Glucose transporter 1-mediated glucose uptake is limiting for B-cell acute lymphoblastic leukemia anabolic metabolism and resistance to apoptosis

Cell signaling in Ehrlichia infection and cancer: Parallels in pathogenesis

Ehrlichia chaffeensis (E. chaffeensis) has recently emerged as an intracellular bacterial pathogen with sophisticated survival mechanisms that include repurposing evolutionarily conserved eukaryotic cell signaling pathways for immune evasion. E. chaffeensis exploits four major developmental signaling pathways (Wnt, Notch, Hedgehog, and Hippo) using short linear motif (SLiM) ligand mimicry to initiate signaling cascades. Dysregulation of these major signaling pathways leading to unchecked cell survival is implicated in various diseases, most notably cancer. E. chaffeensis exploits Wnt, Notch, Hedgehog and Hippo signaling pathways to inhibit apoptosis and co-opt other cellular functions to promote infection. This review will explore the signaling pathways exploited during Ehrlichia infection and the new discoveries that have illuminated this interesting example of the cell signaling convergence in cellular infection and cancer biology.

Adipocyte maturation impacts daunorubicin disposition and metabolism

INTRODUCTION

Acute lymphoblastic leukaemia (ALL) is the most common type of childhood leukaemia with effective chemotherapeutic treatment. However, obesity has been associated with higher ALL chemoresistance rates and lower event-free survival rates. The molecular mechanism of how obesity promotes chemotherapy resistance is not well delineated.

OBJECTIVES

This study evaluated the effect of adipocyte maturation on sequestration and metabolism of chemotherapeutic drug daunorubicin (DNR).

METHODS

Using targeted LC-MS/MS multi-analyte assay, DNR sequestration and metabolism were studied in human preadipocyte and adipocyte cell lines, where expressions of DNR-metabolizing enzymes aldo-keto reductases (AKR) and carbonyl reductases (CBR) were also evaluated. In addition, to identify the most DNR-metabolizing AKR/CBR isoforms, recombinant human AKR and CBR enzymes were subject to DNR metabolism. The results were further validated by AKR-, CBR-specific inhibitors.

RESULTS

This report shows that adipocyte maturation upregulates expressions of AKR and CBR enzymes (by 4- to 60- folds, p < .05), which is positively associated with enhanced sequestration and metabolism of DNR in adipocytes compared to preadipocytes (by ~30%, p < .05). In particular, adipocyte maturation upregulates AKR1C3 and CBR1, which are the predominate metabolic enzyme isoforms responsible for DNR biotransformation to its metabolites.

CONCLUSION

Fat is an expandable tissue that can sequester and detoxify DNR when stimulated by obesity, likely through the upregulation of DNR-metabolizing enzymes AKR1C3 and CBR1. Our data partially explains why obese ALL patients may be more likely to become chemoresistant towards DNR, and provides evidence for potential clinical investigation targeting obesity to reduce DNR chemoresistance.

Ikaros sets the threshold for negative B-cell selection by regulation of the signaling strength of the AKT pathway

Inhibitory phosphatases, such as the inositol-5-phosphatase SHIP1 could potentially contribute to B-cell acute lymphoblastic leukemia (B-ALL) by raising the threshold for activation of the autoimmunity checkpoint, allowing malignant cells with strong oncogenic B-cell receptor signaling to escape negative selection. Here, we show that SHIP1 is differentially expressed across B-ALL subtypes and that high versus low SHIP1 expression is associated with specific B-ALL subgroups. In particular, we found high SHIP1 expression in both, Philadelphia chromosome (Ph)-positive and ETV6-RUNX1-rearranged B-ALL cells. As demonstrated by targeted knockdown of SHIP1 by RNA interference, proliferation of B-ALL cells in vitro and their tumorigenic spread in vivo depended in part on SHIP1 expression. We investigated the regulation of SHIP1, as an important antagonist of the AKT signaling pathway, by the B-cell-specific transcription factor Ikaros. Targeted restoration of Ikaros and pharmacological inhibition of the antagonistic casein kinase 2, led to a strong reduction in SHIP1 expression and at the same time to a significant inhibition of AKT activation and cell growth. Importantly, the tumor suppressive function of Ikaros was enhanced by a SHIP1-dependent additive effect. Furthermore, our study shows that all three AKT isoforms contribute to the pro-mitogenic and anti-apoptotic signaling in B-ALL cells. Conversely, hyperactivation of a single AKT isoform is sufficient to induce negative selection by increased oxidative stress. In summary, our study demonstrates the regulatory function of Ikaros on SHIP1 expression in B-ALL and highlights the relevance of sustained SHIP1 expression to prevent cells with hyperactivated PI3K/AKT/mTOR signaling from undergoing negative selection.

Lipid metabolism in B cell biology

In recent years, the field of immunometabolism has solidified its position as a prominent area of investigation within the realm of immunological research. An expanding body of scientific literature has unveiled the intricate interplay between energy homeostasis, signalling molecules, and metabolites in relation to fundamental aspects of our immune cells. It is now widely accepted that disruptions in metabolic equilibrium can give rise to a myriad of pathological conditions, ranging from autoimmune disorders to cancer. Emerging evidence, although sometimes fragmented and anecdotal, has highlighted the indispensable role of lipids in modulating the behaviour of immune cells, including B cells. In light of these findings, this review aims to provide a comprehensive overview of the current state of knowledge regarding lipid metabolism in the context of B cell biology.

Glucose metabolism in B cell malignancies: a focus on glycolysis branching pathways

Glucose catabolism, one of the essential pathways sustaining cellular bioenergetics, has been widely studied in the context of tumors. Nevertheless, the function of various branches of glucose metabolism that stem from 'classical' glycolysis have only been partially explored. This review focuses on discussing general mechanisms and pathological implications of glycolysis and its branching pathways in the biology of B cell malignancies. We summarize here what is known regarding pentose phosphate, hexosamine, serine biosynthesis, and glycogen synthesis pathways in this group of tumors. Despite most findings have been based on malignant B cells themselves, we also discuss the role of glucose metabolism in the tumor microenvironment, with a focus on T cells. Understanding the contribution of glycolysis branching pathways and how they are hijacked in B cell malignancies will help to dissect the role they have in sustaining the dissemination and proliferation of tumor B cells and regulating immune responses within these tumors. Ultimately, this should lead to deciphering associated vulnerabilities and improve current therapeutic schedules.

Obesity and Leukemia: Biological Mechanisms, Perspectives, and Challenges

PURPOSE OF REVIEW

To examine the epidemiological data on obesity and leukemia; evaluate the effect of obesity on leukemia outcomes in childhood acute lymphoblastic leukemia (ALL) survivors; assess the potential mechanisms through which obesity may increase the risk of leukemia; and provide the effects of obesity management on leukemia. Preventive (diet, physical exercise, obesity pharmacotherapy, bariatric surgery) measures, repurposing drugs, candidate therapeutic agents targeting oncogenic pathways of obesity and insulin resistance in leukemia as well as challenges of the COVID-19 pandemic are also discussed.

RECENT FINDINGS

Obesity has been implicated in the development of 13 cancers, such as breast, endometrial, colon, renal, esophageal cancers, and multiple myeloma. Leukemia is estimated to account for approximately 2.5% and 3.1% of all new cancer incidence and mortality, respectively, while it represents the most frequent cancer in children younger than 5 years. Current evidence indicates that obesity may have an impact on the risk of leukemia. Increased birthweight may be associated with the development of childhood leukemia. Obesity is also associated with worse outcomes and increased mortality in leukemic patients. However, there are several limitations and challenges in meta-analyses and epidemiological studies. In addition, weight gain may occur in a substantial number of childhood ALL survivors while the majority of studies have documented an increased risk of relapse and mortality among patients with childhood ALL and obesity. The main pathophysiological pathways linking obesity to leukemia include bone marrow adipose tissue; hormones such as insulin and the insulin-like growth factor system as well as sex hormones; pro-inflammatory cytokines, such as IL-6 and TNF-α; adipocytokines, such as adiponectin, leptin, resistin, and visfatin; dyslipidemia and lipid signaling; chronic low-grade inflammation and oxidative stress; and other emerging mechanisms. Obesity represents a risk factor for leukemia, being among the only known risk factors that could be prevented or modified through weight loss, healthy diet, and physical exercise. Pharmacological interventions, repurposing drugs used for cardiometabolic comorbidities, and bariatric surgery may be recommended for leukemia and obesity-related cancer prevention.

