Tiny circles of DNA harbor cancer-associated oncogenes and immunomodulatory genes promoting cancer development. They arise during the transformation from pre-cancer to cancer, say Stanford Medicine-led team.
Tiny circles of DNA that defy the accepted laws of genetics are key drivers of cancer formation, according to an international study led by researchers at Stanford Medicine.
The circles, known as extrachromosomal DNA or ecDNA, often harbor cancer-associated genes called oncogenes. Because they can exist in large numbers in a cell, they deliver a super-charged growth signal that can override a cell’s natural programming. They also contain genes likely to dampen the immune system’s response to a nascent cancer, the researchers found.
“This study has profound implications for our understanding of ecDNA in tumor development,” said professor of pathology Paul Mischel, MD. “It shows the power and diversity of ecDNA as a fundamental process in cancer. It has implications for early diagnosis of precancers that put patients at risk, and it highlights the potential for earlier intervention as treatments are developed.”
Mischel is one of six senior authors of the research, which was published recently in the journal Nature. Howard Chang, MD, PhD, professor of genetics and the Virginia and D.K. Ludwig Professor in Cancer Research, is also a senior author. Other senior authors include senior staff scientist Thomas Paulson, PhD, from Seattle’s Fred Hutchison Cancer Center; assistant professor of pediatrics Sihan Wu, PhD, assistant professor at Children’s Medical Center Research Institute at the University of Texas Southwestern Medical Center; professor of computer science and engineering Vineet Bafna, PhD, from UC San Diego; and professor of cancer prevention and director of the Early Cancer Institute Rebecca Fitzgerald, MD, from the University of Cambridge.
“People with ecDNA in their precancerous cells are 20 to 30 times more likely than others to develop cancer,” Chang said. “This is a huge increase, and it means we really need to pay attention to this. Because we also found that some ecDNAs carry genes that affect the immune system, it suggests that they may also promote early immune escape.”
A grand challenge
Deciphering ecDNA’s role in cancer was one of four Cancer Grand Challenges awarded by the National Cancer Institute and Cancer Research UK in 2022. The grand challenges program was launched to bring together researchers from around the world to tackle complex research topics too daunting for any one group. Mischel was awarded $25 million to lead a team of international researchers to learn more about the circles. But first they had to jettison some key genetic principles that have guided the field for nearly 200 years.
“When we think about how a tumor evolves in a patient and in response to treatment, we think of the branching trees of life proposed by Charles Darwin,” Mischel said. “This idea is so powerful that researchers often sequence the DNA from multiple parts of a tumor and draw these trees to learn about its evolution. If a mutation is there at the trunk of the tree and in all of its branches, we assume it is a key driver event in the formation of the tumor; if it is in only some branches, we assume it happened later in tumor development and may not be a good target for drug development.”
But these assumptions hinge on the idea that all of a tumor’s DNA is neatly contained on chromosomes, which are evenly divided among daughter cells each time a cancer cell divides — ensuring that each new cell gets one, and only one, copy of each chromosome.
In contrast, the tiny ecDNA circles swirl in a dividing cell like bubbles circling a bathtub drain and are portioned willy-nilly between the new daughter cells. One may get nearly all the circles; the other, almost none. As the generations accumulate, the evolutionary tree favored by Darwin begins to look decidedly odd, with the appearance of ecDNA-bearing cells sprinkled among the branches like haphazardly hung Christmas lights.
“Some researchers have looked at the evolutionary trees and decided that, because you see it here, but not there, it must be that ecDNA formation is a late event and probably isn’t important when considering treatments,” Mischel said. “Our team thought that interpretation was wrong.”
Pinpointing a reason
To get to the bottom of the tiny circles, Mischel, Chang and their collaborators turned to a specific example of cancer development — people with a condition known as Barrett’s esophagus, which occurs when the cells lining the lower part of the esophagus are damaged by acid reflux and become more like cells lining the intestine than healthy esophageal tissue. About 1% of these people develop esophageal cancer, which is difficult to treat and has a high mortality rate. Because the outcome is so poor, people with Barrett’s esophagus are routinely monitored with endoscopies and biopsies of the abnormal tissue. Because of these frequent biopsies, the researchers had access to tissue samples collected both before and after cancers developed.
The researchers assessed the prevalence of ecDNA, and identified the genes they carried, in biopsies from nearly 300 people with Barrett’s esophagus or esophageal cancer treated at the University of Cambridge or at Seattle’s Fred Hutchison Cancer Center, where individual patients were studied as the cancer developed. They found that the prevalence of ecDNA increased from 24% to 43% in early- versus late-stage esophageal cancer, indicating the continual formation of the DNA circles during cancer progression. More tellingly, they found that 33% of people with Barrett’s esophagus who developed esophageal cancer had ecDNA in their precancerous cells. In contrast, only one out of 40 people who didn’t develop cancer had cells with ecDNA, and that individual passed away due to another cause.
“The conclusions were remarkable,” Mischel said. “We see that ecDNA can arise in these precancerous cells, and that if it is there, the patient is going to get cancer. We also saw the continuous formation of ecDNA as the cancer progresses, indicating that it is advantageous to cancer growth. Finally, we saw that the ecDNA can contain immune-modulatory genes in addition to oncogenes.”
