CyTOF profiling of bone marrow immune dynamics across myeloma stages.

Multiple myeloma (MM) orchestrates a profound disruption of immune balance within the bone marrow (BM) microenvironment, driving disease progression and therapeutic resistance. To better understand these complex immune dynamics, we used high-dimensional mass cytometry (CyTOF) profiling to comprehensively characterize the immune landscape of the BM across different stages of myeloma progression, including MGUS (n = 16), smoldering MM (SMM; n = 25), and active MM, both newly diagnosed (n = 43) and relapsed/refractory (n = 104). Our analysis revealed substantial immune remodeling during disease progression, characterized by adaptive immune suppression and extensive infiltration of innate immune populations. Transformation from MGUS to SMM was marked by significant alterations in central and effector memory T helper cells, effector cytotoxic T cells, and an enrichment of monocytic and neutrophil subsets. Active MM stages were further distinguished by increased expansion of myeloid and monocytic lineages, alongside a pronounced reduction in progenitor and transitional B cells. Correspondence analysis demonstrated that specific immune profiles were significantly associated with clinical outcomes, including progression-free survival and overall survival. This study highlights the potential of CyTOF-based molecular profiling to unravel the intricate immune dynamics of the BM microenvironment across MM disease stages, enhancing our understanding of MM pathogenesis and providing a foundation for identifying prognostic biomarkers and tailoring precision immunotherapeutic strategies.