Abstract B25: Colorectal cancer-associated anaerobic bacteria proliferate in tumor spheroids and alter the microenvironment

Recent reports show that colorectal tumors contain microbiotas that are distinct from those that reside in a “normal” colon environment and that these microbiotas can contribute to cancer progression. Fusobacterium nucleatum is the most commonly observed species in the colorectal tumor microenvironment and reportedly influences disease progression through numerous mechanisms. However, a detailed understanding of the role of this organism in cancer progression is limited, in part due to challenges in maintaining F. nucleatum viability under standard aerobic cell culture conditions. Herein we describe the development of a 3-dimensional (3D) tumor spheroid model that can harbor and promote the growth of anaerobic bacteria. Bacteria-tumor cell interactions and metabolic crosstalk were extensively studied by measuring the kinetics of bacterial growth, cell morphology and lysis, cancer-related gene expression, and metabolomics. We observed that viable F. nucleatum assembles biofilm-like structures in the tumor spheroid microenvironment, whereas heat-killed F. nucleatum is internalized and sequestered in the cancer cells. Lastly, we use the model to coculture 28 Fusobacterium clinical isolates and demonstrate that the model successfully supports coculture with diverse fusobacterial species. This bacteria-spheroid coculture model enables mechanistic investigation of the role of anaerobic bacteria in the tumor microenvironment. Citation Format: Stephen H. Kasper, Carolina Morell-Perez, Thomas P. Wyche, Theodore R. Sana, Linda A. Lieberman, Erik C. Hett. Colorectal cancer-associated anaerobic bacteria proliferate in tumor spheroids and alter the microenvironment [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 B25.