Analysis of αv integrin protein expression in human eyelid and periorbital squamous cell carcinomas

Background: Alpha v integrins are receptors for many extracellular matrix (ECM) protein ligands, including latent transforming growth factor betas (TGFβs). Various studies in mice have shown that ablation of genes encoding αv integrin or TGFβ signaling pathway components leads to spontaneous squamous cell carcinomas (SCCs) in the conjunctiva and periocular skin. Here, we have analyzed patterns of αv integrin protein expression and TGFβ signaling in human eyelid and periorbital SCC samples. Methods: An anti-αv integrin antibody was used to immunostain 19 eyelid and periorbital SCC samples. Additionally, tissue lysates from resected normal eyelid and SCC samples were analyzed by immunoblotting for αv integrin protein. Tumor sections were also immunostained with an antibody directed against Smad2, an intracellular signaling protein that is phosphorylated by TGFβ receptors. Results: Alpha v integrin protein was highly expressed in the invasive and less-differentiated components of human SCCs. Lower levels of αv integrin protein were detected in more differentiated components of tumors, as well as in SCC in situ. Patterns of phosphorylated Smad2 immunoreactivity correlated with levels αv integrin expression. Conclusions: Alpha v integrin was expressed at robust levels in tumor cells representing less differentiated, more invasive components of SCC; by contrast, well-differentiated cells as well as SCC in situ expressed low levels of αv integrin protein.