As the CosmosID blog illustrates regularly, microbes are remarkable for their ability to shape and affect just about every aspect of the world we live in. Yet, each week we are newly awed by publications that highlight discoveries of microbial feats and applications. This week was no different, as we were captivated by a story about a researcher who aims to cure cancer using Salmonella. The idea of treating cancer with bacteria is not new. In fact, research on this particular topic dates back to at least the 1890s. However, up until now, research efforts have been inhibited by the toxicity of Salmonella.
The person behind this more recent effort is the research director for the Cancer Research Center in Columbia, Missouri, Abe Eisenstark, who has a background in Salmonella research. It was this experience that drove him to direct Alison Dino, a scientist at the University of Missouri, to start experimenting with using old Salmonella samples as weapons against cancer. Entertaining this wild notion, Dino began by putting these bacterial samples into the same petri dishes occupied by tumor cells. As she combined the two biological warriors for a showdown, she wanted to see if the Salmonella would be drawn to the tumor cells, and if the bacteria would also leave healthy cells alone. A win would mean the bacteria attacked the cancer cells while leaving the healthy cells unharmed. To her amazement, she found a promising candidate in a strain labeled CRC 1674.
It helps to first understand that research had already shown that Salmonella is drawn to tumor cells. But the novel idea behind this research story is Dr. Eisenstark’s insight to use aged Salmonella. He predicted that the bacteria samples, having survived in isolated vials for decades, would have adapted to low energy environments by inhibiting their own toxicity, as that characteristic demands energy that the bacteria could not have spared.
When placed in a petri dish with cancerous tissue, the scientists found that the bacteria moved straight to the tumor cells but showed no attraction to healthy cells. Working from this validation, the Mizzou researchers have since genetically altered the CRC 1674 strain to make it even less toxic and more troublesome to cancer cells. As a publication from 2016 shows, this altered strain was able to target prostate cancer tumors in mice and even shrink the tumors but could not stop their spread. The team is continuing to work on modifying the promising strain, and is looking to begin clinical trials in larger animals as early as 2018.
As with the greater story of oncology efforts, this research has great promise but also much progress to be made. Regardless, it’s worth marveling at the ingenuity required to successfully modify one of the world’s most common food-borne diseases to target cancer.