In a novel approach to fighting cancer cells, researchers at Duke University have found that a modified poliovirus enables the body to use its resources to fight off cancer. The research was published recently in the journal Science Translational Medicine.
The modified poliovirus, whose full name is recombinant oncolytic poliovirus (PVS-RIPO), has been in clinical trials since 2011 to see its effectiveness in fighting aggressive forms of brain tumors. This study sought to investigate how PVS-RIPO works.
Attaching then attacking
The goal of the Duke study was to examine the behavior of the poliovirus in two human cell lines: melanoma and triple-negative breast cancer. They found that those cancerous cells have an excess of a certain protein that acts as a receptor for the poliovirus. Because of this, the poliovirus attaches itself to these cancer cells.
Once attached, the poliovirus starts to attack the cancer cells. These attacks cause a release of antigens by the tumor. This release alerts the body’s immune system because it does not recognize the toxic antigens. The immune system gets to work attacking the same cells the poliovirus is attacking. While the immune system is making its attack, the PVS-RIPO infects the dendritic cells and macrophages.
What are those cells? Dendritic cells have the job of processing antigens and basically “showing them” to T cells, a type of immune cell in the body. T cells play a central role in cell-mediated immunity. Macrophages are large white blood cells whose role is to rid the body of toxic substances and other debris.
The Duke research found that once the poliovirus infected the dendritic cells, these cells then told the T cells to begin an immune attack. Once this process was initiated, it continued. This made the cancer cells vulnerable to the immune system’s attack over a longer period. This vulnerability kept the tumor from regrowing.
One of the leads on the study, Professor Smita Nair, an immunologist in the Duke Department of Surgery, explains what is going on. “Not only is the poliovirus killing tumor cells, but it is also infecting the antigen-presenting cells, which allows them to function in such a way that they can now raise a T cell response that can recognize and infiltrate a tumor,” he explains in the study. “This is an encouraging finding because it means the poliovirus stimulates an innate inflammatory response.”
The double benefits of the poliovirus both attacking the cancer cells on its own and initiating an alarm in the dendritic cells that summons an immune response merits additional future research, the study’s authors note, “Our findings provide clear rationales for moving forward with clinical trials in breast cancer, prostate cancer, and malignant melanoma.”