Infections which cause cancer

Make a difference in the fight against cancer by donating to cancer research. Call us anytime. How can a virus cause cancer? August 30, by CTCA. HBV- and HCV-induced chronic liver infections are rare, but when they occur, they raise the risk of liver cancer. There are still many question marks over the role other bacterial and parasitic infections may play, and which biological mechanisms cause bacterial and parasitic infections to lead to cancer.

Certain molecules or toxins made by the bacteria or parasites can turn on genes in our cells that stop faulty cells committing suicide a normal way our body rids itself of damaged cells and activate genes linked to increased cell division — fundamental processes in cancer.

But our own cells play a role in driving cancer too. Unwittingly, our immune system — our robust lines of defence to protect us against viral, bacterial and parasitic infections — also plays a role in cancer developing. One of the front lines of attack is the release of a powerful cocktail of chemicals, which both kills the trespassers directly and sends out SOS signals to call more immune cells into the area.

This is what causes inflammation — the reddening and swelling you see at an infection site. But when this inflammation persists over long periods of time, some of the chemicals can also damage our own DNA, increasing the risk of cancer.

And as our cells are damaged and lost — either due to the germs themselves or the immune attack — the body increases the number of new cells it makes to replace them. Every time a cell divides it has to copy its DNA and mistakes can happen. So a long-lasting infection and a constant demand for new cells increases the risk from cancer over time by raising the risk of chance mistakes during DNA replication.

In the case of people living in the UK, the answer is thought to be not very great, generally speaking. According to the World Health Organisation WHO , about six in every cancer deaths in developed countries are linked to an infection. And certain infections are strong risk factors for specific cancer types, for example nearly all women who develop cervical cancer are infected with human papilloma virus HPV. But in other parts of the world, cancers with strong links to infections are a much bigger problem.

Shockingly, one in five cancer deaths in developing countries are caused by infection. For example Asia has high rates of stomach and liver cancers linked to Helicobacter pylori and hepatitis infections , and cervical cancer and non-Hodgkin lymphoma associated with human papillomaviruses and Epstein-Barr virus infections are common in Africa. Unravelling the complex relationships between infections and cancer might lead to new tests to identify people at higher risk and also develop preventative treatments like vaccines.

And understanding more about the key mechanisms linking infections with cancer might shed light on innovative new ways to treat the disease. Reference for oncovirus discovery: Ellerman, C. EBV can readily infect and alter the genetic code of human B cells, and may predispose immunosuppressed patients to malignant tumors.

Its early discovery and monoclonal genome made Epstein-Barr virus EBV one of the best studied examples of a cancer-causing virus. Finally, EBV can cause nasopharyngeal carcinoma, which might be a result of virus latency in nasopharyngeal epithelial cells. The genetic mutations caused by EBV infection depend on the viral type and strain, but smoking has been associated with nasopharyngeal carcinoma and possibly leads to EBV reactivation.

Pathologists have been able to harness recent advances in viral oncology to visualize cancer under the microscope. Double labelling of malignant cells, as in Figure 1, shows co-expression of Epstein-Barr virus early RNAs brownish black in color and latent membrane protein 1 LMP1; red in color.

Human papillomavirus HPV is the most common sexually transmitted virus in the world, and is present in up to 79 million Americans. When the HPV genome becomes integrated into human chromosomes, it disrupts an open reading frame and causes the overexpression of two viral oncogenes. This is due to the development and widespread acceptance of cervical cancer screening Pap tests. Kaposi sarcoma-associated herpesvirus is also known as herpesvirus-8 HHV KSHV infects endothelial cells and modulates pathways that control cell proliferation, gene expression, and metabolism.

KSHV may selectively activate and suppress its lytic replication cycles during co-infections with other microbes by sensing resources and cellular conditions. Gastric lymphomas and immunoproliferative small intestinal disease have been most strongly linked to underlying bacterial infection. Because bacterial infections can be cured with antibiotics, identification of bacterial causes of malignancy could have important implications for cancer prevention.

Abstract Bacterial infections traditionally have not been considered major causes of cancer. Publication types Research Support, Non-U.