All Things Considered

Americans Win Nobel For Research On Aging

By Jon Hamilton

Published October 5, 2009 5:55 AM

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Three American scientists who made key discoveries about how living cells age have received the 2009 Nobel Prize in Physiology or Medicine.

The winners are Elizabeth Blackburn of the University of California, San Francisco; Carol Greider of Johns Hopkins University in Baltimore; and Jack Szostak of Massachusetts General Hospital in Boston.

The scientists all study telomeres — structures that act like caps on the ends of chromosomes and protect them when cells divide. Chromosomes are the long strands of DNA that contain a living creature's genetic code.

Their work, together and apart, figured out how telomeres delay the aging of cells, that they are caused by the enzyme telomerase, and that they exist in all species, including humans.

These discoveries are now being used to study how behavior, such as diet or smoking, can determine the levels of telomerase in an individual and therefore influence the aging of his cells. The subject is also being looked at in terms of cancer therapy, as restricting telomeres can hinder the cell division that occurs so rapidly in cancerous tumors.

Each winner will receive one-third of the prize of about $1.4 million.

Elizabeth Blackburn

Blackburn discovered the molecular nature of telomeres, and her research lab now focuses on many different aspects of how telomeres work, including the relationship between accelerated telomere shortening and stress.

Blackburn is the first Australian woman to win Nobel Prize and only the ninth woman to win the prize for physiology or medicine in the past century.

She has outlined a mind/body connection to disease through an enzyme that plays a key role in how cells function and age. Blackburn is studying how diet, exercise and decreasing stress may reduce the risk of disease and even reverse damage due to coronary artery disease.

In a 2006 study, her group found that low levels of telomerase, the enzyme that helps keeps telomeres intact, were associated with smoking, high blood pressure, high blood sugar and pre-diabetes. Her lab is now looking at whether interventions such as a very low-calorie diet or stopping smoking may help repair the damage caused by stress.

In 2004, Blackburn was the focus of controversy over her support of "therapeutic cloning," which uses embryos to develop new treatments from stem cells. Then-President George W. Bush declined to reappoint Blackburn to his bioethics council, a political move in the eyes of many scientists and ethicists.

Blackburn, who grew up in Tasmania, was named one of Time magazine's "100 Most Influential People in the World" in 2007.

From her earliest years she was fascinated by small creatures, and that fascination led to her interest in molecular biology. She joined the UCSF faculty in 1990 and lives in San Francisco.

Carol Greider

Greider co-discovered telomerase in 1984 while working as a graduate student with Blackburn at the University of California, Berkeley.

"What intrigues basic scientists like me is that anytime we do a series of experiments, there are going to be three or four new questions that come up when you think you've answered one. Our approach shows that while you can do research that tries to answer specific questions about a disease, you can also just follow your nose," she said after receiving an award for her work in 2006.

Greider's father was a physicist at the University of California, Davis, and she credits him with influencing her to pursue a career in academic science.

While working at McMaster University in 1990, Greider realized that telomere length is related to cellular aging and found that telomerase is activated in cancer cells. That allows the cells to continue to grow and divide. Her work with mice and human cells has confirmed that inhibiting telomerase can limit cancer cells and tumor production.

Jack Szostak

Szostak is genetics professor at Harvard Medical School and Massachusetts General Hospital.

He was born in England but grew up in Canada. Szostak was fascinated with learning more about how cells work, which led to discoveries that telomeres in human cells play crucial roles in both cancer and aging.

Szostak's early work with genetics led to key discoveries about telomeres. His interest in telomeres was piqued when he heard of Blackburn's work in 1980. The two then performed an experiment that proved that telomere DNA is present in most plants and animals as a fundamental mechanism.

Szostak is also credited with creating the first yeast artificial chromosome, which led scientists to map the location of genes in mammals and develop techniques for manipulating genes, according to the Howard Hughes Medical Institute, where he also holds the title of HHMI investigator.

