title: Specific glycosylation of membrane proteins in epithelial ovarian cancer cell lines: glycan structures reflect gene expression and DNA methylation status.
abstract: Epithelial ovarian cancer is the fifth most common cause of cancer in women worldwide bearing the highest mortality rate among all gynecological cancers. Cell membrane glycans mediate various cellular processes such as cell signaling and become altered during carcinogenesis. The extent to which glycosylation changes are influenced by aberrant regulation of gene expression is nearly unknown for ovarian cancer and remains crucial in understanding the development and progression of this disease. To address this effect, we analyzed the membrane glycosylation of non-cancerous ovarian surface epithelial (HOSE 6.3 and HOSE 17.1) and serous ovarian cancer cell lines (SKOV 3, IGROV1, A2780, and OVCAR 3), the most common histotype among epithelial ovarian cancers. N-glycans were released from membrane glycoproteins by PNGase F and analyzed using nano-liquid chromatography on porous graphitized carbon and negative-ion electrospray ionization mass spectrometry (ESI-MS). Glycan structures were characterized based on their molecular masses and tandem MS fragmentation patterns. We identified characteristic glycan features that were unique to the ovarian cancer membrane proteins, namely the "bisecting N-acetyl-glucosamine" type N-glycans, increased levels of α 2-6 sialylated N-glycans and "N,N'-diacetyl-lactosamine" type N-glycans. These N-glycan changes were verified by examining gene transcript levels of the enzymes specific for their synthesis (MGAT3, ST6GAL1, and B4GALNT3) using qRT-PCR. We further evaluated the potential epigenetic influence on MGAT3 expression by treating the cell lines with 5-azacytidine, a DNA methylation inhibitor. For the first time, we provide evidence that MGAT3 expression may be epigenetically regulated by DNA hypomethylation, leading to the synthesis of the unique "bisecting GlcNAc" type N-glycans on the membrane proteins of ovarian cancer cells. Linking the observation of specific N-glycan substructures and their complex association with epigenetic programming of their associated synthetic enzymes in ovarian cancer could potentially be used for the development of novel anti-glycan drug targets and clinical diagnostic tools.
authors.affiliation: From the ‡Department of Chemistry & Biomolecular Sciences, Biomolecular Frontiers Research Centre, Faculty of Science, Macquarie University, NSW 2109, Sydney, Australia;
authors.forename: Merrina
authors.initials: M
authors.lastname: Anugraham
authors.affiliation: §Gynaecological Research Group, Department of Biomedicine, Women's University Hospital Basel, University of Basel, Basel 4003, Switzerland; ¶Ovarian Cancer Group, Adult Cancer Program, Lowy Cancer Research Centre, Prince of Wales Clinical School, University of New South Wales, NSW 2052, Sydney, Australia.
authors.forename: Francis
authors.initials: F
authors.lastname: Jacob
authors.affiliation: ¶Ovarian Cancer Group, Adult Cancer Program, Lowy Cancer Research Centre, Prince of Wales Clinical School, University of New South Wales, NSW 2052, Sydney, Australia.
authors.forename: Sheri
authors.initials: S
authors.lastname: Nixdorf
authors.affiliation: From the ‡Department of Chemistry & Biomolecular Sciences, Biomolecular Frontiers Research Centre, Faculty of Science, Macquarie University, NSW 2109, Sydney, Australia;
authors.forename: Arun Vijay
authors.initials: AV
authors.lastname: Everest-Dass
authors.affiliation: §Gynaecological Research Group, Department of Biomedicine, Women's University Hospital Basel, University of Basel, Basel 4003, Switzerland; ¶Ovarian Cancer Group, Adult Cancer Program, Lowy Cancer Research Centre, Prince of Wales Clinical School, University of New South Wales, NSW 2052, Sydney, Australia.
authors.forename: Viola
authors.initials: V
authors.lastname: Heinzelmann-Schwarz
authors.affiliation: From the ‡Department of Chemistry & Biomolecular Sciences, Biomolecular Frontiers Research Centre, Faculty of Science, Macquarie University, NSW 2109, Sydney, Australia; nicki.packer@mq.edu.au.
authors.forename: Nicolle H
authors.initials: NH
authors.lastname: Packer
mesh_terms: D002460:Cell Line; D045744:Cell Line, Tumor; D002853:Chromatography, Liquid; D019175:DNA Methylation; D004847:Epithelial Cells / Q000378:metabolism; D005260:Female; D015972:Gene Expression Regulation, Neoplastic; D006031:Glycosylation; D016695:Glycosyltransferases / Q000235:genetics; D006801:Humans; D008565:Membrane Proteins / Q000378:metabolism*; D010051:Ovarian Neoplasms / Q000378:metabolism*; D011134:Polysaccharides / Q000378:metabolism; D021241:Spectrometry, Mass, Electrospray Ionization; D053719:Tandem Mass Spectrometry
chemical_list: D008565:Membrane Proteins; D011134:Polysaccharides; D016695:Glycosyltransferases