Anti-inflammatory effect of Piper longum L. fruit methanolic extract on lipopolysaccharide-treated RAW 264.7 murine macrophages

Context

The Piper species was studied several potential properties such as anti-tumor, anti-inflammatory and antioxidant activity. However, the specific anti-inflammatory activity of the extract from the fruits of P. longum L. has not been investigated.

Objectives

Our study want to examine the anti-inflammatory effects of P. longum L. fruit methanolic extracts (PLE) on lipopolysachharide (LPS)-stimulated RAW 264.7 murine macrophages to understand the mechanism of this effect.

Method

This study examined the chemical profiling of PLE by LC-HRMS analysis and measured the presence of nitric oxide (NO), interleukin-6 (IL-6) and tumor necrosis factor alpha (TNF-α) in the supernatant using the Griess reagent assay and enzyme-linked immunosorbent assay (ELISA), respectively. The mRNA expression of IL-6, TNF-α, cyclooxygenase-2 (COX-2), and inducible nitric oxide synthase (iNOS) were evaluated by using real-time quantitative polymerase chain reaction (RT-qPCR). Furthermore, the protein expression of COX-2, iNOS and the phosphorylation of MAPK family, c-Jun N-terminal kinase (JNK), p38 in protein level were observed by western blotting.

Result

PLE have detected 66 compounds which belong to different classes such as alkaloids, flavonoids, terpenoids, phenolics, lactones, and organic acids inhibited nitric oxide products with the IC50 = 28.5 ± 0.91 μg/mL. Moreover, PLE at 10-100 μg/mL up-regulate HO-1 protein expression from 3 to 10 folds at 3 h. It also downregulated the mRNA and protein expression of iNOS, COX-2, decreased IL-6 and TNF-α secretion by modulating the mitogen-activated protein kinase (MAPK) signaling pathway, specifically by decreasing the phosphorylation of p38 and JNK.

Conclusion

These results shown chemical profiling of PLE and demonstrated that PLE exhibits anti-inflammatory effects by regulating the MAPK family and could be a potential candidate for the treatment of inflammatory diseases.

Plasma Cell Differentiation, Antibody Quality, and Initial Germinal Center B Cell Population Depend on Glucose Influx Rate

Serum Ab concentrations, selection for higher affinity BCRs, and generation of higher Ab affinities are important elements of immune response optimization and functions of germinal center (GC) reactions. B cell proliferation requires nutrients to support the anabolism inherent in clonal expansion. Glucose usage by mouse GC B cells has been reported to contribute little to their energy needs, with questions raised as to whether glucose uptake or glycolysis increases in GC B cells compared with their naive precursors. Indeed, metabolism can be highly flexible, such that supply shortage along one pathway may be compensated by increased flux on others. We now show that reduction of the glucose transporter GLUT1 in mice after establishment of a preimmune B cell repertoire, even after initiation of the GC B cell gene expression program, decreased initial GC B cell population numbers, affinity maturation, and plasma cell outputs. Glucose oxidation was heightened in GC B cells, but this hexose flowed more into the pentose phosphate pathway, whose activity was important in controlling reactive oxygen species (ROS) and Ab-secreting cell production. In modeling how glucose usage by B cells promotes the Ab response, the control of ROS appeared insufficient. Surprisingly, the combination of galactose, which mitigated ROS, with provision of mannose, an efficient precursor to glycosylation, supported robust production of and normal Ab secretion by Ab-secreting cells under glucose-free conditions. Collectively, the findings indicate that GCs depend on normal glucose influx, especially in plasma cell production, but reveal an unexpected metabolic flexibility in hexose requirements.

Ehrlichia Wnt SLiM ligand mimic deactivates the Hippo pathway to engage the anti-apoptotic Yap-GLUT1-BCL-xL axis

Ehrlichia chaffeensis TRP120 effector has evolved short linear motif (SLiM) ligand mimicry to repurpose multiple evolutionarily conserved cellular signaling pathways, including Wnt, Notch, and Hedgehog. In this investigation, we demonstrate that E. chaffeensis and recombinant TRP120 deactivate Hippo signaling, resulting in the activation of Hippo transcription coactivator Yes-associated protein (Yap). Moreover, a homologous 6 amino acid (QDVASH) SLiM shared by TRP120 and Wnt3a/5a ligands phenocopied Yap and β-catenin activation induced by E. chaffeensis, rTRP120, and Wnt5a. Similar Hippo gene expression profiles were also stimulated by E. chaffeensis, rTRP120, SLiM, and Wnt5a. Single siRNA knockdown of Hippo transcription co-activator/factors, Yap, and transcriptional enhanced associate domain (TEAD) significantly decreased E. chaffeensis infection. Yap activation was abolished in THP-1 Wnt Frizzled-5 (Fzd5) receptor knockout cells (KO), demonstrating Fzd5 receptor dependence. In addition, the TRP120-Wnt-SLiM antibody blocked Hippo deactivation (Yap activation). Expression of anti-apoptotic Hippo target gene SLC2A1 (encodes glucose transporter 1; GLUT1) was upregulated by E. chaffeensis and corresponded to increased levels of GLUT1. Conversely, siRNA knockdown of SLC2A1 significantly inhibited infection. Higher GLUT1 levels correlated with increased B cell lymphoma-extra large (BCL-xL) and decreased BCL2-associated X, apoptosis regulator (Bax) levels. Moreover, blocking Yap activation with the inhibitor Verteporfin induced apoptosis that corresponded to significant reductions in GLUT1 and BCL-xL levels and activation of Bax and Caspase-3 and -9. This study identifies a novel shared Wnt/Hippo SLiM ligand mimic and demonstrates that E. chaffeensis deactivates the Hippo pathway to engage the anti-apoptotic Yap-GLUT1-BCL-xL axis.

Enhanced chemotherapeutic efficacy of docetaxel in human lung cancer cell line via GLUT1 inhibitor

The dose-dependent adverse effects of anticancer agents need new methods with lesser toxicity. The objective of the current research was to evaluate the efficacy of GLUT1 inhibitor, as an inhibitor of glucose consumption in cancer cells, in augmenting the efficiency of docetaxel with respect to cytotoxicity and apoptosis. Cell cytotoxicity was assessed by using methylthiazolyldiphenyl-tetrazolium bromide (MTT) assay. Annexin V/PI double staining was employed to evaluate apoptosis percentage. Quantitative real-time polymerase chain reaction (RT-PCR) analysis was accomplished to detect the expression of genes involved in the apoptosis pathway. The IC50 values for docetaxel and BAY-876 were 3.7 ± 0.81 and 34.1 ± 3.4 nM, respectively. The severity of synergistic mutual effects of these agents on each other was calculated by synergy finder application. It showed that the percentage of apoptotic cells following co-administration of docetaxel and BAY-876 increased to 48.1 ± 2.8%. In comparison without GLUT1 co-administration, the combined therapy decreased significantly the transcriptome levels of the Bcl-2 and Ki-67 and a remarkable increase in the level of the Bax as proapoptotic protein(p < 0.05). Co-treatment of BAY-876 and docetaxel depicted a synergistic effect which was calculated using the synergy finder highest single agent (HSA) method (HSA synergy score: 28.055). These findings recommend that the combination of GLUT-1 inhibitor and docetaxel can be considered as a promising therapeutic approach for the treatment of patients with lung cancer.

