June 3 (HealthDay News) -- A person's risk of cancer increases if he or she suffers from DNA-damaging chronic inflammation of the intestine or stomach, such as ulcerative colitis, according to scientists at the Massachusetts Institute of Technology.

Their findings, confirmed in two studies the researchers did on mice, were published in the June 2 online issue of the Journal of Clinical Investigation.

Researchers have long known that inflammation caused by infectious agents, such as Helicobacter pylori and hepatitis C, produces cytokines -- chemicals that can foster cancerous cell proliferation and suppress cell death. This increases the risk of stomach and liver cancers. They had also suspected that the inflammation pathway could also induce cancer, as the body's response to infection includes a release of reactive oxygen and nitrogen that can damage DNA.

Normally, the DNA damage would be repaired by the cells. But, if the DNA repair system is not functioning properly, the damage could induce cell mutations that can lead to cancer, according to the new study.

"It's something that was expected, but it was never formally proven," lead study author Lisiane Meira, research scientist in MIT's Center for Environmental Health Sciences, said in a prepared statement.

As everyone's DNA repair system has a different degree of effectiveness, doctors might now be able figure out which patients are most susceptible to inflammation-induced cancers.

"That variation could influence the susceptibility of individuals and how they are going to respond to a chronic inflammation response," senior study author Leona Samson, director of the Center for Environmental Health Sciences, said in a prepared statement.

SOURCE: Massachusetts Institute of Technology, news release, June 2, 2008