The bone marrow microenvironment – Home of the leukemic blasts

Implication of bone marrow adipose tissue in bone homeostasis during osteoarthritis

OBJECTIVE

To explore the role of bone marrow adipocytes (BMAds) in osteoarthritis (OA).

METHODS

Male and female C57BL/6 mice (n=4/group) underwent meniscectomy (MNX) or SHAM surgery. OA was determined using Osteoarthritis Research Society International (OARSI) score, and the number of perilipin+ adipocytes was quantified. Mesenchymal Stromal Cells (MSCs) from MNX and SHAM mice were differentiated into osteoblasts and adipocytes. Human adipocytes and MSCs (n=8) were enzymatically isolated from epiphyseal and metaphyseal marrow, and from subcutaneous adipose tissue (SCAT) of hip OA patients. Human OA MSCs were differentiated into osteoblasts and adipocytes (OA-Diff-hAdipo). Gene expression patterns of epiphyseal and metaphyseal BMAds, SCAT adipocytes and OA-Diff-hAdipo were evaluated by RNAseq (n=4). The effect conditioned media from OA epiphyseal bone (n=5) on the alkaline phosphatase (ALP) activity and mineralization kinetics was assessed in vitro.

RESULTS

Increase in BMAd density was positively correlated with cartilage degradation in MNX mice. OA modified the differentiation capacity of MSCs, accelerating adipocyte differentiation and failing to produce osteoblasts in both human and mice. Human epiphyseal, metaphyseal and SCAT adipocytes from the same OA patients each displayed a specific transcriptome, suggesting different functions. Enrichment analysis defined metaphyseal OA-BMAds as cells implicated in hematopoietic stem cell differentiation. On the other hand, epiphyseal OA-BMAds were considered as osteogenic cells showing an up-regulation of genes related to bone mineralization and remodeling. Specifically, OA epiphysis-secreted molecules decreased ALP activity and altered in vitro the mineralization process.

CONCLUSION

All these results support the emergence of BMAds as new cell partners in OA, opening new venues for therapeutic approaches.

Development of multivalent CAR T cells as dual immunotherapy and conditioning agents

Hematopoietic stem cell transplantation (HSCT) is the only definitive cure for pediatric acute myeloid leukemia (AML). Despite adjustments in HSCT protocols and improvements in supportive care, 30% of high-risk patients who receive HSCT as part of their therapy still experience disease relapse with high transplant-related mortality. Relapsed AML has a dismal prognosis, and novel therapies are needed. To improve upon the status quo, HSCT would more effectively eliminate relapse-initiating leukemic cells and be delivered with safer, non-genotoxic conditioning. Here, we investigate hematopoietic cytokine receptors (HCRs) and identify that KIT, MPL, and FLT3 are collectively highly expressed in virtually all pediatric AML samples studied. Further, we establish proof-of-concept of a first-in-class chimeric antigen receptor (CAR) T cell that enables simultaneous targeting of KIT, MPL, and FLT3 through a single receptor, which we term the extracellularly linked concatemeric trivalent cytokine (ELECTRIC) CAR. ELECTRIC CARs exhibit potent cytotoxicity against normal and malignant hematopoietic cells in vitro and display anti-HCR activity in a murine xenograft model. We propose that the ELECTRIC system can be the foundation to developing a non-genotoxic, anti-leukemic conditioning regimen to enable safer, more durable efficacy with minimal toxicity.

Paediatric bone marrow mesenchymal stem cells support acute myeloid leukaemia cell survival and enhance chemoresistance via contact-independent mechanism

Children diagnosed with acute myeloid leukaemia (paediatric AML [pAML]) have limited treatment options and relapse rates due to chemoresistance and refractory disease are over 30%. Current treatment is cytotoxic and in itself has long-lasting harsh side effects. New, less toxic treatments are needed. The bone marrow microenvironment provides chemoprotection to leukaemic cells through cell communication and interaction with mesenchymal stem cells (MSCs), but this is not well defined in pAML. Using primary patient material, we identify a cell contact-independent mechanism of MSC-mediated chemoprotection involving extrinsic soluble factors that is abrogated through inhibition of the JAK/STAT and ERK pathways.

Clofarabine-loaded aptamer-conjugated biodegradable nanoparticle successfully targeted CD117 overexpressed HL60 cells and potentially induced apoptosis

Acute Myeloid Leukemia (AML) is a rapidly progressing malignancy characterized by the proliferation of abnormal neutrophils, leading to severe symptoms and complications. Current widely used treatment options include chemotherapy and radiotherapy, which often result in suffering from systemic toxicity and drug resistance. To mitigate systemic toxicity and off-target side effects, a targeted therapeutic strategy is one of the remarkably successful options. For targeting AML cells, we have chosen a single-strand DNA aptamer (Apt), which is specific for the biomarker CD117, overexpressing AML cells. This study introduces explicitly a novel therapeutic approach employing aptamer-conjugated clofarabine-loaded PLGA nanoparticles (Apt-CNP) targeting the CD117 receptor on HL60 leukemia cells. Clofarabine, a potent nucleoside analogue, disrupts DNA synthesis and induces cancer cell death but is limited by its toxicity and resistance. Encapsulation in PLGA nanoparticles enables sustained drug release, maintaining therapeutic concentrations and potentially reducing drug resistance. Our findings demonstrate that Apt-CNP effectively targets HL60 leukemia cells, thereby improving drug delivery and reducing adverse effects on healthy cells. This targeted approach may open a new avenue for more specific drug delivery to mobile and floated blood cells, including AML (HL60 leukemia) cells, and overcome the limitations of traditional AML treatments.

Construction of a stromal-related prognostic model in acute myeloid leukemia by comprehensive bioinformatics analysis

BACKGROUND

Stromal cells play a pivotal role in the tumor microenvironment (TME), significantly impacting the progression of acute myeloid leukemia (AML). This study sought to develop a stromal-related prognostic model for AML, aiming to uncover novel prognostic markers and therapeutic targets.

METHODS

RNA expression data and clinical profiles of AML patients were retrieved from the Cancer Genome Atlas (TCGA). The extent of stromal cell infiltration within the TME was quantified using the ESTIMATE algorithm. Associations between stromal scores and the French-American-British (FAB) classification, overall survival (OS), and the Cancer and Leukemia Group B (CALGB) cytogenetic risk categories were analyzed. Differentially expressed genes (DEGs) were identified, and gene ontology (GO) and protein-protein interaction (PPI) networks were constructed. Prognostic DEGs were selected through LASSO-cox regression analysis. A risk score model was then developed based on these DEGs. A stromal-related prognostic model (SPM) was constructed from the patients' risk scores (RS), and its efficacy was evaluated using Receiver Operating Characteristic (ROC) curves and a nomogram. The association between FAB, CALGB, age, and common mutations and SPM was also assessed. Ultimately, the SPM was validated using an external dataset from 246 patients in the TARGET-AML study.

RESULTS

Kaplan-Meier analysis revealed a significant association between stromal scores and patient survival (p = 0.04). LASSOCox regression identified four genes (MAP7D2, CDRT1, HOXB9, and IRX5) as highly predictive of survival. The prognostic model showed a strong correlation with overall survival, with higher scores indicating poorer outcomes (p = 1.48e-07). Older patients (over 60 years) faced significantly worse prognoses (p = 0.0055). Although no significant association was found between the SPM and the FAB classification (p = 0.063), both poor and intermediate/normal cytogenetic groups had significantly higher SPM risk scores than the favorable group (p = 0.0057 and 0.0026). External validation of the SPM in the TARGET-AML dataset confirmed a significant association with survival (p = 0.00035), with the area under the curve (AUC) for 10-year survival at 75.81 %.

CONCLUSION

Our research successfully established a stromal-related prognostic model in AML, offering new perspectives for prognostic evaluation and identifying potential targets for therapeutic intervention.

In Vitro 3D Models of Haematological Malignancies: Current Trends and the Road Ahead?

Haematological malignancies comprise a diverse group of life-threatening systemic diseases, including leukaemia, lymphoma, and multiple myeloma. Currently available therapies, including chemotherapy, immunotherapy, and CAR-T cells, are often associated with important side effects and with the development of drug resistance and, consequently, disease relapse. In the last decades, it was largely demonstrated that the tumor microenvironment significantly affects cancer cell proliferation and tumor response to treatment. The development of biomimetic, in vitro models may promote the investigation of the interactions between cancer cells and the tumor microenvironment and may help to better understand the mechanisms leading to drug resistance. Although advanced in vitro models have been largely explored in the field of solid tumors, due to the complex nature of the blood cancer tumor microenvironment, the mimicking of haematological malignancies mostly relies on simpler systems, often limited to two-dimensional cell culture, which intrinsically excludes the microenvironmental niche, or to ethically debated animal models. This review aims at reporting an updated overview of state-of-the-art hematological malignancies 3D in vitro models, emphasizing the key features and limitations of existing systems to inspire further research in this underexplored field.

