An IL-1β-driven neutrophil-stromal cell axis fosters a BAFF-rich protumor microenvironment in individuals with multiple myeloma

Based on the TLR4/NLRP3 Pathway and Its Impact on the Formation of NETs to Explore the Mechanism of Ginsenoside Rg1 on Acute Gouty Arthritis

This study investigated whether ginsenoside Rg1 (G-Rg1) alleviated acute gouty arthritis (AGA) in rats by modulating the TLR4/NLRP3 pathway and neutrophil extracellular trap (NET) formation. Rats were orally administered G-Rg1 or colchicine (Col) for 7 days, and monosodium urate (MSU) was injected into the ankle joints on day 5 to induce AGA. Joint swelling, histopathology (HE staining), and serum markers (MPO, NE, MPO-DNA, IL-6, IL-1β; ELISA) were assessed at the baseline and 6-36 h post-modeling. Western blot and immunofluorescence analyzed the NET-related and TLR4/NLRP3 pathway proteins in synovial tissue. G-Rg1 significantly reduced ankle swelling and synovial inflammation compared with the AGA group, lowered the serum IL-6, IL-1β, MPO, NE, and MPO-DNA levels, and suppressed NET-associated protein expression. Mechanistically, G-Rg1 downregulated TLR4/NLRP3 pathway activation in synovial tissue. These findings suggest that G-Rg1 mitigates AGA by inhibiting TLR4/NLRP3 signaling, thereby reducing inflammatory cytokine release and NET formation.

Ferroptotic Neutrophils Induce Immunosuppression and Chemoresistance in Breast Cancer

Inducing ferroptosis in tumor cells is emerging as a strategy for treating malignancies that are refractory to traditional treatment modalities. However, the consequences of ferroptosis of immune cells in the tumor microenvironment need to be better understood in order to realize the potential of this approach. In this study, we discovered that neutrophils in chemoresistant breast cancer are highly sensitive to ferroptosis. Reduction of the acyltransferase MOAT1 in chemoresistance-associated neutrophils induced phospholipid reprogramming, switching the preference from monounsaturated fatty acids to polyunsaturated fatty acids, which increased their susceptibility to ferroptosis. Ferroptotic neutrophils secreted PGE2, IDO, and oxidized lipids that suppressed the proliferation and cytotoxicity of antitumor CD8+ T cells. Furthermore, neutrophil ferroptosis was closely related to a distinct subset of IL1β+CXCL3+CD4+ (Fer-CD4) T lymphocytes, which were enriched in chemoresistant tumors. Fer-CD4 T cells orchestrated neutrophil ferroptosis by modulating MOAT1 expression via IL1β/IL1R1/NF-κB signaling. Moreover, Fer-CD4 T cells secreted CXCL3, IL8, and S100A9 to replenish the neutrophil pool in the tumor microenvironment. Ferroptotic neutrophils in turn fostered Fer-CD4 T-cell differentiation. In spontaneous tumorigenesis mouse models, targeting IL1β+ CD4+ T cells or IL1R1+ neutrophils broke the cross-talk, restraining neutrophil ferroptosis, enhancing antitumor immunity, and overcoming chemoresistance. Overall, these findings uncover the role of neutrophil ferroptosis in shaping the immune landscape and propose appealing targets for restoring immunosurveillance and chemosensitivity in breast cancer. Significance: In chemoresistant breast cancer, IL1β+CXCL3+CD4+ T cells mediate neutrophil ferroptosis that suppresses antitumor immunity, indicating that interfering with this intercellular cross-talk could be an attractive strategy to reverse chemoresistance.

New horizons in our understanding of precursor multiple myeloma and early interception

Multiple myeloma is an incurable plasma cell malignancy that evolves over decades through the selection and malignant transformation of monoclonal plasma cells. The evolution from precursor states to symptomatic disease is characterized by an increasing complexity of genomic alterations within the plasma cells and a remodelling of the microenvironment towards an immunosuppressive state. Notably, in patients with advanced disease, similar mechanisms of tumour escape and immune dysfunction mediate resistance to modern T cell-based therapies, such as T cell-engaging bispecific antibodies and chimeric antigen receptor (CAR)-T cells. Thus, an increasing number of clinical trials are assessing the efficiency and safety of these therapies in individuals with newly diagnosed multiple myeloma and high-risk smoldering multiple myeloma. In this Review, we summarize the current knowledge about tumour intrinsic and extrinsic processes underlying progression from precursor states to symptomatic myeloma and discuss the rationale for early interception including the use of T cell-redirecting therapies.

A single-cell transcriptomic map of the murine and human multiple myeloma immune microenvironment across disease stages

BACKGROUND

The long-term effectiveness of immunotherapies against Multiple Myeloma (MM) remains elusive, demonstrated by the inevitable relapse in patients. This underscores the urgent need for an in-depth analysis of the MM tumor-immune microenvironment (TME). Hereto, a representative immunocompetent MM mouse model can offer a valuable approach to study the dynamic changes within the MM-TME and to uncover potential resistance mechanisms hampering effective and durable therapeutic strategies in MM.

METHODS

We generated a comprehensive single-cell RNA-sequencing atlas of the MM-TME in bone marrow and spleen encompassing different stages of disease, using the immunocompetent 5T33MM mouse model. Through comparative analysis, we correlated our murine dataset with the pathogenesis in MM patients by reanalyzing publicly available datasets of human bone marrow samples across various disease stages. Using flow cytometry, we validated the dynamic changes upon disease progression in the 5T33MM model. Furthermore, interesting target populations, as well as the immune-boosting anti-CD40 agonist (αCD40) therapy were tested ex vivo on murine and human primary samples and in vivo using the 5T33MM model.

