Glycogen synthase kinase 3alpha and 3beta mediate a glucose-sensitive antiapoptotic signaling pathway to stabilize Mcl-1

Pentamethylquercetin attenuates angiotensin II-induced abdominal aortic aneurysm formation by blocking nuclear translocation of C/EBPβ at Lys253

BACKGROUND

Pentamethylquercetin (PMQ) is a natural polymethyl flavonoid that possesses anti-apoptotic and other biological properties. Abdominal aortic aneurysm (AAA), a fatal vascular disease with a high risk of rupture, is associated with phenotypic switching and apoptosis of medial vascular smooth muscle cells (VSMCs). This study aimed to investigate the protective effects of PMQ on the development of AAA and the underlying mechanism.

METHODS

ApoE-/- mice were continuously infused with angiotensin II (Ang II) for 4 weeks to develop the AAA model. Intragastric administration of PMQ was initiated 5 days before Ang II infusion and continued for 4 weeks. In vitro, VSMCs were cultured and pretreated with PMQ, stimulated with Ang II. Real-time PCR, western blotting, and immunofluorescence staining were used to examine the roles and mechanisms of PMQ on the phenotypic switching and apoptosis of VSMCs.

RESULTS

PMQ dose-dependently reduced the incidence of Ang II-induced AAA, aneurysm diameter enlargement, elastin degradation, VSMCs phenotypic switching and apoptosis. Furthermore, PMQ also inhibited phenotypic switching and apoptosis in Ang II-stimulated VSMCs. PMQ exerted protective effects by regulating the C/EBPβ/PTEN/AKT/GSK-3β axis. AAV-mediated overexpression of PTEN reduced the therapeutic effects of PMQ in the AAA model mice, suggesting that the effects of PMQ on Ang II-mediated AAA formation were related to the PTEN/AKT/GSK-3β axis. PMQ inhibited VSMCs phenotypic switching and apoptosis by bounding to C/EBPβ at Lys253 with hydrogen bond to regulate C/EBPβ nuclear translocation and PTEN/AKT/GSK-3β axis, thereby inhibiting Ang II-induced AAA formation.

CONCLUSIONS

Pentamethylquercetin inhibits angiotensin II-induced abdominal aortic aneurysm formation by bounding to C/EBPβ at Lys253. Therefore, PMQ prevents the formation of AAA and reduces the incidence of AAA.

Congenital neutropenia: From lab bench to clinic bedside and back

Neutropenia is a hematological condition characterized by a decrease in absolute neutrophil count (ANC) in peripheral blood, typically classified in adults as mild (1-1.5 × 109/L), moderate (0.5-1 × 109/L), or severe (< 0.5 × 109/L). It can be categorized into two types: congenital and acquired. Congenital severe chronic neutropenia (SCN) arises from mutations in various genes, with different inheritance patterns, including autosomal recessive, autosomal dominant, and X-linked forms, often linked to mitochondrial diseases. The most common genetic cause is alterations in the ELANE gene. Some cases exist as non-syndromic neutropenia within the SCN spectrum, where genetic origins remain unidentified. The clinical consequences of congenital neutropenia depend on granulocyte levels and dysfunction. Infants with this condition often experience recurrent bacterial infections, with approximately half facing severe infections within their first six months of life. These infections commonly affect the respiratory system, digestive tract, and skin, resulting in symptoms like fever, abscesses, and even sepsis. The severity of these symptoms varies, and the specific organs and systems affected depend on the genetic defect. Congenital neutropenia elevates the risk of developing acute myeloid leukemia (AML) or myelodysplastic syndromes (MDS), particularly with certain genetic variants. SCN patients may acquire CSF3R and RUNX1 mutations, which can predict the development of leukemia. It is important to note that high-dose granulocyte colony-stimulating factor (G-CSF) treatment may have the potential to promote leukemogenesis. Treatment for neutropenia involves antibiotics, drugs that boost neutrophil production, or bone marrow transplants. Immediate treatment is essential due to the heightened risk of severe infections. In severe congenital or cyclic neutropenia (CyN), the primary therapy is G-CSF, often combined with antibiotics. The G-CSF dosage is gradually increased to normalize neutrophil counts. Hematopoietic stem cell transplants are considered for non-responders or those at risk of AML/MDS. In cases of WHIM syndrome, CXCR4 inhibitors can be effective. Future treatments may involve gene editing and the use of the diabetes drug empagliflozin to alleviate neutropenia symptoms.

Damage-induced pyroptosis drives endog thymic regeneration via induction of Foxn1 by purinergic receptor activation

Endogenous thymic regeneration is a crucial process that allows for the renewal of immune competence following stress, infection or cytoreductive conditioning. Fully understanding the molecular mechanisms driving regeneration will uncover therapeutic targets to enhance regeneration. We previously demonstrated that high levels of homeostatic apoptosis suppress regeneration and that a reduction in the presence of damage-induced apoptotic thymocytes facilitates regeneration. Here we identified that cell-specific metabolic remodeling after ionizing radiation steers thymocytes towards mitochondrial-driven pyroptotic cell death. We further identified that a key damage-associated molecular pattern (DAMP), ATP, stimulates the cell surface purinergic receptor P2Y2 on cortical thymic epithelial cells (cTECs) acutely after damage, enhancing expression of Foxn1, the critical thymic transcription factor. Targeting the P2Y2 receptor with the agonist UTPγS promotes rapid regeneration of the thymus in vivo following acute damage. Together these data demonstrate that intrinsic metabolic regulation of pyruvate processing is a critical process driving thymus repair and identifies the P2Y2 receptor as a novel molecular therapeutic target to enhance thymus regeneration.

Modulations in human neutrophil metabolome and S-glutathionylation of glycolytic pathway enzymes during the course of extracellular trap formation

Neutrophil extracellular trap formation (NETosis) has been irrefutably referred to as a distinct and unique form of active cell death with the purpose to counteract invading pathogens or augmenting the inflammatory cascade. Since the discovery, consistent efforts have been made to understand the various aspects of the initiation and sustenance of NETosis. In this study, using a global metabolomics approach during the phorbol 12-myristate 13-acetate (PMA) induced NETosis in human neutrophils, various metabolic pathways were found to be altered which includes intermediates related to, carbohydrate metabolism, and redox related metabolites, nucleic acid metabolism, and amino acids metabolism. Enrichment analysis of the metabolite sets highlighted the importance of the pentose phosphate pathway (PPP) and glutathione metabolism PMA-induced NETotic neutrophils. Further, analysis of the glutathyniolation status of neutrophil proteins by Matrix-assisted laser desorption/ionization-time of flight (MALDI-TOF) indicated six different glutathionylated proteins: among them, two metabolically important proteins were α-enolase and glyceraldehyde-3-phosphate dehydrogenase (GAPDH) with MALDI score 166 and 70 respectively. Other proteins were lactoferrin, β-actin, c-myc promoter-binding protein, and uracil DNA glycosylase with MALDI scores of 96, 167, 104, and 68 respectively. Besides, activation of signalling proteins involved in metabolic regulation is also correlated with NETosis. Altogether, a balance between reactive oxygen species-glutathione metabolism seems to regulate the activity of glycolytic enzymes such as GAPDH and α-enolase during PMA-induced NETosis in a time-dependent manner.

