say tumor. A genetic mutation may help doctors diagnose deadly tumors in the brain.
Photo courtesy of Duke PhotoPath
While survival rates for many cancers have improved over the years, brain cancers often remain stubbornly insensitive treatment. Now, researchers are turning to genetic and knocked on a genetic mutation that can be used to distinguish the most deadly brain cancers. The discovery could help doctors diagnose more precisely these devastating tumors.
The most common tumor of the brain, glioblastoma, is also the most deadly. These tumors occur in two forms: primary, in which patients suddenly develop very large and malignant tumors, and secondary glioblastomas, which start as smaller tumors, less aggressive in the brain. Last fall, scientists reported an interesting difference in the genetics of these two tumor types. A particular mutation showed in secondary tumors ( Science , September 4, 08, p. 1807). Patients with the mutation also seem to have a better prognosis than those without it.
The researchers, led by D. Williams Parsons of Johns Hopkins University in Baltimore, Maryland, and Hai Yan of Duke University in Durham, North Carolina, was intrigued because the gene is not previously been implicated in cancer. The gene, called isocitrate dehydrogenase-1 ( IDH1 ) encodes an important enzyme in the cellular metabolism. The researchers decided to sequence more brain tumors to check what types of mutations occurring in the gene IDH1 and their impact on cancer cells.
They sampled the DNA of 445 brain tumor which had been removed from patients at different stages of development. Of these, 170 carried a mutated form of a IDH1 or its cousin gene IDH2 . Most mutated tumors were either secondary glioblastomas and other tumors, less aggressive, confirming the work of last year, the researchers report online this week in The New England Journal of Medicine . Above all, each tumor with a mutant gene had a change of simple letter at about the same location on the gene, which may make it easier to use as a biomarker because it is relatively easy to spot.
Next, the researchers found that in the brain cancer cells in the laboratory, the enzymes that usually produce energy was virtually inactive in the mutant cells relative to normal cells HDI - suggesting that these cells do not metabolize energy as efficiently and have less to develop on. Despite the results of the paper Science and this, Yan said the mutation may not actually be to protect patients. It could just be signaling tumors to grow, but not as aggressive as in primary glioblastomas - but its function is far from clear at this time. This is important because the two types of tumors may look very similar under the microscope, says pathologist Roger McLendon Duke, who also participated in the research. Test for the IDH mutation could allow doctors to diagnose more accurately the disease, Yan said.
Whether the findings will lead to new treatments is not known at this stage, says cancer biologist William Hahn of the Dana-Farber Cancer Institute, in Boston. But just using the mutation as a diagnostic tool would be a boon for the treatment of brain cancer, he said. "We are all hoping that we will have molecular markers to distinguish between tumors that will do well or poorly"
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- http: / /www.sciencemag.org/cgi/content/abstract/1164382
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