Dual targeting of the Warburg effect with a glucose-conjugated lactate dehydrogenase inhibitor

A patent review of lactate dehydrogenase inhibitors (2014-present)

INTRODUCTION

Lactate dehydrogenase (LDH) is a key enzyme in glycolysis responsible for the conversion of pyruvate into lactate and vice versa. Lactate plays a crucial role in tumor progression and metastasis; therefore, reducing lactate production by inhibiting LDH is considered an optimal strategy to tackle cancer. Additionally, dysregulation of LDH activity is correlated with other pathologies, such as cardiovascular and neurodegenerative diseases as well as primary hyperoxaluria, fibrosis and cryptosporidiosis. Hence, LDH inhibitors could serve as potential therapeutics for treating these pathological conditions.

AREAS COVERED

This review covers patents published since 2014 up to the present in the Espacenet database, concerning LDH inhibitors and their potential therapeutic applications.

EXPERT OPINION

Over the past 10 years, different compounds have been identified as LDH inhibitors. Some of them are derived from the chemical optimization of already known LDH inhibitors (e.g. pyrazolyl derivatives, quinoline 3-sulfonamides), while others belong to newly identified chemical classes of LDH inhibitors. LDH inhibition has proven to be a promising therapeutic strategy not only for preventing human pathologies, but also for treating animal diseases. The published patents from both academia and the pharmaceutical industry highlight the persistent high interest of the scientific community in developing efficient LDH inhibitors.

Glycoconjugate coumarins exploiting metabolism-enhanced fluorescence and preferential uptake: New optical tools for tumor cell staining

The possibility to visually discriminate cells based on their metabolism and capability to uptake exogenous molecules is an important topic with exciting fallback on translational and precision medicine. To this end, probes that combine several complementary features are necessary. The ideal probe is selectively uptaken and activated in tumor cells compared with control ones and is not fluorescent in the extracellular medium. Fluorogenic compounds that combine enzyme-activated pH sensitivity and good cell uptake can be an ideal solution, provided that the sensed enzymes are dysregulated in tumor cells. Here, we present synthesis and in vitro evaluation of a new class of glyco-coumarin based probes that merge all these features. These probes show uptake ratio in tumor vs. control cells up to 3:1, with a cell to background ratio upon administration of the probe up to 5:1. These features make this new family of fluorogenic targeted probes a promising tool in life science.

Multiplex genome editing eliminates the Warburg Effect without impacting growth rate in mammalian cells

The Warburg effect is ubiquitous in proliferative mammalian cells, including cancer cells, but poses challenges for biopharmaceutical production, as lactate accumulation inhibits cell growth and protein production. Previous efforts to eliminate lactate production via knockout have failed in mammalian bioprocessing since lactate dehydrogenase has proven essential. However, here we eliminated the Warburg effect in Chinese hamster ovary (CHO) and HEK293 cells by simultaneously knocking out lactate dehydrogenase and regulators involved in a negative feedback loop that typically inhibits pyruvate conversion to acetyl-CoA. In contrast to long-standing assumptions about the role of aerobic glycolysis, Warburg-null cells maintain wildtype growth rate while producing negligible lactate. Further characterization of Warburg-null CHO cells showed a compensatory increase in oxygen consumption, a near total reliance on oxidative metabolism, and higher cell densities in fed-batch cell culture. These cells remained amenable for production of diverse biotherapeutic proteins, reaching industrially relevant titers and maintaining product glycosylation. Thus, the ability to eliminate the Warburg effect is an important development for biotherapeutic production and provides a tool for investigating a near-universal metabolic phenomenon.

The determinants of metabolic discrepancies in aerobic glycolysis: Providing potential targets for breast cancer treatment

Altered aerobic glycolysis is the robust mechanism to support cancer cell survival and proliferation beyond the maintenance of cellular energy metabolism. Several investigators portrayed the important role of deregulated glycolysis in different cancers, including breast cancer. Breast cancer is the most ubiquitous form of cancer and the primary cause of cancer death in women worldwide. Breast cancer with increased glycolytic flux is hampered to eradicate with current therapies and can result in tumor recurrence. In spite of the low order efficiency of ATP production, cancer cells are highly addicted to glycolysis. The glycolytic dependency of cancer cells provides potential therapeutic strategies to preferentially kill cancer cells by inhibiting glycolysis using antiglycolytic agents. The present review emphasizes the most recent research on the implication of glycolytic enzymes, including glucose transporters (GLUTs), hexokinase (HK), phosphofructokinase (PFK), pyruvate kinase (PK), lactate dehydrogenase-A (LDHA), associated signalling pathways and transcription factors, as well as the antiglycolytic agents that target key glycolytic enzymes in breast cancer. The potential activity of glycolytic inhibitors impinges cancer prevalence and cellular resistance to conventional drugs even under worse physiological conditions such as hypoxia. As a single agent or in combination with other chemotherapeutic drugs, it provides the feasibility of new therapeutic modalities against a wide spectrum of human cancers.

