Cell free DNA: A novel biomarker for clinical diagnosis

Cell free DNAs (cfDNAs) are small fragments of genomic or mitochondrial DNA releasing from cells into the blood stream. The presence of cfDNA in the human circulatory system has been shown for the first time in 1948; however, the potential clinical applications of cfDNA remained unknown until recent progress in detection and quantification of these molecules by sensitive methods. In this paper, we will review the existing literature concerning the potential clinical applications of circulating cfDNA in prenatal diagnosis, detection and monitoring of tumors and other conditions, such as autoimmune disease, stroke, myocardial infarction and transplantation. In prenatal diagnosis, cfDNA technology is used for determination of fetal sex and fetal RhD status and for prenatal diagnosis of aneuploidies and monogenic disorders. In cancer the level of circulating tumor-derived cfDNA and its qualitative characteristics, including tumor specific gene mutations and epigenetic modification are correlated with the stage and grade of disease. Therefore, cfDNA can be used as a specific marker for detection and monitoring of tumors. In the field of organ transplantation, the presence of cfDNA from transplanted-organ in the circulation or urine of recipient patient could serve as a marker of transplant rejection. Finally, in stroke and myocardial infarction, quantification of cfDNAs is used as a marker of cell necrosis.