Ehrlichia Wnt short linear motif ligand mimetic deactivates the Hippo pathway to engage the anti-apoptotic Yap-GLUT1-BCL-xL axis

Ehrlichia chaffeensis TRP120 effector has evolved short linear motif (SLiM) ligand mimicry to repurpose multiple evolutionarily conserved cellular signaling pathways including Wnt, Notch and Hedgehog. In this investigation, we demonstrate that E. chaffeensis and recombinant TRP120 deactivate Hippo signaling resulting in activation of Hippo transcription coactivator Yap and target gene expression. Moreover, a homologous 6 amino acid (QDVASH) SLiM shared by TRP120 and Wnt3a/5a ligands phenocopied Yap and β-catenin activation induced by E. chaffeensis, rTRP120 and Wnt5a. Similar Hippo gene expression profiles were also stimulated by E. chaffeensis, rTRP120, SLiM and Wnt5a. Single siRNA knockdown of Hippo transcription co-activator/factors (Yap and TEAD) significantly decreased E. chaffeensis infection. Yap activation was abolished in THP-1 Wnt Frizzled-5 (Fzd5) receptor knockout cells (KO), demonstrating Fzd5 receptor dependence. In addition, TRP120 Wnt-SLiM antibody blocked Hippo deactivation (Yap activation). Expression of anti-apoptotic Hippo target gene SLC2A1 (encodes glucose transporter 1; GLUT1) was upregulated by E. chaffeensis and corresponded to increased levels of GLUT1. Conversely, siRNA knockdown of SLC2A1 significantly inhibited infection. Higher GLUT1 levels correlated with increased BCL-xL and decreased Bax levels. Moreover, blocking Yap activation with the inhibitor Verteporfin induced apoptosis that corresponded to significant reductions in levels of GLUT1 and BCL-xL, and activation of Bax and Caspase-3 and -9. This study identifies a novel shared Wnt/Hippo SLiM ligand mimetic and demonstrates that E. chaffeensis deactivates the Hippo pathway to engage the anti-apoptotic Yap-GLUT1-BCL-xL axis.

TRAF3: A novel regulator of mitochondrial physiology and metabolic pathways in B lymphocytes

Mitochondria, the organelle critical for cell survival and metabolism, are exploited by cancer cells and provide an important therapeutic target in cancers. Mitochondria dynamically undergo fission and fusion to maintain their diverse functions. Proteins controlling mitochondrial fission and fusion have been recognized as essential regulators of mitochondrial functions, mitochondrial quality control, and cell survival. In a recent proteomic study, we identified the key mitochondrial fission factor, MFF, as a new interacting protein of TRAF3, a known tumor suppressor of multiple myeloma and other B cell malignancies. This interaction recruits the majority of cytoplasmic TRAF3 to mitochondria, allowing TRAF3 to regulate mitochondrial morphology, mitochondrial functions, and mitochondria-dependent apoptosis in resting B lymphocytes. Interestingly, recent transcriptomic, metabolic and lipidomic studies have revealed that TRAF3 also vitally regulates multiple metabolic pathways in B cells, including phospholipid metabolism, glucose metabolism, and ribonucleotide metabolism. Thus, TRAF3 emerges as a novel regulator of mitochondrial physiology and metabolic pathways in B lymphocytes and B cell malignancies. Here we review current knowledge in this area and discuss relevant clinical implications.

Multiple functions and regulatory network of miR-150 in B lymphocyte-related diseases

MicroRNAs (miRNAs) play vital roles in the post-transcriptional regulation of gene expression. Previous studies have shown that miR-150 is a crucial regulator of B cell proliferation, differentiation, metabolism, and apoptosis. miR-150 regulates the immune homeostasis during the development of obesity and is aberrantly expressed in multiple B-cell-related malignant tumors. Additionally, the altered expression of MIR-150 is a diagnostic biomarker of various autoimmune diseases. Furthermore, exosome-derived miR-150 is considered as prognostic tool in B cell lymphoma, autoimmune diseases and immune-mediated disorders, suggesting miR-150 plays a vital role in disease onset and progression. In this review, we summarized the miR-150-dependent regulation of B cell function in B cell-related immune diseases.

The opportunities and challenges for nutritional intervention in childhood cancers

Diet dictates nutrient availability in the tumor microenvironment, thus affecting tumor metabolic activity and growth. Intrinsically, tumors develop unique metabolic features and are sensitive to environmental nutrient concentrations. Tumor-driven nutrient dependencies provide opportunities to control tumor growth by nutritional restriction or supplementation. This review summarized the existing data on nutrition and pediatric cancers after systematically searching articles up to 2023 from four databases (PubMed, Web of Science, Scopus, and Ovid MEDLINE). Epidemiological studies linked malnutrition with advanced disease stages and poor clinical outcomes in pediatric cancer patients. Experimental studies identified several nutrient dependencies (i.e., amino acids, lipids, vitamins, etc.) in major pediatric cancer types. Dietary modifications such as calorie restriction, ketogenic diet, and nutrient restriction/supplementation supported pediatric cancer treatment, but studies remain limited. Future research should expand epidemiological studies through data sharing and multi-institutional collaborations and continue to discover critical and novel nutrient dependencies to find optimal nutritional approaches for pediatric cancer patients.

SIRT1 regulated hexokinase-2 promoting glycolysis is involved in hydroquinone-enhanced malignant progression in human lymphoblastoid TK6 cells

Reprogramming of cellular metabolism is a vital event during tumorigenesis. The role of glycolysis in malignant progression promoted by hydroquinone (HQ), one of the metabolic products of benzene, remains to be understood. Recently, we reported the overexpression of sirtuin 1 (SIRT1) in HQ-enhanced malignant progression of TK6 cells and hypothesized that SIRT1 might contribute to glycolysis and favor tumorigenesis. Our data showed that acute exposure of TK6 cells to HQ for 48 h inhibited glycolysis, as indicated by reduction in glucose consumption, lactate production, hexokinase activity, and the expression of SIRT1 and glycolytic enzymes, including HIF-1α, hexokinase-2 (HK-2), ENO-1, glucose transporter 1 (Glut-1), and lactic dehydrogenase A (LDHA). Knockdown of SIRT1 or inhibition of glycolysis using the glycolytic inhibitor 2-deoxy-D-glucose (2-DG) downregulated the levels of SIRT1 and glycolytic enzymes and significantly enhanced HQ-induced cell apoptosis, although knockdown of SIRT1 or 2-DG alone had little effect on apoptosis. Furthermore, immunofluorescence and Co-IP assays demonstrated that SIRT1 regulated the expression of HK-2, and HQ treatment caused a decrease in SIRT1 and HK-2 binding to mitochondria. Importantly, we found that glycolysis was promoted with increasing HQ treatment weeks. Long-term HQ exposure increased the expression of SIRT1 and several glycolytic enzymes and promoted malignant cell progression. Moreover, compared with the PBS group, glucose consumption and lactate production increased after 10 weeks of HQ exposure, and the protein levels of SIRT1 and HK-2 were increased after 15 weeks of HQ exposure, while those of Glut-1, ENO-1, and LDHA were elevated. In addition, SIRT1 knockdown HQ 19 cells exhibited decreased lactate production, glucose consumption, glycolytic enzymes expression, cell growth, and tumor formation in nude mice. Our findings identify the high expression of SIRT1 as a strong oncogenic driver that positively regulates HK-2 and promotes glycolysis in HQ-accelerated malignant progression of TK6 cells.