Enforcing GLUT3 expression in CD8+ T cells improves fitness and tumor control by promoting glucose uptake and energy storage

Despite the tremendous success of adoptive T-cell therapies (ACT) in fighting certain hematologic malignancies, not all patients respond, a proportion experience relapse, and effective ACT of most solid tumors remains elusive. In order to improve responses to ACT suppressive barriers in the solid tumor microenvironment (TME) including insufficient nutrient availability must be overcome. Here we explored how enforced expression of the high-affinity glucose transporter GLUT3 impacted tumor-directed T cells. Overexpression of GLUT3 in primary murine CD8⁺ T cells enhanced glucose uptake and increased glycogen and fatty acid storage, and was associated with increased mitochondrial fitness, reduced ROS levels, higher abundance of the anti-apoptotic protein Mcl-1, and better resistance to stress. Importantly, GLUT3-OT1 T cells conferred superior control of B16-OVA melanoma tumors and, in this same model, significantly improved survival. Moreover, a proportion of treated mice were cured and protected from re-challenge, indicative of long-term T cell persistence and memory formation. Enforcing expression of GLUT3 is thus a promising strategy to improve metabolic fitness and sustaining CD8⁺ T cell effector function in the context of ACT.

Supplying the trip to antibody production-nutrients, signaling, and the programming of cellular metabolism in the mature B lineage

The COVID pandemic has refreshed and expanded recognition of the vital role that sustained antibody (Ab) secretion plays in our immune defenses against microbes and of the importance of vaccines that elicit Ab protection against infection. With this backdrop, it is especially timely to review aspects of the molecular programming that govern how the cells that secrete Abs arise, persist, and meet the challenge of secreting vast amounts of these glycoproteins. Whereas plasmablasts and plasma cells (PCs) are the primary sources of secreted Abs, the process leading to the existence of these cell types starts with naive B lymphocytes that proliferate and differentiate toward several potential fates. At each step, cells reside in specific microenvironments in which they not only receive signals from cytokines and other cell surface receptors but also draw on the interstitium for nutrients. Nutrients in turn influence flux through intermediary metabolism and sensor enzymes that regulate gene transcription, translation, and metabolism. This review will focus on nutrient supply and how sensor mechanisms influence distinct cellular stages that lead to PCs and their adaptations as factories dedicated to Ab secretion. Salient findings of this group and others, sometimes exhibiting differences, will be summarized with regard to the journey to a distinctive metabolic program in PCs.

Targeting Glycolysis in Alloreactive T Cells to Prevent Acute Graft-Versus-Host Disease While Preserving Graft-Versus-Leukemia Effect

Alloreactive donor T cells undergo extensive metabolic reprogramming to become activated and induce graft-versus-host disease (GVHD) upon alloantigen encounter. It is generally thought that glycolysis, which promotes T cell growth and clonal expansion, is employed in this process. However, conflicting data have been reported regarding the requirement of glycolysis to induce T cell-mediated GVHD due to the lack of T cell-specific treatments using glycolysis inhibitors. Importantly, previous studies have not evaluated whether graft-versus-leukemia (GVL) activity is preserved in donor T cells deficient for glycolysis. As a critical component affecting the clinical outcome, it is necessary to assess the anti-tumor activity following treatment with metabolic modulators in preclinical models. In the present study, we utilized T cells selectively deficient for glucose transporter 1 (Glut1^T-KO), to examine the role of glycolysis exclusively in alloreactive T cells without off-targeting effects from antigen presenting cells and other cell types that are dependent on glycolysis. We demonstrated that transfer of Glut1^T-KO T cells significantly improved acute GVHD outcomes through increased apoptotic rates, impaired expansion, and decreased proinflammatory cytokine production. In addition to impaired GVHD development, donor Glut1^T-KO T cells mediated sufficient GVL activity to protect recipients from tumor development. A clinically relevant approach using donor T cells treated with a small molecule inhibitor of glycolysis, 2-Deoxy-D-glucose ex vivo, further demonstrated protection from tumor development. These findings indicate that treatment with glycolysis inhibitors prior to transplantation selectively eliminates alloreactive T cells, but spares non-alloreactive T cells including those that protect against tumor growth. The present study has established a definitive role for glycolysis in acute GVHD and demonstrated that acute GVHD can be selectively prevented through targeting glycolysis.

Nordentatin Inhibits Neuroblastoma Cell Proliferation and Migration through Regulation of GSK-3 Pathway

Cancer is caused by abnormal cell changes leading to uncontrolled cell growth. The specific characteristics of cancer cells, including the loss of apoptotic control and the ability to migrate into and invade the surrounding tissue, result in cancer cell metastasis to other parts of the body. Therefore, the inhibition of the proliferation, migration, and invasion of cancer cells are the principal goals in the treatment of cancer. This study aimed to investigate the inhibitory activity of nordentatin, a coumarin derivative isolated from Clausena harmandiana, regarding the proliferation and migration of human neuroblastoma cells (SH-SY5Y). Nordentatin at a concentration of 100 µM showed cell cytotoxicity toward SH-SY5Y that was significantly different from that of the control group (p < 0.01) at 24, 48, and 72 h. Moreover, nordentatin inhibited SH-SY5Y proliferation by inhibiting the antiapoptotic protein Mcl-1, leading to the cleavage of caspase-3 and resulting in the inhibition of a migratory protein, MMP-9, through the GSK-3 pathway (compared with cells treated with a GSK inhibitor). These results suggest that nordentatin inhibited the proliferation and migration of neuroblastoma cells through the GSK-3 pathway.

Mitochondrial metabolism as a potential therapeutic target in myeloid leukaemia

While the understanding of the genomic aberrations that underpin chronic and acute myeloid leukaemia (CML and AML) has allowed the development of therapies for these diseases, limitations remain. These become apparent when looking at the frequency of treatment resistance leading to disease relapse in leukaemia patients. Key questions regarding the fundamental biology of the leukaemic cells, such as their metabolic dependencies, are still unresolved. Even though a majority of leukaemic cells are killed during initial treatment, persistent leukaemic stem cells (LSCs) and therapy-resistant cells are still not eradicated with current treatments, due to various mechanisms that may contribute to therapy resistance, including cellular metabolic adaptations. In fact, recent studies have shown that LSCs and treatment-resistant cells are dependent on mitochondrial metabolism, hence rendering them sensitive to inhibition of mitochondrial oxidative phosphorylation (OXPHOS). As a result, rewired energy metabolism in leukaemic cells is now considered an attractive therapeutic target and the significance of this process is increasingly being recognised in various haematological malignancies. Therefore, identifying and targeting aberrant metabolism in drug-resistant leukaemic cells is an imperative and a relevant strategy for the development of new therapeutic options in leukaemia. In this review, we present a detailed overview of the most recent studies that present experimental evidence on how leukaemic cells can metabolically rewire, more specifically the importance of OXPHOS in LSCs and treatment-resistant cells, and the current drugs available to target this process. We highlight that uncovering specific energy metabolism dependencies will guide the identification of new and more targeted therapeutic strategies for myeloid leukaemia.

Targeting the Interplay between Cancer Metabolic Reprogramming and Cell Death Pathways as a Viable Therapeutic Path

In cancer cells, metabolic adaptations are often observed in terms of nutrient absorption, biosynthesis of macromolecules, and production of energy necessary to meet the needs of the tumor cell such as uncontrolled proliferation, dissemination, and acquisition of resistance to death processes induced by both unfavorable environmental conditions and therapeutic drugs. Many oncogenes and tumor suppressor genes have a significant effect on cellular metabolism, as there is a close relationship between the pathways activated by these genes and the various metabolic options. The metabolic adaptations observed in cancer cells not only promote their proliferation and invasion, but also their survival by inducing intrinsic and acquired resistance to various anticancer agents and to various forms of cell death, such as apoptosis, necroptosis, autophagy, and ferroptosis. In this review we analyze the main metabolic differences between cancer and non-cancer cells and how these can affect the various cell death pathways, effectively determining the susceptibility of cancer cells to therapy-induced death. Targeting the metabolic peculiarities of cancer could represent in the near future an innovative therapeutic strategy for the treatment of those tumors whose metabolic characteristics are known.

