The use of harmless for human viruses to help in the treatment of serious diseases can be called a promising medical technology. For example, adeno-associated viruses are used in gene therapy, which can insert their genome into the host genome. But in the treatment of cancer, the so-called oncolytic viruses help.
One such is, for example, the Zika virus, and it has recently been proven that, when properly used, it effectively kills glioblastoma cells – in most cases, the deadly type of brain cancer.
A new study, conducted by a team from several research centers in the UK, showed that there is another virus that can be used to treat the most aggressive types of brain cancer.
It’s about reoviruses . It turned out that they can act on the principle of immunotherapy – to stimulate immune cells to attack cancer. (By the way, classical immunotherapy and the use of antibodies also showed high effectiveness in fighting some types of cancer).
The trump of reoviruses, according to the authors, is the ability to overcome the blood-brain barrier ( BBB ). It protects the brain of all vertebrates, including humans, from toxins and microorganisms that can enter the central nervous system through the blood.
The BBB consists of a dense layer of endothelial cells surrounding each blood vessel like insulation on electrical wires. With the help of special transport mechanisms, these cells pass only vital molecules and completely block access to deeper layers for any foreign objects.
A new study showed that the reovirus can cross the blood-brain barrier smoothly, after which the virus replicates (multiplies), and it begins to kill cancer cells, and also “includes” the body’s own defense systems.
Scientists note: it was still considered unlikely that a virus could enter the brain through the BBB. And this means that the only way to deliver it to the right place was direct injection directly into the brain. This method is extremely difficult (especially considering that the virus would have to be administered regularly), besides, it is not suitable for all patients.
However, thanks to new data, it became clear that the virus enough to enter the bloodstream. That is, in the case of reoviruses, you can dispense with the usual intravenous infusion, in simple terms, with a dropper.
The authors of the work from the University of Leeds and the Institute of Cancer Research in London believe that reovirus therapy can be used in combination with other cancer treatments to make them more powerful. They have already conducted the first clinical trial of the new method.
Nine patients took part in it, all had cancerous formations – primary or secondary. That is, they were either formed immediately in the brain (these were gliomas – a rapidly growing type of cancer that is difficult to treat and has a poor prognosis), or spread from other parts of the body.
All patients were removed surgically, but a few days before the surgery they were given “viral droppers”.
Once the tumors were removed, the experts carefully examined them and concluded that in each of the nine cases the virus had penetrated the barrier (in some cases, it had penetrated deep into the brain).
The authors specify that the presence of reovirus stimulated the body’s own defense system. Immune cells, known as T-killers , who hunt for cancer cells, seemed to be attracted to a tumor to attack it.
Scientists compared samples of tumor tissues with samples from the control group – patients entering it performed operations without prior introduction of the virus. The analysis revealed in the samples of patients from the experimental group higher levels of interferons – proteins, which activate the immune system of the body.
“This is the first time that a therapeutic virus has been shown to be able to pass into the brain through the blood barrier, this type of immunotherapy can be used to treat a large number of people with aggressive brain cancer,” said oncologist lead author Adel Samson .
Co-author of the study, Professor Alan Melcher ( Alan Melcher ) explains that our immune system is not very “seeing” cancer. First, the cells of the tumor look like the own cells of our body, and secondly, the cancer can deceive the immune system, weakening it and making it “close your eyes” to the disease. But the viruses recognize immune cells very well.
“In our study, we were able to show that the reovirus can infect cancer cells in the brain, and, importantly, brain tumors infected with reovirus become more visible to the immune system,” Melcher explains.
According to him, this small-scale clinical trial allows you to ask a question of great importance and to obtain information that should be checked in the future both in laboratory and in clinical studies.
Actually, new clinical trials have already started. Now doctors use reovirus in combination with standard treatment – radiation and chemotherapy, which follow after operations.
In particular, one of the patients with glioblastoma (the most frequent and most aggressive form of the brain tumor) should receive a total of 16 doses of the virus a few months after the removal of the tumor, along with chemotherapy and radiotherapy.
Although previous work showed that the reovirus gets to the site of tumor formation after a single injection into the body, the doctors decided to repeatedly give it to patients to strengthen the immune response.
“The presence of cancer in the brain weakens the body’s own immune system, the presence of reovirus counteracts this and stimulates the protective system to action.We hope for an additional effect: the virus will strengthen the body’s immune response and increase the number of tumor cells that will be killed by standard treatment.” Susan Short ( by Susan Short ), who runs the new challenges.
This study will show how well patients tolerate combination therapy and what side effects it can cause (so far only minor effects associated with influenza have been noted).
More information on the new method of fighting brain cancer is described in an article published in the publication Science Translational Medicine.
By the way, it was previously revealed that stem cells that produce the necessary toxin can fight metastases of brain cancer.