Microenvironment matters: In vitro 3D bone marrow niches differentially modulate survival, phenotype and drug responses of acute myeloid leukemia (AML) cells

Acute myeloid leukemia (AML) is a deadly form of leukemia with ineffective traditional treatment and frequent chemoresistance-associated relapse. Personalized drug screening holds promise in identifying optimal regimen, nevertheless, primary AML cells undergo spontaneous apoptosis during cultures, invalidating the drug screening results. Here, we reconstitute a 3D osteogenic niche (3DON) mimicking that in bone marrow to support primary AML cell survival and phenotype maintenance in cultures. Specifically, 3DON derived from osteogenically differentiated mesenchymal stem cells (MSC) from healthy and AML donors are co-cultured with primary AML cells. The AML cells under the AML_3DON niche showed enhanced viability, reduced apoptosis and maintained CD33+ CD34-phenotype, associating with elevated secretion of anti-apoptotic cytokines in the AML_3DON niche. Moreover, AML cells under the AML_3DON niche exhibited low sensitivity to two FDA-approved chemotherapeutic drugs, further suggesting the physiological resemblance of the AML_3DON niche. Most interestingly, AML cells co-cultured with the healthy_3DON niche are highly sensitive to the same sample drugs. This study demonstrates the differential responses of AML cells towards leukemic and healthy bone marrow niches, suggesting the impact of native cancer cell niche in drug screening, and the potential of re-engineering healthy bone marrow niche in AML patients as chemotherapeutic adjuvants overcoming chemoresistance, respectively.

Impact of bone marrow fibrosis on outcomes of allogeneic hematopoietic stem cell transplantation in acute myeloid leukemia

Bone marrow fibrosis (BMF) of unknown etiology was common in hematological malignancies, but its prognostic value for acute myeloid leukemia (AML) is unclear. We interrogated data from 532 newly diagnosed subjects with AML receiving allogeneic hematological stem cell transplantation to evaluate the prognostic impact of BMF on transplant outcomes. Using the European consensus on the grading of BMF at diagnosis, 255 (48%) subjects were BMF-0, 209 (39%), BMF-1 and 68 (13%), BMF-2-3. Subjects with BMF-2-3 had poor overall survival (P < 0.001), disease-free survival (P < 0.001) and a higher incidence of relapse (CIR, P < 0.001). Multi-variable analyses in subjects achieving pre-transplant complete remission showed BMF-2-3 was an independent risk factor for CIR (Hazard Ratio [HR] = 2.17, (95% CI, 1.11, 4,24); P = 0.02). Furthermore, BMF-2-3 group showed delayed neutrophil and platelet engraftment and delayed B cell recovery post-transplantation. These findings demonstrate the significance of BMF in transplant outcomes and attract more attention to AML with BMF.

High Mobility Group Box 1 (HMGB1): Molecular Signaling and Potential Therapeutic Strategies

High Mobility Group Box 1 (HMGB1) is a highly conserved non-histone chromatin-associated protein across species, primarily recognized for its regulatory impact on vital cellular processes, like autophagy, cell survival, and apoptosis. HMGB1 exhibits dual functionality based on its localization: both as a non-histone protein in the nucleus and as an inducer of inflammatory cytokines upon extracellular release. Pathophysiological insights reveal that HMGB1 plays a significant role in the onset and progression of a vast array of diseases, viz., atherosclerosis, kidney damage, cancer, and neurodegeneration. However, a clear mechanistic understanding of HMGB1 release, translocation, and associated signaling cascades in mediating such physiological dysfunctions remains obscure. This review presents a detailed outline of HMGB1 structure-function relationship and its regulatory role in disease onset and progression from a signaling perspective. This review also presents an insight into the status of HMGB1 druggability, potential limitations in understanding HMGB1 pathophysiology, and future perspective of studies that can be undertaken to address the existing scientific gap. Based on existing paradigm of various studies, HMGB1 is a critical regulator of inflammatory cascades and drives the onset and progression of a broad spectrum of dysfunctions. Studies focusing on HMGB1 druggability have enabled the development of biologics with potential clinical benefits. However, deeper understanding of post-translational modifications, redox states, translocation mechanisms, and mitochondrial interactions can potentially enable the development of better courses of therapy against HMGB1-mediated physiological dysfunctions.

Rationally designed BCR-ABL kinase inhibitors for improved leukemia treatment via covalent and pro-/dual-drug targeting strategies

BACKGROUND

Chronic Myeloid Leukemia (CML) is a blood cancer that remains challenging to cure due to drug resistance and side effects from current BCR-ABL inhibitors. There is an urgent need for novel and more effective BCR-ABL targeting inhibitors and therapeutic strategies to combat this deadly disease.

METHOD

We disclose an "OH-implant" strategy to improve a noncovalent BCR-ABL inhibitor, PPY-A, by adding a hydroxyl group to its scaffold. By taking advantage of this OH "hot spot", we designed a panel of irreversible covalent kinase inhibitors and hypoxia-responsive pro-/dual-drugs, and their biological activities were studied in vitro, in cellulo and in vivo.

RESULT

The resulting compound B1 showed enhanced solubility and biological activity. B4 achieved sustained BCR-ABL inhibition by forming a stable covalent bond with ABL kinase. Hypoxia-responsive prodrug P1 and dual-drugs D1/D2/D3 demonstrated significant anti-tumor effects under hypoxic conditions. The in vivo studies using K562-xenografted mice showed that B1 displayed superior antitumor activity than PPY-A, while P1 and D3 offered better safety profiles alongside significant tumor control.

CONCLUSION

We have successfully developed a chemical biology approach to convert a known noncovalent BCR-ABL inhibitor into more potent and safer inhibitors through covalent and pro-/dual-drug targeting strategies. Our "OH-implant" approach and the resulting drug design strategies have general applicability and hold promise for improvement the performance of various other reported drugs/drug candidates, thereby providing advanced medicines for disease treatment.

BRD4 degraders may effectively counteract therapeutic resistance of leukemic stem cells in AML and ALL

Acute myeloid leukemia (AML) and acute lymphoblastic leukemia (ALL) are life-threatening hematopoietic malignancies characterized by clonal expansion of leukemic blasts in the bone marrow and peripheral blood. The epigenetic reader BRD4 and its downstream effector MYC have recently been identified as potential drug targets in human AML and ALL. We compared anti-leukemic efficacies of the small-molecule BET inhibitor JQ1 and the recently developed BRD4 degraders dBET1 and dBET6 in AML and ALL cells. JQ1, dBET1, and dBET6 were found to suppress growth and viability in all AML and ALL cell lines examined as well as in primary patient-derived AML and ALL cells, including CD34+/CD38- and CD34+/CD38+ leukemic stem and progenitor cells, independent of the type (variant) of leukemia or molecular driver expressed in leukemic cells. Moreover, we found that dBET6 overcomes osteoblast-induced drug resistance in AML and ALL cells, regardless of the type of leukemia or the drug applied. Most promising cooperative or even synergistic drug combination effects were seen with dBET6 and the FLT3 ITD blocker gilteritinib in FLT3 ITD-mutated AML cells, and with dBET6 and the multi-kinase blocker ponatinib in BCR::ABL1+ ALL cells. Finally, all BRD4-targeting drugs suppressed interferon-gamma- and tumor necrosis factor-alpha-induced expression of the resistance-related checkpoint antigen PD-L1 in AML and ALL cells, including LSC. In all assays examined, the BRD4 degrader dBET6 was a superior anti-leukemic drug compared with dBET1 and JQ1. Together, BRD4 degraders may provide enhanced inhibition of multiple mechanisms of therapy resistance in AML and ALL.

