Hitchhiking Virus Escapes Immune System to Fight Cancer

Jun 19, 2012 | David Bui | Research & Policy

A new study published in the Science Translational Medicine journal reveals the discovery of how the reovirus, the virus associated with the common cold, may one day be used as treatment against certain cancers.

The reovirus is an oncolytic virus: a virus that attacks cancer cells while leaving healthy cells unscathed. Prior studies have well documented the reovirus’ anti-cancer effects. The virus attacks cancer cells in two ways; it directly infects cancerous cells, killing them the way other viruses destroy healthy cells, and it stimulates the immune system to kill off remaining cancer cells—almost like a vaccine.

Oncolytic viral therapy has been researched for some time now and shows promise in treating certain cancers in early-phase clinical trials. However, getting the oncolytic viruses to the cancer cells has proven challenging.

One problem is that the viruses are attacked by our immune systems as soon as they enter the bloodstream, so they need to be directly injected into the tumors. When tumors are deep within the body, direct delivery of the viruses may not be possible. This limits its therapeutic use to a specific subset of cancers.

The reovirus, as researchers from Leeds University and the Institute of Cancer Research found, surpasses these barriers.

The researchers discovered that the reovirus is able to avoid the body’s immune system by “hitching” rides within blood cells, essentially hiding from antibodies that would normally destroy them, until they reach cancer cells. This discovery of the reovirus’ ability to evade antibodies makes its use in cancer therapies potentially effective for a wider range of cancers.


The study included ten patients with advanced cancers that had spread to their livers. Study participants were given doses of the reovirus treatment in the weeks leading up to a surgery intended to remove the cancerous tissues. In post- surgery examinations of the removed tissues, the researchers found active reoviruses in cancer tissues, but not in normal liver tissue. This finding confirmed that the reovirus had survived the bodies immune response long enough to reach the cancer cells.

More importantly, the reovirus was able to reach the cancer cells deep in the liver despite being injected into the blood stream. The outcome of the study suggests that the reovirus may be able to reach and treat a wider range of cancers than originally thought. It also shows that the reovirus’ preference for attacking cancer cells may result in fewer side effects for patients.

The study team hopes the discovery will encourage the use of oncolytic viral therapies in cancer trials and treatment.

 

Written by David Bui

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