Contact:
sales@biotechnologyforums.com to feature here

Thread Rating:
  • 0 Vote(s) - 0 Average
  • 1
  • 2
  • 3
  • 4
  • 5
Fighting Cancer With a Virus
#1
Current cancer treatments involve the administration of chemotherapeutic drugs, which act by killing all rapidly proliferating cells. This process, however, results in the killing of many healthy cells in the body, including blood cells, skin cells, and others. This results in very unpleasant side effects, including gastrointestinal problems, decreased ability to fight infections, hair loss, nausea, and skin sensitivities. The treatment options for cancer have not improved over the past several years, so more research into less toxic treatments is desperately needed. In addition to severe side effects, chemotherapy is not always effective at killing all of the cancer cells, in part because it cannot effectively penetrate solid tumors. In addition, many cancer cells have developed mutations that provide protection from such drugs. Cancer cells can increase or decrease the expression of certain receptors on the surface of the cell so that they appear invisible to both drugs and the immune system.

Using attenuated viruses to enhance the effects of chemotherapy drugs has been studied in the past. The virus helps the chemotherapy work more effectively against the cancer cell by weakening the cell so it is more easily killed by the treatment. Adenovirus, which is a causative agent of the common cold, has been studied in many forms for treating cancer. Some genetically engineered strains of adenovirus have been used to infect cancer cells, thereby making them more susceptible to the chemotherapeutics. In addition, adenovirus has been used as a vector for gene therapy, delivering genes to cancer cells that can help remove the cancer from the patient.

Cancer cells tend have deficiencies in the innate immune response that helps protect them from viral infection. This makes cancer cells more susceptible to viral infection than normal, noncancerous cells. Knowing this, researchers wanted to determine if a fast acting virus could selectively infect and kill cancer cells, without harming normal cells. The researcher team first infected melanoma cancer cells in vitro with several strains of a virus called Vesicular Stomatits Virus (VSV). The melanoma cells were efficiently infected and killed by most strains of the virus studied, some of which were able to kill nearly 100% of the melanoma cells. In contrast, healthy melanocytes were not infected as efficiently by VSV. The researchers then transplanted human melanoma cells into mice, and infected the mice with the various VSV strains. Again, the VSV was able to selectively kill the melanoma cells, but not healthy melanocytes in the mice. Taken together, these results indicate that a virus which is able to quickly kill cells, such as VSV, may be able to selectively target and kill cancerous cells, while avoiding healthy cells.

When the researchers treated the melanoma cells with interferon, a protein produced by cells to help protect the cell from viral infection, both the infectivity and the ability of VSV to kill melanoma cells in vitro was decreased. This indicates that the antiviral immune response generated in normal, noncancerous cells, does not function as efficiently in cancerous melanoma cells. If the cancerous cells are not able to produce innate immune molecules, such as interferon, they cannot stop the viral infection and can be easily killed. Because the cancer cells are unable to protect themselves, the melanoma cells become susceptible to killing by VSV. Adding interferon to the melanoma cells allowed the cells to develop an antiviral immune response, thus preventing cellular killing by the virus.

While this study provides valuable proof of concept information that cancerous cells appear to be more susceptible to killing by viral infection, there are still many questions that must be addressed before this information can be translated to humans. For example, a virus would have to be specifically engineered so as not to cause severe illness in cancer patients, who may already be immunocompromised from standard chemotherapies. In addition, the virus would have to be able to target the tissues in which the cancer is found. Also, many viruses cause the development of a memory immune response, that would result in the virus being quickly destroyed by the host. The immunity of a patient to certain viruses may be unknown, making it difficult to determine if the viral infection would help the patient. Lastly, many of the proteins produced by cells during viral infection can act on neighboring cells. This means that a healthy cell may produce interferon that has a protective effect on nearby cancerous cells. This would prevent the virus from efficiently killing the viral cells.

The study presented above is reminiscent of a study done in the late 1800s, in which a physician injected cancer patients with infectious bacteria. The bacteria caused the host to mount an immune response, producing a protein termed Tumor Necrosis Factor (TNF). Unfortunately, many of the patients succumbed to the infection, and this type of immunotherapy did therefore not become popular for treating cancer patients. However, with more sophisticated knowledge of the immune system and how a virus can affect the host, this type of therapy may soon be another option for cancer patients.



References:

https://www.asm.org/index.php/asm-newsro...rmal-cells

http://www.asm.org/images/Communications...lanoma.pdf
Like Post Reply
  

Possibly Related Threads…
Thread
Author
  /  
Last Post



Users browsing this thread:
1 Guest(s)

Fighting Cancer With a Virus00