In recent years, Szostak's research has focused on understanding how complex chemicals come together to form simple organisms that can reproduce and evolve. According to Massachusetts General Hospital, the Szostak lab is using the principle of molecular evolution as a tool for drug discovery to treat different types of cancer.

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MELISSA BLOCK, host:

You're listening to ALL THINGS CONSIDERED from NPR News.

Now, time to hear from three scientists who discovered this morning they had won the Nobel Prize in Physiology or Medicine.

As NPR's Jon Hamilton reports, they won for explaining a biological process that seems to play an important role in cancer and aging.

JON HAMILTON: When cells divide, they lose a tiny bit of genetic information at the end of each chromosome.

Dr. ELIZABETH BLACKBURN (University of California, San Francisco): The ends of chromosomes are always wearing down.

HAMILTON: Elizabeth Blackburn from the University of California, San Francisco, is one of the scientists who became a Nobel winner today. Blackburn says the ends of chromosomes would eventually get worn away if they weren't protected by something called a telomere. She says it acts like the plastic tip on a shoelace, which prevents the lace ends from fraying.

But where do telomeres come from? That's what Blackburn was trying to figure out in the 1980s when she was at UC Berkeley. She figured there must be an enzyme responsible for making and maintaining these genetic shoelace tips.

Dr. BLACKBURN: There were some hints. And then I think there was a particular time when we really saw a particular piece of evidence there, which said very strongly to us, ah, this thing really does exist.

HAMILTON: The discovery was made by Carol Greider, who was a graduate student back then. These days, Greider is a professor at Johns Hopkins University in Baltimore. She also will receive a share of the Nobel Prize.

Dr. CAROL GREIDER (Johns Hopkins University) We were studying these single-celled pond animals called Tetrahymena, that happen to have 40,000 chromosomes. And we figured if you want to understand how chromosomes are replicated and how telomeres work, go to the organism that has 40,000 of them.

HAMILTON: What Greider found in those organisms was an enzyme that was able to keep the ends of chromosomes in good shape. She says at first they called the enzyme telomere terminal transferase.

Dr. GREIDER: But we realized, especially because we were working with this organism that was called Tetrahymena thermophila, that if you want to say Tetrahymena thermophila telomere terminal transferase, that gets to be a mouthful.

HAMILTON: So Greider took a friend's suggestion and renamed the enzyme telomerase. At the time, it wasn't clear whether the system worked the same way in other species. That question was answered by Jack Szostak, a geneticist at Harvard Medical School and Massachusetts General Hospital. He's the third recipient of today's Nobel Prize.

Szostak took the telomere DNA from the organism Blackburn and Greider were studying and inserted it into yeast cells. He then used X-ray images to see whether the DNA was protecting yeast chromosomes during cell division.

Dr. JACK SZOSTAK (Geneticist, Harvard Medical School, Massachusetts General Hospital): There was a moment where, you know, in sort of developing the X-ray film where, you know, just by looking at it, it was obvious that the experiment had worked and that, therefore, the telomere machinery was working in yeast.

HAMILTON: That suggested the machinery would be present in all species, including humans. More recent research has confirmed that. Szostak says that when he and other scientists made those early discoveries, they were just trying to understand how cells work. But since then, it's become clear that the process they uncovered offers a new way to understand a wide range of diseases, including cancer. Szostak says cancer cells depend on telomerase. He says it seems to allow them to divide like crazy without dying the way normal cells would.

Dr. SZOSTAK: The hope is that by interfering with the enzyme, maybe there will be a therapeutically useful benefit.

HAMILTON: Elizabeth Blackburn from UC San Francisco says telomeres also seem to have a role in things like heart disease, diabetes and perhaps even the aging process itself. Blackburn's recent work suggests that chronic psychological stress can actually damage telomeres.

Jon Hamilton, NPR News. Transcript provided by NPR, Copyright National Public Radio.

Source: NPR