DNA Damage Promotes Epithelial Hyperplasia and Fate Mis-specification via Fibroblast Inflammasome Activation.

DNA crosslinking agents are commonly used in cancer chemotherapy; however, responses of normal tissues to these agents have not been widely investigated. We reveal in mouse interfollicular epidermal, mammary and hair follicle epithelia that genotoxicity does not promote apoptosis but paradoxically induces hyperplasia and fate specification defects in quiescent stem cells. DNA damage to skin causes epithelial and dermal hyperplasia, tissue expansion, and proliferation-independent formation of abnormal K14/K10 dual-positive suprabasal cells. Unexpectedly, this behavior is epithelial cell non-autonomous and independent of an intact immune system. Instead, dermal fibroblasts are both necessary and sufficient to induce the epithelial response, which is mediated by activation of a fibroblast-specific NLRP3 inflammasome and subsequent IL-1ß production. Thus, genotoxic agents that are used chemotherapeutically to promote cancer cell death can have the opposite effect on wild-type epithelia by inducing, via a non-autonomous IL-1ß-driven mechanism, both hyperplasia and stem cell lineage defects.