Post by Bozur on Jul 4, 2005 0:39:02 GMT -5
Papers Find Genetic Link to Growth of Tumors
By Andrew Pollack
New York Times
June 9, 2005
A recently discovered genetic mechanism appears to play an important role in the development of cancer, scientists are reporting today, in findings that may eventually lead to new ways to diagnose and treat the disease.
The discoveries "change the landscape in cancer genetics," Dr. Paul S. Meltzer of the National Human Genome Research Institute wrote in a commentary in the journal Nature, which is publishing three papers on the findings today.
Other scientists cautioned that the new findings merely added detail to the already complex picture of how tumors arise and grow.
The findings concern micro-RNA's, which are tiny snippets of genetic material that help dampen the activity of other genes. The material was discovered in the early 1990's, in the roundworm, and in recent years scientists have been finding them everywhere, including at least 200 in human cells.
The mere discovery has altered views of RNA's importance in regulating the working of genes. The previous view was that genes, which are made of DNA, are the recipes for protein, which make up much of the structure of cells and perform most of the functions. In this scheme, RNA, a sort of chemical cousin of DNA, acted mainly as a messenger dispatched by DNA to carry the recipe for a protein to the cell's protein-making machinery.
But with micro-RNA's, the RNA itself is the end product of a gene, not merely an intermediate product on the way to making a protein. These RNA snippets, made up of only 20 to 25 letters of the genetic code, help control the activity of genes that make proteins.
But in most cases the specific function of the snippets has not been found. The cancer papers are a start in that direction.
In one paper, scientists at the Cold Spring Harbor Laboratory, the University of North Carolina and the Memorial Sloan-Kettering Cancer Center found that a particular set of micro-RNA's might help cause B cell lymphoma, a blood cancer.
The scientists genetically altered mouse blood stem cells to make the micro-RNA's more active. When the cells were then put into mice, the animals developed lymphomas that could be traced to the altered cells. The scientists also found that the micro-RNA's were overly active in human tumor biopsies.
"This is perhaps the first example that a gene that doesn't produce any protein at all can contribute to cancer," said Dr. Gregory J. Hannon, a professor at Cold Spring Harbor and a senior author of the paper.
In a second paper, scientists at Johns Hopkins, led by Dr. Joshua T. Mendell, found evidence that a well-known cancer-promoting gene called c-Myc activates six micro-RNA's.
The third paper found that patterns of activity of the 200 or so known human micro-RNA's might be used to distinguish healthy cells from tumor cells, or one type of tumor from another.
The technique may prove useful in diagnosing the small fraction of tumors that cannot be diagnosed clearly, often because they are found after they have spread from their original site, said Dr. Todd R. Golub, the senior author, who is at the Dana-Farber Cancer Institute and the Broad Institute at the Massachusetts Institute of Technology and Harvard.
Scientists generally believe that cancers are formed by an accumulation of gene mutations that allows cells to start growing in an uncontrolled way. In some cases, however, the cause is not mutations of a gene but rather the gene's being turned on or off inappropriately. Micro-RNA may be yet a new mechanism.
"It's all more complicated than we'd like it to be," Dr. Golub said. Indeed, while some micro-RNA's may help cause cancer, there is evidence that others may help suppress it.
Scientists and federal officials are planning a "Human Cancer Genome Project" to try to determine all the genetic changes linked to cancer. The project could easily be modified to look at micro-RNA's, said Dr. Harold Varmus, a planner of the project and the president of Sloan-Kettering.
A better understanding of how tumors form and grow could lead to new treatments. It might be possible, for instance, to turn off micro-RNA's that contribute to tumor growth.
Scientists are already taking advantage of a phenomenon called RNA interference, which is closely related to micro-RNA's. They are synthesizing short pieces of RNA and using them to turn off genes in animals and cells as a way to determine the genes' functions. Some are developing drugs that use short pieces of RNA to treat eye degeneration, viral infections and other diseases.
Another paper being published in Nature suggests that micro-RNA's help regulate stem cell division.
"What you're going to find is you have these guys sticking their fingers in a lot of different pies," Dr. Hannon said, "that a lot of regulatory networks might be regulated by micro-RNA's."
