IDO1 regulating ROS rhythm reveals glycogenolysis/PPP as a cancer treatment target

Reactive oxygen species (ROS) dynamics exhibits rhythmic oscillations in cancer cells but how this rhythm influences tumorigenesis and therapeutic responses remains unclear. Here we found coexistence of ROS rhythmicity and rhythm loss in tumor samples. Under low-ROS conditions, indoleamine 2,3-dioxygenase 1 (IDO1), an immune-checkpoint molecule, binds to KEAP1 for proteasomal degradation in the nucleus. In contrast, elevated ROS levels drive IDO1 translocation into the cytosol, where it binds mitochondria-released heme to form an active holoenzyme. This holoenzyme catalyzes tryptophan to kynurenine that allosterically activates glucose-6-phosphate dehydrogenase, enhancing NADPH production and promoting ROS clearance. However, in hypoxic tumor microenvironments, ROS rhythmicity is lost. Compensating for this, hypoxic tumor cells mobilize the sulfenylated aryl hydrocarbon receptor (AhR)-mediated glycogenolysis pathway to manage disordered ROS accumulation, maintaining elevated ROS levels that favor tumor growth. Dual inhibition of IDO1 and AhR significantly prolongs survival of NSG mice, highlighting enforced disruption of ROS rhythm as a common therapeutic strategy.