Arginine deprivation induces prolonged autophagy activation and ROS-dependent cell death in glioblastoma multiforme

BACKGROUND: Arginine deprivation was shown to be selectively cytotoxic to GBM cells with cell death being caspase-independent, non-apoptotic. In this study, we assess the impact of prolonged arginine deprivation on GBM cells, the potential activation of autophagy, the mechanism of its activation, and its impact on cell cytotoxicity. METHODS: GBM cell lines A172 and U251 were used in this study and arginine deprivation was induced by a cobalt-substituted, PEGylated human arginase I [HuArgI (Co)-PEG5000]. RESULTS: Arginine deprivation induced prolonged cytotoxicity up to 120 hours post-treatment. Cytotoxicity persisted despite cells overexpressing ASS-1. Arginine deprivation also induced a marked and sustained activation of autophagy, starting at 24 hours and lasting up to 120 hours post-treatment. Autophagy was shown to induce cell death since its inhibition by chloroquine significantly decreased cytotoxicity, indicating that the extensive activation of autophagy is resulting in cell death of GBM cells. Moreover, ROS was shown to accumulate in treated cells and neutralizing ROS using NAC did not affect the autophagic response but led to a complete reversal of cytotoxicity, demonstrating that death by autophagy is dependent on ROS generation. CONCLUSION: Arginine deprivation leads to sustained activation of autophagy and subsequent ROS-dependent cell death in GBM cells.