title: Topoisomerase I expression is associated with prognosis in postoperative non-small cell lung cancer patients.
abstract: BACKGROUND
  Biomarkers may help to improve non-small cell lung cancer (NSCLC) prognosis. However, the prognostic effect of topoisomerase I (Topo I) on NSCLC is unknown. We evaluated the clinicopathologic and prognostic significance of tumor Topo I and thymidylate synthase (TS) protein expression in postoperative NSCLC patients.
  
  
  METHODS
  One hundred and fifteen patients with postoperative NSCLC were enrolled. Topo I and TS protein were detected in removed tumors by immunohistochemistry. The correlations between Topo I/TS protein expression and clinicopathologic characters and outcomes of patients were analyzed.
  
  
  RESULTS
  Increased expression of Topo I was found in 57 (49.6%) tumors. The largest diameter of the tumor was significantly different between patients with high and low Topo I expression (P = 0.035). TS staining showed that 35 (30.4%) carcinomas were TS positive. The level of TS expression was correlated with tumor differentiation (P = 0.037). Patients with low Topo I expression had significantly longer overall survival (OS) than those with high expression (P = 0.004). The correlation between Topo I expression and OS was demonstrated among patients with squamous cell carcinoma (P = 0.030) and patients in pathological tumor node metastasis stage I (P = 0.027). Topo I expression was positively correlated with TS expression in tumor tissue (R = 0.251, P = 0.007).
  
  
  CONCLUSIONS
  Low Topo I expression is an independent favorable prognostic factor for longer OS in postoperative NSCLC patients, especially in squamous cell carcinoma. There is a correlation between the expression of TS and Topo I in removed tumor tissue.
authors.affiliation: Division of Medical Oncology Beijing Chest Hospital, Capital Medical University Beijing China.
authors.forename: Baohua
authors.initials: B
authors.lastname: Lu
authors.affiliation: Division of Medical Oncology Beijing Chest Hospital, Capital Medical University Beijing China.
authors.forename: Hongmei
authors.initials: H
authors.lastname: Zhang
authors.affiliation: Division of Medical Oncology Beijing Chest Hospital, Capital Medical University Beijing China.
authors.forename: Tongmei
authors.initials: T
authors.lastname: Zhang
authors.affiliation: Division of Pathology Beijing Chest Hospital, Capital Medical University Beijing China.
authors.forename: Yiran
authors.initials: Y
authors.lastname: Cai
authors.affiliation: Division of Medical Oncology Beijing Chest Hospital, Capital Medical University Beijing China.
authors.forename: Ying
authors.initials: Y
authors.lastname: Hu
authors.affiliation: Division of Medical Oncology Beijing Chest Hospital, Capital Medical University Beijing China.
authors.forename: Hua
authors.initials: H
authors.lastname: Zheng
authors.affiliation: Division of Medical Oncology Beijing Chest Hospital, Capital Medical University Beijing China.
authors.forename: Baolan
authors.initials: B
authors.lastname: Li
keywords: Non‐small cell lung cancer; prognosis; topoisomerase I