NATIONAL DESK | June 9, 2005, Thursday $
Papers Find Genetic Link To Growth Of Tumors
By ANDREW POLLACK (NYT) 856 words
By Andrew Pollack
New York Times
June 9, 2005
A recently discovered genetic mechanism appears to play an important role in the development of cancer, scientists are reporting today, in findings that may eventually lead to new ways to diagnose and treat the disease.
The discoveries "change the landscape in cancer genetics," Dr. Paul S. Meltzer of the National Human Genome Research Institute wrote in a commentary in the journal Nature, which is publishing three papers on the findings today.
Other scientists cautioned that the new findings merely added detail to the already complex picture of how tumors arise and grow.
The findings concern micro-RNA's, which are tiny snippets of genetic material that help dampen the activity of other genes. The material was discovered in the early 1990's, in the roundworm, and in recent years scientists have been finding them everywhere, including at least 200 in human cells.
The mere discovery has altered views of RNA's importance in regulating the working of genes. The previous view was that genes, which are made of DNA, are the recipes for protein, which make up much of the structure of cells and perform most of the functions. In this scheme, RNA, a sort of chemical cousin of DNA, acted mainly as a messenger dispatched by DNA to carry the recipe for a protein to the cell's protein-making machinery.
But with micro-RNA's, the RNA itself is the end product of a gene, not merely an intermediate product on the way to making a protein. These RNA snippets, made up of only 20 to 25 letters of the genetic code, help control the activity of genes that make proteins.
But in most cases the specific function of the snippets has not been found. The cancer papers are a start in that direction.
In one paper, scientists at the Cold Spring Harbor Laboratory, the University of North Carolina and the Memorial Sloan-Kettering Cancer Center found that a particular set of micro-RNA's might help cause B cell lymphoma, a blood cancer.
The scientists genetically altered mouse blood stem cells to make the micro-RNA's more active. When the cells were then put into mice, the animals developed lymphomas that could be traced to the altered cells. The scientists also found that the micro-RNA's were overly active in human tumor biopsies.
"This is perhaps the first example that a gene that doesn't produce any protein at all can contribute to cancer," said Dr. Gregory J. Hannon, a professor at Cold Spring Harbor and a senior author of the paper.
In a second paper, scientists at Johns Hopkins, led by Dr. Joshua T. Mendell, found evidence that a well-known cancer-promoting gene called c-Myc activates six micro-RNA's.
The third paper found that patterns of activity of the 200 or so known human micro-RNA's might be used to distinguish healthy cells from tumor cells, or one type of tumor from another.
The technique may prove useful in diagnosing the small fraction of tumors that cannot be diagnosed clearly, often because they are found after they have spread from their original site, said Dr. Todd R. Golub, the senior author, who is at the Dana-Farber Cancer Institute and the Broad Institute at the Massachusetts Institute of Technology and Harvard.
Scientists generally believe that cancers are formed by an accumulation of gene mutations that allows cells to start growing in an uncontrolled way. In some cases, however, the cause is not mutations of a gene but rather the gene's being turned on or off inappropriately. Micro-RNA may be yet a new mechanism.
"It's all more complicated than we'd like it to be," Dr. Golub said. Indeed, while some micro-RNA's may help cause cancer, there is evidence that others may help suppress it.
Scientists and federal officials are planning a "Human Cancer Genome Project" to try to determine all the genetic changes linked to cancer. The project could easily be modified to look at micro-RNA's, said Dr. Harold Varmus, a planner of the project and the president of Sloan-Kettering.
A better understanding of how tumors form and grow could lead to new treatments. It might be possible, for instance, to turn off micro-RNA's that contribute to tumor growth.
Scientists are already taking advantage of a phenomenon called RNA interference, which is closely related to micro-RNA's. They are synthesizing short pieces of RNA and using them to turn off genes in animals and cells as a way to determine the genes' functions. Some are developing drugs that use short pieces of RNA to treat eye degeneration, viral infections and other diseases.
Another paper being published in Nature suggests that micro-RNA's help regulate stem cell division.
"What you're going to find is you have these guys sticking their fingers in a lot of different pies," Dr. Hannon said, "that a lot of regulatory networks might be regulated by micro-RNA's."
NATIONAL DESK | June 9, 2005, Thursday $
Papers Find Genetic Link To Growth Of Tumors
By ANDREW POLLACK (NYT) 856 words