Osteopontin stimulates invasion of NCI-h295 cells but is not associated with survival in adrenocortical carcinoma

Gene array studies indicated that osteopontin (OPN) mRNA is highly expressed in adrenocortical carcinomas (ACCs). OPN enhances invasiveness, proliferation, and metastasis formation, and is associated with poor survival in some malignant diseases. Integrin alpha v beta 3 has been shown to mediate OPN effects on invasion. In this study, we demonstrated OPN and integrin alpha v beta 3 expression in normal adrenal glands and benign adenomas, with staining seen exclusively in adrenocortical cells as well as even stronger staining in ACC. Western blot analysis confirmed overexpression of OPN in ACC (p < 0.01). With Matrigel invasion assays, we have shown that OPN greatly stimulates the invasiveness of NCI-h295 cells (>six-fold increase, p < 0.001). Transfection with integrin alpha v beta 3 further increased invasiveness after OPN stimulation (p < 0.001). This increase was reversed by the addition of an anti-integrin beta 3 antibody, indicating a functional relationship of OPN and integrin av beta 3 in ACC. With tissue arrays, we confirmed high OPN expression in 147 ACC samples. However, no association with survival was seen in Kaplan-Meier analysis including Ill patients with primary tumours graded for OPN staining and follow-up data available. In conclusion, our in vitro data indicate that OPN and integrin alpha v beta 3 may act as a functional complex facilitating the invasiveness of adrenocortical tumours. This relationship remains of relevance to our understanding of carcinogenesis, but further studies are needed to address the physiological and pathological function of OPN in adrenal tissue. Copyright (c) 2009 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.