Role of microRNAs in mechanisms of glioblastoma resistance to radio- and chemotherapy.

Low-grade gliomas and multiform glioblastoma are characterized by highly pronounced anaplasia, malignization, proliferation, and invasiveness; moreover, they are highly resistant to chemo- and radiotherapy. The very low efficiency of traditional approaches in the treatment of patients with glioblastomas is due to the intensive invasive growth of the tumor resulting in deep infiltration of adjacent normal perivascular and nervous tissue and formation of areas of perineural infiltration differently remote from the tumor epicenter. MicroRNAs are key posttranscriptional regulators of gene activities, and their expression is markedly increased in tumors, in particular in gliomas. MicroRNAs have been shown to promote the growth, proliferation, migration, and survival of tumor stem and non-stem cells. However, a population of microRNA possessing antitumor effects is also detected in gliomas. As a rule, the expression of antitumor microRNAs is suppressed in tumors. In this review, we consider microRNAs, their influence on radio- and chemoresistance of gliomas, and prospects for their use as specific agents in targeted therapy of gliomas. The pool of these microRNAs has distinct therapeutic value, because on use in combined therapy it can decrease the resistance of glioma tumor stem cells to existing pharmaceuticals and improve the efficiency of radio- and chemotherapy.