Extracellular
nucleic acids (
NAs), both
DNA and
mRNA, have been found to exist in many
biological media, including serum, plasma, saliva, urine, semen, milk and bronchial lavage, as well as cell culture supernatants. Analysis of such
NAs as potential diagnostic, prognostic or predictive
biomarkers for
cancer has indicated that, while these
NAs are detected in both plasma and serum from both healthy individuals as well as those suffering from a broad range of
cancer types, their overall concentrations in the circulation are generally higher in
cancer than in normal conditions. Indeed, the detection of specific mRNAs (by RT-PCR/qPCR and, more recently, by microarrays) has been associated with the presence of
cancer, supporting their potential as useful
biomarkers. Furthermore, it has been proposed that these extracellular mRNAs are not inert, but may have functional relevance. Evidence suggests that such extracellular
NAs also have potential as
biomarkers for a range of other pathological conditions and in forensic science. In conclusion, it seems that the field of extracellular
NAs has great potential to be exploited by the development of minimally-invasive diagnostic, prognostic and predictive assays for
cancer if it is ensured that relevant and adequate controls are included in all studies.