BACR 18: Polysialyltransferase inhibition modulates tumour cell growth, migration and invasion in neuroblastoma
1Institute of Cancer Therapeutics, University of Bradford, Bradford, UK,2University of Leeds, Leeds, UK
Polysialic acid (polySia) is expressed on the surface of NCAM (neuronal cell adhesion molecule) in many cancer cells where it modulates cell growth, adhesion, migration, invasion and metastasis. It is strongly associated with poor clinical prognosis and correlates with aggressive/invasive disease in neuroblastoma and many other neuroendocrine tumours. SiRNA knockdown of polysialyltransferase (polyST), which is responsible for polySia biosynthesis, abolishes tumour cell growth and dissemination.
Progress towards development of polyST inhibitors has been limited by lack of an efficient technique for quantitative assessment of enzyme activity. We have validated a highly sensitive UPLC-based inhibition assay, amenable to high-throughput screening , which we have utilised to identify small molecule polyST inhibitors. Using isogenic cell lines (C6-STX: polySia+/ST8SiaII+ and C6-WT: polySia-/ST8SiaII-) and naturally polySia expressing human neuroblastoma cells (SH-SY5Y, IMR-32) compounds were evaluated for their ability to reduce polySia expression and to modulate cell function in vitro. Specificity of agents for polySTs over other sialyltransferases (STs; ?-2,3 and ?-2,6) was subsequently investigated using lectin differential labelling probes. Effects of polyST inhibitors on intracellular signalling events were also investigated. In parallel studies, we have evaluated polySia expression in neuroblastoma metastatic bone marrow deposits.
We have identified a series of selective polyST inhibitors. ICT-3176, a carbohydrate tool compound, has been utilised as an exemplar polyST inhibitor. ICT-3176 significantly reduced polySia expression, neuroblastoma cell growth, migration and invasion. These effects were only found in cell lines expressing ST8SiaII and polySia. Selectivity of ICT-3176 over other STs was confirmed (as evidenced by lack of effect on ?-2,3 and ?-2,6-sialic acid expression). ICT3176 has been shown to disturb the dynamics of focal adhesion kinase and modulate ERK1/2, CREB, AKT and VEGFR3 signalling. In preliminary parallel studies, polySia expression was found to be co-localised with GD2 expression in metastatic bone marrow deposits.
In summary, we have identified polyST inhibitors which significantly decrease neuroblastoma cell growth, migration and invasion in vitro through modulation of polySia assembly. This work paves the way for development of a novel therapeutic for the treatment of neuroblastoma.