Applied and Environmental Microbiology
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In the United States, 1 in 8 women will be diagnosed with breast cancer in her lifetime. Along with genetics, the environmentcontributes to disease development, but what these exact environmental factors are remains unknown. We have previouslyshown that breast tissue is not sterile but contains a diverse population of bacteria. We thus believe that the host's local microbiomecould be modulating the risk of breast cancer development. Using 16S rRNA amplicon sequencing, we show that bacterialprofiles differ between normal adjacent tissue from women with breast cancer and tissue from healthy controls. Women withbreast cancer had higher relative abundances of Bacillus, Enterobacteriaceae and Staphylococcus. Escherichia coli (a member ofthe Enterobacteriaceae family) and Staphylococcus epidermidis, isolated from breast cancer patients, were shown to induce DNAdouble-stranded breaks in HeLa cells using the histone-2AX (H2AX) phosphorylation (γ-H2AX) assay. We also found that microbialprofiles are similar between normal adjacent tissue and tissue sampled directly from the tumor. This study raises importantquestions as to what role the breast microbiome plays in disease development or progression and how we can manipulatethis for possible therapeutics or prevention.