Regulation of immune cell metabolism in health and disease: Special focus on T and B cell subsets

Metabolism is a dynamic process and keeps changing from time to time according to the demand of a particular cell to meet its bio-energetic requirement. Different immune cells rely on distinct metabolic programs which allow the cell to balance its requirements for energy, molecular biosynthesis, and effector activity. In the aspect of infection and cancer immunology, effector T and B cells get exhausted and help tumor cells to evade immunosurveillance. On the other hand, T cells become hyperresponsive in the scenario of autoimmune diseases. In this article, we have explored the uniqueness and distinct metabolic features of key CD4⁺ T and B helper cell subsets, CD4⁺ T, B regulatory cell subsets and CD8⁺ T cells regarding health and disease. Th1 cells rely on glycolysis and glutaminolysis; inhibition of these metabolic pathways promotes Th1 cells in Treg population. However, Th2 cells are also dependent on glycolysis but an abundance of lactate within TME shifts their metabolic dependency to fatty acid metabolism. Th17 cells depend on HIF-1α mediated glycolysis, ablation of HIF-1α reduces Th17 cells but enhance Treg population. In contrast to effector T cells which are largely dependent on glycolysis for their differentiation and function, Treg cells mainly rely on FAO for their function. Therefore, it is of utmost importance to understand the metabolic fates of immune cells and how it facilitates their differentiation and function for different disease models. Targeting metabolic pathways to restore the functionality of immune cells in diseased conditions can lead to potent therapeutic measures.

Single-Cell Metabolomics in Hematopoiesis and Hematological Malignancies

Aberrant metabolism contributes to tumor initiation, progression, metastasis, and drug resistance. Metabolic dysregulation has emerged as a hallmark of several hematologic malignancies. Decoding the molecular mechanism underlying metabolic rewiring in hematological malignancies would provide promising avenues for novel therapeutic interventions. Single-cell metabolic analysis can directly offer a meaningful readout of the cellular phenotype, allowing us to comprehensively dissect cellular states and access biological information unobtainable from bulk analysis. In this review, we first highlight the unique metabolic properties of hematologic malignancies and underscore potential metabolic vulnerabilities. We then emphasize the emerging single-cell metabolomics techniques, aiming to provide a guide to interrogating metabolism at single-cell resolution. Furthermore, we summarize recent studies demonstrating the power of single-cell metabolomics to uncover the roles of metabolic rewiring in tumor biology, cellular heterogeneity, immunometabolism, and therapeutic resistance. Meanwhile, we describe a practical view of the potential applications of single-cell metabolomics in hematopoiesis and hematological malignancies. Finally, we present the challenges and perspectives of single-cell metabolomics development.

Deciphering Metabolic Adaptability of Leukemic Stem Cells

Therapeutic targeting of leukemic stem cells is widely studied to control leukemia. An emerging approach gaining popularity is altering metabolism as a potential therapeutic opportunity. Studies have been carried out on hematopoietic and leukemic stem cells to identify vulnerable pathways without impacting the non-transformed, healthy counterparts. While many metabolic studies have been conducted using stem cells, most have been carried out in vitro or on a larger population of progenitor cells due to challenges imposed by the low frequency of stem cells found in vivo. This creates artifacts in the studies carried out, making it difficult to interpret and correlate the findings to stem cells directly. This review discusses the metabolic difference seen between hematopoietic stem cells and leukemic stem cells across different leukemic models. Moreover, we also shed light on the advancements of metabolic techniques and current limitations and areas for additional research of the field to study stem cell metabolism.

Pitavastatin Is Anti-Leukemic in a Bone Marrow Microenvironment Model of B-Lineage Acute Lymphoblastic Leukemia

Simple Summary

Chemoresistance after chemotherapy is a negative prognostic indicator for B-cell acute lymphoblastic leukemia (ALL), necessitating the search for novel therapies. By growing ALL cells together with bone marrow stromal cells, we developed a chemoresistant ALL model. Using this model, we found that the lipid lowering drug pitavastatin had antileukemic activity in this chemoresistant co-culture model. Our data suggests that pitavastatin may be a novel treatment option for repurposing in chemoresistant, relapse ALL.

Abstract

The lack of complete therapeutic success in the treatment of B-cell acute lymphoblastic leukemia (ALL) has been attributed, in part, to a subset of cells within the bone marrow microenvironment that are drug resistant. Recently, the cholesterol synthesis inhibitor, pitavastatin (PIT), was shown to be active in acute myeloid leukemia, prompting us to evaluate it in our in vitro co-culture model, which supports a chemo-resistant ALL population. We used phospho-protein profiling to evaluate the use of lipid metabolic active compounds in these chemo-resistant cells, due to the up-regulation of multiple active survival signals. In a co-culture with stromal cells, a shift towards anabolic processes occurred, which was further confirmed by assays showing increased lipid content. The treatment of REH leukemia cells with pitavastatin in the co-culture model resulted in significantly higher leukemic cell death than exposure to the standard-of-care chemotherapeutic agent, cytarabine (Ara-C). Our data demonstrates the use of pitavastatin as a possible alternative treatment strategy to improve patient outcomes in chemo-resistant, relapsed ALL.

GLUT1 Immunohistochemistry Is a Highly Sensitive and Relatively Specific Marker for Erythroid Lineage in Benign and Malignant Hematopoietic Tissues

OBJECTIVES

Glucose transporter 1 (GLUT1), a glucose transporter, is an abundant protein in erythrocytes with expression beginning early in erythropoiesis. We sought to evaluate the utility of GLUT1 immunohistochemistry (IHC) as a diagnostic marker for identifying erythroid differentiation in hematopoietic tissues, including neoplastic erythroid proliferations.

METHODS

A variety of benign and neoplastic bone marrow biopsy specimens containing variable proportions of erythroid precursors were selected (n = 46, including 36 cases of leukemia). GLUT1 IHC was performed using a commercially available polyclonal antibody. Each case was evaluated for staining of erythroid precursors, nonerythroid hematopoietic cells, and blasts. A GATA1/GLUT1 double stain was performed on one case to confirm coexpression of GLUT1 on early erythroid precursors. Staining was compared with other erythroid markers, including glycophorin C.

RESULTS

GLUT1 demonstrated strong membranous staining in erythroid precursors of all cases, which was restricted largely to the erythroid lineage. Of the 36 leukemia cases, all 6 cases of pure erythroid leukemia and both cases of therapy-related acute myeloid leukemia with erythroid differentiation showed positive GLUT1 staining in blasts. Otherwise, only lymphoblasts in B-lymphoblastic leukemia showed weak to moderate granular cytoplasmic staining (four of five cases).

CONCLUSIONS

GLUT1 IHC is a highly sensitive and relatively specific marker for erythroid lineage in benign and neoplastic bone marrow biopsy specimens.

Metabolic Reprogramming and Cell Adhesion in Acute Leukemia Adaptation to the CNS Niche

Involvement of the Central Nervous System (CNS) in acute leukemia confers poor prognosis and lower overall survival. Existing CNS-directed therapies are associated with a significant risk of short- or long-term toxicities. Leukemic cells can metabolically adapt and survive in the microenvironment of the CNS. The supporting role of the CNS microenvironment in leukemia progression and dissemination has not received sufficient attention. Understanding the mechanism by which leukemic cells survive in the nutrient-poor and oxygen-deprived CNS microenvironment will lead to the development of more specific and less toxic therapies. Here, we review the current literature regarding the roles of metabolic reprogramming in leukemic cell adhesion and survival in the CNS.

PON2 blockade overcomes dexamethasone resistance in acute lymphoblastic leukemia

OBJECTIVES

The high frequency of chemotherapy resistance is ultimately responsible for clinical relapse in acute lymphoblastic leukemia (ALL). Nevertheless, the molecular mechanism relevant to glucocorticoid (GC) resistance remains ambiguous.

METHODS

Quantitative real-time polymerase chain reaction and Western blot were performed to detect the expressions of paraoxonase 2 (PON2), Bcl-2 and Bax. shRNA was used to knockdown PON2 expression in SUP-B15 and REH cell. CCK-8 and flow cytometry assay were conducted to monitor the changes of proliferation and apoptosis in ALL cells. The growth of ALL REH cells in vivo was determined using transplanted tumor model.

