Abstract 3989: Ovarian cancer protein biomarker identification from the tumor tissue microenvironment

Abstract

Abstract Objective: In order to circumvent the challenges associated with serum-based biomarker discovery for ovarian cancer screening development, we utilized a novel sampling strategy to harvest shed and secreted proteins from tissue interstitial fluid (TIF) from the ovarian tumor tissue microenvironment. The motivating hypothesis is TIF, the proximal fluid that bathes ovarian cancer cells and stroma, is rich in cancer-specific proteins that are readily identifiable by mass spectrometry (MS)-based proteomics. Materials: Ovarian tumor tissue and ascites were collected within 30 minutes of removal from the patient, at the time of debulking surgery. Samples used in the analysis were from four chemotherapy naïve patients with pathology-proven papillary serous ovarian cancer. We implemented a standardized sampling strategy, involving incubation of tumor tissue in saline for 1 hour immediately following resection resulting in protein rich TIF. The TIF and ascites samples were analyzed by MS for protein sequence identification and relative quantitation. Results: Over 2700 total proteins were identified in TIF across all patient samples, while ascitic fluid contained over 2000 proteins across all patient samples. 13 proteins were identified in all TIF samples that were 3-fold or greater in quantity compared to ascitic fluid samples. For comparison, 14 proteins that were 3-fold greater in ascitic fluid compared to TIF, was also identified. Interestingly, these select proteins from two microenvironments had contrasting function and location. TIF samples contained largely intracellular proteins, which are secreted and/or shed while ascitic fluid sample contained extracellular proteins, similar to serum, thus confirming the utility of TIF representing the tumor microenvironment, see figure. The results demonstrate the ability to readily identify hundreds of proteins in TIF, which are at higher abundance compared to those, identified in ascitic fluid from the same patients. Conclusions: We developed a standard workflow for the discovery of candidate biomarkers from the ovarian cancer tissue microenvironment. The TIF proteome contains more lower abundant and cancer specific proteins compared to ascitic fluid. We are prospectively validating candidate biomarkers from this microenvironment in patient serum by western blot analysis and immunohistochemistry. Ultimately we will expand our standard protocol to a cohort of patients with likely early stage cancers in order to translate to a serum-based screening test. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 3989.