Glycans in tissues are structurally diverse and usually include a large number of isomers that cannot be easily distinguished by mass spectrometry (MS). To address this issue, we developed a combined method that can efficiently separate and identify glycan isomers. First, we separated 2-aminopyridine (PA)-derivatized N-glycans from chicken colon by reversed-phase liquid chromatography (LC) and directly analyzed them by electrospray ionization (ESI)-MS and MS/MS to obtain an overview of the structural features of tissue glycans. Next, we deduced the structures of isomers based on their elution positions, full MS, and MS/MS data, before or after digestions with several exoglycosidases. In this method, the elution position differed greatly depending on the core structure and branching pattern, allowing multiantennary N-glycan structures to be easily distinguished. To further determine linkages of branch sequences, we modified PA-N-glycans with sialic acid linkage-specific alkylamidation and/or permethylation, and analyzed the products by LC–MS and multistage MS. We determined the relative abundances of core structures, branching patterns, and branch sequences of N-glycans from chicken colon, and confirmed presence of characteristic branch sequences such as Lex, sialyl Lex, sulfated LacNAc, LacNAc repeat, and LacdiNAc. The results demonstrated that our method is useful for comparing N-glycomes among various tissue samples.

Zebrafish is a model organism suitable for studying vertebrate development. We analyzed the N-glycan structures of zebrafish embryos and their alterations during zebrafish embryogenesis to obtain basic data for studying the roles of N-glycosylation. Multiple modes of high-performance liquid chromatography and multistage mass spectrometry were used for structural analysis of N-glycans. The N-glycans from deyolked embryos at 36 hours postfertilization, a mid-pharyngula stage, contained relatively higher amounts of complex- and hybrid-type glycans with LacNAc (Galβ1-4GlcNAc) and/or sialyl LacNAc without additional β1,4-Gal, which are commonly found in mammalian tissues, as well as abundant oligomannose-type glycans. Some of the complex- and hybrid-type glycans possessed various extended LacNAc structures, such as Galβ1-4LacNAc, LacNAc-repeat or unique (+/- dHex)-GalNAcα1-GlcNAcβ1-LacNAc. In contrast, the yolk of the embryo contains predominant oligomannose-type glycans and complex-type glycans with Galβ1-4(Siaα2-3)Galβ1-4(Fucα1-3)GlcNAc antennae. N-Glycan profiles obtained from deyolked embryos at different stages showed stage-dependent variation of complex- and hybrid-type glycans. At gastrula and early segmentation stages, complex- and hybrid-type glycans were minor components, and their antenna structures were mainly sialyl LacdiNAc (Siaα2-6GalNAcβ1-4GlcNAc). From the mid-segmentation to pharyngula stages, those with LacNAc and/or α2,6-sialyl LacNAc antenna structures increased remarkably, and those with α2,3-sialyl LacNAc antenna, core α1,6-Fuc and bisecting GlcNAc modifications increased gradually. These results suggest the presence of mechanisms for regulating the antenna structures of complex/hybrid N-glycan biosynthesis in the phylotypic stage of vertebrate development.

β-1,4-N-Acetyl-Galactosaminyltransferase 1 (B4GALNT1) encodes the key enzyme B4GALNT1 to generate gangliosides GM2/GD2. GM2/GD2 gangliosides are surface glycolipids mainly found on brain neurons as well as peripheral nerves and skin melanocytes and are reported to exacerbate the malignant potential of melanomas. In order to elucidate the mechanism, we performed functional analyses of B4GALNT1-overexpressing cells. We analyzed ganglioside pattern on four melanoma and two neuroblastoma cell lines by high performance liquid chromatography (HPLC). We overexpressed B4GALNT1 in GM2/GD2-negative human melanoma cell line (SH4) and confirmed production of GM2/GD2 by HPLC. They showed higher anchorage independence growth (AIG) in colony formation assay, and exhibited augmented motility. In vitro, cell proliferation was not affected by GM2/GD2 expression. In vivo, GM2/GD2-positive SH4 clones showed significantly higher tumorigenesis in NOD/ Scid/IL2Rγ-null mice, and immunostaining of mouse CD31 revealed that GM2/GD2 induced remarkable angiogenesis. No differences were seen in melanoma stem cell and Epithelial-Mesenchymal Transition markers between GM2/GD2-positive and -negative SH4 cells. We therefore concluded that B4GALNT1, and consequently GM2/GD2, enhanced tumorigenesis via induction of angiogenesis, AIG, and cell motility. RNA-Seq suggested periostin as a potential key factor for angiogenesis and AIG. These findings may lead to development of novel therapy for refractory melanoma.abundant in the nervous system, especially brain neurons 14 . They also exist in peripheral nerves and skin melanocytes 15,16 . These molecules are reported to have important biological functions, such as intercellular communication, cell cycling, cell growth, adhesion, differentiation, and cell motility [17][18][19] . Gangliosides are not only detected at high levels in tumors of neuroectodermal cell origin but also related to the biological and clinical behavior of many kinds of tumors 20 . Recently, some analysis revealed that patients with higher expression of B4GALNT1 and GM2/GD2 correlated with poorer prognosis in renal cell carcinoma (TCGA data set; Human Protein Atlas), neuroblastoma 21 , and melanoma 22 . Thus, B4GALNT1 gene is considered to be key tumor-associated antigens [23][24][25][26][27] , indicating that their expression is a meaningful marker for metastatic condition and are potential therapeutic targets for melanoma.Our findings indicate the involvement of B4GALNT1 and GM2/GD2 in tumor establishment and progression as well as a potential direction of therapeutic approach via controlling B4GALNT1, and consequently GM2/GD2 expression in cancers such as melanoma. Scientific RepoRtS |(2020) 10:1199 | https://doi.Generation of GM2/GD2-positive SH4 melanoma clones. The SH4 cells were transfected with expression vectors with or without B4GALNT1 gene cassette, to establish GM2/GD2-positive and -negative SH4 clones. Two GM2/GD2-high clones were selected by single cell isolation (#4 and #5, Fig. S2A). These two clones showed significa...

Alterations to glycans in cancer patients have been used to identify novel tumor biomarkers. Most of these studies have focused on protein glycosylation but less attention has been paid to free-glycans. Here, we analyzed acidic free-glycans in the urine of cancer patients to identify novel tumor marker candidates. Specifically, urine samples were collected from patients with gastric cancer, pancreatic cancer and cholangiocarcinoma as well as normal controls. The free-glycans were extracted from creatinine-adjusted urine and fluorescently labeled with 2-aminopyridine. Initially, we performed profiling of urinary free-glycans by high-performance liquid chromatography and mass spectrometry with enzymatic and chemical degradation. More than 100 glycans, including novel structures, were identified. The chromatographic peaks suggested some of these glycans were present at elevated levels in cancer patients. To verify cancer-associated alterations, we compared the glycan levels between cancer patients and normal controls by selected reaction monitoring. Representative structures of glycans with elevated levels in cancer patients included the following: small glycans related to sialyllactose; sialyl Lewis X; lactose- and N-acetyllactosamine (LacNAc) type-II-core glycans with LacNAc (type-I or II)-extensions and modifications of α1,3/4-fucose and/or 6-sulfate on the Glc/GlcNAc; free-N-glycans containing sialylation or β1,6-branch of 6-sulfo Lewis X; novel NeuAcα2-3Galβ1–4(+/−Fucα1–3)Xylα1–3Glc glycans. Our results provide further insight into urinary free-glycans and suggest the potential utility of these compounds as tumor markers.

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