Possible Link Found Between
Virus and Colon Cancer
Excerpt By Amy Norton, Reuter's Health

NEW YORK (Reuters Health) - A common type of herpesvirus may play a role in the development of colorectal cancer, preliminary research suggests.

The virus, called cytomegalovirus (CMV), is widespread and normally causes no problems in healthy individuals. As many as 90% of US adults may carry CMV, which in most cases remains dormant.

However, some research has suggested CMV infection can help promote heart disease, possibly by causing long-term inflammation in the body. Now the new study hints at a potential role in cancer of the colon and rectum--although, the lead author told Reuters Health, it does not prove the virus helps cause the cancer.

Looking at samples of colorectal cancer and nearby healthy tissue from 29 patients, the Alabama researchers found evidence of CMV proteins in most of the tumor samples, but not in healthy tissue. The proteins also turned up in most of the colorectal polyps the researchers studied. Colorectal polyps are usually benign growths, but over time, some may develop into cancer.

The study authors, led by Dr. Charles S. Cobbs of the University of Alabama, Birmingham, report the findings in the November 16th issue of The Lancet.

In addition to detecting CMV in patients' tumor samples, the investigators found in lab experiments that infecting colon cancer cells with CMV produced two types of proteins that are thought to contribute to the progression of colon cancer.

Still, none of this establishes a cause-and-effect relationship, Cobbs pointed out in an interview. And considering how pervasive CMV infection is worldwide, Cobbs said his "suspicion" is that a number of other factors would have to conspire with CMV for colorectal cancer to develop.

Exactly how CMV might promote colorectal cancer is unclear, but there are several possibilities, according to the researchers. For example, CMV-infected colon cancer cells might gain a "growth advantage" or, alternatively, a shield from the immune response that might normally kill them. Research has shown that CMV has the ability to evade key immune-system components.

The finding that CMV could have a role in cancer is something of a surprise, Cobbs pointed out. But he and his colleagues had previously found a potential tie to brain tumors, and they are continuing to study what role, if any, the virus might have in other cancers.

If more research does confirm that CMV contributes to colon cancer, Cobbs said it is "theoretically possible" that the CMV vaccines researchers are working on could one day help prevent colorectal cancer.

Colorectal cancer is the second-leading cause of cancer deaths in the US. Established risk factors include older age, family history of the disease and the inflammatory disorder ulcerative colitis. Health experts recommend that men and women begin regular colorectal cancer screening at age 50.

SOURCE: The Lancet 2002;360:1557-1563.

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