Mirror Worlds: The Shared Regulatory Architecture of Cell Fate in Development and Cancer.

Lineage plasticity has emerged as a central mechanism through which cancer cells adapt to therapeutic pressure, evade immune surveillance, and acquire aggressive phenotypes. Although recognized across tumor types, the regulatory principles governing how cancer cells reprogram cellular identity remain incompletely understood. In this review, we propose that lineage plasticity in cancer reflects the redeployment of regulatory frameworks established during normal development. Rather than representing a stochastic byproduct of genomic instability, cancer plasticity frequently unfolds within gene regulatory architectures that also govern cell fate specification, lineage commitment, and controlled state transitions during embryogenesis and tissue homeostasis. Developmental transcription factors, including members of the SOX family, FOXA1, ASCL1, NKX2-1, and epithelial-mesenchymal transition regulators, function as lineage gatekeepers during development but are repurposed in cancer to destabilize lineage commitment and enable phenotypic switching. Similarly, epigenetic regulators that guide developmental trajectories, including chromatin remodeling complexes, Polycomb group proteins, and DNA methylation machinery, are frequently dysregulated or redistributed in tumors, altering the repression of lineage-stabilizing and alternative lineage programs and thereby weakening epigenetic barriers to lineage transitions. Together, these observations support a model in which development and cancer operate as mirror regulatory systems: one establishing and stabilizing cellular identity, the other exploiting the same regulatory architecture to permit adaptive reprogramming under selective pressure. We further discuss how emerging single-cell and spatial multi-omics technologies, integrated with artificial intelligence-based modeling, enable mapping of cell state landscapes and transitional trajectories, transforming lineage plasticity from a descriptive phenomenon into a measurable and predictable property of tumor evolution.