Abstract
Detection of autoantibodies against tumor‐associated antigens (TAA) has recently been shown to be a powerful tool for early detection of various cancers. The aim of this study was to investigate the possibility of using autoantibodies against TAA as novel biomarkers by a proteomics‐based approach in patients with ovarian cancer. We used two‐dimensional differential gel electrophoresis analysis of immuno‐precipitated tumor antigens (2D‐DITA) to compare the levels of autoandibodies in pretreatment and posttreatment sera of patients with ovarian cancers. The identified autoantibodies were validated by SYBR Green real‐time polymerase chain reaction (PCR) and immunohistochemistry (IHC). We further evaluated the level of autoantibody in sera of 68 ovarian cancer patients by an enzyme‐linked immunosorbent assay (ELISA). The autoantibody directed against stress‐induced phosphoprotein‐1 (STIP‐1) emerged as a novel biomarker candidate for ovarian cancer. SYBR Green PCR and IHC confirmed that the STIP‐1 mRNA and protein expression levels were significantly up‐regulated in ovarian cancers compared with normal and benign tumors (P = 0.003 and P < 0.001, respectively). A preliminary ELISA study showed that the serum levels of anti‐STIP‐1 autoantibodies were significantly elevated in ovarian cancer patients compared with healthy controls (P = 0.03). The results suggest that 2D‐DITA is a useful tool to detect autoantibodies and that STIP‐1 is a potential biomarker candidate for ovarian cancers. © 2010 Wiley‐Liss, Inc.