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Tissue-resident macrophages promote multiple myeloma early dissemination and progression via IL-6 and TNFa

ABSTRACT: Multiple myeloma (MM) is a plasma cell malignancy characterized by the presence of multiple foci in the skeleton. These distinct tumor foci indicate cycles of tumor growth and dissemination that seed new clusters and drives disease progression. Utilizing an intra-tibial Vk*MYC murine myeloma, we found that CD169 + radiation-resistant, tissue-resident macrophages (MPs) were critical for myeloma early dissemination and disease progression. While depletion of these MPs had no effect on tumor proliferation, it reduced myeloma BM egress and spreading to other bones, which improved overall survival as a single therapy and in combination with BM transplantation. Myeloma dissemination correlated with an increased inflammatory signature in BM MPs, as well as production of IL-6 and TNFα by tumor-associated MPs (TAMs). Exogenous i.v. IL-6 and TNFa could trigger myeloma intravasation in the BM by increasing vascular leakiness in the BM, and by enhancing myeloma motility by reducing CD138 adhesion. Moreover, mice lacking IL-6 had defects in myeloma dissemination as in MP-depleted recipients. While in TNFa or TNFaR deficient mice had defects in MM dissemination, engraftment was also impaired. These effects on myeloma dissemination required production of cytokines in the radiation-resistant compartment, containing these radiation-resistant BM MPs. Taken together, we propose BM egress of myeloma cells is regulated by localized inflammation in foci, driven in part by CD169 + MPs.

ORGANISM(S): Mus musculus

PROVIDER: GSE176385 | GEO | 2021/06/09

REPOSITORIES: GEO

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Project description:Multiple myeloma involves early dissemination of malignant plasma cells across the bone marrow; however, the initial steps of dissemination remain unclear. Human bone marrow-derived mesenchymal stromal cells (hMSCs) stimulate myeloma cell expansion (e.g., IL-6) and simultaneously retain myeloma cells via chemokines (e.g., CXCL12) and adhesion factors. Hence, we hypothesized that the imbalance between cell division and retention drives dissemination. We present an in vitro model using primary hMSCs co-cultured with INA-6 myeloma cells. Time-lapse microscopy revealed proliferation and attachment/detachment dynamics. Separation techniques (V-well adhesion assay and well plate sandwich centrifugation) were established to isolate MSC-interacting myeloma subpopulations that were characterized by RNAseq, cell viability and apoptosis. Results were correlated with gene expression data (n=837) and survival of myeloma patients (n=536). On dispersed hMSCs, INA-6 saturate hMSC-surface before proliferating into large homotypic aggregates, from which single cells detached completely. On confluent hMSCs, aggregates were replaced by strong heterotypic hMSC-INA-6 interactions, which modulated apoptosis time-dependently. Only INA-6 daughter cells (nMA-INA6) detached from hMSCs by cell division but sustained adherence to hMSC-adhering mother cells (MA-INA6). Isolated nMA-INA6 indicated hMSC-autonomy through superior viability after IL6 withdrawal and upregulation of proliferation-related genes. MA-INA6 upregulated adhesion and retention factors (CXCL12), that, intriguingly, were highly expressed in myeloma samples from patients with longer overall and progression-free survival, but their expression decreased in relapsed myeloma samples. Altogether, in vitro dissemination of INA-6 is driven by detaching daughter cells after a cycle of hMSC-(re)attachment and proliferation, involving adhesion factors that represent a bone marrow-retentive phenotype with potential clinical relevance.

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Tissue-resident macrophages promote multiple myeloma early dissemination and progression via IL-6 and TNFa

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