- James Gallagher
- BBC Science Correspondent
This discovery helps with the help of the immune system, targeting and attacking the tumor.
Scientists have concluded that remnants of ancient viruses that spent millions of years hiding inside human DNA help the body fight cancer.
A study by the Francis Crick Institute showed that dormant remnants of these ancient viruses are awakened when cancer cells get out of control.
This inadvertently helps the immune system target and attack the tumor.
The team seeks to harness this discovery to design vaccines that might enhance or even prevent cancer treatment.
The researchers noted a link between better recovery from lung cancer and a part of the immune system called B cells that gather around tumors.
B cells, which are part of the immune system, produce masses of antibodies that can help attack any foreign or harmful organism. .
B cells are the part of the body that makes antibodies and are best known for their role in fighting infections, such as the coronavirus.
What these cells were doing in lung cancer was a mystery, but a recent series of complex experiments using patient samples and animal tests showed they were still trying to fight viruses.
“It turns out that the antibodies recognize remnants of so-called endogenous retroviruses,” Professor Julian Downward, associate director of research at the Francis Crick Institute, told us.
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B cells, which are part of the immune system, produce clumps of antibodies that can help attack invaders
Retroviruses have a neat trick of inserting a copy of their genetic instructions into our body’s makeup. Therefore:
- More than 8% of what we think of as “human” DNA actually has such viral origins.
- Some of these retroviruses have been a staple of our genetic code for tens of millions of years and are shared with our ancient relatives, the apes.
- Other retroviruses may have entered our DNA thousands of years earlier.
It may be that some of these properties and how they work serve useful purposes within our cells, but experiments and studies are still ongoing to monitor and prevent the spread of others of these cells within the human body excessively.
However, chaos takes over inside a cancer cell when it grows uncontrollably and loses the tight control of these ancient viruses.
These ancient genetic instructions can no longer revive whole viruses but they can create enough virus fragments for the immune system to detect a viral threat.
“The immune system is tricked into thinking cancer cells are infected and tries to kill the virus, so it’s kind of an alarm system,” said Professor George Kasiotis, chair of viral immunology at the Biomedical Research Centre.
The antibodies call in other parts of the immune system that kill the “infected” cells as the immune system tries to stop the virus but in this case it takes out the cancer cells.
Prof Kassiotis says it’s a remarkable reversal of the role of retroviruses working at their peak. They “may have caused cancer in our ancestors” because of the way they invaded our DNA, but now they protect us from cancer which is wonderful, says the professor.
The study, published in the journal Nature, describes how this process occurs naturally in the body, but researchers want to enhance this effect by developing vaccines to teach the body how to search for endogenous retroviruses.
Professor Kassiotis added: “If we can do that, you can think of not only curative vaccines, you can also think of preventive vaccines.”
The research comes from a TracerX study that has been tracking lung cancers in unprecedented detail and this week showed the cancer’s “near infinite” ability to evolve. This prompted the researchers conducting the experiment to call for more focus on preventing cancer, which is very difficult to stop.
Dr Claire Bromley, from Cancer Research UK, said: “We all have ancient viral DNA in our genes, passed down from our ancestors, and this fascinating research has shed light on the role it plays in cancer and how our immune system can recognize and destroy cancer cells.” .
She said “more research” is needed to develop a cancer vaccine, but “nevertheless, this study adds to the growing body of research that might one day see this innovative approach to cancer treatment become a reality.”
