Abstract 3057: Selective targeting of sumoylation disrupts mitochondrial homeostasis via TRAP1 to suppress growth of non-Hodgkin lymphoma (NHL) B-cells

Abstract Aberrant sumoylation is frequently observed in human tumors, highlighting its significance in cancer biology and therapeutic targeting. We investigated the mechanistic effects of inhibiting SUMOylation in B-cell non-Hodgkin lymphoma (NHL) using the inhibitor TAK-981 (subasumstat). SUMO pathway components were highly expressed in lymph nodes from NHL patients compared with reactive lymph nodes. TAK-981 potently inhibited growth of NHL cell lines (IC50 ∼10 nM), inducing apoptosis and reducing cell viability over 24-72 hours, alongside rapid, dose-dependent global protein desumoylation. Consistent with these in-vitro effects, TAK-981 treatment significantly prolonged survival of OCI-LY3 and Raji xenograft-bearing mice by approximately 5.5 weeks relative to control. To uncover SUMO-regulated pathways relevant to the TAK-981 response, we performed RNA-Seq on B-NHL cell lines. Gene set enrichment analysis revealed significant downregulation of MYC targets and oxidative phosphorylation-related genes. MitoMiner gene-ontology analysis further indicated suppression of mitochondrial membrane organization and depolarization pathways. Subcellular fractionation showed that TAK-981 caused dramatic desumoylation of proteins in the mitochondrial fraction compared to the cytosol. LC-MS/MS profiling of mitochondrial extracts from U2932 and Raji cells identified 40 and 44 proteins, respectively, with 4-fold reductions in SUMO2/3 binding. The mitochondrial chaperone TRAP1 (Hsp75), which in Raji cells exhibited ∼5-fold decreased SUMO association. Given TRAP1’s pro-oncogenic role in maintaining mitochondrial integrity and metabolism, we investigated how SUMOylation affects TRAP1. We confirmed SUMO2/3-TRAP1 association in mitochondria, which was disrupted by TAK-981 in FLAG-TRAP1-expressing HEK293T cells. Cycloheximide chase assays demonstrated that desumoylation did not alter TRAP1 protein stability; however, it caused a redistribution of TRAP1 from mitochondria to the cytosol, indicating that SUMOylation guides TRAP1 mitochondrial localization. Consistent with widespread loss of mitochondrial SUMOylation, TAK-981 induced mitochondrial depolarization, ultrastructural defects, and reduced oxidative phosphorylation as measured by Seahorse analysis. Metabolomic profiling confirmed decreases in TCA cycle intermediates. Importantly, TRAP1 overexpression in Raji cells partially restored mitochondrial function and protected cells from TAK-981-induced apoptosis, supporting a functional requirement for SUMOylated TRAP1 in lymphoma cell survival. Collectively, our findings show that TAK-981 disrupts mitochondrial SUMOylation, leading to metabolic dysfunction and apoptosis in B-NHL cells. SUMO-dependent regulation of TRAP1 emerges as a mechanistic driver and a promising therapeutic vulnerability in lymphoma. Citation Format: Vi Lam, Tingting Liu, Heifeng Shen, Olga V. Danilova, Katarzyna Dabrowska, Sonia Rodriguez, Courtney Jones, Martina Cusan, Angelo D’Alessandro, Lapo Alinari, Lili Wang, Tycel Phillips, Patrick Pirrotte, Zheng Xia, Alexey Danilov. Selective targeting of sumoylation disrupts mitochondrial homeostasis via TRAP1 to suppress growth of non-Hodgkin lymphoma (NHL) B-cells 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 3057.