**The Roles of MicroRNAs in Glioblastoma Biology and Biomarker**

Takashi Sasayama, Kazuhiro Tanaka and Eiji Kohmura

Additional information is available at the end of the chapter

http://dx.doi.org/10.5772/63243

#### **Abstract**

heterogeneity is an active process maintained by a mutant EGFR-induced cytokine circuit in glioblastoma. Genes Dev. 2010;24:1731–1745. DOI: 10.1101/gad.1890510 [89] Cairncross G, Wang M, Shaw E, Jenkins R, Brachman D, Buckner J, Fink K, Souhami L, Laperriere N, Curran W, Mehta M. Phase III trial of chemoradiotherapy for anaplastic oligodendroglioma: long-term results of RTOG 9402. J Clin Oncol. 2013;31:337–343.

[90] Kim YH, Nobusawa S, Mittelbronn M, Paulus W, Brokinkel B, Keyvani K, Sure U, Wrede K, Nakazato Y, Tanaka Y, Vital A, Mariani L, Stawski R, Watanabe T, De Girolami U, Kleihues P, Ohgaki H. Molecular classification of low-grade diffuse

[91] Riemenschneider MJ, Jeuken JW, Wesseling P, Reifenberger G. Molecular diagnostics of gliomas: state of the art. Acta Neuropathol. 2010;120:567–584. DOI: 10.1007/

[92] Basanta D, Scott JG, Rockne R, Swanson KR, Anderson AR. The role of IDH1 mutated tumour cells in secondary glioblastomas: an evolutionary game theoretical view. Phys

Biol. 2011;8:015016. DOI 10.1088/1478-3975/8/1/015016

gliomas. Am J Pathol. 2010;177:2708–2714. DOI: 10.2353/ajpath.2010.100680

DOI: 10.1200/JCO.2012.43.2674

s00401-010-0736-4

26 Neurooncology - Newer Developments

MicroRNAs (miRNAs) are small, noncoding RNAs transcribed from DNA that are 18– 24 nucleotides in length. A single miRNA has the capacity to regulate a large number of target messenger RNAs (mRNAs), and the main function of miRNAs is to downregu‐ late gene expression. A large set of miRNAs is overexpressed or downregulated in various human cancers compared with normal tissues, and gene silencing by miRNAs enhan‐ ces tumor malignancies.

In glioblastomas (GBMs), a number of miRNAs are reported to display aberrant expression patterns, and miRNAs have been shown to strongly influence cell viability, cell proliferation, invasiveness, angiogenesis, metabolism, and microenvironment. Since early findings, the number of studies published on this subject has steadily increased, elucidating numerous interesting miRNA-mediated mechanisms in the tumorigenesis of GBM.

A number of studies have recently suggested that circulating miRNAs could be potential biomarkers for cancer diagnosis. Not only the role of miRNAs in glioma development but also their specificity makes them important candidate biomarkers that could provide important characteristic information about a tumor and improve treatment and prognosis. This review summarizes current progress and future directions in this exciting and steadily expanding field.

**Keywords:** glioblastoma, microRNA, hallmarks, biomarker, circulating

© 2016 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
