Viruses are commonly associated with the spread of disease and considered harmful to their host. However, there are viruses which are good, and even necessary for us to be alive. Several viruses have certain properties which scientists, nowadays, are trying to manipulate and enhance to find cures for different illnesses. One of such types of viruses, oncolytic viruses are used to kill cancer cells. Oncolytic viruses were first discovered around two decades ago and have become increasingly popular in cancer treatments.
Preliminary Knowledge:
To understand how oncolytic viruses eliminate harmful cancer cells, it is first important for one to understand how cancer infiltrates the body. Cancer is primarily caused by a gene mutation. The way that these gene mutations occur is through factors such as: smoking, radiation, hormones, obesity and more; When a gene mutation happens, which is a frequency phenomena during puberty, the cell goes through its mechanism of recognizing and eliminating that gene mutation. However, when the gene mutation is either not recognized or dealt with, then it results in damaged DNA that will lead into a cancerous cell. Another common way that a cancerous cell occurs is due to the process of cells breaking down being damaged. As cells get old, they break down and new ones are created as a replacement. Though, this process can ‘malfunction’ and abnormal cell growth can occur. Those ‘defect’ cells may form tumors, lumps of tissue, that can be cancerous or not. Once a cell or tissue is considered cancerous then it spreads to other cells/tissues, taking over the body.
Definition of Oncolytic Viruses:
Oncolytic viruses are a vital discovery to treat cancer as they thrive and duplicate inside cancer cells. The viruses break the cancer cell from within by fracturing the cell. By doing so, the contents inside the cell get exposed to the immune system. The immune system is finally able to detect the abnormal protein on the cell surface and eliminate each cancer cell. Not only do these viruses destroy cancer cells by nature but can also be altered to carry other genes into the cancer cells that would amplify any cancer treatment in the process (could be done to shrink the tumor or remove it fully. Interestingly, the modified oncolytic viruses are more effective than oncolytic viruses themselves. Based on experiments done on mice with neck and head tumors, the altered virus shrunk the tumors while the non-modified one gave little to no impact.
Issues:
Though oncolytic viruses have shown promising results against cancer, there are a few quirks that limit this method from being used everywhere. Currently, the biggest issue is the deployment of the oncolytic virus inside the cancerous cell. To be able to do their job, oncolytic viruses must be injected inside the tumor. However, that isn’t always feasible or done correctly, which means that the oncolytic virus must find its way into the center of the tumor. However, to do so would mean that the oncolytic virus has to ‘escape’ the nk (natural killer) cells, whose' purpose is to destroy any ‘wrong’ or ‘defect’ organism in the body – like an unknown virus for example. In the absence of nk cells, APC (antigen presenting cells) would detect the virus and send a signal to the immune system, which would destroy it. If the oncolytic virus is able to pass by either guard cell undetected, then it has to go through the lymphatic network, which is similar to a complex sequence of blood vessels, inside the cell, past the vascular hyperpermeability, excess fluids and protein, and past the large network of proteins and other molecules which support the cell. This rigorous process commonly results in the virus being cleared by the immune system and it’s difficult to ensure that the correct amount makes it inside the tumor to help. To ensure proper results, scientists are trying different paths to deliver the oncolytic viruses into the tumor, such as intravenous (through the veins), intrapleural (through the chest cavity), hepatic artery infusion (release near liver). However, these have not been that well tested and systemic administration (through the circulatory system) seems to have become the preferred way to insert oncolytic viruses.
Oncolytic Viruses have been an enlightening discovery for scientists looking to deplete cancer. This solution, like all others, comes with issues, however actions are being taken to make this viable; now one can only wait to see when oncolytic viruses will be introduced into therapies worldwide and abolish cancer.
References
“Cancer.” Mayo Clinic, Mayo Foundation for Medical Education and Research, 19 Nov. 2024,www.mayoclinic.org/diseases-conditions/cancer/symptoms-causes/syc-20370588#:~:text=A%20number%20of%20forces%20can,and%20a%20lack%20of%20exercise.
Chen, Nanhai G, et al. “Oncolytic Viruses.” Advances in Virology, U.S. National Library of Medicine, 2012, pmc.ncbi.nlm.nih.gov/articles/PMC3384932/.
Messerschmidt, Jonathan L, et al. “How Cancers Escape Immune Destruction and Mechanisms of Action for the New Significantly Active Immune Therapies: Helping Nonimmunologists Decipher Recent Advances.” The Oncologist, U.S. National Library of Medicine, Feb. 2016, pmc.ncbi.nlm.nih.gov/articles/PMC4746082/#:~:text=The%20innate%20and%20adaptive%20immune,%2C%20blood%2C%20and%20lymphatic%20fluid.
“NCI Dictionary of Cancer Terms.” Comprehensive Cancer Information - NCI, www.cancer.gov/publications/dictionaries/cancer-terms/def/natural-killer-cell#:~:text=Listen%20to%20pronunciation,type%20of%20white%20blood%20cell. Accessed 2 Jan. 2025.
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