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Scientists Identify Genetic Defects Responsible For Deadliest Cancers


Scientists have identified a host of genetic defects that are responsible for two of the most deadly cancers - brain and pancreatic cancers. As VOA's Jessica Berman reports, investigators say their findings will lead to early methods of diagnosis for cancers for which there is currently no cure.

The most common form of brain cancer, known as glioblastoma multiforme, and pancreatic cancer carry a bleak prognosis. Only five percent of patients diagnosed with either disease are alive five years later.

Cancer researcher Paula Kiberstis is senior editor of the journal Science, which this week published two papers describing the discovery of several genetic abnormalities that are responsible for the two cancers.

Kiberstis says the findings may help answer two fundamental questions.

"After receiving a cancer diagnosis, a patient typically asks his or her physician two questions: Can you treat my cancer and what's my prognosis?," said Paula Kiberstis.

Kiberstis says the latest discoveries may ultimately improve the outlook for cancer patients.

In a comprehensive study looking for clues into the cause of glioblastoma and pancreatic cancer, two teams lead by researchers at the Howard Hughes Medical Institute and the Ludwig Center at The Johns Hopkins University in Maryland scoured 20,000 genes in 46 patients with pancreatic and brain cancer.

The researchers narrowed the culprits to about a dozen regulatory processes, or pathways, controlled by defective genes in about each tumor type.

In pancreatic cancer, the researchers linked the mutations to between 67 and 100 percent of pancreatic cancers.

Researchers were also surprised to discover a new mutation in a gene, called IDH1, not previously associated with brain cancer.

Because people with the genetic defect tend to live longer, the investigators now say glioblastoma is two diseases that could lead to two different ways to treat the disease.

But while there were similarities among tumor types, investigators found that the combination of genes of each cancer patient in the studies was unique, making a cure for either pancreatic or brain cancer unlikely anytime soon.

Victor Velculescu is a professor of medicine at The Johns Hopkins University and co-researcher of the brain cancer study.

"Now at least I think we know what the enemies are and it will take a long time to take advantage of this," said Victor Velculescu. "But it at least provides a way forward."

Howard Hughes Medical Institute investigator Bert Vogelstein, a key researcher in the cancer studies, says the work will make it possible to identify genetic markers that contribute to the development of glioblastoma and pancreatic cancer.

In both diseases, experts say there are 70 genes that are hyperactive, making them potentially good targets for early diagnosis and screening.

Vogelstein says the history of medicine shows prevention, not therapy, is the best way control diseases.

"We still can't cure polio but it hardly ever occurs," said Bert Vogelstein. "And with cancer there's a special opportunity because you don't really have to prevent it. You just have to detect it before it metastasizes [spreads]. And nearly everyone can be cured by straightforward surgery."

Last year, Vogelstein and his colleagues found a similarly complex genetic landscape for breast and colon cancer.

The findings set back the research goal of individualized medicine, identifying as many cancer-causing mutations as possible and targeting drugs for that individual.

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