Hematopoietic and leukemic stem cells homeostasis: the role of bone marrow niche

The bone marrow microenvironment (BMM) has highly specialized anatomical characteristics that provide a sanctuary place for hematopoietic stem cells (HSCs) that allow appropriate proliferation, maintenance, and self-renewal capacity. Several cell types contribute to the constitution and function of the bone marrow niche. Interestingly, uncovering the secrets of BMM and its interaction with HSCs in health paved the road for research aiming at better understanding the concept of leukemic stem cells (LSCs) and their altered niche. In fact, they share many signals that are responsible for interactions between LSCs and the bone marrow niche, due to several biological similarities between LSCs and HSCs. On the other hand, LSCs differ from HSCs in their abnormal activation of important signaling pathways that regulate survival, proliferation, drug resistance, invasion, and spread. Targeting these altered niches can help in better treatment choices for hematological malignancies and bone marrow disorders in general and acute myeloid leukemia (AML) in particular. Moreover, targeting those niches may help in decreasing the emergence of drug resistance and lower the relapse rate. In this article, the authors reviewed the most recent literature on bone marrow niches and their relations with either normal HSCs and AML cells/LSC, by focusing on pathogenetic and therapeutic implications.

Immune infiltration-related genes regulate the progression of AML by invading the bone marrow microenvironment

In this study, we try to find the pathogenic role of immune-related genes in the bone marrow microenvironment of AML. Through WGCNA, seven modules were obtained, among which the turquoise module containing 1793 genes was highly correlated with the immune infiltration score. By unsupervised clustering, the turquoise module was divided into two clusters: the intersection of clinically significant genes in the TCGA and DEGs to obtain 178 genes for mutation analysis, followed by obtaining 17 genes with high mutation frequency. Subsequently, these 17 genes were subjected to LASSO regression analysis to construct a riskscore model of 8 hub genes. The TIMER database, ImmuCellAI portal website, and ssGSEA elucidate that the hub genes and risk scores are closely related to immune cell infiltration into the bone marrow microenvironment. In addition, we also validated the relative expression levels of hub genes using the TCGA database and GSE114868, and additional expression levels of hub genes in AML cell lines in vitro. Therefore, we constructed an immune infiltration-related gene model that identify 8 hub genes with good risk stratification and predictive prognosis for AML.

Application of omics in the diagnosis, prognosis, and treatment of acute myeloid leukemia

Acute myeloid leukemia (AML) is the most frequent leukemia in adults with a high mortality rate. Current diagnostic criteria and selections of therapeutic strategies are generally based on gene mutations and cytogenetic abnormalities. Chemotherapy, targeted therapies, and hematopoietic stem cell transplantation (HSCT) are the major therapeutic strategies for AML. Two dilemmas in the clinical management of AML are related to its poor prognosis. One is the inaccurate risk stratification at diagnosis, leading to incorrect treatment selections. The other is the frequent resistance to chemotherapy and/or targeted therapies. Genomic features have been the focus of AML studies. However, the DNA-level aberrations do not always predict the expression levels of genes and proteins and the latter is more closely linked to disease phenotypes. With the development of high-throughput sequencing and mass spectrometry technologies, studying downstream effectors including RNA, proteins, and metabolites becomes possible. Transcriptomics can reveal gene expression and regulatory networks, proteomics can discover protein expression and signaling pathways intimately associated with the disease, and metabolomics can reflect precise changes in metabolites during disease progression. Moreover, omics profiling at the single-cell level enables studying cellular components and hierarchies of the AML microenvironment. The abundance of data from different omics layers enables the better risk stratification of AML by identifying prognosis-related biomarkers, and has the prospective application in identifying drug targets, therefore potentially discovering solutions to the two dilemmas. In this review, we summarize the existing AML studies using omics methods, both separately and combined, covering research fields of disease diagnosis, risk stratification, prognosis prediction, chemotherapy, as well as targeted therapy. Finally, we discuss the directions and challenges in the application of multi-omics in precision medicine of AML. Our review may inspire both omics researchers and clinical physicians to study AML from a different angle.

Unveiling novel insights in acute myeloid leukemia through single-cell RNA sequencing

Acute myeloid leukemia (AML) is a complex and heterogeneous group of aggressive hematopoietic stem cell disease. The presence of diverse and functionally distinct populations of leukemia cells within the same patient's bone marrow or blood poses a significant challenge in diagnosing and treating AML. A substantial proportion of AML patients demonstrate resistance to induction chemotherapy and a grim prognosis upon relapse. The rapid advance in next generation sequencing technologies, such as single-cell RNA-sequencing (scRNA-seq), has revolutionized our understanding of AML pathogenesis by enabling high-resolution interrogation of the cellular heterogeneity in the AML ecosystem, and their transcriptional signatures at a single-cell level. New studies have successfully characterized the inextricably intertwined interactions among AML cells, immune cells and bone marrow microenvironment and their contributions to the AML development, therapeutic resistance and relapse. These findings have deepened and broadened our understanding the complexity and heterogeneity of AML, which are difficult to detect with bulk RNA-seq. This review encapsulates the burgeoning body of knowledge generated through scRNA-seq, providing the novel insights and discoveries it has unveiled in AML biology. Furthermore, we discuss the potential implications of scRNA-seq in therapeutic opportunities, focusing on immunotherapy. Finally, we highlight the current limitations and future direction of scRNA-seq in the field.

Immunotherapies of acute myeloid leukemia: Rationale, clinical evidence and perspective

Acute myeloid leukemia (AML) is a prevalent hematological malignancy that exhibits a wide array of molecular abnormalities. Although traditional treatment modalities such as chemotherapy and allogeneic stem cell transplantation (HSCT) have become standard therapeutic approaches, a considerable number of patients continue to face relapse and encounter a bleak prognosis. The emergence of immune escape, immunosuppression, minimal residual disease (MRD), and other contributing factors collectively contribute to this challenge. Recent research has increasingly highlighted the notable distinctions between AML tumor microenvironments and those of healthy individuals. In order to investigate the potential therapeutic mechanisms, this study examines the intricate transformations occurring between leukemic cells and their surrounding cells within the tumor microenvironment (TME) of AML. This review classifies immunotherapies into four distinct categories: cancer vaccines, immune checkpoint inhibitors (ICIs), antibody-based immunotherapies, and adoptive T-cell therapies. The results of numerous clinical trials strongly indicate that the identification of optimal combinations of novel agents, either in conjunction with each other or with chemotherapy, represents a crucial advancement in this field. In this review, we aim to explore the current and emerging immunotherapeutic methodologies applicable to AML patients, identify promising targets, and emphasize the crucial requirement to augment patient outcomes. The application of these strategies presents substantial therapeutic prospects within the realm of precision medicine for AML, encompassing the potential to ameliorate patient outcomes.

Targeting nucleolin improves sensitivity to chemotherapy in acute lymphoblastic leukemia

PURPOSE

Most patients with acute lymphoblastic leukemia (ALL) are treated with chemotherapy as primary care. Although the treatment response is usually positive, resistance and relapse often occur via unknown mechanisms. The purpose of this study was to identify factors associated with chemotherapy resistance in ALL. Here, we present clinical and experimental evidence that overexpression of nucleolin (NCL), a multifunctional nucleolar protein, is linked to drug resistance in ALL.

METHODS

NCL mRNA and protein levels were compared between cell lines and patient samples using qRT-PCR and immunoblotting. NCL mRNA levels were compared between patients of different disease stages from our clinic patients' specimens and publicly available ALL patient datasets. Cells and patient-derived xenograft mouse experiments were performed to assess the effect of NCL inhibition on ALL chemotherapy effectiveness.

RESULTS

Analysis of patient specimens, and publicly available RNA-sequencing datasets revealed a strong correlation between the abundance of NCL and disease relapse or poor survival in B-ALL. Altering NCL expression results in changes in drug sensitivity in ALL cell lines. High levels of NCL upregulated components of the ATP-binding cassette transporters via activation of the ERK pathway, resulting in a decrease in drug accumulation inside the cells. Targeting NCL with AS1411, an NCL-binding oligonucleotide aptamer, significantly increased the sensitivity of ALL cell lines and cells/patient-derived ALL xenograft mice to chemotherapeutic drugs and prolonged mouse survival.

CONCLUSION

Our results highlight NCL as a prognostic marker in B-ALL and a potential therapeutic target to combat chemotherapy resistance in ALL.

