Increased angiogenesis in the bone marrow of patients with acute myeloid leukemia

Inhibition of TGF-β signaling in bone marrow endothelial cells promotes hematopoietic recovery in acute myeloid leukemia patients

Although it is an effective treatment for acute myeloid leukemia (AML), chemotherapy leads to myelosuppression and poor hematopoietic reconstruction. Hematopoiesis is regulated by bone marrow (BM) endothelial cells (ECs), and BM ECs are dysfunctional in acute leukemia patients with poor hematopoietic reconstitution after allogenic hematopoietic stem cell transplantation. Thus, it is crucial to explore the underlying mechanism of EC impairment and establish strategies for targeted therapy. TGF-β signaling was found to be upregulated in ECs from AML patients in complete remission (CR ECs) and led to CR EC damage. Administration of a TGF-β inhibitor rescued the dysfunction of ECs caused by TGF-β1 expression in vitro, especially their hematopoiesis-supporting ability. Moreover, inhibition of TGF-β expression repaired the BM EC damage triggered by chemotherapy in both AML patients in vitro and in an AML-CR murine model, and restored normal hematopoiesis without promoting AML progression. Mechanistically, our data reveal alterations in the transcriptomic pattern of damaged BM ECs, accompanied by the overexpression of downstream molecules TGF-βR1, pSmad2/3, and functional genes related to adhesion, angiogenesis suppression and pro-apoptosis. Collectively, our findings reveal for the first time that the activation of TGF-β signaling leads to BM EC dysfunction and poor hematopoietic reconstitution. Targeting TGF-β represents a potential therapeutic strategy to promote multilineage hematopoiesis, thereby benefiting more cancer patients who suffer from myelosuppression after chemotherapy.

Transforming the Niche: The Emerging Role of Extracellular Vesicles in Acute Myeloid Leukaemia Progression

Acute myeloid leukaemia (AML) management remains a significant challenge in oncology due to its low survival rates and high post-treatment relapse rates, mainly attributed to treatment-resistant leukaemic stem cells (LSCs) residing in bone marrow (BM) niches. This review offers an in-depth analysis of AML progression, highlighting the pivotal role of extracellular vesicles (EVs) in the dynamic remodelling of BM niche intercellular communication. We explore recent advancements elucidating the mechanisms through which EVs facilitate complex crosstalk, effectively promoting AML hallmarks and drug resistance. Adopting a temporal view, we chart the evolving landscape of EV-mediated interactions within the AML niche, underscoring the transformative potential of these insights for therapeutic intervention. Furthermore, the review discusses the emerging understanding of endothelial cell subsets' impact across BM niches in shaping AML disease progression, adding another layer of complexity to the disease progression and treatment resistance. We highlight the potential of cutting-edge methodologies, such as organ-on-chip (OoC) and single-EV analysis technologies, to provide unprecedented insights into AML-niche interactions in a human setting. Leveraging accumulated insights into AML EV signalling to reconfigure BM niches and pioneer novel approaches to decipher the EV signalling networks that fuel AML within the human context could revolutionise the development of niche-targeted therapy for leukaemia eradication.

The Clinical Significance and Involvement in Molecular Cancer Processes of Chemokine CXCL1 in Selected Tumors

Chemokines play a key role in cancer processes, with CXCL1 being a well-studied example. Due to the lack of a complete summary of CXCL1's role in cancer in the literature, in this study, we examine the significance of CXCL1 in various cancers such as bladder, glioblastoma, hemangioendothelioma, leukemias, Kaposi's sarcoma, lung, osteosarcoma, renal, and skin cancers (malignant melanoma, basal cell carcinoma, and squamous cell carcinoma), along with thyroid cancer. We focus on understanding how CXCL1 is involved in the cancer processes of these specific types of tumors. We look at how CXCL1 affects cancer cells, including their proliferation, migration, EMT, and metastasis. We also explore how CXCL1 influences other cells connected to tumors, like promoting angiogenesis, recruiting neutrophils, and affecting immune cell functions. Additionally, we discuss the clinical aspects by exploring how CXCL1 levels relate to cancer staging, lymph node metastasis, patient outcomes, chemoresistance, and radioresistance.

Semaphorins and the bone marrow microenvironment: New candidates that influence the hematopoietic system

The bone marrow is a haven for hematopoietic and non-hematopoietic cells, creating complex micro-anatomical regions called niches. These distinct niches all participate in an intricate orchestra of cellular interactions that regulates the hematopoietic stem cell and its progenies. In this review, we provide a detailed description of the three most well-known bone marrow niches and their participation in hematopoiesis. We use pre-clinical data, including different in vitro and in vivo studies to discuss how a group of proteins called Semaphorins could potentially modulate both hematopoietic and non-hematopoietic cells, establishing links between the niches, semaphorins, and hematopoietic regulation. Thus, here we provide a deep dive into the inner functioning of the bone marrow and discuss the overarching implications that semaphorins might have on blood formation.

Ocular pharmacological and biochemical profiles of 6-thioguanine: a drug repurposing study

Introduction

The purine analog 6-thioguanine (6TG), an old drug approved in the 60s to treat acute myeloid leukemia (AML), was tested in the diabetic retinopathy (DR) experimental in vivo setting along with a molecular modeling approach.

Methods

A computational analysis was performed to investigate the interaction of 6TG with MC1R and MC5R. This was confirmed in human umbilical vein endothelial cells (HUVECs) exposed to high glucose (25 mM) for 24 h. Cell viability in HUVECs exposed to high glucose and treated with 6TG (0.05-0.5-5 µM) was performed. To assess tube formation, HUVECs were treated for 24 h with 6TG 5 µM and AGRP (0.5-1-5 µM) or PG20N (0.5-1-5-10 µM), which are MC1R and MC5R antagonists, respectively. For the in vivo DR setting, diabetes was induced in C57BL/6J mice through a single streptozotocin (STZ) injection. After 2, 6, and 10 weeks, diabetic and control mice received 6TG intravitreally (0.5-1-2.5 mg/kg) alone or in combination with AGRP or PG20N. Fluorescein angiography (FA) was performed after 4 and 14 weeks after the onset of diabetes. After 14 weeks, mice were euthanized, and immunohistochemical analysis was performed to assess retinal levels of CD34, a marker of endothelial progenitor cell formation during neo-angiogenesis.

Results

The computational analysis evidenced a more stable binding of 6TG binding at MC5R than MC1R. This was confirmed by the tube formation assay in HUVECs exposed to high glucose. Indeed, the anti-angiogenic activity of 6TG was eradicated by a higher dose of the MC5R antagonist PG20N (10 µM) compared to the MC1R antagonist AGRP (5 µM). The retinal anti-angiogenic effect of 6TG was evident also in diabetic mice, showing a reduction in retinal vascular alterations by FA analysis. This effect was not observed in diabetic mice receiving 6TG in combination with AGRP or PG20N. Accordingly, retinal CD34 staining was reduced in diabetic mice treated with 6TG. Conversely, it was not decreased in diabetic mice receiving 6TG combined with AGRP or PG20N.

