Abstract 4919: Decoding the tumor microenvironment of NF1 tumors using spatial and cell-type specific analyses of patient-derived organoids

Abstract Neurofibromatosis Type I (NF1) is a tumor-predisposing genetic syndrome driven by germline variants in the tumor suppressor gene NF1. Patients with NF1 frequently develop benign peripheral nerve sheath tumors, including cutaneous and plexiform neurofibromas (cNFs, pNFs), which are associated with significant comorbidities. Notably, a proportion of pNFs can progress to malignant peripheral nerve sheath tumors (MPNSTs), aggressive soft tissue sarcomas, in approximately 15% of patients. Current therapies for NF1 associated tumors are extremely limited, being the MEK 1/2 inhibitors selumetinib and mirdametinib the only FDA-approved drugs for patients with symptomatic inoperable pNFs. However, both treatments are not curative and require continuous administration, with associated toxicities that highlight the need for alternative therapies. NF1 tumors present a complex microenvironment comprising different cell types including Schwann cells, fibroblasts, and mast cells embedded in a dense extracellular matrix (ECM). Efforts to identify effective non-surgical treatments are constrained by the rarity of these tumors, their marked cellular heterogeneity, their abundant ECM deposition, and the lack of patient-derived models that accurately recapitulate these complex features. We have developed patient-derived organoids of both neurofibromas (Nguyen et al, Cell Reports Methods 2024) and MPNSTs (Al Shihabi et al, Cell Stem Cell 2024) that preserve the cellular and molecular characteristics of parental tumors, providing robust tractable models for drug discovery studies. Here, we are developing a single-cell typing, image-based assay, integrating multiplex immunofluorescence with computational techniques, to evaluate the impact of drugs on individual cell subpopulations within NF1 organoids. This methodology will be coupled with our high throughput mini-ring organoid screening platform (Phan et al, Communications Biology 2019; Al Shihabi et al, Science Advances 2022), to rapidly screen FDA-approved drugs, along with a modified 3D-compatible Cell Painting assay for providing unbiased phenotypic readouts of the impact of therapeutic agents on each cell type as well as proteomics approaches. By integrating these methods, we aim to address the challenges posed by the cellular heterogeneity of NF1-associated tumors and to identify precision therapeutic strategies for NF1 patients. Citation Format: Alberto Mendoza-Valderrey, Michael J. Lippincott, Huyen Thi Lam Nguyen, Jenna Tomkinson, Cameron Mattson, Dave Bunten, Summer Norris, Jeremy Jacobson, Jackson Chin, Paul Piehowski, Le Day, Chelsea Hutchinson Bunch, Christopher Anderton, Brittney Gorman, Sara Gosline, Gregory P. Way, Alice Soragni. Decoding the tumor microenvironment of NF1 tumors using spatial and cell-type specific analyses of patient-derived organoids [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 4919.