**1. Introduction**

Glioblastomas (GBMs) are the most common and intractable primary neoplasms of the central nervous system (CNS). Gross total surgical excision followed by radiotherapy up to a total dose of 60 Gy was the only accepted GBM management for decades because no chemothera‐ peutic agents significantly improved the survival of patients with GBM until the introduction of temozolomide, an oral alkylating agent (1). Despite aggressive treatments, recurrence is inevitable and fatal in GBMs. In a recent clinical study, the median survival was up to approximately 20 months and the two-year survival rate was approximately 30~40% (2, 3). Therefore, more efforts need to be made to change the poor prognosis of patients with GBM.

MicroRNAs (miRNAs) are small (18–24 nt), noncoding RNAs that are transcribed from the intergenic or intronic regions of DNA. miRNAs regulate the expression levels or translational levels of messenger RNAs (mRNAs) post-transcriptionally and affect to various biological processes, such as cell proliferation, cell survival, differentiation, and metabolism (4). Primary miRNAs (pri-miRNAs), transcribed from DNA and have short stem-loop structures (SLSs), are processed into premature miRNAs (pre-miRNAs) and then finally processed into mature miRNAs (5). A single miRNA has many targets of mRNAs, binding its target sites mostly in the 3′ untranslated region (3′-UTR) of the mRNA. The main function of miRNAs is to down‐ regulate gene expression, and miRNAs can function either as tumor suppressors or as oncogenes (6).

A number of miRNAs are reported to display aberrant expression patterns in GBMs (7). In 2005, the first miRNA dysregulation was identified in GBMs (8). miR-21 detected by northern blot was overexpressed in GBM tissues when compared with non-neoplastic control tissues. On the other hand, a systemic screen for miRNA aberrations by miRNA microarray in GBM was performed by other researchers (7). Using miRNA microarray analysis, we previously reported that miR-10b, miR-21, miR-183, miR-92b, and miR-106b are highly expressed in GBMs compared with normal brain tissue (9). Several other reports have also identified these miRNAs as being upregulated in GBMs (8). Recently, we reported that the expression of miR-183 involved in HIF-1α expression and its downstream molecules (10). Since then, it has been documented that miRNA dysregulation could play an important role in development and progression.
