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When Two Wrongs Make a Right

Poliovirus, which was once a serious threat to the lives of many, is now playing a vital role in the fight against the deadliest types of brain cancer. A genetically modified version of the poliovirus has been used to treat some cases of glioblastoma, a type of brain cancer that kills its victims within two years on average[1]. Dr. Matthias Gromeier, a molecular biologist at Duke University, is credited with the discovery of the modified poliovirus. Over the course of 5 years, there have been a total of 22 patients who have used the poliovirus as an attempt to cure their glioblastoma with 11 deaths and 11 patients recovered or in remission[2]. Despite the high number of deaths, the drug is held in high regards because it has shone a light on future advancements in cancer research.

            The poliovirus was chosen because its receptor, cluster of differentiation 155 (CD155), is commonly found on most tumor cells. This discovery prompted scientists to try using the poliovirus to kill tumor cells. However, in order for that treatment to be successful, the disease-causing ability had to be removed from the virus. The development of the genetically modified strain of poliovirus, which is called PVS-RIPO, requires the internal ribosomal entry site (IRES) of the poliovirus to be replaced with the IRES of the human rhinovirus 2[3].This slight change does not completely alter the functions of the poliovirus, but reduces its intensity, preventing damage to the nervous system and accidental death of the patient. This is important to the success of PVS-RIPO. When injected in the body, the virus attacks the cancerous tumor cells and partially kills the cancer. The rest of the work is done by the immune system, which attacks the site of the poliovirus and thus the tumor[4]. As the immune system works to kill the disease, the tumor size increases and appears to worsen over the span of two months. Eventually the inflammation decreases and the tumor slowly disappears, placing the patient in remission. A safe remission period is defined as 6 months without any signs of a tumor, which has become a fairly common result of patients using the poliovirus strain.

            Although there will need to be improvements made to the PVS-RIPO treatment, there are still many accomplishments to look forward to. Many patients are still in remission up to 36 months after treatment, which is unheard of for cases of glioblastoma2. Looking into the future, Dr. Gromeier and his colleagues at Duke are hoping to test this virus on other types of cancer to determine the versatility of PVS-RIPO4.

-  LR

[1] "Glioblastoma (GBM)." American Brain Tumor Association. American Brain Tumor Association, 2014. Web.

[2] Pelley, Scott. "Killing Cancer." CBS 60 Minutes. CBS Interactive Inc., 29 Mar. 2015. Web. 24 May 2016.

[3] Goetz, Christian, and Matthias Gromeier. "Preparing an Oncolytic Poliovirus Recombinant for Clinical Application against Glioblastoma Multiforme." Cytokine & Growth Factor Reviews 21.2-3 (2010): 197-203. Web.

[4] Gromeier, Matthias, MD, and Gordana Vlahovic, MD, MHS. "Targeting Cancer with Genetically Engineered Poliovirus (PVS-RIPO)." The Preston Robert Tisch Brain Tumor Center at Duke. Duke University Health System, 2016. Web. 26 May 2016.

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