The world is filled with microorganisms, which have a profound impact on many facets of life. Do these microbial communities influence cancer1? Many studies of microbes and their genomes (collectively called the microbiome) have focused on the gut, where most of the body’s microbes reside. This work has revealed a role for the gut microbiome in several types of cancer that arise in the intestinal lining itself2–4, and indicated that the gut microbiome might influence cancers at distant sites through its impact on the immune system1. In addition, emerging evidence indicates that microbial signatures (such as nucleic acids) can be found in tumours at other sites in the body5,6 and in the tissues and blood of individuals who don’t have cancer7,8. Writing in Nature, Poore et al.9 build on this evidence, identifying signatures of microbial DNA and RNA, both in tumours and in the blood, across multiple human cancers. The authors further suggest that these signatures might augment existing clinical diagnostic tools, although further work is needed in this area…..
