Remnants of ancient viruses – which spent millions of years hiding in human DNA – help the body fight cancer, scientists say, reports BBC.
Cancer cellsPhoto: Jezper | Dreamstime.com
The study by the Francis Crick Institute showed that the dormant remnants of these old viruses are awakened when cancer cells get out of control.
This inadvertently helps the immune system target and attack the tumor.
The team wants to use the discovery to make vaccines that can stimulate the treatment of cancer or even prevent it.
Researchers have seen a link between a better survival rate for people with lung cancer and a part of the immune system – B cells – that gather around tumors.
B cells make antibodies and are better known for their role in fighting infections such as Covid.
What exactly these cells do in lung cancer was a mystery, but a series of complicated experiments using patient samples and animal tests showed that they are still trying to fight viruses.
How endogenous retroviruses, also present in monkey DNA, help destroy cancer
“The antibodies have been shown to recognize remnants of what are called endogenous retroviruses,” said Professor Julian Downward, Associate Director of Research at the Francis Crick Institute.
Retroviruses can, by an ingenious trick, slip a copy of their genetic instructions inside us.
More than 8% of what we think of as “human” DNA actually has such viral origins.
Some of these retroviruses became a fixed element of our genetic code tens of millions of years ago and are a common element with our evolutionary relatives, the great apes.
And other retroviruses may have entered our DNA several thousand years ago.
Some of these foreign instructions have been co-opted over time and serve useful purposes inside our cells, but others are tightly controlled to prevent their spread.
However, chaos reigns inside a cancer cell when it grows out of control and control of these ancient viruses is lost.
These ancient genetic instructions are no longer capable of resurrecting whole viruses, but they can create virus fragments that are sufficient for the immune system to detect a viral threat.
“The immune system is tricked into thinking the tumor cells are infected and trying to get rid of the virus, so it’s a kind of alarm system,” said Professor George Kassiotis, head of retroviral immunology at the biomedical research centre.
Antibodies call on other parts of the immune system to kill “infected” cells – the immune system is trying to stop a virus, but in this case it’s killing cancer cells.
Professor Kassiotis says it’s a remarkable reversal of role for retroviruses which, in their heyday, “may have caused cancer in our ancestors” because of the way they invade our DNA, but now protect us from cancer.
The study, published in the journal Nature, describes how this happens naturally in the body, but researchers want to enhance this effect by developing vaccines that teach the body how to hunt down endogenous retroviruses.
