Abstract 5579: MGAloss-of-function regulates mitochondrial oxidative metabolism-induced cancer stem cell phenotype during lymphomagenesis with therapeutic potential

Abstract As an antagonist of MYC oncogene, Max gene associated (MGA) gene are implicated in multiple cancers, proposing the potential role of tumor suppressor. Using multi-omics data of The Cancer Genome Atlas (TCGA, n=10,295) and lymphoma datasets from our group (n=702), we defined genetic features associated with MGA and its related MYC/MAX/MXD network members across 36 cancers. Pan-cancer, MGA mutation, predominant as nonsense or frameshift, was observed in 4.39% of all samples. MGA expression was significantly downregulated in mutated samples than that of wild type samples. Moreover, MGA mutation was positively associated with inferior clinical outcomes in diffuse large B-cell lymphoma (P=0.001 and P<0.001 in 2 independent datasets), peripheral T-cell lymphoma (P=0.044) and natural killer/T-cell lymphoma (P=0.012), encouraging in-depth study on the important role of MGA in lymphomagenesis. Conditional knockout of MGA in hematopoietic system using Vav-iCre (Mgafl/fl, Vav-iCre mice) led to reduction in the numbers of peripheral blood lymphocyte due to blockade differentiation and enhanced stemness as evidenced by flowcytometry and RNA-sequencing (RNA-seq). To investigate the molecular mechanism, we performed pulldown assay in NK-92 cells molecular silencing of MGA or scramble control, and subsequently subjected for mass spectrum analysis. A total of 97 proteins were identified to interaction with MGA and mainly enriched to nucleosome (26), cytosolic ribosome (16), immune response (13), and glycolysis (6). Molecular silencing of MGA, localizing in the nucleolus, interfered with ribosomal RNA processing, enhanced “onco-ribosome” biogenesis, and contributed to aberrant translational program characterized by mitochondrial oxidative metabolism. Changes in mitochondrial respiration and membrane potential are key to maintaining stemness in cancer cells. Considering that stemness is important for tumorigenesis, recurrence, metastasis, and drug resistance, we exploited high-throughput drug screening platform and found that targeted inhibition of Exportin 1 (XPO1) significantly suppressed the viability of tumor cells molecular silencing MGA, which were resistant to chemotherapeutic agents such as gemcitabine, etoposide, etc. Mechanically, molecular silencing MGA induced abnormalities of nucleocytoplasmic localization in 739 proteins involving in mitochondrial respiratory chain complex I assembly, oxidative phosphorylation, and mitochondrial translation, 50% (332/739) of which were rescued by treatment with XPO1 inhibitor Selinexor. In summary, MGA initiated lymphoma cell stemness via onco-ribosome mediated activation of mitochondrial oxidative metabolism. Selinexor targeted the aberrant nucleocytoplasmic localization and served as a promising therapeutic agent. Citation Format: Jie Xiong, Wen-Fang Wang, Wei-Li Zhao. MGAloss-of-function regulates mitochondrial oxidative metabolism-induced cancer stem cell phenotype during lymphomagenesis with therapeutic potential [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 5579.