The word salmonella conjures up images of raw meat, food poisoning, and days spent close to the bathroom with nasty stomach pain. But that may all change if salmonella can be tweaked to become a cancer-fighting agent, as scientists hope.
Researchers at the University of Minnesota Masonic Cancer Center in Minneapolis are trying to use salmonella to attack tumors and destroy them. They believe it makes sense to put salmonella to work where it's most at home in the body -- around the organs of the abdominal region such as the liver and spleen and in segments of the digestive tract like the colon.
The scientists altered a strain of salmonella to make it weaker and therefore unable to make the host ill. They also gave their special strain of salmonella the ability to make Interleukin 2 (IL-2). IL-2 is a naturally occurring substance in the body that can stimulate the immune system and activate the growth of T-cells and Natural Killer cells, both of which can destroy cancerous growths.
Their theory is that since salmonella always travels to the core of the body and is most comfortable establishing itself in the gut, it will find any tumors existing there and penetrate them. Once inside, the salmonella will release the IL-2 that will then trigger the immune system to obliterate the cancer from within the tumor. So far, animal trials have been conducted with great success. The IL-2 salmonella has worked to demolish tumors in test mice. Recently, the researchers began testing the salmonella variant on humans as well.
Because it is so talented at invading cells, salmonella has been used in other research as an illness fighter. At the University of California, Berkeley, scientists have reprogrammed salmonella to treat cytomegalovirus (1) -- part of the herpes virus family that can cause cold sores and roseola -- and found it worked extremely well in initial animal trials. In both this study and the one using salmonella to fight cancer, the treatment can be taken orally instead of as an injection due to salmonella's ability to survive the digestive tract.
This re-engineering of salmonella is not the first time researchers have put bacteria to work to benefit people rather than harm them. Aside from the well-known cases, such as using live, weakened polio virus to create the vaccine that protects us from this disease, various bacterium have been put to use in labs to help us in many ways. Bacillus subtilis can grow riboflavin, an essential vitamin that helps our bodies create necessary proteins. When developed in the laboratory, the riboflavin is grown within the bacteria, then separated from it so it can be added to fortified grains such as bread and cereal. E. coli has been likewise re-engineered to produce vitamin B-12.
Other bacteria have been used in experiments in which human genetic coding was added. This allows for the creation of human proteins that can form important body chemicals that some people cannot produce enough of on their own. Lab work in this area has been quite successful in creating both insulin and human growth hormone using bacteria as the hosts. (2) And of course, the active ingredient in Tamiflu is now synthesized by re-engineered E. coli.
If it turns out that salmonella can work as well as the University of Minnesota researchers suggest -- with the ability to target the tumors and destroy them while leaving the rest of the body intact -- that would be quite a breakthrough. And it would certainly be a huge improvement over the often-toxic forms of traditional medical treatment for cancer that we have available today.
1 Bai, Yong; Gong, Hao; Li, Hongjian; Vu, Gia-Phong; Lu, Sangwei; and Liu, Fenyong. "Oral delivery of RNase P ribozymes by Salmonella inhibits viral infection in mice." Proceedings of the National Academy of Sciences. 7 February 2011. National Academy of Sciences. 19 March 2011. <http://www.pnas.org/content/108/8/3222.abstract?sid=36ac2350-5290-4dce-a5ae-a25ac15e6f1c>.
2 "Harnessing Invisible Power." Science Clarified. 2009. Advameg, Inc. 20 March 2011. http://www.scienceclarified.com/scitech/Bacteria-and-Viruses/Harnessing-Invisible-Power.html.