The fight against cancer has recruited some unlikely allies. From honeybee venom to close virus cousins of the HIV pathogen, converting microbes and toxins from the dark side to delivering drugs is proving to be one of the most powerful weapons in stopping cancer.
One particular challenge is how tumors can suppress the immune system, preventing it from identifying and destroying the rapidly dividing cells.
Now, new research has used a weakened strain of Salmonella (yes, the same bacteria that prevents you from eating chicken rare) to gather around tumors and signal the immune system of the growing threat. When the researchers tried it on mice, there was a heightened immune response against the tumor and extended the survival of multiple tumor models of mice.
The results were published in Nature Biomedical Engineering.
Salmonella typhimurium has previously been demonstrated to be safe and effective as a delivery method for treatments, and Jinhui Wu and colleagues from Nanjing University in China looked to expand on this by using it as a vehicle to deliver signaling antigens directly to the tumor.
It is a great organism for this use for two reasons: it has self-propelling flagella (the small tails that propel some bacteria forward), moving much quicker than other bacterial species; and Salmonella can increase the immune response towards cancer antigens.
The tests were conducted on mice after receiving radiotherapy. Each Salmonella bacterium was coated in positively charged nanoparticles that aimed to stick to negatively charged antigens released by the tumor as a result of radiation. This would mean tumor antigens, which the immune system could recognize, were then bundled together and nicely packaged outside of the tumor, ready for dendritic cells to notice and take action.
In mice treated with the bacteria therapy, 83 percent survived, while just 25 percent of the placebo control group survived. The treatment also resulted in higher dendritic cell activity in vitro, and higher crosstalk between tumor antigens and immune system cells.
The results suggest the bacteria therapy is safe and effective in mouse models, and a similar delivery method could be a promising avenue to combat immunosuppressive cancers.
While the research was successful, it remains limited to mouse models, and tumor interactions in mice are often different from those in humans.
In a statement to the Scientist, Wu said that the team has plans to take the treatment to humans, but must do significantly more safety testing before doing so.