RT Journal Article SR Electronic T1 Exploring the emerging role of the microbiome in cancer immunotherapy JF Journal for ImmunoTherapy of Cancer JO J Immunother Cancer FD BMJ Publishing Group Ltd SP 108 DO 10.1186/s40425-019-0574-4 VO 7 IS 1 A1 Fessler, Jessica A1 Matson, Vyara A1 Gajewski, Thomas F. YR 2019 UL http://jitc.bmj.com/content/7/1/108.abstract AB The activity of the commensal microbiota significantly impacts human health and has been linked to the development of many diseases, including cancer. Gnotobiotic animal models have shown that the microbiota has many effects on host physiology, including on the development and regulation of immune responses. More recently, evidence has indicated that the microbiota can more specifically influence the outcome of cancer immunotherapy. Therapeutic interventions to optimize microbiota composition to improve immunotherapy outcomes have shown promise in mouse studies. Ongoing endeavors are translating these pre-clinical findings to early stage clinical testing. In this review we summarize 1) basic methodologies and considerations for studies of host-microbiota interactions; 2) experimental evidence towards a causal link between gut microbiota composition and immunotherapeutic efficacy; 3) possible mechanisms governing the microbiota-mediated impact on immunotherapy efficacy. Moving forward, there is need for a deeper understanding of the underlying biological mechanisms that link specific bacterial strains to host immunity. Integrating microbiome effects with other tumor and host factors regulating immunotherapy responsiveness versus resistance could facilitate optimization of therapeutic outcomes.Jessica Fessler and Vyara Matson contributed equally to this work.Abbreviations:Allo-HSCTAllogeneic hematopoietic stem cell transplantationAPCsAntigen-presenting cellsCTLCytotoxic T lymphocyteCTLA-4Cytotoxic T-lymphocyte-associated protein 4DCDendritic cellGFGerm-freeGVHDGraft-versus-host diseaseICBImmune checkpoint blockadeLPLamina propriaMALDI-TOFMatrix-assisted laser desorption ionization time-of-flightMAMPMicrobe-associated molecular patternMDSCMyeloid-derived suppressor cellMLNMesenteric lymph nodesOSOverall survivalOTUOperational taxonomic unitPD-1Programmed cell death protein 1PD-L1Programmed death-ligand 1PAMPPathogen-associated molecular patternPFSProgression-free survivalPRRPattern recognition receptorPSAPolysaccharide ASCFAShort-chain fatty acidsSFBSegmented filamentous bacteriaSPFSpecific pathogen-freeTdLNTumor-draining lymph nodeTMETumor microenvironment