Single-cell transcriptomic landscape of keratinocyte transformation from actinic keratosis to skin carcinoma

Cutaneous squamous cell carcinoma (cSCC) develops through a stepwise progression from normal skin (NS) to actinic keratosis (AK) and invasive carcinoma. To delineate the cellular and molecular events underlying this transition, we perform single-cell RNA sequencing on 65,485 cells from NS, AK, and cSCC tissues. The analysis revealed dynamic remodeling of keratinocyte, T cell, and B cell populations during disease progression. A progressively expanding KRT6A ⁺ KRT16 ⁺ keratinocyte subpopulation (Ker-6) displayed an increasing copy number variation burden and activation of tumor-associated pathways. Ligand-receptor analysis indicated that Ker-6 keratinocytes engage proliferative T cells via the interleukin (IL)-13/IL13RA1/IL4R signaling axis. Functional assays using IL13RA1 and IL4R knockdown confirmed that IL-13 signaling promotes keratinocyte proliferation and migration. These findings define a key immunoregulatory pathway linking epithelial transformation and immune interaction, providing a cellular framework for understanding early cSCC development and identifying potential targets for intervention.