Key differences identified between actinic keratosis and cutaneous squamous cell carcinoma by transcriptome profiling

Cutaneous squamous cell carcinoma (cSCC) is one of the most common malignancies in fair skinned populations worldwide and its incidence is increasing. Despite previous observations of multiple genetic abnormalities in cSCC, the oncogenic process remains elusive. The purpose of this study was to investigate the transcriptomes of cSCC and actinic keratoses (AK), to elucidate key differences between precursor AK lesions and invasive carcinoma. This study identified 196 genes that are differentially expressed between AK and cSCC, with enrichment for processes including epidermal differentiation, cell migration, cell cycle regulation and metabolism. Gene set enrichment analysis highlighted a key role for the MAPK pathway in the transition from AK to cSCC. Furthermore, the differentiation status of the tumor influenced the gene expression profile, which may have implications for drug sensitivity and response in clinical trials. These data indicate that progression to cSCC is associated with a complex pattern of molecular changes. We have identified relevant pathways involved in this process, in particular that the MAPK pathway may be pivotal to the transition from AK and may represent a potential therapeutic target. RNA was extracted by laser capture microdissection from 10 AK and 30 cSCC, for analysis using the Affymetrix HG U133 Plus 2.0 microarrays. The cSCC samples included a range of histological diagnoses (well differentiated through to poorly differentiatied) from both immunocompetent and immunosuppressed patients.