Early fibrotic niches establish tumour-permissive microenvironments [Experiment 3]

Pathologic transformation represents a pivotal yet poorly defined window during which early alterations in epithelial stem cells remodel their surrounding niche to prime tumour initiation. Here, we integrate single-cell, spatial, and functional analyses to map the dynamics of this early multicellular reorganisation. We show that KrasG12D-mutant alveolar type II cells undergo an early reprogramming transition that transforms them into signalling hubs, with the Amphiregulin (Areg)-EGFR axis emerging as a central driver of cross-compartmental cooperation. Mutant epithelial cells secrete Areg to activate EGFR in adjacent fibroblasts, eliciting a regenerative-like fibrotic programme. These reprogrammed fibroblasts, in turn, reshape the immune landscape by expanding and reprogramming alveolar macrophages, amplifying inflammatory signalling, immune recruitment, and epithelial plasticity. Together, these interactions establish a self-reinforcing multicellular circuit that generates and maintains a tumour permissive niche. Disrupting that circuit through genetic and pharmacological perturbation of the Areg-EGFR axis prevents both early niche cell reprogramming and tumour formation. Findings from KRASG12D-inducible human alveolar organoids and early-stage lung adenocarcinoma tissues confirm conservation of these interactions, identifying early mutant epithelial-stromal crosstalk as a targetable step in pathologic transformation with potential to avert establishment of treatment-resistant disease.