Good Cop, Bad Cop: Profiling the Immune Landscape in Multiple Myeloma

Multiple myeloma (MM) is a dyscrasia of plasma cells (PCs) characterized by abnormal immunoglobulin (Ig) production. The disease remains incurable due to a multitude of mutations and structural abnormalities in MM cells, coupled with a favorable microenvironment and immune suppression that eventually contribute to the development of drug resistance. The bone marrow microenvironment (BMME) is composed of a cellular component comprising stromal cells, endothelial cells, osteoclasts, osteoblasts, and immune cells, and a non-cellular component made of the extracellular matrix (ECM) and the liquid milieu, which contains cytokines, growth factors, and chemokines. The bone marrow stromal cells (BMSCs) are involved in the adhesion of MM cells, promote the growth, proliferation, invasion, and drug resistance of MM cells, and are also crucial in angiogenesis and the formation of lytic bone lesions. Classical immunophenotyping in combination with advanced immune profiling using single-cell sequencing technologies has enabled immune cell-specific gene expression analysis in MM to further elucidate the roles of specific immune cell fractions from peripheral blood and bone marrow (BM) in myelomagenesis and progression, immune evasion and exhaustion mechanisms, and development of drug resistance and relapse. The review describes the role of BMME components in MM development and ongoing clinical trials using immunotherapeutic approaches.

Fabrication of a three-dimensional bone marrow niche-like acute myeloid Leukemia disease model by an automated and controlled process using a robotic multicellular bioprinting system

BACKGROUND

Acute myeloid leukemia (AML) is a hematological malignancy that remains a therapeutic challenge due to the high incidence of disease relapse. To better understand resistance mechanisms and identify novel therapies, robust preclinical models mimicking the bone marrow (BM) microenvironment are needed. This study aimed to achieve an automated fabrication process of a three-dimensional (3D) AML disease model that recapitulates the 3D spatial structure of the BM microenvironment and applies to drug screening and investigational studies.

METHODS

To build this model, we investigated a unique class of tetramer peptides with an innate ability to self-assemble into stable hydrogel. An automated robotic bioprinting process was established to fabricate a 3D BM (niche-like) multicellular AML disease model comprised of leukemia cells and the BM's stromal and endothelial cellular fractions. In addition, monoculture and dual-culture models were also fabricated. Leukemia cell compatibility, functionalities (in vitro and in vivo), and drug assessment studies using our model were performed. In addition, RNAseq and gene expression analysis using TaqMan arrays were also performed on 3D cultured stromal cells and primary leukemia cells.

RESULTS

The selected peptide hydrogel formed a highly porous network of nanofibers with mechanical properties similar to the BM extracellular matrix. The robotic bioprinter and the novel quadruple coaxial nozzle enabled the automated fabrication of a 3D BM niche-like AML disease model with controlled deposition of multiple cell types into the model. This model supported the viability and growth of primary leukemic, endothelial, and stromal cells and recapitulated cell-cell and cell-ECM interactions. In addition, AML cells in our model possessed quiescent characteristics with improved chemoresistance attributes, resembling more the native conditions as indicated by our in vivo results. Moreover, the whole transcriptome data demonstrated the effect of 3D culture on enhancing BM niche cell characteristics. We identified molecular pathways upregulated in AML cells in our 3D model that might contribute to AML drug resistance and disease relapse.

CONCLUSIONS

Our results demonstrate the importance of developing 3D biomimicry models that closely recapitulate the in vivo conditions to gain deeper insights into drug resistance mechanisms and novel therapy development. These models can also improve personalized medicine by testing patient-specific treatments.

Role of IL8 in myeloid malignancies

Aberrant overexpression of Interleukin-8 (IL8) has been reported in Myelodysplastic Syndromes (MDS), Acute Myeloid Leukemia (AML), Myeloproliferative Neoplasms (MPNs) and other myeloid malignancies. IL8 (CXCL8) is a CXC chemokine that is secreted by aberrant hematopoietic stem and progenitors as well as other cells in the tumor microenvironment. IL8 can bind to CXCR1/CXCR2 receptors and activate oncogenic signaling pathways, and also increase the recruitment of myeloid derived suppressor cells to the tumor microenvironment. IL8/CXCR1/2 overexpression has been associated with poorer prognosis in MDS and AML and increased bone marrow fibrosis in Myelofibrosis. Preclinical studies have demonstrated benefit of inhibiting the IL8/CXCR1/2 pathways via restricting the growth of leukemic stem cells as well as normalizing the immunosuppressive microenvironment in tumors. Targeting the IL8-CXCR1/2 pathway is a potential therapeutic strategy in myeloid neoplasms and is being evaluated with small molecule inhibitors as well as monoclonal antibodies in ongoing clinical trials. We review the role of IL8 signaling pathway in myeloid cancers and discuss future directions on therapeutic targeting of IL8 in these diseases.

The Small-Molecule E26-Transformation-Specific Inhibitor TK216 Attenuates the Oncogenic Properties of Pediatric Leukemia

The E26-transformation-specific (ETS) transcription factors regulate multiple aspects of the normal hematopoietic system. There is an increasing body of evidence suggesting aberrant ETS activity and its contribution to leukemia initiation and progression. In this study, we evaluated the small-molecule ETS inhibitor TK216 and demonstrated its anti-tumor activity in pediatric leukemia. We found TK216 induced growth inhibition, cell cycle arrest and apoptosis and inhibited the migratory capability of leukemic cells, without significantly inhibiting the cell viability of normal blood mononuclear cells. Priming the leukemic cells with 5-Azacitidine enhanced the cytotoxic effects of TK216 on pediatric leukemia cells. Importantly, we found purine-rich box1 (PU.1) to be a potential target of TK216 in myeloid and B-lymphoid leukemic cells. In addition, TK216 sharply decreased Mcl-1 protein levels in a dose-dependent manner. Consistent with this, TK216 also potentiated the cytotoxic effects of Bcl-2 inhibition in venetoclax-resistant cells. The sustained survival benefit provided to leukemic cells in the presence of bone-marrow-derived conditioned media is also found to be modulated by TK216. Taken together, our data indicates that TK216 could be a promising targeted therapeutic agent for the treatment of acute myeloid and B-lymphoid leukemia.

TRAIL promotes the polarization of human macrophages toward a proinflammatory M1 phenotype and is associated with increased survival in cancer patients with high tumor macrophage content

Background

TNF-related apoptosis-inducing ligand (TRAIL) is a member of the TNF superfamily that can either induce cell death or activate survival pathways after binding to death receptors (DRs) DR4 or DR5. TRAIL is investigated as a therapeutic agent in clinical trials due to its selective toxicity to transformed cells. Macrophages can be polarized into pro-inflammatory/tumor-fighting M1 macrophages or anti-inflammatory/tumor-supportive M2 macrophages and an imbalance between M1 and M2 macrophages can promote diseases. Therefore, identifying modulators that regulate macrophage polarization is important to design effective macrophage-targeted immunotherapies. The impact of TRAIL on macrophage polarization is not known.

Methods

Primary human monocyte-derived macrophages were pre-treated with either TRAIL or with DR4 or DR5-specific ligands and then polarized into M1, M2a, or M2c phenotypes in vitro. The expression of M1 and M2 markers in macrophage subtypes was analyzed by RNA sequencing, qPCR, ELISA, and flow cytometry. Furthermore, the cytotoxicity of the macrophages against U937 AML tumor targets was assessed by flow cytometry. TCGA datasets were also analyzed to correlate TRAIL with M1/M2 markers, and the overall survival of cancer patients.

Results

TRAIL increased the expression of M1 markers at both mRNA and protein levels while decreasing the expression of M2 markers at the mRNA level in human macrophages. TRAIL also shifted M2 macrophages towards an M1 phenotype. Our data showed that both DR4 and DR5 death receptors play a role in macrophage polarization. Furthermore, TRAIL enhanced the cytotoxicity of macrophages against the AML cancer cells in vitro. Finally, TRAIL expression was positively correlated with increased expression of M1 markers in the tumors from ovarian and sarcoma cancer patients and longer overall survival in cases with high, but not low, tumor macrophage content.

Conclusions

TRAIL promotes the polarization of human macrophages toward a proinflammatory M1 phenotype via both DR4 and DR5. Our study defines TRAIL as a new regulator of macrophage polarization and suggests that targeting DRs can enhance the anti-tumorigenic response of macrophages in the tumor microenvironment by increasing M1 polarization.

