Abstract: Background and purpose: Osteopontin (OPN) is a secreted glyco-phosphoprotein, which is overexpressed by numerous human cancers, invovled in tumor occurrence, development and prognosis. OPN up-regulates matrix metal proteases (MMPs) expression in a NF-κB-dependent fashion during extracellular matrix (ECM) invasion causing degradation of cell basement membrane and ECM leading to tumor invasion and metastasis. The aim of this study was to examine the protein level of OPN in a large number of tissue samples from patients with lung squamous cell carcinoma (SCC), and evaluate its potential clinical value. Methods: The OPN protein levels in 265 tumor tissue samples and corresponding 24 normal lung tissue samples were examined by immunohistochemical (IHC) analysis. Results: IHC results showed that the positive rate of OPN was 64.5% in the SCC tissues, which was significantly higher than that in normal alveoli tissues (29.2%, P<0.001). The positive rate of OPN expression in late stage (Ⅲ+Ⅳ) tissues was 78.4%, significantly higher than that in early stage (Ⅰ+Ⅱ) tissue(positive rate 54.5%, P<0.001). The positive rate of OPN expression in T_3-4 stage (Ⅲ+Ⅳ) tissue was 76.9%, significantly higher than that in T_1-2 stage tissue (positive rate 59.4%, P=0.007). The expression of OPN was signifcantly correlated with the status of lymph node metastasis (LNM). The positive rate in the tumor tissue with LNM was 73.4%, significantly higher than that without (positive rate 51.4%, P<0.001). Conclusion: The level of OPN protein was overexpressed in lung cancer tissues, involved in SCC carcinogenesis and LNM. It is indicated that OPN has an important reference value in diagnosis, prognosis and therapy of SCC.

Key words: Osteopontin, Lung squamous cell carcinoma, Lymph node metastasis