Abstract 7337: Estrogen-related receptor gamma maintains oxidative metabolism via glutamine-derived anaplerosis

Abstract Glutamine (Gln), traditionally considered a nonessential amino acid, becomes essential in cancer cells as the rate of Gln consumption exceeds that of endogenous biosynthesis. This metabolic dependency constitutes a unique “glutamine addiction”. Although many factors, both genetic and environmental, have been shown to contribute to the control of Gln metabolism, the precise regulation of Gln utilization in cancer still remains largely unclear. Here, we identify estrogen-related receptor gamma (ERRγ) as a critical regulator of glutaminolytic enzymes and cellular Gln utilization. RNA-sequencing of four primary retinoblastoma cells lines with or without shRNA-mediated ERRγ knockdown showed that, relative to shGFP controls, shERRγ downregulated genes were enriched for hypoxic adaptation and glycolysis pathways (FDR 0.05), with no change in oxidative phosphorylation, indicating a shift toward lactate-producing glucose flux. Consistent with this, key genes in lactic acid fermentation (PDK1, LDH, MCT1) were significantly reduced (p 0.05). shERRγ also decreased expression of glutaminolysis-related genes (FDR 0.05), suggesting reliance on Gln-derived carbon to sustain TCA activity in a “Warburg-like” state. Functionally, RB006, a model cancer cell line with high basal ERRγ expression, requires exogenous Gln for viability, exhibiting marked cell death upon Gln withdrawal and a dose-dependent increase in proliferation, with ≥ 4mM required for maximal growth. Mesenchymal stem cells (MSCs), which express low ERRγ, were Gln-independent; however, ERRγ overexpression (MSCERRγ), induced both Gln dependence and dose-responsive proliferation. To further assess Gln utilization, cells were supplemented with increasing Gln, and TCA intermediates (glutamate, α-KG, citrate, pyruvate, ATP) were quantified. All lines converted Gln to glutamate in a dose-dependent manner, but only RB006 and MSCERRγ showed parallel increases in α-KG and citrate, consistent with ERRγ-mediated control of GLUD1/2 and downstream reductive carboxylation. High- ERRγ cells demonstrated strong correlations between Gln levels and all metabolites (r 0.9), produced greater metabolite output per unit Gln than MSCs, and exhibited larger stepwise increases in Gln-derived flux, reflecting enhanced glutamine-handling capacity. Our results indicate ERRγ may be necessary to support oxidative phosphorylation via glutamine-derived anaplerosis. We provide evidence that ERRγ is required for glutaminolytic pathways, suggesting that ERRγ may be a key player in the metabolic adaptation of highly proliferative cell lines. Citation Format: Samantha A. McLaughlin, Zelia M. Correa, J. William Harbour, Daniel Pelaez. Estrogen-related receptor gamma maintains oxidative metabolism via glutamine-derived anaplerosis abstract. In: Proceedings of the American Association for Cancer Research Annual Meeting 2026; Part 1 (Regular Abstracts); 2026 Apr 17-22; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2026;86(7 Suppl):Abstract nr 7337.