Conclusion

6TG evidenced a marked anti-angiogenic activity in HUVECs exposed to high glucose and in mice with DR. This seems to be mediated by MC1R and MC5R retinal receptors.

IL-2/CD25 axis mediates cellular networks promoting the growth of CD25+ acute myeloid leukemia cells

Although the expression of interleukin-2 receptor α-chain (IL-2Rα, CD25) has been provided prognostic significance independent of known biomarkers in acute myeloid leukemia (AML), the functional role of CD25 molecule remains unknown. Since IL-2 can be trans-presented via CD25 to another cell, CD25+AML cells may deliver environmental IL-2 to surrounding immune cells to produce myeloid growth factors for their proliferation. We hypothesize that cellular interactions via IL-2/CD25 axis in the bone marrow microenvironment contributes to the growth advantage of these AML cells and affects the clinical outcome of those AML patients.

The Role of CXCR1, CXCR2, CXCR3, CXCR5, and CXCR6 Ligands in Molecular Cancer Processes and Clinical Aspects of Acute Myeloid Leukemia (AML)

Acute myeloid leukemia (AML) is a type of leukemia known for its unfavorable prognoses, prompting research efforts to discover new therapeutic targets. One area of investigation involves examining extracellular factors, particularly CXC chemokines. While CXCL12 (SDF-1) and its receptor CXCR4 have been extensively studied, research on other CXC chemokine axes in AML is less developed. This study aims to bridge that gap by providing an overview of the significance of CXC chemokines other than CXCL12 (CXCR1, CXCR2, CXCR3, CXCR5, and CXCR6 ligands and CXCL14 and CXCL17) in AML's oncogenic processes. We explore the roles of all CXC chemokines other than CXCL12, in particular CXCL1 (Gro-α), CXCL8 (IL-8), CXCL10 (IP-10), and CXCL11 (I-TAC) in AML tumor processes, including their impact on AML cell proliferation, bone marrow angiogenesis, interaction with non-leukemic cells like MSCs and osteoblasts, and their clinical relevance. We delve into how they influence prognosis, association with extramedullary AML, induction of chemoresistance, effects on bone marrow microvessel density, and their connection to French-American-British (FAB) classification and FLT3 gene mutations.

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.

Hematopoietic Stem Cells and Their Bone Marrow Niches

Hematopoietic stem cells (HSCs) are maintained in the bone marrow microenvironment, also known as the niche, that regulates their proliferation, self-renewal, and differentiation. In this chapter, we will introduce the history of HSC niche research and review the interdependencies between HSCs and their niches. We will further highlight recent advances in our understanding of HSC heterogeneity with regard to HSC subpopulations and their interacting cellular and molecular bone marrow niche constituents.

A randomized phase 2 trial of nintedanib and low-dose cytarabine in elderly patients with acute myeloid leukemia ineligible for intensive chemotherapy

We investigated the safety and efficacy of nintedanib added to low-dose cytarabine (LDAC) in a phase 1/2 study in patients 60 years or older with newly diagnosed or relapsed/refractory (r/r) AML ineligible for intensive chemotherapy. The results of the dose-finding phase 1 part have been previously published. Patients were randomized 1:1 to LDAC plus nintedanib or LDAC plus placebo stratified by AML status (newly diagnosed vs r/r). LDAC was applied subcutaneously at 20 mg twice daily on days 1 to 10. Nintedanib/placebo was orally administered twice daily on days 1 to 28 in 28-day cycles. The primary endpoint was overall survival (OS). Between 05/2017 and 09/2019, 31 patients were randomized and 30 were treated, before the study was terminated prematurely due to slow recruitment. Median (range) age of patients was 76 (60-84) years. Twenty-two patients (73%) had r/r AML. Median OS in patients treated with LDAC and nintedanib was 3.4 months, compared with 3.6 months in those treated in the placebo arm, with a HR adjusted for AML status of 1.19 (corresponding confirmatory adjusted 95% CI, 0.55-2.56; univariate log-rank P = 0.96). In the 22 patients with r/r AML, median OS was 3.0 months in the nintedanib and 3.6 months in the placebo arm (P = 0.36). One patient in the nintedanib and two patients in the placebo arm achieved a CR and entered maintenance treatment. Nintedanib showed no superior therapeutic activity over placebo when added to LDAC in elderly AML patients considered unfit for intensive chemotherapy. The trial was registered at clinicaltrials.gov NCT01488344.

A nonrandomized phase I and biomarker trial of regorafenib in advanced myeloid malignancies

We conducted a single-center, open-label, dose escalation, and expansion phase I trial of the antiangiogenic multikinase inhibitor regorafenib in patients with advanced myeloid neoplasms. We enrolled 16 patients with relapsed/refractory acute myeloid leukemia (AML), myeloproliferative neoplasms (MPN), chronic myelomonocytic leukemia (CMML), or myelodysplastic syndrome (MDS). A 3 + 3 dose escalation design was used with two planned dose levels (120 or 160 mg daily) and one de-escalation level (80 mg daily). An additional 10 patients were treated on an expansion cohort. The recommended phase two dose of regorafenib was 160 mg daily, with no dose-limiting toxicities. The best overall disease response by International Working Group criteria included one partial and stable disease in 11 patients. Tissue studies indicated no change in Ras/mitogen-activated protein kinase (MAPK) pathway activation in responders. Pharmacodynamic changes in plasma VEGF, PlGF, and sVEGFR2 were detected during treatment. Baseline proinflammatory and angiogenic cytokine levels were not associated with clinical response. Single-agent regorafenib demonstrated an acceptable safety profile in relapsed/refractory myeloid malignancy patients. Most patients achieved stable disease, with modest improvements in cell counts in some MDS patients. Biomarker studies were consistent with on-target effects of regorafenib on angiogenesis. Future studies should investigate the role of regorafenib in combination therapy approaches.

Targeting CD38 in acute myeloid leukemia interferes with leukemia trafficking and induces phagocytosis

Targeting the interaction between leukemic cells and the microenvironment is an appealing approach to enhance the therapeutic efficacy in acute myeloid leukemia (AML). AML infiltration induces a significant release of inflammatory cytokines in the human bone marrow niche which accelerates leukemogenesis. As the transmembrane glycoprotein CD38 has been shown to regulate cytokine release, we assessed the anti-leukemic potential of CD38 inhibition in AML. CD38 expression in AML cells proved to depend on microenvironmental cues and could be significantly enforced through addition of tretinoin. In fact, the anti-CD38 antibody daratumumab showed significant cytostatic efficacy in a 3D in vitro triple-culture model of AML, but with modest cell-autonomous cytotoxic activity and independent of CD38 expression level. In line with a predominantly microenvironment-mediated activity of daratumumab in AML, CD38 inhibition significantly induced antibody-dependent phagocytosis and showed interference with AML cell trafficking in vivo in a xenograft transplantation model, but overall lacked robust anti-leukemic effects.

