Epithelial-dermal inflammasome crosstalk in cutaneous squamous cell carcinoma

Epithelia maintain their barrier function through the proliferative and plastic behavior of stem cells that drive continuous tissue regeneration. However, these same properties render epithelia susceptible to tumorigenesis. The skin, the largest epithelial barrier, is the source of the most prevalent human cancers, yet the molecular mechanisms by which stem cells and their microenvironment cooperate to promote cutaneous cancer development remain incompletely defined. Previous work demonstrated that genotoxic injury in normal skin activates epithelial-dermal inflammasome signaling that drives epithelial stem cell hyperproliferation and misspecification. Here, we investigated whether this mechanism also operates in diseased skin. We found that stem cell misspecification is a broadly conserved feature across pathological skin conditions but is absent in normally proliferating tissue. Notably, inflammasome activation is detected in both epithelial and dermal compartments of cutaneous squamous cell carcinoma (cSCC), but not in other skin pathologies. Mechanistically, oncogenic KRAS expression in keratinocytes triggers inflammasome activation before tumor formation non-cell autonomously. Furthermore, IL-1 signaling is activated in fibroblasts adjacent to the cSCC tumor interface, but not in the overlying epithelium. Taken together, these findings support a model in which KRAS-driven epithelial-fibroblast inflammasome crosstalk establishes a feed-forward IL-1 signaling loop that enhances the tumor-promoting microenvironment in cSCC.