(Lymph)angiogenic influences on hematopoietic cells in acute myeloid leukemia

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.

Therapeutic potential of FLT4-targeting peptide in acute myeloid leukemia

Previously, we found that dysfunctional natural killer (NK) cells with low interferon gamma (IFN-γ) were restored in acute myeloid leukemia (AML) by the FLT4 antagonist MAZ51. Here, we developed 12 peptides targeting FLT4 for clinical application and examined whether they restored the frequency of lymphocytes, especially T cells and NK cells, and high IFN-γ expression, as MAZ51 treatment did in our previous study. Although clinical data from using peptides are currently available, peptides targeting FLT4 to modulate immune cells have not been fully elucidated. In this study, we focus on novel peptide 4 (P4) from the intracellular domain of FLT4 because it had dominant negative activity. Similar to MAZ51, high IFN-γ levels were expressed in AML-mononuclear cells exposed to P4. Additionally, T and NK cell levels were restored, as were high IFN-γ levels, in a leukemic environment when P4 was treated. Interestingly, the regulatory T cells were significantly decreased by P4, implying the role of peptide in tumor niche. Overall, we demonstrated the therapeutic value of functionally modulating lymphocytes using a peptide targeting FLT4 and proposed the development of advanced therapeutic approaches against AML by using immune cells.

γδ T Cells for Leukemia Immunotherapy: New and Expanding Trends

Recently, many discoveries have elucidated the cellular and molecular diversity in the leukemic microenvironment and improved our knowledge regarding their complex nature. This has allowed the development of new therapeutic strategies against leukemia. Advances in biotechnology and the current understanding of T cell-engineering have led to new approaches in this fight, thus improving cell-mediated immune response against cancer. However, most of the investigations focus only on conventional cytotoxic cells, while ignoring the potential of unconventional T cells that until now have been little studied. γδ T cells are a unique lymphocyte subpopulation that has an extensive repertoire of tumor sensing and may have new immunotherapeutic applications in a wide range of tumors. The ability to respond regardless of human leukocyte antigen (HLA) expression, the secretion of antitumor mediators and high functional plasticity are hallmarks of γδ T cells, and are ones that make them a promising alternative in the field of cell therapy. Despite this situation, in particular cases, the leukemic microenvironment can adopt strategies to circumvent the antitumor response of these lymphocytes, causing their exhaustion or polarization to a tumor-promoting phenotype. Intervening in this crosstalk can improve their capabilities and clinical applications and can make them key components in new therapeutic antileukemic approaches. In this review, we highlight several characteristics of γδ T cells and their interactions in leukemia. Furthermore, we explore strategies for maximizing their antitumor functions, aiming to illustrate the findings destined for a better mobilization of γδ T cells against the tumor. Finally, we outline our perspectives on their therapeutic applicability and indicate outstanding issues for future basic and clinical leukemia research, in the hope of contributing to the advancement of studies on γδ T cells in cancer immunotherapy.

Increased circulating basic fibroblast growth factor levels in acute myeloid leukemia: a meta-analysis

Background: Basic fibroblast growth factor (bFGF) plays an important role in the pathogenesis of acute myeloid leukemia (AML). Whether the levels of circulating bFGF are increased or not in untreated AML patients is still not clear. In order to acquire a more definite evaluation, a meta-analysis was performed.Material and methods: We searched PubMed, Embase, the Cochrane Library, China National Knowledge Infrastructure (CNKI), Wanfang, and VIP databases for possible eligible articles. Forest plot was used to present the combined effect values and 95% confidence intervals (CI) through the random-effect model. Subgroup analysis was performed based on sample size, sample type, and region. All statistical analysis was performed in STATA12.0 software.Results: After excluding the articles that did not meet the inclusion criteria, 11 studies that met the inclusion conditions were included in this meta-analysis. Overall, AML patients probably had higher circulating levels of bFGF (SMD = 1.15, 95% CI: 0.35-1.94). The results of sensitivity analysis indicated that the results were stable. Moreover, the trim and fill analysis showed that publication bias had little effect and the results were relatively robust. In addition, AML patients with N < 30 group, serum group, and Asia group (all P < 0.05) had higher circulating bFGF levels, whereas other subgroups showed no significant change.Conclusion: The results of current meta-analysis revealed that AML patients had higher circulating bFGF levels, and it was associated with sample type, sample size, and region. Considering the possible pathogenic role of bFGF in AML, drug development targeting bFGF is very promising for AML patients.

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.

Danggui Buxue Tang promotes the adhesion and migration of bone marrow stromal cells via the focal adhesion pathway in vitro

ETHNOPHARMACOLOGY RELEVANCE

Danggui Buxue Tang has been used in China to treat clinical anemia for more than 800 years. However, there is no scientific report on its effect on bone marrow stromal cells.

AIM OF THE STUDY

Here, we aimed to explore the effect of Danggui Buxue Tang on bone marrow stromal cell adhesion and migration.

MATERIALS AND METHODS

Bone marrow stromal cells were used as a model to evaluate the effect of Danggui Buxue Tang on the adhesion and migration of bone marrow stromal cells. RNA-sequencing, quantitative polymerase chain reaction, and western blotting were used to detect and confirm the expression of genes related to the focal adhesion pathway before and after drug delivery.

