Virotherapy
WHAT ARE ONCOLYTIC VIRUSES?
Oncolytic viruses target tumors through signalling antigens and injecting viral DNA into unhealthy cells leading to lysis.
BACKGROUND
Oncolytic Viruses infect and kill tumor cells without harming healthy cells; these cells can be found in nature or be genetically modified in the laboratory. Because of their ability to trigger the immune system to respond to the cancer cells, researchers hope that oncolytic viruses can be used as a tool to treat cancer. Currently, the Food and Drug Administration has only approved one oncolytic virus, talimogene laherparepvec, use to treat melanoma. Melanoma is the most dangerous type of skin cancer because of rapid ability to grow and spread. Most likely due to the overexposure of ultraviolet light, DNA can be damaged causing skin cells to rapidly produce which causes malignant tumors to form. Melanomas can either look like moles, typically black or brown, or develop from moles. The virus used to treat melanomas are genetically modified form of herpesvirus; this virus is crucial because some patients diagnosed with melanomas can not be surgically removed.
PROCESS
The oncolytic virus would first attach to the cancer cell, which is the host cell for the virus. The oncolytic virus would penetrate and release an enzyme that will dissolve its cell wall which allows the virus to inject the viral DNA into the the cancer cell. Then, the oncolytic virus undergoes biosynthesis; a process where the viral DNA replicates and protein synthesis occurs, creating virus parts. Afterwards, these viral parts are assembled that later eventually leads to the death of the cancer cell. As this occurs, the cell releases tumor antigens that enables the immune system to recognize and differentiate between the cancer cells from the healthy cells. This may eventually lead to a local response (nearby tumors) or tumors throughout the body.
LYTIC CYCLE
ATTACHMENT
The virus first attaches to the surface of the host cell, in this case the cancer cell.
PENETRATION
The virus would then release the viral DNA into the cancer cell.
BIOSYNTHESIS
The virus then replicates its DNA and protein synthesis occurs which allows the virus to create its parts. During this process the viral DNA becomes active and completes the lytic cycle.
ASSEMBLY
The viruses assemble their parts in this stage.
RELEASE
At the end of this cycle, the host cell dies which allows for the releasing of newly made viruses.