Immunohistochemical analysis of integrins αvβ3, αvβ5 and α5β1, and their ligands, fibrinogen, fibronectin, osteopontin and vitronectin, in frozen sections of human oral head and neck squamous cell carcinomas

Integrins mediate the interaction of cells with the extracellular matrix and are believed to be involved in tumor cell survival and metastasis, and in tumor angiogenesis. We used immunohistochemistry of fresh-frozen human tumor tissues to analyze the presence of integrins alpha v beta 3, alpha v beta 5 and alpha 5 beta 1, which are believed to be involved in tumor growth and migration, together with integrin ligands, vitronectin, osteopontin, fibronectin and fibrinogen, in human oral squamous cell carcinomas. Samples of squamous cell carcinomas and control tissues from patients without cancer undergoing oral or maxillofacial surgery were frozen in liquid nitrogen within 30 min of removal. Frozen sections were prepared, and the presence of integrins or ligands was visualized using standard immunohistochemistry (APAAP) with a blinded evaluation. Comparison of samples from the 40 oral cancer patients and the 20 controls revealed increased staining in tumors compared with the controls, and staining was demonstrated for alpha v beta 3 in endothelia. alpha v beta 5 staining was increased in the tumor samples, but this was associated with increased expression in stroma rather than in endothelia. Modestly increased expression of alpha 5 beta 1 was observed in the tumor samples, and this was associated with tumor cells, endothelia and stroma. Expression of ligands for the integrins varied between tissue types, with increased fibrinogen and fibronectin expression in tumor endothelia. Confirmation of the presence of these integrins and their association with tumor cells, endothelia or stroma suggests their potential for these integrins in human oral tumors. Overall, the increased expression of integrins within tumors, particularly expression associated with endothelial cells, supports the principle of selective integrin blockade as a novel anticancer strategy.