Modeling early tumorigenesis and metastatic invasion with cell competition

Abstract

Many cancers arise in epithelial tissues, yet how mutant cells expand within otherwise healthy epithelia remains poorly understood, in part due to the difficulty of observing early tumorigenesis. To address this, we introduced oncogenic perturbations in Madin-Darby canine kidney (MDCK) cells and tracked their behavior in co-culture with wildtype cells. Overexpression of the oncogene cMyc or knockdown of the tumor suppressor Fat1 generated cells with deregulated homeostatic control that (i) achieved higher steady-state densities, (ii) resisted anchorage-dependent cell death (anoikis), resulting in multilayered tissue structures, and (iii) eliminated neighboring wildtype cells during co-culture. Wildtype and oncogenic populations coexisted when physically separated but exposed to shared, competition-conditioned media, indicating that super-competitive overgrowth is not driven primarily by diffusible factors. Consistent with this, conditioned media contained viable cells from both populations that adhered and proliferated upon replating, suggesting that live-cell extrusion contributes to competitive dynamics. During direct confrontation, wildtype cells underwent apoptosis several cell diameters away from the interface with oncogenic cells, arguing against a strictly contact-dependent, transmembrane signaling mechanism. Inhibition of apoptosis through ectopic Bcl2 expression rescued wildtype cell survival but led to multilayer accumulation, indicating that apoptosis functions as an execution step downstream of competition rather than its initiating cause. Extending these findings to a metastasis-like context, we found that super-competitor cells introduced in suspension invaded and overtook confluent wildtype monolayers, establishing a tractable assay for screening anti- invasive or anti-metastatic interventions. Finally, engineering cells resistant to membrane potential–mediated mechano-transduction abrogated Myc- and Fat1-driven super-competition in both two-dimensional co-culture and a three-dimensional invasion model. Together, these findings support a model in which Myc- and Fat1-driven super- competition is governed by mechanical interactions, rather than biochemical signaling alone, and suggest that mechanical cell competition—traditionally viewed as tumor-suppressive—may instead promote early tumor expansion and invasion.