Dedifferentiation-driven oncogenic stemness promotes tumor-sustaining adaptability in the intestinal epithelium

Intestinal tumorigenesis can occur via two distinct routes: bottom-up tumorigenesis occurs from mutations sustained in the Lgr5⁺ stem cells, whereas top-down tumorigenesis is driven by dedifferentiation of epithelial cells near the intestinal lumen. While sporadic human colon adenomas exhibit features of top-down tumorigenesis, their biological determinants remain elusive. Here, using a Smad4 loss-of-function and β-catenin gain-of-function (Smad4^LOF:β-catenin^GOF) mouse model, we demonstrate that dedifferentiation-derived oncogenic stem cells sustain tumorigenesis more effectively than endogenous mutant stem cells harboring the mutation. The dedifferentiating villi epithelial cells showed early expression of CD44 and Lgr5, supporting oncogenic stemness. Aberrant Notch signaling in the villi epithelium was also detected at the onset of dedifferentiation, suggesting its contribution to dedifferentiation. Single-cell RNA sequencing revealed a distinct population of dedifferentiation-derived stem cells enriched for proliferative, metabolic, and mouse embryonic stem cell-like gene signatures, consistent with enhanced plasticity and tumorigenic potential. These mutant cells exhibited growth factor independence, indicating a capacity for niche-independent proliferation and metabolic adaptation to sustain tumor growth. These findings identify dedifferentiation-driven stemness, aberrant Notch activation, and metabolic plasticity as cooperative mechanisms that promote top-down intestinal tumorigenesis. This study provides insight into how oncogenic dedifferentiation contributes to tumor heterogeneity and persistence and has implications for therapeutic resistance in colorectal cancer.