Using viruses to kill cancer
Here’s an interesting news report via Science Daily, and published recently at the online medical journal PLoS One. Researchers at the University of Copenhagen are reporting that a common virus called vesicular stomatitis virus, or VSV, has potent anti-tumor effects and may be usable as a novel anti-cancer therapy. This story brings to mind my posting here on the blog earlier this year of research to use bacteria to combat tumors, although the mechanisms between these approaches are very different. VSV is a virus that is found in the same family as the rabies virus, and is able to infect a wide variety of animals. VSV is not responsible for any significant disease in humans, and it’s main utility is as an excellent model for studying the biology of viruses in a safe manner.
The immune system is very effective at monitoring the body for foreign materials, and optimally is able to eliminate those foreign objects in the resolution of disease under normal circumstances. Part of this proper immune response is directed at eliminating cancer cells when they are formed. A cancer cell is unique from a bacterium, virus, or other pathogen, in that it is actually one of our own cells that has begun to grow out of control. Fortunately, in many cases this switch to out of control growth at least initially causes the cancer cell to be recognized as a foreign object, and the immune system can eliminate it. Logically, anything that disrupts normal immune system function would then have an effect on the ability of the immune system to eliminate cancer cells. Immunodeficiencies such as AIDS result in the patient being much more susceptible to uncommon tumors that immunocompetent individuals do not get; Kaposi’s Sarcoma is one example. Many cancers, however, have the ability to begin to modulate or alter the immune response against them, which will in turn allow those tumors to progress even with a competent immune response.
So what are we to do then? Most anti-cancer therapies are in fact pretty brutal: surgical resection of the tumor, or chemical treatments with tremendous side effects are the two most common approaches, and if the patient doesn’t die from these treatments, they have a chance of eliminating most of the cancer. Some approaches are a bit more specific, using tailored medicines to hone in one the cancer cells alone. The bacterial treatment written about and linked above is one such approach. Immunotherapies are an approach gaining in effectiveness, and typically involve injections of specific chemicals that turn on or turn off single aspects of the complex web of interactions in the immune response.
The news from Denmark is novel in this respect in that it is utilizing a superinfection to treat another disease. In this study, the researchers noted that VSV infection blocked the production of certain immunostimulatory molecules, and it was these same molecules that were produced by many cancer cells to shut off the immune response against them in the first place. Infection with the virus then allowed the immune system to again be able to eliminate the cancer cells. From their abstract:
Our results show that VSV possess an escape mechanism, which could affect the immune recognition of VSV infected cancer cells. This may also have implications for immune recognition of cancer cells after combined treatment with VSV and chemotherapeutic drugs.
This is not a brand new finding; there have been a number of reports (an old review here) looking at VSV immunomodulation of cancer cells, but this is one of the first reports that begins to look at the specific receptor/ligand mechanism that is at work, and also hints at the perhaps global applicability of using VSV as an anti-cancer therapy in humans. The researchers remark that clinical trials in humans are the next step, and that such trials are already under way in the US.
Posted on September 26, 2011, in Microbes in the News, Strange but True and tagged Cancer cell, Immune system, Tumor, Vesicular stomatitis virus. Bookmark the permalink. Comments Off on Using viruses to kill cancer.