Blood Vessels and Peripheral Nerves as Key Players in Cancer Progression and Therapy Resistance

Simple Summary

The interactions between cancer cells and the surrounding blood vessels and peripheral nerves are critical in all the phases of tumor development. Accordingly, therapies that specifically target vessels and nerves represent promising anticancer approaches. The first aim of this review is to document the importance of blood vessels and peripheral nerves in both cancer onset and local or distant growth of tumoral cells. We then focus on the state-of-the-art therapies that limit cancer progression through the impairment of blood vessels and peripheral nerves. The mentioned literature is helpful for the scientific community to appreciate the recent advances in these two fundamental components of tumors.

Abstract

Cancer cells continuously interact with the tumor microenvironment (TME), a heterogeneous milieu that surrounds the tumor mass and impinges on its phenotype. Among the components of the TME, blood vessels and peripheral nerves have been extensively studied in recent years for their prominent role in tumor development from tumor initiation. Cancer cells were shown to actively promote their own vascularization and innervation through the processes of angiogenesis and axonogenesis. Indeed, sprouting vessels and axons deliver several factors needed by cancer cells to survive and proliferate, including nutrients, oxygen, and growth signals, to the expanding tumor mass. Nerves and vessels are also fundamental for the process of metastatic spreading, as they provide both the pro-metastatic signals to the tumor and the scaffold through which cancer cells can reach distant organs. Not surprisingly, continuously growing attention is devoted to the development of therapies specifically targeting these structures, with promising initial results. In this review, we summarize the latest evidence that supports the importance of blood vessels and peripheral nerves in cancer pathogenesis, therapy resistance, and innovative treatments.

Leukaemia: a model metastatic disease

In contrast to solid cancers, which often require genetic modifications and complex cellular reprogramming for effective metastatic dissemination, leukaemic cells uniquely possess the innate ability for migration and invasion. Dedifferentiated, malignant leukocytes retain the benign leukocytes' capacity for cell motility and survival in the circulation, while acquiring the potential for rapid and uncontrolled cell division. For these reasons, leukaemias, although not traditionally considered as metastatic diseases, are in fact models of highly efficient metastatic spread. Accordingly, they are often aggressive and challenging diseases to treat. In this Perspective, we discuss the key molecular processes that facilitate metastasis in a variety of leukaemic subtypes, the clinical significance of leukaemic invasion into specific tissues and the current pipeline of treatments targeting leukaemia metastasis.

The Role of Hypoxic Bone Marrow Microenvironment in Acute Myeloid Leukemia and Future Therapeutic Opportunities

Acute myeloid leukemia (AML) is a hematologic malignancy caused by a wide range of alterations responsible for a high grade of heterogeneity among patients. Several studies have demonstrated that the hypoxic bone marrow microenvironment (BMM) plays a crucial role in AML pathogenesis and therapy response. This review article summarizes the current literature regarding the effects of the dynamic crosstalk between leukemic stem cells (LSCs) and hypoxic BMM. The interaction between LSCs and hypoxic BMM regulates fundamental cell fate decisions, including survival, self-renewal, and proliferation capacity as a consequence of genetic, transcriptional, and metabolic adaptation of LSCs mediated by hypoxia-inducible factors (HIFs). HIF-1α and some of their targets have been associated with poor prognosis in AML. It has been demonstrated that the hypoxic BMM creates a protective niche that mediates resistance to therapy. Therefore, we also highlight how hypoxia hallmarks might be targeted in the future to hit the leukemic population to improve AML patient outcomes.

Cell interactions in the bone marrow microenvironment affecting myeloid malignancies

The bone marrow is a complex tissue in which heterogeneous populations of stromal cells interact with hematopoietic cells to dynamically respond to organismal needs in defense, hemostasis, and oxygen delivery. Physiologic challenges modify stromal/hematopoietic cell interactions to generate changes in blood cell production. When either stroma or hematopoietic cells are impaired, the system distorts. The distortions associated with myeloid malignancy are reviewed here and may provide opportunities for therapeutic intervention.

The Dynamic Interface Between the Bone Marrow Vascular Niche and Hematopoietic Stem Cells in Myeloid Malignancy

Hematopoietic stem cells interact with bone marrow niches, including highly specialized blood vessels. Recent studies have revealed the phenotypic and functional heterogeneity of bone marrow endothelial cells. This has facilitated the analysis of the vascular microenvironment in steady state and malignant hematopoiesis. In this review, we provide an overview of the bone marrow microenvironment, focusing on refined analyses of the marrow vascular compartment performed in mouse studies. We also discuss the emerging role of the vascular niche in “inflamm-aging” and clonal hematopoiesis, and how the endothelial microenvironment influences, supports and interacts with hematopoietic cells in acute myeloid leukemia and myelodysplastic syndromes, as exemplar states of malignant myelopoiesis. Finally, we provide an overview of strategies for modulating these bidirectional interactions to therapeutic effect in myeloid malignancies.

Effects of lenalidomide on the bone marrow microenvironment in acute myeloid leukemia: Translational analysis of the HOVON103 AML/SAKK30/10 Swiss trial cohort

This translational study aimed at gaining insight into the effects of lenalidomide in acute myeloid leukemia (AML). Forty-one AML patients aged 66 or older of the Swiss cohort of the HOVON-103 AML/SAKK30/10 study were included. After randomization, they received standard induction chemotherapy with or without lenalidomide. Bone marrow biopsies at diagnosis and before the 2nd induction cycle were obtained to assess the therapeutic impact on leukemic blasts and microenvironment. Increased bone marrow angiogenesis, as assessed by microvessel density (MVD), was found at AML diagnosis and differed significantly between the WHO categories. Morphological analysis revealed a higher initial MVD in AML with myelodysplasia-related changes (AML-MRC) and a more substantial decrease of microvascularization after lenalidomide exposure. A slight increase of T-bet-positive TH1-equivalents was identifiable under lenalidomide. In the subgroup of patients with AML-MRC, the progression-free survival differed between the two treatment regimens, showing a potential but not significant benefit of lenalidomide. We found no correlation between the cereblon genotype (the target of lenalidomide) and treatment response or prognosis. In conclusion, addition of lenalidomide may be beneficial to elderly patients suffering from AML-MRC, where it leads to a reduction of microvascularization and, probably, to an intensified specific T cell-driven anti-leukemic response.

Sorafenib or placebo in patients with newly diagnosed acute myeloid leukaemia: long-term follow-up of the randomized controlled SORAML trial

Early results of the randomized placebo-controlled SORAML trial showed that, in patients with newly diagnosed acute myeloid leukaemia (AML), sorafenib led to a significant improvement in event-free (EFS) and relapse-free survival (RFS). In order to describe second-line treatments and their implications on overall survival (OS), we performed a study after a median follow-up time of 78 months. Newly diagnosed fit AML patients aged ≤60 years received sorafenib (n = 134) or placebo (n = 133) in addition to standard chemotherapy and as maintenance treatment. The 5-year EFS was 41 versus 27% (HR 0.68; p = 0.011) and 5-year RFS was 53 versus 36% (HR 0.64; p = 0.035). Allogeneic stem cell transplantation (allo SCT) was performed in 88% of the relapsed patients. Four years after salvage allo SCT, the cumulative incidence of relapse was 54 versus 35%, and OS was 32 versus 50%. The 5-year OS from randomization in all study patients was 61 versus 53% (HR 0.82; p = 0.282). In conclusion, the addition of sorafenib to chemotherapy led to a significant prolongation of EFS and RFS. Although the OS benefit did not reach statistical significance, these results confirm the antileukaemic activity of sorafenib.

