A microfluidic co-culture model for investigating colonocytes-microbiota interactions in colorectal cancer.

Changes in the abundance of certain bacterial species within the colorectal microbiota correlate with colorectal cancer (CRC) development. While carcinogenic mechanisms of single pathogenic bacteria have been characterized in vitro , limited tools are available to investigate interactions between pathogenic bacteria and both commensal microbiota and colonocytes in a physiologically relevant tumor microenvironment. To address this, we developed a microfluidic device that can be used to co-culture colonocyte spheroids and colorectal microbiota. The device was used to explore the effect of Fusobacterium nucleatum , an opportunistic pathogen associated with colorectal cancer development in humans, on colonocyte gene expression and microbiota composition. F. nucleatum altered the transcription of genes involved in cytokine production, epithelial-to-mesenchymal transition, and proliferation in colonocytes in a contact-independent manner; however, most of these effects were significantly diminished by the presence of commensal microbiota. Interestingly, F. nucleatum significantly altered the abundance of multiple bacterial clades associated with mucosal immune responses and cancer development in the colon. Our results highlight the importance of evaluating the potential carcinogenic activity of pathogens in the context of a commensal microbiota, and the potential to discover novel inter-species microbial interactions in the CRC microenvironment.