Effects of tryptophan deprivation.
Low intracellular (ic) tryptophan (Trp) levels can mediate pro-tumorigenic (blue background) and anti-tumorigenic effects (green background). Mechanisms described in glioma models are highlighted in black letters, mechanisms described in other systems are highlighted in gray. Abbreviations: GCN2: general control non-derepressible-2, p-eIF2α: phosphorylated eukaryotic translation initiation factor 2α, ATF4: activating transcription factor 4, WARS: tryptophanyl-tRNA synthetase, IFN-γ: interferon-gamma.