RESULTS

Danggui Buxue Tang significantly increased the number of bone marrow stromal cells. After 12 days of 16 mg/mL Danggui Buxue Tang treatment, bone marrow stromal cells were significantly increased (by 0.527 ± 0.008 fold; p < 0.001) as compared to the control group (0.180 ± 0.019). The effect was not due to enhanced cell proliferation, as there was no difference in the cell cycle (p > 0.05). The adhesion area of a single cell was doubled by Danggui Buxue Tang treatment (p < 0.001), and the time required for cell adhesion to a Petri dish was shortened. Thus, Danggui Buxue Tang increases the number of bone marrow stromal cells by promoting adhesion. Danggui Buxue Tang also significantly promoted bone marrow stromal cell migration (p <  0.001). Transcript analysis revealed that the focal adhesion and PI3K-Akt signaling pathways were activated. Expression analysis confirmed that the gene and protein expression of focal adhesion-related factors were upregulated.

CONCLUSION

Danggui Buxue Tangaffects bone marrow stromal cell adhesion and migration by enhancing the focal adhesion pathway in vitro, and bone marrow stromal cells are a target of DBT-regulated hematopoiesis, and the active ingredients of DBT involved in the effects require further investigation.

Increased Vascular Permeability in the Bone Marrow Microenvironment Contributes to Disease Progression and Drug Response in Acute Myeloid Leukemia

The biological and clinical behaviors of hematological malignancies can be influenced by the active crosstalk with an altered bone marrow (BM) microenvironment. In the present study, we provide a detailed picture of the BM vasculature in acute myeloid leukemia using intravital two-photon microscopy. We found several abnormalities in the vascular architecture and function in patient-derived xenografts (PDX), such as vascular leakiness and increased hypoxia. Transcriptomic analysis in endothelial cells identified nitric oxide (NO) as major mediator of this phenotype in PDX and in patient-derived biopsies. Moreover, induction chemotherapy failing to restore normal vasculature was associated with a poor prognosis. Inhibition of NO production reduced vascular permeability, preserved normal hematopoietic stem cell function, and improved treatment response in PDX.

Angiogenesis in Liquid Tumors: An In Vitro Assay for Leukemic-Cell-Induced Bone Marrow Angiogenesis

The critical role of angiogenesis for solid tumor growth and metastatic spread has been well established. In contrast, even though increased vascularity has been commonly observed in bone marrows of patients with hematological malignancies (liquid tumors), the pathophysiology of leukemia-induced angiogenesis in the bone marrow remains elusive. This paper demonstrates the usage of a microengineered 3D biomimetic model to study leukemic-cell-induced bone marrow angiogenesis. Rational design of the 3D angiogenesis chip incorporating endothelial cells (ECs), leukemic cells, and bone marrow stromal fibroblasts provide an efficient biomimetic means to promote and visualize early angiogenic processes. Morphological features of angiogenesis induced by three different leukemic cell lines (U937, HL60, and K562) are investigated and compared. Quantitative measurements of angiogenic factors secreted from monocultures and cocultures of leukemic cells with bone marrow stromal fibroblasts suggest a synergistic relationship between ECs, leukemic cells, and bone marrow stromal fibroblasts for angiogenic induction, and also confirm the necessity of conducting functional angiogenic assays in proper 3D biomimetic cell culture systems like the one developed in this work.

Co-culture with podoplanin+ cells protects leukemic blast cells with leukemia-associated antigens in the tumor microenvironment

Podoplanin+ cells are indispensable in the tumor microenvironment. Increasing evidence suggests that podoplanin may support the growth and metastasis of solid tumors; however, to the best of our knowledge no studies have determined whether or not podoplanin serves a supportive role in acute myeloid leukemia (AML). The effects of co‑culture with podoplanin+ cells on the cellular activities of the leukemic cells, such as apoptosis and cell proliferation, in addition to the expression of podoplanin in leukemic cells, were investigated. Due to the fact that genetic abnormalities are the primary cause of leukemogenesis, the overexpression of the fibromyalgia‑like tyrosine kinase‑3 gene in colony forming units was also examined following cell sorting. Podoplanin+ cells were found to play a protective role against apoptosis in leukemic cells and to promote cell proliferation. Tumor‑associated antigens, including Wilms' tumor gene 1 and survivin, were increased when leukemic cells were co‑cultured with podoplanin+ cells. In combination, the present results also suggest that podoplanin+ cells can function as stromal cells for blast cell retention in the AML tumor microenvironment.

The safety of treatment options for elderly people with acute myeloid leukemia

INTRODUCTION

Life expectancy in elderly patients with acute myeloid leukemia (AML) is a function of age, disability, and co-morbidity, combined with leukemia characteristics. There is currently no consensus regarding the optimal therapeutic strategy for older adults with AML. Although selected older adults with AML can benefit from intensive therapies, recent evidence supports the use of lower-intensity therapies in most patients and emphasizes the importance of tolerability and quality of life.

AREAS COVERED

Results of the current clinical trials and safety data are reviewed.

EXPERT OPINION

Treatment recommendations for elderly patients with AML need to be individualized. In order to avoid toxicities, hematologists should collaborate more with geriatricians to identify clues of vulnerability in elderly patients through the study of functional physical, physiological, cognitive, social, and psychological parameters.

The progress of angiogenic factors in the development of leukemias

Angiogenic factors have been demonstrated to play important roles in modulating angiogenesis of solid tumors. Recently, accumulating studies extensively indicated that some angiogenic factors widely exist in malignant cells of hematologic malignancy, which regulated the expression of a number of genes that were involved in abnormal proliferation, differentiation and apoptosis of these cells. With deep research of angiogenic factors, its expression, function and regulatory mechanism were gradually elucidated, and some of them were related to the development and prognosis of leukemia, or provide more possible strategies for treatment of patients with leukemia. Herein, we summarize the progress in study of some important angiogenic factors and hematological malignancies.