Legumain: a biomarker for diagnosis and prognosis of human ovarian cancer

Legumain is a member of the asparaginyl endopeptidase family that is over‐expressed in response to hypoxic stress on mammary adenocarcinoma, colorectal cancer, proliferating endothelial cells, and tumor‐associated macrophages (TAMs). Here, we demonstrate that elevated expression of legumain in ovarian cancer by a proteomic approach using isobaric tags for relative and absolute quantification (iTRAQ) followed by liquid chromatography–mass spectrometry (LC–MS/MS). To investigate the relationship between legumain expression and ovarian cancer development, we tested legumain expression in malignant human ovarian tumors (n = 60), borderline ovarian tumors (n = 20), benign ovarian tumors (n = 20), and normal ovary samples (n = 20) using immunohistochemical assay (IHC). A correlation between legumain expression, and clinocopathologic and biological variables was also established. Importantly, increased legumain expression was validated by real‐time PCR and Western blots, correlated positively with an increased malignancy of ovarian tumors (P < 0.01). In fact, patients with strong legumain expression had a worse prognosis (P = 0.03). In addition, results of in vitro experiments revealed that over‐expression of legumain correlates with increased cell migration and invasion of ovarian cancer cells. Although legumain's functional role and clinical utility remain to be established, our results indicated that a sensitive assay for early expression of legumain may serve as both a potential biomarker and a molecular target for treatment of ovarian cancer. J. Cell. Biochem. 113: 2679–2686, 2012. © 2012 Wiley Periodicals, Inc.