Gut bugs found to aid in cancer fight

Recent intriguing evidence from several human clinical trials has suggested that the composition and diversity of the gut microbiome influences response to cancer immunotherapy.

To better understand whether diets could enhance patients’ responses to cancer therapies by manipulating the gut microbiota, researchers carried out a systematic review searching articles published on PubMed, Web of Science, Sciencedirect and Scopus.

One trial included in the review assessed outcomes of those on the Mediterranean diet. Results showed that participants increased levels of fecal short chain fatty acid (SCFAs), Prevotella, and some fiber-degrading Firmicutes.

An additional study investigating the consumption of whole grains for 6 weeks by healthy participants revealed those who consumed whole grains, but not refined grains, exhibited increased levels of plasma alkylresorcinols and stool weight and frequency, in addition to higher levels of stool acetate and SCFAs.

These changes associated with increased levels of Lachnospira, which produces SCFAs, and decreased levels of Enterobacteriaceae, which are pro-inflammatory.

One other study found that even short-term consumption of whole grains and/or brown rice yielded changes in the gut microbiota that aligned with improvements in individuals’ physiological measures.

A larger study that followed 123 overweight/obese individuals for 9 weeks who consumed a whole grain-based diet revealed participants exhibited “significantly reduced fecal levels of Enterobacteria and Desulfovibriona, which are endotoxin-producing pathogens. In contrast, levels of Bifidobacteria, which protect the gut barrier, increased,” authors wrote.

In addition, levels of lipopolysaccharide-binding protein, TNF-α, and IL-6 (a proinflammatory cytokine) decreased, suggesting that whole grain intake may ameliorate inflammatory responses.

Although several other trials showed consuming fruits, vegetables and whole grains did not alter participants’ gut microbiota, researchers noted that components of these food stuffs can suppress inflammation and improve gut health by modulating the immune system before changes in the gut microbiota become obvious.

Previous human studies also suggested gut microbiota composition at baseline may affect cancer immunotherapy responses.

In a trial of 112 individuals with melanoma treated with anti-programmed cell death 1 protein (PD1) immunotherapy, those who responded to treatment had increased diversity and their systemic and antitumour immunity was enhanced, according to authors.

Several additional clinical trials are ongoing in which researchers are manipulating the gut microbiota via lifestyle changes or probiotics, or faecal transplantation in an effort to improve responses to cancer therapy.

Most trials already completed focused on patients with melanoma and revealed how baseline gut microbiota composition impacted responses to immunotherapy. According to researchers, “these approaches warrant testing in non-small-cell lung cancer and renal cell carcinoma patients.”