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Genetic disorder helps protect from cancer
Down syndrome abnormality can decrease colon cancer rates
Issue date: 2/14/08
In an unexpected new experiment, scientists from the Hopkins School of Medicine and colleagues at Ohio State University have shown that mice with a relatively common chromosomal abnormality have a decreased rate of intestinal cancer.
The genetic condition, trisomy 21, occurs when an extra copy of chromosome 21 is inherited from one parent. In humans, this causes Down syndrome, a genetic childhood disorder in which patients have three copies of chromosome 21 rather than a normal pair.
Down syndrome has several trademark symptoms in humans, including characteristically flat facial features, almond-shaped eyes, heart problems and mental retardation.
These characteristics are all products of the genetic trisomy and therefore over-expression of genes on chromosome 21. Usually, this over-expression has drastic, and often tragic, consequences.
However, this study from the laboratory of Roger Reeves has shown that in mouse models, trisomy 21 actually seems to decrease the rate of intestinal cancer formation and growth, despite inconclusive studies in humans over the last 50 years. The reduction is substantial, reaching up into the 60th percentile range in some cases.
The team proposes that the reason for this unexpected and slightly paradoxical benefit of the trisomy of chromosome 21 is that one or more of the genes that gets over-expressed, in particular the gene Ets2, has a repressive effect on tumor growth.
Ets2 is of particular interest to scientists because Ets2 over-expression due to trisomy is thought to cause increased production of an abnormal Ets2 protein, which is good news: The normal Ets2 protein has previously been thought of as a "pro-cancer" protein.
The mouse model of intestinal cancer used in this experiment demonstrates how tumors are often caused by a faulty or mutated gene that is related to a gene that causes colon cancer in humans.
If it is shown that Ets2 works directly to repress tumor formation, scientists could study the manner in which Ets2 works in order to create an analog treatment in human cases of intestinal cancer. They have already started to do so.
With the knowledge gained in this study, and with further verification, it is possible that someday there could be a pharmaceutical preventative for cancer using the idea that certain genes, through over-expression, can decrease the incidence and growth rate of tumors.
The genetic condition, trisomy 21, occurs when an extra copy of chromosome 21 is inherited from one parent. In humans, this causes Down syndrome, a genetic childhood disorder in which patients have three copies of chromosome 21 rather than a normal pair.
Down syndrome has several trademark symptoms in humans, including characteristically flat facial features, almond-shaped eyes, heart problems and mental retardation.
These characteristics are all products of the genetic trisomy and therefore over-expression of genes on chromosome 21. Usually, this over-expression has drastic, and often tragic, consequences.
However, this study from the laboratory of Roger Reeves has shown that in mouse models, trisomy 21 actually seems to decrease the rate of intestinal cancer formation and growth, despite inconclusive studies in humans over the last 50 years. The reduction is substantial, reaching up into the 60th percentile range in some cases.
The team proposes that the reason for this unexpected and slightly paradoxical benefit of the trisomy of chromosome 21 is that one or more of the genes that gets over-expressed, in particular the gene Ets2, has a repressive effect on tumor growth.
Ets2 is of particular interest to scientists because Ets2 over-expression due to trisomy is thought to cause increased production of an abnormal Ets2 protein, which is good news: The normal Ets2 protein has previously been thought of as a "pro-cancer" protein.
The mouse model of intestinal cancer used in this experiment demonstrates how tumors are often caused by a faulty or mutated gene that is related to a gene that causes colon cancer in humans.
If it is shown that Ets2 works directly to repress tumor formation, scientists could study the manner in which Ets2 works in order to create an analog treatment in human cases of intestinal cancer. They have already started to do so.
With the knowledge gained in this study, and with further verification, it is possible that someday there could be a pharmaceutical preventative for cancer using the idea that certain genes, through over-expression, can decrease the incidence and growth rate of tumors.
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