Gut Bacteria Could Make Skin Cancer Drugs More Effective


A new study suggests healthy gut bacteria can help cancer-fighting drugs do just that — fight cancer.  

Researchers at the University of Texas found that people who had diverse gut bacteria were more likely to benefit from immunotherapy, a treatment used to fight cancer.

Immunotherapy, also known as biological therapy, treats cancer by boosting the body’s natural defenses. Essentially, it launches the immune system into full speed and then cuts the breaks.

The evolution of a 4mm Nodular Melanoma over the course of 14 months. Image courtesy: NodularMelanomaEvolution, CC BY-SA 3.0
The evolution of a 4mm Nodular Melanoma over the course of 14 months. Credit: NodularMelanomaEvolution/Wikimedia Commons, CC BY-SA 3.0

The study examined the gut bacteria from 23 cancer patients who responded to therapy and 11 who did not. All of the patients examined had advanced melanoma.

“We found a night-and-day difference in the diversity of bacteria species in the faecal samples,” Dr. Jennifer Wargo, a melanoma surgeon and scientist at the University of Texas, told the BBC News online.

The study, which was presented at the National Cancer Research Institute’s Cancer Conference in Liverpool, found that the patients who responded to the therapy had higher levels of Ruminococcus bacteria than those who did not respond to treatment. Researchers believe this new discovery suggests that changing the balance of bacteria in the gut could help boost the effectiveness of immunotherapy.

“It is hugely plausible I think – we still need to dig a little deeper, but I think we’re onto something,” Dr. Wargo said. “I think it really does shape our body’s immune response as a whole and to cancer.”

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Early studies found that changing the gut bacteria in mice improved their response to immunotherapy, but this was the first study that looked at the link in humans.

“Our research shows a really interesting link that may mean the immune system is aided by gut bacteria when responding to drugs,” Dr. Wargo said in a press release. “Not all patients respond to immunotherapy drugs and it’s hard to know who will benefit from the treatment prior to it being given.”

There has yet to be a definitive link between gut bacteria and a positive response to immunotherapy in humans, but the results are encouraging. People who eat fruits and vegetables tend to have better gut bacteria, so a healthy lifestyle could actually be what improves immunotherapy effectiveness.

“It might point to a healthy diet increasing your chances, which I think would be a great message,” Dr. Wargo said.

This is not the first time gut bacteria has helped fight cancer. A 2013 study published in the journal Science found that intestinal flora, also known as microbiota, helped chemotherapy to be more effective.

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“Gut microbes have been shown to influence the role of conventional chemotherapy, so it’s probably not surprising that they impact on response to new immunotherapies being used in the the clinic,” Dr. Pippa Corrie, Chair of the NCRI’s Skin Cancer Clinical Studies Group, said. “Manipulating the gut flora may be a new strategy to enhance activity of immunotherapy drugs, as well to manage problematic toxicity in the future.”

Clinical trials still need to be conducted, but researchers suggest giving patients antibiotics, probiotics, or even a fecal transplant before immunotherapy could increase the likelihood of the cancer-fighting therapy to be effective.

Danielle Tarasiuk

Danielle Tarasiuk is a multimedia journalist based in Los Angeles. Her work has been published on, Yahoo! Sports, KCET, and NPR-affiliate stations KPCC and KCRW. She’s a proud Sarah Lawrence College and USC Annenberg alumn.