The extracellular matrix: A key player in the pathogenesis of hematologic malignancies

Hematopoietic stem and progenitor cells located in the bone marrow lay the foundation for multiple lineages of mature hematologic cells. Bone marrow niches are architecturally complex with specific cellular, physiochemical, and biomechanical factors. Increasing evidence suggests that the bone marrow microenvironment contributes to the pathogenesis of hematological neoplasms. Numerous studies have deciphered the role of genetic mutations and chromosomal translocations in the development hematologic malignancies. Significant progress has also been made in understanding how the cellular components and cytokine interactions within the bone marrow microenvironment promote the evolution of hematologic cancers. Although the extracellular matrix is known to be a key player in the pathogenesis of various diseases, it's role in the progression of hematologic malignancies is less understood. In this review, we discuss the interactions between the extracellular matrix and malignant cells, and provide an overview of the role of extracellular matrix remodeling in sustaining hematologic malignancies.

Anti-angiogenic activity of ShengMaBieJia decoction in vitro and in acute myeloid leukaemia tumour-bearing mouse models

Context: ShengMaBieJia decoction (SMBJD) is used to treat solid and hematological tumours; however, its anti-angiogenesis activity remains unclear.Objective: This study verified the anti-angiogenic effects of SMBJD in vitro and in tumour-bearing acute myeloid leukaemia (AML) mouse models.Materials and methods: In vivo, the chicken chorioallantoic membrane (CAM) and BALB/c null mouse xenograft models were treated with SMBJD (0, 2, 4, and 8 mg/mL) for 48 h and for 2 weeks, respectively. Anti-angiogenic activity was assessed according to microvessel density (MVD) and immunohistochemistry (IHC) targeting CD31 and VEGFR2. In vitro, proliferation viability, migratory activity and tube formation were measured. Western blots and polymerase chain reaction (PCR) assays were used to examine the levels of PI3K, Akt, and VEGF.Results: HPLC analyses revealed the active constituents of SMBJD such as liquiritin, cimifugin, ferulic, isoferulic, and glycyrrhizic acids. In vitro, SMBJD treatment decreased cellular migration, chemotaxis, and tube formation at non-cytotoxic concentrations (2, 4, and 8 mg/mL) in a time- and dose-dependent manner. The dosage of less than IC₂₀ is considered safe. In vivo, CAM models exhibited a decrease in MVD, and the tissues of xenografted mice possessed reduced CD31 and VEGFR2 expression. Conditioned media (CM) from AML cells (HL60 and NB4 cells) treated with non-cytotoxic doses of SMBJD inhibited chemotactic migration and tube formation in vitro. Both CM (HL60) and CM (NB4) exhibited downregulated expression of PI3K, Akt, and VEGF.Discussion and conclusions: SMBJD inhibited angiogenesis in AML through the PI3K/AKT pathway, which might be combined with targeted therapy to provide more effective treatment.

Insights into the mechanism of Arnebia euchroma on leukemia via network pharmacology approach

BACKGROUND

Arnebia euchroma (A. euchroma) is a traditional Chinese medicine (TCM) used for the treatment of blood diseases including leukemia. In recent years, many studies have been conducted on the anti-tumor effect of shikonin and its derivatives, the major active components of A. euchroma. However, the underlying mechanism of action (MoA) for all the components of A. euchroma on leukemia has not been explored systematically.

METHODS

In this study, we analyzed the MoA of A. euchroma on leukemia via network pharmacology approach. Firstly, the chemical components and their concentrations in A. euchroma as well as leukemia-related targets were collected. Next, we predicted compound-target interactions (CTIs) with our balanced substructure-drug-target network-based inference (bSDTNBI) method. The known and predicted targets of A. euchroma and leukemia-related targets were merged together to construct A. euchroma-leukemia protein-protein interactions (PPIs) network. Then, weighted compound-target bipartite network was constructed according to combination of eight central attributes with concentration information through Cytoscape. Additionally, molecular docking simulation was performed to calculate whether the components and predicted targets have interactions or not.

RESULTS

A total of 65 components of A. euchroma were obtained and 27 of them with concentration information, which were involved in 157 targets and 779 compound-target interactions (CTIs). Following the calculation of eight central attributes of targets in A. euchroma-leukemia PPI network, 37 targets with all central attributes greater than the median values were selected to construct the weighted compound-target bipartite network and do the KEGG pathway analysis. We found that A. euchroma candidate targets were significantly associated with several apoptosis and inflammation-related biological pathways, such as MAPK signaling, PI3K-Akt signaling, IL-17 signaling, and T cell receptor signaling pathways. Moreover, molecular docking simulation demonstrated that there were eight pairs of predicted CTIs had the strong binding free energy.

CONCLUSIONS

This study deciphered that the efficacy of A. euchroma in the treatment of leukemia might be attributed to 10 targets and 14 components, which were associated with inhibiting leukemia cell survival and inducing apoptosis, relieving inflammatory environment and inhibiting angiogenesis.

Human fibronectin extra domain B as a biomarker for targeted therapy in cancer

The extracellular matrix protein fibronectin contains a domain that is rarely found in healthy adults and is almost exclusively expressed by newly formed blood vessels in tumours, particularly in solid tumours, different types of lymphoma and some leukaemias. This domain, called the extra domain B (ED‐B), thus has broad therapeutic potential. The antibody L19 has been developed to specifically target ED‐B and has shown therapeutic potential when combined with cytokines, such as IL‐2. In this review article, we discuss the preclinical research and clinical trials that highlight the potential of ED‐B targeting for the imaging and treatment of various types of cancer. ED‐B‐centred studies also highlight how proper patient stratification is of utmost importance for the successful implementation of novel antibody‐based targeted therapies.

Anti-VEGF Drugs in the Treatment of Multiple Myeloma Patients

The interaction between the bone marrow microenvironment and plasma cells plays an essential role in multiple myeloma progression and drug resistance. The vascular endothelial growth factor (VEGF)/VEGF receptor (VEGFR) pathway in vascular endothelial cells activates and promotes angiogenesis. Moreover, VEGF activates and promotes vasculogenesis and vasculogenic mimicry when it interacts with VEGF receptors expressed in precursor cells and inflammatory cells, respectively. In myeloma bone marrow, VEGF and VEGF receptor expression are upregulated and hyperactive in the stromal and tumor cells. It has been demonstrated that several antiangiogenic agents can effectively target VEGF-related pathways in the preclinical phase. However, they are not successful in treating multiple myeloma, probably due to the vicarious action of other cytokines and signaling pathways. Thus, the simultaneous blocking of multiple cytokine pathways, including the VEGF/VEGFR pathway, may represent a valid strategy to treat multiple myeloma. This review aims to summarize recent advances in understanding the role of the VEGF/VEGFR pathway in multiple myeloma, and mainly focuses on the transcription pathway and on strategies that target this pathway.

