Proteomics identification of stress-induced phosphoprotein (STIP1) as a potential biomarker for human ovarian cancer

Abstract

16533 Patients with ovarian cancers are often associated with poor prognosis and limited survival rates because their cancers were not detected at earlier stages. Currently, CA125 is the most commonly used tumor marker for ovarian cancer, but it only results in 78% sensitivity, 82 to 95% specificity, and 82% positive predictive value. Therefore, discovery of new tumor markers for detecting ovarian cancer is warranted. Peripheral blood is a convenient source of tumor markers. However, screening for new tumor markers from blood is difficult because tumor markers, usually at low concentrations in blood, are easily obscured by serum abundant common proteins. Alternatively, tumor interstitial fluid (TIF) represents a rich source for secreted proteins from both cancer cells and neighboring stromal tissues, and the contents of TIF are eventually drained into blood circulation. In this study, we attempted to identify cancer-specific proteins from TIF derived from human ovarian cancer with proteomics approaches. Using statistical analysis of 596 protein spots in two-dimensional gels between the TIF of ovarian cancer and normal interstitial fluid (NIF) of normal ovaries, we identified several differentially expressed proteins, including stress-induced phosphoprotein 1 (STIP1). Specific elevations of STIP1 in TIF and ovarian cancer tissues were confirmed with Western blot analysis and immunohistochemistry, respectively. Subsequent enzyme-linked immunosorbent assay (ELISA) experiments revealed serum levels of STIP1 were significantly higher in ovarian cancer patients than in healthy controls. Receiver operating characteristics (ROC) curve analysis suggested the value of STIP1 to be comparable to CA125. These results suggest STIP1 has the potential as a biomarker for human ovarian cancer. No significant financial relationships to disclose.