The role of bone marrow microenvironment (BMM) cells in acute myeloid leukemia (AML) progression: immune checkpoints, metabolic checkpoints, and signaling pathways

Acute myeloid leukemia (AML) comprises a multifarious and heterogeneous array of illnesses characterized by the anomalous proliferation of myeloid cells in the bone marrow microenvironment (BMM). The BMM plays a pivotal role in promoting AML progression, angiogenesis, and metastasis. The immune checkpoints (ICs) and metabolic processes are the key players in this process. In this review, we delineate the metabolic and immune checkpoint characteristics of the AML BMM, with a focus on the roles of BMM cells e.g. tumor-associated macrophages, natural killer cells, dendritic cells, metabolic profiles and related signaling pathways. We also discuss the signaling pathways stimulated in AML cells by BMM factors that lead to AML progression. We then delve into the roles of immune checkpoints in AML angiogenesis, metastasis, and cell proliferation, including co-stimulatory and inhibitory ICs. Lastly, we discuss the potential therapeutic approaches and future directions for AML treatment, emphasizing the potential of targeting metabolic and immune checkpoints in AML BMM as prognostic and therapeutic targets. In conclusion, the modulation of these processes through the use of directed drugs opens up new promising avenues in combating AML. Thereby, a comprehensive elucidation of the significance of these AML BMM cells' metabolic and immune checkpoints and signaling pathways on leukemic cells can be undertaken in the future investigations. Additionally, these checkpoints and cells should be considered plausible multi-targeted therapies for AML in combination with other conventional treatments in AML. Video Abstract.

Plant-derived extracts and metabolic modulation in leukemia: a promising approach to overcome treatment resistance

Leukemic cells acquire complex and often multifactorial mechanisms of resistance to treatment, including various metabolic alterations. Although the use of metabolic modulators has been proposed for several decades, their use in clinical practice has not been established. Natural products, the so-called botanical drugs, are capable of regulating tumor metabolism, particularly in hematopoietic tumors, which could partly explain the biological activity attributed to them for a long time. This review addresses the most recent findings relating to metabolic reprogramming-Mainly in the glycolytic pathway and mitochondrial activity-Of leukemic cells and its role in the generation of resistance to conventional treatments, the modulation of the tumor microenvironment, and the evasion of immune response. In turn, it describes how the modulation of metabolism by plant-derived extracts can counteract resistance to chemotherapy in this tumor model and contribute to the activation of the antitumor immune system.

Engineering tandem CD33xCD146 CAR CIK (cytokine-induced killer) cells to target the acute myeloid leukemia niche

In acute myeloid leukemia (AML), malignant stem cells hijack the normal bone marrow niche where they are largely protected from the current therapeutic approaches. Thus, eradicating these progenitors is the ultimate challenge in the treatment of this disease. Specifically, the development of chimeric antigen receptors (CARs) against distinct mesenchymal stromal cell subpopulations involved in the maintenance of leukemic stem cells within the malignant bone marrow microenvironment could represent a new strategy to improve CAR T-cell therapy efficacy, which is still unsuccessful in AML. As a proof of concept, we generated a novel prototype of Tandem CAR, with one specificity directed against the leukemic cell marker CD33 and the other against the mesenchymal stromal cell marker CD146, demonstrating its capability of simultaneously targeting two different cell types in a 2D co-culture system. Interestingly, we could also observe an in vitro inhibition of CAR T cell functionality mediated by stromal cells, particularly in later effector functions, such as reduction of interferon-gamma and interleukin-2 release and impaired proliferation of the CAR⁺ effector Cytokine-Induced Killer (CIK) cells. Taken together, these data demonstrate the feasibility of a dual targeting model against two molecules, which are expressed on two different target cells, but also highlight the immunomodulatory effect on CAR CIK cells exerted by stromal cells, confirming that the niche could be an obstacle to the efficacy of CAR T cells. This aspect should be considered in the development of novel CAR T cell approaches directed against the AML bone marrow niche.

An Updated Overview of the Role of CYP450 during Xenobiotic Metabolization in Regulating the Acute Myeloid Leukemia Microenvironment

Oxidative stress is associated with several acute and chronic disorders, including hematological malignancies such as acute myeloid leukemia, the most prevalent acute leukemia in adults. Xenobiotics are usually harmless compounds that may be detrimental, such as pharmaceuticals, environmental pollutants, cosmetics, and even food additives. The storage of xenobiotics can serve as a defense mechanism or a means of bioaccumulation, leading to adverse effects. During the absorption, metabolism, and cellular excretion of xenobiotics, three steps may be distinguished: (i) inflow by transporter enzymes, (ii) phases I and II, and (iii) phase III. Phase I enzymes, such as those in the cytochrome P450 superfamily, catalyze the conversion of xenobiotics into more polar compounds, contributing to an elevated acute myeloid leukemia risk. Furthermore, genetic polymorphism influences the variability and susceptibility of related myeloid neoplasms, infant leukemias associated with mixed-lineage leukemia (MLL) gene rearrangements, and a subset of de novo acute myeloid leukemia. Recent research has shown a sustained interest in determining the regulators of cytochrome P450, family 2, subfamily E, member 1 (CYP2E1) expression and activity as an emerging field that requires further investigation in acute myeloid leukemia evolution. Therefore, this review suggests that CYP2E1 and its mutations can be a therapeutic or diagnostic target in acute myeloid leukemia.

Transcriptomics of acute myeloid leukaemia core bone marrow biopsies reveals distinct therapy response-specific osteo-mesenchymal profiles

While the bone marrow (BM) microenvironment is significantly remodelled in acute myeloid leukaemia (AML), molecular insight into AML-specific alterations in the microenvironment has been historically limited by the analysis of liquid marrow aspirates rather than core biopsies that contain solid-phase BM stroma. We assessed the effect of anthracycline- and cytarabine-based induction chemotherapy on both haematopoietic and non-haematopoietic cells directly in core BM biopsies using RNA-seq and histological analysis. We compared matched human core BM biopsies at diagnosis and 2 weeks after cytarabine- and anthracycline-based induction therapy in responders (<5% blasts present after treatment) and non-responders (≥5% blasts present after treatment). Our data indicated enrichment in vimentin (VIM), platelet-derived growth factor receptor beta (PDGFRB) and Snail family transcriptional repressor 2 (SNAI2) transcripts in responders, consistent with the reactivation of the mesenchymal population in the BM stroma. Enrichment of osteoblast maturation-related transcripts of biglycan (BGN), osteopontin (SPP1) and osteonectin (SPARC) was observed in non-responders. To the best of our knowledge, this is the first report demonstrating distinct osteogenic and mesenchymal transcriptome profiles specific to AML response to induction chemotherapy assessed directly in core BM biopsies. Detailing treatment response-specific alterations in the BM stroma may inform optimised therapeutic strategies for AML.

Dexamethasone-Induced Fatty Acid Oxidation and Autophagy/Mitophagy Are Essential for T-ALL Glucocorticoid Resistance

ALL is a highly aggressive subtype of leukemia that affects children and adults. Glucocorticoids (GCs) are a critical component of the chemotherapeutic strategy against T-ALL. Cases of resistance to GC therapy and recurrent disease require novel strategies to overcome them. The present study analyzed the effects of Dex, one of the main GCs used in ALL treatment, on two T-ALL cell lines: resistant Jurkat and unselected CCRF-CEM, representing a mixture of sensitive and resistant clones. In addition to nuclear targeting, we observed a massive accumulation of Dex in mitochondria. Dex-treated leukemic cells suffered metabolic reprogramming from glycolysis and glutaminolysis towards lipolysis and increased FAO, along with increased membrane polarization and ROS production. Dex provoked mitochondrial fragmentation and induced autophagy/mitophagy. Mitophagy preceded cell death in susceptible populations of CCRF-CEM cells while serving as a pro-survival mechanism in resistant Jurkat. Accordingly, preventing FAO or autophagy greatly increased the Dex cytotoxicity and overcame GC resistance. Dex acted synergistically with mitochondria-targeted drugs, curcumin, and cannabidiol. Collectively, our data suggest that GCs treatment should not be neglected even in apparently GC-resistant clinical cases. Co-administration of drugs targeting mitochondria, FAO, or autophagy can help to overcome GC resistance.

Comprehensive analysis of the immune pattern of T cell subsets in chronic myeloid leukemia before and after TKI treatment

Background

Immunological phenotypes and differentiation statuses commonly decide the T cell function and anti-tumor ability. However, little is known about these alterations in CML patients.

Method

Here, we investigated the immunologic phenotypes (CD38/CD69/HLA-DR/CD28/CD57/BTLA/TIGIT/PD-1) of T subsets (TN, TCM, TEM, and TEMRA) in peripheral blood (PB) and bone marrow (BM) from de novo CML patients (DN-CML), patients who achieved a molecular response (MR) and those who failed to achieve an MR (TKI-F) after tyrosine kinase inhibitor (TKI) treatment using multicolor flow cytometry.

