We know that certain behaviors and environmental factors can lead to cancer, such as smoking and exposure to pollution, but new research suggests that sometimes the body’s own immune response to a virus may lead to cancer-causing mutations. The research is still in its early stages, but if it holds over the course of further testing, it could lead to more effective cancer prevention methods.

The study, from the University of Colorado Cancer Center, showed that enzymes created by the immune system in response to an invading virus may cause cancerous mutations, Gen News reported. According to the research, an enzyme called APOBEC3 is released in response to a viral infection and works by scrambling the virus’ DNA in an effort to disable it. However, it may also scramble the person's DNA as well, increasing the risk of cancer. This hypothesis may help to explain why infections with human papillomavirus (HPV) often lead to cancer.

In their study, researchers showed that the APOBEC3 enzyme caused mutations in genes involved with about 40 percent of HPV-positive head and neck cancers, but only 10 percent of head and neck cancers not related to HPV.

“We know some of the mechanisms that cause these mutations; for example, ultraviolet (UV) radiation can cause mutations that lead to skin cancer and smoking can cause mutations that lead to lung cancer,” explained senior study investigator Dohun Pyeon, Ph.D, Gen News reported. “But there are many more cancers in which we don't know the source of the mutations. The APOBEC3 family can explain how some of these mutations are created. In fact, APOBEC3A can be activated in many ways—not just with HPV infection—and its action may drive a percentage of [cancerous] mutations across many cancer types."

According to the Centers for Disease Control and Prevention, HPV causes most cervical cancers, but is also known to cause cancers of the vagina, vulva, penis, anus, rectum, and oropharynx. In total, about 31,500 cancer cases a year can be attributed to HPV.  There is currently a vaccine that can be given to prevent HPV infections, however, the vaccine is most effective when given at an early age, preferably before exposure to the virus.

If this line of research continues to hold, scientists may be able to develop medicines that prevent APOBEC 3's effect on human DNA.

"Perhaps if you are infected with HPV or have especially high APOBEC3A levels, you could have a drug to prevent any significant mutations,” explained Pyeon.

However, the team also note that there are likely other factors in increasing cancer risk besides the enzyme's effect on mutations, and they hope to investigate further. 

Source: Warren CJ, Westrich JA, Van Doorslaer K, et al. Roles of APOBEC3A and APOBEC3B in Human Papillomavirus Infection and Disease Progression. Viruses. 2017