Powerful new test detects 15% of cancers | COSMOS magazine

Powerful new test detects 15% of cancers
Tuesday, 24 November 2009
by Gemma Black

Cosmos Online

SYDNEY: One in six cancers, including some of the most aggressive and lethal varieties, could soon be traceable in a simple blood test with the discovery of an abnormal type of DNA.

The technology, detailed this week in the journal Nature Biotechnology, could also lead to improved survival rates for patients and shorter waiting times for test results.

"I'm excited about this discovery and the test, as I am optimistic that it will soon start to make a difference to patients," said Jeremy Henson, lead researcher behind the discovery at the Children's Medical Research Institute (CMRI) in Sydney, Australia.

Two mechanisms

There are two types of mechanism that allow cancer cells to become immortal and multiply indefinitely at the expense of other, healthy cells. One of the mechanisms, called 'alternative lengthening of telomeres' (ALT) is used by 15 % of cancers, most commonly bone, brain and connective tissue cancer, as well as some breast and lung cancers.

The presence of cells using this ALT mechanism can now be detected in a blood test, thanks to the discovery of abnormal hoops of single stranded DNA, called C-circles, which are only detectable in those cells. The finding is also significant because patients with ALT-type cancers generally have a shorter life expectancy, with an average prognosis of five to seven years.

"Our C-circle test is the first for measuring the amount of ALT activity," said Henson. "The process is definitive and only takes a few days, whereas previously the process took two to three months and mostly we were still uncertain by the end," he said.

Protective caps

Telomeres are like protective caps fitted onto the ends of DNA strands inside chromosomes. As cells divide with age, the telomeres reduce in length, ageing both the cells and the organism. Malignant cancer cells using the ALT mechanism, however, are able to maintain their length, thus becoming 'immortal'.

The ability to detect cells using the ALT mechanism by means of a blood test will allow scientists to not only test for cancers, but to better monitor cancer progress, the effectiveness of treatment and perhaps even individualise a treatment specific to ALT-type cancers.

"The survival of patients with bone cancer could be improved by a test to determine how well the chemotherapy is working," said Henson. "If it is not working it can be altered to a more aggressive regime. Currently this cannot be determined until the tumour is resected at surgery after chemotherapy, and by then it is too late."

According to Henson, any future treatments for cancer will target these 'immortality mechanisms' as they are vital for the survival of cancer cells, but not required for normal, healthy cells.

"Remarkable finding"

"This test is a remarkable finding because it will translate directly to patient diagnosis and treatment," said Jennifer Stow, a molecular cell biologist from the University of Queensland, in Brisbane.

"The beauty of this test is that it's so easy to do," she said. "It's not often that we get such applicable findings coming out of cancer research."

Once the initial findings have been tested in a larger study, a blood test to detect abnormal circular DNA could become available to high-risk patients within a year, the experts said.