Results

CD38 or HLA-DR positive PB CD8+TN and TCM cells decreased in the DN-CML patients and this was further decreased in TKI-F patients. Meanwhile, the level of PD-1 elevated in CD8+ TEM and TEMRA cells from PB in all groups. Among BM sample, the level of HLA-DR+CD8+TCM cells significantly decreased in all groups and CD8+TEMRA cells from TKI-F patients exhibited increased level of TIGIT and CD8+ tissue-residual T cells (TRM) from DN-CML patients expressed a higher level of PD-1 and TIGIT. Lastly, we found a significantly decreased proportion of CD86+ dendritic cells (DCs) and an imbalanced CD80/CD86 in the PB and BM of DN-CML patients, which may impair the activation of T cells.

Conclusion

In summary, early differentiated TN and TCM cells from CML patients may remain in an inadequate activation state, particularly for TKI-F patients. And effector T cells (TEM, TEMRA and TRM) may be dysfunctional due to the expression of PD-1 and TIGIT in CML patients. Meanwhile, DCs cells exhibited the impairment of costimulatory molecule expression in DN-CML patients. Those factors may jointly contribute to the immune escape in CML patients.

Bone Marrow Microenvironment as a Source of New Drug Targets for the Treatment of Acute Myeloid Leukaemia

Acute myeloid leukaemia (AML) is a heterogeneous disease with one of the worst survival rates of all cancers. The bone marrow microenvironment is increasingly being recognised as an important mediator of AML chemoresistance and relapse, supporting leukaemia stem cell survival through interactions among stromal, haematopoietic progenitor and leukaemic cells. Traditional therapies targeting leukaemic cells have failed to improve long term survival rates, and as such, the bone marrow niche has become a promising new source of potential therapeutic targets, particularly for relapsed and refractory AML. This review briefly discusses the role of the bone marrow microenvironment in AML development and progression, and as a source of novel therapeutic targets for AML. The main focus of this review is on drugs that modulate/target this bone marrow microenvironment and have been examined in in vivo models or clinically.

Therapeutic resistance in acute myeloid leukemia cells is mediated by a novel ATM/mTOR pathway regulating oxidative phosphorylation

While leukemic cells are susceptible to various therapeutic insults, residence in the bone marrow microenvironment typically confers protection from a wide range of drugs. Thus, understanding the unique molecular changes elicited by the marrow is of critical importance toward improving therapeutic outcomes. In this study, we demonstrate that aberrant activation of oxidative phosphorylation serves to induce therapeutic resistance in FLT3 mutant human AML cells challenged with FLT3 inhibitor drugs. Importantly, our findings show that AML cells are protected from apoptosis following FLT3 inhibition due to marrow-mediated activation of ATM, which in turn upregulates oxidative phosphorylation via mTOR signaling. mTOR is required for the bone marrow stroma-dependent maintenance of protein translation, with selective polysome enrichment of oxidative phosphorylation transcripts, despite FLT3 inhibition. To investigate the therapeutic significance of this finding, we tested the mTOR inhibitor everolimus in combination with the FLT3 inhibitor quizartinib in primary human AML xenograft models. While marrow resident AML cells were highly resistant to quizartinib alone, the addition of everolimus induced profound reduction in tumor burden and prevented relapse. Taken together, these data provide a novel mechanistic understanding of marrow-based therapeutic resistance and a promising strategy for improved treatment of FLT3 mutant AML patients.

Modelling acute myeloid leukemia (AML): What's new? A transition from the classical to the modern

Acute myeloid leukemia (AML) is a heterogeneous malignancy affecting myeloid cells in the bone marrow (BM) but can spread giving rise to impaired hematopoiesis. AML incidence increases with age and is associated with poor prognostic outcomes. There has been a disconnect between the success of novel drug compounds observed in preclinical studies of hematological malignancy and less than exceptional therapeutic responses in clinical trials. This review aims to provide a state-of-the-art overview on the different preclinical models of AML available to expand insights into disease pathology and as preclinical screening tools. Deciphering the complex physiological and pathological processes and developing predictive preclinical models are key to understanding disease progression and fundamental in the development and testing of new effective drug treatments. Standard scaffold-free suspension models fail to recapitulate the complex environment where AML occurs. To this end, we review advances in scaffold/matrix-based 3D models and outline the most recent advances in on-chip technology. We also provide an overview of clinically relevant animal models and review the expanding use of patient-derived samples, which offer the prospect to create more "patient specific" screening tools either in the guise of 3D matrix models, microphysiological "organ-on-chip" tools or xenograft models and discuss representative examples.

Emerging translational strategies and challenges for enhancing regulatory T cell therapy for graft-versus-host disease

Allogeneic hematopoietic stem cell transplantation (allo-HSCT) is a curative therapy for many types of cancer. Genetic disparities between donor and host can result in immune-mediated attack of host tissues, known as graft versus host disease (GVHD), a major cause of morbidity and mortality following HSCT. Regulatory CD4+ T cells (Tregs) are a rare cell type crucial for immune system homeostasis, limiting the activation and differentiation of effector T cells (Teff) that are self-reactive or stimulated by foreign antigen exposure. Adoptive cell therapy (ACT) with Treg has demonstrated, first in murine models and now in patients, that prophylactic Treg infusion can also suppress GVHD. While clinical trials have demonstrated Treg reduce severe GVHD occurrence, several impediments remain, including Treg variability and practical need for individualized Treg production for each patient. Additionally, there are challenges in the use of in vitro expansion techniques and in achieving in vivo Treg persistence in context of both immune suppressive drugs and in lymphoreplete patients being treated for GVHD. This review will focus on 3 main translational approaches taken to improve the efficacy of tTreg ACT in GVHD prophylaxis and development of treatment options, following HSCT: genetic modification, manipulating TCR and cytokine signaling, and Treg production protocols. In vitro expansion for Treg ACT presents a multitude of approaches for gene modification to improve efficacy, including: antigen specificity, tissue targeting, deletion of negative regulators/exhaustion markers, resistance to immunosuppressive drugs common in GVHD treatment. Such expansion is particularly important in patients without significant lymphopenia that can drive Treg expansion, enabling a favorable Treg:Teff ratio in vivo. Several potential therapeutics have also been identified that enhance tTreg stability or persistence/expansion following ACT that target specific pathways, including: DNA/histone methylation status, TCR/co-stimulation signaling, and IL-2/STAT5 signaling. Finally, this review will discuss improvements in Treg production related to tissue source, Treg subsets, therapeutic approaches to increase Treg suppression and stability during tTreg expansion, and potential for storing large numbers of Treg from a single production run to be used as an off-the-shelf infusion product capable of treating multiple recipients.

DNA damage and repair on hematopoietic stem cells: impact of oxidative stress in renovascular hypertension

BACKGROUND

This study investigated oxidative damage to bone marrow cells in the pathogenesis of renovascular hypertension (RH).

METHODS

Male C57BL/6 J mice (10-week-old and ~23 g) were divided into two groups: Sham-operated and 2K1C, which has a stainless-steel clip placed around the left renal artery. After twenty-eight days, the animals were anesthetized for hemodynamic measurements and bone marrow cells isolation. The intracellular production of ROS, DNA damage, and DNA repair kinetics were evaluated.

RESULTS

Our results show that RH increases HSCs ROS production and that the 2K1C group showed a significant reduction of HSCs in the G0/G1 phase, increased p53 expression, DNA fragmentation, low DNA repair capacity, and a higher percentage of apoptotic cells when compared with the Sham group.

CONCLUSIONS

Our data imply that RH can compromise the hematopoiesis by increased oxidative stress leading to impaired DNA repair activity. Furthermore, this study provides new insights into the influence of hypertension on bone marrow homeostasis. This study showed for the first time that RH leads to oxidative damage, including genotoxic, to bone marrow cells. Thus, these findings provide new insights into the consequences of RH on bone marrow cells.

Bone Marrow Microenvironment-On-Chip for Culture of Functional Hematopoietic Stem Cells

Hematopoiesis takes place in the bone marrow and is supported by a complex cellular and molecular network in the bone marrow microenvironment. Commonly used models of the human bone marrow microenvironment include murine models and two-dimensional and three-dimensional tissue cultures. While these model systems have led to critical advances in the field, they fail to recapitulate many aspects of the human bone marrow. This has limited our understanding of human bone marrow pathophysiology and has led to deficiencies in therapy for many bone marrow pathologies such as bone marrow failure syndromes and leukemias. Therefore, we have developed a modular murine bone marrow microenvironment-on-chip using a commercially available microfluidic platform. This model includes a vascular channel separated from the bone marrow channel by a semi-porous membrane and incorporates critical components of the bone marrow microenvironment, including osteoblasts, endothelial cells, mesenchymal stem cells, and hematopoietic stem and progenitor cells. This system is capable of maintaining functional hematopoietic stem cells in vitro for at least 14 days at frequencies similar to what is found in the primary bone marrow. The modular nature of this system and its accessibility will allow for acceleration of our understanding of the bone marrow.

