Abstract 4627: Proximal fluid proteome profiling of human colorectal cancer tissue reveals candidate biomarkers for CRC screening

Abstract

Abstract Background: Colorectal cancer (CRC) is the second leading cause of cancer death in the Western world. Detection of CRC at an early stage of disease is associated with a much better prognosis for the patient, and is a realistic approach to reduce CRC mortality rates. Several randomised trials have shown that FOBT screening, ie detection of blood-derived haem in feces, reduces CRC mortality by ∼16%. However, it is commonly recognized that sensitivity and specificity of non-invasive CRC screening tests need to be improved, for which novel biomarkers are urgently needed. Aim: The aim of this study is to identify novel protein biomarkers that can be used for development of a blood-based or stool-based screening test for early diagnosis of CRC. Approach: Tumor “proximal fluids” are a rich source of tumor-derived proteins, comprising proteins that are either secreted, shed by membrane vesicles (exosomes), or externalized due to cell death. Fresh human colon carcinoma tissue and matched normal colon tissue samples were obtained from four patients directly following surgery. Histological evaluation indicated large variation among tumor samples in staging (I, III, and 2x IV) and type (3 adenocarcinomas, 1 mucinous tumor). Tissues were briefly rinsed and incubated in PBS at 37°C for one hour. Proximal fluids of normal and CRC tissues were collected and subjected to in-depth proteome profiling by a GeLC-MS/MS workflow. Quantitative comparisons were based on label-free spectral counting, p-values were calculated using the Mantel Haenszel test, and the single-test threshold for significance was set to p<1e-5 to withstand correction for multiple testing. Ingenuity Pathway Analysis (IPA) was used to support data interpretation. Results: A total of 2817 proteins were identified from proximal fluids of human colon carcinoma and patient-matched normal colon control tissues. Of these, 55 proteins were consistently and significantly (single test p<0.00001) more secreted by CRC samples than by controls. Data integration with a previously obtained mouse colon tumor proximal fluid proteome indicated 26 overlapping candidates, including several minichromosome maintenance MCM proteins that have been proposed in literature as markers for (stool-based) CRC screening. Conclusion & Discussion: We conclude that proximal fluid proteome profiling of human CRC tissue is a powerful strategy to discover novel candidate biomarkers for CRC screening. Despite large variation in tumor stage and type between the four samples analyzed more than 50 candidate CRC biomarkers were identified. Further validation studies are required to investigate whether these candidates are robust biomarkers for CRC screening. Acknowledgments: This research is supported by the Cancer Center Amsterdam. Note: This abstract was not presented at the AACR 101st Annual Meeting 2010 because the presenter was unable to attend. 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 4627.