Objective: Expression of N-myc downstream-regulated gene 1 (NDRG1)/Cap43 is a prognostic indicator of human malignancies according to the tumor type in which it occurs. We investigated how NDRG1/Cap43 could affect tumor growth and angiogenesis in non-small-cell lung cancer (NSCLC) in vivo using an animal experimental model, and also how it could affect tumor angiogenesis and prognosis in NSCLC patients.
Methods and results: Knockdown of NDRG1/Cap43 in lung cancer cells using a specific small interfering RNA resulted in growth rates in culture that were similar to those of counterpart control cells, but decreased tumor growth rates in vivo markedly. Stable NDRG1/Cap43 knockdown did not induce consistent changes in the expression of Epidermal growth factor receptor (EGFR) family proteins and c-Met in two human lung cancer cell lines in vitro. However, cell lines with NDRG1/Cap43 knockdown showed markedly decreased production of the potent angiogenic factors vascular endothelial growth factor-A and interleukin-8. Cells with knockdown of NDRG1/Cap43 showed marked reduction of tumor-induced angiogenesis. Using immunohistochemistry, we examined 182 surgically resected specimens of NSCLC for expression of NDRG1/Cap43 and tumor angiogenesis. High microvessel density in the tumor was significantly associated with nuclear positivity for NDRG1/Cap43 in both adenocarcinoma (p = 0.003) and squamous cell carcinoma (p=0.041). For both adenocarcinoma (p = 0.031) and squamous cell carcinoma (p=0.034), the survival curve of patients negative for nuclear NDRG1/Cap43 expression differed significantly from that of patients who were positive.
Conclusion: Therefore, the expression of NDRG1/Cap43 may be predictive of tumor angiogenesis and poor prognosis in NSCLC.