Salmonella kills cancer cells
14 Apr 2015
Genetically engineered salmonella has been shown to kill cancer cells in laboratory tests, according to research.
To conduct the study, a research team at the American Society for Microbiology focused on modifying the lipopolysaccharide structure (LPS) of salmonella to make the bacteria less toxic, thereby rendering it safe enough to use as a potential anti-cancer therapy.
“There has long been interest in using genetically engineered microbes to target and destroy cells within solid tumours
Research leader Roy Curtiss
In battling salmonella’s toxicity, 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 tumour bearing mice.
Tests identified a ’mutant strain’ of salmonella as the most effective at killing cancer cells and shrinking tumours.
Unfortunately, the mutant strain was not as adept at colonising tumours as other strains, such as Serovar Typhimurium, have previously shown.
To address this issue, the researchers added a further genetic modification - an inducible arabinose promoter that allowed the salmonella to be injected in the mouse in a form that would not harm normal, healthy cells, was effective at colonising tumours, and after entering cancer cells, would turn toxic, the researchers said.
“This transition from a benign, invasive salmonella that doesn’t hurt normal cells to the toxic type occurs very rapidly (time-wise) in the tumour due to the very rapid growth and cell division that occurs when salmonella enters a tumour,” said Roy Curtiss, who helped conduct the research.
According to Curtiss, in a normal cell, salmonella grows very slowly, dividing once or twice in a 24-hour period, but in a tumour, the bacteria divide every hour.
Looking ahead, Curtiss suggests the investigational therapy could probably be used in conjunction with chemotherapy and radiation therapy, once it gets to human trials.
“There has long been interest in using genetically engineered microbes to target and destroy cells within solid tumours,” Curtiss said.
“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,” he said.
