Expression of CD44 in Tumor Tissue and Serum of Small Cell Lung Cancer and Its Clinical Prognostic Significance

Background Small cell lung cancer (SCLC) is a highly aggressive malignancy characterized by rapid growth, early metastasis and acquired therapeutic resistance, and the prognosis is extremely poor. Studies have proved that the stem cell marker CD44 is correlated with tumor recurrence and treatment resistance, however, there are limited reports yet concerning on the CD44 expression and its clinical prognostic significance in SCLC patients. The purpose of this study is to investigate the expression of CD44 in tumor tissues as well as serum of SCLC patients and explore its correlation with the clinical characteristics, therapeutic effect and prognosis. Methods The tumor tissues and serum samples of 47 newly diagnosed SCLC patients were collected. Immunohistochemistry and enzyme-linked immunosorbent assay were applied to detect CD44. The relationship between CD44 level and the clinical characteristics as well as prognosis of the patients was analyzed. Results The stem cell marker CD44 was detectable both in serum sample and tumor tissue of SCLC patients. The positive rate of CD44 in tumor tissue was significantly higher in patients with performance status (PS) 2 than that of patients with PS 0-1 (85.71% vs 30%, P=0.017). Patients were divided in to different groups according to the treatment efficacy. The CD44 immunohistochemical score and serum level in the disease progression group were significantly higher than those in the disease control group, and the differences were statistically significant (P=0.006, P=0.034), Univariate analysis depicted that the progression-free- survival (PFS) of CD44 positive patients was significantly shorter than that of CD44 negative patients (5.23 mon vs 9.03 mon, P=0.036). Conclusions The positive expression of CD44 in tumor tissues of pre-treatment SCLC patients is correlated with poor PFS. The clinical significance of CD44 is worthy to be further studied.