Viruses that can help fight and prevent cancer – 04/16/2023 – Health

Traces of ancient viruses — which have spent millions of years “hidden” in human DNA — help the body fight cancer.

That was the conclusion of a study conducted by scientists at the Francis Crick Institute, which showed that dormant remnants of these micro-organisms are awakened when cancer cells escape the body’s control.

This dynamic ends up unwittingly helping the immune system to target and attack the tumor.

The researchers hope to use the discovery, published this week in the journal Nature, as a starting point for developing vaccines that could boost cancer treatment or even prevent the disease.

They saw a connection between a higher survival rate from lung cancer and the performance of a specific part of the immune system — the so-called B-cells — that cluster around tumors.

B-cells produce antibodies and are best known for their role in fighting infections, such as the one caused by Covid-19.

The observation of these cells in cases of lung cancer drew the attention of scientists, who initially did not understand why they had targeted the region affected by the disease.

A series of experiments using patient samples and tests on animals revealed that they were trying to fight what they identified as a virus.

“At the end of the day, the antibodies were recognizing remnants of what is known as an endogenous retrovirus,” explains Professor Julian Downward, Associate Director of Research at the Francis Crick Institute.

Retroviruses multiply by inserting a copy of their genetic code into their hosts’ DNA.

More than 8% of what we think of as “human” DNA actually comes from this process. Some of these retroviruses became part of our genetic code tens of millions of years ago and were shared during the evolutionary process; others, more recent, may have entered human DNA a few thousand years ago.

Part of these genetic sequences brought by viruses was, over time, incorporated and started to perform useful functions within our cells. Others, however, are strictly controlled by the body to prevent them from spreading.

When a cancer spreads in the body, however, the cancer cells begin to grow out of control — and the hitherto rigid mechanisms for containing the genes of these ancient viruses end up being lost.

These genetic instructions are no longer able to give rise to 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 believing that the tumor cells are infected and tries to eliminate the virus, so it’s kind of an alarm system,” says Professor George Kassiotis, head of retroviral immunology at the biomedical research centre.

The antibodies then call upon other parts of the immune system that act to eliminate the “infected” cells, and so, while the immune system tries to kill a virus, it ends up targeting the cancer cells.

Kassiotis points out that this is a remarkable role reversal for retroviruses that, in their heyday, “could have caused cancer in our ancestors” because of the way they invade our DNA, but are now protecting us from cancer.

“I find it fascinating,” he adds.

The study describes how this process happens naturally in the body. The researchers now want to understand how they can leverage this effect by developing vaccines to teach the body to hunt endogenous retroviruses.

“If we can do this, it is possible to think not only of therapeutic vaccines, but also of preventive vaccines”, emphasizes Kassiotis.

The research comes out of the TracerX study, which has been tracking lung cancer in an unprecedented level of detail and which this week showed the cancer’s “almost infinite” capacity to evolve – a conclusion that has led the authors to call for more focus on cancer prevention. , as he is very difficult to contain.

“We all have ancient viral DNA in our genes, passed down from our ancestors. This fascinating research has highlighted the role it plays in cancer and how our immune systems can recognize and destroy cancer cells,” comments Claire Bromley of Cancer Research UK, an organization of cancer research in the UK.

In his view, “more research” is needed to develop a vaccine against the disease, “however, this study adds to the growing body of research that may one day see this innovative approach to treating cancer become a reality.”