Salmonella is known to cause typhoid, severe food poisoning and other stomach-related maladies. What most people do not know is that certain strains, of this otherwise hostile microbe, have been found to exhibit impressive cancer-killing capabilities. Up until now, scientists have been unable to exploit the bacteria’s medicinal uses, without inducing any unpleasant side effects. However, a new study shows that researchers have finally managed to develop genetically-modified Salmonella, that effectively attacks the tumor, sans the nasty tummy problems.
The research, recently published in the American Society for Microbiology’s journal mBio, is part of a collaboration between Arizona State University and Germany-based Helmholtz Center for Infection Research. Certain strains of the bacteria, especially Salmonella enterica Serovar Typhimurium, have been known to possess remarkable anti-cancer properties. According to the scientists, these microorganisms are extremely efficient in colonizing a tumor and then, systematically eliminating the cancerous cells. In order to make it safer for humans, the team modified a part of the microbe’s outer membrane, known as lipopolysaccharide (LPS).
Known for its toxicity, the LPS is responsible for inducing sepsis, i.e. whole-body inflammation leading to organ failure and even death, in the host body. With the help of genetic engineering, the scientists were able to eliminate the specific genes involved in the synthesis of the lipopolysaccharide structure. Following this, the team performed laboratory testing, in human cancer cells and tumor-afflicted mice, to assess the efficacy of the mutant bacteria in killing cancer cells. Of the several Salmonella strains tested as part of the research, one in particular was found to be adept at shrinking the tumorous mass, without inducing any unpleasant side effects.
In order to enhance the cancer-killing abilities of the mutant strain, the researchers genetically-altered the bacteria, a second time, to include inducible arabinose promoter. Consequently, when injected into the affected mouse, the modified Salmonella would turn toxic only after entering the tumor, thus leaving the surrounding healthy cells unharmed. This is because, the microbe divides and multiples very slowly, only about once or twice 24 hours, in normal cells, as opposed to the cancer cells where it grows hourly. Dr. Roy Curtiss, a member of the research team and a professor of Microbiology at the ASU, said:
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. This transition from a benign, invasive Salmonella that doesn’t hurt normal cells to the toxic type occurs very rapidly (time wise) in the tumor due to the very rapid growth and cell division that occurs when Salmonella enters a tumor.
Upon successful completion of human trials, the treatment would likely be used alongside chemotherapy and radiation therapy.