SLPI Protein Levels In Circulating Plasma And Tumor Tissue Of Lung Cancer Patients And Their Clinical Significance

Background:Lung cancer is the leading cause of cancer deaths throughout the world. The poor prognosis with only 10-15%patient surviving 5 years after diagnosis is largely due to the lack of efficient methods for early detection. However, a noninvasive blood test of tumor markers is promising. Our previous study demonstrated that secretory leukoprotease inhibitor (SLPI) was detected in condition medium of primary cell culture or organ culture of lung cancer. Besides, SLPI gene was also detected up-regulation in some other cancers, but the expression in lung cancer remain controversial. Our primary object is to test SLPI expression levels in lung cancer tissue and Circulating plasma. Then, we test if it can be used as a tumor marker.Methods:Circulating plasma SLPI level in 123 patients with primary lung cancer and in 53 health subjects were measured by an enzyme immunoassay. Fifty eight specimens from patients with primary lung cancer were also examined by immunohistochemistry(IHC). Then, the accuracy of SLPI in the diagnosis of lung cancer was also measured alone or combining with other biomarkers.Results:The results of the current study showed that the plasma levels of SLPI in patients with primary lung cancer were significantly elevated compared with the healthy controls (P=0.007). When classifying primary lung cancer by its histology, SLPI levels in patients of squamous cell carcinoma (SCC, n=53) and small cell lung cancer (SCLC, n=12) were significantly higher than those in patients of adenocarcinoma (P=0.002). The SLPI levels in advanced group (Stageâ…¢andâ…£, n=56) were significantly higher than those in non advanced group (Stageâ… andâ…¡, n=67), and plasma SLPI levels also were elevated in the patients with lymph node metastatic (n=73) compared with patients without metastatic (n=50, P<0.001). Immunohistochemical study showed that SLPI underexpressed in lung cancer tissues compared with in normal bronchial (P<0.001). When used as a tumor marker for SCC and SCLC alone, at 98%specificity, SLPI has a sensitivity of 49%and 50%(cutoff=88.6ng/ml), respectively. Combining with both markers which are using in the clinic did improve the diagnostic performance.Conclusion:Plasma SLPI levels elevated in squamous cell carcinoma and small cell carcinoma, it is feasible that using SLPI as an adjunctive tumor marker in diagnosis of lung cancer.