NAMPT is the cellular target of STF-31-like small-molecule probes

The interplay between the tumor microenvironment and tumor-derived small extracellular vesicles in cancer development and therapeutic response

The tumor microenvironment (TME) plays an essential role in tumor cell survival by profoundly influencing their proliferation, metastasis, immune evasion, and resistance to treatment. Extracellular vesicles (EVs) are small particles released by all cell types and often reflect the state of their parental cells and modulate other cells' functions through the various cargo they transport. Tumor-derived small EVs (TDSEVs) can transport specific proteins, nucleic acids and lipids tailored to propagate tumor signals and establish a favorable TME. Thus, the TME's biological characteristics can affect TDSEV heterogeneity, and this interplay can amplify tumor growth, dissemination, and resistance to therapy. This review discusses the interplay between TME and TDSEVs based on their biological characteristics and summarizes strategies for targeting cancer cells. Additionally, it reviews the current issues and challenges in this field to offer fresh insights into comprehending tumor development mechanisms and exploring innovative clinical applications.

Oxygen-Dependent Interactions between the Ruthenium Cage and the Photoreleased Inhibitor in NAMPT-Targeted Photoactivated Chemotherapy

Photoactivated chemotherapy agents form a new branch of physically targeted anticancer agents with potentially lower systemic side effects for patients. On the other hand, limited information exists on the intracellular interactions between the photoreleased metal cage and the photoreleased anticancer inhibitor. In this work, we report a new biological study of the known photoactivated compound Ru-STF31 in the glioblastoma cancer cell line, U87MG. Ru-STF31 targets nicotinamide phosphoribosyltransferase (NAMPT), an enzyme overexpressed in U87MG. Ru-STF31 is activated by red light irradiation and releases two photoproducts: the ruthenium cage and the cytotoxic inhibitor STF31. This study shows that Ru-STF31 can significantly decrease intracellular NAD+ levels in both normoxic (21% O2) and hypoxic (1% O2) U87MG cells. Strikingly, NAD+ depletion by light activation of Ru-STF31 in hypoxic U87MG cells could not be rescued by the addition of extracellular NAD+. Our data suggest an oxygen-dependent active role of the ruthenium photocage released by light activation.

Emerging roles of long noncoding RNAs in enzymes related intracellular metabolic pathways in cancer biology

Metabolic reprogramming plays critical roles in the development and progression of tumor by providing cancer cells with a sufficient supply of nutrients and other factors needed for fast-proliferating. Emerging evidence indicates that long noncoding RNAs (lncRNAs) are involved in the initiation of metastasis via regulating the metabolic reprogramming in various cancers. In this paper, we aim to summarize that lncRNAs could participate in intracellular nutrient metabolism including glucose, amino acid, lipid, and nucleotide, regardless of whether lncRNAs have tumor-promoting or tumor-suppressor function. Meanwhile, modulation of lncRNAs in glucose metabolic enzymes in glycolysis, pentose phosphate pathway and tricarboxylic acid cycle (TCA) in cancer is reviewed. We also discuss therapeutic strategies targeted at interfering with enzyme activity to decrease the utilization of glucoses, amino acid, nucleotide acid and lipid in tumor cells. This review focuses on our current understanding of lncRNAs participating in cancer cell metabolic reprogramming, paving the way for further investigation into the combination of such approaches with existing anti-cancer therapies.

GLUT and HK: Two primary and essential key players in tumor glycolysis

Cancer cells reprogram their metabolism to become "glycolysis-dominant," which enables them to meet their energy and macromolecule needs and enhancing their rate of survival. This glycolytic-dominancy is known as the "Warburg effect", a significant factor in the growth and invasion of malignant tumors. Many studies confirmed that members of the GLUT family, specifically HK-II from the HK family play a pivotal role in the Warburg effect, and are closely associated with glucose transportation followed by glucose metabolism in cancer cells. Overexpression of GLUTs and HK-II correlates with aggressive tumor behaviour and tumor microenvironment making them attractive therapeutic targets. Several studies have proven that the regulation of GLUTs and HK-II expression improves the treatment outcome for various tumors. Therefore, small molecule inhibitors targeting GLUT and HK-II show promise in sensitizing cancer cells to treatment, either alone or in combination with existing therapies including chemotherapy, radiotherapy, immunotherapy, and photodynamic therapy. Despite existing therapies, viable methods to target the glycolysis of cancer cells are currently lacking to increase the effectiveness of cancer treatment. This review explores the current understanding of GLUT and HK-II in cancer metabolism, recent inhibitor developments, and strategies for future drug development, offering insights into improving cancer treatment efficacy.

The Illustration of Altered Glucose Dependency in Drug-Resistant Cancer Cells

A chemotherapeutic approach is crucial in malignancy management, which is often challenging due to the development of chemoresistance. Over time, chemo-resistant cancer cells rapidly repopulate and metastasize, increasing the recurrence rate in cancer patients. Targeting these destined cancer cells is more troublesome for clinicians, as they share biology and molecular cross-talks with normal cells. However, the recent insights into the metabolic profiles of chemo-resistant cancer cells surprisingly illustrated the activation of distinct pathways compared with chemo-sensitive or primary cancer cells. These distinct metabolic dynamics are vital and contribute to the shift from chemo-sensitivity to chemo-resistance in cancer. This review will discuss the important metabolic alterations in cancer cells that lead to drug resistance.

Small molecule inhibitors for cancer metabolism: promising prospects to be explored

BACKGROUND

Abnormal metabolism is the main hallmark of cancer, and cancer metabolism plays an important role in tumorigenesis, metastasis, and drug resistance. Therefore, studying the changes of tumor metabolic pathways is beneficial to find targets for the treatment of cancer diseases. The success of metabolism-targeted chemotherapy suggests that cancer metabolism research will provide potential new targets for the treatment of malignant tumors.

PURPOSE

The aim of this study was to systemically review recent research findings on targeted inhibitors of tumor metabolism. In addition, we summarized new insights into tumor metabolic reprogramming and discussed how to guide the exploration of new strategies for cancer-targeted therapy.

CONCLUSION

Cancer cells have shown various altered metabolic pathways, providing sufficient fuel for their survival. The combination of these pathways is considered to be a more useful method for screening multilateral pathways. Better understanding of the clinical research progress of small molecule inhibitors of potential targets of tumor metabolism will help to explore more effective cancer treatment strategies.

Therapeutic strategies targeting metabolic characteristics of cancer cells

Metabolic reprogramming is one of the important characteristics of cancer and is a key process leading to malignant proliferation, tumor development and treatment resistance. A variety of therapeutic drugs targeting metabolic reaction enzymes, transport receptors, and special metabolic processes have been developed. In this review, we investigate the characteristics of multiple metabolic changes in cancer cells, including glycolytic pathways, lipid metabolism, and glutamine metabolism changes, describe how these changes promote tumor development and tumor resistance, and summarize the progress and challenges of therapeutic strategies targeting various links of tumor metabolism in combination with current study data.

