A new blood test developed by bioengineers at the University of California, San Diego (UCSD) would not only be able to detect cancer, but also find where in the body the tumor is growing.
The study, published in the March 6 issue of the journal Nature Genetics, could provide a path for doctors to diagnose cancer early on, without having to do invasive procedures.
The discovery happened as a complete accident, said Kun Zhang, a bioengineering professor at the UC San Diego Jacobs School of Engineering and senior author of the study.
“Initially, we were taking the conventional approach and just looking for cancer cell signals and trying to find out where they were coming from," Zhang said.
Most cancer blood tests will screen for DNA released by dying tumor cells, and these tests are promising for detecting traces of tumor DNA in the blood of cancer patients.
However, existing tests do not indicate where that tumor may be in the body.
“Knowing the tumor’s location is critical for effective early detection,” Zhang said.
In this new study, lead by Zhang, the team discovered a new clue in the blood that could detect tumor cells and identify where they are.
As tumors grow in the body, they compete with regular cells for space and nutrients. In the process, the tumor cells will kill off the regular cells. As those cells die, they release their DNA into the bloodstream.
The DNA in the bloodstream could identify the affected tissue, locating the area in the body where the tumor is growing.
"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.
Here's how the new test would work: it would screen for a particular DNA signature using CpG methylation haplotypes. Each tissue can be identified by its unique signature of methylation haplotypes.
To create the new method, the team put together a complete database of CpG methylation patterns of 10 different normal tissues - the liver, intestine, colon, lung, brain, kidney, pancreas, spleen, stomach and blood.
Additionally, the team looked at tumor samples and blood samples from cancer patients at the UC San Diego Moores Cancer Center to create a database of cancer-specific genetic markers.
The team then screened the blood samples from cancer patients, along with blood samples from individuals without cancer. In their screenings, they were looking for signals of the cancer markers and the specific tissue methylation patterns in a dual authentication process.
Next, researchers hope to move to the clinical stage.
“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.
Shicheng Guo, Dinh Diep, Nongluk Plongthongkum, Ho-Lim Fung, Kang Zhang and Kun Zhang contributed to the study.