Angiopoietin-Like Protein 2 Acts as a Novel Biomarker for Diagnosis and Prognosis in Patients with Esophageal Cancer

Angiopoietin-like protein 2 (ANGPTL2) mediates chronic inflammation. Tumor cell-derived ANGPTL2 promotes tumor invasion and angiogenesis. Overexpression of ANGPTL2 in tumor cells is associated with tumor progression and has been recognized in lung, breast, colon, and gastric cancer. However, to our knowledge the functional and clinical significance of ANGPTL2 expression has not been investigated in patients with esophageal cancer (EC). First, in vitro assays were performed for functional analysis of ANGPTL2 using small interfering RNA. Next, ANGPTL2 expression in EC tissues (n = 71) was evaluated by immunohistochemistry (IHC in patients with EC (n = 71). Finally, serum ANGPLT2 levels from patients with EC (n = 71) and healthy controls (n = 35) were evaluated using enzyme-linked immunosorbent assay. Knockdown of ANGPTL2 expression decreased the proliferative, invasive, and migration capacity in EC cell lines. ANGPTL2 expression in EC tissues was significantly elevated in patients with a high T stage, squamous cell carcinoma, and high TNM stage. Patients with high ANGPTL2 expression had significantly poorer overall and disease-free survival than those with low expression. Furthermore, high ANGPTL2 expression in EC tissues was an independent predictive marker for a poor prognosis. On the other hand, the serum ANGPTL2 level in patients with EC was significantly higher than that in healthy controls, and allowed for highly accurate discrimination between patients with and without EC. However, no significant association between serum ANGPTL2 levels and clinicopathological findings was observed in patients with EC. We have demonstrated novel evidence for the clinical significance of ANGPTL2 as a biomarker in patients with EC.