Identification of MS4A3 as a reliable marker for early myeloid differentiation in human hematopoiesis

MS4A3 regulates hematopoietic myeloid differentiation through ROS/TGF-β/p38MAPK pathway

The hematopoietic homeostasis relies on the intricate regulation of hematopoietic stem cells during their proliferation and differentiation. Myeloid differentiation disorders can lead to chronic myeloid leukemia and acute myeloid leukemia. Previous studies have shown increased expression of MS4A3 in myeloid cells, suggesting that MS4A3 may play a critical role in hematopoietic myeloid differentiation. However, the underlying mechanism and its role in hematopoietic myeloid differentiation require further elucidation. In this study, using K562 cell lines with MS4A3 over-expression (oeMS4A3) and MS4A3 knockdown (shMS4A3), we demonstrated that the overexpression of MS4A3 resulted in an augmented skewing towards myeloid differentiation and cell cycle arrest at G0/G1. In addition, inhibition of ROS, TGF-β, and p38MAPK in oeMS4A3 K562 cells attenuated the skewing of myeloid differentiation. Furthermore, in vivo experiments revealed a slight myeloid differentiation suppression tendency in MS4A3 knockout mice. Taken together, we show that MS4A3 overexpression promote myeloid differentiation skewing through the activation of the ROS/p38MAPK/TGFβ pathway. This study underscored the role of MS4A3 in the hematopoietic myeloid differentiation.

CREB-binding protein/P300 bromodomain inhibition reduces neutrophil accumulation and activates antitumor immunity in triple-negative breast cancer

Tumor-associated neutrophils (TANs) have been shown to promote immunosuppression and tumor progression, and a high TAN frequency predicts poor prognosis in triple-negative breast cancer (TNBC). Dysregulation of CREB-binding protein (CBP)/P300 function has been observed with multiple cancer types. The bromodomain (BRD) of CBP/P300 has been shown to regulate its activity. In this study, we found that IACS-70654, a selective CBP/P300 BRD inhibitor, reduced TANs and inhibited the growth of neutrophil-enriched TNBC models. In the bone marrow, CBP/P300 BRD inhibition reduced the tumor-driven abnormal differentiation and proliferation of neutrophil progenitors. Inhibition of CBP/P300 BRD also stimulated the immune response by inducing an IFN response and MHCI expression in tumor cells and increasing tumor-infiltrated cytotoxic T cells. Moreover, IACS-70654 improved the response of a neutrophil-enriched TNBC model to docetaxel and immune checkpoint blockade. This provides a rationale for combining a CBP/P300 BRD inhibitor with standard-of-care therapies in future clinical trials for neutrophil-enriched TNBC.

CBP/P300 BRD Inhibition Reduces Neutrophil Accumulation and Activates Antitumor Immunity in TNBC

Tumor-associated neutrophils (TANs) have been shown to promote immunosuppression and tumor progression, and a high TAN frequency predicts poor prognosis in triple-negative breast cancer (TNBC). Dysregulation of CREB binding protein (CBP)/P300 function has been observed with multiple cancer types. The bromodomain (BRD) of CBP/P300 has been shown to regulate its activity. In this study, we found that IACS-70654, a novel and selective CBP/P300 BRD inhibitor, reduced TANs and inhibited the growth of neutrophil-enriched TNBC models. In the bone marrow, CBP/P300 BRD inhibition reduced the tumor-driven abnormal differentiation and proliferation of neutrophil progenitors. Inhibition of CBP/P300 BRD also stimulated the immune response by inducing an IFN response and MHCI expression in tumor cells and increasing tumor-infiltrated CTLs. Moreover, IACS-70654 improved the response of a neutrophil-enriched TNBC model to docetaxel and immune checkpoint blockade. This provides a rationale for combining a CBP/P300 BRD inhibitor with standard-of-care therapies in future clinical trials for neutrophil-enriched TNBC.

