Metabolomic profiling identifies distinct phenotypes for ASS1 positive and negative GBM

Lina Mörén,Nelofer Syed,Kevin Oneill,Julia K Langer,Richard Perryman,Henrik Antti,Tim Crook

doi:10.1186/s12885-018-4040-3

Lina Mörén, Nelofer Syed + Show 5 more

Open Access

https://doi.org/10.1186/s12885-018-4040-3

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Abstract

BackgroundTumour cells have a high demand for arginine. However, a subset of glioblastomas has a defect in the arginine biosynthetic pathway due to epigenetic silencing of the rate limiting enzyme argininosuccinate synthetase (ASS1). These tumours are auxotrophic for arginine and susceptible to the arginine degrading enzyme, pegylated arginine deiminase (ADI-PEG20). Moreover, ASS1 deficient GBM have a worse prognosis compared to ASS1 positive tumours. Since altered tumour metabolism is one of the hallmarks of cancer we were interested to determine if these two subtypes exhibited different metabolic profiles that could allow for their non-invasive detection as well as unveil additional novel therapeutic opportunities.MethodsWe looked for basal metabolic differences using one and two-dimensional gas chromatography-time-of-flight mass spectrometry (1D/2D GC-TOFMS) followed by targeted analysis of 29 amino acids using liquid chromatography-time-of-flight mass spectrometry (LC-TOFMS). We also looked for differences upon arginine deprivation in a single ASS1 negative and positive cell line (SNB19 and U87 respectively). The acquired data was evaluated by chemometric based bioinformatic methods.ResultsOrthogonal partial least squares-discriminant analysis (OPLS-DA) of both the 1D and 2D GC-TOFMS data revealed significant systematic difference in metabolites between the two subgroups with ASS1 positive cells generally exhibiting an overall elevation of identified metabolites, including those involved in the arginine biosynthetic pathway. Pathway and network analysis of the metabolite profile show that ASS1 negative cells have altered arginine and citrulline metabolism as well as altered amino acid metabolism. As expected, we observed significant metabolite perturbations in ASS negative cells in response to ADI-PEG20 treatment.ConclusionsThis study has highlighted significant differences in the metabolome of ASS1 negative and positive GBM which warrants further study to determine their diagnostic and therapeutic potential for the treatment of this devastating disease.

Highlights

Tumour cells have a high demand for arginine
GC-TOFMS analysis reveals metabolic differences between argininosuccinate synthetase (ASS) negative and ASS positive GBM We previously demonstrated that ASS negative GBM can be targeted by arginine deprivation therapy using ADIPEG20 whereas ASS positive GBM are unaffected due to their ability to endogenously synthesize arginine [27]
GBM cells were cultured for 48 h as described in materials and methods and both the cell supernatants and cell pellets were harvested for analysis

Summary

Introduction

A subset of glioblastomas has a defect in the arginine biosynthetic pathway due to epigenetic silencing of the rate limiting enzyme argininosuccinate synthetase (ASS1). These tumours are auxotrophic for arginine and susceptible to the arginine degrading enzyme, pegylated arginine deiminase (ADI-PEG20). Mörén et al BMC Cancer (2018) 18:167 aberrant signalling through these pathways is likely to be essential for the development of GBM These studies have identified four distinct molecular subclasses of GBM based on the enrichment of specific molecular alterations (proneural, classical, mesenchymal and neural). These subclasses were shown to have different responses to standard therapies [4]

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