Therapy Resistance in Cancers: Phenotypic, Metabolic, Epigenetic and Tumour Microenvironmental Perspectives

BACKGROUND

Chemoresistance is a vital problem in cancer therapy where cancer cells develop mechanisms to encounter the effect of chemotherapeutics, resulting in cancer recurrence. In addition, chemotherapy- resistant leads to the formation of a more aggressive form of cancer cells, which, in turn, contributes to the poor survival of patients with cancer.

OBJECTIVE

In this review, we aimed to provide an overview of how the therapy resistance property evolves in cancer cells, contributing factors and their role in cancer chemoresistance, and exemplified the problems of some available therapies.

METHODS

The published literature on various electronic databases including, Pubmed, Scopus, Google scholar containing keywords cancer therapy resistance, phenotypic, metabolic and epigenetic factors, were vigorously searched, retrieved and analyzed.

RESULTS

Cancer cells have developed a range of cellular processes, including uncontrolled activation of Epithelial- Mesenchymal Transition (EMT), metabolic reprogramming and epigenetic alterations. These cellular processes play significant roles in the generation of therapy resistance. Furthermore, the microenvironment where cancer cells evolve effectively contributes to the process of chemoresistance. In tumour microenvironment immune cells, Mesenchymal Stem Cells (MSCs), endothelial cells and cancer-associated fibroblasts (CAFs) contribute to the maintenance of therapy-resistant phenotype via the secretion of factors that promote resistance to chemotherapy.

CONCLUSION

To conclude, as these factors hinder successful cancer therapies, therapeutic resistance property of cancer cells is a subject of intense research, which in turn could open a new horizon to aim for developing efficient therapies.

Mitochondrial metabolism: powering new directions in acute myeloid leukemia

There has been an explosion of knowledge about the role of metabolism and the mitochondria in acute myeloid leukemia (AML). We have also recently seen several waves of novel therapies change the treatment landscape for AML, such as the selective B-cell lymphoma 2 (BCL-2) inhibitor venetoclax. In this new context, we review the rapidly advancing literature on the role of metabolism and the mitochondria in AML pathogenesis, and how these are interwoven with the mechanisms of action for novel therapeutics in AML. We also review the role of oxidative phosphorylation (OxPhos) in maintaining leukemia stem cells (LSCs), how recurrent genomic alterations in AML alter downstream metabolism, and focus on how the BCL-2 pathway and the mitochondria are inextricably linked in AML. Thus, we provide an overview of the mitochondria and metabolism in the context of our new therapeutic world for AML and outline how targeting these vulnerabilities may produce novel therapeutic strategies.

AKT signaling restrains tumor suppressive functions of FOXO transcription factors and GSK3 kinase in multiple myeloma

The phosphatidylinositide-3 kinases and the downstream mediator AKT drive survival and proliferation of multiple myeloma (MM) cells. AKT signaling is active in MM and has pleiotropic effects; however, the key molecular aspects of AKT dependency in MM are not fully clear. Among the various downstream AKT targets are the Forkhead box O (FOXO) transcription factors (TFs) and glycogen synthase kinase 3 (GSK3), which are negatively regulated by AKT signaling. Here we show that abrogation of AKT signaling in MM cells provokes cell death and cell cycle arrest, which crucially depends on both FOXO TFs and GSK3. Based on gene expression profiling, we defined a FOXO-repressed gene set that has prognostic significance in a large cohort of patients with MM, indicating that AKT-mediated gene activation is associated with inferior overall survival. We further show that AKT signaling stabilizes the antiapoptotic myeloid cell leukemia 1 (MCL1) protein by inhibiting FOXO- and GSK3-mediated MCL1 turnover. In concordance, abrogation of AKT signaling greatly sensitized MM cells for an MCL1-targeting BH3-mimetic, which is currently in clinical development. Taken together, our results indicate that AKT activity is required to restrain the tumor-suppressive functions of FOXO and GSK3, thereby stabilizing the antiapoptotic protein MCL1 in MM. These novel insights into the role of AKT in MM pathogenesis and MCL1 regulation provide opportunities to improve targeted therapy for patients with MM.

The Role of Metabolism in Tumor Immune Evasion: Novel Approaches to Improve Immunotherapy

The tumor microenvironment exhibits altered metabolic properties as a consequence of the needs of tumor cells, the natural selection of the most adapted clones, and the selfish relationship with other cell types. Beyond its role in supporting uncontrolled tumor growth, through energy and building materials obtention, metabolism is a key element controlling tumor immune evasion. Immunotherapy has revolutionized the treatment of cancer, being the first line of treatment for multiple types of malignancies. However, many patients either do not benefit from immunotherapy or eventually relapse. In this review we overview the immunoediting process with a focus on the metabolism-related elements that are responsible for increased immune evasion, either through reduced immunogenicity or increased resistance of tumor cells to the apoptotic action of immune cells. Finally, we describe the main molecules to modulate these immune evasion processes through the control of the metabolic microenvironment as well as their clinical developmental status.

Mitochondria: The metabolic switch of cellular oncogenic transformation

Mitochondria, well recognized as the "powerhouse" of cells, are maternally inherited organelles with bacterial ancestry that play essential roles in a myriad of cellular functions. It has become profoundly evident that mitochondria regulate a wide array of cellular and metabolic functions, including biosynthetic metabolism, cell signaling, redox homeostasis, and cell survival. Correspondingly, defects in normal mitochondrial functioning have been implicated in various human malignancies. Cancer development involves the activation of oncogenes, inactivation of tumor suppressor genes, and impairment of apoptotic programs in cells. Mitochondria have been recognized as the site of key metabolic switches for normal cells to acquire a malignant phenotype. This review outlines the role of mitochondria in human malignancies and highlights potential aspects of mitochondrial metabolism that could be targeted for therapeutic development.

Electron transport chain activity is a predictor and target for venetoclax sensitivity in multiple myeloma

The BCL-2 antagonist venetoclax is highly effective in multiple myeloma (MM) patients exhibiting the 11;14 translocation, the mechanistic basis of which is unknown. In evaluating cellular energetics and metabolism of t(11;14) and non-t(11;14) MM, we determine that venetoclax-sensitive myeloma has reduced mitochondrial respiration. Consistent with this, low electron transport chain (ETC) Complex I and Complex II activities correlate with venetoclax sensitivity. Inhibition of Complex I, using IACS-010759, an orally bioavailable Complex I inhibitor in clinical trials, as well as succinate ubiquinone reductase (SQR) activity of Complex II, using thenoyltrifluoroacetone (TTFA) or introduction of SDHC R72C mutant, independently sensitize resistant MM to venetoclax. We demonstrate that ETC inhibition increases BCL-2 dependence and the ‘primed’ state via the ATF4-BIM/NOXA axis. Further, SQR activity correlates with venetoclax sensitivity in patient samples irrespective of t(11;14) status. Use of SQR activity in a functional-biomarker informed manner may better select for MM patients responsive to venetoclax therapy.

