Diet-gut microbial interactions influence cancer immunotherapy

Abstract

The gut microbiome is involved in the absorption and metabolism of host nutrients and modulates the immune response, affecting the efficacy of immunotherapy for cancer. In patients receiving immunotherapy, appropriate modifications of gut microbiota are thought to improve therapeutic response. Of all the factors that influence the gut microbiota, diet is the most influential and modifiable. Healthy dietary patterns as well as some specific dietary components can help the growth of beneficial microbiota in the gut, thereby protecting against cancers and promoting human health. A growing number of researches have confirmed the positive effects of a diet-gut microbiota approach as an adjuvant therapy for cancer, but controversy remains. Here, we summarize the interactions between diet and gut microbes based on previous studies, and discuss the role of gut microbiota-based dietary strategies in tumor immunotherapy, with the potential mechanisms of actions also intensively discussed.

Keywords: cancer; diet; gut microbiota; immunity; immunotherapy.

Figure 1

Dietary modulation of the gut microbiota. A healthy diet can maintain the balance of intestinal microecology, and is beneficial for the gut microbiota to exert positive effects on the host (neurological, structural, metabolic, protective). An unhealthy diet disrupts the balance of the host gut microecology and participates in the occurrence and development of many diseases, including neuropsychiatric disorders, metabolic diseases, digestive diseases, tumor, and others. ASDs, Autistic Spectrum Disorder; ADHD, Attention deficit and hyperactivity disorder; MS, Multiple Sclerosis; NMO, neuromyelitis optica; IBD, Inflammatory bowel disease, IBS, Irritable Bowel Syndrome; CHB, Chronic hepatitis B; NAFLD, Nonalcoholic fatty liver disease.

Figure 2

Dietary and gut microbial interactions regulate host immunity and metabolism. Different dietary patterns affect the composition of gut microbes and their metabolites, which are involved in the pathogenesis of many diseases by affecting host metabolism and immunity through different mechanisms. Also alterations in gut microbes in turn affect nutrition. Some tumor associated bacterascites (e.g. H. pylori, F. nucleatum and C. thrachomatis), promote tumorigenesis and progression. GLP1, glucagon-like peptide 1; PYY, peptide tyrosine-tyrosine; IPA, indolepropionic acid; MAMPs, Metabolism-Associated Molecular Patterns; TMAO, Trimetlylamine oxide.

Figure 3

Role of SCFAs in immune cells. SCFAs affect the activity, differentiation and function of immune cells (including T cells, B cells, NK cells, DCs, macrophages, neutrophils) through different mechanisms. SCFAs, short-chain fatty acids; GPCRs, G-protein-coupled receptors; HDACs, inhibit histone deacetylases; FFAR, free fatty acid receptor; ADCC, antibody dependent cell-mediated cytotoxicity; IL, interleukins; MCT1, monocarboxylate transporters 1; FASL, Fas Ligand; TRAIL, tumour necrosis factor-related apoptosis-inducing ligand; NK, natural killer cells; DC, dendritic cell; Aldh1a1, aldehyde dehydrogenases 1 family member a1; AID, activation-induced cytidine deaminase.