Plasma Peptide Biomarker Discovery for Amyotrophic Lateral Sclerosis by MALDI –TOF Mass Spectrometry Profiling

Abstract

The diagnostic of Amyotrophic lateral sclerosis (ALS) remains based on clinical and neurophysiological observations. The actual delay between the onset of the symptoms and diagnosis is about 1 year, preventing early inclusion of patients into clinical trials and early care of the disease. Therefore, finding biomarkers with high sensitivity and specificity remains urgent. In our study, we looked for peptide biomarkers in plasma samples using reverse phase magnetic beads (C18 and C8) and MALDI-TOF mass spectrometry analysis. From a set of ALS patients (n=30) and healthy age-matched controls (n=30), C18- or C8-SVM-based models for ALS diagnostic were constructed on the base of the minimum of the most discriminant peaks. These two SVM-based models end up in excellent separations between the 2 groups of patients (recognition capability overall classes > 97%) and classify blinded samples (10 ALS and 10 healthy age-matched controls) with very high sensitivities and specificities (>90%). Some of these discriminant peaks have been identified by Mass Spectrometry (MS) analyses and correspond to (or are fragments of) major plasma proteins, partly linked to the blood coagulation.

Biomarker Characterization by MALDI–TOF/MS

“…Furthermore, models using C18-or C8-based magnetic beads for ALS diagnosis were constructed from a set of ALS patients and healthy age-matched controls through a classification program. Both models showed good separations between patients and control samples with high sensitivities and specificities [242].…”

“…All normalized ion peaks were subjected to statistical analysis using unsupervised PCA [242]. Two separate point clouds each corresponding to ALS patients and healthy controls were obtained.…”

Biomarkers in Human Peripheral Blood Mononuclear Cells: The State of the Art in Amyotrophic Lateral Sclerosis

“…Many other proteins are involved in ALS pathogenesis and can be used as biomarkers. Thus, mass spectrometry (MS) for proteomics analysis in ALS patients was exploited for the first time in both CSF and plasma, using matrix-assisted laser desorption ionization–time of flight and surface-enhanced laser desorption/ionization, to drive the identification of novel candidate disease biomarkers [ 128 , 129 , 130 , 131 ]. These studies opened promising pathways for biomarker investigation, but they had two limitations: CSF collections are not always well tolerated by patients, and highly abundant plasma proteins (albumin and IgGs, among others) limit the detection of the other proteins [ 44 ].…”

Disease Profiling by MALDI MS Analysis of Biofluids

“…This protocol and a slight variation of it with regard to the serum peptide extraction step (Tiss et al 2007) have been used for biomarker discovery studies for the early detection of ovarian cancer (Timms et al 2010;Timms et al 2011) and differential diagnosis of biliary tract cancer (Sandanayake et al 2014). Similar protocols have been used by other groups for diagnostic biomarker discovery in a variety of cancers (Villanueva et al 2006b;Villanueva et al 2006c;Pietrowska et al 2009) and other diseases/infections (Conraux et al 2013;Li et al 2012;Terracciano et al 2011;Teunissen et al 2011;Xiao et al 2011), for predictive and prognostic biomarker discovery (Vafadar-Isfahani et al 2010;Taguchi et al 2007), and to identify blood-borne markers of ageing (Lu et al 2012).…”