RESULTS

This study was designed to identify GC resistance-associated genes by means of the transcriptome chip from the public Gene Expression Omnibus database, and preliminarily investigation of dexamethasone (DEX)-resistance mechanism in ALL. We disclosed that PON2 expression was elevated in ALL patients and especially higher in DEX-resistance ALL patients. Then, cell apoptosis assay suggested that silencing of PON2 dramatically promoted in DEX-resistant ALL cells apoptosis and the activity of Caspase 3 induced by DEX administration. In xenograft tumor model, PON2 knockdown significantly reduced DEX-resistant ALL cells growth in immunodeficient mice.

CONCLUSIONS

Collectively, inhibition of PON2 may represent a novel method to restore the sensitivity of treatment-resistant ALL to GC-induced cell death.

The Importance of Cellular Metabolic Pathways in Pathogenesis and Selective Treatments of Hematological Malignancies

Despite recent advancements in the treatment of hematologic malignancies and the emergence of newer and more sophisticated therapeutic approaches such as immunotherapy, long-term overall survival remains unsatisfactory. Metabolic alteration, as an important hallmark of cancer cells, not only contributes to the malignant transformation of cells, but also promotes tumor progression and metastasis. As an immune-escape mechanism, the metabolic adaptation of the bone marrow microenvironment and leukemic cells is a major player in the suppression of anti-leukemia immune responses. Therefore, metabolic rewiring in leukemia would provide promising opportunities for newer therapeutic interventions. Several therapeutic agents which affect essential bioenergetic pathways in cancer cells including glycolysis, β-oxidation of fatty acids and Krebs cycle, or anabolic pathways such as lipid biosynthesis and pentose phosphate pathway, are being tested in various types of cancers. So far, numerous preclinical or clinical trial studies using such metabolic agents alone or in combination with other remedies such as immunotherapy are in progress and have demonstrated promising outcomes. In this review, we aim to argue the importance of metabolic alterations and bioenergetic pathways in different types of leukemia and their vital roles in disease development. Designing treatments based on targeting leukemic cells vulnerabilities, particularly in nonresponsive leukemia patients, should be warranted.

Supply and demand: Cellular nutrient uptake and exchange in cancer

Nutrient supply and demand delineate cell behavior in health and disease. Mammalian cells have developed multiple strategies to secure the necessary nutrients that fuel their metabolic needs. This is more evident upon disruption of homeostasis in conditions such as cancer, when cells display high proliferation rates in energetically challenging conditions where nutritional sources may be scarce. Here, we summarize the main routes of nutrient acquisition that fuel mammalian cells and their implications in tumorigenesis. We argue that the molecular mechanisms of nutrient acquisition not only tip the balance between nutrient supply and demand but also determine cell behavior upon nutrient limitation and energetic stress and contribute to nutrient partitioning and metabolic coordination between different cell types in inflamed or tumorigenic environments.

PON2 subverts metabolic gatekeeper functions in B cells to promote leukemogenesis

Unlike other cell types, developing B cells undergo multiple rounds of somatic recombination and hypermutation to evolve high-affinity antibodies. Reflecting the high frequency of DNA double-strand breaks, adaptive immune protection by B cells comes with an increased risk of malignant transformation. B lymphoid transcription factors (e.g., IKZF1 and PAX5) serve as metabolic gatekeepers by limiting glucose to levels insufficient to fuel transformation. We here identified aberrant expression of the lactonase PON2 in B cell acute lymphoblastic leukemia (B-ALL) as a mechanism to bypass metabolic gatekeeper functions. Compared to normal pre-B cells, PON2 expression was elevated in patient-derived B-ALL samples and correlated with poor clinical outcomes in pediatric and adult cohorts. Genetic deletion of Pon2 had no measurable impact on normal B cell development. However, in mouse models for BCR-ABL1 and NRAS^G12D-driven B-ALL, deletion of Pon2 compromised proliferation, colony formation, and leukemia initiation in transplant recipient mice. Compromised leukemogenesis resulted from defective glucose uptake and adenosine triphosphate (ATP) production in PON2-deficient murine and human B-ALL cells. Mechanistically, PON2 enabled glucose uptake by releasing the glucose-transporter GLUT1 from its inhibitor stomatin (STOM) and genetic deletion of STOM largely rescued PON2 deficiency. While not required for glucose transport, the PON2 lactonase moiety hydrolyzes the lactone-prodrug 3OC12 to form a cytotoxic intermediate. Mirroring PON2 expression levels in B-ALL, 3OC12 selectively killed patient-derived B-ALL cells but was well tolerated in transplant recipient mice. Hence, while B-ALL cells critically depend on aberrant PON2 expression to evade metabolic gatekeeper functions, PON2 lactonase activity can be leveraged as synthetic lethality to overcome drug resistance in refractory B-ALL.

Metabolic determinants of B-cell selection

B-cells are antibody-producing cells of the adaptive immune system. Approximately 75% of all newly generated B-cells in the bone marrow are autoreactive and express potentially harmful autoantibodies. To prevent autoimmune disease, the immune system has evolved a powerful mechanism to eliminate autoreactive B-cells, termed negative B-cell selection. While designed to remove autoreactive clones during early B-cell development, our laboratory recently discovered that transformed B-cells in leukemia and lymphoma are also subject to negative selection. Indeed, besides the risk of developing autoimmune disease, B-cells are inherently prone to malignant transformation: to produce high-affinity antibodies, B-cells undergo multiple rounds of somatic immunoglobulin gene recombination and hypermutation. Reflecting high frequencies of DNA-breaks, adaptive immune protection by B-cells comes with a dramatically increased risk of development of leukemia and lymphoma. Of note, B-cells exist under conditions of chronic restriction of energy metabolism. Here we discuss how these metabolic gatekeeper functions during B-cell development provide a common mechanism for the removal of autoreactive and premalignant B-cells to safeguard against both autoimmune diseases and B-cell malignancies.

Metabolic Gatekeepers of Pathological B Cell Activation

Unlike other cell types, B cells undergo multiple rounds of V(D)J recombination and hypermutation to evolve high-affinity antibodies. Reflecting high frequencies of DNA double-strand breaks, adaptive immune protection by B cells comes with an increased risk of malignant transformation. In addition, the vast majority of newly generated B cells express an autoreactive B cell receptor (BCR). Thus, B cells are under intense selective pressure to remove autoreactive and premalignant clones. Despite stringent negative selection, B cells frequently give rise to autoimmune disease and B cell malignancies. In this review, we discuss mechanisms that we term metabolic gatekeepers to eliminate pathogenic B cell clones on the basis of energy depletion. Chronic activation signals from autoreactive BCRs or transforming oncogenes increase energy demands in autoreactive and premalignant B cells. Thus, metabolic gatekeepers limit energy supply to levels that are insufficient to fuel either a transforming oncogene or hyperactive signaling from an autoreactive BCR.

Selenium nanoparticles reduce glucose metabolism and promote apoptosis of glioma cells through reactive oxygen species-dependent manner

Gliomas are the most common, malignant, and lethal tumors in adults. Furthermore, gliomas are highly resistant to current chemotherapeutic drugs. Thus, new effective anticancer drugs for glioma are urgently needed. Selenium nanoparticles have been reported to have potent anti-tumor activity, although the specific mechanism is not fully understood. This study aimed to test the anti-tumor effect of selenium nanoparticles and its mechanism. We used selenium nanoparticles to treat commercial glioma cell lines, and patient-derived glioma cells, and then used the MTT assay to determine selenium nanoparticles effect against these. Apoptotic cell death was determined by annexin V-Fluos staining kit. Glucose uptake, lactate, and adenosine triphosphate production, together with hexokinase 2 and pyruvate kinase activities were measured to determine the glucose metabolism level. Reactive oxygen species production was tested using 2',7'-dichlorodihydrofluorescein diacetate. Our results showed that selenium nanoparticles had a potent cytotoxic effect in glioma cells, regardless of whether they were drug-resistant or not, whereas it showed less toxic effect in normal healthy cells. Further tests showed that selenium nanoparticles treatment leads to apoptotic cell death enhancement and glucose metabolism reduction, and this process was in a reactive oxygen species pathway-dependent manner. These results may provide a novel direction for glioma therapy in the future.