NAD pool as an antitumor target against cancer stem cells in head and neck cancer

Head and neck squamous cell carcinoma (HNSCC) is a heterogeneous group of tumors that affect different anatomical locations. Despite this heterogeneity, HNSCC treatment depends on the anatomical location, TNM stage and resectability of the tumor. Classical chemotherapy is based on platinum-derived drugs (cisplatin, carboplatin and oxaliplatin), taxanes (docetaxel, paclitaxel) and 5-fluorouracil¹. Despite advances in HNSCC treatment, the rate of tumor recurrence and patient mortality remain high. Therefore, the search for new prognostic identifiers and treatments targeting therapy-resistant tumor cells is vital. Our work demonstrates that there are different subgroups with high phenotypic plasticity within the CSC population in HNSCC. CD10, CD184, and CD166 may identify some of these CSC subpopulations with NAMPT as a common metabolic gene for the resilient cells of these subpopulations. We observed that NAMPT reduction causes a decrease in tumorigenic and stemness properties, migration capacity and CSC phenotype through NAD pool depletion. However, NAMPT-inhibited cells can acquire resistance by activating the NAPRT enzyme of the Preiss-Handler pathway. We observed that coadministration of the NAMPT inhibitor with the NAPRT inhibitor cooperated inhibiting tumor growth. The use of an NAPRT inhibitor as an adjuvant improved NAMPT inhibitor efficacy and reduced the dose and toxicity of these inhibitors. Therefore, it seems that the reduction in the NAD pool could have efficacy in tumor therapy. This was confirmed by in vitro assays supplying the cells with products of inhibited enzymes (NA, NMN or NAD) and restoring their tumorigenic and stemness properties. In conclusion, the coinhibition of NAMPT and NAPRT improved the efficacy of antitumor treatment, indicating that the reduction in the NAD pool is important to prevent tumor growth.

Nutrient transporters: connecting cancer metabolism to therapeutic opportunities

Cancer cells rely on certain extracellular nutrients to sustain their metabolism and growth. Solute carrier (SLC) transporters enable cells to acquire extracellular nutrients or shuttle intracellular nutrients across organelles. However, the function of many SLC transporters in cancer is unknown. Determining the key SLC transporters promoting cancer growth could reveal important therapeutic opportunities. Here we summarize recent findings and knowledge gaps on SLC transporters in cancer. We highlight existing inhibitors for studying these transporters, clinical trials on treating cancer by blocking transporters, and compensatory transporters used by cancer cells to evade treatment. We propose targeting transporters simultaneously or in combination with targeted therapy or immunotherapy as alternative strategies for effective cancer therapy.

Targeting of Glucose Transport and the NAD Pathway in Neuroendocrine Tumor (NET) Cells Reveals New Treatment Options

(1) Background: the potency of drugs that interfere with glucose metabolism, i.e., glucose transporters (GLUT) and nicotinamide phosphoribosyltransferase (NAMPT) was analyzed in neuroendocrine tumor (NET, BON-1, and QPG-1 cells) and small cell lung cancer (SCLC, GLC-2, and GLC-36 cells) tumor cell lines. (2) Methods: the proliferation and survival rate of tumor cells was significantly affected by the GLUT-inhibitors fasentin and WZB1127, as well as by the NAMPT inhibitors GMX1778 and STF-31. (3) Results: none of the NET cell lines that were treated with NAMPT inhibitors could be rescued with nicotinic acid (usage of the Preiss-Handler salvage pathway), although NAPRT expression could be detected in two NET cell lines. We finally analyzed the specificity of GMX1778 and STF-31 in NET cells in glucose uptake experiments. As previously shown for STF-31 in a panel NET-excluding tumor cell lines, both drugs specifically inhibited glucose uptake at higher (50 μM), but not at lower (5 μM) concentrations. (4) Conclusions: our data suggest that GLUT and especially NAMPT inhibitors are potential candidates for the treatment of NET tumors.

The release of FB1-induced heterophil extracellular traps in chicken is dependent on autophagy and glycolysis

Fumonisin B₁ (FB₁), a worldwide contaminating mycotoxin produced by Fusarium, poses a great threat to the poultry industry. It was reported that extracellular traps could be induced by FB₁ efficiently in chickens. However, the relevance of autophagy and glycolysis in FB₁-triggered heterophil extracellular trap (HET) formation is unclear. In this study, immunostaining revealed that FB₁-induced HETs structures were composed of DNA coated with histones H3, and elastase, and that heterophils underwent LC3B-related autophagosome formation assembly driven by FB₁. Western blotting showed that FB₁ downregulated the phosphorylated phosphoinositide 3-kinase3-kinase (PI3K)/protein kinase B (AKT)/mechanistic target of rapamycin complex 1 (mTORC1) axis and raised the AMP-activated kinase α (AMPKα) activation protein. Furthermore, rapamycin- and 3-Methyladenine (3-MA)-treatments modulated FB₁-triggered HET formation according to the pharmacological analysis. Further studies on energy metabolism showed that glucose/lactate transport and glycolysis inhibitors abated FB₁-induced HETs. These results showed that FB₁-induced HET formation might interact with the autophagy process and relied on glucose/monocarboxylic acid transporter 1 (MCT1) and glycolysis, reflecting chicken's early innate immune responses against FB₁ intake.

An appraisal of the current status of inhibition of glucose transporters as an emerging antineoplastic approach: Promising potential of new pan-GLUT inhibitors

Neoplastic cells displayed altered metabolism with accelerated glycolysis. Therefore, these cells need a mammoth supply of glucose for which they display an upregulated expression of various glucose transporters (GLUT). Thus, novel antineoplastic strategies focus on inhibiting GLUT to intersect the glycolytic lifeline of cancer cells. This review focuses on the current status of various GLUT inhibition scenarios. The GLUT inhibitors belong to both natural and synthetic small inhibitory molecules category. As neoplastic cells express multiple GLUT isoforms, it is necessary to use pan-GLUT inhibitors. Nevertheless, it is also necessary that such pan-GLUT inhibitors exert their action at a low concentration so that normal healthy cells are left unharmed and minimal injury is caused to the other vital organs and systems of the body. Moreover, approaches are also emerging from combining GLUT inhibitors with other chemotherapeutic agents to potentiate the antineoplastic action. A new pan-GLUT inhibitor named glutor, a piperazine-one derivative, has shown a potent antineoplastic action owing to its inhibitory action exerted at nanomolar concentrations. The review discusses the merits and limitations of the existing GLUT inhibitory approach with possible future outcomes.

Structural aspects of the glucose and monocarboxylate transporters involved in the Warburg effect

Cancer cells shift their glucose catabolism from aerobic respiration to lactic fermentation even in the presence of oxygen, and this is known as the "Warburg effect". To accommodate the high glucose demands and to avoid lactate accumulation, the expression levels of human glucose transporters (GLUTs) and human monocarboxylate transporters (MCTs) are elevated to maintain metabolic homeostasis. Therefore, inhibition of GLUTs and/or MCTs provides potential therapeutic strategies for cancer treatment. Here, we summarize recent advances in the structural characterization of GLUTs and MCTs, providing a comprehensive understanding of their transport and inhibition mechanisms to facilitate further development of anticancer therapies.

