Many factors within the host environment may play a role in modulating an immune response. Outside of the tumor microenvironment, factors such as smoking, diet, UV exposure, infectious agents, and the gut microbiome can favorably or unfavorably affect the antitumor immune response.1-3
The gut microbiome is a collection of bacteria and other organisms that actively colonize the intestine.4 Certain bacterial species have been identified that can influence cancer incidence, progression, and response to therapy.4
Factors within the host environment, including the gut microbiome, are currently being investigated as I-O biomarkers.
REFERENCES: Host Environment
1. Chen DS, Mellman I. Elements of cancer immunity and the cancer-immune set point. Nature. 2017;541(7637):
321-330. 2. Alexandrov LB, Nik-Zainal S, Wedge DC, et al. Signatures of mutational processes in human cancer. Nature. 2013;500(7463):415-421. 3. Sharma P, Allison JP. The future of immune checkpoint therapy. Science. 2015;348(6230):56-61. 4. Zitvogel L, Galluzzi L, Viaud S, et al. Cancer and the gut microbiota: an unexpected link. Sci Transl Med. 2015. doi:10.1126/scitranslmed.3010473.