Thu, Dec 06, 2018 - Page 14 News List

Scientists develop 10-minute test for cancer

The new test uses color-changing fluid to show the likelihood of cancerous cells in a patient’s DNA

By Ian Sample  /  The Guardian

A doctor collects blood from a man in November at a cancer detection and awareness event in Amritsar, India.

Photo: AFP

Scientists have developed a universal cancer test that can detect traces of the disease in a patient’s bloodstream.

The cheap and simple test uses a color-changing fluid to reveal the presence of malignant cells anywhere in the body and provides results in less than 10 minutes.

While the test is still in development, it draws on a radical new approach to cancer detection that could make routine screening for the disease a simple procedure for doctors.

“A major advantage of this technique is that it is very cheap and extremely simple to do, so it could be adopted in the clinic quite easily,” said Laura Carrascosa, a researcher at the University of Queensland.

The test has a sensitivity of about 90 percent, meaning it would detect about 90 in 100 cases of cancer, with 10 percent false positives. It would serve as an initial check for cancer, with doctors following up positive results with more focused investigations.

“Our technique could be a screening tool to inform clinicians that a patient may have a cancer, but they would require subsequent tests with other techniques to identify the cancer type and stage,” Carrascosa said.

The test was made possible by the Queensland team’s discovery that cancer DNA and normal DNA stick to metal surfaces in markedly different ways. This allowed them to develop a test that distinguishes between healthy cells and cancerous ones, even from the tiny traces of DNA that find their way into the bloodstream.

Healthy cells ensure they function properly by patterning their DNA with molecules called methyl groups. These work like volume controls, silencing genes that are not needed and turning up others that are.

In cancer cells, this patterning is hijacked so that only genes that help the cancer grow are switched on. While the DNA inside normal cells has methyl groups dotted all over it, the DNA inside cancer cells is largely bare, with methyl groups found only in small clusters at specific locations.

Writing in the journal Nature Communications, the Queensland team described a series of tests that confirmed the telltale pattern of methyl groups in breast, prostate and colorectal cancer as well as lymphoma. They then showed that the patterns had a dramatic impact on the DNA’s chemistry, making normal and cancer DNA behave very differently in water.

“This is a huge discovery that no one has grasped before,” Carrascosa said.

After a series of experiments, the scientists came up with the new test for cancer. The suspect DNA is added to water containing tiny gold nanoparticles. Though made of gold, the particles turn the water pink. If DNA from cancer cells is then added, it sticks to the nanoparticles in such a way that the water retains its original color. But if DNA from healthy cells is added, the DNA binds to the particles differently, and turns the water blue.

“The test is sensitive enough to detect very low levels of cancer DNA in the sample,” Carrascosa said.

Led by Matt Trau, a professor of chemistry at the University of Queensland, the researchers have run the test on 200 human cancer samples and healthy DNA.

“We certainly don’t know yet whether it’s the holy grail for all cancer diagnostics, but it looks really interesting as an incredibly simple universal marker for cancer, and as an accessible and inexpensive technology that doesn’t require complicated lab-based equipment like DNA sequencing,” Trau said.

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