Molecular Testing of Urine: Catching DNA on the Way Out

Abstract

There has been much recent interest in the potential diagnostic use of DNA in plasma and serum for cancer testing (1), prenatal diagnosis (2), and transplantation monitoring (3). It has also been demonstrated that circulating DNA appears to be cleared very rapidly from the circulation (4). The exact mechanism of clearance, however, has remained incompletely understood. In this issue of the Journal, Botezatu et al. (5) describe interesting results indicating that the kidney plays a role in the clearance of plasma DNA and that, excitingly, a proportion of the DNA is excreted in sizes detectable by molecular techniques such as PCR. Botezatu et al. (5) began their investigation by demonstrating that mice injected with either purified bacteriophage DNA or irradiated Raji cells excreted detectable amounts of DNA derived from the injected materials. They went on to show that their observations could also be extended to humans by demonstrating the presence of male DNA in the urine of women transfused with male blood and in women pregnant with male fetuses (5). These authors continued their line of investigation by showing that tumor-associated K- ras mutations were detectable in the urine of pancreatic and colorectal carcinoma patients. Overall, their results have opened up the possibility that urinary DNA analysis may have diverse clinical applications, ranging …