How can a virus cause cancer? | CTCA
In the s and '70s, as part of a nationwide war on cancer, U.S. virologists took A workshop on the relationship between breast cancer and viruses. Pinpointing the links between infections and cancer poses a huge Many viruses make us feel unwell, but don't have any link to cancer. The Epstein-Barr virus (EBV) has been associated with certain cancers, but the mechanisms of how the virus causes tumor growth is not yet.
All of the seven criteria do not need to be fulfilled to show plausibility, however, said James GoedertM. What is absolutely necessary, however, is temporality: The cause must be present in the organism prior to the outcome, Rabkin said. And work must be replicated in numerous laboratories. For proving the link between HPV and cervical cancer, gradient and plausibility were very strong: The former meant showing that there was an increase in risk with increasing sexual exposure, and the latter called for evidence that cervical dysplasia preceded cancer.
For gastric cancer and Helicobacter pylori, there had been evidence linking infection with that bacterium to other diseases in the stomach, and finally, to precancerous changes, said Rabkin.
Many years may pass between initial infection and tumor appearance, and most infected individuals do not develop cancer, although, in some cases, immunocompromised people have higher risk of virus-associated cancer, she added.
Think About the Link Between Viruses and Cancer
There is also a synergistic effect between some viruses and environmental co-factors. In the mids, H. The advent of PCR has enabled scientists to scan suspect tissue for nonhuman DNA, facilitating the discovery of new infections. Representational difference analysis, western blot analysis, microarray displays, and other tools have also allowed investigators to see what might be lurking within the cancer. Yale BMC-Jerry Domian George Miller Association and Causation With many cancer-associated viruses, however, investigators have had a tough time proving causation--it may be difficult to detect or simply not there.Thinking about cancer as an infectious disease
The most notable exceptions: HPV and hepatitis B, which is known to cause hepatocellular carcinoma. Both viruses are relatively simple, and the mechanisms that trigger the cancer have been well characterized.
They both suppress p Hepatitis B can also directly integrate into the human genome. The characterization of these mechanisms has helped facilitate treatments: In other cases, the lack of a well-understood mechanism has made it difficult to show cancer causation and thus demonstrate proof of principle for treatments.
Some appear to stimulate cell replication but haven't been shown to provoke malignancies.
Strong associations with these viruses and cancers have, nonetheless, inspired treatments. EBV's apparent role in the development of nasopharyngeal carcinoma in China has been the impetus for a vaccine. Cervical cancer has become much less common in the United States because the Pap test has been widely available for many years. This test can show pre-cancerous changes in cells of the cervix that might be caused by HPV infection.
These changed cells can then be destroyed or removed, if needed.
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This can keep cancer from developing. Doctors may now also test for HPV, which can tell them if a woman might be at higher risk for cervical cancer.
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Nearly all women with cervical cancer show signs of HPV infection on lab tests, but most women infected with HPV will not develop cervical cancer. If the HPV causes abnormal cells to start growing, these cells can be removed or destroyed. HPV and other cancers HPVs also have a role in causing some cancers of the penisanusvaginaand vulva.
They are linked to some cancers of the mouth and throattoo. Smokingwhich is also linked with these cancers, may work with HPV to increase cancer risk. Other genital infections may also increase the risk that HPV will cause cancer. You can get more details in HPV and Cancer. They're given as a series of injections shots. The vaccines can only be used to help prevent HPV infection — they do not stop or help treat an existing infection.
To be most effective, the vaccine series should be given before a person becomes sexually active has sex with another person. The vaccination series can be started as early as age 9. HPV vaccination is also recommended for females 13 to 26 years old and for males 13 to 21 years old who have not started the vaccines, or who have started but not completed the series.
Males 22 to 26 years old may also be vaccinated.
See HPV Vaccines for more on this. Most people in the United States are infected with EBV by the end of their teen years, although not everyone develops the symptoms of mono.