Acute Myeloid Leukemia Cells Educate Mesenchymal Stromal Cells toward an Adipogenic Differentiation Propensity with Leukemia Promotion Capabilities

Mesenchymal stromal cells (MSCs) are essential elements of the bone marrow (BM) microenvironment, which have been widely implicated in pathways that contribute to leukemia growth and resistance. Recent reports showed genotypic and phenotypic alterations in leukemia patient-derived MSCs, indicating that MSCs might be educated/reprogrammed. However, the results have been inconclusive, possibly due to the heterogeneity of leukemia. Here, the authors report that acute myeloid leukemia (AML) induces MSCs towards an adipogenic differentiation propensity. RNAseq analysis reveal significant upregulation of gene expression enriched in the adipocyte differentiation process and reduction in osteoblast differentiation. The alteration is accompanied by a metabolic switch from glycolysis to a more oxidative phosphorylation-dependent manner. Mechanistic studies identify that AML cell-derived exosomes play a vital role during the AML cell-mediated MSCs education/reprogramming process. Pre-administration of mice BM microenvironment with AML-derived exosomes greatly enhance leukemia engraftment in vivo. The quantitative proteomic analysis identified a list of exosomal protein components that are differently expressed in AML-derived exosomes, which represent an opportunity for novel therapeutic strategies based on the targeting of exosome-based AML cells-MSCs communication. Collectively, the data show that AML-educated MSCs tend to differentiate into adipocytes contributing to disease progression, which suggests complex interactions of leukemia with microenvironment components.

Role of CDH23 as a prognostic biomarker and its relationship with immune infiltration in acute myeloid leukemia

Background

Cadherin-23 (CDH23) plays an important role in intercellular adhesion and is involved in the progression of several types of cancer. However, the biological functions and effect of CDH23 expression on the prognosis of patients with acute myeloid leukemia (AML) are unexplored. Herein, we aim to characterize the role and molecular functions of CDH23 in AML.

Methods

We downloaded the transcriptomic profiles and clinical data from the Cancer Genome Atlas and Beat AML trial. The expression level of CDH23 was assessed using Gene Expression Profiling Interactive Analysis (GEPIA). Kaplan-Meier survival analysis was used to assess prognostic value of CDH23. Correlation and biological function analyses were performed using LinkedOmics and GeneMANIA. Relationship of CDH23 with immune infiltration level was determined using Tumor Immune Estimation Resource (TIMER).

Results

We found that the CDH23 expression was aberrantly upregulated in patients with AML and could be used as an independent risk factor of overall survival using Cox multivariate analysis. Notably, we observed a negative correlation between CDH23 expression and immune cell infiltration abundance by calculating the immune and stromal scores. In addition, functional enrichment analysis established that CDH23 plays a crucial role in tumor immunity.

Conclusions

Our findings indicate that upregulated CDH23 expression corresponds to decreased overall survival of patients with AML. CDH23 may be involved in mediating tumor immune environment, and this highlights the potential of CDH23 as a therapeutic target in AML.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12885-022-09532-1.

Cellular senescence in cancers: relationship between bone marrow cancer and cellular senescence

INTRODUCTION

There are many factors and conditions that lead to cellular senescence. Replicative senescence and Hayflick phenomenon are the most important causes of cellular senescence. Senescent cells also lead to wound healing conditions resulting from injury and toxic conditions.

MATERIAL AND METHODS

When a cell becomes senescent, it stops replication and begins to leak inflammatory signals before growth. It also alters the extracellular matrix and behavior of neighbor cells and even motivates them. This review was conducted to determine the association between senescence and bone marrow cancer.

RESULTS

The results showed that senescent cells have a short life span due to their self-destructive nature or natural removal from the body by the immune system. These signals are effective to a certain extent in regenerating the damaged cells when present in a transient state. Cellular senescence can decrease the risk of all cancers, including bone marrow cancer, ensuring that cells with significant DNA injury are prevented from replication.

CONCLUSION

However, senescent cells increase in number as they age, which is very harmful over time. These cells extend into an older tissue for longer periods of time and form longer clusters in older tissues. Therefore, cellular senescence significantly contributes to aging.

Taking the STING out of acute myeloid leukemia through macrophage-mediated phagocytosis

Macrophages within the bone marrow (BM) microenvironment take on unexpected roles in acute myeloid leukemia (AML) as reported by Moore and colleagues in this issue of the JCI. In contrast to solid tumors, where tumor-associated macrophages frequently assume an immunosuppressive phenotype that promotes tumor progression, this study revealed that BM macrophages repressed leukemia expansion in AML through a pathway called LC3-associated phagocytosis (LAP). After phagocytosis of dead and dying leukemic cells, including the mitochondria within the leukemic blasts, mitochondrial DNA activated stimulator of IFN genes (STING), leading to inflammatory signals that enhanced phagocytosis and restrained leukemic cell expansion. These findings unveil the modulation of macrophage-mediated phagocytosis via LAP as a potential therapeutic strategy directed at the BM microenvironment in AML.

DT7 peptide-modified lecithin nanoparticles co-loaded with γ-secretase inhibitor and dexamethasone efficiently inhibit T-cell acute lymphoblastic leukemia and reduce gastrointestinal toxicity

T-cell acute lymphoblastic leukemia (T-ALL) is a serious hematologic malignancy and glucocorticoid resistance is the main recurrent cause for a high relapsed and death rate. Here, we proposed an effective therapeutic regimen of combining gamma-secretase inhibitors (GSIs) with dexamethasone (DEX) to overcome glucocorticoid resistance. Moreover, the bone marrow targeting DT7 peptide-modified lecithin nanoparticles co-loaded with DEX and GSI (TLnp/D&G) were developed to enhance T-ALL cells recognition and endocytosis. In vitro cytotoxicity studies showed that TLnp/D&G significantly inhibited cell survival and promoted apoptosis of T-ALL cells. Mechanically, we found that GSIs promoted DEX-induced cell apoptosis by two main synergetic mechanisms: 1) GSIs significantly upregulated glucocorticoid receptor (GR) expression in T-ALL and restored the glucocorticoid-induced pro-apoptotic response. 2) Both DEX and GSI synergistically inhibited BCL2 and suppressed the survival of T-ALL cells. Furthermore, in vivo studies demonstrated that TLnp/D&G showed high bone marrow accumulation and better antileukemic efficacy both in leukemia bearing models and in systemic Notch1-induced T-ALL models, with excellent biosafety and reduced gastrointestinal toxicity. Overall, our study provides new strategies for the treatment of T-ALL and promising bone marrow targeting systems with high transformation potential.

Tetrandrine overcomes drug resistance mediated by bone marrow microenvironment by regulating the expression of P-glycoprotein in acute leukemia

Objectives: To study the effect of TET on the reversal of drug resistance in the bone marrow microenvironment, and to further promote the research on drug reversal.Methods: We established a co-culture system of bone marrow mesenchymal stem cells (BM-MSC) and K562 cell lines, and compared the cell inhibition rate of K562 cells between the co-culture group and K562 singleculture group by daunorubicin (DNR) single-drug intervention with CCK-8 and also compared K562 proliferation in the co-culture group and K562 single-culture group after combined intervention with DNR and TET, then used Western blot and RT-qPCR to verify the expression of P-gp of K562 cells at protein and mRNA levels, confirmed the concentration of DNR in K562 of different experimental groups by HPLC-MS.Results: According to the results of CCK-8, after co-culture with bone marrow mesenchymal stem cells (BM-MSCs), the inhibition rate of DNR on K562 decreased significantly. When TET (1μmol/L) combined with daunorubicin (DNR) treated on the co-culture group, the inhibition rate increased significantly. Then, the results of RT-qPCR and western blot showed a remarkable difference of the expression of P-glycoprotein (P-gp). After co-culture with BM-MSCs, the protein expression of P-gp showed a significant upward trend. After adding TET intervention, the expression of P-gp decreased both in mRNA and protein levels. Also, the DNR concentration in K562 also performed the correspondent trend.Conclusion: The bone marrow microenvironment can promote the MDR of acute leukemia. TET can reverse the MDR mediated by the bone marrow microenvironment by inhibiting the expression of P-glycoprotein.

