Studies have demonstrated that environmental, host genetic, and socioeconomic factors influence the breast cancer prevalence landscape with a far-reaching influence on racial disparity to subtypes of breast cancer. To understand whether breast tissue harbors race-specific microbiota, we performed 16S rRNA gene-based sequencing of retrospective tumor and matched normal tissue adjacent to tumor (NAT) samples collected from Black non-Hispanic (BNH) and White non-Hispanic (WNH) women. Analysis of Triple Negative Breast cancer (TNBC) and Triple Positive Breast Cancer (TPBC) tissues for microbiota composition revealed significant differences in relative abundance of specific taxa at both phylum and genus levels between WNH and BNH women cohorts. Our main findings are that microbial diversity as measured by Shannon index was significantly lower in BNH TNBC tumor tissue as compared to matched NAT zone. In contrast, the WNH cohort had an inverse pattern for the Shannon index, when TNBC tumor tissue was compared to the matched NAT. Unweighted Principle Coordinates Analysis (PCoA) revealed a distinct clustering of tumor and NAT microbiota in both BNH and WNH cohorts.

Social epigenomics has emerged as an integrative field of research focused on identification of socio-environmental factors, their influence on human biology through epigenomic modifications, and how they contribute to current health disparities. Several health disparities studies have been published using genetic-based approaches; however, increasing accessibility and affordability of molecular technologies have allowed for an in-depth investigation of the influence of external factors on epigenetic modifications (e.g., DNA methylation, micro-RNA expression). Currently, research is focused on epigenetic changes in response to environment, as well as targeted epigenetic therapies and environmental/social strategies for potentially minimizing certain health disparities. Here, we will review recent findings in this field pertaining to conditions and diseases over life span encompassing prenatal to adult stages.

African American women are approximately twice as likely to be diagnosed with highly aggressive estrogen receptor-negative (ER-) and TNBC subtypes of breast cancer than Caucasian women. Among biologic factors, microbiota has been implicated in the etiology of several kinds of cancer including breast cancer. Few recent studies have shown that the breast niche-specific microbiota may have a major influence on breast tumorigenesis as shown by a decreased abundance of bacterial species with known immunomodulatory and probiotic effect in paired tumor tissue as compared to normal tissue derived from healthy patients, including different microbiota profiles in different subtypes of breast cancer. To understand whether the breast tissue harbors microbiota profiles that are uniquely race-specific we have analyzed tumor and matched normal and tumor tissue using 16S rRNA targeted sequencing strategy. Two distinct breast tumor types derived from women were included in this study: triple-negative breast cancer (TNBC) and triple-positive breast cancer (TPBC) derived from BNH and WNH women. The data were analyzed for microbiota composition, abundance, and diversity parameters, alpha diversity and beta diversity. The preliminary microbiome analysis revealed specific differences in abundance both at the phylum and genus levels between WNH and BNH women breast tissues; the alpha diversity matric, Shannon index measuring both richness and evenness of microbiota diversity showed differences in microbial diversity between normal breast tumor tissue and the matched normal adjacent to tumor tissue. The microbiota richness was relatively lower in BNH TNBC tumor tissue as compared to its matched normal adjacent to tumor zone as defined by pathologic analysis. In contrast, the microbiota richness was higher in WNH TNBC tumor tissue as compared to its matched normal breast tissue. The multivariate analysis of beta diversity revealed a distinct clustering in BNH and WNH TNBC microbiota between both tumors as compared to normal tissue and BNH as compared to WNH racial groups. Research reported in this publication was supported by the National Institute on Minority Health and Health Disparities of the National Institutes of Health under Award Numbers S21MD012472 and U54MD006882. Note: This abstract was not presented at the conference. Citation Format: Srikantha Thyagarajan, Yan Zhang, Santosh Thapa, Michael S. Allen, Nicole Phillips, Jamboor K. Vishwanatha. Comparative analysis of breast tumor microbiome in Black non-Hispanic (BNH) and White non-Hispanic (WNH) women [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 B26.

Studies have demonstrated that environmental, host genetic, and socioeconomic factors influence the breast cancer prevalence landscape with a far-reaching influence on racial disparity to subtypes of breast cancer. To understand whether breast tissue harbors race-specific microbiota, we performed 16S rRNA gene-based sequencing of retrospective tumor and matched normal tissue adjacent to tumor (NAT) samples collected from Black non-Hispanic (BNH) and White non-Hispanic (WNH) women. Analysis of Triple Negative Breast cancer (TNBC) and Triple Positive Breast Cancer (TPBC) tissue for microbiota composition revealed significant differences in relative abundance of specific taxa at both phylum and genus levels between WNH and BNH women cohorts. Our main findings are that microbial diversity as measured by Shannon index was significantly lower in BNH TNBC tumor tissue as compared to matched NAT zone. In contrast, the WNH cohort had an inverse pattern for the Shannon index, when TNBC tumor tissue was compared to the matched NAT. Unweighted Principle Coordinate Analysis (PCoA) revealed a distinct clustering of tumor and NAT microbiota in both BNH and WNH cohorts. Citation Format: Jamboor K. Vishwanatha, Srikantha Thyagarajan, Michael Allen, Yan Zhang, Nicole Phillips, Pankaj Chaudhary. Comparative analysis of breast tumor microbiome in Black non-Hispanic (BNH) and White non-Hispanic (WNH) women [abstract]. In: Proceedings of the AACR Virtual Conference: Thirteenth AACR Conference on the Science of Cancer Health Disparities in Racial/Ethnic Minorities and the Medically Underserved; 2020 Oct 2-4. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2020;29(12 Suppl):Abstract nr PO-095.