The Neurokinin-1 Receptor Antagonist Aprepitant, a New Drug for the Treatment of Hematological Malignancies: Focus on Acute Myeloid Leukemia

Acute myeloid leukemia (AML) is a heterogeneous hematological malignancy. To treat the disease successfully, new therapeutic strategies are urgently needed. One of these strategies can be the use of neurokinin-1 receptor (NK-1R) antagonists (e.g., aprepitant), because the substance P (SP)/NK-1R system is involved in cancer progression, including AML. AML patients show an up-regulation of the NK-1R mRNA expression; human AML cell lines show immunoreactivity for both SP and the NK-1R (it is overexpressed: the truncated isoform is more expressed than the full-length form) and, via this receptor, SP and NK-1R antagonists (aprepitant, in a concentration-dependent manner) respectively exert a proliferative action or an antileukemic effect (apoptotic mechanisms are triggered by promoting oxidative stress via mitochondrial Ca⁺⁺ overload). Aprepitant inhibits the formation of AML cell colonies and, in combination with chemotherapeutic drugs, is more effective in inducing cytotoxic effects and AML cell growth blockade. NK-1R antagonists also exert an antinociceptive effect in myeloid leukemia-induced bone pain. The antitumor effect of aprepitant is diminished when the NF-κB pathway is overactivated and the damage induced by aprepitant in cancer cells is higher than that exerted in non-cancer cells. Thus, the SP/NK-1R system is involved in AML, and aprepitant is a promising antitumor strategy against this hematological malignancy. In this review, the involvement of this system in solid and non-solid tumors (in particular in AML) is updated and the use of aprepitant as an anti-leukemic strategy for the treatment of AML is also mentioned (a dose of aprepitant (>20 mg/kg/day) for a period of time according to the response to treatment is suggested). Aprepitant is currently used in clinical practice as an anti-nausea medication.

The bone marrow stromal niche: a therapeutic target of hematological myeloid malignancies

Introduction: Myeloid malignancies are caused by uncontrolled proliferation of neoplastic cells and lack of mature hematopoietic cells. Beside intrinsic genetic and epigenetic alterations within the neoplastic population, abnormal function of the bone marrow stroma promotes the neoplastic process. To overcome the supportive action of the microenvironment, recent research focuses on the development of targeted therapies, inhibiting the interaction of malignant cells and niche cells.Areas covered: This review covers regulatory networks and potential druggable pathways within the hematopoietic stem cell niche. Recent insights into the cell-to-cell interactions in the bone marrow microenvironment are presented. We performed literature searches using PubMed Database from 2000 to the present.Expert opinion: Future therapy of myeloid malignancies must focus on targeted, personalized treatment addressing specific alterations within the malignant and the supporting niche cells. This includes treatments to overcome resistance mechanisms against chemotherapeutic agents mediated by supporting microenvironment. Novel techniques employing sequencing approaches, Crisp/Cas9, or transgenic mouse models are required to elucidate specific interactions between components of the bone marrow niche to identify new therapeutic targets.

7‑Difluoromethyl‑5,4'‑dimethoxygenistein exerts anti‑angiogenic effects on acute promyelocytic leukemia HL‑60 cells by inhibiting the TLR4/NF‑κB signaling pathway

Angiogenesis plays an important role in the development and metastasis of tumors, and anti-angiogenesis agents are used to treat tumors. For example, the acute promyelocytic leukemia (APL) may be treated with arsenic trioxide. Angiogenesis in APL is a multi-step dynamic equilibrium process coordinated by various angiogenic stimulators and inhibitors, which play key roles in the occurrence, progression and chemosensitivity of this disease. Our research group previously synthesized 7-difluoromethyl-5,4′-dimethoxygenistein (DFMG), and found that it inhibits angiogenesis during atherosclerotic plaque formation. In the present study, the effect and mechanism of DFMG in angiogenesis induced by APL HL-60 cells was investigated using a chick embryo chorioallantoic membrane model and Matrigel tubule formation assays. The results obtained revealed an anti-angiogenesis effect of DFMG towards HL-60 cells. When the Toll-like receptor 4/nuclear factor-κB (TLR4/NF-κB) signaling pathway was inhibited, the anti-angiogenic effect of DFMG was further enhanced. However, when the TLR4/NF-κB signaling pathway was activated, the anti-angiogenic effect of DFMG was attenuated. These results demonstrated that DFMG inhibits angiogenesis induced by APL HL-60 cells, and provides insights into the mechanism by which DFMG inhibits the TLR4/NF-κB signaling pathway. In conclusion, in the present study, the anti-angiogenesis effect of DFMG on APL has been reported, and the mechanism by which DFMG induced the anti-angiogenesis effect was explored. These findings have provided a potential new drug candidate for the treatment of patients with APL.

Cellular and molecular architecture of hematopoietic stem cells and progenitors in genetic models of bone marrow failure

Inherited bone marrow failure syndromes, such as Fanconi anemia (FA) and Shwachman-Diamond syndrome (SDS), feature progressive cytopenia and a risk of acute myeloid leukemia (AML). Using deep phenotypic analysis of early progenitors in FA/SDS bone marrow samples, we revealed selective survival of progenitors that phenotypically resembled granulocyte-monocyte progenitors (GMP). Whole-exome and targeted sequencing of GMP-like cells in leukemia-free patients revealed a higher mutation load than in healthy controls and molecular changes that are characteristic of AML: increased G>A/C>T variants, decreased A>G/T>C variants, increased trinucleotide mutations at Xp(C>T)pT, and decreased mutation rates at Xp(C>T)pG sites compared with other Xp(C>T)pX sites and enrichment for Cancer Signature 1 (X indicates any nucleotide). Potential preleukemic targets in the GMP-like cells from patients with FA/SDS included SYNE1, DST, HUWE1, LRP2, NOTCH2, and TP53. Serial analysis of GMPs from an SDS patient who progressed to leukemia revealed a gradual increase in mutational burden, enrichment of G>A/C>T signature, and emergence of new clones. Interestingly, the molecular signature of marrow cells from 2 FA/SDS patients with leukemia was similar to that of FA/SDS patients without transformation. The predicted founding clones in SDS-derived AML harbored mutations in several genes, including TP53, while in FA-derived AML the mutated genes included ARID1B and SFPQ. We describe an architectural change in the hematopoietic hierarchy of FA/SDS with remarkable preservation of GMP-like populations harboring unique mutation signatures. GMP-like cells might represent a cellular reservoir for clonal evolution.