Host factor TIMP1 sustains long-lasting myeloid-biased hematopoiesis after severe infection

Infection is able to promote innate immunity by enhancing a long-term myeloid output even after the inciting infectious agent has been cleared. However, the mechanisms underlying such a regulation are not fully understood. Using a mouse polymicrobial peritonitis (sepsis) model, we show that severe infection leads to increased, sustained myelopoiesis after the infection is resolved. In post-infection mice, the tissue inhibitor of metalloproteinases 1 (TIMP1) is constitutively upregulated. TIMP1 antagonizes the function of ADAM10, an essential cleavage enzyme for the activation of the Notch signaling pathway, which suppresses myelopoiesis. While TIMP1 is dispensable for myelopoiesis under the steady state, increased TIMP1 enhances myelopoiesis after infection. Thus, our data establish TIMP1 as a molecular reporter of past infection in the host, sustaining hyper myelopoiesis and serving as a potential therapeutic target for modulating HSPC cell fate.

Genotoxic aldehyde stress prematurely ages hematopoietic stem cells in a p53-driven manner

Aged hematopoietic stem cells (HSCs) display diminished self-renewal and a myeloid differentiation bias. However, the drivers and mechanisms that underpin this fundamental switch are not understood. HSCs produce genotoxic formaldehyde that requires protection by the detoxification enzymes ALDH2 and ADH5 and the Fanconi anemia (FA) DNA repair pathway. We find that the HSCs in young Aldh2-/-Fancd2-/- mice harbor a transcriptomic signature equivalent to aged wild-type HSCs, along with increased epigenetic age, telomere attrition, and myeloid-biased differentiation quantified by single HSC transplantation. In addition, the p53 response is vigorously activated in Aldh2-/-Fancd2-/- HSCs, while p53 deletion rescued this aged HSC phenotype. To further define the origins of the myeloid differentiation bias, we use a GFP genetic reporter to find a striking enrichment of Vwf+ myeloid and megakaryocyte-lineage-biased HSCs. These results indicate that metabolism-derived formaldehyde-DNA damage stimulates the p53 response in HSCs to drive accelerated aging.

Osteoprogenitor-GMP crosstalk underpins solid tumor-induced systemic immunosuppression and persists after tumor removal

Remote tumors disrupt the bone marrow (BM) ecosystem (BME), eliciting the overproduction of BM-derived immunosuppressive cells. However, the underlying mechanisms remain poorly understood. Herein, we characterized breast and lung cancer-induced BME shifts pre- and post-tumor removal. Remote tumors progressively lead to osteoprogenitor (OP) expansion, hematopoietic stem cell dislocation, and CD41- granulocyte-monocyte progenitor (GMP) aggregation. The tumor-entrained BME is characterized by co-localization between CD41- GMPs and OPs. OP ablation abolishes this effect and diminishes abnormal myeloid overproduction. Mechanistically, HTRA1 carried by tumor-derived small extracellular vesicles upregulates MMP-13 in OPs, which in turn induces the alterations in the hematopoietic program. Importantly, these effects persist post-surgery and continue to impair anti-tumor immunity. Conditional knockout or inhibition of MMP-13 accelerates immune reinstatement and restores the efficacies of immunotherapies. Therefore, tumor-induced systemic effects are initiated by OP-GMP crosstalk that outlasts tumor burden, and additional treatment is required to reverse these effects for optimal therapeutic efficacy.

DNA Methylation and Gene Expression in Blood and Adipose Tissue of Adult Offspring of Women with Diabetes in Pregnancy—A Validation Study of DNA Methylation Changes Identified in Adolescent Offspring

