Oncological relevance of gut and urine microbiomes

Abstract

Dysfunction of the immune system plays a crucial role in the development and progression of cancer as well as the effectiveness of antitumor therapies. Gut microbiota, due to their impact on the immune system, are able to influence response to anticancer drug therapies. Next-generation DNA-sequencing technologies enabled a comprehensive quantitative and qualitative exploration of the gut microbiome. An increasing body of evidence indicates the association between the efficacy of immune checkpoint inhibitor therapies and gut microbiome composition in colorectal cancer, malignant melanoma, renal cell carcinoma, and non-small cell lung cancer. Recently, several bacterial strains and species were shown to be associated with treatment efficacies. In accordance, dysbiosis caused by antibiotic treatment was found to increase the risk of failure to immune checkpoint inhibitor therapies. In the light of these results, examination of microbiome composition may become an important factor for the prediction of immunotherapies. Currently ongoing clinical trials are investigating the potential of therapeutic alteration of microbiome composition. Contrary to the previous view, urine has been shown not to be sterile. By using sensitive DNA-sequencing technologies, several urinary bacteria could be identified which may contribute to the development and progression of bladder cancer and may influence the efficacy of intravesical BCG therapy. In the present work, we summarize recent studies that identified the presence of certain bacteria associated with the development, progression, and therapy resistance of various cancers.