New research shows promise for a blood test that not only identifies cancer but also pinpoints precisely where tumors are growing.
Published in the journal Nature Genetics, the study describes how a specific DNA signature called CpG methylation haplotypes can indicate both the presence and specific location of tumor cells.
Senior study author Kun Zhang of the Jacobs School of Engineering at the University of California-San Diego and colleagues say their findings could offer a noninvasive method for cancer diagnosis.
According to the American Cancer Society, more than 1.6 million new cancer cases will be diagnosed in the United States this year and more than 600,000 people are expected to die from the disease.
In most cases, cancer diagnosis requires a biopsy, whereby a sample of tissue is removed and analyzed for the presence of cancer cells. This new test requires neither surgery, endoscopy, or the use of a needle.
Using DNA from healthy cells
Cancer blood tests are gaining momentum for cancer diagnosis.
These tests work by identifying DNA traces of cancer cells that have broken away from tumors.
At present, however, such tests are unable to provide information on where in the body a tumor is located.
"Knowing the tumor's location is critical for effective early detection," noted Zhang.
For their study, the researchers created a technique that tests for DNA signature CpG methylation haplotypes.
In simple terms, this signature is an indicator of both tumor DNA and the DNA of healthy cells. The team explains that when healthy cells are destroyed by cancer cells, their DNA is released into the bloodstream. This DNA can be used to pinpoint the tissue affected by cancer cells.
"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,” said Zhang.
“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.”
‘A promising strategy’
To reach their findings, the researchers used samples from 10 different healthy tissues – including the liver, brain, lung, intestine, and colon – to produce a database of methylation patterns.
Additionally, the team used blood and tumor samples from cancer patients to create a database of genetic markers specific to cancer.
Next, the researchers analyzed the blood samples of healthy patients and those with tumors.
By searching for cancer- and tissue-specific genetic markers in these blood samples, the team was able to identify the presence and location of tumors.
Zhang notes that further work is needed to “optimize and refine” this technique, but the researchers believe that their study provides proof of concept for a noninvasive diagnostic technique for cancer.
“In summary, methylation haplotyping in plasma is a promising strategy for the early detection of a tumor and its primary growth site, as well as for the continuous monitoring of tumor progression and metastasis to multiple organs,” say the authors.
“With more plasma samples from patients at multiple clearly defined cancer stages and from healthy controls, it is possible to further improve the prediction sensitivity and specificity to a level adequate for clinical testing.”