Venetoclax monotherapy is effective in 40% of t(11:14) positive multiple myeloma (MM). Here, the authors show that electron transport chain complex I (CI) and complex II (CII) activity predict MM sensitivity to venetoclax, and inhibition of CI with IACS-010759 or CII with TTFA increase sensitivity.

The potential role of glycogen metabolism in diffuse large B-cell lymphoma

Diffuse large B-cell lymphoma (DLBCL) is a common and aggressive form of non-Hodgkin lymphoma that may become refractory to available standard therapies, resulting in the need for the development of novel therapeutic targets. Increased metabolic activity of DLBCL tumor cells associated with high expression of glycolysis related proteins, such as glucose transporters and hexokinases, have already been described and indicates a pivotal role for glucose and glycogen metabolism in the malignant progression of the disease. Moreover, several enzymes involved in glycolysis and glycogen metabolism, including hexokinases and glycogen synthase kinase-3, are key molecules in mediating cell survival signaling, indicating that glucose/glycogen metabolism is tightly linked to the cell survival and can potentially be targeted for therapeutic purposes in DLBCL. In this review, we provide a summary of glycogen and glucose metabolism and discuss their significance in the metabolic reprograming that leads to cell survival and proliferation in DLBCL.

Cancer Metabolism and the Evasion of Apoptotic Cell Death

Cellular growth and proliferation depend upon the acquisition and synthesis of specific metabolites. These metabolites fuel the bioenergy, biosynthesis, and redox potential required for duplication of cellular biomass. Multicellular organisms maintain tissue homeostasis by balancing signals promoting proliferation and removal of cells via apoptosis. While apoptosis is in itself an energy dependent process activated by intrinsic and extrinsic signals, whether specific nutrient acquisition (elevated or suppressed) and their metabolism regulates apoptosis is less well investigated. Normal cellular metabolism is regulated by lineage specific intrinsic features and microenvironment driven extrinsic features. In the context of cancer, genetic abnormalities, unconventional microenvironments and/or therapy engage constitutive pro-survival signaling to re-program and rewire metabolism to maintain survival, growth, and proliferation. It thus becomes particularly relevant to understand whether altered nutrient acquisition and metabolism in cancer can also contribute to the evasion of apoptosis and consequently therapy resistance. Our review attempts to dissect a causal relationship between two cancer hallmarks, i.e., deregulated cellular energetics and the evasion of programmed cell death with primary focus on the intrinsic pathway of apoptosis.

Mitochondria as emerging targets for therapies against T cell acute lymphoblastic leukemia

Acute lymphoblastic leukemia (ALL) comprises a heterogeneous group of hematologic malignancies, arising from diverse genetic alterations in the early lymphocyte development. T-cell subtype of ALL (T-ALL) accounts for about 15% and 25% of ALL in children and adults, respectively. Being less frequent among ALL subtypes, T-ALL represents a high-risk factor for poor prognosis due to its aggressiveness and resistance to common antileukemic drugs. Mitochondria were widely explored recently as a target for anticancer treatment because they are involved in a metabolic reprogramming of a cancer cell and play key roles in reactive oxygen species generation, Ca²⁺ signaling, and cell death induction. Accordingly, a new class of anticancer compounds named mitocans has been developed, which target mitochondria at distinct crucial points to promote their dysfunction and subsequent cell death. The present review analyses the role of mitochondria in malignant reprogramming and emerging therapeutic strategies targeting mitochondria as an "Achilles' heel" in T-ALL, with an emphasis on BH3 mimetics, sequestering pro-survival BCL proteins and voltage-dependent anion channel (VDAC)1-directed drugs, which promote the suppression of aerobic glycolysis, VDAC1 closure, mitochondrial Ca²⁺ overload, stoppage of the oxidative phosphorylation, oxidative stress, and release of proapoptotic factors.

Molecular regulation of peripheral B cells and their progeny in immunity

In this review, Boothby et al. summarize some salient advances toward elucidation of the molecular programming of the fate choices and function of B cells in the periphery. They also note unanswered questions that pertain to differences among subsets of B lymphocytes and plasma cells.

Mature B lymphocytes are crucial components of adaptive immunity, a system essential for the evolutionary fitness of mammals. Adaptive lymphocyte function requires an initially naïve cell to proliferate extensively and its progeny to have the capacity to assume a variety of fates. These include either terminal differentiation (the long-lived plasma cell) or metastable transcriptional reprogramming (germinal center and memory B cells). In this review, we focus principally on the regulation of differentiation and functional diversification of the “B2” subset. An overview is combined with an account of more recent advances, including initial work on mechanisms that eliminate DNA methylation and potential links between intracellular metabolites and chromatin editing.

Targeting Mcl-1 and other Bcl-2 family member proteins in cancer therapy

Regulation of both the extrinsic and the mitochondria-dependent intrinsic apoptotic pathways plays a key role in the development of the hematopoietic system, for sustaining cell survival during generation of various cell types, in eliminating cells with dual identities such as CD4/CD8 double-positive cells (Hettmann, Didonato, Karin, & Leiden, 1999; Ogasawara, Suda, & Nagata, 1995), for sustaining cells during the rapid clonal expansion phase (Schirmer, Vallejo, Weyand, & Gronzy, 1998), as well as eliminating cells during the contraction phase (Yajima et al., 2006). The anti-apoptotic protein Mcl-1 is necessary for sustaining hematopoietic stem cells (HPS) (Akashi et al., 2003; Akashi, Traver, Miyamoto, & Weissman, 2000). The anti-apoptotic factors Mcl-1, Bcl-2, and Bcl-xL were also found to be over-expressed in acute myeloid leukemia (AML) (Kaufmann et al., 2016) and acute lymphocytic leukemia (ALL) (Findley, Gu, Yeager, & Zhou, 1997), suggesting that dis-regulated apoptotic processes could be a factor in the instigation of leukemia and/or its relapse. Molecules targeting these proteins were used as single agents to treat leukemia. However, by using a set of recently developed specific molecule inhibitors targeting anti-apoptotic proteins, distinct roles are being discovered for these anti-apoptotic proteins during hematopoietic and tumor development. Furthermore, using these inhibitors in proper combinations can effectively induce apoptosis in various solid tumors, even though each agent on its own cannot induce apoptosis in them. These new findings suggest that inhibiting anti-apoptotic elements can induce apoptosis without external stimuli in most cells, but it comes with a risk that some combinations could also trigger apoptosis in healthy cells. One way to address the safety issue is by limiting exposure to all the agents to only cancer cells, thus making the combination safe and effective. In this article, we review this rapidly developing idea in cancer research.

Infection with flaviviruses requires BCLXL for cell survival

BCL2 family proteins including pro-survival proteins, BH3-only proteins and BAX/BAK proteins control mitochondria-mediated apoptosis to maintain cell homeostasis via the removal of damaged cells and pathogen-infected cells. In this study, we examined the roles of BCL2 proteins in the induction of apoptosis in cells upon infection with flaviviruses, such as Japanese encephalitis virus, Dengue virus and Zika virus. We showed that survival of the infected cells depends on BCLX_L, a pro-survival BCL2 protein due to suppression of the expression of another pro-survival protein, MCL1. Treatment with BCLX_L inhibitors, as well as deficient BCLX_L gene expression, induced BAX/BAK-dependent apoptosis upon infection with flaviviruses. Flavivirus infection attenuates cellular protein synthesis, which confers reduction of short-half-life proteins like MCL1. Inhibition of BCLX_L increased phagocytosis of virus-infected cells by macrophages, thereby suppressing viral dissemination and chemokine production. Furthermore, we examined the roles of BCLX_L in the death of JEV-infected cells during in vivo infection. Haploinsufficiency of the BCLX_L gene, as well as administration of BH3 mimetic compounds, increased survival rate after challenge of JEV infection and suppressed inflammation. These results suggest that BCLX_L plays a crucial role in the survival of cells infected with flaviviruses, and that BCLX_L may provide a novel antiviral target to suppress propagation of the family of Flaviviridae viruses.