Nicotinamide Adenine Dinucleotide (NAD) Metabolism as a Relevant Target in Cancer

NAD+ is an important metabolite in cell homeostasis that acts as an essential cofactor in oxidation–reduction (redox) reactions in various energy production processes, such as the Krebs cycle, fatty acid oxidation, glycolysis and serine biosynthesis. Furthermore, high NAD+ levels are required since they also participate in many other nonredox molecular processes, such as DNA repair, posttranslational modifications, cell signalling, senescence, inflammatory responses and apoptosis. In these nonredox reactions, NAD+ is an ADP-ribose donor for enzymes such as sirtuins (SIRTs), poly-(ADP-ribose) polymerases (PARPs) and cyclic ADP-ribose (cADPRs). Therefore, to meet both redox and nonredox NAD+ demands, tumour cells must maintain high NAD+ levels, enhancing their synthesis mainly through the salvage pathway. NAMPT, the rate-limiting enzyme of this pathway, has been identified as an oncogene in some cancer types. Thus, NAMPT has been proposed as a suitable target for cancer therapy. NAMPT inhibition causes the depletion of NAD+ content in the cell, leading to the inhibition of ATP synthesis. This effect can cause a decrease in tumour cell proliferation and cell death, mainly by apoptosis. Therefore, in recent years, many specific inhibitors of NAMPT have been developed, and some of them are currently in clinical trials. Here we review the NAD metabolism as a cancer therapy target.

New Developments in T Cell Immunometabolism and Therapeutic Implications for Type 1 Diabetes

Type 1 diabetes (T1D) is an autoimmune disease mediated by T cells and is becoming a serious public health threat. Despite the increasing incidence rate of T1D worldwide, our understanding of why T1D develops and how T cells lose their self-tolerance in this process remain limited. Recent advances in immunometabolism have shown that cellular metabolism plays a fundamental role in shaping T cell responses. T cell activation and proliferation are supported by metabolic reprogramming to meet the increased energy and biomass demand, and deregulation in immune metabolism can lead to autoimmune disorders. Specific metabolic pathways and factors have been investigated to rectify known deficiencies in several autoimmune diseases, including T1D. Most therapeutic strategies have concentrated on aerobic glycolysis to limit T cell responses, whereas glycolysis is the main metabolic pathway for T cell activation and proliferation. The use of metabolic inhibitors, especially glycolysis inhibitors may largely leave T cell function intact but primarily target those autoreactive T cells with hyperactivated metabolism. In this review, we provide an overview of metabolic reprogramming used by T cells, summarize the recent findings of key metabolic pathways and regulators modulating T cell homeostasis, differentiation, and function in the context of T1D, and discuss the opportunities for metabolic intervention to be employed to suppress autoreactive T cells and limit the progression of β-cell destruction.

Targeting cancer metabolism in the era of precision oncology

One hundred years have passed since Warburg discovered alterations in cancer metabolism, more than 70 years since Sidney Farber introduced anti-folates that transformed the treatment of childhood leukaemia, and 20 years since metabolism was linked to oncogenes. However, progress in targeting cancer metabolism therapeutically in the past decade has been limited. Only a few metabolism-based drugs for cancer have been successfully developed, some of which are in - or en route to - clinical trials. Strategies for targeting the intrinsic metabolism of cancer cells often did not account for the metabolism of non-cancer stromal and immune cells, which have pivotal roles in tumour progression and maintenance. By considering immune cell metabolism and the clinical manifestations of inborn errors of metabolism, it may be possible to isolate undesirable off-tumour, on-target effects of metabolic drugs during their development. Hence, the conceptual framework for drug design must consider the metabolic vulnerabilities of non-cancer cells in the tumour immune microenvironment, as well as those of cancer cells. In this Review, we cover the recent developments, notable milestones and setbacks in targeting cancer metabolism, and discuss the way forward for the field.

5-Aminolevulinic acid combined with ferrous iron improves glucose tolerance in high-fat diet-fed mice via upregulation of glucose transporter 1

Decreased mitochondrial metabolism suppresses glucose metabolism, resulting in obesity and diabetes. The present study aimed to investigate mechanisms underlying the 5-aminolevulinic acid (5-ALA) hydrochloride-mediated increase in glucose uptake in high-fat diet (HFD)-fed mice in vivo and C2C12 myotube cells in vitro. C57BL/6N male mice (20 weeks old) were fed either HFD or normal diet (ND) for 4 weeks. A total of five HFD-fed mice were orally administered with 300 mg/kg 5-ALA hydrochloride and 47.1 mg/kg sodium ferrous citrate (SFC; HFD + 5-ALA/SFC), whereas ND and other HFD-fed mice were orally administered with saline. After 4 weeks, these mice were intraperitoneally administered with 2 g/kg glucose and 3.2 mg/kg 2-deoxyglucose (2DG) for intraperitoneal glucose tolerance test (IPGTT) and glucose uptake test. Body weights, plasma glucose levels and the area under the curve of IPGTT were lower in mice treated with HFD + 5-ALA/SFC compared with in those treated with HFD alone. 2DG uptake in the gastrocnemius muscle and heart were more significantly improved in the HFD + 5-ALA/SFC mice compared with the HFD-fed mice. Furthermore, 5-ALA/SFC increased 2DG uptake in C2C12 cells to a similar level to the insulin-treated group. Moreover, it increased glucose transport (GLUT)1 translocation in the plasma membrane by 2.5-fold relative to the controls without affecting GLUT1 expression; however, it had no effect on GLUT4 translocation. Therefore, 5-ALA/SFC enhanced gastrocnemius and cardiac glucose uptake in HFD-fed mice, and upregulated GLUT1 translocation to the plasma membrane, but not GLUT4 in C2C12 myotube cells. Therefore, it could potentially be used as a novel drug for the treatment of diabetes.

Advances in NAD-Lowering Agents for Cancer Treatment

Nicotinamide adenine dinucleotide (NAD) is an essential redox cofactor, but it also acts as a substrate for NAD-consuming enzymes, regulating cellular events such as DNA repair and gene expression. Since such processes are fundamental to support cancer cell survival and proliferation, sustained NAD production is a hallmark of many types of neoplasms. Depleting intratumor NAD levels, mainly through interference with the NAD-biosynthetic machinery, has emerged as a promising anti-cancer strategy. NAD can be generated from tryptophan or nicotinic acid. In addition, the "salvage pathway" of NAD production, which uses nicotinamide, a byproduct of NAD degradation, as a substrate, is also widely active in mammalian cells and appears to be highly exploited by a subset of human cancers. In fact, research has mainly focused on inhibiting the key enzyme of the latter NAD production route, nicotinamide phosphoribosyltransferase (NAMPT), leading to the identification of numerous inhibitors, including FK866 and CHS-828. Unfortunately, the clinical activity of these agents proved limited, suggesting that the approaches for targeting NAD production in tumors need to be refined. In this contribution, we highlight the recent advancements in this field, including an overview of the NAD-lowering compounds that have been reported so far and the related in vitro and in vivo studies. We also describe the key NAD-producing pathways and their regulation in cancer cells. Finally, we summarize the approaches that have been explored to optimize the therapeutic response to NAMPT inhibitors in cancer.

Conservation of copy number profiles during engraftment and passaging of patient-derived cancer xenografts

Patient-derived xenografts (PDXs) are resected human tumors engrafted into mice for preclinical studies and therapeutic testing. It has been proposed that the mouse host affects tumor evolution during PDX engraftment and propagation, affecting the accuracy of PDX modeling of human cancer. Here, we exhaustively analyze copy number alterations (CNAs) in 1,451 PDX and matched patient tumor (PT) samples from 509 PDX models. CNA inferences based on DNA sequencing and microarray data displayed substantially higher resolution and dynamic range than gene expression-based inferences, and they also showed strong CNA conservation from PTs through late-passage PDXs. CNA recurrence analysis of 130 colorectal and breast PT/PDX-early/PDX-late trios confirmed high-resolution CNA retention. We observed no significant enrichment of cancer-related genes in PDX-specific CNAs across models. Moreover, CNA differences between patient and PDX tumors were comparable to variations in multiregion samples within patients. Our study demonstrates the lack of systematic copy number evolution driven by the PDX mouse host.