Is There A Causal Relationship between Childhood Obesity and Acute Lymphoblastic Leukemia? A Review

Childhood obesity is a growing epidemic with numerous global health implications. Over the past few years, novel insights have emerged about the contribution of adult obesity to cancer risk, but the evidence base is far more limited in children. While pediatric patients with acute lymphoblastic leukemia (ALL) are at risk of obesity, it is unclear if there are potential causal mechanisms by which obesity leads to ALL development. This review explores the endocrine, metabolic and immune dysregulation triggered by obesity and its potential role in pediatric ALL's genesis. We describe possible mechanisms, including adipose tissue attraction and protection of lymphoblasts, and their impact on ALL chemotherapies' pharmacokinetics. We also explore the potential contribution of cytokines, growth factors, natural killer cells and adipose stem cells to ALL initiation and propagation. While there are no current definite causal links between obesity and ALL, critical questions persist as to whether the adipose tissue microenvironment and endocrine actions can play a causal role in childhood ALL, and there is a need for more research to address these questions.

Mechanisms by Which Obesity Impacts Survival from Acute Lymphoblastic Leukemia

The prevalence of obesity has steadily risen over the past decades, even doubling in more than 70 countries. High levels of body fat (adiposity) and obesity are associated with endocrine and hormonal dysregulation, cardiovascular compromise, hepatic dysfunction, pancreatitis, changes in drug metabolism and clearance, inflammation, and metabolic stress. It is thus unsurprising that obesity can affect the development of and survival from a wide variety of malignancies. This review focuses on acute lymphoblastic leukemia, the most common malignancy in children, to explore the multiple mechanisms connecting acute lymphoblastic leukemia, obesity, and adipocytes, and the implications for leukemia therapy.

Nicotinamide Inhibits Glycolysis of HL-60 Cells by Modulating Sirtuin 1 (SIRT1)/Peroxisome Proliferator-Activated Receptor γ Coactivator 1α (PGC-1α)/Hypoxia-Inducible Factor-2α (HIF2α) Signaling Pathway

Background

Nicotinamide can affect differentiation and proliferation of leukemia cells. This research aimed to explore the regulatory effect of nicotinamide on glycolysis metabolism of leukemia cells and to clarify the associated mechanisms.

Material/Methods

HL-60 cells were treated with nicotinamide and divided into 0.1, 1, and 10 μmol/l groups. HL-60 cells without any administration were assigned as negative control (CT group). Glucolytic activity was evaluated by detecting lactic acid production, and glucose level was measured using glucose consumption assay. Apoptosis of HL-60 was examined using flow cytometry assay, when cells were cultured for 24 h. Expressions of sirtuin 1 (SIRT1), peroxisome proliferator-activated receptor γ coactivator 1α (PGC-1α), and hypoxia-inducible factor-2α (HIF2α) were evaluated using a reverse transcription PCR assay and Western blotting assay, respectively.

Results

Nicotinamide remarkably decreased lactic acid production and glucose levels in leukemia cells compared with that of the CT group (p<0.05). Nicotinamide significantly induced the apoptosis of HL-60 cells compared to that of the negative control group (p<0.05). Nicotinamide significantly inhibited the SIRT1/PGC-1α/HIF2α signaling pathway mRNAs compared to that of the CT group (p<0.05). Nicotinamide remarkably reduced mitochondrial regulatory factors SIRT1/PGC-1α expression compared to that in the CT group (p<0.05). Nicotinamide obviously downregulated HIF2α compared with that of the CT group (p<0.05). Moreover, all of the above nicotinamide-induced effects, including glycolytic activity, apoptosis, and expression of SIRT1/PGC-1α/HIF2α, were changed in a dose-dependent manner.

Conclusions

Nicotinamide can inhibit glycolysis of HL-60 cells by inhibiting the mitochondrial regulatory factor SIRT1/PGC-1α and suppressing transcription factor HIF2α.

mTOR Regulation of Metabolism in Hematologic Malignancies

Neoplastic cells rewire their metabolism, acquiring a selective advantage over normal cells and a protection from therapeutic agents. The mammalian Target of Rapamycin (mTOR) is a serine/threonine kinase involved in a variety of cellular activities, including the control of metabolic processes. mTOR is hyperactivated in a large number of tumor types, and among them, in many hematologic malignancies. In this article, we summarized the evidence from the literature that describes a central role for mTOR in the acquisition of new metabolic phenotypes for different hematologic malignancies, in concert with other metabolic modulators (AMPK, HIF1α) and microenvironmental stimuli, and shows how these features can be targeted for therapeutic purposes.

Metabolic dependencies and vulnerabilities in leukemia

In this Review, Rashkovan et al. discuss the role of cancer metabolic circuitries feeding anabolism and redox potential in leukemia development and recent progress in translating these important findings to the clinic.

Leukemia cell proliferation requires up-regulation and rewiring of metabolic pathways to feed anabolic cell growth. Oncogenic drivers directly and indirectly regulate metabolic pathways, and aberrant metabolism is central not only for leukemia proliferation and survival, but also mediates oncogene addiction with significant implications for the development of targeted therapies. This review explores leukemia metabolic circuitries feeding anabolism, redox potential, and energy required for tumor propagation with an emphasis on emerging therapeutic opportunities.

The Metabolic Profiles in Hematological Malignancies

Leukemia is one of the most aggressive hematological malignancies. Leukemia stem cells account for the poor prognosis and relapse of the disease. Decades of investigations have been performed to figure out how to eradicate the leukemia stem cells. It has also been known that cancer cells especially solid cancer cells use energy differently than most of the cell types. The same thing happens to leukemia. Since there are metabolic differences between the hematopoietic stem cells and their immediate descendants, we aim at manipulating the energy sources with which that could have an effect on leukemia stem cells while sparing the normal blood cells. In this review we summarize the metabolic characteristics of distinct leukemias such as acute myeloid leukemia, chronic myeloid leukemia, T cell lymphoblastic leukemia, B-cell lymphoblastic leukemia, chronic lymphocytic leukemia and other leukemia associated hematological malignancies such as multiple myeloma and myelodysplastic syndrome. A better understanding of the metabolic profiles in distinct leukemias might provide novel perspectives and shed light on novel metabolic targeting strategies towards the clinical treatment of leukemias.

Targeting Metabolic Reprogramming in Acute Myeloid Leukemia

The cancer metabolic reprogramming allows the maintenance of tumor proliferation, expansion and survival by altering key bioenergetics, biosynthetic and redox functions to meet the higher demands of tumor cells. In addition, several metabolites are also needed to perform signaling functions that further promote tumor growth and progression. These metabolic alterations have been exploited in different cancers, including acute myeloid leukemia, as novel therapeutic strategies both in preclinical models and clinical trials. Here, we review the complexity of acute myeloid leukemia (AML) metabolism and discuss how therapies targeting different aspects of cellular metabolism have demonstrated efficacy and how they provide a therapeutic window that should be explored to target the metabolic requirements of AML cells.

Non-proteolytic ubiquitination of Hexokinase 2 by HectH9 controls tumor metabolism and cancer stem cell expansion

Enormous efforts have been made to target metabolic dependencies of cancer cells for developing new therapies. However, the therapeutic efficacy of glycolysis inhibitors is limited due to their inability to elicit cell death. Hexokinase 2 (HK2), via its mitochondrial localization, functions as a central nexus integrating glycolysis activation and apoptosis resilience. Here we identify that K63-linked ubiquitination by HectH9 regulates the mitochondrial localization and function of HK2. Through stable isotope tracer approach and functional metabolic analyses, we show that HectH9 deficiency impedes tumor glucose metabolism and growth by HK2 inhibition. The HectH9/HK2 pathway regulates cancer stem cell (CSC) expansion and CSC-associated chemoresistance. Histological analyses show that HectH9 expression is upregulated and correlated with disease progression in prostate cancer. This work uncovers that HectH9 is a novel regulator of HK2 and cancer metabolism. Targeting HectH9 represents an effective strategy to achieve long-term tumor remission by concomitantly disrupting glycolysis and inducing apoptosis.

