Wnt activation disturbs cell competition and causes diffuse invasion of transformed cells through NF-B-MMP21 pathway

Normal epithelial cells exert their competitive advantage over RasV12-transformed cells and eliminate them into the apical lumen via cell competition. However, the internal or external factors that compromise cell competition and provoke carcinogenesis remain elusive. In this study, we examine the effect of sequential accumulation of gene mutations, mimicking multi-sequential carcinogenesis on RasV12-induced cell competition in intestinal epithelial tissues. Consequently, we find that the directionality of RasV12-cell extrusion in Wnt-activated epithelia is reversed, and transformed cells are delaminated into the basal lamina via non-cell autonomous MMP21 upregulation. Subsequently, diffusively infiltrating, transformed cells develop into highly invasive carcinomas. The elevated production of MMP21 is elicited partly through NF-kappa B signaling, blockage of which restores apical elimination of RasV12 cells. We further demonstrate that the NF-kappa B-MMP21 axis is significantly bolstered in early colorectal carcinoma in humans. Collectively, this study shows that cells with high mutational burdens exploit cell competition for their benefit by behaving as unfit cells, endowing them with an invasion advantage. The relevance of cell competition in intestinal epithelial carcinogenesis remains to be explored. Here, the authors find aberrant Wnt activation in RasV12-transformed cells reverses the directionality of cell extrusion mediated by cell competition in intestinal epithelium, causing infiltration into basal lamina rather than apical elimination of transformed cells and consequent development of invasive carcinomas.