Abstract 5331: Spatial resolution of immune cell lineages in the tumor microenvironment of plasma cell dyscrasias

Abstract Plasma cell dyscrasias (PCDs) are diseases of the hematologic system, with Multiple Myeloma as the most common disease. Less common PCDs include primary and secondary extramedullary plasmacytomas (EMP), which occur in soft tissues. EMPs are typically solitary and infrequent, often localized in the upper aerodigestive and gastrointestinal tracts, lung, and lymph nodes among other organs, and can convert to Multiple Myeloma. Secondary extramedullary plasmacytomas are often noted in advanced disease following multiple rounds of therapy and are commonly associated with poor prognosis. Studies aimed at gaining a better understanding of soft tissue EMPs, whether solitary plasmacytomas with undiagnosed multiple myeloma or in the context of recurrent or metastatic EMP disease, are limited. In this study, we employ a comprehensive approach using multiple modalities, including dissociated CITE-seq, spatial transcriptomics, and multiplexed spatial immuno-fluorescence imaging to interrogate the tumor and immune landscape in EMP disease. Importantly, the use of the same biomarker antibodies across these modalities provides a cross-data-framework for a deep contextual understanding of the immune and tumor cell organization and cell-to-cell signaling in EMP. Ultimately, this study provides new insights into patient-to-patient and tumor location variability, tumor and immune cell microenvironment heterogeneity, and possible future therapeutic strategies for EMP. Citation Format: Medbh A. Dillon, Lisa Arvidson, Cole G. Phalen, Julian R. Ishibashi, John B. Johanneson, Zachary J. Thomson, Peiyao A. Zhao, Jocelin Malone, Mackenzie S. Kopp, Matthew Norton, Gabriella Spang, Susan A. Ludmann, Adam K. Savage, Claire E. Gustafson, Marla Glass, Emma L. Kuan, Tao Peng, Lucas T. Graybuck, Xiao-jun Li, Troy R. Torgerson, Peter J. Skene, Ananda W. Goldrath, Samuel Jensen, Stephanie Anover-Sombke, Melinda L. Angus-Hill. Spatial resolution of immune cell lineages in the tumor microenvironment of plasma cell dyscrasias [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 5331.