WHY VIRUSES AND BACTERIA?
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According to the World Health Organization (WHO), cancer-causing infections are deemed responsible for nearly 25% of cancers in low and middle-income countries. Globally, close to 1 in 6 deaths are now attributed to cancer.
There is more pressing evidence that chronic viral and bacterial infections are directly related to some cancer origins. We hope to facilitate ground-breaking research to further understand relationships between viral and bacterial infections and cancer formation, to monitor and identify infections and cancers, and/or to prevent infection and cancer formation, ultimately pushing forward the science needed to prevent cancer deaths.
Below, find examples of important viruses and bacteria associated with cancer.
VIRUSES
From 2010 to 2015, an estimated 42,700 people per year were diagnosed with cancers associated with the human papillomavirus (HPV) according to the CDC. HPV is most commonly associated with the development of cervical cancer, although it can also induce cancer in several other areas of the human body. But HPV is not the only virus capable of inducing cancer growth. Chronic Hepatitis B and Hepatitis C infections are associated with increased risk of liver cancer. Less than half of liver cancers in the United States are associated with Hepatitis infections, but more than half are associated with the viruses globally.
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Artistic illustration of Human Papilomavirus
Further, the Epstein-Barr virus is another suspected culprit in cancer growth. This virus increases risk of generating nasopharyngeal cancer and fast-growing lymphomas as well as Hodgkins lymphoma and stomach cancers. While the rate of people infected with Epstein-Barr developing an associated cancer is extremely low, the causation for viral infection to cancer is not currently well understood. Additionally, the human t-lymphotrophic virus-1, less common in the United States, is associated overseas with cancers lymphotcytic leukemia and non-Hodgkins lymphoma.
While HPV and Hepatitis are suspected to play a major role in cancer formation through chronic inflammation and cellular stresses, the t-lymphotrophic virus may act through a different mechanism. As a retrovirus, it rewrites its own RNA into DNA to reproduce, and in turn can interact with the human chromosome, changing the mechanism of cellular division which may lead to the development of cancer cells. Collectively, the information on viruses listed here is a mere glimpse of scientific knowledge on virus-cancer relationships. For more information on viruses and cancer formation, consult the embedded links at the bottom of this page.
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BACTERIA
In recent years, researchers have demonstrated strong links between certain bacterial infections that generate chromic inflammation and/or carcinogenic metabolite generation with resulting cancer. The most concrete evidence for this relationship is found in gastric cancer, which killed approximately 738,000 people in 2008, and is the second most common cause of cancer-related fatalities globally. The primary identified cause and strongest known risk factor for gastric cancer is the bacterium Helicobacter pylori (H. pylori), according to the National Cancer Institute.
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Artistic illustration of Heliobacter pylori
Approximately two thirds of the adult global population hosts the bacterium, but risk factors for developing gastric cancers and specifics of the bacterial infection are believed to play a role in the development of H. pylori-induced carcinogenic growth. An enhanced understanding of bacterial interaction mechanisms and human cells is needed to explain the complex role this bacteria plays in cellular life cycles.
In addition to the H. pylori bacterium, increased attention has been placed on the role of Chlamydia trachomatis as a bacterium capable of facilitating the formation of cervical cancer, although its impact without the presence of HPV is not well understood. Further, mutagenic bacterial metabolites from bacterial infections are believed to play a role in colon cancers as well. For additional information, see the attached links embedded in our website, including a list compiled by WHO on biological agents associated with cancer.
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CITATIONS
1. Cited by WHO: Plummer M, de Martel C, Vignat J, Ferlay J, Bray F, Franceschi S. Global burden of cancers attributable to infections in 2012: a synthetic analysis. Lancet Glob Health. 2016 Sep;4(9):e609-16. doi: 10.1016/S2214-109X(16)30143-7.
2. http://www.who.int/news-room/fact-sheets/detail/cancer
3. https://www.cdc.gov/cancer/hpv/statistics/index.htm
4. https://www.cdc.gov/hpv/parents/cancer.html
6. https://www.cancer.gov/about-cancer/causes-prevention/risk/infectious-agents/h-pylori-fact-sheet
8. https://www.ncbi.nlm.nih.gov/pubmed/20709622
9. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1518971/
10. http://monographs.iarc.fr/ENG/Monographs/vol100B/index.php