- By James Gallagher
- Health and science correspondent
Remnants of ancient viruses – which spent millions of years hiding inside human DNA – help the body fight cancer, scientists say.
The Francis Crick Institute study showed that the dormant remnants of these old viruses are awakened when cancerous cells lose control.
This inadvertently helps the immune system target and attack the tumor.
The team wants to use the discovery to design vaccines that can boost cancer treatment, or even prevent it.
Researchers noticed a connection between better survival from lung cancer and a part of the immune system, called B-cells, that cluster around tumors.
B-cells are the part of our body that make antibodies and are best known for their role in fighting infections, such as Covid.
What exactly they do in lung cancer is a mystery but a series of complex experiments using samples from patients and animal tests showed that they still try to fight viruses.
“It turns out that the antibodies recognize the remnants of so-called endogenous retroviruses,” Prof Julian Downward, an associate research director at the Francis Crick Institute, told me.
Retroviruses have the amusing trick of placing a copy of their genetic instructions inside ourselves.
- Over 8% of what we think of as “human” DNA actually has such a viral origin
- Some of these retroviruses became part of our genetic code tens of millions of years ago and are shared with our evolutionary relatives, the great apes.
- Other retroviruses may have entered our DNA thousands of years ago
Some of these foreign instructions are, over time, integrated and serve a useful purpose within our cells, but others are tightly controlled to prevent their spread.
However, chaos reigns inside a cancerous cell when it grows uncontrollably and the once tight control over these ancient viruses is lost.
These ancient genetic instructions can no longer revive whole viruses but they can create fragments of viruses that are sufficient for the immune system to detect a viral threat.
“The immune system is tricked into believing that the tumor cells are infected and it’s trying to get rid of the virus, so it’s a kind of alarm system,” Prof George Kassiotis, head of retroviral immunology at the biomedical research center, told me.
Antibodies summon other parts of the immune system that kill “infected” cells – the immune system is trying to stop a virus but in this case releases cancerous cells.
Prof Kassiotis said it was a remarkable reversal of role for retroviruses which, in their abundance, “could have caused cancer in our ancestors” because of the way they invade our DNA, but now protect us from in cancer, “which I think is fascinating” , He added.
The studying, published in the journal Naturedescribes how this occurs naturally in the body but researchers want to improve that effect by developing vaccines to teach the body how to hunt down endogenous retroviruses.
“If we can do that, you can think not only of therapeutic vaccines, you can also think of preventive vaccines,” said Prof Kassiotis.
The research comes out of the TracerX study which tracks lung cancers in unprecedented detail and this week showed the cancer’s “near infinite” ability to grow. This led the researchers running the trial to call for more focus on preventing the cancer because it is so 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 amazing research highlights the role that its role in cancer and how our immune system recognizes and destroys cancer cells.”
He said that “more research” is needed to develop a cancer vaccine but “nevertheless, this study adds to the growing body of research that may one day see this innovative approach to cancer treatment become a truth.”