Estrogen-related receptor gamma coordinates glutamine dependence and mitochondrial metabolic flexibility in retinoblastoma

Cancer cells undergo extensive metabolic reprogramming and can become dependent on glutamine to replenish the tricarboxylic acid cycle when glucose-derived carbon is diverted to lactate production, yet the transcriptional programs coordinating this response remain incompletely defined. We previously identified estrogen-related receptor gamma (ESRRG) as a driver of hypoxic adaptation in retinoblastoma (Rb), and here we show that ESRRG also regulates glutamine-responsive metabolism. ESRRG knockdown reduced transcriptional programs associated with glycolysis and glutamine utilization, while pharmacological inhibition with GSK5182 attenuated glutamine-dependent viability and survival. Conversely, ESRRG overexpression increased sensitivity to glutamine withdrawal in mesenchymal stem cells. Functionally, glutamine enhanced basal and maximal respiration, spare respiratory capacity, and ATP-linked respiration in Rb cells, whereas these responses were attenuated by GSK5182. Targeted LC-MS/MS profiling further showed reduced glutamine-responsive accumulation of intracellular glutamine, glutamate, α-ketoglutarate, and downstream TCA-associated metabolites following ESRRG inhibition. These findings identify ESRRG as a regulator of glutamine dependence and mitochondrial metabolic flexibility in Rb and nominates ESRRG-associated glutamine dependence as a potential metabolic vulnerability.