Pathogenesis of Early Onset Colorectal Cancer: Microbiome Contributions and Mechanisms

ABSTRACT Early onset colorectal cancer (EO-CRC), defined as disease onset in individuals younger than 50 years, is an emerging, deadly public health threat in the United States. Because the colon contains a densely populated microbial ecosystem, it is hypothesized that the intimate association of colonic epithelial cells with the microbiota can contribute to the initiation and/or progression of human CRC. However, as yet, no studies investigating the microbiota/microbiome of patients with EO-CRC have been reported. Our group has identified that colon mucus- invasive bacterial biofilms are common on CRCs occurring in those older than 50 (termed late onset CRC, LO- CRC). We have demonstrated that LO-CRC-associated bacterial biofilms induce colon tumors in susceptible mouse models. Further, our preliminary data now support that biofilms are common on EO-CRC. Herein, we will test the hypothesis that individuals with EO-CRC display microbial and colonic epithelial signatures that differ from age-matched controls. In our distinct, but complementary, Specific Aims, we will trace the epidemiology of biofilm formation on CRCs for the past 35 years, test the antibody responses of EO-CRC patients and comparator disease and control groups to biofilm and other microbes and determine if microbial exposures induce changes in colon epithelial biology that lower the threshold for colon epithelial cell neoplastic transformation. Using retrospective and prospective human cohorts, our Specific Aims are: 1) to determine the longitudinal association of biofilm structure and composition with EO-CRC defined by all bacterial and multiprobe fluorescent in situ hybridization (FISH) and 16S rRNA amplicon sequencing; 2) to characterize the binding of serum antibodies of EO-CRC patients to a broad array of environmental organism-associated antigens (e.g., viral, phage, biofilm bacterial and/or bacterial toxin) via programmable phage display-based profiling (known as PhIP-Seq); and 3) to define the molecular signatures of normal EO-CRC epithelium with known biofilm status through genome-wide methylation studies and the environmental stress responses of normal human colonoids derived from EO-CRC, LO-CRC and healthy persons. Our results will provide insight into the microbial associations and colon epithelial cell mechanisms that we predict potentiate EO-CRC, with the ultimate goal of informing and accelerating novel strategies for EO-CRC detection, prevention and intervention.