| Lung cancer is a major health problem due to its high incidence andpoor curability. This disease is the most fatal cancer in the world and itis estimated that there have been over 1300 000 lung cancer deaths inthe year 2000 . The enormous fatality rate reflects the limited chance ofcure, with a dismal overall 5-year survival rate of approximately 14% inthe United States. In Europe, over 90% of all cases diagnosed die within5 years . Two thirds of cases have advanced disease at diagnosis and thevast majority die of cancer despite aggressive multimodalitymanagement. Surgical excision is still the most effective way to achievelocal control and permanent cure, but is only applicable to 25-30% ofcases due to the tumour burden . Few clinically useful tumor markers have been identified for themanagement of human lung cancer. New tumor markers and markers oftumor progression are needed for improved staging and treatment of manycancers. At present, despite a large number of potential markers of cancerhaving been identified, carcinoembryonic antigen is the only tumor markerthat has gained widespread clinical use in the management of human lungcancer. Its use, however, is marred by its lack of expression in a significantnumber of cancers and its lack of correlation with tumor response totherapy. Gene expression pro-filing techniques offer the opportunity todiscover new molecular markers . Osteopontin is an acidic glycoprotein with a protein backbone ofabout 32.5 kDa. It is rich in aspartate, glutamate and serine and containsabout 30 monosaccharides, including 10 sialic acids. Carbohydrate ispresent as one N-glycosyl and five to six O-glycosyl side chains.Phosphorylation occurs to a variable extent, possibly on up to 28 sites ,distributed throughout the molecule . Osteopontin is produced byosteoclasts, macrophages, T-cells, kidneys, and vascular smooth musclecells. It contributes to macrophage homing and cellular immunity. It alsomediates neovascularization and inhibits apoptosis. Finally, osteopontinmaintains the homeostasis of free calcium. Purpose : Osteopontin(OPN), an integrin-binding, transformation-associated protein, is secreted by tumor cell lines in culture and isassociated with increased malignancy in some experimental tumor systems.Little is know, however, about the significance in human cancer. The aimsof this study were to investigate the expression of osteopontin(OPN)mRNA in lung cancer and adjacent normal tissues and the clinicalsignificance of OPN in tumorigenesis of lung cancer. Methods: Quantitative real-time reverse transcription-PCR wasused to analyze OPN mRNA in normal lung tissue and matching tumorsamples from 22 patients with lung cancer. Gene expression data foreach patient were matched to classification of histological pathology oflung cancer. Results: The overall median mRNA expression level of OPN was15-fold higher in tumor tissues than in matching normal lung tissues(P<0.000). OPN was predominantly expressed in non-small cell lungcancer(NSCLC) tissues: 7 of 11 cases of squamous cell carcinoma (SCC) ,two of 9 cases of adenocarcinoma, but not in two cases of small cell lungcancer. Conclusion: The large increase of OPN expression in tumorscompared with normal tissue, and OPN is mainly expressed in NSCLC,especially among SCC. OPN may have strong relationship with NSCLC,and may be a potential clinical marker for NSCLC. |
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