Iron homeostasis and cell clonality drive cancer-associated intestinal DNA methylation drift in aging

Epigenetic drift is a key feature of aging and is associated with age-related diseases including cancer, yet the underlying molecular mechanisms remain unclear. Here, by analyzing DNA methylation and gene expression data from healthy and cancerous human colon samples, we identify an aging and colon cancer-associated DNA methylation (DNAm) drift. We find evidence that this drift is conserved in the mouse intestinal epithelium, where we demonstrate its origin within intestinal stem cells and identify its cell-intrinsic and non-mitotic characteristics, finding that its expansion is regulated via crypt clonality and fission. Mechanistically, we find that this drift is driven by age-related inflammation and reduced Wnt signaling, which dysregulate iron metabolism and impair TET activity. Despite CpG-level heterogeneity, we find that DNAm changes are consistent at the gene level, suggesting potential functionality. Our findings shed light on the epigenetic mechanisms of aging and provide a mechanistic basis for the hypermethylation observed in cancer.