Use of a Combination of Approaches to Identify and Validate Relevant Tumor-Associated Antigens and Their Corresponding Autoantibodies in Ovarian Cancer Patients

Abstract

Purpose: Novel biomarkers are urgently needed to increase the sensitivity of CA125 for the early detection of ovarian cancer. Indeed, it has been shown that as much as 20% of early-stage patients do not express significant levels of this biomarker.Therefore, the possibility of using autoantibodies directed against tumor-associated antigens as putative cancer markers is being more examined. Indeed, many autoantibodies have recently been shown to correlate with cancer patient prognosis or to be suitable for detection of the disease. Experimental Design: In this study, we have used a new approach involving the use of proteomics, immunology, and ELISA methods to identify relevant autoantibodies in the plasma of ovarian cancer patients. To do so, we developed an innovative technique called two-dimensional differential gel electrophoresis analysis of immunoprecipitated tumor antigens.Results: This strategy allowed us to successfully identify novel circulating autoantibodies directed against the S100A7 protein in the plasma of ovarian cancer patients. Further real-time reverse transcription-PCR and immunohistochemical studies confirmed that the S100A7 mRNA and protein were highly expressed in ovarian tumors but absent in normal and benign tissues. Moreover, a preliminary study involving 138 patients confirmed that the plasma levels of anti-S100A7 antibodies are significantly elevated in early-and late-stage ovarian cancer patients compared with healthy controls and with patients with benign gynecologic diseases. Conclusions: This shows that our approach is a valuable tool to successfully identify autoantibodies and tumor-associated antigens in cancer patients and that future research assessing their putative clinical usefulness would be worthwhile.Ovarian cancer is the leading cause of gynecologic cancer death worldwide. In the United States, it is the eighth most common cancer among women and the fifth most common cause of cancer death, with about 20,180 new cases and 15,310 deaths expected in 2006 (1). However, the relatively asymptomatic nature of early-stage disease and the lack of adequate screening tests have resulted in the majority of cases presenting with a late-stage disease (2). Currently, clinicians rely on a combination of serum CA125 levels and imaging to diagnose ovarian cancer in suspected patients and monitor treatment response. However, due to its low sensitivity, the currently used test to quantify the CA125 serum marker is not adequate for early detection (3). Indeed, up to 20% of ovarian cancers fail to express significant levels of the maker (4). Thus, there is an urgent need for new ovarian cancer biomarkers that could improve the sensitivity of ovarian cancer early detection.The hunt for cancer biomarkers in the serum/plasma of patients with cancer is based on the observation that some lowmolecular weight proteins that reflect the pathologic state of the patients are shed into the bloodstream (5). Therefore, because our immune system constantly surveys the body for ''nonself'' antigens,...

Identification of salt-inducible kinase 3 as a novel tumor antigen associated with tumorigenesis of ovarian cancer

“…The responses are frequently mounted against tumor cells expressing altered or abnormally high levels of normal self-antigens with inappropriate timing (Brewer et al, 2009), cellular compartmentalization (Chang et al, 2006) or tissue expression (Old, 2008) that result in increased immunogenicity. Therefore, high levels of tumor-associated autoantibodies can be also observed in some cancer patients throughout their disease progressions (Gagnon et al, 2008), and some of them are associated with their disease outcomes (Reuschenbach et al, 2009). Currently, over 100 immunogenic TAAs have been reported in patients with a variety of cancers; however, few of them are associated with ovarian cancer, including CA125 (Reuschenbach et al, 2009;Taylor et al, 2009).…”

The Role of Circulating Antigen and Autoantibody in Diagnosing Ovarian Cancer

“…We therefore suggest more study with larger cohort of subjects focusing detection of early ovarian cancer based on the relation between the autoantigen and its autoantibody. The immune system recognizes the TAAs as foreign and induces a humoral immune response very early in the disease process [59]. Although measurement of autoantibodies to a single TAA is possible, the low sensitivity and specificity renders single autoantibody measurements of little value for screening and early detection of cancer.…”

Étude de la réaction immunitaire humorale aux cancers par des approches protéomiques

“…Il est néanmoins possible d'enrichir spécifiquement les antigènes tumoraux faiblement exprimés par des approches d'immunoprécipitation [27] et d'utiliser des molécules fluorescentes plus sensibles que les méthodes de coloration standard [28]. Cette combinaison a été utilisée récemment avec succès pour identifier des AAT dans le cancer de l'ovaire [29]. Le SERPA demeure donc une méthode très robuste pour la mise en évidence d'une réponse immune de type humoral dans les cancers, d'autant que de nombreuses améliorations technologiques ont été introduites ces dernières années, notamment dans la robotisation des techniques de 2-DE ou l'amélioration de la sensibilité des spectromètres de masse permettant l'identification des antigènes.…”