Leukemic marrow infiltration reveals a novel role for Egr3 as a potent inhibitor of normal hematopoietic stem cell proliferation

EV-mediated intercellular communication in acute myeloid leukemia: Transport of genetic materials in the bone marrow microenvironment

Acute myeloid leukemia (AML) is a common hematological cancer. Cancer cells exchange information with the surrounding microenvironment, which can be transmitted by extracellular vesicles (EVs). In recent years, the genetic materials transported by EVs have attracted attention due to their important roles in different pathological processes. EV-derived ncRNAs (EV-ncRNAs) regulate physiological functions and maintain homeostasis, mainly including microRNAs, long noncoding RNAs, and circular RNAs. However, the mechanism of involvement and potential clinical application of EV-ncRNAs in AML have not been reported. Given the unique importance of the bone marrow microenvironment (BMME) for AML, a greater understanding of the communication between leukemic cells and the BMME is needed to improve the prognosis of patients and reduce the incidence of recurrence. Additionally, studies on leukemic EV-ncRNA transport guide the design of new diagnostic and therapeutic tools for AML. This review systematically describes intercellular communication in the BMME of AML and emphasizes the role of EVs. More importantly, we focus on the information transmission of EV-ncRNAs in the BMME to explore their clinical application as potential biomarkers and therapeutic targets.

Rescue of cardiac dysfunction during chemotherapy in acute myeloid leukaemia by blocking IL-1α

BACKGROUND AND AIMS

Patients with acute myeloid leukaemia (AML) suffer from severe myocardial injury during daunorubicin (DNR)-based chemotherapy and are at high risk of cardiac mortality. The crosstalk between tumour cells and cardiomyocytes might play an important role in chemotherapy-related cardiotoxicity, but this has yet to be demonstrated. This study aimed to identify its underlying mechanism and explore potential therapeutic targets.

METHODS

Cardiac tissues were harvested from an AML patient after DNR-based chemotherapy and were subjected to single-nucleus RNA sequencing. Cardiac metabolism and function were evaluated in AML mice after DNR treatment by using positron emission tomography, magnetic resonance imaging, and stable-isotope tracing metabolomics. Plasma cytokines were screened in AML mice after DNR treatment. Genetically modified mice and cell lines were used to validate the central role of the identified cytokine and explore its downstream effectors.

RESULTS

In the AML patient, disruption of cardiac metabolic homeostasis was associated with heart dysfunction after DNR-based chemotherapy. In AML mice, cardiac fatty acid utilization was attenuated, resulting in cardiac dysfunction after DNR treatment, but these phenotypes were not observed in similarly treated tumour-free mice. Furthermore, tumour cell-derived interleukin (IL)-1α was identified as a primary factor leading to DNR-induced cardiac dysfunction and administration of an anti-IL-1α neutralizing antibody could improve cardiac functions in AML mice after DNR treatment.

CONCLUSIONS

This study revealed that crosstalk between tumour cells and cardiomyocytes during chemotherapy could disturb cardiac energy metabolism and impair heart function. IL-1α neutralizing antibody treatment is a promising strategy for alleviating chemotherapy-induced cardiotoxicity in AML patients.

Iron overload promotes the progression of MLL-AF9 induced acute myeloid leukemia by upregulation of FOS

Systemic iron overload is a common clinical challenge leading to significantly serious complications in patients with acute myeloid leukemia (AML), which affects both the quality of life and the overall survival of patients. Symptoms can be relieved after iron chelation therapy in clinical practice. However, the roles and mechanisms of iron overload on the initiation and progression of leukemia remain elusive. Here we studied the correlation between iron overload and AML clinical outcome, and further explored the role and pathophysiologic mechanism of iron overload in AML by using two mouse models: an iron overload MLL-AF9-induced AML mouse model and a nude xenograft mouse model. Patients with AML had an increased ferritin level, particularly in the myelomonocytic (M4) or monocytic (M5) subtypes. High level of iron expression correlated with a worsened prognosis in AML patients and a shortened survival time in AML mice. Furthermore, iron overload increased the tumor load in the bone marrow (BM) and extramedullary tissues by promoting the proliferation of leukemia cells through the upregulation of FOS. Collectively, our findings provide new insights into the roles of iron overload in AML. Additionally, this study may provide a potential therapeutic target to improve the outcome of AML patients and a rationale for the prospective evaluation of iron chelation therapy in AML.

Intravital Microscopy to Study the Effect of Matrix Metalloproteinase Inhibition on Acute Myeloid Leukemia Cell Migration in the Bone Marrow

Hematopoiesis is the process through which all mature blood cells are formed and takes place in the bone marrow (BM). Acute myeloid leukemia (AML) is a blood cancer of the myeloid lineage. AML progression causes drastic remodeling of the BM microenvironment, making it no longer supportive of healthy hematopoiesis and leading to clinical cytopenia in patients. Understanding the mechanisms by which AML cells shape the BM to their benefit would lead to the development of new therapeutic strategies. While the role of extracellular matrix (ECM) in solid cancer has been extensively studied during decades, its role in the BM and in leukemia progression has only begun to be acknowledged. In this context, intravital microscopy (IVM) gives the unique insight of direct in vivo observation of AML cell behavior in their environment during disease progression and/or upon drug treatments. Here we describe our protocol for visualizing and analyzing MLL-AF9 AML cell dynamics upon systemic inhibition of matrix metalloproteinases (MMP), combining confocal and two-photon microscopy and focusing on cell migration.

Twenty years of evolution of CML therapy: how the treatment goal is moving from disease to patient

The introduction of imatinib in 2000 opened the era of tyrosine kinase inhibitors (TKIs) for CML therapy and has revolutionized the life expectancy of CML patients, which is now quite like the one of the healthy aged population. Over the last 20 years, both the TKI therapy itself and the objectives have undergone evolutions highlighted and discussed in this review. The main objective of the CML therapy in the first 10 years after TKI introduction was to abolish the disease progression from the chronic to the blastic phase and guarantee the long-term survival of the great majority of patients. In the second 10 years (from 2010 to the present), the main objective of CML therapy moved from survival, considered achieved as a goal, to treatment-free remission (TFR). Two phenomena emerged: no more than 50-60% of CML patients could be candidates for discontinuation and over 50% of them molecularly relapse. The increased cumulative incidence of specific TKI off-target side effects was such relevant to compel to discontinue or reduce the TKI administration in a significant proportion of patients and to avoid a specific TKI in particular settings of patients. Therefore, the treatment strategy must be adapted to each category of patients. What about the patients who do not get or fail the TFR? Should they be compelled to continue the TKIs at the maximum tolerated dose? Alternative strategies based on the principle of minimal effective dose have been tested with success and they are now re-evaluated with more attention, since they guarantee survival and probably a better quality of life, too. Moving from treating the disease to treating the patient is an important change of paradigm. We can say that we are entering a personalized CML therapy, which considers the patients' age, their comorbidities, tolerability, and specific objectives. In this scenario, the new techniques supporting the monitoring of the patients, such as the digital PCR, must be considered. In the present review, we present in deep this evolution and comment on the future perspectives of CML therapy.

Lin- PU.1dim GATA-1- defines haematopoietic stem cells with long-term multilineage reconstitution activity

Despite extensive characterization of the state and function of haematopoietic stem cells (HSCs), the use of transcription factors to define the HSC population is still limited. We show here that the HSC population in mouse bone marrow can be defined by the distinct expression levels of Spi1 and Gata1. By using a double fluorescence knock-in mouse model, PGdKI, in which the expression levels of PU.1 and GATA-1 are indicated by the expression of GFP and mCherry, respectively, we uncover that the HSCs with lymphoid and myeloid repopulating activity are specifically enriched in a Lin- PU.1dim GATA-1- (LPG) cell subset. In vivo competitive repopulation assays demonstrate that bone marrow cells gated by LPG exhibit haematopoietic reconstitution activity which is comparable to that of classical Lin- Sca1+ c-kit+ (LSK). The integrated analysis of single-cell RNA sequence data from LPG and LSK-gated cells reveals that a transcriptional network governed by core TFs contributes to regulation of HSC multipotency. These discoveries provide new clues for HSC characterization and functional study.

