MicroRNA involvement in brain tumors: from bench to bedside.

MicroRNAs (miRNAs), a novel class of small non-coding RNAs, are effective post-transcriptional regulators of gene expression, exhibiting, when altered in human tumors, both oncogenic and tumor suppressive potential. Recently, miRNA involvement in the pathophysiology of brain cancer has been assessed. Aberrant gene expression is the main mechanism of miRNAs dysfunction in cancer, with abnormal expression levels of mature and/or precursor miRNA expression in tumor samples versus normal. MiRNA germline and somatic mutations or polymorphisms in the protein coding messenger RNA targeted by miRNAs may also occur, contributing to cancer predisposition, initiation and/or progression. If present in somatic cells, miRNA alterations may play a role in tumor initiation, while if present in germ line cells they could constitute a cancer predisposing event. MiRNA expression profiling of human tumors has led to the identification of signatures correlated with the tumor diagnosis, staging, progression, prognosis and response to treatment. MiRNA fingerprinting can therefore be added to the diagnostic and prognostic tools used by medical oncologists. Furthermore, new therapeutic strategies involving miRNA silencing or miRNA mimics could be proposed based on the roles of these small non-coding RNAs as oncogenes and tumor suppressors in brain tumors.