J Exp Clin Cancer Res. 2012, 31:73.PubMedCrossRef”
“Introduction Glioma is the first commonly diagnosed types of intracranial tumors, accounting for more than 50% among all primary brain tumors [1]. Gliomas can be classified as astrocytomas, oligodendrogliomas, or tumors with morphological features of both two types of tumors above. According to their degrees of malignancy, gliomas are classified from graded I to IV. Glioblastoma, one subtype of aggressive gliomas, is the most common and lethal brain tumor, with widespread invasion in brain, poor differentiation, destruction of normal brain tissue, and resistance to traditional therapeutic approaches [1–3]. selleck screening library Current

options for treatment of glioblastoma include surgical resection of the primary tumor to reduce the tumor size, followed by radiotherapy and adjuvant chemotherapy with temozolomide (TMZ) [4]. However, even with successful surgical resection and subsequent radiotherapy and chemotherapy, the prognosis remains poor, with a median survival of 12–15 months [5]. High tumor recurrence rate and mortality of patients is due to incomplete removal of primary check details tumors after surgery and resistance to chemotherapy. The infiltrating characteristics of glioblastoma make complete removal of primary tumor virtually

impossible, and even cause normal brain tissue damage. Therefore, the limitation of current options for glioblastoma treatment suggests that it is urgently required to study mechanism of chemoresistance regulation of this cancer. MicroRNAs (miRNAs), a class of 22-nucleotide small non-coding RNAs, can regulate gene expression at post-transcriptional level. MiRNAs are evolutionarily conserved and negatively regulate gene expression. They

are transcribed by RNA polymerase II, spliced, and then poly-adenylated to generate primitive miRNAs (pri-miRNAs) [6]. The stem-loop structure of pri-miRNAs can be recognized and cleaved by the nuclear RNase III Drosha to generate hairpin precursor miRNAs (pre-miRNAs). Pre-miRNAs are rapidly exported to the cytoplasm by exportin-5, excised by the cytoplasmic RNase III Dicer to generate a 22-nucleotide miRNA duplex: one Farnesyltransferase strand is a mature miRNA, whereas the other strand (miRNA*) is normally unstable and degraded. The mature miRNAs can suppress target gene expression by interaction with complementary sequences in the 3′-untranslated regions (3′-UTRs) of target mRNAs and trigger translation blockade or mRNA degradation depending on whether it is completely or partially matched with the target genes [7]. Multiple studies have shown that miRNAs are deregulated in various types of human cancers [8], including glioblastoma [9–11], breast cancer [12], lung cancer [13], colon cancer [14], and ovarian cancer [15]. MiRNAs may function as oncogenes or tumor suppressors, and also involve in chemoresistance [15, 16].