TO901317 inhibits the development of hepatocellular carcinoma by LXRα/Glut1 decreasing glycometabolism

This study was conducted to observe the effect and possible mechanism of TO901317 in vivo and in vitro to provide a new basis for the targeted therapy of hepatocellular carcinoma (HCC). The expressions of liver X receptor (LXR)-α, glucose transporter (Glut)-1, proliferating cell nuclear antigen (PCNA), and matrix metalloproteinase (MMP)-9 were analyzed from HCC public database (NCBI PubMed database). The result showed that LXRα was downregulated, whereas Glut1, PCNA, and MMP9 were upregulated in human HCC compared with normal liver. Furthermore, LXRα mRNA was negatively correlated with Glut1 mRNA. At the same time, HCC cells were cultivated in vitro and axillary injected in nude mice to establish the xenograft model. The xenograft in the TO901317-treated group was slower and smaller than the control group. The protein expression of LXRα, Glut1, and MMP9 could be detected by Western blot and glucose level. As a result, TO901317 could inhibit the cell proliferation of HCC in a dose-dependent manner by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay. With the increase of TO901317 concentration, the cellular glucose concentration and ATP level were gradually decreased. Western blot results showed TO901317 could upregulate LXRα expression but downregulate MMP9 and Glut1 expression. Transwell and wound-healing analysis confirmed that, by increasing the concentration of TO901317, the cell invasion and migration were both decreased. LXRα small-interfering RNA (siRNA) could relieve the suppression effect of TO901317 on the cell invasion and migration and the expression of LXRα, Glut1, and MMP9. The glucose concentration was also raised. TO901317 could repress the progress of HCC cells by reducing the glucose concentration, upregulating LXRα expression, but downregulating the expression of Glut1 and MMP9. NEW & NOTEWORTHY This subject confirmed that TO901317, a specific liver X receptor agonist, could inhibit the progression of liver cancer through upregulating liver X receptor-α, downregulating the expression of glucose transporter-1 and matrix metalloproteinase-9, and decreasing the glucose content in SMMC-7721 and HepG2 cells.

Targeting mTOR in Acute Lymphoblastic Leukemia

Acute Lymphoblastic Leukemia (ALL) is an aggressive hematologic disorder and constitutes approximately 25% of cancer diagnoses among children and teenagers. Pediatric patients have a favourable prognosis, with 5-years overall survival rates near 90%, while adult ALL still correlates with poorer survival. However, during the past few decades, the therapeutic outcome of adult ALL was significantly ameliorated, mainly due to intensive pediatric-based protocols of chemotherapy. Mammalian (or mechanistic) target of rapamycin (mTOR) is a conserved serine/threonine kinase belonging to the phosphatidylinositol 3-kinase (PI3K)-related kinase family (PIKK) and resides in two distinct signalling complexes named mTORC1, involved in mRNA translation and protein synthesis and mTORC2 that controls cell survival and migration. Moreover, both complexes are remarkably involved in metabolism regulation. Growing evidence reports that mTOR dysregulation is related to metastatic potential, cell proliferation and angiogenesis and given that PI3K/Akt/mTOR network activation is often associated with poor prognosis and chemoresistance in ALL, there is a constant need to discover novel inhibitors for ALL treatment. Here, the current knowledge of mTOR signalling and the development of anti-mTOR compounds are documented, reporting the most relevant results from both preclinical and clinical studies in ALL that have contributed significantly into their efficacy or failure.

Myeloid Slc2a1-Deficient Murine Model Revealed Macrophage Activation and Metabolic Phenotype Are Fueled by GLUT1

Macrophages (MΦs) are heterogeneous and metabolically flexible, with metabolism strongly affecting immune activation. A classic response to proinflammatory activation is increased flux through glycolysis with a downregulation of oxidative metabolism, whereas alternative activation is primarily oxidative, which begs the question of whether targeting glucose metabolism is a viable approach to control MΦ activation. We created a murine model of myeloid-specific glucose transporter GLUT1 (Slc2a1) deletion. Bone marrow-derived MΦs (BMDM) from Slc2a1M-/- mice failed to uptake glucose and demonstrated reduced glycolysis and pentose phosphate pathway activity. Activated BMDMs displayed elevated metabolism of oleate and glutamine, yet maximal respiratory capacity was blunted in MΦ lacking GLUT1, demonstrating an incomplete metabolic reprogramming. Slc2a1M-/- BMDMs displayed a mixed inflammatory phenotype with reductions of the classically activated pro- and anti-inflammatory markers, yet less oxidative stress. Slc2a1M-/- BMDMs had reduced proinflammatory metabolites, whereas metabolites indicative of alternative activation-such as ornithine and polyamines-were greatly elevated in the absence of GLUT1. Adipose tissue MΦs of lean Slc2a1M-/- mice had increased alternative M2-like activation marker mannose receptor CD206, yet lack of GLUT1 was not a critical mediator in the development of obesity-associated metabolic dysregulation. However, Ldlr-/- mice lacking myeloid GLUT1 developed unstable atherosclerotic lesions. Defective phagocytic capacity in Slc2a1M-/- BMDMs may have contributed to unstable atheroma formation. Together, our findings suggest that although lack of GLUT1 blunted glycolysis and the pentose phosphate pathway, MΦ were metabolically flexible enough that inflammatory cytokine release was not dramatically regulated, yet phagocytic defects hindered MΦ function in chronic diseases.

Leptin and its receptor in glucose metabolism of T-cell lymphoma

T-cell lymphoma (TCL) is a group of heterogeneous disorders with a poor response to conventional treatment. In order to identify novel therapeutic targets, the present study investigated the effect of leptin and its receptor on glucose metabolism in TCL. The expression of the leptin receptor (ObR), and glucose transporter (Glut)1 and 4 was detected in TCL and reactive lymphoid hyperplasia (RLH) tissues by immunohistochemical analysis. A higher level of ObR expression was observed in the TCL tissues than in the RLH tissues (58.3 vs. 22.2%; P=0.012), and ObR overexpression was associated with high expression of Glut1 (P=0.007). In vitro analysis using the human TCL MOLT-3 cell line demonstrated that leptin stimulated cell glucose uptake via promoting recruitment and expression of Glut1, effects which were abolished by ObR-specific small interfering RNA (siRNA). Additionally, MOLT-3 cell viability was also increased following leptin treatment. ObR-specific siRNA abolished these responses. In conclusion, these results suggested that leptin serves a critical role in TCL glucose uptake via the ObR.

The hypoxia signalling pathway in haematological malignancies

Haematological malignancies are tumours that affect the haematopoietic and the lymphatic systems. Despite the huge efforts to eradicate these tumours, the percentage of patients suffering resistance to therapies and relapse still remains significant. The tumour environment favours drug resistance of cancer cells, and particularly of cancer stem/initiating cells. Hypoxia promotes aggressiveness, metastatic spread and relapse in most of the solid tumours. Furthermore, hypoxia is associated with worse prognosis and resistance to conventional treatments through activation of the hypoxia-inducible factors. Haematological malignancies are not considered solid tumours, and therefore, the role of hypoxia in these diseases was initially presumed to be inconsequential. However, hypoxia is a hallmark of the haematopoietic niche. Here, we will review the current understanding of the role of both hypoxia and hypoxia-inducible factors in different haematological tumours.

