PO48CHARACTERISING INTRATUMOUR HETEROGENEITY IN PAEDIATRIC GLIOBLASTOMA MULTIFORME USING A NOVEL ADVANCED MASS SPECTROMETRY TECHNIQUE

Abstract

INTRODUCTION: Intratumour heterogeneity (ITH) may account for therapy failure and tumour recurrence in adult glioblastoma multiforme (GBM). Low availability of fresh frozen tissue has hindered characterisation of ITH in paediatric GBM. Here, we propose the application of desorption electrospray ionisation mass spectrometry (DESI-MS) to assess spatial lipidomic profiles of formalin-fixed paraffin-embedded (FFPE) tissue of paediatric GBM. METHOD: Optimisation of DESI-MS has been conducted on FFPE tissue of normal adult brain prior to transfer of the technology to paediatric GBM tissue. Immunohistochemical analyses for proteins associated with lipid biosynthesis delineated distinct intratumour regions. Spatial characterisation of lipids synthesised by these metabolic proteins will permit optimisation of DESI-MS, prior to unbiased lipidomic analyses. RESULTS: Paediatric GBM cell lines grown under lipoprotein-deficient conditions demonstrated greater resilience compared to an adult cell line, indicating distinct lipid metabolism that will be revealed through lipidomic analyses. Proteins associated with lipid biosynthesis demonstrated evidence of ITH in paediatric GBM, with 69% of patients displaying heterogeneous expression of fatty acid synthase that correlated with areas of high cellularity. CONCLUSION: DESI-MS has the potential to characterise early indications of paediatric GBM ITH through characterisation of lipid markers associated with distinct intratumour regions. Proteins associated with the synthesis of identified lipid markers may represent potential therapeutic targets. We anticipate the establishment of an optimised DESI-MS method that will facilitate lipidomic studies of other paediatric brain tumours.