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The story, as typically occurs in science, sounded so interesting. Cells have a molecular clock that determines how lengthy they stay. If you happen to can simply cease the clock, cells can stay indefinitely. And the identical ought to go for folks, who’re, in any case, constructed from cells. Cease the cell clocks and you may stay youthful.
The clocks come within the type of caps on the tip of chromosomes — the lengthy twisted strings of DNA carrying the cells’ genes. The caps on chromosomes, referred to as telomeres, are chains of quick, repeated segments of DNA. Each time a cell divides, its telomeres get a bit of shorter, till lastly they get so quick that the cell dies.
“Brief telomeres had been considered dangerous — folks with untimely getting old syndromes had quick telomeres — so, by analogy, lengthy telomeres had been considered good,” mentioned Dr. Mary Armanios, professor of oncology at Johns Hopkins College Faculty of Drugs and director of the Telomere Middle on the medical college’s Sidney Kimmel Complete Most cancers Middle. “And the longer the higher.”
However, in fact, nothing in biology is so easy. And a paper printed Thursday within the New England Journal of Drugs, with outcomes of a examine that Dr. Armanios led, exhibits that the telomere story isn’t any exception. Whereas quick telomeres do result in well being issues, lengthy telomeres result in well being issues of their very own. Removed from extending life, lengthy telomeres seem to trigger most cancers and a blood dysfunction referred to as CHIP, a situation that will increase the danger of blood cancers and coronary heart illness.
Dr. Elizabeth Blackburn, an emerita professor on the College of California, San Francisco, who shared a Nobel Prize for the invention of an enzyme concerned in making telomeres and who was not concerned within the examine, mentioned it was a “lovely paper” that went past correlations to indicate a direct hyperlink between lengthy telomeres and illness. She added that the analysis “enlightens this entire trade-off.”
For Dr. Armanios, it’s the fruits of labor she started 20 years in the past.
When scientists began learning telomeres, they noticed that younger folks had longer ones than older folks. When cells are grown within the lab, their telomeres act as kind of a ticking clock, figuring out how lengthy they should stay.
Quickly, telomeres had been hailed as a secret to getting old — corporations marketed that they might inform your organic age by measuring the size of your telomeres. Others mentioned that you would prolong your life by preserving your telomeres with dietary supplements.
However Dr. Armanios and different researchers had noticed that telomere lengths appeared constrained to a slender vary, indicating there’s a worth to pay for very lengthy or very quick telomeres.
Inhabitants studies by a number of teams appeared to assist that concept. They discovered correlations — not a trigger and impact — with elevated illness dangers at both finish of the conventional telomere spectrum.
These with shorter than common telomeres appeared to have an increased risk of immune system issues and quite a lot of degenerative illnesses, in addition to pulmonary fibrosis, a lung illness. These with longer than common telomeres appeared to have a modestly elevated threat of most cancers.
There have been, although, some puzzlements.
“Some organisms have loopy lengthy telomeres, like mice,” mentioned Dr. Benjamin Ebert, chairman of medical oncology on the Dana-Farber Most cancers Institute. “And mice don’t stay that lengthy.”
Dr. Armanios, as a human geneticist, thought the best way to get solutions was to review people. “There are belongings you simply can’t infer from learning cells,” she mentioned.
She suspected, she mentioned, that “you simply can’t elongate telomeres with out a worth,” and commenced on the lookout for folks with very lengthy telomeres to ask what that worth is perhaps.
She determined to search for folks with a standard genetic mutation, POT1, that may end up in lengthy telomeres. It was recognized to extend most cancers threat however most researchers thought it was for causes apart from lengthening telomeres.
She ended up with 17 folks from 5 households. They ranged in age from 7 to 83 and had terribly lengthy telomeres.
Additionally they had tumors, starting from benign, like goiters and uterine fibroids, to malignant, like these from melanoma and blood cancers. Throughout the two-year examine, 4 sufferers died of quite a lot of cancers.
Harriet Brown, 73, of Frederick, Md., is likely one of the examine individuals with very lengthy telomeres. She has had benign tumors referred to as paragangliomas in her neck and throat, thyroid most cancers and two melanomas. She additionally has CHIP, the blood dysfunction related to coronary heart illness and blood cancers.
She has frequent scans and exams however, she mentioned, “there may be actually not a lot I can do at this level,” as a result of there is no such thing as a option to stop extra tumors from creating.
The consequences of lengthy telomeres on folks like Ms. Brown make good sense, mentioned Dr. Norman Sharpless, professor of most cancers coverage and innovation on the College of North Carolina Faculty of Drugs and a former director of the Nationwide Most cancers Institute.
“It’s not that lengthy telomeres make cells develop,” he mentioned. “It’s that they don’t have the brakes to make them cease rising.” And since the telomeres of individuals with POT1 mutations don’t develop shorter with every cell division, the cells hold round, dividing repeatedly. The longer they’re dividing within the physique, the extra time they should accumulate random mutations, a few of which immediate tumor development.
That’s very true in blood, the place cells are consistently being produced. POT1 mutations in a few of these blood cells may give them time to build up different mutations that give them a selective benefit in development. Quickly a few of these mutated blood cells just about take over an individual’s bone marrow. The result’s CHIP.
That may be a new view of CHIP. The thought had been that as a result of folks with CHIP had been at elevated threat for blood most cancers, that CHIP itself was inflicting most cancers.
As an alternative, Dr. Armanios mentioned, it’s that lengthy telomeres are each creating CHIP and, independently, giving cells time to develop cancer-causing mutations.
“Getting old biology is much more sophisticated than we’d hoped,” Dr. Sharpless mentioned.
Or, as Dr. Blackburn noticed: Lengthy telomeres should not the key to everlasting youth.
“There is no such thing as a free lunch,” she mentioned.
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