The genus Flavivirus including Japanese encephalitis virus, Dengue virus, and Zika virus all of which are mosquito-borne human pathogen and cause serious diseases in humans. Therefore, the development of effective vaccines and antivirals against several flaviviruses is still needed. BCL2 family proteins control mitochondria-mediated apoptosis to maintain cell homeostasis via the removal of damaged cells and pathogen-infected cells, deregulation of which leads to severe diseases including cancer and autoimmune diseases. Here, we showed that BCLX_L is a critical cell survival factor during infection with flaviviruses, and that inhibition of BCLX_L by treatment with BH3 mimetics restricts the production of infectious particles and the expression of chemokines in vitro and in vivo. Inhibition of BCLX_L induces apoptosis in cells infected with flaviviruses and these cells are quickly removed by engulfment of phagocytes, which leads to inhibition of virus dissemination without any inflammatory reaction. Based on these data, BCLX_L would appear to be a suitable target for the development of novel antivirals against a broad range of flavivirus infections.

Metabolic Regulation of the Immune Humoral Response

Productive humoral responses require that naive B cells and their differentiated progeny move among distinct micro-environments. In this review, we discuss how studies are beginning to address the nature of these niches as well as the interplay between cellular signaling, metabolic programming, and adaptation to the locale. Recent work adds evidence to the expectation that B cells at distinct stages of development or functional subsets are influenced by the altered profiles of nutrients and metabolic by-products that distinguish these sites. Moreover, emerging findings reveal a cross-talk among the external milieu, signal transduction pathways, and transcription factors that direct B cell fate in the periphery.

Targeting the Akt, GSK-3, Bcl-2 axis in acute myeloid leukemia

Over the last few decades, there has been significant progress in the understanding of the pathogenetic mechanisms of the Acute Myeloid Leukemia (AML). However, despite important advances in elucidating molecular mechanisms, the treatment of AML has not improved significantly, remaining anchored at the standard chemotherapy regimen "3 + 7", with the prognosis of patients remaining severe, especially for the elderly and for those not eligible for transplant procedures. The biological and clinical heterogeneity of AML represents the major obstacle that hinders the improvement of prognosis and the identification of new effective therapeutic approaches. To date, abundant information has been collected on the genetic and molecular alterations of AML carrying prognostic significance. However, not enough is known on how AML progenitors regulate proliferation and survival by redundant and cross-talking signal transduction pathways (STP). Furthermore, it remains unclear how such complicated network affects prognosis and therapeutic treatment options, although many of these molecular determinants are potentially attractive for their druggable characteristics. In this review, some of the key STP frequently deregulated in AML, such as PI3k/Akt/mTOR pathway, GSK3 and components of Bcl-2 family of proteins, are summarized, highlighting in addition their interplay. Based on this information, we reviewed new targeted therapeutic approaches, focusing on the aberrant networks that sustain the AML blast proliferation, survival and drug resistance, aiming to improve disease treatment. Finally, we reported the approaches aimed at disrupting key signaling cross-talk overcoming resistances based on the combination of different targeting therapeutic strategies.

Multinuclear NMR and MRI Reveal an Early Metabolic Response to mTOR Inhibition in Sarcoma

Biomarkers predicting rapalog responses in sarcomas where PI3K and mTOR are often hyperactivated could improve the suitable recruitment of responsive patients to clinical trials. PI3K/mTOR pathway activation drives energy production by regulating anaerobic glycolysis in cancer cells, suggesting a route toward a monitoring strategy. In this study, we took a multimodality approach to evaluate the phenotypic effects and metabolic changes that occur with inhibition of the PI3K/mTOR pathway. Its central role in regulating glycolysis in human sarcomas was evaluated by short- and long-term rapamycin treatment in sarcoma cell lines. We observed an overall decrease in lactate production in vitro, followed by cell growth inhibition. In vivo, we observed a similar quantitative reduction in lactate production as monitored by hyperpolarized MRI, also followed by tumor size changes. This noninvasive imaging method could distinguish reduced cell proliferation from induction of cell death. Our results illustrate the use of hyperpolarized MRI as a sensitive technique to monitor drug-induced perturbation of the PI3K/mTOR pathway in sarcomas. Cancer Res; 77(11); 3113-20. ©2017 AACR.

Gsk3 is a metabolic checkpoint regulator in B cells

B cells predominate in a quiescent state until antigen is encountered, which results in rapid growth, proliferation and differentiation. These distinct cell states are likely accompanied by differing metabolic needs, yet little is known about the metabolic control of B cell fate. Here we show that glycogen synthase kinase 3 (GSK3) is a metabolic sensor that promotes the survival of naïve recirculating B cells by restricting cell mass accumulation. In antigen-driven responses, GSK3 was selectively required for CD40-mediated regulation of B cell size, mitochondria biogenesis, glycolysis and reactive oxygen species (ROS) production. GSK3 was required to prevent metabolic collapse and ROS-induced apoptosis when glucose became limiting, functioning in part by repressing c-Myc-dependent growth. Importantly, we found that GSK3 was required for the generation and maintenance of germinal center B cells, which require high glycolytic activity to support growth and proliferation in a hypoxic microenvironment.

How to unleash mitochondrial apoptotic blockades to kill cancers?

Apoptosis, especially the intrinsic mitochondrial cell death pathway, is regulated by the BCL-2 family of proteins. Defects in apoptotic machinery are one of the main mechanisms that cells employ to evade cell death and become cancerous. Targeting the apoptotic defects, either by direct inhibition of BCL-2 family proteins or through modulation of regulatory pathways, can restore cell sensitivity to cell death. This review will focus on the aspects of BCL-2 family proteins, their interactions with kinase pathways, and how novel targeted agents can help overcome the apoptotic blockades. Furthermore, functional assays, such as BH3 profiling, may help in predicting responses to chemotherapies and aid in the selection of combination therapies by determining the mitochondrial threshold for initiating cell death.

Cycloheximide Can Induce Bax/Bak Dependent Myeloid Cell Death Independently of Multiple BH3-Only Proteins

Apoptosis mediated by Bax or Bak is usually thought to be triggered by BH3-only members of the Bcl-2 protein family. BH3-only proteins can directly bind to and activate Bax or Bak, or indirectly activate them by binding to anti-apoptotic Bcl-2 family members, thereby relieving their inhibition of Bax and Bak. Here we describe a third way of activation of Bax/Bak dependent apoptosis that does not require triggering by multiple BH3-only proteins. In factor dependent myeloid (FDM) cell lines, cycloheximide induced apoptosis by a Bax/Bak dependent mechanism, because Bax^-/-Bak^-/- lines were profoundly resistant, whereas FDM lines lacking one or more genes for BH3-only proteins remained highly sensitive. Addition of cycloheximide led to the rapid loss of Mcl-1 but did not affect the expression of other Bcl-2 family proteins. In support of these findings, similar results were observed by treating FDM cells with the CDK inhibitor, roscovitine. Roscovitine reduced Mcl-1 abundance and caused Bax/Bak dependent cell death, yet FDM lines lacking one or more genes for BH3-only proteins remained highly sensitive. Therefore Bax/Bak dependent apoptosis can be regulated by the abundance of anti-apoptotic Bcl-2 family members such as Mcl-1, independently of several known BH3-only proteins.