Interlukin-4 weakens resistance to stress injury and megakaryocytic differentiation of hematopoietic stem cells by inhibiting Psmd13 expression

Thrombocytopenia is a major and fatal complication in patients with acute myeloid leukemia (AML), which results from disrupted megakaryopoiesis by leukemic niche and blasts. Our previous research revealed that elevated interleukin-4 (IL-4) in AML bone marrow had adverse impact on multiple stages throughout megakaryopoiesis including hematopoietic stem cells (HSCs), but the specific mechanism remains unknown. In the present study, we performed single-cell transcriptome analysis and discovered activated oxidative stress pathway and apoptosis pathway in IL-4Rαhigh versus IL-4Rαlow HSCs. IL-4 stimulation in vitro led to apoptosis of HSCs and down-regulation of megakaryocyte-associated transcription factors. Functional assays displayed higher susceptibility of IL-4Rαhigh HSCs to tunicamycin and irradiation-induced apoptosis, demonstrating their vulnerability to endoplasmic reticulum (ER) stress injury. To clarify the downstream signaling of IL-4, we analyzed the transcriptomes of HSCs from AML bone marrow and found a remarkable down-regulation of the proteasome component Psmd13, whose expression was required for megakaryocytic-erythroid development but could be inhibited by IL-4 in vitro. We knocked down Psmd13 by shRNA in HSCs, and found their repopulating capacity and megakaryocytic differentiation were severely compromised, with increased apoptosis in vivo. In summary, our study uncovered a previous unrecognized regulatory role of IL-4-Psmd13 signaling in anti-stress and megakaryocytic differentiation capability of HSCs.

Sox13 and M2-like leukemia-associated macrophages contribute to endogenous IL-34 caused accelerated progression of acute myeloid leukemia

Interleukin 34 (IL-34) mainly plays physiologic and pathologic roles through the sophisticated multi-ligand signaling system, macrophage colony-stimulating factor (M-CSF, CSF-1)/IL-34-CSF-1R axis, which exhibits functional redundancy, tissue-restriction and diversity. This axis is vital for the survival, differentiation and function of monocytic lineage cells and plays pathologic roles in a broad range of diseases. However, the role of IL-34 in leukemia has not been established. Here MLL-AF9 induced mouse acute myeloid leukemia (AML) model overexpressing IL-34 (MA9-IL-34) was used to explore its role in AML. MA9-IL-34 mice exhibited accelerated disease progression and short survival time with significant subcutaneous infiltration of AML cells. MA9-IL-34 cells showed increased proliferation. In vitro colony forming assays and limiting dilution transplantation experiments demonstrated that MA9-IL-34 cells had elevated leukemia stem cell (LSC) levels. Gene expression microarray analysis revealed a panel of differential expressed genes including Sex-determining region Y (SRY)-box 13 (Sox13). Furthermore, a positive correlation between the expressions of IL-34 and Sox13 was detected human datasets. Knockdown of Sox13 rescued the enhanced proliferation, high LSC level and subcutaneous infiltration in MA9-IL-34 cells. Moreover, more leukemia-associated macrophages (LAMs) were detected in MA9-IL-34 microenvironment. Additionally, those LAMs showed M2-like phenotype since they expressed high level of M2-associated genes and had attenuated phagocytic potential, suggesting that LAMs should also contribute to IL-34 caused adverse phenotypes. Therefore, our findings uncover the intrinsic and microenvironmental mechanisms of IL-34 in AML and broadens the knowledge of M-CSF/IL-34-CSF-1R axis in malignancies.

The EGR3 regulome of infant KMT2A-r acute lymphoblastic leukemia identifies differential expression of B-lineage genes predictive for outcome

KMT2A-rearranged acute lymphoblastic infant leukemia (KMT2A-r iALL) is associated with outsize risk of relapse and relapse mortality. We previously reported strong upregulation of the immediate early gene EGR3 in KMT2A::AFF1 iALL at relapse; now we provide analyses of the EGR3 regulome, which we assessed through binding and expression target analysis of an EGR3-overexpressing t(4;11) cell culture model. Our data identify EGR3 as a regulator of early B-lineage commitment. Principal component analysis of 50 KMT2A-r iALL patients at diagnosis and 18 at relapse provided strictly dichotomous separation of patients based on the expression of four B-lineage genes. Absence of B-lineage gene expression translates to more than two-fold poorer long-term event-free survival. In conclusion, our study presents four B-lineage genes with prognostic significance, suitable for gene expression-based risk stratification of KMT2A-r iALL patients.

Role of the bone marrow vascular niche in chemotherapy for MLL-AF9-induced acute myeloid leukemia

Leukemia stem cells in acute myeloid leukemia (AML) can persist within unique bone marrow niches similar to those of healthy hematopoietic stem cells and resist chemotherapy. In the context of AML, endothelial cells (ECs) are crucial components of these niches that appear to promote malignant expansion despite treatment. To better understand these interactions, we developed a real-time cell cycle-tracking mouse model of AML (Fucci-MA9) with an aim of unraveling why quiescent leukemia cells are more resistant to chemotherapy than cycling cells and proliferate during disease relapse. We found that quiescent leukemia cells were more prone to escape chemotherapy than cycling cells, leading to relapse and proliferation. Importantly, post-chemotherapy resting leukemia cells tended to localize closer to blood vessels. Mechanistically, after chemotherapy, resting leukemia cells interacted with ECs, promoting their adhesion and anti-apoptotic capacity. Further, expression analysis of ECs and leukemia cells during AML, after chemotherapy, and after relapse revealed the potential of suppressing the post-chemotherapy inflammatory response to regulate the functions of leukemia cells and ECs. These findings highlight the role of leukemia cells in evading chemotherapy by seeking refuge near blood vessels and provide important insights and directions for future AML research and treatment.

Motixafortide and G-CSF to mobilize hematopoietic stem cells for autologous transplantation in multiple myeloma: a randomized phase 3 trial

Autologous hematopoietic stem cell transplantation (ASCT) improves survival in multiple myeloma (MM). However, many individuals are unable to collect optimal CD34+ hematopoietic stem and progenitor cell (HSPC) numbers with granulocyte colony-stimulating factor (G-CSF) mobilization. Motixafortide is a novel cyclic-peptide CXCR4 inhibitor with extended in vivo activity. The GENESIS trial was a prospective, phase 3, double-blind, placebo-controlled, multicenter study with the objective of assessing the superiority of motixafortide + G-CSF over placebo + G-CSF to mobilize HSPCs for ASCT in MM. The primary endpoint was the proportion of patients collecting ≥6 × 106 CD34+ cells kg-1 within two apheresis procedures; the secondary endpoint was to achieve this goal in one apheresis. A total of 122 adult patients with MM undergoing ASCT were enrolled at 18 sites across five countries and randomized (2:1) to motixafortide + G-CSF or placebo + G-CSF for HSPC mobilization. Motixafortide + G-CSF enabled 92.5% to successfully meet the primary endpoint versus 26.2% with placebo + G-CSF (odds ratio (OR) 53.3, 95% confidence interval (CI) 14.12-201.33, P < 0.0001). Motixafortide + G-CSF also enabled 88.8% to meet the secondary endpoint versus 9.5% with placebo + G-CSF (OR 118.0, 95% CI 25.36-549.35, P < 0.0001). Motixafortide + G-CSF was safe and well tolerated, with the most common treatment-emergent adverse events observed being transient, grade 1/2 injection site reactions (pain, 50%; erythema, 27.5%; pruritis, 21.3%). In conclusion, motixafortide + G-CSF mobilized significantly greater CD34+ HSPC numbers within two apheresis procedures versus placebo + G-CSF while preferentially mobilizing increased numbers of immunophenotypically and transcriptionally primitive HSPCs. Trial Registration: ClinicalTrials.gov , NCT03246529.

