[Biogenesis of microRNAs and their role in the development and course of selected hematologic disorders].

MicroRNAs (miRNAs) are a group of small molecules, about twenty nucleotides in length. They are involved in the regulation of gene expression mainly at a posttranscriptional level. This function depends on their complementarity to the 3'UTR regions of mRNAs. MicroRNAs are essential for proper development and functioning of the organism. They are so important because of their participation in such processes as angiogenesis, apoptosis, cell cycle control and oncogenesis. Over thirty percent of human genes are controlled by miRNAs. This indicates the great importance of these molecules. Alterations of numerous cellular processes can be caused by the dysregulation of miRNA expression. Such disturbances are observed in cancer cells, and signatures of microRNA expression are specific to particular types of cancer. It is suggested that miRNAs may serve as diagnostic and prognostic factors in oncologic and hematooncologic disorders. The expression of specific miRNAs can indicate benign or aggressive course of disease. The overall survival or time to treatment are also possible to estimate based on the microRNA expression profile. Knowledge about changes in miRNA expression observed in leukemia patients may enable the selection of appropriate individual therapy. Recent reports indicate that various hematooncologic disorders may be well characterized by microRNAs circulating in plasma or serum. It is of great potential importance, considering the availability of material for analysis, simplicity of diagnostic procedures and shortening of time required to conduct them.