Does Bacterial Infection Lead to Increased Risk of Cancer?

Sohini Basu Roy

Reading time: 3 minutes

Every year 2.8 million antibiotic-resistant infections cases occur in the U.S. and more than 35,000 people die due to bacterial infection But one of the main challenges is a consequence resulting from the infection: weakened immune system. This leads to immunodeficiency and thus patients become more prone to other infections and diseases. There are multiple infectious agents in nature that have been linked to cancer including bacteria. Bacteria can affect the integrity of their host cells by manipulating them in various phases of their infection cycle and thus contributing to cancer. Bacterial protein toxins and effector proteins can induce the pathway of host cell DNA damage and therefore are involved in cell proliferation, apoptosis, differentiation and immune signaling. There are two reported mechanisms by which bacterial infection is linked to cancer: a) induction of chronic inflammation and b) production of cancer-causing bacterial metabolites.

Despite extensive research and advances on these mechanistic studies, there are still other risk factors that are not as well known. One of the classes of bacteria known as cancer bacteria can directly cause cancer, generally through chronic inflammatory mechanisms as they infect host cells. For example, infection caused by the bacteria H.pylori causes inflammation and thus damages the inner layer of the stomach, which may lead to gastric cancer. A subpopulation of H.pylori produces a toxin called CagA (cytotoxin-associated gene A); they use a needle-like appendage to inject this toxin into the junction of stomach lining. This toxin alters the structure of the stomach cells and allows other bacteria to more easily attach. Chronic inflammation develops due to the long-term exposure to these bacteria, which ultimately increases the risk of developing gastric cancer. Those strains of H.pylori which produce this toxin are known as cag A positive.

From randomized clinical trials, it was found that short-term treatment with antibiotics can reduce the incidence of gastric cancer. According to the Centers for Disease Control and Prevention (CDC), people should be tested and treated for H.pylori if they have an active history of ulcers, and this preventative measure may reduce the change of H.pylori-induced gastric cancer. Beyond H.pylori, there are other viruses and parasites which are also responsible for the direct link to cancers.

Every year, cancer researchers from all over the globe put in research efforts which could enhance the overall quality of a cancer patient’s life. At the same time,  pharmaceutical organizations working in cancer drug development, often in collaboration with academia and government agencies, lead the clinical development of investigational medicinal products targeting cancer. Additionally, scientists continue to research genetic causes for certain cancer types like cancers of the breast and colon. Like other cancer-causing agents, such as tobacco and radiation, learning more about bacterial causes of cancer could lead to early and new ways of preventing and treating disease. Researchers can explore these causes as a new opportunity for identifying cancer risk factors and setting safety standards to reduce public exposure to infectious materials and toxins associated with cancer, ultimately contributing to a healthier population.

Edited by Manisit Das

 Header Image

https://pixabay.com/illustrations/bacteria-bacterium-1453123/

Work discussed

1. Research on Causes of Cancer. National Cancer Institute. https://www.cancer.gov/research/areas/causes
2. Infectious agents. National Cancer Institute. https://www.cancer.gov/about-cancer/causes-prevention/risk/infectious-agents
3. Parsonnet J.,(1995). Bacterial infection as a cause of cancer. Environ Health Perspect. Nov;103 Suppl 8(Suppl 8):263-8. https://pubmed.ncbi.nlm.nih.gov/8741796/
4. Helicobacter pylori and  Cancer. National Institute of Cancer.https://www.cancer.gov/about-cancer/causes-prevention/risk/infectious-agents/h-pylori-fact-sheet
5. Biggest threats and Data.https://www.cdc.gov/drugresistance/biggest-threats.html