PO-368 Epigenetic regulation of glycosylation and the impact on chemoresistance in ovarian and breast cancer

Introduction Glycosylation is epigenetically regulated and is a fundamental post-translational modification altered in cancer. These alterations impact on tumour progression, and promote tumour survival. In the literature, there is a clear link between chemoresistance and hypoxia, hypoxia and epigenetics and more recently glycosylation and epigenetics. Our remit is to bring these paradigms together, to open up new avenues of approach for the detection, diagnosis and treatment of ovarian and breast cancer. Material and methods Ovarian and breast cancer cells were treated with the DNA methyltransferase inhibitor, 5-AZA-2-deoxycytidine (5-AZA-dC). Cells were exposed to normoxia and differential hypoxic conditions. Methylation status of hypoxia-exposed cells and the normoxia-controls as well as demethylation following 5-AZA-dC treatment was confirmed by flow cytometry. N-glycans from cell secreted glycoproteins were analysed using hydrophilic interaction liquid chromatography (HILIC) and mass spectrometry. Western blot analyses assessed apoptosis, senescence, autophagy and epithelial to mesenchymal transition (EMT). The Oris Migration Assay monitored the cell migration, while qRTPCR measured candidate glycosyltransferases and transcription factor (TFs) gene expression in these samples. Results and discussions Branching and sialylation known to aid in tumour survival, were increased on secreted N-glycans from chemosensitive cells compared to chemoresistant cells following treatment with 5-AZA-dC and in all cells under hypoxic conditions. These changes correlated with increases in MGAT5 and ST3GAL4 expression in demethylated ovarian cancer cells. GATA2/3 were identified in-silico, as possible TFs for these genes. Results show that there is a correlation between, ST3GAL4 and GATA2 and MGAT5 and GATA3, respectively. 5-AZA-dC-treated and hypoxia-exposed cells displayed increased migration, with a greater effect in chemosensitive demethylated- and 0.5% hypoxia-exposed cells compared to chemoresistant cells. Apoptotic and senescence markers were increased in 5-AZA-dC treated cells. Conclusion These results give insight into the effects epigenetic alterations have on cancer cell glycosylation and how these may impact on the overall fate of those cells. The GATA2/3 TFs are linked to cancer stage, increased invasiveness and are possible therapeutic targets. Our data show a correlation between GATA2/3 and the levels of glycosyltransferases involved in branching and sialylation which are involved in cancer cell survival and metastases.