Abstract
The incidence rate of colorectal cancer in younger adults has been rising in developed countries. This trend may be attributed to environmental exposures as a result of lifestyle changes. Many of the lifestyle factors that promote colorectal cancer can also affect the gut microbiome, which may be associated with colorectal cancer risks. The role of the microbiome in the ongoing rise of early-onset colorectal cancer is unknown. Here, we aimed to investigate age-related differences in the gut microbiome of patients with colorectal cancer and healthy individuals by examining both the fecal and tumor microbiomes. We utilized the publicly accessible data on fecal shotgun metagenomics from CuratedMetagenomeData and TCGA via the GDC Data Portal. Comparison of 701 colorectal cancer and 693 controls revealed that microbial features were age dependent, with a significant difference in species enrichment between early-onset (<50 years) and late-onset (>65 years) patients with colorectal cancer. Analysis of the tumor-associated microbiome in a separate dataset of 85 patients with colorectal cancer verified age-specific differences in taxon abundance between early- and late-onset patients with colorectal cancer. Finally, using host gene expression data, we found a stronger microbe-host interaction in early- vs. late-onset colorectal cancers. Altogether, these findings indicate that microbial features were age-dependent with stronger microbial-host interactions at the tumor site in early-onset colorectal cancers, suggesting a direct role of microbes in tumorigenesis via interaction with cancer-related pathways in this age group. PREVENTION RELEVANCE: Early-onset colorectal cancer is on the rise, presumably because of changes in environmental exposures. Lifestyle changes may contribute to colorectal cancer via alterations in gut microbes. Here, we show that microbial association with colorectal cancer is age-dependent, and microbe interactions with tumor pathways are stronger in young versus older colorectal cancers.