Abstract 511: Characterization of humoral response profiles of ovarian cancer patients as diagnostic biomarkers

Abstract

Abstract Ovarian cancer is the 5th leading cause of cancer death among women and is the leading cause of death among gynecologic malignancies as a result of limitations in early diagnosis. It is associated with the induction of humoral immunity, characterized by the generation of IgG against a wide range of tumor-associated antigens. Although the role of circulating tumor-reactive IgG is unclear, it has been demonstrated to correlate with poor prognosis and survival. The use of tumor-reactive IgG as a potential diagnostic and/or prognostic tool has been limited since most studies have identified components with shared expression in non-neoplastic tissue and failed to define targets exhibiting ubiquitous expression in ovarian cancers. A number of these limitations result from the use of recombinant proteins (translated in non-mammalian cells) as targets to define immunoreactivity. The power in utilizing the autologous humoral response is its ability to define alterations which might lead to the altered appearance or aberrant association of antigen with other cellular components, thereby resulting in the induction of humoral responses. We therefore hypothesize that the ovarian patient humoral response to specific tumor antigens can serve as diagnostic biomarkers of ovarian cancer. To investigate patients’ humoral response to “natural” tumor antigens, ovarian tumor cell lysates and tumor-derived exosomes were separated into antigenic proteins by first dimension isoelectric focusing via an immobilized pH gradient and/or rotofor fractionation. Reactive proteins were further separated by second dimension SDS-PAGE, followed by western immunoblotting using autologous or heterologous patient sera. Circulating tumor-reactive IgG was found to recognize shared (MW 37-75 kD, pI 3.0-5.5) and distinct (MWexo ∼50 kD, pI 9.0-10.5; MWlys∼15 kD, pI 4.3-6.5) ovarian tumor cell proteins. Recognition of these antigenic proteins was not observed using antibodies derived from normal control patients. Collectively, our data supports that the circulating IgG produced in the ovarian cancer humoral response recognizes specific tumor antigens (many of which are shared among cancer patients) and will thus have utility in diagnosing these patients. Further identification of these antigenic proteins by mass spectrometry will produce specific diagnostic targets and may provide insights on common driver mechanisms in ovarian cancer. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 511. doi:1538-7445.AM2012-511