Angiopoietin-2 (Ang-2) is a useful serum tumor marker for liver cancer in the Chinese population

Background: We estimated the diagnostic and prognostic value of serum angiopoietin-2 (Ang-2) in liver cancer patients. Methods: Tissue Ang-2 was measured using immunohistochemistry (IHC). Cell localization of Ang-2 was tested using immunofluorescence (IF). Cell viability and apoptosis were evaluated using MTT and caspase3/7 assays, respectively. Colony-formation was measured using a soft agar assay. Serum Ang-2 was examined using enzyme linked immunosorbent assay (ELISA) and Western blotting. Results: Ang-2 was up-regulated in liver cancer compared to the levels in normal tissues. Serum Ang-2 concentrations were much higher in liver cancer patients than in healthy individuals and those with chronic liver disease (CLD). Inhibitions of Ang-2 using specific shRNA decreased cell proliferation. Serum Ang-2 decreased significantly after surgery. Serum Ang-2 was positively correlated with serum alpha-fetoprotein (AFP; R = 0.375, P = 0.005). Receiver operating characteristic (ROC) curves suggested that serum Ang-2 could be used with relatively high sensitivity and specificity in differentiating liver cancer patients from CLD patients or healthy controls, with corresponding AUC values of 0.742 and 0.924, respectively. Serum Ang-2 was negatively correlated with overall survival. Subgroup analysis also showed that Ang-2 retained its prognostic value in overall survival prediction in different risk subgroups. Conclusion: Serum Ang-2 may be a useful tumor marker in predicting liver cancer prognosis.