“If a gene is carried on ecDNA, it is very likely to be important for cancer,” Chang said. “These circles are not only giving us new targets for cancer diagnosis and drug development; they are also teaching us what is important for tumor growth.”
What to look at next
The researchers are planning to explore more about how ecDNAs arise in cancer cells and how they work together to make proteins that drive cancer cell growth. They saw that cancers with ecDNA were likely to also have mutations in a protein called p53. Sometimes called “the guardian of the genome,” p53 temporarily halts the cell cycle to allow cells to repair damage or mutations to their DNA before beginning to divide.
“We want to learn more about the landscape of ecDNA in precancers and the risks it confers,” Mischel said. “We also want to know if we can stop its formation or activity; how to improve our ability to detect their presence; how they affect the immune system; and whether there are opportunities for new, novel therapies. There is much more to learn, and our team is excited to tackle all these issues. But what we do know for certain is that these tiny DNA circles are a very big deal in cancer.”
![](https://www.nanoappsmedical.com/wp-content/uploads/2017/05/spacer.jpg)
News
The Silent Battle Within: How Your Organs Choose Between Mom and Dad’s Genes
Research reveals that selective expression of maternal or paternal X chromosomes varies by organ, driven by cellular competition. A new study published today (July 26) in Nature Genetics by the Lymphoid Development Group at the MRC [...]
Study identifies genes increasing risk of severe COVID-19
Whether or not a person becomes seriously ill with COVID-19 depends, among other things, on genetic factors. With this in mind, researchers from the University Hospital Bonn (UKB) and the University of Bonn, in [...]
Small regions of the brain can take micro-naps while the rest of the brain is awake and vice versa
Sleep and wake: They're totally distinct states of being that define the boundaries of our daily lives. For years, scientists have measured the difference between these instinctual brain processes by observing brain waves, with [...]
Redefining Consciousness: Small Regions of the Brain Can Take Micro-Naps While the Rest of the Brain Is Awake
The study broadly reveals how fast brain waves, previously overlooked, establish fundamental patterns of sleep and wakefulness. Scientists have developed a new method to analyze sleep and wake states by detecting ultra-fast neuronal activity [...]
AI Reveals Health Secrets Through Facial Temperature Mapping
Researchers have found that different facial temperatures correlate with chronic illnesses like diabetes and high blood pressure, and these can be detected using AI with thermal cameras. They highlight the potential of this technology [...]
Breakthrough in aging research: Blocking IL-11 extends lifespan and improves health in mice
In a recent study published in the journal Nature, a team of researchers used murine models and various pharmacological and genetic approaches to examine whether pro-inflammatory signaling involving interleukin (IL)-11, which activates signaling molecules such [...]
Promise for a universal influenza vaccine: Scientists validate theory using 1918 flu virus
New research led by Oregon Health & Science University reveals a promising approach to developing a universal influenza vaccine—a so-called "one and done" vaccine that confers lifetime immunity against an evolving virus. The study, [...]
New Projects Aim To Pioneer the Future of Neuroscience
One study will investigate the alterations in brain activity at the cellular level caused by psilocybin, the psychoactive substance found in “magic mushrooms.” How do neurons respond to the effects of magic mushrooms? What [...]
Decoding the Decline: Scientific Insights Into Long COVID’s Retreat
Research indicates a significant reduction in long COVID risk, largely due to vaccination and the virus’s evolution. The study analyzes data from over 441,000 veterans, showing lower rates of long COVID among vaccinated individuals compared [...]
Silicon Transformed: A Breakthrough in Laser Nanofabrication
A new method enables precise nanofabrication inside silicon using spatial light modulation and laser pulses, creating advanced nanostructures for potential use in electronics and photonics. Silicon, the cornerstone of modern electronics, photovoltaics, and photonics, [...]
Caught in the actinium: New research could help design better cancer treatments
The element actinium was first discovered at the turn of the 20th century, but even now, nearly 125 years later, researchers still don't have a good grasp on the metal's chemistry. That's because actinium [...]
Innovative Light-Controlled Drugs Could Revolutionize Neuropathic Pain Treatment
A team of researchers from the Institute for Bioengineering of Catalonia (IBEC) has developed light-activated derivatives of the anti-epileptic drug carbamazepine to treat neuropathic pain. Light can be harnessed to target drugs to specific [...]
Green Gold: Turning E-Waste Into a Treasure Trove of Rare Earth Metals
Scientists are developing a process inspired by nature that efficiently recovers europium from old fluorescent lamps. The approach could lead to the long-awaited recycling of rare earth metals. A small molecule that naturally serves [...]
Cambridge Study: AI Chatbots Have an “Empathy Gap,” and It Could Be Dangerous
A new study suggests a framework for “Child Safe AI” in response to recent incidents showing that many children perceive chatbots as quasi-human and reliable. A study has indicated that AI chatbots often exhibit [...]
Nanoparticle-based delivery system could offer treatment for diabetics with rare insulin allergy
Up to 3% of people with diabetes have an allergic reaction to insulin. A team at Forschungszentrum Jülich has now studied a method that could be used to deliver the active substance into the [...]
Nanorobot kills cancer cells in mice with hidden weapon
Researchers at Karolinska Institutet in Sweden have developed nanorobots that kill cancer cells in mice. The robot's weapon is hidden in a nanostructure and is exposed only in the tumor microenvironment, sparing healthy cells. [...]