Manipulation of Glucose Availability to Boost Cancer Immunotherapies

The orchestration of T cell responses is intimately linked to the execution of metabolic processes, both in homeostasis and disease. In cancer tissues, metabolic alterations that characterize malignant transformation profoundly affect the composition of the immune microenvironment and the accomplishment of an effective anti-tumor response. The growing understanding of the metabolic regulation of immune cell function has shed light on the possibility to manipulate metabolic pathways as a strategy to improve T cell function in cancer. Among others, glucose metabolism through the glycolytic pathway is central in shaping T cell responses and emerges as an ideal target to improve cancer immunotherapy. However, metabolic manipulation requires a deep level of control over side-effects and development of biomarkers of response. Here, we summarize the metabolic control of T cell function and focus on the implications of metabolic manipulation for the design of immunotherapeutic strategies. Integrating our understanding of T cell function and metabolism will hopefully foster the forthcoming development of more effective immunotherapeutic strategies.

The Warburg Effect 97 Years after Its Discovery

The deregulation of the oxidative metabolism in cancer, as shown by the increased aerobic glycolysis and impaired oxidative phosphorylation (Warburg effect), is coordinated by genetic changes leading to the activation of oncogenes and the loss of oncosuppressor genes. The understanding of the metabolic deregulation of cancer cells is necessary to prevent and cure cancer. In this review, we illustrate and comment the principal metabolic and molecular variations of cancer cells, involved in their anomalous behavior, that include modifications of oxidative metabolism, the activation of oncogenes that promote glycolysis and a decrease of oxygen consumption in cancer cells, the genetic susceptibility to cancer, the molecular correlations involved in the metabolic deregulation in cancer, the defective cancer mitochondria, the relationships between the Warburg effect and tumor therapy, and recent studies that reevaluate the Warburg effect. Taken together, these observations indicate that the Warburg effect is an epiphenomenon of the transformation process essential for the development of malignancy.

Structural Basis of Beneficial Design for Effective Nicotinamide Phosphoribosyltransferase Inhibitors

Inhibition of nicotinamide phosphoribosyltransferase (NAMPT) is an attractive therapeutic strategy for targeting cancer metabolism. So far, many potent NAMPT inhibitors have been developed and shown to bind to two unique tunnel-shaped cavities existing adjacent to each active site of a NAMPT homodimer. However, cytotoxicities and resistances to NAMPT inhibitors have become apparent. Therefore, there remains an urgent need to develop effective and safe NAMPT inhibitors. Thus, we designed and synthesized two close structural analogues of NAMPT inhibitors, azaindole-piperidine (3a)- and azaindole-piperazine (3b)-motif compounds, which were modified from the well-known NAMPT inhibitor FK866 (1). Notably, 3a displayed considerably stronger enzyme inhibitory activity and cellular potency than did 3b and 1. The main reason for this phenomenon was revealed to be due to apparent electronic repulsion between the replaced nitrogen atom (N1) of piperazine in 3b and the Nδ atom of His191 in NAMPT by our in silico binding mode analyses. Indeed, 3b had a lower binding affinity score than did 3a and 1, although these inhibitors took similar stable chair conformations in the tunnel region. Taken together, these observations indicate that the electrostatic enthalpy potential rather than entropy effects inside the tunnel cavity has a significant impact on the different binding affinity of 3a from that of 3b in the disparate enzymatic and cellular potencies. Thus, it is better to avoid or minimize interactions with His191 in designing further effective NAMPT inhibitors.

The NAD+ Salvage Pathway Supports PHGDH-Driven Serine Biosynthesis

NAD⁺ is a key metabolic redox cofactor that is regenerated from nicotinamide through the NAD⁺ salvage pathway. Here, we find that inhibiting the NAD⁺ salvage pathway depletes serine biosynthesis from glucose by impeding the NAD⁺-dependent protein, 3-phosphoglycerate dehydrogenase (PHGDH). Importantly, we find that PHGDH^high breast cancer cell lines are exquisitely sensitive to inhibition of the NAD⁺ salvage pathway. Further, we find that PHGDH protein levels and those of the rate-limiting enzyme of NAD⁺ salvage, NAMPT, correlate in ER-negative, basal-like breast cancers. Although NAD⁺ salvage pathway inhibitors are actively being pursued in cancer treatment, their efficacy has been poor, and our findings suggest that they may be effective for PHGDH-dependent cancers.

A new chemotype with promise against Trypanosoma cruzi

Pyridyl benzamide 2 is a potent inhibitor of Trypanosoma cruzi, but not other protozoan parasites, and had a selectivity-index of ≥10. The initial structure-activity relationship (SAR) indicates that benzamide and sulfonamide functional groups, and N-methylpiperazine and sterically unhindered 3-pyridyl substructures are required for high activity against T. cruzi. Compound 2 and its active analogs had low to moderate metabolic stabilities in human and mouse liver microsomes.

A synthetic lethal drug combination mimics glucose deprivation-induced cancer cell death in the presence of glucose

Metabolic reprogramming in cancer cells can increase their dependence on metabolic substrates such as glucose. As such, the vulnerability of cancer cells to glucose deprivation creates an attractive opportunity for therapeutic intervention. Because it is not possible to starve tumors of glucose in vivo, here we sought to identify the mechanisms in glucose deprivation-induced cancer cell death and then designed inhibitor combinations to mimic glucose deprivation-induced cell death. Using metabolomic profiling, we found that cells undergoing glucose deprivation-induced cell death exhibited dramatic accumulation of intracellular l-cysteine and its oxidized dimer, l-cystine, and depletion of the antioxidant GSH. Building on this observation, we show that glucose deprivation-induced cell death is driven not by the lack of glucose, but rather by l-cystine import. Following glucose deprivation, the import of l-cystine and its subsequent reduction to l-cysteine depleted both NADPH and GSH pools, thereby allowing toxic accumulation of reactive oxygen species. Consistent with this model, we found that the glutamate/cystine antiporter (xCT) is required for increased sensitivity to glucose deprivation. We searched for glycolytic enzymes whose expression is essential for the survival of cancer cells with high xCT expression and identified glucose transporter type 1 (GLUT1). Testing a drug combination that co-targeted GLUT1 and GSH synthesis, we found that this combination induces synthetic lethal cell death in high xCT-expressing cell lines susceptible to glucose deprivation. These results indicate that co-targeting GLUT1 and GSH synthesis may offer a potential therapeutic approach for targeting tumors dependent on glucose for survival.

Pharmacological Targeting of GLUT1 to Control Autoreactive T Cell Responses

An increasing body of evidence indicates that bio-energetic metabolism of T cells can be manipulated to control T cell responses. This potentially finds a field of application in the control of the T cell responses in autoimmune diseases, including in type 1 diabetes (T1D). Of the possible metabolic targets, Glut1 gained considerable interest because of its pivotal role in glucose uptake to fuel glycolysis in activated T cells, and the recent development of a novel class of small molecules that act as selective inhibitor of Glut1. We believe we can foresee a possible application of pharmacological Glut1 blockade approach to control autoreactive T cells that destroy insulin producing beta cells. However, Glut1 is expressed in a broad range of cells in the body and off-target and side effect are possible complications. Moreover, the duration of the treatment and the age of patients are critical aspects that need to be addressed to reduce toxicity. In this paper, we will review recent literature to determine whether it is possible to design a pharmacological Glut1 blocking strategy and how to apply this to autoimmunity in T1D.

