Scientists develop new blood test to detect cancer at early stage

A new blood test has been developed by scientists which can detect cancer and locate where the tumour is growing. The test provies a potential alternative to invasive surgical procedures like biopsies. When a tumour starts to take over a part of the body, it competes with normal cells for nutrients and space, killing them off in the process, according to researchers from the University of California, San Diego in the US.

As normal cells die, they release their DNA into the blood stream and that DNA could identify the affected tissue. "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 Kun Zhang, a professor at UC San Diego. "

But we were also seeing signals from other cells and realised that if we integrate both sets of signals together,we could actually determine the presence or absence of atumour, and where the tumour is growing," Zhang added.

Researchers put together a database of the complete CpGmethylation patterns of 10 different normal tissues (liver,intestine, colon, lung, brain, kidney, pancreas, spleen, stomach and blood).

They analysed tumour samples and blood samples from cancer patients to put together a database of cancer-specific genetic markers. Blood samples from individuals with and without tumours were screened.

They looked for signals of the cancer markers and the tissue-specific methylation patterns. The test works like a dual authentication process. The combination of both signals, above a statistical cut off, is required to assign a positive match, researchers said. The study was  published in the journal Nature Genetics.