The RNA m6A Reader YTHDF1 Is Required for Acute Myeloid Leukemia Progression

N6-methyladenosine (m6A), the most abundant modification in mRNAs, has been defined as a crucial modulator in the progression of acute myelogenous leukemia (AML). Identification of the key regulators of m6A modifications in AML could provide further insights into AML biology and uncover more effective therapeutic strategies for patients with AML. Here, we report overexpression of YTHDF1, an m6A reader protein, in human AML samples at the protein level with enrichment in leukemia stem cells (LSC). Whereas YTHDF1 was dispensable for normal hematopoiesis in mice, depletion of YTHDF1 attenuated self-renewal, proliferation, and leukemic capacity of primary human and mouse AML cells in vitro and in vivo. Mechanistically, YTHDF1 promoted the translation of cyclin E2 in an m6A-dependent manner. Structure-based virtual screening of FDA-approved drugs identified tegaserod as a potential YTHDF1 inhibitor. Tegaserod blocked the direct binding of YTHDF1 with m6A-modified mRNAs and inhibited YTHDF1-regulated cyclin E2 translation. Moreover, tegaserod reduced the viability of patient-derived AML cells in vitro and prolonged survival in patient-derived xenograft models. Together, our study defines YTHDF1 as an integral regulator of AML progression by regulating the expression of m6A-modified mRNAs, which might serve as a potential therapeutic target for AML.

SIGNIFICANCE

The m6A reader YTHDF1 is required for progression of acute myelogenous leukemia and can be targeted with the FDA-approved drug tegaserod to suppress leukemia growth.

Egr3 as an important regulator of uterine decidualization through targeting Hand2

Early growth response 3 (Egr3) is required for embryogenesis, but little understanding is usable about its function in embryo implantation and decidualization. The present study exhibited an obvious localization of Egr3 in luminal epithelium and subluminal stroma at implantation sites. Administration of estrogen brought about a distinct gather of Egr3 mRNA in uterine luminal and glandular epithelia. Meanwhile, Egr3 was visualized in the decidua where it might facilitate the proliferation of stromal cells via Ccnd3 and accelerate stromal differentiation, testifying the significance of Egr3 in decidualization. In ovariectomized mice uteri or stromal cells, progesterone advanced the expression of Egr3 whose obstruction counteracted the inducement of stromal differentiation by progesterone. Consistently, Egr3 mediated the influence of cAMP and heparin-binding EGF-like growth factor (HB-EGF) on the differentiation program. Additionally, cAMP-protein kinase A (PKA) signaling mediated the adjustment of progesterone on Egr3. Impediment of HB-EGF antagonized the ascendance of Egr3 conferred by cAMP. In stromal cells, Egr3 activated the transcription of Hand2 whose promoter region exhibited the binding enrichment of Egr3. Activation of Hand2 relieved the weakness of stromal differentiation by Egr3 hinderance, whereas knockdown of Hand2 neutralized the guidance of Egr3 overexpression on the differentiation program. Collectively, Egr3 was identified as an important regulator of uterine decidualization through targeting Hand2 in response to progesterone/cAMP/HB-EGF pathway.

Chemotherapy-induced thrombocytopenia: literature review

Chemotherapy-induced thrombocytopenia (CIT) is a common condition that frequently results in reduced chemotherapy dosages, postponed treatment, bleeding, and unfavorable oncological outcomes. At present, there is no clear suggestions for preventing or treating CIT. Thrombopoietin (TPO) replacement therapy has been invented and used to treat CIT to promote the production of megakaryocytes and stimulate the formation of platelets. However, this treatment is limited to the risk of immunogenicity and cancer progression. Therefore, an unmet need exists for exploring alternatives to TPO to address the clinical issue of CIT. Application of appropriate therapeutic drugs may be due to understanding the potential mechanisms of CIT. Studies have shown that chemotherapy significantly affects various cells in bone marrow (BM) microenvironment, reduces their ability to support normal hematopoiesis, and may lead to BM damage, including CIT in cancer patients. This review focuses on the epidemiology and treatment of cancer patients with CIT. We also introduce some recent progress to understand the cellular and molecular mechanisms of chemotherapy inhibiting normal hematopoiesis and causing thrombocytopenia.

Emerging roles of extracellular vesicles in normal and malignant hematopoiesis

Hematopoietic stem cells, regulated by their microenvironment (or “niche”), sustain the production of mature blood and immune cells. Leukemia cells remodel the microenvironment to enhance their survival, which is accompanied by the loss of support for normal hematopoiesis in hematologic malignancies. Extracellular vesicles (EVs) mediate intercellular communication in physiological and pathological conditions, and deciphering their functions in cell-cell interactions in the ecosystem can highlight potential therapeutic targets. In this Review, we illustrate the utility of EVs derived from various cell types, focusing on the biological molecules they contain and the behavioral alterations they can induce in recipient cells. We also discuss the potential for clinical application in hematologic malignancies, including EV-based therapeutic regimens, drug delivery via EVs, and the use of EVs (or their cargoes) as biomarkers.

The immune checkpoint ICOSLG is a relapse-predicting biomarker and therapeutic target in infant t(4;11) acute lymphoblastic leukemia

The most frequent genetic aberration leading to infant ALL (iALL) is the chromosomal translocation t(4;11), generating the fusion oncogenes KMT2A:AFF1 and AFF1:KMT2A, respectively. KMT2A-r iALL displays a dismal prognosis through high relapse rates and relapse-associated mortality. Relapse occurs frequently despite ongoing chemotherapy and without the accumulation of secondary mutations. A rational explanation for the observed chemo-resistance and satisfactory treatment options remain to be elucidated. We found that elevated ICOSLG expression level at diagnosis was associated with inferior event free survival (EFS) in a cohort of 43 patients with t(4;-11) iALL and that a cohort of 18 patients with iALL at relapse displayed strongly increased ICOSLG expression. Furthermore, co-culturing t(4;11) ALL cells (ICOSLG^hi) with primary T-cells resulted in the development of T_regs. This was impaired through treatment with a neutralizing ICOSLG antibody. These findings imply ICOSLG (1) as a relapse-predicting biomarker, and (2) as a therapeutic target involved in a potential immune evasion relapse-mechanism of infant t(4;11) ALL.

•

Early growth response 3 (EGR3) is a direct transactivator of the immune checkpoint gene ICOSLG

•

high ICOSLG expression at diagnosis is predictive for ALL relapse

•

EGR3 and ICOSLG expressions are relapse-associated

•

expression of ICOSLG on t(4;11) ALL cells leads to the rapid expansion of Tregs

Metalloproteinase inhibition reduces AML growth, prevents stem cell loss, and improves chemotherapy effectiveness

Acute myeloid leukemia (AML) is a blood cancer of the myeloid lineage. Its prognosis remains poor, highlighting the need for new therapeutic and precision medicine approaches. AML symptoms often include cytopenias linked to loss of healthy hematopoietic stem and progenitor cells (HSPCs). The mechanisms behind HSPC decline are complex and still poorly understood. Here, intravital microscopy (IVM) of a well-established experimental model of AML allows direct observation of the interactions between healthy and malignant cells in the bone marrow (BM), suggesting that physical dislodgment of healthy cells by AML through damaged vasculature may play an important role. Multiple matrix metalloproteinases (MMPs), known to remodel extracellular matrix, are expressed by AML cells and the BM microenvironment. We reason MMPs could be involved in cell displacement and vascular leakiness; therefore, we evaluate the therapeutic potential of MMP pharmacological inhibition using the broad-spectrum inhibitor prinomastat. IVM analyses of prinomastat-treated mice reveal reduced vascular permeability and healthy cell clusters in circulation and lower AML infiltration, proliferation, and cell migration. Furthermore, treated mice have increased retention of healthy HSPCs in the BM and increased survival following chemotherapy. Analysis of a human AML transcriptomic database reveals widespread MMP deregulation, and human AML cells show susceptibility to MMP inhibition. Overall, our results suggest that MMP inhibition could be a promising complementary therapy to reduce AML growth and limit HSPC loss and BM vascular damage caused by MLL-AF9 and possibly other AML subtypes.