Erianin alleviates diabetic retinopathy by reducing retinal inflammation initiated by microglial cells via inhibiting hyperglycemia-mediated ERK1/2-NF-κB signaling pathway

Blood-retinal barrier (BRB) breakdown is a typical event in the early stage of diabetic retinopathy (DR). This study aims to elucidate the protection of erianin, a natural compound isolated from Dendrobium chrysotoxum Lindl, against DR development. Erianin alleviated BRB breakdown and rescued the reduced claudin1 and occludin expression in retinas from streptozotocin-induced diabetic mice. Erianin reduced microglial activation, ERK1/2 phosphorylation, NF-κB transcriptional activation, and the elevated TNF-α expression both in vitro and in vivo. ERK1/2 inhibitor U0126 abrogated NF-κB activation in d-glucose-treated BV2 cells. Erianin reduced cellular glucose uptake, and molecular docking analysis indicated the potential interaction of erianin with glucose transporter (GLUT)1. GLUT1 inhibitor (STF31) reduced the activation of the ERK1/2-NF-κB signaling pathway. Coculture with d-glucose-stimulated microglial BV2 cells and with TNF-α stimulation both induced inner BRB and outer BRB damage in human retinal endothelial cells and APRE19 cells, but erianin improved all these damages. In summary, erianin attenuated BRB breakdown during DR development by inhibiting microglia-triggered retinal inflammation via reducing cellular glucose uptake and abrogating the subsequent activation of the downstream ERK1/2-NF-κB pathway. Moreover, erianin also alleviated BRB damage induced by TNF-α released from the activated microglia.-Zhang, T., Ouyang, H., Mei, X., Lu, B., Yu, Z., Chen, K., Wang, Z., Ji, L. Erianin alleviates diabetic retinopathy by reducing retinal inflammation initiated by microglial cells via inhibiting hyperglycemia-mediated ERK1/2-NF-κB signaling pathway.

Targeting cancer metabolism through synthetic lethality-based combinatorial treatment strategies

PURPOSE OF REVIEW

Targeting cancer metabolism for therapy has received much attention over the last decade with various small molecule inhibitors entering clinical trials. The present review highlights the latest strategies to target glucose and glutamine metabolism for cancer therapy with a particular emphasis on novel combinatorial treatment approaches.

RECENT FINDINGS

Inhibitors of glucose, lactate, and glutamine transport and the ensuing metabolism are in preclinical to clinical trial stages of investigation. Recent advances in our understanding of cell-intrinsic and cell-extrinsic factors that dictate dependence on these targets have informed the development of rational, synthetic lethality-based strategies to exploit these metabolic vulnerabilities.

SUMMARY

Cancer cells exhibit a number of metabolic alterations with functional consequences beyond that of sustaining cellular energetics and biosynthesis. Elucidating context-specific metabolic dependencies and their connections to oncogenic signaling and epigenetic programs in tumor cells represents a promising approach to identify new metabolic drug targets for cancer therapy.

Computational Analyses Connect Small-Molecule Sensitivity to Cellular Features Using Large Panels of Cancer Cell Lines

We recently pioneered several analyses of small-molecule sensitivity data collected from large-scale perturbation of hundreds of cancer cell lines with hundreds of small molecules, with cell viability measured as a readout of compound sensitivity. We performed these studies using cancer cell lines previously annotated with cellular, genomic, and basal gene-expression features. By combining small-molecule sensitivity data with these other datasets, we identified new candidate biomarkers of sensitivity, gained insights into small-molecule mechanisms of action, and proposed candidate hypotheses for cancer dependencies (including candidate combination therapies). Nevertheless, given the size of these datasets, we expect that many connections between cellular features and small-molecule sensitivity remain underexplored. In this chapter, we provide a step-by-step account of foundational data-analysis methods underlying our published studies, including working MATLAB code applied to our own public datasets. These procedures will allow others to repeat analyses of our data with new parameters, in additional contexts, and to adapt our procedures to their own datasets.

Ovarian Cancer Relies on Glucose Transporter 1 to Fuel Glycolysis and Growth: Anti-Tumor Activity of BAY-876

The recent progresses in understanding of cancer glycolytic phenotype have offered new strategies to manage ovarian cancer and other malignancies. However, therapeutic targeting of glycolysis to treat cancer remains unsuccessful due to complex mechanisms of tumor glycolysis and the lack of selective, potent and safe glycolytic inhibitors. Recently, BAY-876 was identified as a new-generation inhibitor of glucose transporter 1 (GLUT1), a GLUT isoform commonly overexpressed but functionally poorly defined in ovarian cancer. Notably, BAY-876 has not been evaluated in any cell or preclinical animal models since its discovery. We herein took advantage of BAY-876 and molecular approaches to study GLUT1 regulation, targetability, and functional relevance to cancer glycolysis. The anti-tumor activity of BAY-876 was evaluated with ovarian cancer cell line- and patient-derived xenograft (PDX) models. Our results show that inhibition of GLUT1 is sufficient to block basal and stress-regulated glycolysis, and anchorage-dependent and independent growth of ovarian cancer cells. BAY-876 dramatically inhibits tumorigenicity of both cell line-derived xenografts and PDXs. These studies provide direct evidence that GLUT1 is causally linked to the glycolytic phenotype in ovarian cancer. BAY-876 is a potent blocker of GLUT1 activity, glycolytic metabolism and ovarian cancer growth, holding promise as a novel glycolysis-targeted anti-cancer agent.

Genomic and tumor biological aspects of the anticancer nicotinamide phosphoribosyltransferase inhibitor FK866 in resistant human colorectal cancer cells

Cancer cells' resistance to drugs remains an important problem affecting cancer treatment strategies. We previously studied the nicotinamide phosphoribosyltransferase (NAMPT) inhibitor FK866's resistance mechanisms in the human colorectal cancer HCT116 cells. We established an acquired FK866-resistant cell line, HCT116R^FK866. In this study, we investigated gene mutations in parental HCT116 and HCT116R^FK866 cells using exome sequencing technology. The results indicated cluster genes related to NAD⁺ biosynthesis (including NAMPT), DNA repair, and ATP-binding cassette transporters were differentially altered in these cells. Interestingly, HCT116R^FK866 cells, which are resistant to other class NAMPT inhibitors, were more sensitive to the anticancer 5-fluorouracil and cisplatin and γ-ray irradiation compared to parental HCT116 cells. This higher sensitivity appears to cause a genetic change in the identified gene clusters by resistance to the NAMPT inhibitor FK866. Collectively, these novel findings provide a better understanding of anticancer candidate NAMPT inhibitors with regard to resistance mechanisms and cancer chemotherapy strategies.