RESULTS

In this study, we identified the heterogenous and dynamic changes within the TME of murine and human MM. We found that the MM-TME was characterized by an increase in T cells, accompanied with an exhausted phenotype. Although neutrophils appeared to be rather innocuous at early disease stages, they acquired a pro-tumorigenic phenotype during MM progression. Moreover, conventional dendritic cells (cDCs) showed a less activated phenotype in MM, underscoring the potential of immune-boosting therapies such as αCD40 therapy. Importantly, we provided the first pre-clinical evaluation of αCD40 therapy and demonstrated successful induction of cDC- and T-cell activation, accompanied by a significant short-term anti-tumor response.

CONCLUSIONS

This resource provides a comprehensive and detailed immune atlas of the evolution in human and murine MM disease progression. Our findings can contribute to immune-based patient stratification and facilitate the development of novel and durable (immune) therapeutic strategies in MM.

Multi-omics reveal immune microenvironment alterations in multiple myeloma and its precursor stages

Tumor immune microenvironmental alterations occur early in multiple myeloma (MM) development. In this study, we aim to systematically characterize the tumor immune microenvironment (TME) and the tumor-immune interactions from precursor stages, i.e., monoclonal gammopathy of undetermined significance (MGUS) and smoldering MM (SMM), to newly diagnosed MM, comparing these to healthy donors. Using CIBERSORT, mass cytometry (CyTOF), and single-cell RNA sequencing (scRNA-Seq), we examined innate and adaptive immune changes across these stages. We found a decrease in granulocytes in the TME predicts MM outcomes. HLA-DR is reduced in CD16+ monocytes and plasmacytoid dendritic cells, while myeloid dendritic cells show decreased expression of stress and immune-response genes. NK cells and CD8+ T cells shift from a GZMK+ to a GZMB+ cytotoxic phenotype in the TME, with increased inhibitory markers TIM3 and TIGIT. In paired samples, the proportion and gene expression pattern in patient-specific GZMB+CD8+ T cells remain largely unchanged despite MM progression. Our findings provide a comprehensive immune landscape of MM and its precursors, offering insights into therapeutic strategies. Enhancing neutrophil and NK cell cytotoxicity, tumor antigen presentation, and CD8+ T cell versatility in precursor stages may prevent MM progression.

In vitro models of the crosstalk between multiple myeloma and stromal cells recapitulate the mild NF-κB activation observed in vivo

Multiple myeloma (MM) is linked to chronic NF-κB activity in myeloma cells, but this activity is generally considered a cell-autonomous property of the cancer cells. The precise extent of NF-κB activation and the contributions of the physical microenvironment and of cell-to-cell communications remain largely unknown. By quantitative immunofluorescence, we found that NF-κB is mildly and heterogeneously activated in a fraction of MM cells in human BMs, while only a minority of MM cells shows a strong activation. To gain quantitative insights on NF-κB activation in living MM cells, we combined advanced live imaging of endogenous p65 Venus-knocked-in in MM.1S and HS-5 cell lines to model MM and mesenchymal stromal cells (MSCs), cell co-cultures, microfluidics and custom microbioreactors to mimic the 3D-interactions within the bone marrow (BM) microenvironment. We found that i) reciprocal MM-MSC paracrine crosstalk and cell-to-scaffold interactions shape the inflammatory response in the BM; ii) the pro-inflammatory cytokine IL-1β, abundant in MM patients' plasma, activates MSCs, whose paracrine signals are responsible for strong NF-κB activation in a minority of MM cells; iii) IL-1β, but not TNF-α, activates NF-κB in vivo in BM-engrafted MM cells, while its receptor inhibitor Anakinra reduces the global NF-κB activation. We propose that NF-κB activation in the BM of MM patients is mild, restricted to a minority of cells and modulated by the interplay of restraining physical microenvironmental cues and activating IL-1β-dependent stroma-to-MM crosstalk.

Decoding changes in tumor-infiltrating leukocytes through dynamic experimental models and single-cell technologies

The ability to characterize immune cells and explore the molecular interactions that govern their functions has never been greater, fueled in recent years by the revolutionary advance of single-cell analysis platforms. However, precisely how immune cells respond to different stimuli and where differentiation processes and effector functions operate remain incompletely understood. Inferring cellular fate within single-cell transcriptomic analyses is now omnipresent, despite the assumptions typically required in such analyses. Recently developed experimental models support dynamic analyses of the immune response, providing insights into the temporal changes that occur within cells and the tissues in which such transitions occur. Here we will review these approaches and discuss how these can be combined with single-cell technologies to develop a deeper understanding of the immune responses that should support the development of better therapeutic options for patients.

Advancements in microenvironment-based therapies: transforming the landscape of multiple myeloma treatment

Multiple myeloma (MM) is the most prevalent malignant monoclonal disease of plasma cells. There is mounting evidence that interactions with the bone marrow (BM) niche are essential for the differentiation, proliferation, survival, migration, and treatment resistance of myeloma cells. For this reason, gaining a deeper comprehension of how BM microenvironment compartments interact with myeloma cells may inspire new therapeutic ideas that enhance patient outcomes. This review will concentrate on the most recent findings regarding the mechanisms of interaction between microenvironment and MM and highlight research on treatment targeting the BM niche.