A Murine Model With JAK2V617F Expression in Both Hematopoietic Cells and Vascular Endothelial Cells Recapitulates the Key Features of Human Myeloproliferative Neoplasm

The myeloproliferative neoplasms (MPNs) are characterized by an expansion of the neoplastic hematopoietic stem/progenitor cells (HSPC) and an increased risk of cardiovascular complications. The acquired kinase mutation JAK2V617F is present in hematopoietic cells in a majority of patients with MPNs. Vascular endothelial cells (ECs) carrying the JAK2V617F mutation can also be detected in patients with MPNs. In this study, we show that a murine model with both JAK2V617F-bearing hematopoietic cells and JAK2V617F-bearing vascular ECs recapitulated all the key features of the human MPN disease, which include disease transformation from essential thrombocythemia to myelofibrosis, extramedullary splenic hematopoiesis, and spontaneous cardiovascular complications. We also found that, during aging and MPN disease progression, there was a loss of both HSPC number and HSPC function in the marrow while the neoplastic hematopoiesis was relatively maintained in the spleen, mimicking the advanced phases of human MPN disease. Different vascular niche of the marrow and spleen could contribute to the different JAK2V617F mutant stem cell functions we have observed in this JAK2V617F-positive murine model. These results indicate that the spleen is functionally important for the JAK2V617F mutant neoplastic hematopoiesis during aging and MPN disease progression. Compared to other MPN murine models reported so far, our studies demonstrate that JAK2V617F-bearing vascular ECs play an important role in both the hematologic and cardiovascular abnormalities of MPN.

XIST promotes apoptosis and the inflammatory response in CSE-stimulated cells via the miR-200c-3p/EGR3 axis

Background

Chronic obstructive pulmonary disease (COPD) is a disease that causes obstructed airways and abnormal inflammatory responses in the lungs. Early growth response 3 (EGR3) has been revealed to play a vital role in the regulation of the inflammatory response in certain diseases. We aimed to explore the role of EGR3 and its upstream mechanism in COPD.

Methods and result

In the present study, 16HBE cells were treated with cigarette smoke extract (CSE) to mimic the inflammatory response in vitro. RT-qPCR revealed that the expression of EGR3 was upregulated in lungs from COPD patients. EGR3 expression in 16HBE cells was increased by CSE treatment. Moreover, flow cytometry analysis and western blot analysis showed that EGR3 downregulation inhibited 16HBE cell apoptosis. EGR3 silencing decreased the protein levels of IL-6, TNF-α, IL-1β and COX2 in CSE-stimulated 16HBE cells. In addition, EGR3 was targeted by microRNA-200c-3p (miR-200c-3p) in 16HBE cells. MiR-200c-3p expression was significantly decreased in lung tissues from COPD patients compared to that in healthy controls. Furthermore, miR-200c-3p bound to lncRNA X-inactive specific transcript (XIST) in 16HBE cells. Additionally, XIST expression was elevated in lung tissues from COPD patients. Rescue assays indicated that EGR3 overexpression counteracted the effects of XIST downregulation on apoptosis and inflammation in CSE-stimulated 16HBE cells.

Conclusion

The XIST/miR-200c-3p/EGR3 axis facilitated apoptosis and inflammation in CSE-stimulated 16HBE cells. These findings may provide novel insight for treating COPD by alleviating lung inflammation.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12890-021-01582-8.

DPP4+ exosomes in AML patients' plasma suppress proliferation of hematopoietic progenitor cells

Mechanisms by which acute myeloid leukemia (AML) interferes with normal hematopoiesis are under intense investigation. Emerging evidence suggests that exosomes produced by leukemia blasts suppress hematopoiesis. Exosomes isolated from AML patients' plasma at diagnosis significantly and dose-dependently suppressed colony formation of normal hematopoietic progenitor cells (HPC). Levels of HPC suppression mediated by exosomes of AML patients who achieved complete remission (CR) were significantly decreased compared to those observed at AML diagnosis. Exosomes from plasma of patients who had achieved CR but with incomplete cell count recovery (CRi) after chemotherapy suppressed in vitro colony formation as effectively as did exosomes obtained at AML diagnosis. Dipeptidylpeptidase4 (DPP4/CD26), a serine protease that cleaves select penultimate amino acids of various proteins, has been previously implicated in the regulation of hematopoiesis. DPP4 was carried by exosomes from AML plasma or leukemia cell lines. Leukemia exosomes which suppressed HSC colony formation had markedly higher DPP4 functional activity than that detected in the exosomes of normal donors. Pharmacological inhibition of DPP4 activity in AML exosomes reversed the effects of exosome-mediated myelosuppression. Reversing the negative effects of exosomes on AML hematopoiesis, and thus improving cell count recovery, might emerge as a new therapeutic approach to AML.

Toxocara canis Infection Alters lncRNA and mRNA Expression Profiles of Dog Bone Marrow

Bone marrow is the main hematopoietic organ that produces red blood cells, granulocytes, monocyte/macrophages, megakaryocytes, lymphocytes, and myeloid dendritic cells. Many of these cells play roles in the pathogenesis of Toxocara canis infection, and understanding how infection alters the dynamics of transcription regulation in bone marrow is therefore critical for deciphering the global changes in the dog transcriptional signatures during T. canis infection. In this study, long non-coding RNA (lncRNA) and messenger RNA (mRNA) expression profiles in the bone marrow of Beagle dogs infected with T. canis were determined at 12 h post-infection (hpi), 24 hpi, 96 hpi, and 36 days post-infection (dpi). RNA-sequencing and bioinformatics analysis identified 1,098, 984, 1,120, and 1,305 differentially expressed lncRNAs (DElncRNAs), and 196, 253, 223, and 328 differentially expressed mRNAs (DEmRNAs) at 12 h, 24 h, 96 h, and 36 days after infection, respectively. We also identified 29, 36, 38, and 68 DEmRNAs potentially cis-regulated by 44, 44, 51, and 80 DElncRNAs at 12 hpi, 24 hpi, 96 hpi, and 36 dpi, respectively. To validate the sequencing findings, qRT-PCR was performed on 10 randomly selected transcripts. Many altered genes were involved in the differentiation of bone marrow cells. GO of DElncRNAs and GO and KEGG pathway analyses of DEmRNAs revealed alterations in several signaling pathways, including pathways involved in energy metabolism, amino acid biosynthesis and metabolism, Wnt signaling pathway, Huntington's disease, HIF-1 signaling pathway, cGMP–PKG signaling pathway, dilated cardiomyopathy, and adrenergic signaling in cardiomyocytes. These findings revealed that bone marrow of T. canis-infected dogs exhibits distinct lncRNA and mRNA expression patterns compared to healthy control dogs. Our data provide novel insights into T. canis interaction with the definitive host and shed light on the significance of the non-coding portion of the dog genome in the pathogenesis of toxocariasis.

Identification of a Novel Transcription Factor Prognostic Index for Breast Cancer

Transcription factors (TFs) are the mainstay of cancer and have a widely reported influence on the initiation, progression, invasion, metastasis, and therapy resistance of cancer. However, the prognostic values of TFs in breast cancer (BC) remained unknown. In this study, comprehensive bioinformatics analysis was conducted with data from The Cancer Genome Atlas (TCGA) and Gene Expression Omnibus (GEO) database. We constructed the co-expression network of all TFs and linked it to clinicopathological data. Differentially expressed TFs were obtained from BC RNA-seq data in TCGA database. The prognostic TFs used to construct the risk model for progression free interval (PFI) were identified by Cox regression analyses, and the PFI was analyzed by the Kaplan-Meier method. A receiver operating characteristic (ROC) curve and clinical variables stratification analysis were used to detect the accuracy of the prognostic model. Additionally, we performed functional enrichment analysis by analyzing the differential expressed gene between high-risk and low-risk group. A total of nine co-expression modules were identified. The prognostic index based on 4 TFs (NR3C2, ZNF652, EGR3, and ARNT2) indicated that the PFI was significantly shorter in the high-risk group than their low-risk counterpart (p < 0.001). The ROC curve for PFI exhibited acceptable predictive accuracy, with an area under the curve value of 0.705 and 0.730. In the stratification analyses, the risk score index is an independent prognostic variable for PFI. Functional enrichment analyses showed that high-risk group was positively correlated with mTORC1 signaling pathway. In conclusion, the TF-related signature for PFI constructed in this study can independently predict the prognosis of BC patients and provide a deeper understanding of the potential biological mechanism of TFs in BC.

