How Viruses Are Being Used to Fight Cancer?

VIRUSES CAN UNDOUBTEDLY be very dangerous, but while they are well known to cause devastating illnesses, a wide variety of them – including measles, polio, herpes and the adenovirus – have recently been used to treat cancer, especially aggressive types. Oncolytic virotherapy is an emerging treatment, with major institutions investing research and time into fine-tuning this therapy.

In 2015, researchers at the MD Anderson Cancer Center at the University of Texas genetically modified the adenovirus, which can cause the common cold, to help treat Glioblastoma Multiforme, a very aggressive brain tumor. Malignant gliomas are both the most common and most lethal type of central nervous system tumors, with glioblastoma being the most aggressive subtype. The current standard of care involves a combination of surgery, radiation and chemotherapy, but even with this treatment these tumors remain incredibly fatal, and after second-line therapy there is currently no standard of care.

The virus is engineered to leave healthy tissue cells alone and target proteins that exist only in the cancer cells. Once the virus detects the particular protein, it replicates continuously until it fills the cancer cells and causes it to explode. After the cancer cell bursts, the unleashed viruses find their way to other cancer cells and the process continues. If the cancer comes back, the virus will recognize it and attack it. In another approach, once the immune system has encountered the engineered virus, it can identify cancer cells that contain the modified virus and destroy them – that is, a cancer cell that was initially able to escape detection by the immune system can now be recognized and eliminated.

What viruses are being used to help treat cancer?

Duke University has used an oncolytic virus to treat Glioblastoma Multiforme by inserting a live, genetically modified polio virus into brain tumors via a catheter. The adapted virus, without the part that causes the viral disease, penetrates the cancer cells and spark an immune response to attack the cancer cells. The rate of overall survival of patients treated with this at 24 months was 21%, compared to 4% in the general population group.

The herpes virus Talimogene Laherparepvec (also known as TVEC) is used to treat melanoma and is currently FDA approved. It is genetically engineered to help shrink the tumor and then activate the immune system to continue to recognize and destroy cancer cells. Unlike other cancer treatments that use viruses, this oncolytic virus is genetically engineered to includegranulocyte-macrophage colony-stimulating factor to help draw immune cells to the tumor. This can further enhance the response of our immune system to fight these once unrecognizable cells.

Most recently a strain of the common cold virus, cocksackie virus (CVA21), has been used to attack and kill bladder cancer cells by triggering a protein that triggers an immune response. In a study, 15 patients at the University of Surrey in England were given the cocksackie virus one week prior to surgery through a catheter. When the tumor samples were analyzed after surgery there was evidence that the virus had targeted and killed some of the bladder cancer cells in all 15 of the patients, with no significant side effects. Once those cancer cells had died, the virus then infiltrated and attacked other cancer cells, leaving the healthy ones intact.

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