Maternal gestational diabetes and obesity are associated with adverse outcomes in offspring, including increased risk of diabetes and cardiovascular diseases. Previously, we identified a lower DNA methylation degree at genomic sites near the genes ESM1, MS4A3, and TSPAN14 in the blood cells of adolescent offspring exposed to gestational diabetes and/or maternal obesity in utero. In the present study, we aimed to investigate if altered methylation and expression of these genes were detectable in blood, as well in the metabolically relevant subcutaneous adipose tissue, in a separate cohort of adult offspring exposed to gestational diabetes and obesity (O-GDM) or type 1 diabetes (O-T1D) in utero, compared with the offspring of women from the background population (O-BP). We did not replicate the findings of lower methylation of ESM1, MS4A3, and TSPAN14 in blood from adults, either in O-GDM or O-T1D. In contrast, in adipose tissue of O-T1D, we found higher MS4A3 DNA methylation, which will require further validation. The adipose tissue ESM1 expression was lower in O-GDM compared to O-BP, which in turn was not associated with maternal pre-pregnancy BMI nor the offspring’s own adiposity. Adipose tissue TSPAN14 expression was slightly lower in O-GDM compared with O-BP, but also positively associated with maternal pre-pregnancy BMI, as well as offspring’s own adiposity and HbA1c levels. In conclusion, the lower DNA methylation in blood from adolescent offspring exposed to GDM could not be confirmed in the present cohort of adult offspring, potentially due to methylation remodeling with increased aging. In offspring adipose tissue, ESM1 expression was associated with maternal GDM, and TSPAN14 expression was associated with both maternal GDM, as well as pre-pregnancy BMI. These altered expression patterns are potentially relevant to the concept of developmental programming of cardiometabolic diseases and require further studies.

Differential expression and regulation of MS4A family members in myeloid cells in physiological and pathological conditions

The MS4A gene family encodes 18 tetraspanin-like proteins, most of which with unknown function. MS4A1 (CD20), MS4A2 (FcεRIβ), MS4A3 (HTm4), and MS4A4A play important roles in immunity, whereas expression and function of other members of the family are unknown. The present investigation was designed to obtain an expression fingerprint of MS4A family members, using bioinformatics analysis of public databases, RT-PCR, and protein analysis when possible. MS4A3, MS4A4A, MS4A4E, MS4A6A, MS4A7, and MS4A14 were expressed by myeloid cells. MS4A6A and MS4A14 were expressed in circulating monocytes and decreased during monocyte-to-Mϕ differentiation in parallel with an increase in MS4A4A expression. Analysis of gene expression regulation revealed a strong induction of MS4A4A, MS4A6A, MS4A7, and MS4A4E by glucocorticoid hormones. Consistently with in vitro findings, MS4A4A and MS4A7 were expressed in tissue Mϕs from COVID-19 and rheumatoid arthritis patients. Interestingly, MS4A3, selectively expressed in myeloid precursors, was found to be a marker of immature circulating neutrophils, a cellular population associated to COVID-19 severe disease. The results reported here show that members of the MS4A family are differentially expressed and regulated during myelomonocytic differentiation, and call for assessment of their functional role and value as therapeutic targets.

MS4A3 promotes differentiation in chronic myeloid leukemia by enhancing common β-chain cytokine receptor endocytosis

The chronic phase of chronic myeloid leukemia (CP-CML) is characterized by the excessive production of maturating myeloid cells. As CML stem/progenitor cells (LSPCs) are poised to cycle and differentiate, LSPCs must balance conservation and differentiation to avoid exhaustion, similar to normal hematopoiesis under stress. Since BCR-ABL1 tyrosine kinase inhibitors (TKIs) eliminate differentiating cells but spare BCR-ABL1-independent LSPCs, understanding the mechanisms that regulate LSPC differentiation may inform strategies to eliminate LSPCs. Upon performing a meta-analysis of published CML transcriptomes, we discovered that low expression of the MS4A3 transmembrane protein is a universal characteristic of LSPC quiescence, BCR-ABL1 independence, and transformation to blast phase (BP). Several mechanisms are involved in suppressing MS4A3, including aberrant methylation and a MECOM-C/EBPε axis. Contrary to previous reports, we find that MS4A3 does not function as a G1/S phase inhibitor but promotes endocytosis of common β-chain (βc) cytokine receptors upon GM-CSF/IL-3 stimulation, enhancing downstream signaling and cellular differentiation. This suggests that LSPCs downregulate MS4A3 to evade βc cytokine-induced differentiation and maintain a more primitive, TKI-insensitive state. Accordingly, knockdown (KD) or deletion of MS4A3/Ms4a3 promotes TKI resistance and survival of CML cells ex vivo and enhances leukemogenesis in vivo, while targeted delivery of exogenous MS4A3 protein promotes differentiation. These data support a model in which MS4A3 governs response to differentiating myeloid cytokines, providing a unifying mechanism for the differentiation block characteristic of CML quiescence and BP-CML. Promoting MS4A3 reexpression or delivery of ectopic MS4A3 may help eliminate LSPCs in vivo.

