January 3, 2011
New Attack Used to Treat Brain Tumors
(Ivanhoe Newswire) "“ New insight into the biology of many kinds of less aggressive but lethal brain tumors, or gliomas, opens up a wide variety of possibilities for new therapies, according to this study.
The researchers describe how genetic mutation leads to an abnormal metabolic process in the tumors that could be targeted by drug makers.
"What this tells you is that there are some forms of tumors with a fundamentally altered process," Karl Kelsey, a professor of pathology and laboratory medicine and community health in the Warren Alpert Medical School of Brown and one of the paper's senior authors, was quoted as saying. "This is a really new way to look at potentially modifiable factors in brain tumors."
Scientists have known for a while that a mutation in a gene called IDH is associated with glioma. They've observed that people with gliomas carrying the mutation survive longer than those with a tumor lacking the mutation. What the Brown and UCSF team show in the new study is that the mutation is associated with a consistent pattern of an alteration known as "methylation" of the DNA, which is associated with changes in gene expression. The pattern of methylation in tumors with the IDH mutation usually occurs in metabolic genes, regardless of the tumor's specific type.
Margaret Wrensch, a professor of neurological surgery, epidemiology and biostatistics at UCSF's Helen Diller Family Comprehensive Cancer Center, said what the team found surprising is that DNA from almost all tumors with IDH mutations had the same distinctive methylation pattern. The degree of methylation throughout the genome was unusually high, and the same specific DNA was methylated. "This one mutation is common to a whole subset of brain tumors," Wrensch was quoted as saying. "It's quite unique. It seems to dominate other mutations in the tumor and the epigenetic changes are very uniform."
The researchers hope now that if a drug could inhibit this methylation process in any number of these affected genes, not necessarily just IDH, that might correct the errant metabolism of the tumors and control their growth.
"We know now that there are all these genes related to metabolism that have altered methylation," Brock Christensen, a Brown postdoctoral scholar in pathology and laboratory medicine and a lead author of the paper, which also involved researchers from the University of Minnesota and Dartmouth Medical School, was quoted as saying. "In this suite of genes there might be a much easier target to try to design a therapy for."
The researchers analyzed tumor-by-tumor methylation in scores of samples from the Brian Tumor Research Center at UCSF. They found an unusual correlation between the IDH mutation and methylation in metabolic genes in gliomas of many different names and classifications.
"The strength of the correlation was absolutely stunning," Christensen said. "It's not the kind of thing you see very often in cancer epidemiology, to have almost all of these mutant tumors having the same methylation profile."
The IDH gene has a role in glucose sensing, so the association of the mutation with altered metabolism genes (occurring through enhanced DNA methylation) is reasonable, Christensen said. The researchers are now looking into the role that mutation in IDH plays in perhaps altering other metabolism genes in the cells.
"Gliomas are such a deadly disease, and so little is known about them, that people are pretty excited about this because it is a whole new way in," Kelsey said. "We have a new clue about what to study."
SOURCE: Journal of the National Cancer Institute, published online January 2011