Role of VEGFs/VEGFR-1 Signaling and its Inhibition in Modulating Tumor Invasion: Experimental Evidence in Different Metastatic Cancer Models

The vascular endothelial growth factor (VEGF) family members, VEGF-A, placenta growth factor (PlGF), and to a lesser extent VEGF-B, play an essential role in tumor-associated angiogenesis, tissue infiltration, and metastasis formation. Although VEGF-A can activate both VEGFR-1 and VEGFR-2 membrane receptors, PlGF and VEGF-B exclusively interact with VEGFR-1. Differently from VEGFR-2, which is involved both in physiological and pathological angiogenesis, in the adult VEGFR-1 is required only for pathological angiogenesis. Besides this role in tumor endothelium, ligand-mediated stimulation of VEGFR-1 expressed in tumor cells may directly induce cell chemotaxis and extracellular matrix invasion. Furthermore, VEGFR-1 activation in myeloid progenitors and tumor-associated macrophages favors cancer immune escape through the release of immunosuppressive cytokines. These properties have prompted a number of preclinical and clinical studies to analyze VEGFR-1 involvement in the metastatic process. The aim of the present review is to highlight the contribution of VEGFs/VEGFR-1 signaling in the progression of different tumor types and to provide an overview of the therapeutic approaches targeting VEGFR-1 currently under investigation.

Vascularized Microfluidics and the Blood-Endothelium Interface

The microvasculature is the primary conduit through which the human body transmits oxygen, nutrients, and other biological information to its peripheral tissues. It does this through bidirectional communication between the blood, consisting of plasma and non-adherent cells, and the microvascular endothelium. Current understanding of this blood-endothelium interface has been predominantly derived from a combination of reductionist two-dimensional in vitro models and biologically complex in vivo animal models, both of which recapitulate the human microvasculature to varying but limited degrees. In an effort to address these limitations, vascularized microfluidics have become a platform of increasing importance as a consequence of their ability to isolate biologically complex phenomena while also recapitulating biochemical and biophysical behaviors known to be important to the function of the blood-endothelium interface. In this review, we discuss the basic principles of vascularized microfluidic fabrication, the contribution this platform has made to our understanding of the blood-endothelium interface in both homeostasis and disease, the limitations and challenges of these vascularized microfluidics for studying this interface, and how these inform future directions.

Correlation of histological marrow characteristics and intravoxel incoherent motion-derived parameters in benign and malignant hematological disorders

PURPOSE

To investigate the relationship between intravoxel incoherent motion (IVIM) parameters and histological parameters of vascularity and cellularity in marrow of hyperplasia disease and compare the difference between benign and malignant marrow disorders.

METHODS

From August 2016 to March 2017, 43 newly diagnosed patients were recruited, which included 15 anemia patients (benign hemopathy) and 28 patients with acute leukemia (AL) (malignant hemopathy). All patients underwent IVIM in the lumbar marrow and the D, D*, f values were measured. The microvessel density (MVD) and cellularity of marrow were calculated from the sample of iliac crest biopsy. Pearson correlation analysis was used to study the relationship between IVIM-derived and histology-derived parameters. We performed unpaired t test to analyze the differences of all parameters between AL and anemia.

RESULT

The MVD was positively correlated with f in patients with AL, anemia and both of them (r = 0.692, P < 0.001; r = 0.595, P = 0.019; r = 0.673, P < 0.001, respectively). But there was no correlation between D* and MVD in three groups. D was not related to bone marrow cellularity (BMC) in all groups. In addition, the f and MVD were higher in AL than anemia (t = 3.546, P = 0.001; t = 6.695, P < 0.001, respectively). The BMC was significantly higher in AL than in anemia (t = 3.330, P = 0.004), but D and D* value had no significant difference between the two groups.

CONCLUSION

The blood volume fraction f was positively correlated with the histological features of marrow in hematological disorders, while f can show the difference of vascularity between benign and malignant marrow disease.

Targeting Leukemia Stem Cell-Niche Dynamics: A New Challenge in AML Treatment

One of the most urgent needs in AML is to improve the disease cure rate as relapse still occurs in 60–80% of patients. Recent evidence suggests that dismal clinical outcomes may be improved by a better definition of the tight interaction between the AML cell population and the bone marrow (BM) microenvironment (“the niche”); the latter has been progressively highlighted to have an active role in the disease process. It has now been well established that the leukemic population may misinterpret niche-derived signals and remodel the niche, providing a shelter to AML cells and protecting them from the cytotoxic effects of chemoradiotherapy. Novel imaging technological advances and preclinical disease models have revealed that, due to the finite number of BM niches, leukemic stem cells (LSCs) and normal hematopoietic stem cells (HSCs) compete for the same functional areas. Thus, the removal of LSCs from the BM niche and the promotion of normal HSC engraftment should be the primary goals in antileukemic research. In addition, it is now becoming increasingly clear that AML-niche dynamics are disease stage specific. In AML, the niche has been linked to disease pathogenesis in the preleukemic stage, the niche becomes permissive once leukemic cells are established, and the niche is transformed into a self-reinforcing structure at a later disease stage. These concepts have been fostered by the demonstration that, in unrelated AML types, endosteal vessel loss occurs as a primary AML-induced niche alteration, and additional AML-induced alterations of the niche and normal hematopoiesis evolve focally and in parallel. Obviously, this endosteal vessel loss plays a fundamental role in AML pathogenesis by causing excessive vascular permeability, hypoxia, altered perfusion, and reduced drug delivery. Each of these alterations may be effectively targeted by various therapeutic procedures, but preservation of endosteal vessel integrity might be the best option for any future antileukemic treatment.

Interleukin-8 blockade prevents activated endothelial cell mediated proliferation and chemoresistance of acute myeloid leukemia

One of the greatest challenges in treating acute myeloid leukemia (AML) is chemotherapy refractory disease. Previously, we demonstrated a novel mechanism whereby AML-induced endothelial cell (EC) activation leads to subsequent leukemia cell adherence, quiescence and chemoresistance, identifying activated ECs as potential mediators of relapse. We now show mechanistically that EC activation induces the secretion of interleukin-8 (IL-8) leading to significant expansion of non-adherent AML cells and resistance to cytarabine (Ara-C). Through crystallography and computational modeling, we identified a pocket within IL-8 responsible for receptor binding, screened for small molecules that fit within this pocket, and blocked IL-8 induced proliferation and chemo-protection of AML cells with a hit compound. Results from this study show a new therapeutic strategy for targeting the sanctuary of an activated leukemia microenvironment.

Overexpression of heme oxygenase-1 in microenvironment mediates vincristine resistance of B-cell acute lymphoblastic leukemia by promoting vascular endothelial growth factor secretion

Chemoresistance often causes treatment failure of B-cell acute lymphoblastic leukemia (B-ALL). However, the mechanism remains unclear at present. Herein, overexpression of heme oxygenase-1 (HO-1) was found in the bone marrow stromal cells (BMSCs) from B-ALL patients developing resistance to vincristine (VCR), a chemotherapeutic agent. Two B-ALL cell lines Super B15 and CCRF-SB were cocultured with BMSCs transfected with lentivirus to regulate the expression of HO-1. Silencing HO-1 expression in BMSCs increased the apoptotic rates of B-ALL cell lines induced by VCR, whereas upregulating HO-1 expression reduced the rate. Cell cycle can be arrested in the G2/M phase by VCR. In contrast, B-ALL cells were arrested in the G0/G1 phase due to HO-1 overexpression in BMSCs, which avoided damage from the G2/M phase. Vascular endothelial growth factor (VEGF) in BMSCs, as a key factor in the microenvironment-associated chemoresistance, was also positively coexpressed with HO-1. VEGF secretion was markedly increased in BMSCs with HO-1 upregulation but decreased in BMSCs with HO-1 silencing. B-ALL cell lines became resistant to VCR when cultured with VEGF recombinant protein, so VEGF secretion induced by HO-1 expression may promote the VCR resistance of B-ALL cells. As to the molecular mechanism, the PI3K/AKT pathway mediated regulation of VEGF by HO-1. In conclusion, this study clarifies a mechanism by which B-ALL is induced to resist VCR through HO-1 overexpression in BMSCs, and provides a novel strategy for overcoming VCR resistance in clinical practice.