Transcription factor MEF2D is required for the maintenance of MLL-rearranged acute myeloid leukemia

MEF2D is highly expressed in MLL-rearranged AML and required for leukemia development in vitro and in vivo.

MEF2D suppresses CEBPE-mediated myeloid differentiation in AML.

Acute myeloid leukemia (AML) with MLL-rearrangement (MLL-r) comprises ∼10% of all AML cases and portends poor outcomes. Much remains uncovered on how MLL-r AML drives leukemia development while preventing cells from normal myeloid differentiation. Here, we identified that transcription factor MEF2D is a super-enhancer-associated, highly expressed gene in MLL-r AML. Knockout of MEF2D profoundly impaired leukemia growth, induced myeloid differentiation, and delayed oncogenic progression in vivo. Mechanistically, MEF2D loss led to robust activation of a CEBPE-centered myeloid differentiation program in AML cells. Chromatin profiling revealed that MEF2D binds to and suppresses the chromatin accessibility of CEBPE cis-regulatory regions. In human acute leukemia samples, MEF2D expression showed a strong negative correlation with the expression of CEBPE. Depletion of CEBPE partially rescued the cell growth defect and myeloid cell differentiation induced by the loss of MEF2D. Lastly, we show that MEF2D is positively regulated by HOXA9, and downregulation of MEF2D is an important mechanism for DOT1L inhibitor-induced antileukemia effects. Collectively, our findings suggest that MEF2D plays a critical role in human MLL-r AML and uncover the MEF2D-CEBPE axis as a crucial transcriptional mechanism regulating leukemia cell self-renewal and differentiation block.

MS4A3-HSP27 target pathway reveals potential for haematopoietic disorder treatment in alimentary toxic aleukia

Alimentary toxic aleukia (ATA) is correlated with consuming grains contaminated by Fusarium species, particularly T-2 toxin, which causes serious hurt to human and animal health, chiefly in disorders of the haematopoietic system. However, the mechanism of haematopoietic dysfunction induced by T-2 toxin and the possible target pathway for the treatment of T-2 toxin-induced haematopoietic disorder of ATA remains unclear. In this study, genomes and proteomics were used for the first time to investigate the key differential genes and proteins that inhibit erythroid differentiation of K562 cells caused by T-2 toxin, and it was found that heat shock protein 27 (HSP27) and membrane-spanning 4-domains, subfamily A, member 3 (MS4A3) may play an important role in erythroid differentiation. Meanwhile, MS4A3 interference can inhibit the occurrence of erythroid differentiation of K562 cells and promote the phosphorylation of HSP27. Moreover, the binding of HSP27 to MS4A3 in natural state can activate the phosphorylation site of HSP27 (Ser-83), while T-2 toxin can abolish the activation of phosphorylation site by inhibiting the expression of MS4A3. These findings for the first time demonstrated that the MS4A3-HSP27 pathway may function an efficient therapeutic target pathway for treating T-2 toxin elicited haematopoietic disorders of ATA.

HES1 and HES4 have non-redundant roles downstream of Notch during early human T-cell development

In both mouse and human, Notch1 activation is the main initial driver to induce T-cell development in hematopoietic progenitor cells. The initiation of this developmental process coincides with Notch1-dependent repression of differentiation towards other hematopoietic lineages. Although well described in mice, the role of the individual Notch1 target genes during these hematopoietic developmental choices is still unclear in human, particularly for HES4 since no orthologous gene is present in the mouse. Here, we investigated the functional capacity of the Notch1 target genes HES1 and HES4 to modulate human Notch1-dependent hematopoietic lineage decisions and their requirement during early T-cell development. We show that both genes are upregulated in a Notch-dependent manner during early T-cell development and that HES1 acts as a repressor of differentiation by maintaining a quiescent stem cell signature in CD34+ hematopoietic progenitor cells. While HES4 can also inhibit natural killer and myeloid cell development like HES1, it acts differently on the T- versus B-cell lineage choice. Surprisingly, HES4 is not capable of repressing B-cell development, the most sensitive hematopoietic lineage with respect to Notch-mediated repression. In contrast to HES1, HES4 promotes initiation of early T-cell development, but ectopic expression of HES4, or HES1 and HES4 combined, is not sufficient to induce T-lineage differentiation. Importantly, knockdown of HES1 or HES4 significantly reduces human T-cell development. Overall, we show that the Notch1 target genes HES1 and HES4 have non-redundant roles during early human T-cell development which may relate to differences in mediating Notch-dependent human hematopoietic lineage decisions.

