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Cancer and Down syndrome article

Posted Jun 02 2009 4:31pm

Very interesting findings in the medical community about Down syndrome and cancer. My only complaint about the article, there are a few times that the author could have used people first language. Guess we can’t change them all, LOL!

A medical puzzle yields cancer clue
Downs gene starves growth of tumors
By Stephen Smith, Globe Staff | June 1, 2009

It is a scientific riddle that has stumped, and deeply intrigued, specialists in cancer and genetics for decades: Why do people with Down syndrome so rarely develop life-threatening tumors?

The famed Boston scientist Judah Folkman puzzled over the question for decades, since encountering it on an exam as a young medical student.

Now, 17 months after he died, researchers in his lab at Children’s Hospital Boston have found an answer, and their discovery could provide a beacon to scientists developing treatments and preventive medications designed to be broadly effective against cancer, wherever it resides in the body.

The scientists discovered that the extra chromosome carried by people with Down syndrome - which causes the condition’s distinctive features - harbors a gene responsible for starving tumors of the blood they need to survive and flourish.

That had been Folkman’s suspicion all along.

“Most people don’t appreciate the fact that these individuals with Downs potentially hold a secret that might lead to quite substantial and revolutionary new treatments for cancer,” said Dr. David Sweetser, who treats patients and researches cancer at MassGeneral Hospital for Children but was not involved in the Downs project. “The obvious hope is that this is going to give us information to help develop a tool that we could use to treat a whole variety of solid tumors.”

In many respects, the discovery, detailed last month in the journal Nature, is a textbook example of scientific serendipity.

As a junior researcher, Sandra Ryeom wanted to better understand a protein called calcineurin - and, more specifically, what controls its activity in humans. It was a subject of intense interest because the protein plays a sometimes lethal role in causing transplanted organs to be rejected by recipients.

Six years ago, Ryeom and other scientists identified the genetic mechanism that acts like an on-and-off switch for calcineurin.

“At that point,” Ryeom said, “it was not looked at in terms of cancer, blood vessel growth, or Down syndrome.”

That changed soon enough when Ryeom recognized where that gene lives in the human body: on chromosome 21. That is the same chromosome that exists in triplicate in people with Down syndrome. Most people inherit chromosomes in pairs. But it is the third chromosome 21 that produces the external physical features and internal medical problems associated with Down syndrome, including heart defects, respiratory problems, and Alzheimer’s disease.

At the same time, experiments were showing that the gene had a significant effect in stanching the growth of blood vessels that nourish tumors.

It was like watching the pieces of a puzzle assemble: Could this gene, found on the same chromosome that defines Down syndrome, be especially bountiful in people with Down and, thus, responsible for depriving tumors of what they need to grow?

Epidemiologic studies of thousands of people with Down syndrome - there are more than 400,000 in the United States - have shown they are less than 10 percent as likely to die from solid tumors as their comparably aged peers, and that has remained true even as scientific advances allow people with the syndrome to live deeper into adulthood. Curiously, though, Down syndrome appears to increase prospects of being diagnosed with leukemia, a blood-borne cancer.

“The way that cancer affects people with Down syndrome is just so intriguing from both perspectives,” said Dr. Jeffrey Toretsky, a pediatric oncologist at Georgetown University’s Lombardi Comprehensive Cancer Center. “Why do they get more leukemias but fewer solid tumors?” (more…)

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