Low claudin-6 expression correlates with poor prognosis in patients with non-small cell lung cancer

Abstract

Qiang Wang,1 Yan Zhang,1 Tao Zhang,2 Zhi-Gang Han,1 Li Shan1 1Department of Thoracic Oncology, The Affiliated Tumor Hospital of Xinjiang Medical University, Urumqi, Xinjiang Province, 2Department of Oncology, First Hospital of Lanzhou University, Lanzhou, Gansu Province, People’s Republic of China Objective: Claudins are found in junctional complexes mediating cell adhesion and are involved in the attachment of tight junctions to the underlying cytoskeleton. Abnormal claudin-6 expression has been observed for a variety of malignant solid tumors, but the expression of claudin-6 in non-small cell lung cancer (NSCLC) has not yet been characterized.Methods: Immunohistochemistry, reverse transcription-polymerase chain reaction (RT-PCR), and western blot analysis were used to quantify claudin-6 expression in 123 cases of NSCLC and non-cancerous adjacent tissue. We analyzed the relationship between claudin-6 expression and clinicopathological features of NSCLC. The Kaplan–Meier method was used to analyze postoperative survival rates, and the log-rank test was used to assess differences in survival rates. The Cox regression model was used to perform multivariate analysis.Results: Claudin-6 expression was low for 61 of 123 (49.6%) NSCLC tissue samples and for 33 of 123 (26.8%) normal adjacent tissue samples. RT-PCR and western blot analyses confirmed the immunohistochemistry results. Claudin-6 expression was associated with lymph node metastasis (P<0.001) and TNM stage (P=0.007). Kaplan–Meier analysis indicated that patients with low claudin-6 expression had significantly lower survival rates than those with high claudin-6 expression. Multivariate analysis suggested that low claudin-6 expression was an independent indicator of prognosis in NSCLC patients.Conclusion: Low claudin-6 expression is an independent prognostic biomarker that indicates a worse prognosis in patients with NSCLC. Keywords: NSCLC, claudin-6, immunohistochemistry, RT-PCR, western blot