Overexpression of osteopontin is associated with more aggressive phenotypes in human non-small cell lung cancer

Purpose: The extracellular matrix (ECM) molecule osteopontin is implicated in many pathologic processes, including inflammation, cell proliferation, ECM invasion, tumor progression, and metastasis. The present study evaluated the clinical and biological importance of osteopontin in human lung cancer. Experimental Design and Results: Tissue microarrays derived from non-small cell lung cancer (NSCLC) patients were analyzed immunohistochemically. Osteopontin protein expression was observed in 64.5% (205 of 318) of primary tumors and 75.5% (108 of 143) of lymph node metastases, but in only 27.9% (12 of 43) of normal-appearing bronchial epithelial and pulmonary tissues. Osteopontin expression was associated with tumor growth, tumor staging, and lymph node invasion. In vitro osteopontin enhanced ECM invasion of NSCLC cells, and an osteopontin antibody abolished this effect. We further analyzed osteopontin levels in circulating plasma derived from 158 patients with NSCLC, 54 patients of benign pulmonary disease, and 25 healthy donors, and found that the median osteopontin levels for the three groups were 319.1, 161.6, and 17.9 ng/mL, respectively. Conclusions: Overexpression of osteopontin is common in primary NSCLC and may be important in the development and progression of the cancer. Osteopontin levels in the plasma may serve as a biomarker for diagnosing or monitoring patients with NSCLC.