Metformin inhibits cell cycle progression of B-cell chronic lymphocytic leukemia cells

B-cell chronic lymphocytic leukemia (CLL) was believed to result from clonal accumulation of resting apoptosis-resistant malignant B lymphocytes. However, it became increasingly clear that CLL cells undergo, during their life, iterative cycles of re-activation and subsequent clonal expansion. Drugs interfering with CLL cell cycle entry would be greatly beneficial in the treatment of this disease.

1, 1-Dimethylbiguanide hydrochloride (metformin), the most widely prescribed oral hypoglycemic agent, inexpensive and well tolerated, has recently received increased attention for its potential antitumor activity. We wondered whether metformin has apoptotic and anti-proliferative activity on leukemic cells derived from CLL patients.

Metformin was administered in vitro either to quiescent cells or during CLL cell activation stimuli, provided by classical co-culturing with CD40L-expressing fibroblasts.

At doses that were totally ineffective on normal lymphocytes, metformin induced apoptosis of quiescent CLL cells and inhibition of cell cycle entry when CLL were stimulated by CD40-CD40L ligation. This cytostatic effect was accompanied by decreased expression of survival- and proliferation-associated proteins, inhibition of signaling pathways involved in CLL disease progression and decreased intracellular glucose available for glycolysis.

In drug combination experiments, metformin lowered the apoptotic threshold and potentiated the cytotoxic effects of classical and novel antitumor molecules.

Our results indicate that, while CLL cells after stimulation are in the process of building their full survival and cycling armamentarium, the presence of metformin affects this process.

The reduced concentration of citrate in cancer cells: An indicator of cancer aggressiveness and a possible therapeutic target

Proliferating cells reduce their oxidative metabolism and rely more on glycolysis, even in the presence of O₂ (Warburg effect). This shift in metabolism reduces citrate biosynthesis and diminishes intracellular acidity, both of which promote glycolysis sustaining tumor growth. Because citrate is the donor of acetyl-CoA, its reduced production favors a deacetylation state of proteins favoring resistance to apoptosis and epigenetic changes, both processes contributing to tumor aggressiveness. Citrate levels could be monitored as an indicator of cancer aggressiveness (as already shown in human prostate cancer) and/or could serve as a biomarker for response to therapy. Strategies aiming to increase cytosolic citrate should be developed and tested in humans, knowing that experimental studies have shown that administration of citrate and/or inhibition of ACLY arrest tumor growth, inhibit the expression of the key anti-apoptotic factor Mcl-1, reverse cell dedifferentiation and increase sensibility to cisplatin.

Effects of mutations in Wnt/β-catenin, hedgehog, Notch and PI3K pathways on GSK-3 activity-Diverse effects on cell growth, metabolism and cancer

Glycogen synthase kinase-3 (GSK-3) is a serine/threonine kinase that participates in an array of critical cellular processes. GSK-3 was first characterized as an enzyme that phosphorylated and inactivated glycogen synthase. However, subsequent studies have revealed that this moon-lighting protein is involved in numerous signaling pathways that regulate not only metabolism but also have roles in: apoptosis, cell cycle progression, cell renewal, differentiation, embryogenesis, migration, regulation of gene transcription, stem cell biology and survival. In this review, we will discuss the roles that GSK-3 plays in various diseases as well as how this pivotal kinase interacts with multiple signaling pathways such as: PI3K/PTEN/Akt/mTOR, Ras/Raf/MEK/ERK, Wnt/beta-catenin, hedgehog, Notch and TP53. Mutations that occur in these and other pathways can alter the effects that natural GSK-3 activity has on regulating these signaling circuits that can lead to cancer as well as other diseases. The novel roles that microRNAs play in regulation of the effects of GSK-3 will also be evaluated. Targeting GSK-3 and these other pathways may improve therapy and overcome therapeutic resistance.

A novel small-molecule IAP antagonist, AZD5582, draws Mcl-1 down-regulation for induction of apoptosis through targeting of cIAP1 and XIAP in human pancreatic cancer

Inhibitor of apoptosis proteins (IAPs) plays an important role in controlling cancer cell survival. IAPs have therefore attracted considerable attention as potential targets in anticancer therapy. In this study, we investigated the anti-tumor effect of AZD5582, a novel small-molecule IAP inhibitor, in human pancreatic cancer cells. Treating human pancreatic cancer cells with AZD5582 differentially induced apoptosis, dependent on the expression of p-Akt and p-XIAP. Moreover, the knockdown of endogenous Akt or XIAP via RNA interference in pancreatic cancer cells, which are resistant to AZD5582, resulted in increased sensitivity to AZD5582, whereas ectopically expressing Akt or XIAP led to resistance to AZD5582. Additionally, AZD5582 targeted cIAP1 to induce TNF-α-induced apoptosis. More importantly, AZD5582 induced a decrease of Mcl-1 protein, a member of the Bcl-2 family, but not that of Bcl-2 and Bcl-xL. Interestingly, ectopically expressing XIAP and cIAP1 inhibited the AZD5582-induced decrease of Mcl-1 protein, which suggests that AZD5582 elicits Mcl-1 decrease for apoptosis induction by targeting of XIAP and cIAP1. Taken together, these results indicate that sensitivity to AZD5582 is determined by p-Akt-inducible XIAP phosphorylation and by targeting cIAP1. Furthermore, Mcl-1 in pancreatic cancer may act as a potent marker to analyze the therapeutic effects of AZD5582.

Suppression of Glut1 and Glucose Metabolism by Decreased Akt/mTORC1 Signaling Drives T Cell Impairment in B Cell Leukemia

Leukemia can promote T cell dysfunction and exhaustion that contributes to increased susceptibility to infection and mortality. The treatment-independent mechanisms that mediate leukemia-associated T cell impairments are poorly understood, but metabolism tightly regulates T cell function and may contribute. In this study, we show that B cell leukemia causes T cells to become activated and hyporesponsive with increased PD-1 and TIM3 expression similar to exhausted T cells and that T cells from leukemic hosts become metabolically impaired. Metabolic defects included reduced Akt/mammalian target of rapamycin complex 1 (mTORC1) signaling, decreased expression of the glucose transporter Glut1 and hexokinase 2, and reduced glucose uptake. These metabolic changes correlated with increased regulatory T cell frequency and expression of PD-L1 and Gal-9 on both leukemic and stromal cells in the leukemic microenvironment. PD-1, however, was not sufficient to drive T cell impairment, as in vivo and in vitro anti-PD-1 blockade on its own only modestly improved T cell function. Importantly, impaired T cell metabolism directly contributed to dysfunction, as a rescue of T cell metabolism by genetically increasing Akt/mTORC1 signaling or expression of Glut1 partially restored T cell function. Enforced Akt/mTORC1 signaling also decreased expression of inhibitory receptors TIM3 and PD-1, as well as partially improved antileukemia immunity. Similar findings were obtained in T cells from patients with acute or chronic B cell leukemia, which were also metabolically exhausted and had defective Akt/mTORC1 signaling, reduced expression of Glut1 and hexokinase 2, and decreased glucose metabolism. Thus, B cell leukemia-induced inhibition of T cell Akt/mTORC1 signaling and glucose metabolism drives T cell dysfunction.

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.