Altered Metabolism of Leukemic Cells: New Therapeutic Opportunity

The cancer metabolic program alters bioenergetic processes to meet the higher demands of tumor cells for biomass production, nucleotide synthesis, and NADPH-balancing redox homeostasis. It is widely accepted that cancer cells mostly utilize glycolysis, as opposed to normal cells, in which oxidative phosphorylation is the most employed bioenergetic process. Still, studies examining cancer metabolism had been overlooked for many decades, and it was only recently discovered that metabolic alterations affect both the oncogenic potential and therapeutic response. Since most of the published works concern solid tumors, in this comprehensive review, we aim to summarize knowledge about the metabolism of leukemia cells. Leukemia is a malignant disease that ranks first and fifth in cancer-related deaths in children and adults, respectively. Current treatment has reached its limits due to toxicity, and there has been a need for new therapeutic approaches. One of the possible scenarios is improved use of established drugs and another is to introduce new druggable targets. Herein, we aim to describe the complexity of leukemia metabolism and highlight cellular processes that could be targeted therapeutically and enhance the effectiveness of current treatments.

[Association between BIM gene and glucocorticoid resistance in children with acute lymphoblastic leukemia]

Acute lymphoblastic leukemia (ALL) is the most common malignant hematological disease in childhood. Glucocorticoids are frequently used in the chemoradiotherapy regimen for ALL and can induce the apoptosis of ALL cells through several signaling pathways, but about 10% of ALL children have poor response to glucocorticoids. Studies have revealed that glucocorticoids induce the apoptosis of ALL cells by upregulating the expression of BIM gene, and BIM gene is associated with glucocorticoid resistance in childhood ALL. This article reviews the recent studies on glucocorticoid resistance in childhood ALL, especially the role of BIM and its expression products in this process.

Eviction from the sanctuary: Development of targeted therapy against cell adhesion molecules in acute lymphoblastic leukemia

Acute lymphoblastic leukemia (ALL) is a malignant hematological disease afflicting hematopoiesis in the bone marrow. While 80%-90% of patients diagnosed with ALL will achieve complete remission at some point during treatment, ALL is associated with high relapse rate, with a 5-year overall survival rate of 68%. The initial remission failure and the high rate of relapse can be attributed to intrinsic chemoprotective mechanisms that allow persistence of ALL cells despite therapy. These mechanisms are mediated, at least in part, through the engagement of cell adhesion molecules (CAMs) within the bone marrow microenvironment. This review assembles CAMs implicated in protection of leukemic cells from chemotherapy. Such studies are limited in ALL. Therefore, CAMs that are associated with poor outcomes or are overexpressed in ALL and have been shown to be involved in chemoprotection in other hematological cancers are also included. It is likely that these molecules play parallel roles in ALL because the CAMs identified to be a factor in ALL chemoresistance also work similarly in other hematological malignancies. We review the signaling mechanisms activated by the engagement of CAMs that provide protection from chemotherapy. Development of targeted therapies against CAMs could improve outcome and raise the overall cure rate in ALL.

Proteome alterations associated with transformation of multiple myeloma to secondary plasma cell leukemia

Plasma cell leukemia is a rare and aggressive plasma cell neoplasm that may either originate de novo (primary PCL) or by leukemic transformation of multiple myeloma (MM) to secondary PCL (sPCL). The prognosis of sPCL is very poor, and currently no standard treatment is available due to lack of prospective clinical studies. In an attempt to elucidate factors contributing to transformation, we have performed super-SILAC quantitative proteome profiling of malignant plasma cells collected from the same patient at both the MM and sPCL stages of the disease. 795 proteins were found to be differentially expressed in the MM and sPCL samples. Gene ontology analysis indicated a metabolic shift towards aerobic glycolysis in sPCL as well as marked down-regulation of enzymes involved in glycan synthesis, potentially mediating altered glycosylation of surface receptors. There was no significant change in overall genomic 5-methylcytosine or 5-hydroxymethylcytosine at the two stages, indicating that epigenetic dysregulation was not a major driver of transformation to sPCL. The present study constitutes the first attempt to provide a comprehensive map of the altered protein expression profile accompanying transformation of MM to sPCL in a single patient, identifying several candidate proteins that can be targeted by currently available small molecule drugs. Our dataset furthermore constitutes a reference dataset for further proteomic analysis of sPCL transformation.

TRAF3 deficiency promotes metabolic reprogramming in B cells

The adaptor protein TNF receptor-associated factor 3 (TRAF3) is a critical regulator of B lymphocyte survival. B cell-specific TRAF3 deficiency results in enhanced viability and is associated with development of lymphoma and multiple myeloma. We show that TRAF3 deficiency led to induction of two proteins important for glucose metabolism, Glut1 and Hexokinase 2 (HXK2). This was associated with increased glucose uptake. In the absence of TRAF3, anaerobic glycolysis and oxidative phosphorylation were increased in B cells without changes in mitochondrial mass or reactive oxygen species. Chemical inhibition of glucose metabolism or glucose deprivation substantially attenuated the enhanced survival of TRAF3-deficient B cells, with a decrease in the pro-survival protein Mcl-1. Changes in Glut1 and Mcl-1 levels, glucose uptake and B cell number in the absence of TRAF3 were all dependent upon NF-κB inducing kinase (NIK). These results indicate that TRAF3 deficiency suffices to metabolically reprogram B cells, a finding that improves our understanding of the role of TRAF3 as a tumor suppressor, and suggests potential therapeutic strategies.

The PI3K pathway in B cell metabolism

B cell growth and proliferation is tightly regulated by signaling through the B cell receptor and by other membrane bound receptors responding to different cytokines. The PI3K signaling pathway has been shown to play a crucial role in B cell activation, differentiation and survival. Activated B cells undergo metabolic reprograming in response to changing energetic and biosynthetic demands. B cells also need to be able to coordinate metabolic activity and proliferation with nutrient availability. The PI3K signaling network has been implicated in regulating nutrient acquisition, utilization and biosynthesis, thus integrating receptor-mediated signaling with cell metabolism. In this review, we discuss the current knowledge about metabolic changes induced in activated B cells, strategies to adapt to metabolic stress and the role of PI3K signaling in these processes.

AMPK Is Essential to Balance Glycolysis and Mitochondrial Metabolism to Control T-ALL Cell Stress and Survival

T cell acute lymphoblastic leukemia (T-ALL) is an aggressive malignancy associated with Notch pathway mutations. While both normal activated and leukemic T cells can utilize aerobic glycolysis to support proliferation, it is unclear to what extent these cell populations are metabolically similar and if differences reveal T-ALL vulnerabilities. Here we show that aerobic glycolysis is surprisingly less active in T-ALL cells than proliferating normal T cells and that T-ALL cells are metabolically distinct. Oncogenic Notch promoted glycolysis but also induced metabolic stress that activated 5' AMP-activated kinase (AMPK). Unlike stimulated T cells, AMPK actively restrained aerobic glycolysis in T-ALL cells through inhibition of mTORC1 while promoting oxidative metabolism and mitochondrial Complex I activity. Importantly, AMPK deficiency or inhibition of Complex I led to T-ALL cell death and reduced disease burden. Thus, AMPK simultaneously inhibits anabolic growth signaling and is essential to promote mitochondrial pathways that mitigate metabolic stress and apoptosis in T-ALL.

Attacking the supply wagons to starve cancer cells to death

The constitutive anabolism of cancer cells not only supports proliferation but also addicts tumor cells to a steady influx of exogenous nutrients. Limiting access to metabolic substrates could be an effective and selective means to block cancer growth. In this review, we define the pathways by which cancer cells acquire the raw materials for anabolism, highlight the actionable proteins in each pathway, and discuss the status of therapeutic interventions that disrupt nutrient acquisition. Critical open questions to be answered before apical metabolic inhibitors can be successfully and safely deployed in the clinic are also outlined. In summary, recent studies provide strong support that substrate limitation is a powerful therapeutic strategy to effectively, and safely, starve cancer cells to death.