Membrane Location of Syntaxin-Binding Protein 1 Is Correlated with Poor Prognosis of Lung Adenocarcinoma

Abstract

Lung cancer is the leading cause of cancer-related death, and adenocarcinoma is the most common histological type of lung cancer. Syntaxin-binding protein 1 (STXBP1) is essential for exocytosis of secretory vesicles. Since exocytosis is the basic cellular process of cells, we investigated STXBP1 expression and clinical significance in lung adenocarcinoma. We performed quantitative real-time polymerase chain reaction in 20 pairs of lung adenocarcinoma and paired normal tissues, and demonstrated that the relative expression levels of STXBP1 mRNA in lung adenocarcinoma was significantly higher than those in normal lung tissues. We then carried out immunohistochemistry (IHC) to determine the expression profile of STXBP1 in 276 lung adenocarcinoma specimens, and categorized patients into subgroups with low or high STXBP1 expression, based on the IHC score. Moreover, STXBP1 expression phenotypes were categorized as membrane, cytoplasm, and mixed expression (both membrane and cytoplasm) expression. High STXBP1 protein accounted for 58.0% of all the 276 cases (160/276), and membrane, cytoplasm or mixed STXBP1 accounted for 28.75%, 25.63% and 45.63% in the 160 cases of high STXBP1 expression. The clinical significances of these phenotypes were evaluated by analyzing their correlation with clinicopathological factors, as well as their prognostic values. Consequently, the whole STXBP1 expression or membranal STXBP1 expression were correlated with poor prognosis and were independent prognostic factors of lung adenocarcinoma. The whole and membranal STXBP1 expression are independent prognostic factors of lung adenocarcinoma. STXBP1 detection is capable to help screen patients who may have poor prognosis and strengthen the adjuvant therapy more precisely.