Biology subjects

Ponzoni, M.

Publications and source records attributed to Ponzoni, M..

6 recordsLinked to original sources

bioRxiv2026

A genetic anemia disentangles the dual effect of chronically reduced thrombopoietin on hematopoietic stem cells and bone marrow niche

Many studies unraveled the reciprocal regulation between hematopoietic stem cells (HSC) and the bone marrow (BM) niche by using transgenic knock-out or reporter mice, often overlooking the pathophysiological relevance and the existence of compensatory mechanisms. Here, we exploit the th3 murine model of a genetic anemia, beta-thalassemia (BThal), to investigate the dual impact of chronically reduced thrombopoietin (TPO) production on HSC and megakaryocytic BM niche. Decreased systemic TPO downregulates stemness programs in HSC and impairs their commitment towards megakaryocytes (Mk). We uncover dysmegakaryopoiesis in the BM from BThal patients and mice with defective Mk maturation and reduced production of niche factors, altering the HSC-niche crosstalk. Notably, in vivo stimulation of the TPO signaling restores HSC quiescence, Mk maturation and niche support. These findings demonstrate that TPO regulates HSC through both direct and niche-mediated routes, underscoring the value of using a genetic disease model to disentangle general molecular mechanisms.

cell biology↗

bioRxiv2026

Spatial multi-omics identify an immunosuppressive lipid-laden macrophage niche in primary CNS lymphoma

Primary central nervous system lymphoma (PCNSL) is histologically a subtype of diffuse large B-cell lymphoma (DLBCL), sharing genetic and transcriptomic similarity, but with distinct clinical features, particularly its confinement to the CNS and higher relapse risk. The microenvironmental basis for its divergence from systemic DLBCL remains unclear. Using spatial transcriptomic approaches (Xenium/GeoMx digital spatial profiling) in a comparative study of PCNSL (n=17) and DLBCL (n=76), we found that PCNSL, unlike systemic DLBCL, is dominated by an immunosuppressive macrophage compartment enriched for cholesterol-metabolism programs. In independent cohorts of PCNSL profiled by single-cell RNA sequencing, we validated the presence of a recurrent population of lipid-laden macrophages (LLMs): TREM2/GPNMB-expressing, lipid-remodeled cells transcriptionally distinct from resident microglia and consistent with an infiltrating monocyte origin, not previously characterized in CNS lymphoma. LLMs formed immunosuppressive niches with regulatory T cells, and using Cellscape hyperplex proteomic imaging we demonstrate that LLM-Treg spatial interactions are associated with chemotherapy response. To test whether LLMs are lymphoma-driven and functionally important, we developed an immunocompetent syngeneic PCNSL mouse model, driven by Myd88L252P and Cd79b mutations with Bcl2 overexpression. Monocyte-derived macrophages in lymphoma-bearing brain regions acquired an LLM-like state, not seen in lymphoma-free brain regions or in splenic tumors driven by the same oncogenic lesions. TREM2-SYK signaling sustained this state, and SYK inhibition reversed its tumor-supportive activity ex vivo. These findings identify the LLM program as a targetable immunosuppressive myeloid state in CNS lymphoma.

cancer biology↗

bioRxiv2024

B cell receptor silencing reveals the origin of high-grade B cell lymphomas with MYC and BCL2 rearrangements

The B cell receptor (BCR) is essential for mature B cell lymphomas, serving as therapeutic target. Here, we show that high-grade B cell lymphomas with MYC and BCL2 rearrangements (HGBCL-DH-BCL2) predominantly exhibit immunoglobulin heavy (IGH) chain silencing, leading to BCR shutdown. HGBCL-DH-BCL2 with undetectable IGH (IGHUND) differ from IGH-expressing counterparts for germinal center-zone gene programs, MYC expression and T cell infiltration. While IGH+ HGBCL-DH-BCL2 prefer IGM/IG-Kappa expression, IGHUND counterparts have completed IGH class-switching, favoring IG-Lambda (IGL) light chains. IGHUND HGBCL-DH-BCL2 preserve IGHV gene integrity, overcoming antigen-driven selection. IGH silencing precedes onset and shapes evolution of HGBCL-DH-BCL2 from Follicular Lymphoma (FL) or FL/HGBCL-DH-BCL2 common precursor. In FL/HGBCL-DH-BCL2 pairs and HGBCL-DH-BCL2 models, BCR silencing promoted RAG1/2-dependent IG light chain editing, causing t(8;22)(q24;q11)/IGL::MYC. IGH silencing protected HGBCL-DH-BCL2 models from killing by CD79B-targeting Polatuzumab-Vedotin. Collectively, HGBCL-DH-BCL2 primarily originate from BCR-silenced isotype-switched t(14;18)/IGH::BCL2-positive (pre)FL cells acquiring IGL::MYC translocations during IG light chain revision, with clinical implications. SignificanceThese findings link BCR silencing in isotype-switched t(14;18)+ Follicular Lymphoma cells (or their precursors) to RAG1/2 re-expression, promoting IGL::MYC translocations responsible for transformation into high-grade B cell lymphomas (HGBCL). Predominant silencing of the BCR complex in HGBCL with MYC and BCL2 rearrangements protects tumor cells from CD79B-directed Polatuzumab-Vedotin killing.

cancer biology↗

bioRxiv2023

ZEB1 shapes AML immunological niches suppressing CD8 T-cell activity while fostering Th17 cell expansion.

