Mass Spectrometry Imaging of N-Glycans Reveals Racial Discrepancies in Low Grade Prostate Tumors

Abstract

Prostate cancer is the most common cancer in men worldwide. Despite its prevalence, there is a critical knowledge gap regarding the underlining molecular events that result in higher incidence and mortality rate in Black men. Identifying molecular features that separate racial disparities is a critical step in prostate cancer research that could lead to predictive biomarkers and personalized therapy. N-linked glycosylation is a co-translational event during protein folding that modulates a myriad of cellular processes. Recently, aberrant N-linked glycosylation has been reported in prostate cancers. However, the full clinical implications of dysregulated glycosylation in prostate cancer has yet to be explored. Herein, we performed high-throughput matrix-assisted laser desorption ionization mass spectrometry analysis to characterize the N-glycan profile from tissue microarrays of over 100 patient tumors with over 10 years of follow up data. We identified several species of N-glycans that were profoundly different between low grade prostate tumors resected from White and Black patients. Further, these glycans predict opposing overall survival between White and Black patients with prostate cancer. These data suggest differential N-linked glycosylation underline the racial disparity of prostate cancer prognosis. Our study highlights the potential applications of MALDI-MSI for digital pathology and biomarker to study racial disparity of prostate cancer patients.

In situ spatial glycomic imaging of mouse and human Alzheimer's disease brains

“…Enzyme-assisted MALDI-MSI of in situ N-linked glycans has been utilized for the spatial profiling of many different cancer types, revealing unique tumor and stromal spatial differences. 61,65,66 Spatial profiling of N-linked glycans in mouse brains has been reported in several studies, [94][95][96] but a spatial definition similar to that seen in cancer specimens cannot be reached. Purified enzymes are often stored in salt solution to preserve activity, which can crystallize during dry-spray application of enzyme on FFPE tissue sections.…”

“…[60][61][62][63][64] Enzyme-assisted MALDI-MSI has been applied to an array of different tumor types with remarkable spatial resolution that allows for separation of tumor and stromal metabolic discrepancies. 61,65,66 Although spatial glycomics analysis has been reported in mouse brains, current reports do not achieve the spatial definition observed in cancer studies. 67 We hypothesized that this decreased resolution was due to high levels of charged N-linked glycans containing terminal sialic acids, which are considerably more abundant in the brain compared to other tissues.…”

“…The application of peptide‐N‐glycosidase F (PNGaseF) to FFPE tissue sections prior to matrix application and MALDI‐MSI has enabled comprehensive in situ spatial‐glycomics profiling in multiple tissue types 60–64 . Enzyme‐assisted MALDI‐MSI has been applied to an array of different tumor types with remarkable spatial resolution that allows for separation of tumor and stromal metabolic discrepancies 61,65,66 . Although spatial glycomics analysis has been reported in mouse brains, current reports do not achieve the spatial definition observed in cancer studies 67 .…”

Applications and continued evolution of glycan imaging mass spectrometry

“…An additional advantage of this tissue specimen layout is that the large sample sizes afforded by TMAs provides adequate statistical power for complex analyses of differences in N‐glycosylation between healthy and diseased tissue types (Liu et al, 2004). In multiple studies, N‐glycan imaging of tissue microarrays has demonstrated utility in the screening of large patient cohorts for N‐glycan expression differences in a variety of cancers (Conroy et al, 2020; Drake et al, 2020b; Herrera et al, 2019; Powers et al 2015; Scott et al, 2019a; West et al, 2020, 2018). Like whole‐tissue sections, N‐glycan IMS data from TMAs may be multiplexed with immunohistochemical, immunofluorescence or autofluorescence microscopy for comparison with biomarkers or other molecules of interest (McDowell et al, 2020).…”