New test traces DNA origins to monitor transplant rejection
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A new technique that can trace which tissues and organs the DNA in our blood comes from has been reported in the eLife journal. The method, called GETMap, could be used in prenatal screening, to monitor organ transplant rejection or test for cancers that are concealed in the body.

Analysis of circulating free DNA has been shown to be useful for screening for early asymptomatic cancers. As cancer-associated DNA changes are present in a wide range of cancer types, detection of such changes can be used as a universal test for concealed cancers.

Researchers developed Genetic-Epigenetic Tissue Mapping (GETMap) to determine the tissue composition of plasma DNA carrying genetic variants not present in the constitutional genome through comparing their methylation profiles with relevant tissues.

Investigators validated this approach by showing that, in pregnant women, circulating DNA carrying fetal-specific alleles was entirely placenta-derived. In lung-transplant recipients, they showed that, at 72 hours after transplantation, the lung contributed only a median of 17% to the plasma DNA carrying donor-specific alleles and hematopoietic cells contributed a median of 78%. In hepatocellular cancer patients, the liver was identified as the predominant source of plasma DNA carrying tumor-specific mutations.

In a pregnant woman with lymphoma, plasma DNA molecules carrying cancer mutations and fetal-specific alleles were accurately shown to be derived from the lymphocytes and placenta, respectively.

Conclusively, analysis of tissue origin for plasma DNA carrying genetic variants is potentially useful for noninvasive prenatal testing, transplantation monitoring, and cancer screening.