['Non-small cell lung cancer (NSCLC) is one of the most common malignant tumors. Despite the advances in therapy over the years, its mortality remains high. The aim of this study was to evaluate the expression of small ubiquitin-like modifier (SUMO) proteases 1 (SENP1) in NSCLC tissues and its role in the regulation of vascular endothelial growth factor (VEGF) expression. We also investigated the association between the expression level of SENP1 and the clinicopathological features and survival of the patients.', 'A SENP1 small interfering RNA (siRNA) was constructed and transfected into the NSCLC cells. VEGF gene expression was analyzed by real-time polymerase chain reaction (RT-PCR). Immunohistochemistry staining was used to assess the expression of SENP1 in 100 NSCLC patients and its association with the clinicopathological features and survival was analyzed.', 'VEGF expression was significantly higher in NSCLC tissues than in normal lung tissues. Inhibition of SENP1 by siRNA was associated with decreased VEGF expression. SENP1 was over-expressed in 55 of the 100 NSCLC samples (55%) and was associated with a moderate and low histological tumor grade (3.6%, 38.2%, and 58.2% in high, moderate and low differentiated tumors, respectively, P = 0.046), higher T stage (10.9% in T1, and 89.1% in T2 and T3 tumor samples, P < 0.001) and TNM stage (10.9% in stage I, and 89.1% in stages II and III tumor samples, P < 0.001). The rate of lymph node metastasis was significantly higher in the SENP1 over-expression group (76.4%) than that in the SENP1 low expression group (33.3%, P < 0.001). Sixty three patients received postoperative chemotherapy, including 34 with SENP1 over-expression and 29 with SENP1 low expression. Among the 34 patients with SENP1 over-expression, 22 (64.7%) patients developed recurrence or metastasis, significantly higher than those in the low expression group 27.6% (8/29) (P = 0.005). Multivariate Cox regression analysis showed that lymph node metastasis (P = 0.015), TNM stage (P = 0.001), and SENP1 expression level (P = 0.002) were independent prognostic factors for the survival of NSCLC patients.'] Does over-expression of small ubiquitin-like modifier proteases 1 predict chemo-sensitivity and poor survival in non-small cell lung cancer?