Proteomic Analysis of Ovarian Cancer Proximal Fluids: Validation of Elevated Peroxiredoxin 1 in Patient Peripheral Circulation

Ebony R Hoskins,Thomas C Krivak,Brian L Hood,Mai Sun,Robert P Edwards,Thomas P Conrads,S K Batra

doi:10.1371/journal.pone.0025056

Abstract

BackgroundEpithelial ovarian cancer (EOC) is the deadliest gynecologic malignancy in the United States. Unfortunately, a validated protein biomarker-screening test to detect early stage disease from peripheral blood has not yet been developed. The present investigation assesses the ability to identify tumor relevant proteins from ovarian cancer proximal fluids, including tissue interstitial fluid (TIF) and corresponding ascites, from patients with papillary serous EOC and translates these findings to targeted blood-based immunoassays.Methodology/Principal FindingsPaired TIF and ascites collected from four papillary serous EOC patients at the time of surgery underwent immunodepletion, resolution by 1D gel electrophoresis and in-gel digestion for analysis by liquid chromatography-tandem mass spectrometry, which resulted in an aggregate identification of 569 and 171 proteins from TIF and ascites, respectively. Of these, peroxiredoxin I (PRDX1) was selected for validation in serum by ELISA and demonstrated to be present and significantly elevated (p = 0.0188) in 20 EOC patients with a mean level of 26.0 ng/mL (±9.27 SEM) as compared to 4.19 ng/mL (±2.58 SEM) from 16 patients with normal/benign ovarian pathology.Conclusions/SignificanceWe have utilized a workflow for harvesting EOC-relevant proximal biofluids, including TIF and ascites, for proteomic analysis. Among the differentially abundant proteins identified from these proximal fluids, PRDX1 was demonstrated to be present in serum and shown by ELISA to be elevated by nearly 6-fold in papillary serous EOC patients relative to normal/benign patients. Our findings demonstrate the facile ability to discover potential EOC-relevant proteins in proximal fluids and confirm their presence in peripheral blood serum. In addition, our finding of elevated levels of PRDX1 in the serum of EOC patients versus normal/benign patients warrants further evaluation as a tumor specific biomarker for EOC.

Highlights

22,220 women are diagnosed annually with epithelial ovarian cancer (EOC) and over 13,000 succumb to this disease [1]
A greater representation of the proteome is apparent in the tissue interstitial fluid (TIF) sample due to the lower overall contribution of human serum albumin (HSA) to the total protein content
Presentation with abdominal fullness, early satiety, a pelvic mass and ascites is typical for women with Epithelial ovarian cancer (EOC), these symptoms often present only when the disease is advanced in stage

Summary

Introduction

22,220 women are diagnosed annually with epithelial ovarian cancer (EOC) and over 13,000 succumb to this disease [1]. Women with EOC have a 5-year survival rate of 18– 34%, where the poor prognosis is primarily due to the fact that the majority of patients present with advanced stage disease [2]. While immunodetection of tumor-associated antigens has contributed to the knowledge of the natural history of the disease, their measures have yet to consistently identify early stage EOC. A validated protein biomarker-screening test to detect early stage disease from peripheral blood has not yet been developed. The present investigation assesses the ability to identify tumor relevant proteins from ovarian cancer proximal fluids, including tissue interstitial fluid (TIF) and corresponding ascites, from patients with papillary serous EOC and translates these findings to targeted blood-based immunoassays

Methods

Results

Conclusion