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In the first part of this series about viruses, we looked at general virus structure and function. As is true with most organisms, structure and function are thoroughly intertwined. This week we continue the series with a look at the role viruses play in cancer.
Researchers have long attempted to elucidate the role that viruses play in cancer. There is a mountain of circumstantial evidence that viruses can cause certain types of cancer. At the same time, much remains to be determined about the exact mechanisms of viruses in cancer.
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Image courtesy of Linda M. Stannard, University of Cape Town. |
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Mechanisms
Scientists have been able to discern some commonality among viruses that cause tumors. The tumor viruses change cells by integrating their genetic material with the host cell's DNA. Unlike prophages, this is a permanent insertion in that the genetic material is never "removed."
The insertion mechanism can differ depending on whether the genetic material in the virus is DNA or RNA. In DNA viruses, the genetic material can be directly inserted into the host's DNA. RNA viruses must first transcribe RNA to DNA and then insert the genetic material into the host cell's DNA.
Linkages
Several viruses have been linked to certain types of cancer:
- The Epstein-Barr virus has been linked with Burkitt's lymphoma.
- The Hepatitis B and C viruses have been linked with liver cancer in people with chronic infections.
- HTLV-I, a retrovirus, has been linked to T-cell leukemia.
- Papilloma viruses have been linked with cervical cancer.
Similarly, research with retrorviruses is proving to be a fertile topic area for finding out important information about the underlying mechanisms of viruses in cancer.
Share Your Opinions
What do you think? What role do you think viruses play in cancer? Would you classify a virus as living or nonliving? Come on over to the Biology Forum and share your thoughts, opinions and feelings. Until next time...
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