Genome-wide transcriptional profiling in human squamous cell carcinoma of the skin identifies unique tumor-associated signatures.

The elucidation of specific genetic changes associated with human cancer pathogenesis has focused efforts to relate such changes to the neoplastic phenotype. To further our understanding of the genetic basis of human squamous cell carcinoma (SCC) of the skin, this study used a genome-wide (12 627 sequences) approach to determine transcriptional signatures in lesional and nonlesional sites from five SCC patients. Several novel genes involving the p53 pathway, anti-apoptotic pathways, signal transduction, structural loss and DNA replication, including BCL2A1, MUC4, PTPN11 (SHP2) and FGF9, are upregulated in SCC and could warrant further study regarding their role in disease pathogenesis. SCC pathology is likely combinatorial in nature involving the compounded changes from several cellular processes.

Src kinase activity is required for integrin alphaVbeta3-mediated activation of nuclear factor-kappaB.

Integrin adhesion to extracellular matrix proteins protects adhesion-dependent cells from suspension-induced apoptosis. Previous studies indicate that activation of the transcription factor nuclear factor-kappaB was necessary for the integrin alpha(v)beta3 ligand osteopontin to protect endothelial cells from apoptosis caused by serum withdrawal. In this study, beta3 integrins were overexpressed in smooth muscle cells. When plated on osteopontin, cells overexpressing wild-type beta3 had enhanced cell adhesion, cell spreading, and nuclear factor-kappaB activation compared with vector control. Removal of four amino acids (759X) from the C terminus of beta3 eliminated the ability of the integrin to promote these processes. Single amino acid substitutions indicated that phosphorylation at tyrosine 759 was not required for activation of the transcription factor, however this residue appeared to play a structural role, because mutation to alanine significantly inhibited nuclear factor-kappaB activation. The Src family of tyrosine kinases represents important transducers during integrin signaling, and the C terminus of beta3 has been implicated as the binding site for Src. Immunoprecipitations demonstrated that Src associated with wild-type beta3 integrins, but Src and integrins lacking the C terminus (759X) did not form a complex. Pharmacological inhibition with the Src inhibitor PP2 (4-amino-5-(4-chlorophenyl)-7-(t-butyl)pyrazolo[3,4-d]pyrimidine) or overexpression of kinase-dead c-Src blocked nuclear factor-kappaB activation. Mouse embryonic fibroblasts deficient for Src failed to activate nuclear factor-kappaB when plated on osteopontin, in contrast to control fibroblasts. Together, these experiments indicate that the C terminus of beta3 and Src activity are required for integrin alpha(v)beta3-mediated nuclear factor-kappaB activation.