NAD Metabolism in Cancer Therapeutics

Cancer cells have a unique energy metabolism for sustaining rapid proliferation. The preference for anaerobic glycolysis under normal oxygen conditions is a unique trait of cancer metabolism and is designated as the Warburg effect. Enhanced glycolysis also supports the generation of nucleotides, amino acids, lipids, and folic acid as the building blocks for cancer cell division. Nicotinamide adenine dinucleotide (NAD) is a co-enzyme that mediates redox reactions in a number of metabolic pathways, including glycolysis. Increased NAD levels enhance glycolysis and fuel cancer cells. In fact, nicotinamide phosphoribosyltransferase (Nampt), a rate-limiting enzyme for NAD synthesis in mammalian cells, is frequently amplified in several cancer cells. In addition, Nampt-specific inhibitors significantly deplete NAD levels and subsequently suppress cancer cell proliferation through inhibition of energy production pathways, such as glycolysis, tricarboxylic acid (TCA) cycle, and oxidative phosphorylation. NAD also serves as a substrate for poly(ADP-ribose) polymerase (PARP), sirtuin, and NAD gylycohydrolase (CD38 and CD157); thus, NAD regulates DNA repair, gene expression, and stress response through these enzymes. Thus, NAD metabolism is implicated in cancer pathogenesis beyond energy metabolism and considered a promising therapeutic target for cancer treatment. In this review, we present recent findings with respect to NAD metabolism and cancer pathogenesis. We also discuss the current and future perspectives regarding the therapeutics that target NAD metabolic pathways.

Glucose transporters in cancer - from tumor cells to the tumor microenvironment

Solute carriers of the glucose transporter (GLUT) family mediate the first step for cellular glucose usage. The upregulation of GLUTs has been reported in numerous cancer types as a result of perturbation of gene expression or protein relocalization or stabilization. Because they enable to sustain the energy demand required by tumor cells for various biochemical programs, they are promising targets for the development of anticancer strategies. Recently, important biological insights have come from the fine crystal structure determination of several GLUTs; these advances will likely catalyze the development of new selective inhibitory compounds. Furthermore, deregulated glucose metabolism of nontumor cells in the tumor mass is beginning to be appreciated and could have major implications for our understanding of how glucose uptake by specific cell types influences the behavior of neighboring cells in the same microenvironment. In this review, we discuss some of the deregulation mechanisms of glucose transporters, their genetic and pharmacological targeting in cancer, and new functions they may have in nontumor cells of the tumor environment or beyond glucose uptake for glycolysis.

A Novel Multiple-Read Screen for Metabolically Active Compounds Based on a Genetically Encoded FRET Sensor for ATP

Both glycolysis and mitochondrial energetics are targets of interest for developing antiproliferative cancer therapeutics. We developed a novel multiple-read assay based on long-term expression in K562 cells of a genetically encoded intramolecular Förster resonance energy transfer sensor for adenosine triphosphate (ATP). The assay, conducted in a fluorescent plate reader, can identify compounds that inhibit oxidative phosphorylation-dependent ATP production, glycolysis, or both after short-term treatment. We screened a National Cancer Institute (NCI) compound library, identifying inhibitors of oxidative phosphorylation-dependent ATP production and glycolysis. Three glycolysis inhibitors blocked hexokinase activity, demonstrating that our assay can serve as the initial step in a workflow to identify compounds that inhibit glycolysis via a defined desired mechanism. Finally, upon reviewing the literature, we found surprisingly little evidence that inhibiting glycolysis with small molecules is antiproliferative. Using NCI data on proliferation of K562 cells, we found that inhibitors of oxidative phosphorylation-dependent ATP production were no more antiproliferative than the overall library, whereas all glycolysis inhibitors were in the top third of most effective antiproliferative compounds. Our results thus present a powerful new way to screen for compounds that affect cellular metabolism and also provide important support for the idea that blocking glycosis is antiproliferative.

Targeting glucose transport and the NAD pathway in tumor cells with STF-31: a re-evaluation

BACKGROUND

Targeting glucose metabolism is a promising way to interfere with tumor cell proliferation and survival. However, controversy exists about the specificity of some glucose metabolism targeting anticancer drugs. Especially the potency of STF-31 has been debated. Here, we aimed to assess the impact of the glucose transporter (GLUT) inhibitors fasentin and WZB117, and the nicotinamide phosphoribosyltransferase (NAMPT) inhibitors GMX1778 and STF-31 on tumor cell proliferation and survival, as well as on glucose uptake.

METHODS

Tumor-derived A172 (glioblastoma), BHY (oral squamous cell carcinoma), HeLa (cervix adenocarcinoma), HN (head neck cancer), HT-29 (colon carcinoma) and MG-63 (osteosarcoma) cells were treated with fasentin, WZB117, GMX1778 and STF-31. Proliferation rates and cell viabilities were assessed using XTT, crystal violet and LDH assays. mRNA and protein expression of GLUT1 and NAPRT were assessed using qPCR and Western blotting, respectively. The effects of inhibiting compounds on glucose uptake were measured using [¹⁸F]-fluoro-deoxyglucose uptake experiments.

RESULTS

Stimulation of tumor-derived cells with the different inhibitors tested revealed a complex pattern, whereby proliferation inhibiting and survival reducing concentrations varied in [¹⁸F]-fluoro-deoxyglucose uptake experiments more than one order of magnitude among the different cells tested. We found that the effects of GMX1778 and STF-31 could be partially abolished by (i) nicotinic acid (NA) only in nicotinic acid phosphoribosyltransferase (NAPRT) expressing cells and (ii) nicotinamide mononucleotide (NMN) in all cells tested, supporting the classification of these compounds as NAMPT inhibitors. In short-time [¹⁸F]-fluoro-deoxyglucose uptake experiments the application of WZB-117 was found to lead to an almost complete uptake inhibition in all cells tested, whereas the effect of fasentin was found to be cell type dependent with a maximum value of ~35% in A172, BHY, HeLa and HT-29 cells. We also found that STF-31 inhibited glucose uptake in all cells tested in a range of 25-50%. These data support the classification of STF-31 as a GLUT inhibitor.

CONCLUSIONS

Our data reveal a dual mode of action of STF-31, serving either as a NAMPT or as a GLUT inhibitor, whereby the latter seems to be apparent only at higher STF-31 concentrations. The molecular basis of such a dual function and its appearance in compounds previously designated as NAMPT-specific inhibitors requires further investigation.

Expression of glycolytic enzymes in ovarian cancers and evaluation of the glycolytic pathway as a strategy for ovarian cancer treatment

BACKGROUND

Novel therapeutic approaches are required to treat ovarian cancer and dependency on glycolysis may provide new targets for treatment. This study sought to investigate the variation of expression of molecular components (GLUT1, HKII, PKM2, LDHA) of the glycolytic pathway in ovarian cancers and the effectiveness of targeting this pathway in ovarian cancer cell lines with inhibitors.

METHODS

Expression of GLUT1, HKII, PKM2, LDHA were analysed by quantitative immunofluorescence in a tissue microarray (TMA) analysis of 380 ovarian cancers and associations with clinicopathological features were sought. The effect of glycolysis pathway inhibitors on the growth of a panel of ovarian cancer cell lines was assessed by use of the SRB proliferation assay. Combination studies were undertaken combining these inhibitors with cytotoxic agents.

