Serum Peptidome Profiling Revealed Platelet Factor 4 as a Potential Discriminating Peptide Associated with Pancreatic Cancer

Abstract

Purpose: Mass spectrometry-based serum peptidome profiling is a promising tool to identify novel disease-associated biomarkers, but is limited by preanalytic factors and the intricacies of complex data processing. Therefore, we investigated whether standardized sample protocols and new bioinformatic tools combined with external data validation improve the validity of peptidome profiling for the discovery of pancreatic cancerassociated serum markers. Experimental Design: For the discovery study, two sets of sera from patients with pancreatic cancer (n = 40) and healthy controls (n = 40) were obtained from two different clinical centers. For external data validation, we collected an independent set of samples from patients (n = 20) and healthy controls (n = 20). Magnetic beads with different surface functionalities were used for peptidome fractionation followed by matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry (MS). Data evaluation was carried out by comparing two different bioinformatic strategies. Following proteome database search, the matching candidate peptide was verified by MALDI-TOF MS after specific antibody-based immunoaffinity chromatography and independently confirmed by an ELISA assay. Results: Two significant peaks (m/z 3884; 5959) achieved a sensitivity of 86.3% and a specificity of 97.6% for the discrimination of patients and healthy controls in the external validation set. Adding peak m/z 3884 to conventional clinical tumor markers (CA 19-9 and CEA) improved sensitivity and specificity, as shown by receiver operator characteristics curve analysis (AUROC combined = 1.00). Mass spectrometry-based m/z 3884 peak identification and following immunologic quantitation revealed platelet factor 4 as the corresponding peptide. Conclusions: MALDI-TOF MS-based serum peptidome profiling allowed the discovery and validation of platelet factor 4 as a new discriminating marker in pancreatic cancer.

Identification of Serum Biomarker Signatures Associated with Pancreatic Cancer

“…Despite major efforts, molecular fingerprints associated with PDACs from, in particular, crude, nonfractionated serum and plasma remain a challenge (3,(9)(10)(11)(12). Among the number of mainly single biomarkers that have been outlined so far, including, for example, C-reactive protein (CRP), CA 242, GDF-15, haptoglobin, M2-pyruvate kinase, serum amyloid A, platelet factor 4, and IGF-binding protein (IGFBP)-1, none have proven to be clinically superior to CA 19-9, the most used biomarker today (3,10,11,13).…”

Biomarkers Screening Between Preoperative and Postoperative Patients in Pancreatic Cancer

“…Further, peak m/z 3884 adds information to the conventional serum tumor marker panels consisting of CA 19-9 and CEA, and thereby strongly improves the sensitivity and specificity of the laboratory tumor marker testing in patients suffering from pancreatic cancer. They subsequently identified a MALDI-MS/MS spectrum of 3884 Da corresponding to the platelet factor 4 (Fiedler et al, 2009). In 2011, Liu et al Identified four mass peaks that correlated with colorectal cancer (CRC), with peaks corresponding to m /z values of 2870.7 and 3084 showing down-regulation and peaks corresponding to m /z values of 9180.5 and 13748.8 showing up-regulation, by comparing spectra generated from colorectal cancer patients serum samples between 144 CRC patients and 120 healthy controls (Liu et al, 2011).…”

Biomarker – vom Sein und Wesen

“…"Pattern", also Muster aus unterschiedlichen Konzentrationen verschiedener Moleküle, die zusammen in einem analytischen Lauf gemessen wurden und für die Erstellung eines Pattern noch nicht einmal identifiziert werden mussten. Diese Pattern erreichten für sich allein jedoch selten die diagnostische Trennschärfe der schon etablierten Tumormarker, so dass man sie zur Erzeugung eines diagnostischen Mehrwerts mit den konventionellen Markern kombinierte [2]. Eine genauere Analyse der in den Pattern zusammengefassten Analyten ließ jedoch bald den Schluss aufkommen, dass es sich bei den Analyten nicht nur um tumorspezifische Antigene, sondern häufig um Intermediate tumorspezifischer (proteolytischer) Aktivität handelte, die z.B.…”