JAK2V617F mutant endothelial cells promote neoplastic hematopoiesis in a mixed vascular microenvironment

The chronic myeloproliferative neoplasms (MPNs) are clonal stem cell disorders. The hematopoietic stem/progenitor cell (HSPC) compartment in patients with MPNs is heterogeneous with the presence of both wild-type and JAK2V617F mutant cells. Mechanisms responsible for mutant stem cell expansion in MPNs are not fully understood. Vascular endothelial cells (ECs) are an essential component of the hematopoietic microenvironment. ECs carrying the JAK2V617F mutation can be detected in patients with MPNs. Utilizing an ex vivo EC-HSPC co-culture system with mixed wild-type and JAK2V617F mutant ECs, we show that even small numbers of JAK2V617F mutant ECs can promote the expansion of JAK2V617F mutant HSPCs in preference to wild-type HSPCs during irradiation or cytotoxic chemotherapy, the two treatments commonly used in the conditioning regimen for stem cell transplantation, the only curative treatment for patients with MPNs. Mechanistically, we found that both cell-cell interactions and secreted factors are important for JAK2V617F mutant EC-mediated neoplastic hematopoiesis. Further understanding of how the JAK2V617F mutation alters vascular niche function will help identify new strategies to not only control neoplastic cell expansion but also prevent disease relapse in patients with MPNs.

Acute myeloid leukemia-induced functional inhibition of healthy CD34+ hematopoietic stem and progenitor cells

Acute myeloid leukemia (AML) is characterized by an expansion of leukemic cells and a simultaneous reduction of normal hematopoietic precursors in the bone marrow (BM) resulting in hematopoietic insufficiency, but the underlying mechanisms are poorly understood in humans. Assuming that leukemic cells functionally inhibit healthy CD34+ hematopoietic stem and progenitor cells (HSPC) via humoral factors, we exposed healthy BM-derived CD34+ HSPC to cell-free supernatants derived from AML cell lines as well as from 24 newly diagnosed AML patients. Exposure to AML-derived supernatants significantly inhibited proliferation, cell cycling, colony formation, and differentiation of healthy CD34+ HSPC. RNA sequencing of healthy CD34+ HSPC after exposure to leukemic conditions revealed a specific signature of genes related to proliferation, cell-cycle regulation, and differentiation, thereby reflecting their functional inhibition on a molecular level. Experiments with paired patient samples showed that these inhibitory effects are markedly related to the immunomagnetically enriched CD34+ leukemic cell population. Using PCR, ELISA, and RNA sequencing, we detected overexpression of TGFβ1 in leukemic cells on the transcriptional and protein level and, correspondingly, a molecular signature related to TGFβ1 signaling in healthy CD34+ HSPC. This inhibitory effect of TGFβ1 on healthy hematopoiesis was functionally corrobated and could be pharmacologically reverted by SD208, an inhibitor of TGFβ receptor 1 signaling. Overall, these data indicate that leukemic cells induce functional inhibition of healthy CD34+ HSPC, at least in part, through TGFβ1, suggesting that blockage of this pathway may improve hematopoiesis in AML.

Acute Myeloid Leukemia: Is It T Time?

Acute myeloid leukemia (AML) is a heterogeneous disease driven by impaired differentiation of hematopoietic primitive cells toward myeloid lineages (monocytes, granulocytes, red blood cells, platelets), leading to expansion and accumulation of "stem" and/or "progenitor"-like or differentiated leukemic cells in the bone marrow and blood. AML progression alters the bone marrow microenvironment and inhibits hematopoiesis' proper functioning, causing sustained cytopenia and immunodeficiency. This review describes how the AML microenvironment influences lymphoid lineages, particularly T lymphocytes that originate from the thymus and orchestrate adaptive immune response. We focus on the elderly population, which is mainly affected by this pathology. We discuss how a permissive AML microenvironment can alter and even worsen the thymic function, T cells' peripheral homeostasis, phenotype, and functions. Based on the recent findings on the mechanisms supporting that AML induces quantitative and qualitative changes in T cells, we suggest and summarize current immunotherapeutic strategies and challenges to overcome these anomalies to improve the anti-leukemic immune response and the clinical outcome of patients.

MiR-451a enhances the phagocytosis and affects both M1 and M2 polarization in macrophages

Leukemia associated macrophages (LAMs), which are different from tumor-associated macrophages as well as classical M1 and M2 macrophages, are specifically activated by leukemic microenvironment. We have reported the heterogeneity of gene expression profiles in LAMs. However, the expression profiles of microRNA (miRNA) in LAMs and their regulatory mechanisms have not been established. Here, the expression profiles of miRNA in LAMs from bone marrow and spleen of acute myeloid leukemia mice were analyzed. Then, the effects of miR-451a, which was upregulated in LAMs, on macrophages were studied by transfecting miRNA mimic to peritoneal macrophages. The results showed that overexpression of miR-451a altered the morphology, enhanced the phagocytic ability of macrophages, and promotes the expression of differentiation marker CD11b in macrophages. Furthermore, miR-451a increased the proliferation capacity of both M1- and M2-polarized macrophages, but not M0 macrophages. Moreover, miR-451a further enhanced the expression of iNOS upon M1 activation. Therefore, our results reveal the miRNA expression profiles in LAMs, and broaden the knowledge about miRNA regulation in macrophages.

A mitophagy inhibitor targeting p62 attenuates the leukemia-initiation potential of acute myeloid leukemia cells

There has been an increasing focus on the tumorigenic potential of leukemia initiating cells (LICs) in acute myeloid leukemia (AML). Despite the important role of selective autophagy in the life-long maintenance of hematopoietic stem cells (HSCs), cancer progression, and chemoresistance, the relationship between LICs and selective autophagy remains to be fully elucidated. Sequestosome 1 (SQSTM1), also known as p62, is a selective autophagy receptor for the degradation of ubiquitinated substrates, and its loss impairs leukemia progression in AML mouse models. In this study, we evaluated the underlying mechanisms of mitophagy in the survival of LICs with XRK3F2, a p62-ZZ inhibitor. We demonstrated that XRK3F2 selectively impaired LICs but spared normal HSCs in both mouse and patient-derived tumor xenograft (PDX) AML models. Mechanistically, we observed that XRK3F2 blocked mitophagy by inhibiting the binding of p62 with defective mitochondria. Our study not only evaluated the effectiveness and safety of XRK3F2 in LICs, but also demonstrated that mitophagy plays an indispensable role in the survival of LICs during AML development and progression, which can be impaired by blocking p62.

Development of BCR-ABL1 Transgenic Zebrafish Model Reproducing Chronic Myeloid Leukemia (CML) Like-Disease and Providing a New Insight into CML Mechanisms

Zebrafish has proven to be a versatile and reliable experimental in vivo tool to study human hematopoiesis and model hematological malignancies. Transgenic technologies enable the generation of specific leukemia types by the expression of human oncogenes under specific promoters. Using this technology, a variety of myeloid and lymphoid malignancies zebrafish models have been described. Chronic myeloid leukemia (CML) is a clonal myeloproliferative neoplasia characterized by the BCR-ABL1 fusion gene, derived from the t (9;22) translocation causing the Philadelphia Chromosome (Ph). The BCR-ABL1 protein is a constitutively activated tyrosine kinas inducing the leukemogenesis and resulting in an accumulation of immature leukemic cells into bone marrow and peripheral blood. To model Ph+ CML, a transgenic zebrafish line expressing the human BCR-ABL1 was generated by the Gal4/UAS system, and then crossed with the hsp70-Gal4 transgenic line. The new line named (BCR-ABL1pUAS:CFP/hsp70-Gal4), presented altered expression of hematopoietic markers during embryonic development compared to controls and transgenic larvae showed proliferating hematopoietic cells in the caudal hematopoietic tissue (CHT). The present transgenic zebrafish would be a robust CML model and a high-throughput drug screening tool.

