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GM salmonella shows promise as anti-cancer therapy

Genetically modified Salmonella could be used to kill cancer cells while keeping the patient safe from infection, according to a new study.

“There has long been interest in using genetically engineered microbes to target and destroy cells within solid tumors. I think this study goes a significant way in developing some strategies that will help in the overall means of using Salmonella as part of a cancer therapy,” said Roy Curtiss, who was involved with the research.

Dr. Curtiss is professor of microbiology at Arizona State University.

It has been known for some time that certain strains of bacteria, including Salmonella enterica, can kill cancer cells but the down side is that it makes patients sick. The microbe is a common cause of food poisoning.

The challenge for scientists is to find a balance between allowing it to kill the cancer but be safe for the patient.

In this study, the researchers focused on modifying the lipopolysaccharide structure (LPS) of the Salmonella strain to make it less toxic. LPS, found in the outer membrane of bacteria, is one of the major inducers of sepsis, a life-threatening infection.

The researchers deleted genes involved in the synthesis of the LPS and found one particular mutant strain that was the most effective at killing cancer cells and shrinking tumors, and also unable to cause disease.

However, this strain was also less able to colonise the tumors, so the researchers added another genetic modification that allowed the Salmonella to be injected in the mouse in a form that would not harm normal, healthy cells, was effective at colonising tumors, and after entering cancer cells, would turn toxic.

Curtiss says therapy would probably be used in conjunction with chemotherapy and radiation therapy, once it gets to human trials. 

The study is published in this week’s issue of mBio, an American Society for Microbiology online-only, open access journal.

Bill Condie

Bill Condie

Bill Condie is a science journalist based in Adelaide, Australia.

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