Doctors use reovirus to treat liver cancer
The so-called reovirus usually causes mild cases of respiratory infections, especially in children. However, researchers have now discovered that the virus could be used as an immunotherapy to fight liver cancer and hepatitis C. This form of therapy could lead to improved treatment for many patients around the world.
An international team of scientists found that a widespread virus could be used as a therapy for liver cancer and hepatitis C. The experts published the results of their study in the recognized medical journal "BMJ".
Three quarters of liver cancer diseases result from HCV or HBV
Viruses cause about twenty percent of all cancers. Viruses associated with liver cancer are a particular problem, with around three quarters of the cases being caused by either the hepatitis C virus (HCV) or the hepatitis B virus (HBV).
Researchers are forcing the immune system to fight tumors and HCV infection
These viruses cause a long-lasting infection within the liver. In some people, the infections then lead to the development of tumors, the experts explain. However, the results of the latest study now show that our immune system can be forced to fight both the tumor and the HCV infection that is responsible for its growth.
The type of treatment could also work for other virus-driven malignancies
"By administering a benign reovirus, so to speak, we convinced the immune system that both the tumor and the underlying HCV infection had to be combated," the doctors explain. In mice with liver cancer caused by hepatitis C, it was observed that the animals respond very well to this type of therapy. This type of treatment could also be applied to other virus-driven malignancies, including blood cancer caused by the so-called Epstein-Barr virus, the scientists say.
Advanced stage liver cancer is very difficult to treat
Liver cancer is the third leading cause of cancer-related death worldwide. The disease killed around 745,000 people in 2012 alone, the authors explain. Even so, liver cancer is only the tenth most common form of cancer. This reflects the difficulties that the treatment of this tumor has in advanced stages.
Many treatments only extend the patient's life
In about 90 percent of cases where surgery is not an option, the treatments used tend to prolong the life of the patient rather than fighting the tumor, the doctors explain. HCV and HBV cause about 30 and 50 percent of these tumors, respectively. HCV is the leading cause of liver transplant surgery in developed countries, the researchers report.
Human immune response is a powerful weapon in the fight against cancer
The results show that one of the most powerful weapons to fight cancer is our own immune response. This approach can take various forms, including the deactivation of so-called immune control points. Alternatively, we can use strategies to “hyper-stimulate” immunity, the experts explain. In this way, the immune system also recognizes and reacts to targets that are normally ignored.
Oncolytic viruses make it possible to treat cancer
Such a strategy involves the use of viruses. But the authors only explain viruses that do not lead to human diseases. These cancer-fighting viruses (oncolytic viruses) are increasingly being used in clinical studies. For example, a drug to treat skin cancer was recently licensed.
Reovirus strengthens the immune response
The current study now focused on a specific oncolytic virus. "We already knew about the reovirus that it could reach tumors in the liver after an injection into the bloodstream," the scientists say. The virus strengthens the immune response of the liver as well as within the cancers. This effect is particularly important because the underlying HCV infection affects the entire organ, only the tumor itself.
Interferon triggers an accelerated immune response
The trigger for the accelerated immune response was a substance called interferon. This is released by the body when there is an aggressive reaction to infection and cancer.
Interferon stimulated by reovirus is extremely effective
Using primary human liver tissue and mice, we were able to show that interferon stimulated by the reovirus works in two ways, the experts explain. First, it directly eliminates HCV in liver or tumor cells. Second, it activates specific immune cells, which are also known colloquially as so-called killer cells. These cells destroy virus-infected cells and cancer cells, the researchers add.
Reovirus therapy also works for HBV liver cancer and Epstein Barr virus blood cancer
The result of the so-called reovirus therapy was the simultaneous elimination of HCV and the direct destruction of liver cancer cells. This culminated in reduced tumor growth within mouse models, the scientists explain. The same approach also worked in models of HBV liver cancer and Epstein Barr virus blood cancer.
Further clinical studies on the effects of similar strategies are necessary
Since the reovirus is already available in a clinically usable form, it is our next step to evaluate clinical studies at an early stage on the effect of these or similar strategies for the treatment of multiple tumors, the authors explain. Hopefully, the results can significantly improve future treatment for cancer patients, the scientists said. (as)