Metabolic Regulation of Apoptosis in Cancer

Apoptosis is a cellular suicide program that plays a critical role in development and human diseases, including cancer. Cancer cells evade apoptosis, thereby enabling excessive proliferation, survival under hypoxic conditions, and acquired resistance to therapeutic agents. Among various mechanisms that contribute to the evasion of apoptosis in cancer, metabolism is emerging as one of the key factors. Cellular metabolites can regulate functions of pro- and antiapoptotic proteins. In turn, p53, a regulator of apoptosis, also controls metabolism by limiting glycolysis and facilitating mitochondrial respiration. Consequently, with dysregulated metabolism and p53 inactivation, cancer cells are well-equipped to disable the apoptotic machinery. In this article, we review how cellular apoptosis is regulated and how metabolism can influence the signaling pathways leading to apoptosis, especially focusing on how glucose and lipid metabolism are altered in cancer cells and how these alterations can impact the apoptotic pathways.

Effect of standard tuberculosis treatment on naive, memory and regulatory T-cell homeostasis in tuberculosis-diabetes co-morbidity

Perturbations in CD4(+) and CD8(+) T-cell phenotype and function are hallmarks of tuberculosis-diabetes co-morbidity. However, their contribution to the pathogenesis of this co-morbidity and the effect of anti-tuberculosis treatment on the phenotype of the T-cell subsets is poorly understood. In this study, we examined the frequency of different T-cell subsets in individuals with pulmonary tuberculosis (PTB) with diabetes mellitus (DM) or without coincident diabetes mellitus (NDM) before, during and after completion of anti-tuberculosis chemotherapy. PTB-DM is characterized by heightened frequencies of central memory CD4(+) and CD8(+) T cells and diminished frequencies of naive, effector memory and/or effector CD4(+) and CD8(+) T cells at baseline and after 2 months of treatment but not following treatment completion in comparison with PTB-NDM. Central memory CD4(+) and CD8(+) T-cell frequencies exhibited a positive correlation with fasting blood glucose and glycated haemoglobin A1c levels, whereas the frequencies of naive and effector memory or effector CD4(+) and CD8(+) T cells exhibited a negative correlation. However, the frequencies of CD4(+) and CD8(+) T-cell subsets in individuals with PTB exhibited no significant relationship with bacterial burdens. Finally, although minor alterations in the T-cell subset compartment were observed at 2 months of treatment, significantly decreased frequencies of central memory and significantly enhanced frequencies of naive CD4(+) and CD8(+) T cells were observed at the completion of treatment. Our data reveal a profound effect of coexistent diabetes on the altered frequencies of central memory, effector memory and naive T cells and its normalization following therapy.

BCR signaling inhibitors differ in their ability to overcome Mcl-1–mediated resistance of CLL B cells to ABT-199

BCR signals induce ABT-199 resistance in CLL cells by upregulating Mcl-1. SYK inhibitors prevent BCR-mediated Mcl-1 induction more effectively than BTK or PI3Kδ inhibitors.

Role of the tumor microenvironment in regulating apoptosis and cancer progression

Apoptosis is a gene-directed program that is engaged to efficiently eliminate dysfunctional cells. Evasion of apoptosis may be an important gate to tumor initiation and therapy resistance. Like any other developmental program, apoptosis can be disrupted by several genetic aberrations driving malignant cells into an uncontrolled progression and survival. For its sustained growth, cancer develops in a complex environment, which provides survival signals and rescues malignant cells from apoptosis. Recent studies have clearly shown a wide interaction between tumor cells and their microenvironment, confirming the influence of the surrounding cells on tumor expansion and invasion. These non-malignant cells not only intensify tumor cells growth but also upgrade the process of metastasis. The strong crosstalk between malignant cells and a reactive microenvironment is mediated by soluble chemokines and cytokines, which act on tumor cells through surface receptors. Disturbing the microenvironment signaling might be an encouraging approach for patient's treatment. Therefore, the ultimate knowledge of "tumor-microenvironment" interactions facilitates the identification of novel therapeutic procedures that mobilize cancer cells from their supportive cells. This review focuses on cancer progression mediated by the dysfunction of apoptosis and by the fundamental relationship between tumor and reactive cells. New insights and valuable targets for cancer prevention and therapy are also presented.

Targeting glutamine metabolism in multiple myeloma enhances BIM binding to BCL-2 eliciting synthetic lethality to venetoclax

Multiple myeloma (MM) is a plasma cell malignancy that is largely incurable due to development of resistance to therapy-elicited cell death. Nutrients are intricately connected to maintenance of cellular viability in part by inhibition of apoptosis. We were interested to determine if examination of metabolic regulation of BCL-2 proteins may provide insight on alternative routes to engage apoptosis. MM cells are reliant on glucose and glutamine and withdrawal of either nutrient is associated with varying levels of apoptosis. We and others have demonstrated that glucose maintains levels of key resistance-promoting BCL-2 family member, myeloid cell leukemic factor 1 (MCL-1). Cells continuing to survive in the absence of glucose or glutamine were found to maintain expression of MCL-1 but importantly induce pro-apoptotic BIM expression. One potential mechanism for continued survival despite induction of BIM could be due to binding and sequestration of BIM to alternate pro-survival BCL-2 members. Our investigation revealed that cells surviving glutamine withdrawal in particular, enhance expression and binding of BIM to BCL-2, consequently sensitizing these cells to the BH3 mimetic venetoclax. Glutamine deprivation-driven sensitization to venetoclax can be reversed by metabolic supplementation with TCA cycle intermediate α-ketoglutarate. Inhibition of glucose metabolism with the GLUT4 inhibitor ritonavir elicits variable cytotoxicity in MM that is marginally enhanced with venetoclax treatment, however, targeting glutamine metabolism with 6-diazo-5-oxo-l-norleucine uniformly sensitized MM cell lines and relapse/refractory patient samples to venetoclax. Our studies reveal a potent therapeutic strategy of metabolically driven synthetic lethality involving targeting glutamine metabolism for sensitization to venetoclax in MM.

Elevated HbA(1c) levels and the accumulation of differentiated T cells in CMV(+) individuals

AIMS/HYPOTHESIS

Biological ageing of the immune system, or immunosenescence, predicts poor health and increased mortality. A hallmark of immunosenescence is the accumulation of differentiated cytotoxic T cells (CD27(-)CD45RA(+/-); or dCTLs), partially driven by infection with the cytomegalovirus (CMV). Immune impairments reminiscent of immunosenescence are also observed in hyperglycaemia, and in vitro studies have illustrated mechanisms by which elevated glucose can lead to increased dCTLs. This study explored associations between glucose dysregulation and markers of immunosenescence in CMV(+) and CMV(-) individuals.

METHODS

A cross-sectional sample of participants from an occupational cohort study (n = 1,103, mean age 40 years, 88% male) were assessed for HbA(1c) and fasting glucose levels, diabetes, cardiovascular risk factors (e.g. lipids), numbers of circulating effector memory (EM; CD27(-)CD45RA(-)) and CD45RA re-expressing effector memory (EMRA; CD27(-)CD45RA(+)) T cells, and CMV infection status. Self-report and physical examination assessed anthropometric, sociodemographic and lifestyle factors.

RESULTS

Among CMV(+) individuals (n = 400), elevated HbA(1c) was associated with increased numbers of EM (B = 2.75, p < 0.01) and EMRA (B = 2.90, p < 0.01) T cells, which was robust to adjustment for age, sex, sociodemographic variables and lifestyle factors. Elevated EM T cells were also positively associated with total cholesterol (B = 0.04, p < 0.05) after applying similar adjustments. No associations were observed in CMV(-) individuals.

