title: Down-regulation of NKD1 increases the invasive potential of non-small-cell lung cancer and correlates with a poor prognosis.
abstract: BACKGROUND
  As a negative modulator of the canonical Wnt signaling pathway, Naked1 (NKD1) is widely expressed in many normal tissues. However, the expression pattern and clinicopathological significance of NKD1 in patients with non-small-cell lung cancer (NSCLC) is still unclear.
  
  
  METHODS
  Immunohistochemical studies were performed on 35 cases of normal lung tissues and 100 cases of NSCLC, including 66 cases with complete follow-up records. The NKD1 protein and mRNA expressions were detected by western blot and Real-time PCR, respectively. To examine the effect of NKD1 on the invasiveness of lung cancer cells, NKD1 was down-regulated by siRNA in lung cancer cell lines and the invasive ability was then evaluated by the Matrigel invasion assay. In addition, the expressions of Dishevelled-1 and β-catenin proteins, as well as MMP mRNA were also examined in NKD1 knockdown cells.
  
  
  RESULTS
  In 35 fresh lung cancer tissues examined, 27(79%) of them exhibited lower levels of NKD1 protein in comparison with their corresponding normal tissue (P = 0.009). However, the NKD1 mRNA level was significantly higher in cancerous lung tissues, compared with the adjacent normal tissues. In 100 NSCLC tissues, NKD1 was significantly lower in 78 cases (78%) than in the normal specimens, determined by immunohistochemical staining. The reduced NKD1 expression was correlated with histological type (P = 0.003), poor differentiation (P = 0.004), lymph node metastasis (P = 0.013), TNM stage (P = 0.002) and poor survival (62.88 ± 3.23 versus 23.61 ± 2.18 months, P = 0.03). In addition, NKD1 knockdown could up-regulate Dishevelled-1 and β-catenin protein levels, as well as increased MMP-7 transcription and the invasive ability of lung cancer cells. Furthermore, when the NKD1-knockdown cells were treated with Dishevelled-1 antibody, their invasive potential was significantly reduced.
  
  
  CONCLUSIONS
  NKD1 protein is reduced but NKD1 mRNA is elevated in NSCLC. Reduced NKD1 protein expression correlates with a poor prognosis in NSCLC. NKD1 might inhibit the activity of the canonical Wnt pathway through Dishevelled-1.
authors: Department of Pathology, the First Affiliated Hospital and College of Basic Medical Sciences of China Medical University, Shenyang, China.
authors: Sheng
authors: S
authors: Zhang
authors: Yan
authors: Y
authors: Wang
authors: Shun-Dong
authors: SD
authors: Dai
authors: En-Hua
authors: EH
authors: Wang
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