Common Virus Found Associated with Colon Cancer

A study has found an association between a common human virus and colon cancer, suggesting that treatment or vaccines against the virus may prevent colon tumors. The study was published in the December 2002 issue of Cancer Research.

The virus, called JC virus (JCV), infects more than 90% of the worldwide population, usually during childhood, according to the researchers. The virus is most likely to infect humans through the upper respiratory tract, but remains in a latent stage in most people throughout their lives. JCV can become active, however, in people whose immune systems are depressed and may contribute to cancer in the brain or cause progressive multifocal leukoencephalopathy.

The virus may also enter humans orally through contaminated food or water. In fact, the JCV particles survive in raw sewage. "Re-infection of the human population through contaminated water or food can take the virus into different organs, which in this case may be the intestinal tract,” says Kamel Khalili, Ph.D., a co-investigator and professor and director of the Center for Neurovirology and Cancer Biology at Temple University (Philadelphia, PA, USA; www.temple.edu).

Once in the intestinal tract, JVC expresses the viral protein T-antigen, which has oncogenic potential and associates with beta-catenin, a protein that controls cell division and balances many biologic events in cells. The T-antigen deregulates the function of beta-catenin, which induces the growth of tumors. Gene amplification showed the presence of the viral early genome in 22 of 27 tumors sampled, and the expression of the viral proteins T-antigen and Agnoprotein was found in more than 50% of the samples.
The researchers are not certain whether the JC virus actually causes tumors or is a co-factor or whether its presence is simply a coincidence.

"We can start developing strategies and vaccines against JC virus, which will hopefully lead to the prevention of the tumors it may induce,” notes Dr. Khalili.




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