CONCLUSIONS/INTERPRETATION

The present study identified consistent associations of unfavourable glucose and lipid profiles with accumulation of dCTLs in CMV(+) individuals. These results provide evidence that the impact of metabolic risk factors on immunity and health can be co-determined by infectious factors, and provide a novel pathway linking metabolic risk factors with accelerated immunosenescence.

Mcl-1 downregulation leads to the heightened sensitivity exhibited by BCR-ABL positive ALL to induction of energy and ER-stress

BCR-ABL positive (+) acute lymphoblastic leukemia (ALL) accounts for ∼30% of cases of ALL. We recently demonstrated that 2-deoxy-d-glucose (2-DG), a dual energy (glycolysis inhibition) and ER-stress (N-linked-glycosylation inhibition) inducer, leads to cell death in ALL via ER-stress/UPR-mediated apoptosis. Among ALL subtypes, BCR-ABL+ ALL cells exhibited the highest sensitivity to 2-DG suggesting BCR-ABL expression may be linked to this increased vulnerability. To confirm the role of BCR-ABL, we constructed a NALM6/BCR-ABL stable cell line and found significant increase in 2-DG-induced apoptosis compared to control. We found that Mcl-1 was downregulated by agents inducing ER-stress and Mcl-1 levels correlated with ALL sensitivity. In addition, we showed that Mcl-1 expression is positively regulated by the MEK/ERK pathway, dependent on BCR-ABL, and further downregulated by combining ER-stressors with TKIs. We determined that energy/ER stressors led to translational repression of Mcl-1 via the AMPK/mTOR and UPR/PERK/eIF2α pathways. Taken together, our data indicate that BCR-ABL+ ALL exhibits heightened sensitivity to induction of energy and ER-stress through inhibition of the MEK/ERK pathway, and translational repression of Mcl-1 expression via AMPK/mTOR and UPR/PERK/eIF2α pathways. This study supports further consideration of strategies combining energy/ER-stress inducers with BCR-ABL TKIs for future clinical translation in BCR-ABL+ ALL patients.

Glycogen synthase kinase 3 regulates cell death and survival signaling in tumor cells under redox stress

Targeting tumor-specific metabolic adaptations is a promising anticancer strategy when tumor defense mechanisms are restrained. Here, we show that redox-modulating drugs including the retinoid N-(4-hydroxyphenyl)retinamide (4HPR), the synthetic triterpenoid bardoxolone (2-cyano-3,12-dioxooleana-1,9(11)-dien-28-oic acid methyl ester), arsenic trioxide (As₂O₃), and phenylethyl isothiocyanate (PEITC), while affecting tumor cell viability, induce sustained Ser9 phosphorylation of the multifunctional kinase glycogen synthase kinase 3β (GSK3β). The antioxidant N-acetylcysteine decreased GSK3β phosphorylation and poly(ADP-ribose) polymerase cleavage induced by 4HPR, As₂O₃, and PEITC, implicating oxidative stress in these effects. GSK3β phosphorylation was associated with up-regulation of antioxidant enzymes, in particular heme oxygenase-1 (HO-1), and transient elevation of intracellular glutathione (GSH) in cells surviving acute stress, before occurrence of irreversible damage and death. Genetic inactivation of GSK3β or transfection with the non-phosphorylatable GSK3β-S9A mutant inhibited HO-1 induction under redox stress, while tumor cells resistant to 4HPR exhibited increased GSK3β phosphorylation, HO-1 expression, and GSH levels. The above-listed findings are consistent with a role for sustained GSK3β phosphorylation in a signaling network activating antioxidant effector mechanisms during oxidoreductive stress. These data underlie the importance of combination regimens of antitumor redox drugs with inhibitors of survival signaling to improve control of tumor development and progression and overcome chemoresistance.

PGC-1α is responsible for survival of multiple myeloma cells under hyperglycemia and chemotherapy

The association between hyperglycemia and outcomes during chemotherapy has been reported in several tumors, including multiple myeloma (MM). However, the underlying mechanism of how hyperglycemia affects the survival of MM cells during chemotherapy remain to be elucidated. MM cells were cultured in 10 mM glucose with or without chemotherapeutic agents. Following treatment of MM cells with dexamethasone or bortezomib, an MTT assay was used to evaluate the toxicity of dexamethasone or bortezomib on cell proliferation, and changes of reactive oxygen species (ROS) level were detected by flow cytometry (FCM) analysis. Small interference RNA (siRNA) was applied to inhibit the expression of peroxisome proliferator-activated receptor γ coactivator-1α (PGC-1α). Expressions of PGC-1α and antioxidant factors such as superoxide dismutase 2 (SOD‑2), glutathione peroxidase 1 (GPX-1), and catalase (CAT) were measured by RT-PCR prior to and following treatment. The results showed that the level of PGC-1α in MM cells cultured in high-glucose medium was upregulated prior to and following treatment of chemotherapeutic agents, and these cells showed less fold-change of ROS after insult of drugs, when compared to the control. Genes encoding antioxidant factors such as SOD-2 and CAT were also upregulated. Inhibition of PGC-1α enhanced the toxicity of antitumor agents, associated with reduced expression of antioxidant factors, and elevated level of ROS. The present findings suggested that hyperglycemia may influence the anticancer effect of chemotherapeutic agents in MM by upregulating the expression of PGC-1α and associated antioxidant factors. Inhibition of PGC-1α or control of hyperglycemia may be beneficial in improving the efficacy of chemotherapy in MM patients with diabetes.

Pyruvate kinase M2 regulates apoptosis of intestinal epithelial cells in Crohn's disease

BACKGROUND

Pyruvate kinase M2 (PKM2), a key glycolytic enzyme, is involved in multiple cellular processes including apoptosis. Recently increased fecal PKM2 has been found in Crohn's disease (CD), but little is known regarding its function in the pathophysiology of the disease.

AIM

The intestinal expression of PKM2 and its involvement in CD was investigated.

METHODS

Pyruvate kinase M2 expression in mucosal biopsies from patients with CD and normal controls was detected by immunohistochemistry. A murine model of colitis induced by trinitrobenzenesulphonic acid (TNBS) was established and expression of PKM2, B cell lymphoma-extra large (Bcl-xl), active caspase-3 as well as cleaved poly (ADP-ribose) polymerase (PARP) was examined for association of PKM2 with intestinal epithelial cell (IEC) apoptosis. Furthermore, we treated human IEC line HT-29 by tumor necrosis factor-α (TNF-α) and used RNA interference to analyze the role of PKM2 in IEC apoptosis.

RESULTS

Intestinal expression of PKM2 was higher in patients with CD compared with normal controls mainly locating in IECs. In TNBS-induced colitis, up-regulation of PKM2 was accompanied by the elevated expression of Bcl-xl, active caspase-3, and cleaved PARP. PKM2 was co-localized with active caspase-3 in IECs marked by E-cadherin, suggesting its role in IEC apoptosis. Expression of PKM2 and Bcl-xl in TNF-α-induced HT-29 cells was increased, while TNF-α had no effect on cellular localization of PKM2. Furthermore, knockdown of PKM2 by siRNA could inhibit expression of Bcl-xl but enhance apoptosis in TNF-α-treated HT-29 cells.

CONCLUSION

The up-regulation of PKM2 might protect IECs against apoptosis possibly through Bcl-xl in CD, indicating its important role in the pathophysiology of CD.