86-731-82355401. E-mail: wuminghua554@aliyun.com

 

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