JAN 02, 2020 12:02 PM PST

Mysterious Extrachromosomal DNA is Linked to Childhood Cancer

WRITTEN BY: Carmen Leitch

Cells carry the code for life in their DNA, which (in eukaryotic cells) is stored in the nucleus and carries the instructions for making virtually every protein in an organism. There are a few exceptions, however. An ancient organelle called the mitochondria carries a bit of its own DNA, and scientists have also known about the presence of extrachromosomal DNA (that's separate from genomic DNA) for decades. Very little is known about the role of extrachromosomal DNA (ecDNA). It may originate in different ways, and there may be thousands of ecDNA molecules in a cell that are important for different things. It may be linear or circular. Research has also found that there is more ecDNA in cancerous cells

A microscopic view of ganglioneuroblastoma, which is a growth on ganglia in the nervous system. Magnified X25. / Credit: National Cancer Institute / Dr. Maria Tsokos

Now, researchers have produced a map of extrachromosomal circular DNA (eccDNA), and have found that eccDNA may play a role in cancer development in children. This work may help explain why cancer sometimes arises in children, though cancer is often due to genetic errors that build up over a lifetime of exposure to DNA-damaging influences.

Reporting in Nature Genetics, an international team of researchers mapped circular DNA in neuroblastoma samples taken from 93 children affected by the deadly tumor. Every tissue sample they assessed carried an average of 5,000 copies of circular DNA, which was far more than they anticipated. 

Their work also showed that specific pieces of DNA can separate from a chromosome, and then reintegrate into a chromosome in a different place. 

"This can potentially cause cancer if it results in the original sequence of genetic information being disrupted," explained Dr. Anton Henssen, leader of the Emmy Noether Independent Junior Research Group and a Berlin Institute of Health Clinician Scientist. "The detailed processes involved had not previously been elucidated in this manner and provide insight into how even young cells, like those found in children, can transform into cancer cells."

"We were also able to show that certain types of circular DNA may accelerate neuroblastoma growth," noted Dr. Richard Koche of the Memorial Sloan Kettering Cancer Center. "Testing for their presence may therefore make it easier to predict the course of the disease. Additionally, studying this process in the relatively quiet genomes of these pediatric tumors may help illuminate similar mechanisms which were previously missed in more complex adult cancers. Given the recent interest in circular DNA in a variety of normal and disease contexts, the current study may have implications for a broad range of tumor types and associated clinical outcomes."

More work is planned to validate these findings. "We also want to conduct more detailed research into the origins of circular DNA in order to better understand why it is that children develop cancer," added Henssen.

Work reported last year by a different group has suggested that while extrachromosomal circular DNA is probably too small to code for proteins, but it may express small RNAs that have a regulatory function. Learn more about efforts to use extrachromosomal DNA to diagnose cancer from the video.

Sources: AAAS/Eurekalert! via Charité – Universitätsmedizin Berlin, Nature Genetics

About the Author
  • Experienced research scientist and technical expert with authorships on 28 peer-reviewed publications, traveler to over 60 countries, published photographer and internationally-exhibited painter, volunteer trained in disaster-response, CPR and DV counseling.
You May Also Like
JAN 03, 2020
Cardiology
JAN 03, 2020
Healthy Sleep May Offset Genetic Heart Disease Risk
People with a high genetic risk of heart disease or stroke may be able to offset that risk with healthy sleep patterns, according to new research. The rese...
FEB 09, 2020
Genetics & Genomics
FEB 09, 2020
Mosquitoes are Driven to Search for Heat in the Hunt for Meals
Mosquitoes can be dangerous disease vectors, and they infect and kill hundreds of thousands of people with illnesses like dengue, malaria, and West Nile Virus....
FEB 09, 2020
Microbiology
FEB 09, 2020
Investigating the Links Between Viruses and Cancer
The Pan-Cancer Analysis of Whole Genomes (PCAWG) has brought over 1,300 scientists together to gain new insights into the genetics of cancer....
FEB 17, 2020
Microbiology
FEB 17, 2020
Giant Viruses Blur the Line Between Life and Non-Life
Bacteriophages, also known as phages, are more complex than many viruses that we know of, and often carry large genomes....
MAR 16, 2020
Genetics & Genomics
MAR 16, 2020
How the Genetic Material in Sperm is Unpacked During Fertilization
The genetic material from a sperm and an egg merges to form a new human genome, and now we know more details about the process....
MAR 30, 2020
Genetics & Genomics
MAR 30, 2020
Scientists Discover an Antibiotic Resistance Gene
The gene enables bacteria to resist the effects of an aminoglycoside antibiotic called plazomycin....
Loading Comments...