But what if a well-known virus just might be able take out this mortal enemy -- and win?
Look out cancer, here comes polio.
For those who are too young to remember, polio was a once-feared world epidemic. Swimming pools, lakes and any other possibly infectious places were cleared during polio season due to a risk of transmission.
Polio, medically referred to as poliomyelitis, is a rapidly spreading virus that ultimately can affect the central nervous system. That’s how President Franklin D. Roosevelt – and many others -- became paralyzed.
Though polio still exists, it has nearly been eradicated due to the vaccine itself and a unified global effort to eradicate the virus. In fact, since 1988, the number of worldwide reported polio cases has decreased by more than 99 percent. That’s a reduction from about 350,000 reported cases in 1988 to 359 reported cases in 2014.
The places where polio has is still seen are few and far between. These days, Pakistan and Afghanistan are the only countries with recent polio infections.
That said, there is still no cure for polio. That’s why most of us have been vaccinated.
So just what does brain cancer have to do with polio?
Glioblastomas are some of the deadliest brain cancers. According to the American Brain Tumor Association, “Glioblastomas (GBM) are tumors that arise from astrocytes -- the star-shaped cells that make up the ‘glue-like,’ or supportive tissue of the brain. These tumors are usually highly malignant (cancerous) because the cells reproduce quickly, and they are supported by a large network of blood vessels.”
The ABTA reports the survival time for adults with this type of brain cancer as just 14.6 months to three years depending upon the type.
This is where polio meets cancer. And polio may have an edge. Years of research have become a reality.
Researchers at Duke University’s Preston Robert Tisch Brain Tumor Center are injecting a genetically engineered poliovirus called PVS-RIPO directly into brain tumors in an attempt to kill cancer cells. This approach has shown potential in a small study.
“We achieved this feat by genetic engineering to remove poliovirus’ inherent disease-causing ability (a piece of genetic code of a cold-causing rhinovirus…spliced into the poliovirus genome),” reports the Preston Robert Tisch Brain Tumor Center.
Though the concept of killing cancer with viruses is said to have been around for nearly a century, technology has changed the game. That’s why the use of oncolytic (cancer-fighting) viruses has not emerged until recent times.
So just how does this treatment work?
The modified virus is injected directly into the tumor, and experts say that through this process, the virus infects tumor cells and ultimately kills them. But this process isn’t as easy as it sounds.
According to the Preston Robert Tisch Brain Tumor Center, “to work against cancers in patients, oncolytic viruses must target cancer cells for infection, and they must kill them. At the same time, they must be safe. Accomplishing this is very difficult scientifically, and only very few viruses are suitable as cancer-fighting agents in the clinic.”
The reason why this works is nothing short of amazing.
“PVS-RIPO naturally infects almost all cancer cells, because the receptor for poliovirus (which is used for cell entry) is abnormally present on most tumor cells. PVS-RIPO kills cancer cells, but not normal cells, because its ability to grow (and kill) depends on biochemical abnormalities only present in cancer cells. Safety testing in non-human primates and human patients has shown no nerve cell killing, no ability to cause poliomyelitis, and no ability of PVS-RIPO to change back to wild type poliovirus that can cause poliomyelitis,” says the Preston Robert Tisch Brain Tumor Center.
When the poliovirus comes into contact with tumors, the human immune system naturally responds and does what it does best. It fights -- hard.
“There are many events following PVS-RIPO infusion into the tumor that can contribute to such an outcome. The human immune system is trained to recognize virus infections and, thus, responds vigorously to the infected tumor. Unraveling why and how the immune system attacks tumors that were infused with PVS-RIPO is a major research goal,” of the study, according to the Preston Robert Tisch Brain Tumor Center.
Researchers say that Phase I clinical trials in the project are ongoing, and they hope that this will be expanded in the future.
“We plan to extend these studies (Phase II/III) in a quest to establish PVS-RIPO as a possible therapy for brain tumors. In addition, PVS-RIPO has the potential to work for other types of cancers. The reason for this is that the mechanisms responsible for PVS-RIPO’s effects against brain tumors broadly apply to almost all cancers,” according to information published on the project’s website.
In addition to current efforts to understand why PVS-RIPO is effective in some patients, researchers are trying to determine immune system responses in relation to PVS-RIPO. Future clinical trials could include brain tumors in children and tumors outside the brain in an effort to apply this research to other types of cancers.
According to information published by Duke, the PVS-RIPO trial is available for recurrent glioblastoma patients with only one tumor. The tumor must be surgically accessible; the size must be no smaller than 1 cm and no larger than 5.5 cm; and the tumor must be located at least 1 cm away from the ventricles. Prior exposure to bevacizumab (Avastin) is permitted. For further information, contact the Preston Robert Tisch Brain Tumor Center at Duke at 919-684-5301.