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

Abstract

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.