Abstract PO-034: Targeting metabolic plasticity and flexibility via SIRT3 inhibition to restrain nucleotides availability in DLBCLs
Authors: Li Meng , Park Noel R , Chin Chris , Mlynarczyk Coraline , Lin Hening , Davidson Shawn , Melnick Ari M 
Published: June 2024

Abstract
Cancer cells need metabolic adaptations to survive in hostile environment such as low nutrient and drug treatment conditions. DLBCLs (Diffuse large B cell lymphoma) originate from a metabolic competitive/challenging environment of germinal center (GC) when B cells undergo positive selections against antigens. However, it is largely unknown whether and how metabolic flexibility (the ability to use different nutrients) and plasticity (the ability to process the same nutrient differently) contribute to DLBCLs. Our previous study identified that SIRT3, the only mitochondrial protein deacetylase, is critical to survival and proliferation of DLBCLs by promoting glutaminolysis. Our mitochondrial localized SIRT3 inhibitor, YC8-02, has pan-toxicity to all DLBCL cells tested regardless of different subtypes with somatic mutations. Here, we observed glucose as an alternative nutrient source to compensate in the TCA cycle in SIRT3 deficient cells. DLBCLs exhibited resistance to SIRT3 inhibition in high glucose condition, while SIRT3 inhibited DLBCLs highly depend on glucose metabolism. The combination of YC8-02 with glucose metabolism inhibitors induces synergistic killing to DLBCLs. As glucose is the main carbon source of cells, it is unknown how DLBCLs manage the flexibility of using glucose for different purposes. Using in vivo metabolic imaging (MALDI), we observed that, in contrast to normal GC B cells, lymphomas specifically use the glucose for de novo nucleotide synthesis. SIRT3 inhibition decreased nucleotide levels in DLBCL cells in vitro and in vivo. The metabolic flux tracing showed that DLBCL cells requires SIRT3 activity to activate a glucose/serine/one-carbon metabolism pathway for de novo nucleotide biosynthesis, and Inhibition of SIRT3 decreased the glucose and serine being used for nucleotides in DLBCLs. Serine as another potent source for nucleotides can rescue DLBCLs from SIRT3 inhibition. Furthermore, we validated that overexpression of enzymes, like MTHFD2, in one carbon metabolism pathway can rescue the proliferation in SIRT3 deficient cells. High nucleotides levels in medium also help DLBCLs survival in YC8-02 treatments. To overcome the metabolic flexibility on environmental nucleotides, we used inhibitors of nucleoside transporters (ENT1/2), dipyridamole and draflazine, which can synergize with YC8-02 to kill DLBCLs in vitro and eradicate systemic lymphomas in vivo. In summary, our results illustrate that DLBCLs with active SIRT3 exhibit metabolic plasticity by repurposing glucose to nucleotide biosynthesis, while lymphoma cells can also reply on metabolic flexibility to manage nutrient usage and gain extracellular nucleotides for survival under SIRT3 inhibition. Our combination treatment SIRT3 and ENT inhibitors can be a promising therapy for DLBCLs by restraining their metabolic plasticity and flexibility.
Citation Format: Meng Li, Noel R Park, Chris Chin, Coraline Mlynarczyk, Hening Lin, Shawn Davidson, Ari M Melnick. Targeting metabolic plasticity and flexibility via SIRT3 inhibition to restrain nucleotides availability in DLBCLs [abstract]. In: Proceedings of the Fourth AACR International Meeting on Advances in Malignant Lymphoma: Maximizing the Basic-Translational Interface for Clinical Application; 2024 Jun 19-22; Philadelphia, PA. Philadelphia (PA): AACR; Blood Cancer Discov 2024;5(3_Suppl):Abstract nr PO-034.