Differential osteopontin expression in lung cancer

Osteopontin (OPN) is a phosphorylated glycoprotein with diverse functions i ncluding cancer development, progression and metastasis. Its expression is induced by a variety of stimuli Such as TNF-alpha and Ras proto-oncogene, H owever, differential OPN expression and its regulation in each histologic t ype of lung cancer are not well established. In this study, we assessed exp ression of OPN in lung cancer tissues with immunohistochemical analysis. OP N was predominantly expressed in tumor cells of non-small cell lung cancer (NSCLC) tissues: 11 of 16 cases (68.8%) of squamous cell carcinoma (SCC), f ive of 24 cases (20.8%) of adenocarcinoma (AD), but only two of 18 cases (1 1%) of small cell lung cancer (SCLC). Expectedly, OPN was principally expre ssed in NSCLC cell lines (H322 cells and HL460 cells) but not in SCLC cell line (H69 cells) by Western blotting and Northern blotting. Interestingly, Ras-p21 was specifically co-expressed with OPN staining in eight of eight c ases with SCC (100%), whereas it was demonstrated in three of ten cases (30 %) with AD and only one of 18 cases (5%) with SCLC, Collectively, these res ults suggest that OPN is mainly expressed in NSCLC, especially among SCC. O PN expression may be tightly regulated by Ras oncogene, and its concomitant induction with Ras activation may play a crucial role in the development o f SCC. (C) 2001 Elsevier Science Ireland Ltd. All rights reserved.