- Cancer blood tests usually work by screening for DNA released by dying tumor cells that help in detecting traces of tumor DNA, but do not indicate where the tumor resides.
- The new blood test could detect cancer early and also help to locate where in the body the tumor is growing.
- This test screens for particular DNA signature called CpG methylation haplotypes that are unique to every tissue in the body and thus helps in detecting location.
A new blood test has been developed that could help in early detection of cancer and also in identifying the location of the tumor growth.
The study by bioengineers from the University of California San Diego, could provide a way to diagnose cancer early, by avoiding invasive surgical procedures like biopsies.
‘The new blood test could aid in early diagnosis of cancer and thus help in avoiding invasive surgical procedures like biopsies.’
Cancer blood tests work by screening for DNA released by dying tumor cells. Though these tests help in detecting traces of tumor DNA in the blood of cancer patients the results do not indicate where the tumor resides.
"Knowing the tumor's location is critical for effective early detection," said Kun Zhang, a bioengineering professor at the UC San Diego Jacobs School of Engineering and senior author of the study.
Unique DNA Signature
Researchers discovered a new clue in blood that could both detect tumor cells and identify the location.
When a tumor takes over a part of the body, it competes with normal cells for nutrients and space, killing them off in the process.
The dying normal cells release their DNA into the bloodstream and that DNA could help identify the affected tissue.
The method screens for a particular DNA signature called CpG methylation haplotypes, which are the addition of methyl groups to multiple adjacent CG sequences in a DNA molecule.
Each tissue in the body has a unique signature of methylation haplotypes and can be identified on the basis of that.
Researchers then screened blood samples from individuals with and without tumors. They looked for signals of the cancer markers and the tissue-specific methylation patterns.
"We made this discovery by accident. Initially, we were taking the conventional approach and just looking for cancer cell signals and trying to find out where they were coming from. But we were also seeing signals from other cells and realized that if we integrate both sets of signals together, we could actually determine the presence or absence of a tumor, and where the tumor is growing," Zhang said.
"This a proof of concept. To move this research to the clinical stage, we need to work with oncologists to further optimize and refine this method," Zhang said.
The findings are published in Nature Genetics
- Kun Zhang et al. Identification of methylation haplotype blocks aids in deconvolution of heterogeneous tissue samples and tumor tissue-of-origin mapping from plasma DNA. Nature Genetics ; (2017) doi:10.1038/ng.3805