The neuropeptide receptor calcitonin receptor-like (CALCRL) is a potential therapeutic target in acute myeloid leukemia

Calcitonin receptor-like (CALCRL) is a G-protein-coupled neuropeptide receptor involved in the regulation of blood pressure, angiogenesis, cell proliferation, and apoptosis, and is currently emerging as a novel target for the treatment of migraine. This study characterizes the role of CALCRL in acute myeloid leukemia (AML). We analyzed CALCRL expression in collectively more than 1500 well-characterized AML patients from five international cohorts (AMLCG, HOVON, TCGA, Leucegene, and UKM) and evaluated associations with survival. In the AMLCG analytic cohort, increasing transcript levels of CALCRL were associated with decreasing complete remission rates (71.5%, 53.7%, 49.6% for low, intermediate, high CALCRL expression), 5-year overall (43.1%, 26.2%, 7.1%), and event-free survival (29.9%, 15.8%, 4.7%) (all P < 0.001). CALCRL levels remained associated with all endpoints on multivariable regression analyses. The prognostic impact was confirmed in all validation sets. Genes highly expressed in CALCRL^high AML were significantly enriched in leukemic stem cell signatures and CALCRL levels were positively linked to the engraftment capacity of primary patient samples in immunocompromised mice. CRISPR-Cas9-mediated knockout of CALCRL significantly impaired colony formation in human myeloid leukemia cell lines. Overall, our study demonstrates that CALCRL predicts outcome beyond existing risk factors and is a potential therapeutic target in AML.

The Expression of the SLIT-ROBO Family in Adult Patients with Acute Myeloid Leukemia

INTRODUCTION

SLIT-ROBO is a ligand-receptor family of neuronal guidance cues that has been involved in pathological and physiological angiogenesis. SLIT-ROBO expression is altered in many tumours. However, no data exist about the role of the whole family in acute myelogenous myeloid leukemia (AML).

PURPOSE

Herein, we assessed the expression of all SLIT-ROBO family in bone marrow (BM) biopsy of AML patients and control group on both protein and RNA levels.

METHODS

The paraffin-embedded tissue blocks were subjected to immunohistochemistry for SLIT1, SLIT2, SLIT3, ROBO1, ROBO2, ROBO3, and ROBO4. Microvessel density (MVD) was evaluated by CD34 immunohistochemistry. An in silico analysis using The Cancer Genome Atlas data repository was conducted for assessment of RNA level.

RESULTS

Acute myeloid leukemia patients were generally high expressers of ROBO1 and ROBO2 compared to the controls (p < 0.0001, p < 0.001, respectively). In contrast, low expression of SLIT1, SLIT2, and SLIT3 ligands has been noted more commonly in AML than in control BM samples (p < 0.0001, p = 0.003, and p = 0.001, respectively). ROBO4 expression correlated with MVD. The in silico analysis showed a poor prognostic value of high ROBO3 and low SLIT2 RNA levels (p = 0.0003 and p = 0.0008, respectively), as well as high ROBO3 and ROBO4 RNA levels in cytogenetic poor risk groups of patients (p = 0.0029 and p = 0.0003, respectively).

CONCLUSIONS

These data indicate that SLIT-ROBO family members play a role in the biology of AML. Low expression of SLIT in BM of AML patients may suggest its expression alterations in AML. Increased expression of ROBO1 and ROBO2 in AML patients suggests their participation in AML pathogenesis.

Acute Myeloid Leukemia and the Bone Marrow Niche-Take a Closer Look

The bone marrow is the home of hematopoiesis and is therefore a hotspot for the development of hematopoietic diseases. Complex interactions between the bone marrow microenvironment and hematopoietic stem cells must find a balance between proliferation, differentiation and homeostasis of the stem cell compartment. Changes in this tightly regulated network can provoke malignant transformation, leading to hematopoietic diseases. Here we focus on acute myeloid leukemia (AML), since this is the most frequent acute leukemia in adulthood with very poor overall survival rates and where relapse after chemotherapy continues to be a major challenge, driving demand for new therapeutic strategies. Current research is focusing on the identification of specific interactions between leukemic blasts and their niche components, which may be exploited as novel treatment targets along with induction chemotherapy. Significant progress has been gained over the last few years in the field of high-resolution imaging. Confocal ex vivo and intravital microscopy have revealed a detailed map of bone marrow structures and components; as well as identifying numerous alterations in the stem cell niche that correspond to disease progression. However, the underlying mechanisms are still not completely understood and due to the complexity, their elucidation remains a challenging. This review discusses the constitution of the AML niche in the bone marrow, the improvement in visualization of the complex three-dimensional niche structures and points out new therapeutic strategies to increase the overall survival of AML patients.

Hematopoiesis and microenvironment in hematological malignancies

Adult hematopoietic stem cells (HSCs) and progenitors (HPCs) reside in the bone marrow, a highly orchestrated architecture. In the bone marrow, the process of how HSCs exert self-renewal and differentiation is tightly regulated by the surrounding microenvironment, or niche. Recent advances in imaging technologies and numerous knockout or knockin mouse models have greatly improved our understanding of the organization of the bone marrow niche. This niche compartment includes a complex network of mesenchymal stem cells (MSC), osteolineage cells, endothelial cells (arterioles and sinusoids), sympathetic nerves, nonmyelinating Schwann cells and megakaryocytes. In addition, different types of mediators, such as cytokines/chemokines, reactive oxygen species (ROS) and exosomes play a pivotal role in regulating the function of hematopoietic cells. Therefore, the niche components and the hematopoietic system make up an ecological environment that maintains the homeostasis and responds to stress, damage or disease conditions. On the other hand, the niche compartment can become a traitor that can do harm to normal hematopoietic cells under pathological conditions. Studies on the diseased bone marrow niche have only recently begun to appear in the extant literature. In this short review, we discuss the most recent advances regarding the behaviors of normal hematopoietic cells and their niche alterations in hematological malignancies.

