Circulating nucleic acids in plasma or serum.

Background: Nucleic acids can be found in small amounts in healthy and diseased human plasma/serum. Higher concentrations of DNA are present in the plasma of cancer patients sharing some characteristics with DNA of tumor cells. Together with decreased strand stability, the presence of specific oncogene or tumor-suppressor gene mutations, microsatellite alterations, Ig rearrangements and hypermethylation of several genes may be detected. Moreover, tumor-related mRNA has been found circulating in the plasma/serum. Conclusions: The results obtained in many different cancers have opened a new research area indicating that circulating nucleic acids might eventually be used for the development of noninvasive diagnostic, prognostic and follow-up tests for cancer.