Investigating Patterns of Immune Interaction in Ovarian Cancer: Probing the O-glycoproteome by the Macrophage Galactose-Like C-Type Lectin (MGL)

Abstract

Glycosylation, the posttranslational linking of sugar molecules to proteins, is notoriously altered during tumor transformation. More specifically in carcinomas, GalNAc-type O-glycosylation, is characterized by biosynthetically immature truncated glycans present on the cancer cell surface, which profoundly impact anti-tumor immune recognition. The tumor-associated glycan pattern may thus be regarded as a biomarker of immune modulation. In epithelial ovarian cancer (EOC) there is a particular lack of specific biomarkers and molecular targets to aid early diagnosis and develop novel therapeutic interventions. The aim of this study was to investigate the ovarian cancer O-glycoproteome and identify tumor-associated glycoproteins relevant in tumor–dendritic cell (DC) interactions, mediated by macrophage galactose-like C type lectin (MGL), which recognizes the tumor-associated Tn O-glycan. Lectin weak affinity chromatography (LWAC) was employed to probe the O-glycopeptidome by MGL and Vicia villosa agglutinin (VVA) lectin using glycoengineered ovarian cancer cell lines and ovarian cancer tissues as input material. Biochemical and bioinformatics analysis gave information on the glycan arrangement recognized by MGL in tumor cells. The potential MGL binders identified were located, as expected, at the cell membrane, but also within the intracellular compartment and the matrisome, suggesting that MGL in vivo may play a complex role in sensing microenvironmental cues. The tumor glycoproteins binders for MGL may become relevant to characterize the interaction between the immune system and tumor progression and contribute to the design of glycan targeting-based strategies for EOC immunotherapeutic interventions.

Towards structure-focused glycoproteomics

“…Lectins that recognise other N -glycan structural features include Phaseolus vulgaris erythroagglutinin (PHA-E) and Calystegia sepium lectin (Calsepa) that bind bisecting β1,4-GlcNAc structures, Maackia amurensis lectin (MAL) that recognises α2,3-sialic acid residues and Sambucus nigra agglutinin (SNA) and Sambucus sieboldiana agglutinin (SSA) that both bind α2,6-sialic acid residues [ 140–142 ]. Furthermore, the recombinant human macrophage galactose-like C-type lectin (MGL)-Fc chimeric protein was recently used to enrich Tn glycopeptides from ovarian cancer cells and tissues [ 143 ]. Finally, engineered lectins displaying enhanced or tailored recognition of particular glycan epitopes including, amongst others, core fucose recognised by the recombinant N224Q mutant of the Aleuria aurantia lectin (AAL), and O -GlcNAc recognised by the Agrocybe aegerita lectin (AANL) mutant AANL6 have the potential of expanding the enrichment tool box for structure-focused glycoproteomics [ 144–149 ].…”

Glycoproteins Presenting Galactose and N-Acetylgalactosamine in Human Seminal Plasma as Potential Players Involved in Immune Modulation in the Fertilization Process

“…Galectins recognize β-galactosides and great interest on their impact on tumor progression has arised in the recent years [ 37 , 42 ]. Macrophage galactose binding lectin (MGL), present on the surface of macrophages and the other cells of immune system, is specific for GalNAc and involved in regulation of the immune response [ 53 , 54 , 55 , 56 , 57 , 58 ].…”

Glycan-Lectin Interactions as Novel Immunosuppression Drivers in Glioblastoma

“…These results support the hypothesis that the MGL-Tn axis may contribute to the immunosuppressive network in GB. It is interesting to recall that the Tn-MGL axis has been validated as a therapeutic target in an ovarian cancer mouse model by means of glycomimetic peptides [ 116 , 117 ].…”