Tumor Immune Evasion Induced by Dysregulation of Erythroid Progenitor Cells Development

Cancer cells harness normal cells to facilitate tumor growth and metastasis. Within this complex network of interactions, the establishment and maintenance of immune evasion mechanisms are crucial for cancer progression. The escape from the immune surveillance results from multiple independent mechanisms. Recent studies revealed that besides well-described myeloid-derived suppressor cells (MDSCs), tumor-associated macrophages (TAMs) or regulatory T-cells (Tregs), erythroid progenitor cells (EPCs) play an important role in the regulation of immune response and tumor progression. EPCs are immature erythroid cells that differentiate into oxygen-transporting red blood cells. They expand in the extramedullary sites, including the spleen, as well as infiltrate tumors. EPCs in cancer produce reactive oxygen species (ROS), transforming growth factor β (TGF-β), interleukin-10 (IL-10) and express programmed death-ligand 1 (PD-L1) and potently suppress T-cells. Thus, EPCs regulate antitumor, antiviral, and antimicrobial immunity, leading to immune suppression. Moreover, EPCs promote tumor growth by the secretion of growth factors, including artemin. The expansion of EPCs in cancer is an effect of the dysregulation of erythropoiesis, leading to the differentiation arrest and enrichment of early-stage EPCs. Therefore, anemia treatment, targeting ineffective erythropoiesis, and the promotion of EPC differentiation are promising strategies to reduce cancer-induced immunosuppression and the tumor-promoting effects of EPCs.

HELQ and EGR3 expression correlate with IGHV mutation status and prognosis in chronic lymphocytic leukemia

Background

IGHV mutation status is a crucial prognostic biomarker for CLL. In the present study, we investigated the transcriptomic signatures associating with IGHV mutation status and CLL prognosis.

Methods

The co-expression modules and hub genes correlating with IGHV status, were identified using the GSE28654, by ‘WGCNA’ package and R software (version 4.0.2). The over-representation analysis was performed to reveal enriched cell pathways for genes of correlating modules. Then 9 external cohorts were used to validate the correlation of hub genes expression with IGHV status or clinical features (treatment response, transformation to Richter syndrome, etc.). Moreover, to elucidate the significance of hub genes on disease course and prognosis of CLL patients, the Kaplan–Meier analysis for the OS and TTFT of were performed between subgroups dichotomized by the median expression value of individual hub genes.

Results

2 co-expression modules and 9 hub genes ((FCRL1/FCRL2/HELQ/EGR3LPL/LDOC1/ZNF667/SOWAHC/SEPTIN10) correlating with IGHV status were identified by WGCNA, and validated by external datasets. The modules were found to be enriched in NF-kappaB, HIF-1 and other important pathways, involving cell proliferation and apoptosis. The expression of hub genes was revealed to be significantly different, not only between CLL and normal B cell, but also between various types of lymphoid neoplasms. HELQ expression was found to be related with response of immunochemotherapy treatment significantly (p = 0.0413), while HELQ and ZNF667 were expressed differently between stable CLL and Richter syndrome patients (p < 0.0001 and p = 0.0278, respectively). By survival analysis of subgroups, EGR3 expression was indicated to be significantly associated with TTFT by 2 independent cohorts (GSE39671, p = 0.0311; GSE22762, p = 0.0135). While the expression of HELQ and EGR3 was found to be associated with OS (p = 0.0291 and 0.0114 respectively).The Kras, Hedgehog and IL6-JAK-STAT3 pathways were found to be associating with the expression of hub genes, resulting from GSEA.

Conclusions

The expression of HELQ and EGR3 were correlated with IGHV mutation status in CLL patients. Additionally, the expression of HELQ/EGR3 were prognostic markers for CLL associating with targetable cell signaling pathways.

Understanding of the crosstalk between normal residual hematopoietic stem cells and the leukemic niche in acute myeloid leukemia

Acute myeloid leukemia (AML) is a heterogeneous disease, yet clinically most patients present with pancytopenia resulting from bone marrow failure, predisposing them to life-threatening infections and bleeding. The mechanisms by which AML mediates hematopoietic suppression is not well known. Indeed, much effort has so far been focused on how AML remodels the bone marrow niche to make it a more permissive environment, with less focus on how the remodeled niche affects normal hematopoietic cells. In this perspective, we present evidence of the key role of the bone marrow niche in suppressing hematopoietic stem cells (HSCs) during leukemic progression and provide perspectives on how future research on this topic may be exploited to provide treatments for one of the key complications of AML.

Hematopoietic Stem Cell Niche During Homeostasis, Malignancy, and Bone Marrow Transplantation

Self-renewal and multidirectional differentiation of hematopoietic stem cells (HSCs) are strictly regulated by numerous cellular components and cytokines in the bone marrow (BM) microenvironment. Several cell types that regulate HSC niche have been identified, including both non-hematopoietic cells and HSC-derived cells. Specific changes in the niche composition can result in hematological malignancies. Furthermore, processes such as homing, proliferation, and differentiation of HSCs are strongly controlled by the BM niche and have been reported to be related to the success of hematopoietic stem cell transplantation (HSCT). Single-cell sequencing and in vivo imaging are powerful techniques to study BM microenvironment in hematological malignancies and after HSCT. In this review, we discuss how different components of the BM niche, particularly non-hematopoietic and hematopoietic cells, regulate normal hematopoiesis, and changes in the BM niche in leukemia and after HSCT. We believe that this comprehensive review will provide clues for further research on improving HSCT efficiency and exploring potential therapeutic targets for leukemia.

ANGPTL2-containing small extracellular vesicles from vascular endothelial cells accelerate leukemia progression

Small extracellular vesicles (SEVs) are functional messengers of certain cellular niches that permit noncontact cell communications. Whether niche-specific SEVs fulfill this role in cancer is unclear. Here, we used 7 cell type-specific mouse Cre lines to conditionally knock out Vps33b in Cdh5+ or Tie2+ endothelial cells (ECs), Lepr+ BM perivascular cells, Osx+ osteoprogenitor cells, Pf4+ megakaryocytes, and Tcf21+ spleen stromal cells. We then examined the effects of reduced SEV secretion on progression of MLL-AF9-induced acute myeloid leukemia (AML), as well as normal hematopoiesis. Blocking SEV secretion from ECs, but not perivascular cells, megakaryocytes, or spleen stromal cells, markedly delayed the leukemia progression. Notably, reducing SEV production from ECs had no effect on normal hematopoiesis. Protein analysis showed that EC-derived SEVs contained a high level of ANGPTL2, which accelerated leukemia progression via binding to the LILRB2 receptor. Moreover, ANGPTL2-SEVs released from ECs were governed by VPS33B. Importantly, ANGPTL2-SEVs were also required for primary human AML cell maintenance. These findings demonstrate a role of niche-specific SEVs in cancer development and suggest targeting of ANGPTL2-SEVs from ECs as a potential strategy to interfere with certain types of AML.

Multiple myeloma hinders erythropoiesis and causes anaemia owing to high levels of CCL3 in the bone marrow microenvironment

Anaemia is the most common complication of myeloma and is associated with worse clinical outcomes. Although marrow replacement with myeloma cells is widely considered a mechanistic rationale for anaemia, the exact process has not been fully understood. Our large cohort of 1363 myeloma patients had more than 50% of patients with moderate or severe anaemia at the time of diagnosis. Anaemia positively correlated with myeloma cell infiltration in the bone marrow (BM) and worse patient outcomes. The quantity and erythroid differentiation of HSPCs were affected by myeloma cell infiltration in the BM. The master regulators of erythropoiesis, GATA1 and KLF1, were obviously downregulated in myeloma HSPCs. However, the gene encoding the chemokine CCL3 showed significantly upregulated expression. Elevated CCL3 in the BM plasma of myeloma further inhibited the erythropoiesis of HSPCs via activation of CCL3/CCR1/p38 signalling and suppressed GATA1 expression. Treatment with a CCR1 antagonist effectively recovered GATA1 expression and rescued erythropoiesis in HSPCs. Myeloma cell infiltration causes elevated expression of CCL3 in BM, which suppresses the erythropoiesis of HSPCs and results in anaemia by downregulating the level of GATA1 in HSPCs. Thus, our study indicates that targeting CCL3 would be a potential strategy against anaemia and improve the survival of myeloma patients.

