An international study that included doctors at Toronto's Hospital for Sick Children appears to shed new light on a particular type of brain tumour in children that often proves deadly.

"We have the potential for a new diagnostic tool for a very aggressive type of brain tumour," said Dr. Annie Huang, senior author of the study in Monday's issue of the journal Cancer Cell.

'[T]here's a possibility that we can slow down the aggressive behaviour of these cells, and therefore give the patient a better clinical outcome.'— Dr. Ching Lau

Because these tumours, known as CNS-PNETs, are extremely rare — there are only two or three found in patients at the large pediatric hospital each year — Huang asked hospitals around the world to contribute samples. In the end, the researchers managed to gather 46 tumours, and found they had good data for 40 of them.

It's the largest collection of this tumour type ever looked at, said Huang, whose team examined the genome of the tumours.

"In normal cells, you always have two copies of DNA, and in tumours they tend to lose or gain parts of DNA," she explained. "And those usually tell you important locations for genes that are sort of driving a tumour process or not, or something that is maybe associated with a tumour."

"What we found was that about a quarter of our tumours had this very unusual area, where it had many copies of this particular area. I say area because it encompassed more than one gene."

Marker for aggressive disease

When the researchers looked closely, they found 34 regular genes, as well as two clusters of a "very newly described class of genes, called microRNAs," she said.

They believe these clusters represent a marker for highly aggressive disease in children under age four, which is typically fatal.

"There are two applications we're looking towards — one of them is using this as a diagnostic marker to pick up this group of highly aggressive tumours," said Huang. "And then secondly, my lab is interested in developing therapies against this specific type of molecule."

In terms of diagnosis, though, it would not be good news for a family to learn their child has this particular form of brain cancer.

"Because we put children through treatment that could potentially kill them, [we] have to be cognizant of 'do no harm,' and if we know up front that we can't offer anything that even has a remote chance of success, why put the family through hell?"

"Sometimes they only have six months, and if you keep them in hospital for six months, you've achieved nothing."

Dr. Ching Lau of Baylor College of Medicine in Houston also noted that the abnormality seems to be associated with poorer clinical outcomes.

"Perhaps if we can neutralize the effects of these microRNAs in the tumour cells, there's a possibility that we can slow down the aggressive behaviour of these cells, and therefore give the patient a better clinical outcome," said Lau, a co-author of the study.