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A rare genetic mutation makes people very short, but also resistant to cancer and diabetes.
Trading height for disease resistance. I’m Bob Hirshon and this is Science Update.
A rare genetic mutation that makes people very short also protects them from cancer and diabetes. This according to University of Southern California gerontologist Valter Longo. He and his colleagues studied a group of Ecuadorians with this mutation, which makes them deficient in a growth factor called IGF-1. That limits their stature, but has side effects that protect cells from damage. And when their cells do get damaged, they self-destruct more quickly than usual.
If you have very low levels, as these individuals do, then as soon as you’re pushed in this damage direction, then the cell dies.
That short-circuits the growth of tumors. Previous studies in yeast and mice support the findings. Longo says it probably wouldn’t be good to lower IGF-1 to these levels in other people, but it’s possible that a mild reduction could have more benefits than drawbacks. I’m Bob Hirshon for AAAS, the Science Society.
Making Sense of the Research
Cancer and diabetes are among the most common serious diseases in the developed world. So it's especially intriguing to find a group of people who seem to be almost completely unsusceptible. And that this group of people happens to have a rare genetic condition, called Laron syndrome, that keeps them from growing more than 4 feet tall.
There weren't many people in the study group—99, to be exact—but the researchers followed them closely for 22 years. During that time period, none of them developed diabetes, and only one developed cancer. That person's cancer was successfully treated, and she was cancer-free by the end of the study period. (Still, their overall life expectancy was about the same as in the general population, because they were more prone to accidents, convulsive disorders, and alcohol-related deaths.)
By comparison, the researchers looked at the normal-height close relatives of the Laron syndrome study group. During the same period, about 20 percent of those relatives died of cancer, and their rates of diabetes were typical for the Ecuadorian population as a whole. The researchers also reviewed the death records of 53 other people who had been extremely short, but not part of the formal study group. None of those 53 died from cancer or diabetes-related problems.
As you heard, the same genetic mutation that causes the extreme shortness appears to also stave off cancer and diabetes. The mutation prevents some growth hormones from functioning, and reduces the production of others. As a result, people with Laron syndrome don't get much taller than the average 7-year-old.
But the advantage of this growth deficiency is that it also limits the growth of bad cells. Cellular death is an important function in life; without it, we'd be riddled with tumors and disease. In fact, what makes a tumor a tumor is its inability to stop growing, even when it's crowding and damaging other tissue. Our cells are pre-programmed with a tendency to self-destruct if they reach a certain damage point, but sometimes that self-destruction program doesn't kick in. The Laron syndrome people's cells, however, shut down at the slightest sign of damage.
This raises questions about the treatment of cancer—for instance, is it possible that slightly lowering the levels of this growth hormone could be useful, at least in people who are being treated for cancer or are at high risk? It also calls into question whether giving people growth hormone to increase their height, as is sometimes done, is a good idea after all. These may be topics for future research.
Now try and answer these questions:
- What's unusual about the Ecuadorian population with Laron Syndrome?
- What are the ways in which the researchers concluded that the Laron population was resistant to cancer and diabetes?
- How does the genetic mutation cause both short stature and disease resistance?
- What future studies might build on these findings?
You may want to check out the March 9, 2012, Science Update Podcast to hear further information about this Science Update and the other programs for that week. This podcast's topics include: A rare mutation that protects people from diabetes and cancer, how the pancreas “tastes” sugar, and a new implantable microchip that delivers an osteoporosis drug. Also: chimpanzees may yawn for the same reason humans do.
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The Science Update Southpaw Minority delves into the possible benefits of genes for left-handedness.
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In the Science NetLinks lesson Cancer Risks, students learn about environmental and hereditary factors that increase the chance of developing cancer.
The Science Update lesson Testosterone Tradeoff focuses on the pros and cons of extra testosterone in a bird species.
The Science Update lesson Southpaw Minority delves into the possible benefits of genes for left-handedness.