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Vol. LXIII, No. 15
July 22, 2011
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Digest

Cancer Genome Atlas Completes Ovarian Cancer Analysis

Dr. Judith H. Greenberg
An analysis of genomic changes in ovarian cancer has provided the most comprehensive and integrated view of cancer genes for any cancer type to date.

An analysis of genomic changes in ovarian cancer has provided the most comprehensive and integrated view of cancer genes for any cancer type to date. Ovarian serous adenocarcinoma tumors from 500 patients were examined by the Cancer Genome Atlas (TCGA) Research Network and analyses were reported in the June 30 issue of Nature.

Serous adenocarcinoma is the most prevalent form of ovarian cancer, accounting for about 85 percent of all ovarian cancer deaths. TCGA researchers completed whole-exome sequencing, which examines the protein-coding regions of the genome, on an unprecedented 316 tumors. They also completed other genomic characterizations on these tumors and another 173 specimens.

TCGA is jointly funded and managed by the National Cancer Institute and the National Human Genome Research Institute.

“This landmark study is producing impressive insights into the biology of this type of cancer,” said NIH director Dr. Francis Collins. “It will significantly empower the cancer research community to make additional discoveries that will help us treat women with this deadly disease. It also illustrates the power of what’s to come from our investment in TCGA.”

Findings in Mice May Help Curb Obesity, Type 2 Diabetes

Scientists at NIH have uncovered a pathway in mice that allows white fat—a contributor to obesity and type 2 diabetes—to burn calories in a way that’s normally found in brown fat and muscle. The findings appeared in the July 6 edition of Cell Metabolism.

White fat is used to store calories. However, too much white fat (obesity) increases the risk of type 2 diabetes and other diseases. Brown fat generates heat to maintain body temperature and, like muscle, has lots of iron-containing, calorie-burning mitochondria in its cells. Changing white fat into brown fat or muscle is a potential new approach to treating obesity and type 2 diabetes, although the research is a long way from being applicable to people.

The findings were exciting and unexpected, said Dr. Sushil Rane, a researcher at the National Institute of Diabetes and Digestive and Kidney Diseases and the paper’s senior author. “We weren’t looking to have white fat acquire the properties of brown fat, but that’s what we found, with the fat getting browner from increased mitochondria and displaying genes typically expressed in muscle. It was a striking difference.

“Efforts to reduce obesity by dieting are mostly unsuccessful in the long term, so finding ways to prevent excess fat storage is an urgent medical need,” Rane continued. “Our discovery that white fat can be reduced by partially transforming it to brown fat and muscle opens up new avenues to combat the obesity epidemic.”

Balance Tips Toward Environment as Heritability Ebbs in Autism

The largest and most rigorous twin study of its kind to date has found that shared environment influences susceptibility to autism more than previously thought.

The study, supported by NIH, found that shared environmental factors—experiences and exposures common to both twin individuals— accounted for 55 percent of strict autism and 58 percent of more broadly defined autism spectrum disorders (ASD). Genetic heritability accounted for 37 percent of autism and 38 percent of ASD. Random environmental factors not shared among twins play a much smaller role.

Earlier twin studies had estimated the genetic heritability of autism to be as high as 90 percent, due to much lower estimates of concordance— both members of a twin pair having the disorder—in fraternal twins. The new study found such concordance to be four to five times higher. The findings were reported in the July 2011 issue of the Archives of General Psychiatry.

“High fraternal twin concordance relative to identical twin concordance underscores the importance of both the environment and moderate genetic heritability in predisposing for autism,” said Dr. Joachim Hallmayer of Stanford University, a grantee of the National Institute of Mental Health. “Both types of twin pairs are more often concordant than what would be expected from the frequency of autism in the general population. However, the high concordance among individuals who share only half their genes relative to those who share all of their genes implies a bigger role for shared environmental factors.”


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