RESULTS

Mean expression levels of GLUT1 and HKII were higher in high grade serous ovarian cancer (HGSOC), the most frequently occurring subtype, than in non-HGSOC. GLUT1 expression was also significantly higher in advanced stage (III/IV) ovarian cancer than early stage (I/II) disease. Growth dependency of ovarian cancer cells on glucose was demonstrated in a panel of ovarian cancer cell lines. Inhibitors of the glycolytic pathway (STF31, IOM-1190, 3PO and oxamic acid) attenuated cell proliferation in platinum-sensitive and platinum-resistant HGSOC cell line models in a concentration dependent manner. In combination with either cisplatin or paclitaxel, 3PO (a novel PFKFB3 inhibitor) enhanced the cytotoxic effect in both platinum sensitive and platinum resistant ovarian cancer cells. Furthermore, synergy was identified between STF31 (a novel GLUT1 inhibitor) or oxamic acid (an LDH inhibitor) when combined with metformin, an inhibitor of oxidative phosphorylation, resulting in marked inhibition of ovarian cancer cell growth.

CONCLUSIONS

The findings of this study provide further support for targeting the glycolytic pathway in ovarian cancer and several useful combinations were identified.

Cross resistance to diverse anticancer nicotinamide phosphoribosyltransferase inhibitors induced by FK866 treatment

Cross-resistance to drugs remains an unsolved problem in cancer chemotherapy. This study elucidates a molecular mechanism of cross-resistance to diverse inhibitors of nicotinamide phosphoribosyltransferase (NAMPT) with anticancer activity. We generated a variant of the human colon cancer cell line HCT116, HCT116R^FK866, which exhibited primary resistance to the potent NAMPT inhibitor FK866, and was approximately 1,000-fold less sensitive to the drug than the parental HCT116. HCT116R^FK866 was found to be cross-resistant to diverse NAMPT inhibitors, including CHS-828, GNE-617, and STF-118804. Whole-exon sequencing revealed two point mutations (H191R and K342R) in NAMPT in HCT116R^FK866, only one of which (K342R) was present in the parental HCT116. Importantly, the protein level, NAMPT enzyme activity, and intracellular NAD⁺ level were similar between HCT116R^FK866 and HCT116. Hence, we investigated NAMPT-binding partners in both cell lines by focused proteomic analyses. The amount of NAMPT precipitated with anti-NAMPT monoclonal antibody was much higher in HCT116R^FK866 than in the parental. Furthermore, in HCT116, but not in HCT116R^FK866, NAMPT was revealed to interact with POTE ankyrin domain family member E and beta-actin. Thus, these results suggest that NAMPT usually interacts with the two partner proteins, and the H191R mutation may prevent the interactions, resulting in resistance to diverse NAMPT inhibitors.

Metabolic reprogramming during hepatitis B disease progression offers novel diagnostic and therapeutic opportunities

Metabolic remodeling occurs in immune cells during an infection. Host cells must upregulate energy production for growth, proliferation, and effector functions to limit the damage imposed by pathogens. One example, the hepatitis B virus, induces hepatic injury in human hepatocytes through dysregulation of aerobic glycolysis and lipid metabolism. Increased glycolytic metabolism mediated by elevated expression of Glut1, glucose influx, and lactate secretion is associated with this Warburg phenotype, a classic metabolic signature also observed in cancer cells. This article brings into focus the tight interaction between HBV infection and metabolic dysfunction and how these processes facilitate the progression of end-stage liver diseases, such as hepatocellular carcinoma. We also provide evidence and models by which other viruses such as HIV and Zika disrupt their host metabolic machinery. The emergence of the immunometabolism field provides novel opportunities to take advantage of intermediary metabolites and key metabolic pathways for diagnostic and therapeutic purposes.

A Red-Light-Activated Ruthenium-Caged NAMPT Inhibitor Remains Phototoxic in Hypoxic Cancer Cells

We describe two water-soluble ruthenium complexes, [1]Cl₂ and [2]Cl₂ , that photodissociate to release a cytotoxic nicotinamide phosphoribosyltransferase (NAMPT) inhibitor with a low dose (21 J cm^-2 ) of red light in an oxygen-independent manner. Using a specific NAMPT activity assay, up to an 18-fold increase in inhibition potency was measured upon red-light activation of [2]Cl₂ , while [1]Cl₂ was thermally unstable. For the first time, the dark and red-light-induced cytotoxicity of these photocaged compounds could be tested under hypoxia (1 % O₂ ). In skin (A431) and lung (A549) cancer cells, a 3- to 4-fold increase in cytotoxicity was found upon red-light irradiation for [2]Cl₂ , whether the cells were cultured and irradiated with 1 % or 21 % O₂ . These results demonstrate the potential of photoactivated chemotherapy for hypoxic cancer cells, in which classical photodynamic therapy, which relies on oxygen activation, is poorly efficient.

Splicing modulators act at the branch point adenosine binding pocket defined by the PHF5A-SF3b complex

Pladienolide, herboxidiene and spliceostatin have been identified as splicing modulators that target SF3B1 in the SF3b subcomplex. Here we report that PHF5A, another component of this subcomplex, is also targeted by these compounds. Mutations in PHF5A-Y36, SF3B1-K1071, SF3B1-R1074 and SF3B1-V1078 confer resistance to these modulators, suggesting a common interaction site. RNA-seq analysis reveals that PHF5A-Y36C has minimal effect on basal splicing but inhibits the global action of splicing modulators. Moreover, PHF5A-Y36C alters splicing modulator-induced intron-retention/exon-skipping profile, which correlates with the differential GC content between adjacent introns and exons. We determine the crystal structure of human PHF5A demonstrating that Y36 is located on a highly conserved surface. Analysis of the cryo-EM spliceosome B^act complex shows that the resistance mutations cluster in a pocket surrounding the branch point adenosine, suggesting a competitive mode of action. Collectively, we propose that PHF5A–SF3B1 forms a central node for binding to these splicing modulators.

A number of natural occurring small-molecule splicing modulators are known. Here, the authors combine chemogenomic, structural and biochemical methods and show that these compounds also target the spliceosome-associated protein PHF5A and propose a potential modulator binding site in the PHF5A–SF3B1 complex.

Epstein-Barr Virus-Encoded Latent Membrane Protein 1 Upregulates Glucose Transporter 1 Transcription via the mTORC1/NF-κB Signaling Pathways

Accumulating evidence indicates that oncogenic viral protein plays a crucial role in activating aerobic glycolysis during tumorigenesis, but the underlying mechanisms are largely undefined. Epstein-Barr virus (EBV)-encoded latent membrane protein 1 (LMP1) is a transmembrane protein with potent cell signaling properties and has tumorigenic transformation property. Activation of NF-κB is a major signaling pathway mediating many downstream transformation properties of LMP1. Here we report that activation of mTORC1 by LMP1 is a key modulator for activation of NF-κB signaling to mediate aerobic glycolysis. NF-κB activation is involved in the LMP1-induced upregulation of glucose transporter 1 (Glut-1) transcription and growth of nasopharyngeal carcinoma (NPC) cells. Blocking the activity of mTORC1 signaling effectively suppressed LMP1-induced NF-κB activation and Glut-1 transcription. Interfering NF-κB signaling had no effect on mTORC1 activity but effectively altered Glut-1 transcription. Luciferase promoter assay of Glut-1 also confirmed that the Glut-1 gene is a direct target gene of NF-κB signaling. Furthermore, we demonstrated that C-terminal activating region 2 (CTAR2) of LMP1 is the key domain involved in mTORC1 activation, mainly through IKKβ-mediated phosphorylation of TSC2 at Ser⁹³⁹ Depletion of Glut-1 effectively led to suppression of aerobic glycolysis, inhibition of cell proliferation, colony formation, and attenuation of tumorigenic growth property of LMP1-expressing nasopharyngeal epithelial (NPE) cells. These findings suggest that targeting the signaling axis of mTORC1/NF-κB/Glut-1 represents a novel therapeutic target against NPC.IMPORTANCE Aerobic glycolysis is one of the hallmarks of cancer, including NPC. Recent studies suggest a role for LMP1 in mediating aerobic glycolysis. LMP1 expression is common in NPC. The delineation of essential signaling pathways induced by LMP1 in aerobic glycolysis contributes to the understanding of NPC pathogenesis. This study provides evidence that LMP1 upregulates Glut-1 transcription to control aerobic glycolysis and tumorigenic growth of NPC cells through mTORC1/NF-κB signaling. Our results reveal novel therapeutic targets against the mTORC1/NF-κB/Glut-1 signaling axis in the treatment of EBV-infected NPC.

