As shown in Figure S11, already 4 h of culture with 50 μM canavanine in arginine-free medium evoked pronounced changes in the phosphorylation status of proteins involved in protein synthesis such as 4EBP1 (mTOR pathway) and eIF2α (GCN2 pathway) in both glioblastoma cell lines. Here, MTOR is linked to glioblastoma.