Applications of multiple reaction monitoring targeted proteomics assays in human plasma

ABSTRACT

Introduction: Multiple (or selected) reaction monitoring-mass spectrometry (MRM/SRM) is a targeted proteomic method that can be used for relative and absolute quantification. Multiple reports exist supporting the potential of the approach in proteomic biomarker validation.

Areas covered: To get an overview of the applications of MRM in protein quantification in plasma, a search in MedLine/PubMed was performed using the keywords: ‘MRM/SRM plasma proteomic/proteomics/proteome’. The retrieved studies were further filtered to focus on disease biomarkers and the main results are summarized.

Expert opinion: MRM is increasingly employed for the quantification of both well-established but also newly discovered putative biomarkers and occasionally their post-translationally modified forms in plasma. Fractionation is regularly required for the detection of low abundance proteins. Standardized procedures to facilitate assay establishment and marker quantification have been proposed and, in few cases, implemented. Nevertheless, in most cases, absolute quantification is not performed. To advance, multiple technical issues including the regular use of standard labeled peptides and appropriate quality controls to monitor assay performance should be considered. Additionally, clinical aspects involving careful study design to address biomarker clinical use should also be considered.

KEYWORDS:

• Biomarkers
• drugs
• MRM
• plasma
• quantification
• SRM

Article Highlights

• MRM targeted proteomics analysis is used for verification/validation of proteomic biomarker findings in plasma.

• Multiple MRM studies in plasma have been conducted the past 6 years, quantifying both well established and exploratory biomarkers for a variety of diseases.

• A relatively small number of studies involves analysis of >100 clinical samples and the use of labeled standard peptides for absolute quantification.

• Applications in the quantification of post-translationally modified proteins (glycosylation, hydroxylation) are ever increasing.

• The multiplexing and absolute quantification potential of MRM for clinical applications has not been fully explored yet, linked to technical and clinical issues; these relate in part to the need for protein enrichment, and adopt on a regular basis step-wise workflow for transition selection, assay monitoring and ultimately quantification based on standard curves using properly sized cohorts for the targeted context of biomarker use.

Declaration of interest

The authors have no other relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript apart from those disclosed.

Reviewers Disclosure

Peer reviewers on this manuscript have no relevant financial relationships or otherwise to disclose.

Supplementary material

Supplemental data can be accessed here.

Additional information

Funding

This work is in part supported by the Greek GSRT (grant mELISA-CKD, Τ1ΕΔΚ-03551; EPAnEK Operational Programme)