Development and validation of a Luminex assay for detection of a predictive biomarker for PROSTVAC-VF therapy

<div><p>Cancer therapies can provide substantially improved survival in some patients while other seemingly similar patients receive little or no benefit. Strategies to identify patients likely to respond well to a given therapy could significantly improve health care outcomes by maximizing clinical benefits while reducing toxicities and adverse effects. Using a glycan microarray assay, we recently reported that pretreatment serum levels of IgM specific to blood group A trisaccharide (BG-A_tri) correlate positively with overall survival of cancer patients on PROSTVAC-VF therapy. The results suggested anti-BG-A_tri IgM measured prior to treatment could serve as a biomarker for identifying patients likely to benefit from PROSTVAC-VF. For continued development and clinical application of serum IgM specific to BG-A_tri as a predictive biomarker, a clinical assay was needed. In this study, we developed and validated a Luminex-based clinical assay for measuring serum IgM specific to BG-A_tri. IgM levels were measured with the Luminex assay and compared to levels measured using the microarray for 126 healthy individuals and 77 prostate cancer patients. This assay provided reproducible and consistent results with low %CVs, and tolerance ranges were established for the assay. IgM levels measured using the Luminex assay were found to be highly correlated to the microarray results with R values of 0.93–0.95. This assay is a Laboratory Developed Test (LDT) and is suitable for evaluating thousands of serum samples in CLIA certified laboratories that have validated the assay. In addition, the study demonstrates that discoveries made using neoglycoprotein-based microarrays can be readily migrated to a clinical assay.</p></div

Analytical validation summary.

<p>For the analytical validation, for each sample dilution, we ran eight plates with twelve replicates on each plate (n = 96).</p

Assay specificity^a.

<p>Assay specificity<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0182739#t002fn001" target="_blank">^a</a>.</p

Overview of neoglycoproteins and assay formats.

<p>Glycans or glycopeptides are covalently coupled to albumin to produce neoglycoproteins, which are then printed onto a microarray surface and used to detect IgM to BG-A_tri. Neoglycoproteins immobilized on Luminex microspheres mimic glycan presentation on the microarray surface.</p

Comparison of BG-A_tri signals measured using the Luminex assay and the microarray assay.

<p>Comparison of BG-A_tri signals measured using the Luminex assay and the microarray assay.</p

Selection of sample dilution.^a

<p>Selection of sample dilution.<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0182739#t001fn001" target="_blank">^a</a></p