Can viruses cause cancer? | Live Science • stonescape

Smoking, exposure to toxic chemicals or radiation, and carrying mutations in certain genes are among the most well-known risk factors Cancer. But another cause of cancer is not discussed as often: Viruses.

So which viruses can cause cancer and how do they do it?

There are at least seven viruses which are known to contribute directly or indirectly to the development of cancer in humans. This includes Human papilloma viruses (HPV), hepatitis B virus (HBV), hepatitis C virus (HCV), Epstein-Barr virus (EBV), Kaposi's sarcoma-associated herpesvirus, human T-cell lymphotropic virus and Merkel cell polyomavirus. Additionally, human immunodeficiency virus (HIV) increases the risk of cancer in part by opening the door for cancer-causing viruses to enter the body.

However, it's important to note that only a small percentage of people infected with these viruses go on to develop cancer – in other words, contracting one of these viruses is not a guarantee that you will get cancer. For example, over 90% of adults worldwide are infected with EBV at some point in their lives, but only 1% of cancers are related to EBVthe virus behind “mono”.

Related: What is the oldest known case of cancer in humans?

However, cases caused by all of these viruses continue to occur. An estimate based on 2012 infection numbers suggests that viral infections may be contributing more than 1.4 million cases of cancer worldwide this year, accounting for about 10% of all cancer cases.

“For a long time, many experts were very skeptical that any virus could cause cancer in people,” Dr. Jay Berzofskya senior researcher at the National Cancer Institute told Live Science. “And then as some were discovered, more people jumped on the bandwagon and found more.”

Berzofsky explained that viruses can have carcinogenic or anti-cancer effects through both direct and indirect mechanisms and that each virus can cause cancer through a unique pathway.

Direct mechanisms

One of the most well-known viruses that can cause cancer is HPV, a family of viruses that is responsible for more than 37,000 new cancer cases in the USA every year. The virus is known for its association with cervical cancer, but can also cause anal, oropharyngeal (throat), penile, vaginal and vulvar cancers.

Certain HPV viruses promote cancer Transformation of normal, healthy cells into abnormal tumor cells. This happens because HPV makes certain proteins called proteins E6 and E7 oncoproteinswhich inactivate the natural tumor suppressor systems of healthy cells.

“This allows the abnormal cells to grow uncontrollably.” Dr. Harry Torresprofessor of infectious diseases at the University of Texas MD Anderson Cancer Center told Live Science.

There are more than 200 types of HPV, but only 12 have been strongly linked to cancer. The HPV vaccine, the recommended for all children between 11 and 12 years oldprotects against these high-risk forms of the virus, which can lead to cancer. People can get the shot up to the age of 26 if they have not previously received all recommended doses.

Other viruses that can directly cause cancer, such as: EBV And human lymphotropic T-cell virusdevelop their effects via different cellular and genetic mechanisms. However, the result is ultimately similar: cancer cells begin to multiply aggressively and evade the body's natural defense systems.

Many factors influence whether infection with these viruses leads to cancer. In the case of HPV and EBVCertain strains have greater carcinogenic potential than others. People with weakened immune systems are also at higher risk the development of virus-related cancers. And external factors such as existing mutations or exposure to environmental carcinogens can multiply the likelihood of tumor growth.

Related: New HPV self-swab test is an alternative to Pap smears. This is how it works.

A microscope image showing red colored liver cells

A microscope image of abnormal liver cells in a person with hepatitis. HBV and HCV cause inflammation and scarring in the liver, which increases the risk of cancer. (Image credit: CDC / Dr. Kimbrough)

Indirect mechanisms

Viruses can also cause cancer through more indirect mechanisms. Both HBV and HCV illustrate this. HBV and HCV infect the liverwhich in chronic infections leads to long-term inflammation and liver cirrhosis or scarring of the liver.

“Anything that causes chronic inflammation can potentially increase the risk of cancer,” Berzofsky said.

As the body attempts to repair the extensive damage caused by HBV or HCV by creating new liver cells, there is a possibility that some of these cells may do so mutate and become cancerous. HCV is also associated with non-Hodgkin's lymphoma, a cancer Lymphatic systempossibly because the constant stimulation of the immune system The infection caused by the virus promotes the development of cancer cells.

HIV can too increase the risk of developing cancer through indirect mechanisms. This is because uncontrolled HIV infections cause chronic inflammation and weaken the immune system, making the body more susceptible to other viruses that are directly linked to cancer.

Prevention is key

Although the way these viruses can cause cancer can be complex and multifaceted, Torres says there are methods to prevent and treat some of these infections.

There are vaccines against HPV and HBVboth of which are very effective. For example, absolutely current data was found no new cases of cervical cancer in a large cohort of young women in Scotland who had received the HPV vaccine between the ages of 12 and 13.

Both HIV and HBV spread through multiple body fluids such as blood and semen, while HCV spreads primarily through blood only. Using condoms and never sharing needles can help reduce the risk of contracting infections preventive medication called PrEP is also available for HIV. Note that these viruses can also be transmitted to fetuses and newborns during pregnancy, childbirth, or breastfeeding. Pregnant women are therefore recommended to be tested for infections.

Antiviral treatments can also relieve conditions such as: HIV and chronic HBV to keep them in check, making them less likely to cause cancer. And HCV infections can be cured with antivirals.

Torres is confident that vaccination, prevention and treatment of these viruses can help reduce the global burden of cancer.

“It’s still a work in progress,” he said. “We’re trying to do as much as we can.”

Can viruses cause cancer? | Live Science

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