Scientists Are Just Beginning to Understand Mysterious DNA Circles Common in Cancer Cells
Posted by IHEART AWARENES
Scientists Are Just Beginning to Understand Mysterious DNA Circles Common in Cancer Cells
DNA circles avoid those hooks. How many circles end up in each of the two new cells seems to be random. The cells may split the DNA circles evenly, or one may end up with more than the other. In some cases, one cell hits the jackpot and inherits them all.
Dr. Mischel and other researchers have found evidence that a large inheritance of circles can speed up a cell’s growth. As this lottery plays out with each new cell division, it may allow cancers to rapidly become aggressive.
DNA circles can also slip back into chromosomes, according to a new study led by Anton G. Henssen, a pediatric oncologist at Charité University Hospital Berlin and the Max Delbrück Center of Molecular Medicine. Dr. Henssen thinks that the circles may endow nearby genes with their overdrive, which may lead cells to become more dangerous.
“It’s a very powerful vehicle for cancer evolution,” said Dr. Henssen, a co-organizer of the upcoming meeting in Berlin.
Dr. Chang, Dr. Mischel and their colleagues have started a company called Boundless Bio to look into potential treatments based on their research.
“If you can clear these circles, it’s a way to attack cancer,” said Dr. Anindya Dutta, a molecular biologist at the University of Virginia School of Medicine, who is not involved in the company.
DNA circles aren’t found only in cancer cells. Healthy cells have them, too, studies have shown. In one of these studies, published last year, Dr. Regenberg and her colleagues obtained samples of blood and muscle from 16 people. They extracted DNA from the material and used chemicals to dissolve away the DNA on the chromosomes. When the team analyzed the DNA that remained, they found the signature of about 100,000 different kinds of circles.
There seem to be stark differences between the DNA circles in healthy and diseased cells. In cancer cells, the circles may contain a million base pairs of DNA or more, Dr. Chang and his colleagues found. In contrast, the DNA circles in healthy cells are typically much smaller, containing under 25,000 base pairs, and usually just a few hundred. (The entire human genome contains about three billion base pairs.)
It may be that bigger loops of DNA pose a greater threat of cancer, because they are large enough to house genes that could help a cell grow faster. A small circle may not be long enough to really matter. “They don’t have the real estate to contain a whole gene,” Dr. Dutta said.
But Dr. Dutta thinks that some small circles may still have an impact. He and his colleagues have shown that circles that are too small to encode a protein can still encode small, potent molecules called microRNAs. Those molecules can act like switches, turning off other genes.
As tantalizing as such findings are, they don’t reveal whether small circles of DNA have an influence on our health. For instance, many different kinds of small DNA circles have been found in healthy cells, but researchers don’t know how common they are. Maybe they are too rare to make a difference.
But Dr. Regenberg says we shouldn’t write them off. She expects that the effect of DNA circles may extend far beyond cancer, which has drawn most of the scientific attention thus far.
“It’s been very cancer-centered,” she said. “It’s like when a horse has blinders: The blinders focus the science, but they also prevent some things from being understood.”
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