[Abnormal expression of angiopoietin-2 associated with invasion, metastasis and prognosis of lung cancer].

Objective To investigate the relationship between abnormal angiopoietin-2 (Ang-2) expression and invasion/metastasis of lung cancer. Methods Totally 122 cases of postoperative primary lung cancer tissues and their paracancerous tissues from Jan. 2009 to Dec. 2010 were collected from Affiliated Hospital of Nantong University and Ang-2 expression was analyzed by immunohistochemistry. At the cellular level, the protein and mRNA levels of Ang-2 in lung epithelial cell line Beas-2B and four lung cancer cell lines (SPCA-1, NCI-1650, A549 and NCI-H1975) were observed. The most effective Ang-2-shRNA for Ang-2 transcription was screened and transfected into A 549 lung cancer cells. The Ang-2 expression, Ang-2 gene transcription, cell proliferation, invasion/metastasis, and epithelial-mesenchymal transition (EMT) abilities of lung cancer cells were analyzed by Western blotting, fluorescent quantitative reverse transcriptase PCR, Cell Counting Kit-8 assay, and Transwell cell models for exploring the relationship between Ang-2 expression and invasion/metastasis of lung cancer. Results The higher Ang-2 expression levels in lung cancerous tissues were closely related to tumor diameter (P=0.008), differentiating degree (P=0.033), TNM stage (P=0.025) and 5-year survival rate (P<0.001). According to the Kaplan-Meier survival curves, the 5-year survival rate of patients with higher expression levels of Ang-2 (16.1%) was significantly poorer than that of patients with lower Ang-2 (80.0%, P<0.001). Significant difference of 5-year survival rate was found in patients with different Ang-2 levels at TNM stage Ⅰ(P<0.001), but not at stage Ⅱ, Ⅲ and Ⅳ. Among Beas-2B and four lung cancer cell lines, the protein and mRNA levels of Ang-2 in A549 cells were the highest. After Ang-2-shRNA-1 plasmid successfully transfected into A549 cells, cell proliferation rate was significantly lower than that in the shRNA-negative or blank group at a time-dependent manner. The significant decrease of the invasion, migration and EMT abilities were also found in A549 cells after transfection of Ang-2 shRNA. Conclusion Abnormal expression of Ang-2 is closely related to invasion, migration and prognosis of lung cancer, and interfering the activation of Ang-2 would be a novel molecular-targeted therapy for lung cancer. Key words: Lung neoplasms; Angiopoietin-2; RNA interference; Prognosis