Protein and mRNA expression of osteopontin in lung cancer and clinical significance thereof

Abstract

To investigate the protein and mRNA expression of osteopontin (OPN) in the lung cancer tissue and explore the roles thereof in the development and progression of lung cancer. Immunohistochemistry and in situ hybridization were used to detect the protein and mRNA expression of OPN in 57 specimens of lung cancer tissue, 30 specimens of inflammatory pseudotumors and 20 specimens of pulmonary bulla, all obtained during operation. The OPN protein expression rate of the lung cancer tissue was 57.9% (33/57) , significantly higher than that of the inflammatory pseudotumor (16.7%, 5/30, chi2 = 13.581, P = 0.000). The OPN mRNA expression rate in the lung cancer tissue was 71.9% (41/57), significantly higher than that of the inflammatory pseudotumor (30.0%, 9/30, chi2 = 14. 138, P = 0.000). All the 20 specimens of pulmonary bullae were negative in the expression of OPN, both at the protein and mRNA levels. The OPN protein and mRNA expression rates of the lung cancer tissues with lymph node metastasis were 71.1% (27/38) and 86.8% (33/38) respectively, both significantly higher than those of the lung cancer tissue without lymph node metastasis [31.6% (6/19) and 42.1% (8/19) respectively, chi2 = 6.558, P = 0.010, and chi2 = 10.438, P = 0.001]. The OPN protein and mRNA expression rates of the non-small lung cancer tissues were 68.1% (32/47) and 78.7% (37/47) respectively, both significantly higher than those of the small lung cancer tissues [10% (1/10) and 25% (4/10) respectively, chi2 = 11.412, P = 0.001, and chi2 = 6.124, P = 0.013]. The OPN protein expression was positively correlated with the OPN mRNA expression in the lung cancer tissues (r = 0.623, P = 0.001). The 57 patients with lung cancer after surgery were followed up for 28 (24-40) months, 8 of the 32 patients with both positive OPN protein and mRNA expression had recurrence and 13 patients had a distant metastasis, while only 1 of the 15 cases negative in both OPN protein and mRNA expression showed recurrence (chi2 = 14.258, P = 0.000). 12 patients died in the both positive expression group but no patient died in the both negative expression group (chi2 = 7.554, P = 0.006). Over-expressions of OPN protein and OPN mRNA are found in lung cancer tissues and their expressions are correlated to the prognosis and metastasis of lung cancer.