[Characteristics and diagnostic applications of circulating cell-free DNA in colorectal cancer]

The incidence and mortality of colorectal cancer (CRC) are considerably high in Central European countries, it is the second most common cancer in both men and women in Hungary with 10,000 newly registered patients per year. These data indicate the necessity of new screening methods that are more comfortable for patients, hence the compliance can be increased. Cell-free DNA (cfDNA) level in blood is elevated in certain physiological conditions, such as pregnancy or high physical activity. Furthermore, cfDNA concentration alterations can also be detected in some pathological processes; increased cfDNA amount was observed in autoimmune and inflammatory diseases, as well as in various cancers including CRC. Numerous studies about origin, function, and mechanism of cfDNA can be found in the scientific literature. In this review, we aimed to describe the quantitative and qualitative changes of cfDNA, to present its functions, and to provide an overview of the available diagnostic applications for CRC. CfDNA can be released to the circulatory system via apoptosis, necrosis or by direct secretions by living cells. In cancer patients, cfDNA can originate from healthy and cancer cells, hence genetic (e.g. mutations in APC, KRAS, BRAF) and epigenetic (e.g. methylation in SEPT9, SFRP1) alterations of tumor cells can be examined in cfDNA fraction. Several high-throughput, sensitive and even automated methods are available providing opportunity to perform standardized sample preparation and to analyse biomarker candidates quantitatively. These enhancements can help to develop alternative screening methods that can be easily integrated into the clinical practice and can contribute to early cancer detection. Orv Hetil. 2019; 160(30): 1167-1177.