Acute myeloid leukemia (AML) development and progression is favored by immune suppression directly triggered by leukemia cells. ZEB1 is a key transcription factor in epithelial-to-mesenchymal transition which, we show here, is capable immune regulation in AML. Leukemic cells which had ZEB1 knocked down have reduced engraftment and extramedullary disease when transplanted into immune competent mice due to concomitant activation of CD8 T lymphocytes and reduced expansion of Th17 cells. Differently, in ZEB1 competent AML, IL-17 sustains the development of a pro-invasive and self-maintaining loop inducing MMPs and SOCS2. In humans, AML patients show, in situ on bone marrow biopsies, a direct correlation between ZEB1 and Th17 and, in gene expression profile when divided according to the median value of ZEB1 expression, a different overall survival and relapse along with the expression of MMPs, SOCS2 and Th17 cells enrichment. Overall, our data shed new light into the role of ZEB1 in AML that entwines both pro-tumoral and immune regulatory capacity in AML blasts.

immunology↗

bioRxiv2021

Neutrophil extracellular traps arm DC vaccination against NPM-mutant myeloproliferation

Neutrophil extracellular traps (NET) are web-like chromatin structures composed by dsDNA and histones, decorated with anti-microbial proteins. Their interaction with dendritic cells (DC) allows DC activation and maturation toward presentation of NET-associated antigens. Differently from other types of cell death that imply protein denaturation, NETosis preserves the proteins localized onto the DNA threads for proper enzymatic activity and conformational status, including immunogenic epitopes. Besides neutrophils, leukemic cells can release extracellular traps displaying leukemia-associated antigens, prototypically mutant nucleophosmin (NPMc+) that upon mutation translocates from nucleolus to the cytoplasm localizing onto NET threads. We tested NPMc+ immunogenicity through a NET/DC vaccine to treat NPMc-driven myeloproliferation in transgenic and transplantable models. Vaccination with DC loaded with NPMc+ NET (NPMc+ NET/DC) reduced myeloproliferation in transgenic mice, favoring the development of antibodies to mutant NPMc and and the induction of a CD8+ T cell response. The efficacy of this vaccine was also tested in mixed NPMc/WT bone marrow chimeras in a competitive bone marrow transplantation setting, where the NPMc+ NET/DC vaccination impaired the expansion of NPMc+ in favor of WT myeloid compartment. NPMc+ NET/DC vaccination also achieved control of an aggressive leukemia transduced with mutant NPMc, effectively inducing an anti-leukemia CD8 T cell memory response. eTOC SummaryNPMc is an AML-triggering mutation inducing translocation of NPM into the cytoplasm, allowing its association to NET threads. On NET, NPMc becomes immunogenic acting as an alarmin and exposing immunogenic peptides. We demonstrate that NET can be exploited as anti-tumor weapons in DC-based vaccination strategies.

immunology↗

bioRxiv2020

Intra-tumor heterogeneity of Diffuse Large B-cell Lymphoma involves the induction of diversified stroma-tumor interfaces

Intra-tumor heterogeneity in lymphoid malignancies is articulated around several fundamentals, encompassing selection of genetic subclonal events and epigenetic regulation of transcriptional programs. Clonally-related neoplastic cell populations are unsteadily subjected to immune editing and metabolic adaptations within different tissue microenvironments. How tissue-intrinsic mesenchymal determinants impact on the diversification of aggressive lymphomas is still unknown. In this study we adopted the established A20 line-based model of Diffuse Large B-cell Lymphoma (DLBCL), to investigate the intra-tumor heterogeneity associated with the infiltration of different tissue microenvironments and the specific mesenchymal modifications that characterize stromal adaptation to lymphoma seeding. Combining in situ quantitative immunophenotypical analyses and RNA sequencing, we found that the tissue microenvironment casts a relevant influence over A20 transcriptional landscape also impacting on Myc and DNA damage response programs. Extending the investigation to mice deficient for the matricellular protein Sparc, a stromal determinant endowed with a strong prognostic significance in human DLBCL, we demonstrated a different immune imprint on A20 cells related to stromal Sparc proficiency. The study provides the first evidence of human DLBCL intra-lesional heterogeneity arising from diversified mesenchymal contextures and impacting on MYC expression, advancing the challenge for resolving intra-tumor heterogeneity probing stromal/immune interfaces. KEY POINTSO_LIDiversified stromal adaptations of infiltrated tissues shape DLBCL intra-tumor heterogeneity regulating transcriptional/phenotypic features C_LIO_LIStromal Sparc, which endorses prognostic significance in DLBCL, tunes the immune pressure exerted on lymphoma cells by the microenvironment C_LI

cancer biology↗