Osteopontin is required for the maintenance of leukemia stem cells in acute myeloid leukemia

Acute myeloid leukemia (AML) is a heterogeneous hematopoietic disorder with a poor prognosis. The clinical significance of Leukemia stem cells (LSCs) plays an important role in the generation of AML and is the main cause of the recurrence after remission. Osteopontin (OPN), an extracellular matrix protein, has been implicated in hematopoietic malignancies. However, the specific role and the underlying mechanism of AML cell autocrined OPN in leukemia maintenance remain unknown. Here, we showed that knockdown of Opn expression significantly prolonged the survival of mice with MLL-AF9 cell-induced AML and markedly reduced the tumor burden. The LSCs from the Opn-knockdown groups exhibited decreased numbers and impaired function as determined by immunophenotype, colony-forming and limiting dilution assays. Further analysis revealed that Opn prevents LSCs from undergoing apoptosis and cell cycle arrest. Repression of OPN in human AML cell lines in vitro mimics the phenotypes observed in the mouse model. Overall, our data indicated that OPN is a potent therapeutic target for eradicating LSCs in AML.

Put in a “Ca2+ll” to Acute Myeloid Leukemia

Acute myeloid leukemia (AML) is a clonal disorder characterized by genetic aberrations in myeloid primitive cells (blasts) which lead to their defective maturation/function and their proliferation in the bone marrow (BM) and blood of affected individuals. Current intensive chemotherapy protocols result in complete remission in 50% to 80% of AML patients depending on their age and the AML type involved. While alterations in calcium signaling have been extensively studied in solid tumors, little is known about the role of calcium in most hematologic malignancies, including AML. Our purpose with this review is to raise awareness about this issue and to present (i) the role of calcium signaling in AML cell proliferation and differentiation and in the quiescence of hematopoietic stem cells; (ii) the interplay between mitochondria, metabolism, and oxidative stress; (iii) the effect of the BM microenvironment on AML cell fate; and finally (iv) the mechanism by which chemotherapeutic treatments modify calcium homeostasis in AML cells.

LC3-associated phagocytosis in bone marrow macrophages suppresses acute myeloid leukemia progression through STING activation

The bone marrow (BM) microenvironment regulates acute myeloid leukemia (AML) initiation, proliferation, and chemotherapy resistance. Following cancer cell death, a growing body of evidence suggests an important role for remaining apoptotic debris in regulating the immunologic response to and growth of solid tumors. Here, we investigated the role of macrophage LC3–associated phagocytosis (LAP) within the BM microenvironment of AML. Depletion of BM macrophages (BMMs) increased AML growth in vivo. We show that LAP is the predominate method of BMM phagocytosis of dead and dying cells in the AML microenvironment. Targeted inhibition of LAP led to the accumulation of apoptotic cells (ACs) and apoptotic bodies (ABs), resulting in accelerated leukemia growth. Mechanistically, LAP of AML-derived ABs by BMMs resulted in stimulator of IFN genes (STING) pathway activation. We found that AML-derived mitochondrial damage–associated molecular patterns were processed by BMMs via LAP. Moreover, depletion of mitochondrial DNA (mtDNA) in AML-derived ABs showed that it was this mtDNA that was responsible for the induction of STING signaling in BMMs. Phenotypically, we found that STING activation suppressed AML growth through a mechanism related to increased phagocytosis. In summary, we report that macrophage LAP of apoptotic debris in the AML BM microenvironment suppressed tumor growth.

Bone Cancer Detection Using Feature Extraction Based Machine Learning Model

Bone cancer is considered a serious health problem, and, in many cases, it causes patient death. The X-ray, MRI, or CT-scan image is used by doctors to identify bone cancer. The manual process is time-consuming and required expertise in that field. Therefore, it is necessary to develop an automated system to classify and identify the cancerous bone and the healthy bone. The texture of a cancer bone is different compared to a healthy bone in the affected region. But in the dataset, several images of cancer and healthy bone are having similar morphological characteristics. This makes it difficult to categorize them. To tackle this problem, we first find the best suitable edge detection algorithm after that two feature sets one with hog and another without hog are prepared. To test the efficiency of these feature sets, two machine learning models, support vector machine (SVM) and the Random forest, are utilized. The features set with hog perform considerably better on these models. Also, the SVM model trained with hog feature set provides an F1-score of 0.92 better than Random forest F1-score 0.77.

In vitro and in vivo effects of AVA4746, a novel competitive antagonist of the ligand binding of VLA-4, in B-cell acute lymphoblastic leukemia

Treatment of resistant or recurrent acute lymphoblastic leukemia (ALL) remains a challenge. It was previously demonstrated that the adhesion molecule integrin α4, referred to hereafter as α4, mediates the cell adhesion-mediated drug resistance (CAM-DR) of B-cell ALL by binding to vascular cell adhesion molecule-1 (VCAM-1) on bone marrow stroma. In addition, it was previously observed that the blockade of α4 with natalizumab or inhibition using the small molecule antagonist TBC3486 sensitized relapsed ALL cells to chemotherapy. However, α4-targeted therapy is not clinically available for the treatment of leukemia to date. In the present study, the use of a novel non-peptidic small molecule integrin α4 antagonist, AVA4746, as a potential new approach to combat drug-resistant B-ALL was explored. An in vitro co-culture = model of primary B-ALL cells and an in vivo xenograft model of patient-derived B-ALL cells were utilized for evaluation of AVA4746. VLA-4 conformation activation, cell adhesion/de-adhesion, endothelial tube formation, in vivo leukemia cell mobilization and survival assays were performed. AVA4746 exhibited high affinity for binding to B-ALL cells, where it also efficiently blocked ligand-binding to VCAM-1. In addition, AVA4746 caused the functional de-adhesion of primary B-ALL cells from VCAM-1. Inhibition of α4 using AVA4746 also prevented angiogenesis in vitro and when applied in combination with chemotherapy consisting of Vincristine, Dexamethasone and L-asparaginase, it prolonged the survival of ~33% of the mice in an in vivo xenograft model of B-ALL. These data implicate the potential of targeting the α4-VCAM-1 interaction using AVA4746 for the treatment of drug-resistant B-lineage ALL.

Bone marrow microenvironment drives AML cell OXPHOS addiction and AMPK inhibition to resist chemotherapy

The stromal niche plays a pivotal role in AML chemoresistance and energy metabolism reprogramming is a hallmark of a tumor. 5′‐Adenosine monophosphate‐activated protein kinase (AMPK) is an important energy sensor suppressing mammalian target of rapamycin complex 1 (mTORC1) activity. However, the role of AMPK‐mTORC1 pathway on connecting AML cell energy metabolism reprogramming and chemoresistance induced by the bone marrow microenvironment (BMM) is not defined. Here, with a co‐culture system that simulates the interaction between BMM and AML cells, it is shown that stromal contact led to a decreased sensitivity to chemotherapy accompanied by an increase of oxidative phosphorylation (OXPHOS) activity and mitochondrial ATP synthesis in AML cells. The increased OXPHOS activity and excessive ATP production promoted chemoresistance of AML cells through inhibiting AMPK activity and in turn activating mTORC1 activity. In an in vivo AML mouse model, depletion of AMPK activity with genetic targeting promoted AML progression and reduced their sensitivity to chemotherapeutic drugs. Collectively, AML cells’ acquired increased OXPHOS activity as well as AMPK inhibition could be therapeutically exploited in an effort to overcome BMM‐mediated chemoresistance.

The Bone Marrow Microenvironment Mechanisms in Acute Myeloid Leukemia

Bone marrow (BM) is a highly complex tissue that provides important regulatory signals to orchestrate hematopoiesis. Resident and transient cells occupy and interact with some well characterized niches to produce molecular and cellular mechanisms that interfere with differentiation, migration, survival, and proliferation in this microenvironment. The acute myeloid leukemia (AML), the most common and severe hematological neoplasm in adults, arises and develop in the BM. The osteoblastic, vascular, and reticular niches provide surface co-receptors, soluble factors, cytokines, and chemokines that mediate important functions on hematopoietic cells and leukemic blasts. There are some evidences of how AML modify the architecture and function of these three BM niches, but it has been still unclear how essential those modifications are to maintain AML development. Basic studies and clinical trials have been suggesting that disturbing specific cells and molecules into the BM niches might be able to impair leukemia competencies. Either through niche-specific molecule inhibition alone or in combination with more traditional drugs, the bone marrow microenvironment is currently considered the potential target for new strategies to treat AML patients. This review describes the cellular and molecular constitution of the BM niches under healthy and AML conditions, presenting this anatomical compartment by a new perspective: as a prospective target for current and next generation therapies.