Abstract
In the last decade, one of the most important trends of modern science is the search of the biomarkers, which would have high sensitivity and specificity for non-invasive diagnostics of cancer diseases. Immunological methods are not a well established practice in cancer diagnostics because of low specificity of currently used tumor markers. The study of free - circulating nucleic acids in plasma and serum of cancer patients represents a promising direction of modern molecular diagnostics. Free - circulating nucleic acids include DNA, RNA, microRNA, viral DNA / RNA and mitochondrial DNA. In this case, free-circulating nucleic acids can be present both in the free form and in the supramolecular nucleoprotein complexes. However, many aspects related to the biogenesis of free-circulating nucleic acids, as well as their role in the mechanism of carcinogenesis, are still not clear. This review focuses on the biological properties of free - circulating nucleic acids, biogenesis, their role in the pathogenesis of cancer and the possibility of using free - circulating nucleic acids as biomarkers in the diagnosis of cancer. Key words: free circulating nucleic acids, free circulating DNA, microRNA, mitochondrial DNA, cancer, biomarkers.