- James Gallagher
- BBC Science Correspondent
This discovery helps the immune system target and attack the tumor.
Remnants of ancient viruses hidden within human DNA for millions of years help the body fight cancer, scientists have concluded.
A study by the Francis Crick Institute showed that when cancer cells get out of control, dormant remnants of these ancient viruses wake up.
This inadvertently helps the immune system target and attack the tumor.
The team seeks to use this discovery to design vaccines that can improve or prevent cancer treatment.
Researchers have 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 antibodies that help attack any foreign or harmful organism. .
B cells are part of the body that make antibodies and are best known for their role in fighting infections like the coronavirus.
What these cells do in lung cancer has been a mystery, but a recent series of complex experiments using patient models and animal experiments has shown that they are still trying to fight viruses.
“The antibodies recognize residues from 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 clusters of antibodies that help attack invaders.
Retroviruses have a neat trick of inserting a copy of their genetic code into our body’s makeup. Therefore:
- More than 8% of what we think of as “human” DNA is actually of such viral origin.
- Some of these retroviruses have been a staple of our genetic code for tens of thousands of years and are shared with our ancient relatives, the apes.
- Other retroviruses may have entered our DNA thousands of years ago.
Some of these properties and how they work may serve useful purposes within our cells, but experiments and studies are still ongoing to monitor and prevent the proliferation of these cells within the human body.
However, chaos ensues when the cancer cell grows out of control and loses the tight control of these ancient viruses.
These ancient genetic mechanisms can no longer reproduce whole viruses, but they can produce enough viral 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 a kind of warning system,” said Professor George Cassiotis, head of viral immunology at the Center for Biomedical Research.
Antibodies call in other parts of the immune system that kill the “infected” cells when the immune system tries to stop the virus, but in this case it kills the cancer cells.
Professor Cassiotis says this is a significant shift from the peak role of retroviruses. They “could have caused cancer in our ancestors” by invading our DNA, but now they are protecting us from cancer, which is amazing, says the professor. .
A 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 that teach the body how to seek out endogenous retroviruses.
Professor Cassiotis added: “If we can do that, you can think not only about curative vaccines, you can also think about preventive vaccines.”
The research comes from the TracerX study, which is tracking lung cancers in an unprecedented way, and this week showed the cancer’s “near infinite” potential. This prompted the researchers conducting the experiment to focus more on preventing cancer, which is more 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 sheds light on the role it plays in cancer and how our immune system can recognize and destroy cancer cells.”
He said “much more research” is needed to develop a cancer vaccine, but “nevertheless, this study adds to the growing body of research that could one day make this innovative approach to cancer treatment a reality.”
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