Aberrant expression of microRNA in gliomas: Molecular mechanisms, functional consequences and clinical significance

Coordinator:		Dr.rer. nat. Marietta Wolter                                                                   Dr. Kai Stühler
Institution:		Neuropathologie, Universitätsklinik Düsseldorf                           Ruhr-Universität Bochum
Homepage:		http://www.uniklinik-duesseldorf.de/neuropathologie

MicroRNAs (miRNAs) are small, single-stranded, non-coding RNA molecules that play a major role in the negative regulation of gene expression by translational inhibition or destabilization of mRNAs. A specific miRNA can down-regulate multiple target genes simultaneously and therefore, miRNAs serve as global regulators of gene expression, e.g. in developmental and apoptotic pathways, as well as in cell proliferation. MiRNAs are abundant in the nervous system, where they have key roles in development and are likely to be important mediators of plasticity. MiRNAs are not only involved in developmental processes but play an important role in the initiation and progression of cancer. Thereby miRNA genes can function either as classic tumor suppressors or as tumor promoters (oncogenes).  In this project we want to analyse a series of 120 human primary brain tumors for the expression of 360 miRNAs by a real-time expression approach. Differentially expressed miRNAs are then characterized on molecular as well as functional levels. To identify molecular mechanisms involved in aberrant miRNA expression in gliomas, the corresponding genes will be studied for genetic alterations by direct sequencing. In addition, hypermethylation of CpG-rich 5´-genomic sequences will be identified by sequencing of bisulfite-modified genomic DNA. The function of selected miRNAs will be investigated by the transfection of synthetic miRNA molecules into glioma cells and the phenotypic effects of these genetic manipulations on the viability, proliferation, clonogenicity, invasion and migration of glioma cells will be determined by the appropriate cell biological assays. To analyse the effects of selected miRNAs on tumorigenicity in vivo, we will subcutaneously inject glioma cells stably transfected with the synthetic miRNA molecules into nude mice, determine the development and size of tumors and compare these parameters to the corresponding controls. In addition, we want to identify target genes of selected glioma-associated miRNAs on the mRNA as well as protein level in order to characterize important signal pathways, which are deregulated by the aberrant expression of miRNAs. In this way we hope to present  promising new candidates for an improved molecular diagnostic and cancer therapy of human brain tumors.