Molecular profiling of cutaneous squamous cell carcinoma

Abstract

Cutaneous squamous cell carcinoma (cSCC) is the second most common form of non-melanoma skin cancer and accounts for the majority of deaths from this disease. Its incidence is increasing rapidly, contributing significant morbidity to patients and a burden on healthcare resources. The molecular events underlying cSCC development remain largely uncharacterised, despite the well established role of ultraviolet radiation as a principal carcinogen. Genomewide analyses of the genetic changes underlying cSCC development have shown they are subject to large chromosomal aberrations, which often involve whole chromosome arms. Many of these events occur in a high proportion of tumours, yet the genes they target are unknown. In this study, genomewide expression microarray data has been obtained from a series of cSCC and integrated with single nucleotide polymorphism (SNP) microarray data, to provide a comprehensive analysis of the events associated with tumour development. In total, 222 genes were identified as differentially expressed in cSCC, of which, 21% were concordant with copy number changes. Previous genomewide SNP data of cSCC had identified microdeletions within the PTPRD gene in a subset of tumours (Purdie et al., 2009). This was investigated in further detail and revealed microdeletions in this gene were significantly associated with metastatic cSCC. Sequencing analysis showed 37% of cSCC had a mutation at this locus, which suggests PTPRD is aberrant in a significant proportion of tumours. Decreased expression levels of PTPRD were correspondingly found in moderately and poorly differentiated tumours. The role of PTPRD in skin biology is not known and further functional work is required to elucidate its role in skin cancer. Taken together, these data provide a valuable insight into the genetic background against which cSCC develop. Furthermore, the association of PTPRD disruption with aggressive tumours may potentially be of future benefit as a prognostic biomarker and therapeutic target.