Commonly occurring gut bacteria can clean up chemo toxins in the body, research discovers.
In the human gut, useful bacteria make excellent neighbors.
A recent Northwestern University study discovered that particular varieties of gut bacteria can defend other useful bacteria from cancer cures — less harmful, drug-induced variations to the gut microbiome. By metabolizing chemotherapy drugs, the shielding bacteria could temper long- and short-term side effects of medication.
Eventually, the study could conceivably lead to new probiotics, engineered therapeutics, or dietary supplements to help boost cancer patients’ gut strength. Because chemotherapy-related microbiome shifts in children are associated with health complications later in life — including asthma, obesity, and diabetes — creating new plans for guarding the gut is particularly valuable for pediatric cancer patients.
“We were excited by bioremediation, which utilizes microbes to clean up contaminated environments,” said Northwestern’s Erica Hartmann, the research’s senior author. “Normally bioremediation applied to soil or groundwater but, here, we have implemented it to the gut. We know that particular bacteria can break down toxic cancer treatments. We wondered if, by breaking down drugs, these bacteria could defend the microbes around them. Our research reveals the answer is ‘yes.’ If some bacteria can break down toxins quick enough, that gives a protective outcome for the microbial community.”
The research will be issued today (May 26, 2021) in the journal mSphere.
Ryan Blaustein, a former postdoctoral associate in Hartmann’s laboratory, is the paper’s first author. He is now a postdoctoral fellow at the National Institutes of Health. Assistant professor Hartmann teaches environmental biology at Northwestern’s McCormick School of Engineering.
Although cancer therapies are life-saving, they also produce extremely painful and harsh side effects, including gastrointestinal problems. Chemotherapies, in particular, can exterminate the healthy, “useful” bacteria in the human gut.
“Chemotherapy medications do not distinguish between eliminating cancer cells and eliminating microbes,” Hartmann said. “Microbes in your gut help to digest your food and keep you fit. Killing these microbes is very harmful to kids as there’s some indication that disturbance in the gut microbiome early in life can lead to possible health conditions later in life.”
Working with Dr. Patrick Seed, a professor of pediatrics and microbiology-immunology at the Northwestern University Feinberg School of Medicine, Hartmann’s lab learned from Raoultella planticola. Normally occurring in the human gut in low abundances, Raoultella planticola can break down chemotherapy medicine doxorubicin, which has been shown in another study.
To examine whether or not this breakdown effect could defend the entire microbiome, the group developed simplified microbial communities, which covered several types of bacteria typically observed in the human gut. The “mock gut communities” carried bacteria strains (Klebsiella pneumoniae and Escherichia coli) that are good at breaking down doxorubicin, strains (Lactobacillus rhamnosus and Clostridium innocuum) that are particularly sensitive to doxorubicin, and one strain (Enterococcus faecium) that is opposing to doxorubicin but does not break it down.
The group then exposed these mock gut communities” to doxorubicin and observed increased survival among sensitive strains. The study concluded that, by degrading doxorubicin, several bacteria made the medicines less toxic to the rest of the gut.
Although the study highlights a promising innovative pathway for potentially protecting cancer patients, Hartmann warns that altering the new findings into treatments is still far off.
“There are numerous eventual applications that would be exceptional to help cancer patients — especially pediatric patients — not experience such harsh side effects,” she said. “But we’re still far from making that a certainty.”
Journal Reference: 26 May 2021, mSphere.