Abstract POSTER-BIOL-1323: Elevated MGAT3 expression in ovarian cancer cells is epigenetically regulated and correlates with expression of bisecting GlcNAc-modified proteins

Abstract

Abstract Changes in the glycosylation of membrane proteins are a common feature of malignant transformation including ovarian cancer development. Of particular interest are N-linked glycans because these cell surface glycans mediate various cellular functions in cell-cell communication, cell adhesion, and cell motility. However the nature of these changes, their underlying molecular mechanisms, and the biological function of these glycans are poorly understood. In the present study, N-glycans were released from extracted membrane glycoproteins from ovarian cancer and normal ovarian epithelial cell lines and analysed using electrospray ionisation mass spectrometry; RT-qPCR measured gene expression of related glycosyltransferases; bisulfite sequencing analysed DNA methylation of the corresponding genes. We identified characteristic glycan features unique to membrane proteins of ovarian cancer cells. Among those ovarian cancer specific N-glycans were the ‘bisecting N-acetyl-glucosamine (GlcNAc)’ type. The bisecting GlcNAc is the product of the enzyme MGAT3 (beta-1,4-N-acetylglucosaminyltransferase 3) and the expression of the MGAT3 gene was elevated in ovarian cancer cell lines (SKOV3, IGROV1, A2780, OVCAR3) as compared to normal ovary surface epithelial (HOSE) cells. This elevated MGAT3 expression in ovarian cancer cells correlated with DNA hypomethylation at the transcription start site (TSS) of the MGAT3 promotor, which contains a large CpG island with 204 CpG dinucleotides located -600/+800bp relative to the TSS. This finding suggests that MGAT3 expression is epigenetically regulated. This was validated by the finding that the treatment of HOSE cells with the DNA-methyltransferase inhibitor 5-Aza increased MGAT3 expression and corresponded to a reduction in DNA methylation at the TSS. Taken together, we conclude that the elevated MGAT3 expression in ovarian cancer cells correlates with the presence of the resultant specific N-glycan substructures and with the epigenetic regulation of the associated enzymes by DNA methylation. These findings may stimulate the development of novel anti-glycan targeted drugs and clinical diagnostic tools for ovarian cancer Citation Format: Francis Jacob, Merrina Anugraham, Reto Kohler, Sheri Nixdorf, Arun Vijay Everest-Dass, André Fedier, Viola Heinzelmann-Schwarz, Nicolle H. Packer. Elevated MGAT3 expression in ovarian cancer cells is epigenetically regulated and correlates with expression of bisecting GlcNAc-modified proteins [abstract]. In: Proceedings of the 10th Biennial Ovarian Cancer Research Symposium; Sep 8-9, 2014; Seattle, WA. Philadelphia (PA): AACR; Clin Cancer Res 2015;21(16 Suppl):Abstract nr POSTER-BIOL-1323.