Nanomedicines for the treatment of hematological malignancies

Hematological malignancies (HM) are a collection of malignant transformations originating from cells in the primary or secondary lymphoid organs. Leukemia, lymphoma, and multiple myeloma comprise the three major types of HM. Current treatment consists of bone marrow transplantation, radiotherapy, immunotherapy and chemotherapy. Although, many chemotherapeutic drugs are clinically available for the treatment of HM, the use of these agents is limited due to dose-related toxicity and lack of specificity to tumor tissue. Moreover, the poor pharmacokinetic profile of most of the chemotherapeutics requires high dosage and frequent administration to maintain therapeutic levels at the target site, both increasing adverse effects. This underlines an urgent need for a suitable drug delivery system to improve efficacy, safety, and pharmacokinetic properties of conventional therapeutics. Nanomedicines have proven to enhance these properties for anticancer therapeutics. The most extensively studied nanomedicine systems are lipid-based nanoparticles and polymeric nanoparticles. Typically, nanomedicines are small sub-micron sized particles in the size range of 20-200 nm. The biocompatible and biodegradable nature of nanomedicines makes them attractive vehicles to improve drug delivery. Their small size allows them to extravasate and accumulate at malignant sites passively by means of the enhanced permeability and retention (EPR) effect, resulting from rapid angiogenesis and inflammation. Moreover, the specificity to the target tissue can be further enhanced by surface modification of nanoparticles. This review describes currently available therapies as well as limitations and potential advantages of nanomedicine formulations for treatment of various types of HM. Additionally, recent investigational and approved nanomedicine formulations and their limited applications in HM are discussed.

Wogonoside impedes the progression of acute myeloid leukemia through inhibiting bone marrow angiogenesis

Decreasing bone marrow (BM) microvessel density and circulating angiogenic cytokine levels are promising strategies for the treatment of relapsed and resistant acute myeloid leukemia (AML). Previous studies have reported that wogonoside could inhibit the progression of AML and suppress angiogenesis in a solid tumor, but the correlation of these two effects was ignored. In this research, we determined whether wogonoside could inhibit angiogenesis in this hematologic malignancy. We found that wogonoside could inhibit tumor growth and progression, and prolong the survival of nude mice inoculated with U937/MDR. Besides, reducing BM angiogenesis might cause therapeutic effect against resistant AML. Therefore, coculture between AML cells and BM stromal cells was established to imitate their crosstalk. Then, the effect of wogonoside on BM angiogenesis was tested in vitro and in vivo. We found that wogonoside could suppress microvessel formation in the chicken chorioallantoic membrane assay model and matrigel plug assay. The mechanism research revealed that wogonoside could block the JAK2-STAT3 pathway in AML cells and stromal cells to break their positive feedback. We detected several cytokines related to AML or angiogenesis and found that secreted interleukin-8 was a significant angiogenic cytokine to induce BM angiogenesis. These findings supported that new diagnostics and promising treatment strategies could be developed in relapsed and resistant AML patients.

IL-2/IL-3 interplay mediates growth of CD25 positive acute myeloid leukemia cells

Cell surface interleukin-2 receptor α-chain (IL-2Rα, CD25) expression is currently recognized to be a strong predictor for poor prognosis in patients with acute myeloid leukemia (AML). However, it is still unknown that the reason why CD25 positive AML patients have a dismal clinical outcome. CD25 positive AML cells are generally unresponsive to IL-2, but strongly respond to IL-3. The levels of IL-3Rα on these AML cells are very high and directly proportional to the CD25 levels. T-lymphocytes produce IL-3 in response to stimuli including IL-2-mediated activation. Thus, CD25 on AML cells may capture environmental IL-2 and deliver it to the surrounding T-lymphocytes expressing IL-2Rβ/γc, leading to the production of IL-3 as a growth stimulus to CD25 positive AML cells. We hypothesize that IL-2/IL-3 interplay via CD25 is responsible for the growth property of CD25 positive AML, which may affect clinical behavior of those patients.

Expression of functional neuronal receptor latrophilin 1 in human acute myeloid leukaemia cells

Acute myeloid leukaemia (AML) is a blood cancer affecting cells of myeloid lineage. It is characterised by rapid growth of malignant leukocytes that accumulate in the bone marrow and suppress normal haematopoiesis. This systemic disease remains a serious medical burden worldwide. Characterisation of protein antigens specifically expressed by malignant cells, but not by healthy leukocytes, is vital for the diagnostics and targeted treatment of AML. Here we report, for the first time, that the neuronal receptor latrophilin-1 is expressed in human monocytic leukaemia cell lines and in primary human AML cells. However, it is absent in healthy leukocytes. Latrophilin-1 is functional in leukaemia cells tested, and its biosynthesis is controlled through the mammalian target of rapamycin (mTOR), a master regulator of myeloid cell translational pathways. Our findings demonstrate that latrophilin-1 could be considered as a novel biomarker of human AML, which offers potential new avenues for AML diagnosis and treatment.

Inhibition of Endosteal Vascular Niche Remodeling Rescues Hematopoietic Stem Cell Loss in AML

Bone marrow vascular niches sustain hematopoietic stem cells (HSCs) and are drastically remodeled in leukemia to support pathological functions. Acute myeloid leukemia (AML) cells produce angiogenic factors, which likely contribute to this remodeling, but anti-angiogenic therapies do not improve AML patient outcomes. Using intravital microscopy, we found that AML progression leads to differential remodeling of vasculature in central and endosteal bone marrow regions. Endosteal AML cells produce pro-inflammatory and anti-angiogenic cytokines and gradually degrade endosteal endothelium, stromal cells, and osteoblastic cells, whereas central marrow remains vascularized and splenic vascular niches expand. Remodeled endosteal regions have reduced capacity to support non-leukemic HSCs, correlating with loss of normal hematopoiesis. Preserving endosteal endothelium with the small molecule deferoxamine or a genetic approach rescues HSCs loss, promotes chemotherapeutic efficacy, and enhances survival. These findings suggest that preventing degradation of the endosteal vasculature may improve current paradigms for treating AML.

The microenvironment in myelodysplastic syndromes: Niche-mediated disease initiation and progression

Myelodysplastic syndromes (MDSs) are clonal disorders of hematopoietic stem and progenitor cells and represent the most common cause of acquired marrow failure. Hallmarked by ineffective hematopoiesis, dysplastic marrow, and risk of transformation to acute leukemia, MDS remains a poorly treated disease. Although identification of hematopoietic aberrations in human MDS has contributed significantly to our understanding of MDS pathogenesis, evidence now identify the bone marrow microenvironment (BMME) as another key contributor to disease initiation and progression. With improved understanding of the BMME, we are beginning to refine the role of the hematopoietic niche in MDS. Despite genetic diversity in MDS, interaction between MDS and the BMME appears to be a common disease feature and therefore represents an appealing therapeutic target. Further understanding of the interdependent relationship between MDS and its niche is needed to delineate the mechanisms underlying hematopoietic failure and how the microenvironment can be targeted clinically. This review provides an overview of data from human MDS and murine models supporting a role for BMME dysfunction at several steps of disease pathogenesis. Although no models or human studies so far have combined all of these findings, we review current data identifying BMME involvement in each step of MDS pathogenesis organized to reflect the chronology of BMME contribution as the normal hematopoietic system becomes myelodysplastic and MDS progresses to marrow failure and transformation. Although microenvironmental heterogeneity and dysfunction certainly add complexity to this syndrome, data are already demonstrating that targeting microenvironmental signals may represent novel therapeutic strategies for MDS treatment.