PO-232 Lewis glycans and their epigenetic regulation are associated with neuroblastoma aggressiveness

Introduction Glycans are diverse and complex molecules with a crucial participation in critical events of cell biology. Their implications in adult cancer are widely reported, but little is known about their role in paediatric cancer such as Neuroblastoma (NB). NB is the most common paediatric malignancy diagnosed before the first birthday in which MYCN oncogene amplification is associated with poor prognosis. Hence, the study of aberrant glycosylation is a promising field to understand NB transformation and to find new therapeutic targets. Material and methods This study was carried out over five established human NB cell lines and patients´ tumour samples with different MYCN status. Terminal glycans expression and selectin binding capacity was characterised by flow cytometry. Expression of enzymes involved in glycans biosynthesis was measured by qRT-PCR. The role of Core2-O glycans was studied by C2GNT1 silencing and in vitro cell adhesion, proliferation and migration. Epigenetic regulation was evaluated using Trichostatin A (TSA) histone deacetylase inhibitor. Results and discussions Minimal expression of truncated glycans (T, Tn and STn) was found in all cell lines tested. In contrast, an association between MYCN amplification and Lewis glycan family (mainly SleX and LeY) expression was observed both in cell lines and patients´ samples. In accordance, MYCN-amplified cells showed overexpression of C2GNT1, the glycoenzyme responsible for initiating the Core 2 O-glycans branch that could be extended to the Lewis antigens. Furthermore, we detected overexpression of ST3Gal4, FUT4, 7, 9 and 11, terminal enzymes of this biosynthetic pathway. In the same light, since selectins binding depends on Lewis glycans presence, we observed an increase on E- and P-selectin binding in MYCN-amplified cell lines. Silencing of C2GNT1 provoked a reduction in Lewis glycans expression and decreased in vitro cell adhesion, migration and proliferation in both MYCN status cells. Interestingly, C2GNT1 silencing of MYCN-amplified cells also showed a decreased in E- and P-selectin binding. Finally, inhibition of histone deacetylase in MYCN-non amplified cells produced a significant increase in the expression of Lewis glycans and enzymes FUT3 and FUT7. Conclusion In this work we highlight the impact of Core-2 Lewis family as part of O-glycans in malignant NB cell behaviour, the enzymes involved and the epigenetic regulation in relation to MYCN status.