Genome-wide comparison of human keratinocyte and squamous cell carcinoma responses to UVB irradiation: implications for skin and epithelial cancer

Abstract

To gain insight into the transformation of epidermal cells into squamous carcinoma cells (SCC), we compared the response to ultraviolet B radiation (UVB) of normal human epidermal keratinocytes (NHEK) versus their transformed counterpart, SCC, using biological and molecular profiling. DNA microarray analyses (Affymetrix s , B12 000 genes) indicated that the major group of upregulated genes in keratinocytes fall into three categories: (i) antiapoptotic and cell survival factors, including chemokines of the CXC/CC subfamilies (e.g. IL-8, GRO-1, -2, -3, SCYA20), growth factors (e.g. HB-EGF, CTGF, INSL-4), and proinflammatory mediators (e.g. COX-2, S100A9), (ii) DNA repair-related genes (e.g. GADD45, ERCC, BTG-1, Histones), and (iii) ECM proteases (MMP-1, -10). The major downregulated genes are DNp63 and PUMILIO, two potential markers for the maintenance of keratinocyte stem cells. NHEK were found to be more resistant than SCC to UVB-induced apoptosis and this resistance was mainly because of the protection from cell death by secreted survival factors, since it can be transferred from NHEK to SCC cultures by the conditioned medium. Whereas the response of keratinocytes to UVB involved regulation of key checkpoint genes (p53, MDM2, p21 Cip1 , DNp63), as well as antiapoptotic and DNA repair-related genes -no or little regulation of these genes was observed in SCC. The effect of UVB on NHEK and SCC resulted in upregulation of 251 and 127 genes, respectively, and downregulation of 322 genes in NHEK and 117 genes in SCC. To further analyse these changes, we used a novel unsupervised coupled two-way clustering method that allowed the identification of groups of genes that clearly partitioned keratinocytes from SCC, including a group of genes whose constitutive expression levels were similar before UVB. This allowed the identification of discriminating genes not otherwise revealed by simple static comparison in the absence of UVB irradiation. The implication of the changes in gene profile in keratinocytes for epithelial cancer is discussed.

S100A2 gene is a direct transcriptional target of p53 homologues during keratinocyte differentiation

“…As expected for a mutant p53 protein, no modification of its expression was found in response to cisplatin (Figure 6a). We found that while p73-mediated growth arrest and apoptotic target genes p21 waf1 , bax, p53AIP1, pig-3 were induced upon cisplatin treatment, S100A2 mRNA and protein, in agreement with previously reported findings (Dazard et al, 2003), were downregulated (Figure 6a-c). Similar findings were obtained upon treatment of HaCaT cells with doxorubicin (data not shown).…”

Post-Transcriptional Regulation of DNA Damage-Responsive Gene Expression

“…Even in the absence of p53, the same gene size relationship exists for UV-induced genes (109). Compact p53-independent UV-induced genes included AP-1 responsive immediate early genes, NFjB-regulated cytokines and histones (1,29,48,55,168). Therefore, UV-induced genes tend to be compact, regardless of the transcription factor driving expression.…”

Double‐stranded RNA induces S100 gene expression by a cycloheximide‐sensitive factor

“…Beside their constitutive expression in myeloid cells, they are expressed in epithelial cells in response to stress [14,15]. Their expression is transiently induced in keratinocytes after epidermal injury [16,17], after UVB irradiation [18], and in response to proinflammatory cytokines such as TNFa and IL1b [14]. Data showing that the two S100 proteins are up regulated by the putative TLR ligand LPS are conflicting [19,20].…”