Genetically Engineered Salmonella Shown to Kill Cancer Cells without Causing Harm

Washington (PNA/Xinhua) — Salmonella, the bacteria commonly known for causing food poisoning, may be genetically modified to kill cancer cells without causing harm to patients, researchers said Tuesday.

“There has long been interest in using genetically engineered microbes to target and destroy cells within solid tumors,” study author Roy Curtiss, professor at the Arizona State University, said in a statement.

“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.”

For years, researchers have known that certain strains of bacteria, including Salmonella enterica, can kill cancer cells.

However, in order to use Salmonella as a weapon against cancer in humans, researchers must find a balance between allowing it to kill the cancer and be safe for the patient.

In the new study, the researchers focused on modifying the lipopolysaccharide structure (LPS) of the Salmonella strain to make the bug less toxic.

The researchers used genetic engineering to delete genes involved in the synthesis of the LPS, and then tested various modified Salmonella strains to see how they performed in test tube studies with human cancer cells and in tumor bearing mice.

They identified a particular mutant strain that was the most effective at killing cancer cells and shrinking tumors, and also unable to cause disease, but this mutant strain was less able to colonize the tumors.

To address this problem, the researchers genetically-modified the strain once more, and this modification allowed it to be injected in the mouse in a form that would not harm normal, healthy cells, was effective at colonizing tumors, and after entering cancer cells, would turn toxic.

In a normal cell, Salmonella grows very slowly, dividing once or twice in a 24-hour period, but in a tumor, the bacteria divide every hour.

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

The findings were published in the U.S. journal mBio. (PNA/Xinhua) FFC/EBP