Abstract 3695: Mitochondrial uncoupling reverses reductive carboxylation in cancer

Abstract

Abstract When electron transport chain (ETC) activity is inhibited upon hypoxia or when cultured in suspension, reductive carboxylation plays an essential role in supporting tumor growth through converting α-ketoglutarate (α-KG) to citrate, which is converted to acetyl-coenzyme A (acetyl-CoA) for lipogenesis. However, there is no effective way to target reductive carboxylation for tumor therapy. In this study, we use the mitochondrial uncoupler niclosamide ethanolamine (NEN) and BAM15 to reverse reductive carboxylation in cancer cells. Uncoupler treatment activates ETC and increases the cellular NAD+/NADH ratio. Using U-13C-glutamine and 1-13C-glutamine tracers, we discovered that uncoupler treatment accelerates the oxidative TCA cycle and blocks reductive carboxylation, particularly under hypoxia and spheroid culture condition. Uncoupler treatment significantly reduces tumor cell proliferation, survival and sphere formation. In addition, the intracellular acetyl-CoA levels are significantly decreased by NEN treatment. Furthermore, lipidomics analysis showed that NEN treatment reduced fatty acid abundance and altered the lipid composition under both normoxia and hypoxia. Together, these data demonstrate mitochondrial uncoupling redirects the α-KG flux from reductive carboxylation back to the oxidative TCA cycle, highlighting that the ETC activity and NAD+/NADH ratio is the key switch that determines the metabolic fate of α-KG. Reversing reductive carboxylation could be one key mechanism that mitochondrial uncoupler inhibits tumor growth. Citation Format: Haowen Jiang, Clifford Jiajun He, Albert M. Li, Bo He, Yang Li, Jiangbin Ye. Mitochondrial uncoupling reverses reductive carboxylation in cancer. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 3695.