Racial differences in tumor-associated microbes in early colorectal carcinogenesis.

African Americans (AA) have a higher incidence of colorectal cancer (CRC) than Caucasian Americans (CA). Emerging evidence indicates that pathogenic tumor-associated microbes (TAMs) within preinvasive lesions may promote carcinogenesis. Since AAs are more prone than CAs to robust inflammatory responses to bacteria and fungi, especially at younger ages, infiltrates in early neoplasms may differ by race and age. To study this issue, we selected a convenience sample of 35 preinvasive cases diagnosed between October 2013 and October 2016 at the Medical University of South Carolina for microbial analysis. The study pathologist diagnosed the degree of dysplasia and predominant histology for each lesion. We extracted DNA from 10-micron-thick FFPE sections and sequenced 16S rRNA gene amplicons to determine the microbial communities. We normalized the data using central log ratio transformation with pseudo-counts and selected 20 microbes previously associated with CRC for analysis. Linear regression was used to assess associations between TAMs and race while adjusting for age and sex. We also examined these associations by colorectal location (distal, proximal), degree of dysplasia (high, not high), and age ( Citation Format: Kristin Wallace, David N. Lewin, Christine Bookhout, Shaoli Sun, Brianna Bronsky, Chentha Vasu, Brenda J. Hoffman, John A. Baron, Alexander V. Alekseyenko. Racial differences in tumor-associated microbes in early colorectal carcinogenesis [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 B33.