Proteomic analysis of young and old mouse hematopoietic stem cells and their progenitors reveals post-transcriptional regulation in stem cells

The balance of hematopoietic stem cell (HSC) self-renewal and differentiation is critical for a healthy blood supply; imbalances underlie hematological diseases. The importance of HSCs and their progenitors have led to their extensive characterization at genomic and transcriptomic levels. However, the proteomics of hematopoiesis remains incompletely understood. Here we report a proteomics resource from mass spectrometry of mouse young adult and old adult mouse HSCs, multipotent progenitors and oligopotent progenitors; 12 cell types in total. We validated differential protein levels, including confirmation that Dnmt3a protein levels are undetected in young adult mouse HSCs until forced into cycle. Additionally, through integrating proteomics and RNA-sequencing datasets, we identified a subset of genes with apparent post-transcriptional repression in young adult mouse HSCs. In summary, we report proteomic coverage of young and old mouse HSCs and progenitors, with broader implications for understanding mechanisms for stem cell maintenance, niche interactions and fate determination.

Different Innate Immune Responses in BALB/c and C57BL/6 Strains following Corneal Transplantation

PURPOSE

To investigate immunological differences and the role of CD38+/F4/80 + M1 macrophages in C57BL/6J- and BALB/c-recipient mouse corneal transplantation models.

METHODS

Allogeneic transplantation was performed crosswise in BALB/c mice and C57BL/6J mice; syngeneic transplantation was performed in both strains. Anterior chamber depth (ACD) was measured before and central corneal thickness (CCT) was measured both before and after transplantation. In vivo graft rejection was monitored using anterior eye segment optical coherence tomography (ASOCT) evaluating the CCT and grading of corneal oedema using a well-established clinical score (CS). Histology of corneal grafts was performed 18 or 21 days after surgery. Immunohistochemistry with anti-F4/80 antibody and anti-CD38 antibody was used for detecting M1 macrophages within the grafts.

RESULTS

High CS and CCT values after allogeneic transplantation persisted in both BALB/c (n = 18) and C57BL/6J recipients (n = 20). After syngeneic transplantation, CS and CCT values increased in both models in the early phase after surgery due to the surgical trauma. Surprisingly, in the syngeneic C57BL/6J model, high CCT values persisted. Furthermore, anterior synechiae developed in C57BL/6 recipients after both syngeneic and allogeneic transplantation, whereas BALB/c recipients showed almost no synechiae - even though C57/BL6J animals tended to have a deeper anterior chamber (281 ± 11 pixels [mean ± SD]) compared with BALB/c animals of the same age (270 ± 9 pixels [mean ± SD]). Immunohistochemistry revealed numerous CD38+/F4/80 + M1 macrophages in grafts of C57BL/6J recipients following both syngeneic and allogeneic transplantation. However, in BALB/c-recipient mice only sparse M1 macrophages were detectable (CD38 + M1 macrophages relative to all F4/80 + cells: 75 vs. 17% [after allogeneic transplantation] and 66 vs. 17% [after syngeneic transplantation]; p < 0.05).

CONCLUSIONS

Allogeneic corneal transplants are rejected in BALB/c as well as C57BL/6J mice, but tissue alterations with anterior synechiae are more pronounced in C57BL/6J recipients. Following syngeneic transplantation, C57BL/6J-recipient animals show a persistent graft swelling with increased numbers of CD38+/F4/80 + M1 macrophages in grafted tissue, in contrast to the common model using BALB/c-recipient mice. Our data strongly suggest that strain-dependent differences convey different innate immune responses in BALB/c and C57BL/6J strains. Accordingly, in murine keratoplasty experiments, the mouse line of both donor and recipient animals must be carefully considered. C57BL/6J-recipient mice might be particularly suited to study corneal graft rejection in a clinical setting considered "high risk."