SUV39H1 regulates the progression of MLL-AF9-induced acute myeloid leukemia

Epigenetic regulations play crucial roles in leukemogenesis and leukemia progression. SUV39H1 is the dominant H3K9 methyltransferase in the hematopoietic system, and its expression declines with aging. However, the role of SUV39H1 via its-mediated repressive modification H3K9me3 in leukemogenesis/leukemia progression remains to be explored. We found that SUV39H1 was down-regulated in a variety of leukemias, including MLL-r AML, as compared with normal individuals. Decreased levels of Suv39h1 expression and genomic H3K9me3 occupancy were observed in LSCs from MLL-r-induced AML mouse models in comparison with that of hematopoietic stem/progenitor cells. Suv39h1 overexpression increased leukemia latency and decreased the frequency of LSCs in MLL-r AML mouse models, while Suv39h1 knockdown accelerated disease progression with increased number of LSCs. Increased Suv39h1 expression led to the inactivation of Hoxb13 and Six1, as well as reversion of Hoxa9/Meis1 downstream target genes, which in turn decelerated leukemia progression. Interestingly, Hoxb13 expression is up-regulated in MLL-AF9-induced AML cells, while knockdown of Hoxb13 in MLL-AF9 leukemic cells significantly prolonged the survival of leukemic mice with reduced LSC frequencies. Our data revealed that SUV39H1 functions as a tumor suppressor in MLL-AF9-induced AML progression. These findings provide the direct link of SUV39H1 to AML development and progression.

Differential response to cytotoxic therapy explains treatment dynamics of acute myeloid leukaemia patients: insights from a mathematical modelling approach

Disease response and durability of remission are very heterogeneous in patients with acute myeloid leukaemia (AML). There is increasing evidence that the individual risk of early relapse can be predicted based on the initial treatment response. However, it is unclear how such a correlation is linked to functional aspects of AML progression and treatment. We suggest a mathematical model in which leukaemia-initiating cells and normal/healthy haematopoietic stem and progenitor cells reversibly change between an active state characterized by proliferation and chemosensitivity and a quiescent state, in which the cells do not divide, but are also insensitive to chemotherapy. Applying this model to 275 molecular time courses of nucleophosmin 1-mutated patients, we conclude that the differential chemosensitivity of the leukaemia-initiating cells together with the cells' intrinsic proliferative capacity is sufficient to reproduce both, early relapse as well as long-lasting remission. We can, furthermore, show that the model parameters associated with individual chemosensitivity and proliferative advantage of the leukaemic cells are closely linked to the patients' time to relapse, while a reliable prediction based on early response only is not possible based on the currently available data. Although we demonstrate with our approach, that the complete response data is sufficient to quantify the aggressiveness of the disease, further investigations are necessary to study how an intensive early sampling strategy may prospectively improve risk assessment and help to optimize individual treatments.

Mesenchymal niche remodeling impairs hematopoiesis via stanniocalcin 1 in acute myeloid leukemia

Acute myeloid leukemia (AML) disrupts the generation of normal blood cells, predisposing patients to hemorrhage, anemia, and infections. Differentiation and proliferation of residual normal hematopoietic stem and progenitor cells (HSPCs) are impeded in AML-infiltrated bone marrow (BM). The underlying mechanisms and interactions of residual hematopoietic stem cells (HSCs) within the leukemic niche are poorly understood, especially in the human context. To mimic AML infiltration and dissect the cellular crosstalk in human BM, we established humanized ex vivo and in vivo niche models comprising AML cells, normal HSPCs, and mesenchymal stromal cells (MSCs). Both models replicated the suppression of phenotypically defined HSPC differentiation without affecting their viability. As occurs in AML patients, the majority of HSPCs were quiescent and showed enrichment of functional HSCs. HSPC suppression was largely dependent on secreted factors produced by transcriptionally remodeled MSCs. Secretome analysis and functional validation revealed MSC-derived stanniocalcin 1 (STC1) and its transcriptional regulator HIF-1α as limiting factors for HSPC proliferation. Abrogation of either STC1 or HIF-1α alleviated HSPC suppression by AML. This study provides a humanized model to study the crosstalk among HSPCs, leukemia, and their MSC niche, and a molecular mechanism whereby AML impairs normal hematopoiesis by remodeling the mesenchymal niche.

Detecting qualitative changes in biological systems

Currently, most diseases are diagnosed only after significant disease-associated transformations have taken place. Here, we propose an approach able to identify when systemic qualitative changes in biological systems happen, thus opening the possibility for therapeutic interventions before the occurrence of symptoms. The proposed method exploits knowledge from biological networks and longitudinal data using a system impact analysis. The method is validated on eight biological phenomena, three synthetic datasets and five real datasets, for seven organisms. Most importantly, the method accurately detected the transition from the control stage (benign) to the early stage of hepatocellular carcinoma on an eight-stage disease dataset.

Differentiation of transplanted haematopoietic stem cells tracked by single-cell transcriptomic analysis

How transplanted haematopoietic stem cells (HSCs) behave soon after they reside in a preconditioned host has not been studied due to technical limitations. Here, using single-cell RNA sequencing, we first obtained the transcriptome-based classifications of 28 haematopoietic cell types. We then applied them in conjunction with functional assays to track the dynamic changes of immunophenotypically purified HSCs in irradiated recipients within the first week after transplantation. Based on our transcriptional classifications, most homed HSCs in bone marrow and spleen became multipotent progenitors and, occasionally, some HSCs gave rise to megakaryocytic-erythroid or myeloid precursors. Parallel in vitro and in vivo functional experiments supported the paradigm of robust differentiation without substantial HSC expansion during the first week. Therefore, this study uncovers the previously inaccessible kinetics and fate choices of transplanted HSCs in myeloablated recipients at early stage, with implications for clinical applications of HSCs and other stem cells.

CDK6 Inhibition: A Novel Approach in AML Management

Acute myeloid leukemia (AML) is a complex disease with an aggressive clinical course and high mortality rate. The standard of care for patients has only changed minimally over the past 40 years. However, potentially useful agents have moved from bench to bedside with the potential to revolutionize therapeutic strategies. As such, cell-cycle inhibitors have been discussed as alternative treatment options for AML. In this review, we focus on cyclin-dependent kinase 6 (CDK6) emerging as a key molecule with distinct functions in different subsets of AML. CDK6 exerts its effects in a kinase-dependent and -independent manner which is of clinical significance as current inhibitors only target the enzymatic activity.

The nuclear receptor corepressor NCoR1 regulates hematopoiesis and leukemogenesis in vivo

Enhanced understanding of normal and malignant hematopoiesis pathways should facilitate the development of effective clinical treatment strategies for hematopoietic malignancies. Nuclear receptor corepressor 1 (NCoR1) has been implicated in transcriptional repression and embryonic organ development, but its role in hematopoiesis is yet to be fully elucidated. Here, we showed that hematopoietic-specific loss of NCoR1 leads to expansion of the hematopoietic stem cell (HSC) pool due to aberrant cell cycle entry of long-term HSCs under steady-state conditions. Moreover, NCoR1-deficient HSCs exhibited normal self-renewal capacity but severely impaired lymphoid-differentiation potential in competitive hematopoietic-reconstitution assays. Transcriptome analysis further revealed that several hematopoiesis-associated genes are regulated by NCoR1. In addition, NCoR1 deficiency in hematopoietic cells delayed the course of leukemia and promoted leukemia cell differentiation in an MLL-AF9-induced mouse model. NCoR1 and its partner, histone deacetylase 3, can modulate histone acetylation and gene transcription through binding the promoter regions of myeloid-differentiation genes. Our collective results support the critical involvement of NCoR1 in normal and malignant hematopoiesis in vivo.

