Plasma orosomucoid 2 as a potential risk marker of cholangiocarcinoma

BACKGROUND: Cholangiocarcinoma (CCA), a malignant tumor of the biliary epithelium, is a tumor with an ineffective diagnosis and poor prognosis. We have previously identified an overexpression of orosomucoid 2 (ORM2) along with CCA development in hamsters using a proteomics technique. OBJECTIVE: To evaluate plasma ORM2 as a candidate risk biomarker for CCA in humans. METHODS: Overexpression of ORM2 in CCA patients was assessed by western blotting and immunohistochemistry. The diagnostic efficacy of ORM2 was investigated in the plasma of patients with hepatobiliary diseases - including 46 cholangitis patients and 70 CCA patients - compared with 20 healthy individuals, using enzyme-linked immunosorbent assay (ELISA). RESULTS: Overexpression of ORM2 was observed in the cytoplasm of bile duct tumor cells and in the adjacent normal hepatocytes at a much higher intensity than in normal bile duct cells. Western blot analysis revealed that its expression was significantly higher in the plasma of CCA patients compared with that of healthy individuals (P < 0.01). ELISA showed that plasma ORM2 levels were significantly elevated in CCA and cholangitis groups compared with healthy individuals (P < 0.0001). The sensitivity and specificity of ORM2 in distinguishing CCA patients from healthy patients were 92.86% and 73.68%, respectively. CONCLUSIONS: Plasma ORM2 could serve as a new risk marker for CCA.