PML Nuclear Body Biogenesis, Carcinogenesis, and Targeted Therapy

Targeted therapy has become increasingly important in cancer therapy. For example, targeting the promyelocytic leukemia PML protein in leukemia has proved to be an effective treatment. PML is the core component of super-assembled structures called PML nuclear bodies (NBs). Although this nuclear megaDalton complex was first observed in the 1960s, the mechanism of its assembly remains poorly understood. We review recent breakthroughs in the PML field ranging from a revised assembly mechanism to PML-driven genome organization and carcinogenesis. In addition, we highlight that oncogenic oligomerization might also represent a promising target in the treatment of leukemias and solid tumors.

Single-cell transcriptomic landscape of nucleated cells in umbilical cord blood

BACKGROUND

For both pediatric and adult patients, umbilical cord blood (UCB) transplant is a therapeutic option for a variety of hematologic diseases, such as blood cancers, myeloproliferative disorders, genetic diseases, and metabolic disorders. However, the level of cellular heterogeneity and diversity of nucleated cells in UCB has not yet been assessed in an unbiased and systemic fashion. In the present study, nucleated cells from UCB were subjected to single-cell RNA sequencing to simultaneously profile the gene expression signatures of thousands of cells, generating a rich resource for further functional studies. Here, we report the transcriptomes of 17,637 UCB cells, covering 12 major cell types, many of which can be further divided into distinct subpopulations.

RESULTS

Pseudotemporal ordering of nucleated red blood cells identifies wave-like activation and suppression of transcription regulators, leading to a polarized cellular state, which may reflect nucleated red blood cell maturation. Progenitor cells in UCB also comprise 2 subpopulations with activation of divergent transcription programs, leading to specific cell fate commitment. Detailed profiling of cytotoxic cell populations unveiled granzymes B and K signatures in natural killer and natural killer T-cell types in UCB.

CONCLUSIONS

Taken together, our data form a comprehensive single-cell transcriptomic landscape that reveals previously unrecognized cell types, pathways, and mechanisms of gene expression regulation. These data may contribute to the efficacy and outcome of UCB transplant, broadening the scope of research and clinical innovations.

SATB family chromatin organizers as master regulators of tumor progression

SATB (Special AT-rich binding protein) family proteins have emerged as key regulators that integrate higher-order chromatin organization with the regulation of gene expression. Studies over the past decade have elucidated the specific roles of SATB1 and SATB2, two closely related members of this family, in cancer progression. SATB family chromatin organizers play diverse and important roles in regulating the dynamic equilibrium of apoptosis, cell invasion, metastasis, proliferation, angiogenesis, and immune modulation. This review highlights cellular and molecular events governed by SATB1 influencing the structural organization of chromatin and interacting with several co-activators and co-repressors of transcription towards tumor progression. SATB1 expression across tumor cell types generates cellular and molecular heterogeneity culminating in tumor relapse and metastasis. SATB1 exhibits dynamic expression within intratumoral cell types regulated by the tumor microenvironment, which culminates towards tumor progression. Recent studies suggested that cell-specific expression of SATB1 across tumor recruited dendritic cells (DC), cytotoxic T lymphocytes (CTL), T regulatory cells (Tregs) and tumor epithelial cells along with tumor microenvironment act as primary determinants of tumor progression and tumor inflammation. In contrast, SATB2 is differentially expressed in an array of cancer types and is involved in tumorigenesis. Survival analysis for patients across an array of cancer types correlated with expression of SATB family chromatin organizers suggested tissue-specific expression of SATB1 and SATB2 contributing to disease prognosis. In this context, it is pertinent to understand molecular players, cellular pathways, genetic and epigenetic mechanisms governed by cell types within tumors regulated by SATB proteins. We propose that patient survival analysis based on the expression profile of SATB chromatin organizers would facilitate their unequivocal establishment as prognostic markers and therapeutic targets for cancer therapy.