Abstract LB474: Menin inhibition impairs metastatic colonization of Ewing sarcoma

Abstract Menin is a scaffolding protein that can act as either tumor suppressor or oncogene depending on cell context. In MLL rearranged (MLLr) leukemia, menin functions as an oncogene and a small molecule inhibitor of menin was recently FDA approved for MLLr leukemia therapy (Revumenib, Syndax). We previously showed than menin promotes tumorigenicity of Ewing sarcoma (EwS). In the current work we studied menin knockout (MEN1-KO) and VTP50469 (preclinical precursor to Revumenib) treated EwS cells to test the hypothesis that menin inhibition could be leveraged to impede metastatic progression of EwS. Tumorigenic and metastatic capacities of MEN1-KO A673 and TC32 cells were assessed in subcutaneous, tail vein, and/or spontaneous metastasis models. RNAseq of control and MEN1-KO tumors was performed to define mechanisms by which EwS cells escape deleterious effects of menin loss. To test the effect of pharmacologic inhibition of menin on colonization of disseminated EwS tumor cells (DTCs), mice were inoculated with 50,000 wild type A673 cells via tail vein and then fed control or 0.1% VTP50469 chow for up to 40 days. Results of our studies showed that MEN1-KO cells were reproducibly deficient in the capacity to initiate local and disseminated tumors following either subcutaneous or tail vein injection. Spontaneous metastasis of MEN1-KO tumors from subrenal capsules to livers was also impaired. Defects in metastasis were evident despite enhanced invasive capacity, suggesting that menin loss inhibited tumor colonization. Transcriptomic profiling revealed that EwS cells bypassed menin depletion to restore tumorigenicity by upregulating MYC, RNA transcription, and G2-M checkpoint gene programs and downregulating TGF-beta, NFkB, and apoptosis programs. Colonization of wild type DTCs was inhibited by pharmacologic menin inhibition, mimicking MEN1-KO. At 33 days post cell injection, 0/10 control mice and 12/20 VTP50469 treated mice were tumor free (p<0.0001). Two mice remained tumor free a month after withdrawing drug. Histology studies of VTP50469 mice are pending and will be presented at the meeting. These data reveal a critical role for menin in EwS tumor colonization and suggest that menin inhibitors could be repurposed as metastasis prevention agents in EwS patients who are at high risk of metastatic relapse. Citation Format: Katherine Braun, Mohamed Ahmed, Nicolas Garcia, Elizabeth Lawlor. Menin inhibition impairs metastatic colonization of Ewing sarcoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2025; Part 2 (Late-Breaking, Clinical Trial, and Invited Abstracts); 2025 Apr 25-30; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2025;85(8_Suppl_2):Abstract nr LB474.