Study finds good gut bacteria improves cancer patient's response to immunotherapy

Washington: In a recent study, a group of researchers found a link between an individual's gut bacteria and their response to anticancer immune checkpoint inhibitor therapy (ICT).

The researchers analyzed the gut bacteria of 39 melanoma patients who were treated with immunotherapies and found a strong association between a good response and the presence of particular bacteria. While talking about the research, senior author Dr. Andrew Koh, Associate Professor of Pediatrics and Microbiology with the Simmons Cancer Center, said, "Our research suggests there were certain good-guy bacteria that are needed to optimize the effectiveness of checkpoint inhibitors.

These bacteria somehow prime your immune system so that it's better able to attack cancer cells and kill them." Although ICT achieves durable remission in up to 50 percent of patients with metastatic melanoma, a significant proportion of patients fail to respond or experience severe autoimmune adverse effects, the researchers note.

A person with metastatic melanoma volunteered for the study to identify the link. The participant's metastatic melanoma was discovered on his lungs while he was fighting pneumonia. He was treated with an every-other-week infusion of nivolumab, an immunotherapy drug that acts by lifting a brake on the immune system, allowing the body's natural defenses to go into overdrive.

Researchers found he had the beneficial gut bacteria and suspect this microbiome contributed to the outcome. As a group, patients who responded well to the immunotherapy had three specific bacteria:

- Bacteroides thetaiotaomicron

- Faecalibacterium prausnitzii

- Holdemania filiformis

After identifying the link, scientists looked for a potential reason for the association between the helper bacteria and immunotherapy effectiveness. Dr. Koh explained, "Is it something the bacteria are making? We examined metabolites in these subjects and found the strongest correlation between anacardic acid, present in cashews and mangoes, and the beneficial bacteria."

Now the researchers are planning to follow-up on the current study with larger clinical studies.

The study was published in journal Neoplasia.