Abstract B31: Microbiota composition in bilateral healthy breast tissue and breast tumors

Purpose: The purpose of this pilot study was to assess the differences in breast tissue microbiota composition by breast side (left versus right) within an individual woman and compare the microbiota of healthy and breast tumor tissue between women. We further aimed to determine whether certain bacterial taxa may be associated with breast tumors. Methods: Bilateral healthy breast tissue samples (n=36) were collected from ten women who received routine mammoplasty procedures at the University of Florida Department of Surgery. Archived breast tumor samples (n=10) were obtained from an established biorepository. Bacterial DNA was extracted from tissues, amplified via polymerase chain reaction (PCR), and sequenced on the Illumina MiSeq platform. Microbiota data were analyzed using QIIME and RStudio. Results: The most abundant phyla in both tumor and healthy tissues were Bacteroidetes, Firmicutes, Proteobacteria, and Actinobacteria. A total of 38 operational taxonomic units (OTUs) were found to be significantly different in terms of differential abundance between tumor and healthy tissues (absolute effect size range: 0.761-3.98). The OTUs with the largest absolute effect size associated with higher relative abundance in breast tumors were of Flavobacterium species (R2=3.98), Acinetobacter species (R2=3.64), [Mogibacteriaceae] family (R2=3.34), and Clostridiales order (R2=3.21). Alpha diversity (Shannon Diversity Index) was similar in healthy and tumor tissue (4.98 vs. 4.84; p=0.350). Based on unweighted UniFrac measures, breast tumor samples clustered distinctly from healthy samples (R2=0.10; p=0.001). Microbiota composition in healthy samples clustered within women (R2=0.20; p=0.012) and by breast side (left or right) within a woman (R2=0.36; p=0.001). Conclusion: We identified significant differences in microbiota composition between women and between breasts of the same woman. These results warrant further investigation to elucidate the potential relationship between breast tissue microbiota and breast cancer. Citation Format: Emily M. Klann, Jessica M. Williamson, Massimiliano S. Tagliamonte, Maria Ukhanova, Jaya Ruth Asirvatham, Harvey Chim, Lusine Yaghjyan, Volker Mai. Microbiota composition in bilateral healthy breast tissue and breast tumors [abstract]. In: Proceedings of the AACR Special Conference on the Microbiome, Viruses, and Cancer; 2020 Feb 21-24; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2020;80(8 Suppl):Abstract nr B31.