Targeting of apoptosis gene loci by reprogramming factors leads to selective eradication of leukemia cells

Applying somatic cell reprogramming strategies in cancer cell biology is a powerful approach to analyze mechanisms of malignancy and develop new therapeutics. Here, we test whether leukemia cells can be reprogrammed in vivo using the canonical reprogramming transcription factors-Oct4, Sox2, Klf4, and c-Myc (termed as OSKM). Unexpectedly, we discover that OSKM can eradicate leukemia cells and dramatically improve survival of leukemia-bearing mice. By contrast, OSKM minimally impact normal hematopoietic cells. Using ATAC-seq, we find OSKM induce chromatin accessibility near genes encoding apoptotic regulators in leukemia cells. Moreover, this selective effect also involves downregulation of H3K9me3 as an early event. Dissection of the functional effects of OSKM shows that Klf4 and Sox2 play dominant roles compared to c-Myc and Oct4 in elimination of leukemia cells. These results reveal an intriguing paradigm by which OSKM-initiated reprogramming induction can be leveraged and diverged to develop novel anti-cancer strategies.

Blocking migration of regulatory T cells to leukemic hematopoietic microenvironment delays disease progression in mouse leukemia model

Blocking the migration of regulatory T cells (Tregs) to the tumor microenvironment is a promising strategy for tumor immunotherapy. Treg accumulation in the leukemic hematopoietic microenvironment (LHME) has adverse impacts on patient outcomes. The mechanism and effective methods of disrupting Treg accumulation in the LHME have not been well established. Here, we studied the distribution and characteristics of Tregs in the LHME, investigated the effects of Treg ablation on leukemia progression, explored the mechanisms leading to Treg accumulation, and studied whether blocking Treg migration to the LHME delayed leukemia progression in MLL-AF9-induced mouse acute myeloid leukemia (AML) models using wildtype (WT) and Foxp3^DTR/GFP mice. Increased accumulation of more activated Tregs was detected in the LHME. Inducible Treg ablation prolonged the survival of AML mice by promoting the antileukemic effects of CD8⁺ T cells. Furthermore, both local expansion and migration accounted for Treg accumulation in the LHME. Moreover, blocking the CCL3-CCR1/CCR5 and CXCL12-CXCR4 axes inhibited Treg accumulation in the LHME and delayed leukemia progression. Our findings provide laboratory evidence for a potential leukemia immunotherapy by blocking the migration of Tregs.

Molecular mechanisms for stemness maintenance of acute myeloid leukemia stem cells

Human acute myeloid leukemia (AML) is a fatal hematologic malignancy characterized with accumulation of myeloid blasts and differentiation arrest. The development of AML is associated with a serial of genetic and epigenetic alterations mainly occurred in hematopoietic stem and progenitor cells (HSPCs), which change HSPC state at the molecular and cellular levels and transform them into leukemia stem cells (LSCs). LSCs play critical roles in leukemia initiation, progression, and relapse, and need to be eradicated to achieve a cure in clinic. Key to successfully targeting LSCs is to fully understand the unique cellular and molecular mechanisms for maintaining their stemness. Here, we discuss LSCs in AML with a focus on identification of unique biological features of these stem cells to decipher the molecular mechanisms of LSC maintenance.

Extracellular vesicles impose quiescence on residual hematopoietic stem cells in the leukemic niche

Progressive remodeling of the bone marrow microenvironment is recognized as an integral aspect of leukemogenesis. Expanding acute myeloid leukemia (AML) clones not only alter stroma composition, but also actively constrain hematopoiesis, representing a significant source of patient morbidity and mortality. Recent studies revealed the surprising resistance of long-term hematopoietic stem cells (LT-HSC) to elimination from the leukemic niche. Here, we examine the fate and function of residual LT-HSC in the BM of murine xenografts with emphasis on the role of AML-derived extracellular vesicles (EV). AML-EV rapidly enter HSC, and their trafficking elicits protein synthesis suppression and LT-HSC quiescence. Mechanistically, AML-EV transfer a panel of miRNA, including miR-1246, that target the mTOR subunit Raptor, causing ribosomal protein S6 hypo-phosphorylation, which in turn impairs protein synthesis in LT-HSC. While HSC functionally recover from quiescence upon transplantation to an AML-naive environment, they maintain relative gains in repopulation capacity. These phenotypic changes are accompanied by DNA double-strand breaks and evidence of a sustained DNA-damage response. In sum, AML-EV contribute to niche-dependent, reversible quiescence and elicit persisting DNA damage in LT-HSC.

Overexpressing miR‑335 inhibits DU145 cell proliferation by targeting early growth response 3 in prostate cancer

MicroRNA-335 (miR-335) was reported to suppress cell proliferation in prostate cancer (PC), a common malignancy in males. The expression of early growth response 3 (EGR3) was determined to be elevated in human PC tissues; however, the possible effects and underlying mechanism of miR-335 on PC remains unknown. In the present study, miR-335 mimics and miR-335 inhibitors were respectively transfected into DU145 cells. Stable silencing of EGR3 was observed in DU145 cells following transfection with small interfering RNA. We also used Cell Counting Kit-8 and in vitro angiogenesis assays to determine the viability and revascularization potential of DU145 cells. The expression levels of EGR and caspase-3 activity were analyzed by immunohistochemistry and immunocytochemistry, respectively. We predicted the target of miR-335 by bioinformatics analysis and a dual-luciferase reporter gene assay. Western blot and quantitative real-time polymerase chain reaction analyses were performed to determine the protein and mRNA expression of molecules. miR-335 expression was downregulated in PC tissues and cell lines. Overexpression of miR-335 significantly reduced the viability and the formation of regenerative tubes of DU145 cells, and inhibited the expression of inflammatory factors. EGR3 was proposed as a possible target of miR-335, and was negatively regulated by miR-335. Silencing EGR3 suppressed the viability and angiogenesis of DU145 cells, and reduced the activity of caspase-3 and inflammatory factor expression. miR-335 inhibition along with EGR3 silencing EGR3 inhibited the cell proliferation. Furthermore, miR-335 inhibited the formation of a PC solid tumor xenograft in vivo. Thus, miR-335 may exert an antitumor effect on DU145 cells by regulating the expression of EGR3. The findings of the present study may provide insight into a novel therapeutic strategy for the treatment of prostatic carcinoma.

Bone marrow endothelial cell-derived interleukin-4 contributes to thrombocytopenia in acute myeloid leukemia

Normal hematopoiesis can be disrupted by the leukemic bone marrow microenvironment, which leads to cytopenia-associated symptoms including anemia, hemorrhage and infection. Thrombocytopenia is a major and sometimes fatal complication in patients with acute leukemia. However, the mechanisms underlying defective thrombopoiesis in leukemia have not been fully elucidated. In the steady state, platelets are continuously produced by megakaryocytes. Using an MLL-AF9-induced acute myeloid leukemia mouse model, we demonstrated a preserved number and proportion of megakaryocyte-primed hematopoietic stem cell subsets, but weakened megakaryocytic differentiation via both canonical and non-canonical routes. This primarily accounted for the dramatic reduction of megakaryocytic progenitors observed in acute myeloid leukemia bone marrow and a severe disruption of the maturation of megakaryocytes. Additionally, we discovered overproduction of interleukin-4 from bone marrow endothelial cells in acute myeloid leukemia and observed inhibitory effects of interleukin-4 throughout the process of megakaryopoiesis in vivo. Furthermore, we observed that inhibition of interleukin-4 in combination with induction chemotherapy not only promoted recovery of platelet counts, but also prolonged the duration of remission in our acute myeloid leukemia mouse model. Our study elucidates a new link between interleukin-4 signaling and defective megakaryopoiesis in acute myeloid leukemia bone marrow, thereby offering a potential therapeutic target in acute myeloid leukemia.