Single-cell sequencing highlights heterogeneity and malignant progression in actinic keratosis and cutaneous squamous cell carcinoma

Abstract

Cutaneous squamous cell carcinoma (cSCC) is the second most frequent of the keratinocyte-derived malignancies with actinic keratosis (AK) as a precancerous lesion. To comprehensively delineate the underlying mechanisms for the whole progression from normal skin to AK to invasive cSCC, we performed single-cell RNA-seq (scRNA-seq) to acquire the transcriptomes of 138,982 cells from 13 samples of six patients including AK, squamous cell carcinoma in situ (SCCIS), cSCC and their matched normal tissues, covering comprehensive clinical courses of cSCC. We identified diverse cell types, including important subtypes with different gene expression profiles and functions in major keratinocytes. In SCCIS, we discovered the malignant subtypes of basal cells with differential proliferative and migration potential. Differentially expressed genes (DEGs) analysis screened out multiple key driver genes including transcription factors (TFs) along AK to cSCC progression. Immunohistochemistry (IHC) / immunofluorescence (IF) experiments and single-cell ATAC sequencing (scATAC-seq) data verified the expression changes of these genes. The functional experiments confirmed the important roles of these genes in regulating cell proliferation, apoptosis, migration and invasion in cSCC tumor. Furthermore, we comprehensively described the tumor microenvironment (TME) landscape and potential keratinocyte-TME crosstalk in cSCC providing theoretical basis for immunotherapy. Together, our findings provide a valuable resource for deciphering the progression from AK to cSCC and identifying potential targets for anticancer treatment of cSCC.

Advancements in elucidating the pathogenesis of actinic keratosis: present state and future prospects

“…In particular, the suppression of apoptosis in response to UV-induced damage by the E6 protein from various cutaneous HPV types might significantly contribute to giving genetically damaged keratinocytes a survival edge, leading to the development of AK and cSCC ( 47 ). Epidermodysplasia verruciformis-associated HPVs (EV-HPVs) might also play a crucial role in the emergence of AK, as indicated by serological studies, and are implicated in the pathogenesis of SCC ( 48 ). In EV-associated cSCCs, a variety of betaHPV types, notably HPV5 and HPV8, are identified.…”