Cardiomyocyte Differentiation Promotes Cell Survival During Nicotinamide Phosphoribosyltransferase Inhibition Through Increased Maintenance of Cellular Energy Stores

To address concerns regarding the tumorigenic potential of undifferentiated human pluripotent stem cells (hPSC) that may remain after in vitro differentiation and ultimately limit the broad use of hPSC‐derivatives for therapeutics, we recently described a method to selectively eliminate tumorigenic hPSC from their progeny by inhibiting nicotinamide phosphoribosyltransferase (NAMPT). Limited exposure to NAMPT inhibitors selectively removes hPSC from hPSC‐derived cardiomyocytes (hPSC‐CM) and spares a wide range of differentiated cell types; yet, it remains unclear when and how cells acquire resistance to NAMPT inhibition during differentiation. In this study, we examined the effects of NAMPT inhibition among multiple time points of cardiomyocyte differentiation. Overall, these studies show that in vitro cardiomyogenic commitment and continued culturing provides resistance to NAMPT inhibition and cell survival is associated with the ability to maintain cellular ATP pools despite depletion of NAD levels. Unlike cells at earlier stages of differentiation, day 28 hPSC‐CM can survive longer periods of NAMPT inhibition and maintain ATP generation by glycolysis and/or mitochondrial respiration. This is distinct from terminally differentiated fibroblasts, which maintain mitochondrial respiration during NAMPT inhibition. Overall, these results provide new mechanistic insight into how regulation of cellular NAD and energy pools change with hPSC‐CM differentiation and further inform how NAMPT inhibition strategies could be implemented within the context of cardiomyocyte differentiation. Stem Cells Translational Medicine2017;6:1191–1201

NAD+ salvage pathway in cancer metabolism and therapy

Nicotinamide adenine dinucleotide (NAD⁺) is an essential coenzyme for various physiological processes including energy metabolism, DNA repair, cell growth, and cell death. Many of these pathways are typically dysregulated in cancer cells, making NAD⁺ an intriguing target for cancer therapeutics. NAD⁺ is mainly synthesized by the NAD⁺ salvage pathway in cancer cells, and not surprisingly, the pharmacological targeting of the NAD⁺ salvage pathway causes cancer cell cytotoxicity in vitro and in vivo. Several studies have described the precise consequences of NAD⁺ depletion on cancer biology, and have demonstrated that NAD+ depletion results in depletion of energy levels through lowered rates of glycolysis, reduced citric acid cycle activity, and decreased oxidative phosphorylation. Additionally, depletion of NAD⁺ causes sensitization of cancer cells to oxidative damage by disruption of the anti-oxidant defense system, decreased cell proliferation, and initiation of cell death through manipulation of cell signaling pathways (e.g., SIRT1 and p53). Recently, studies have explored the effect of well-known cancer therapeutics in combination with pharmacological depletion of NAD⁺ levels, and found in many cases a synergistic effect on cancer cell cytotoxicity. In this context, we will discuss the effects of NAD⁺ salvage pathway inhibition on cancer cell biology and provide insight on this pathway as a novel anti-cancer therapeutic target.

Structure-Based Design of Potent Nicotinamide Phosphoribosyltransferase Inhibitors with Promising in Vitro and in Vivo Antitumor Activities

Inhibition of nicotinamide phosphoribosyltransferase (NAMPT) has the potential to directly limit NAD production in cancer cells and is an effective strategy for cancer treatment. Using a structure-based strategy, we have designed a new class of potent small-molecule inhibitors of NAMPT. Several designed compounds showed promising antiproliferative activities in vitro. (E)-N-(5-((4-(((2-(1H-Indol-3-yl)ethyl)(isopropyl)amino)methyl)phenyl)amino)pentyl)-3-(pyridin-3-yl)acrylamide, 30, bearing an indole moiety, has an IC50 of 25.3 nM for binding to the NAMPT protein and demonstrated promising inhibitory activities in the nanomolar range against several cancer cell lines (MCF-7 GI50 = 0.13 nM; MDA-MB-231 GI50 = 0.15 nM). Triple-negative breast cancer is the most malignant subtype of breast cancer with no effective targeted treatments currently available. Significant antitumor efficacy of compound 30 was achieved (TGI was 73.8%) in an orthotopic MDA-MB-231 triple-negative breast cancer xenograft tumor model. This paper reports promising lead molecules for the inhibition of NAMPT which could serve as a basis for further investigation.

Small Molecule Inhibited Parathyroid Hormone Mediated cAMP Response by N-Terminal Peptide Binding

Ligand binding to certain classes of G protein coupled receptors (GPCRs) stimulates the rapid synthesis of cAMP through G protein. Human parathyroid hormone (PTH), a member of class B GPCRs, binds to its receptor via its N–terminal domain, thereby activating the pathway to this secondary messenger inside cells. Presently, GPCRs are the target of many pharmaceuticals however, these drugs target only a small fraction of structurally known GPCRs (about 10%). Coordination complexes are gaining interest due to their wide applications in the medicinal field. In the present studies we explored the potential of a coordination complex of Zn(II) and anthracenyl–terpyridine as a modulator of the parathyroid hormone response. Preferential interactions at the N–terminal domain of the peptide hormone were manifested by suppressed cAMP generation inside the cells. These observations contribute a regulatory component to the current GPCR–cAMP paradigm, where not the receptor itself, but the activating hormone is a target. To our knowledge, this is the first report about a coordination complex modulating GPCR activity at the level of deactivating its agonist. Developing such molecules might help in the control of pathogenic PTH function such as hyperparathyroidism, where control of excess hormonal activity is essentially required.

Correlating chemical sensitivity and basal gene expression reveals mechanism of action

Changes in cellular gene expression in response to small-molecule or genetic perturbations have yielded signatures that can connect unknown mechanisms of action (MoA) to ones previously established. We hypothesized that differential basal gene expression could be correlated with patterns of small-molecule sensitivity across many cell lines to illuminate the actions of compounds whose MoA are unknown. To test this idea, we correlated the sensitivity patterns of 481 compounds with ∼19,000 basal transcript levels across 823 different human cancer cell lines and identified selective outlier transcripts. This process yielded many novel mechanistic insights, including the identification of activation mechanisms, cellular transporters and direct protein targets. We found that ML239, originally identified in a phenotypic screen for selective cytotoxicity in breast cancer stem-like cells, most likely acts through activation of fatty acid desaturase 2 (FADS2). These data and analytical tools are available to the research community through the Cancer Therapeutics Response Portal.