Identification of candidate circulating glucocorticoid response biomarkers in humans using a proteomic approach

Context
Glucocorticoids used in pharmacological doses for the treatment of a variety of medical conditions, and endogenous glucocorticoid excess – Cushing’s syndrome, may result in several adverse effects, but currently there is no clinically useful biomarker of glucocorticoid activity.
Objective
To identify glucocorticoid-responsive proteins potentially measurable in human serum.
Setting and Design
A three-phase protein biomarker discovery strategy was used. Proteomic biomarker discovery and qualification was conducted on the secretome of ex vivo-stimulated peripheral blood mononuclear cells (PBMC) isolated from 6 volunteers, incubated ± dexamethasone 100 ng/mL for 4h and 24h. Untargeted proteomics with label-free quantification (LFQ) was conducted to discover candidate proteins which were quantified using targeted proteomics by a custom multiple reaction monitoring mass spectrometry (MRM-MS) assay. Five proteins were selected for serum measurement by immunoassay in 20 healthy volunteers, with blood drawn at baseline and 12h after 4 mg oral dexamethasone.