ASS1 and glioblastoma: To investigate the metabolic response of these different GBM cell populations to arginine deprivation, a representative ASS negative (SNB19) and ASS positive (U87) cell line was treated with or without the arginine degrading enzyme, ADI-PEG20 (1 μg/ml) for 48 h and both supernatants and cell pellets were analysed by 1D GC-TOFMS.