Combined inhibition of pyruvate dehydrogenase kinase 1 and lactate dehydrogenase a induces metabolic and signaling reprogramming and enhances lung adenocarcinoma cell killing

Lung adenocarcinoma (LUAD) is one of the most prevalent and aggressive types of lung cancer. Metabolic reprogramming plays a critical role in the development and progression of LUAD. Pyruvate dehydrogenase kinase 1 (PDK1) and lactate dehydrogenase A (LDHA) are two key enzymes involved in glucose metabolism, whilst their aberrant expressions are often associated with tumorigenesis. Herein, we investigated the anticancer effects of combined inhibition of PDK1 and LDHA in LUAD in vitro and in vivo and its underlying mechanisms of action. The combination of a PDK1 inhibitor, 64, and a LDHA inhibitor, NHI-Glc-2, led to a synergistic growth inhibition in 3 different LUAD cell lines and more than additively suppressed tumor growth in the LUAD xenograft H1975 model. This combination also inhibited cellular migration and colony formation, while it induced a metabolic shift from glycolysis to oxidative phosphorylation (OXPHOS) resulting in mitochondrial depolarization and apoptosis in LUAD cells. These effects were related to modulation of multiple cell signaling pathways, including AMPK, RAS/ERK, and AKT/mTOR. Our findings demonstrate that simultaneous inhibition of multiple glycolytic enzymes (PDK1 and LDHA) is a promising novel therapeutic approach for LUAD.

Biomimetic Approach to Promote Cellular Uptake and Enhance Photoacoustic Properties of Tumor-Seeking Dyes

The attachment of glucose to drugs and imaging agents enables cancer cell targeting via interactions with GLUT1 overexpressed on the cell surface. While an added benefit of this modification is the solubilizing effect of carbohydrates, in the context of imaging agents, aqueous solubility does not guarantee decreased π-stacking or aggregation. The resulting broadening of the absorbance spectrum is a detriment to photoacoustic (PA) imaging since the signal intensity, accuracy, and image quality all rely on reliable spectral unmixing. To address this major limitation and further enhance the tumor-targeting ability of imaging agents, we have taken a biomimetic approach to design a multivalent glucose moiety (mvGlu). We showcase the utility of this new group by developing aza-BODIPY-based contrast agents boasting a significant PA signal enhancement greater than 11-fold after spectral unmixing. Moreover, when applied to targeting cancer cells, effective staining could be achieved with ultra-low dye concentrations (50 nM) and compared to a non-targeted analogue, the signal intensity was >1000-fold higher. Lastly, we employed the mvGlu technology to develop a logic-gated acoustogenic probe to detect intratumoral copper (i.e., Cu(I)), which is an emerging cancer biomarker, in a murine model of breast cancer. This exciting application was not possible using other acoustogenic probes previously developed for copper sensing.

Role of LDH in tumor glycolysis: Regulation of LDHA by small molecules for cancer therapeutics

Lactate dehydrogenase (LDH) is one of the crucial enzymes in aerobic glycolysis, catalyzing the last step of glycolysis, i.e. the conversion of pyruvate to lactate. Most cancer cells are characterized by an enhanced rate of tumor glycolysis to ensure the energy demand of fast-growing cancer cells leading to increased lactate production. Excess lactate creates extracellular acidosis which facilitates invasion, angiogenesis, and metastasis and affects the immune response. Lactate shuttle and lactate symbiosis is established in cancer cells, which may further increase the poor prognosis. Several genetic and phenotypic studies established the potential role of lactate dehydrogenase A (LDHA) or LDH5, the one homo-tetramer of subunit A, in cancer development and metastasis. The LDHA is considered a viable target for drug design and discovery. Several small molecules have been discovered to date exhibiting significant LDHA inhibitory activities and anticancer activities, therefore the starvation of cancer cells by targeting tumor glycolysis through LDHA inhibition with improved selectivity can generate alternative anticancer therapeutics. This review provides an overview of the role of LDHA in metabolic reprogramming and its association with proto-oncogenes and oncogenes. This review also aims to deliver an update on significant LDHA inhibitors with anticancer properties and future direction in this area.

Targeting Energy Metabolism in Cancer Treatment

Cancer is the second most common cause of death worldwide after cardiovascular diseases. The development of molecular and biochemical techniques has expanded the knowledge of changes occurring in specific metabolic pathways of cancer cells. Increased aerobic glycolysis, the promotion of anaplerotic responses, and especially the dependence of cells on glutamine and fatty acid metabolism have become subjects of study. Despite many cancer treatment strategies, many patients with neoplastic diseases cannot be completely cured due to the development of resistance in cancer cells to currently used therapeutic approaches. It is now becoming a priority to develop new treatment strategies that are highly effective and have few side effects. In this review, we present the current knowledge of the enzymes involved in the different steps of glycolysis, the Krebs cycle, and the pentose phosphate pathway, and possible targeted therapies. The review also focuses on presenting the differences between cancer cells and normal cells in terms of metabolic phenotype. Knowledge of cancer cell metabolism is constantly evolving, and further research is needed to develop new strategies for anti-cancer therapies.

Lactate dehydrogenase A inhibition by small molecular entities: steps in the right direction

Direct targeting of energy metabolism to defeat cancer is not a recent strategy. Although quite a few drugs use cellular metabolism for their antitumor effect, no direct inhibitors of energy metabolism have been approved by the FDA. Currently, several inhibitors of lactate dehydrogenase A (LDH-A), a key player in glycolysis, are in development. Earlier, we demonstrated the efficacy of N-hydroxyindole-based LDH-A inhibitors in different cancer types. In this study we describe the efficacy of NHI-Glc-2, which is designed to dual target cancer cells, by exploiting a simultaneous enhanced glucose uptake by overexpressed glucose transporter 1 (GLUT1) and by inhibition of LDH-A. NHI-Glc-2 inhibits LDH-A enzyme activity, PANC-1 cell growth and disrupts spheroid integrity, with an overall effect that is more pronounced when combined with gemcitabine.

Synergisms of genome and metabolism stabilizing antitumor therapy (GMSAT) in human breast and colon cancer cell lines: a novel approach to screen for synergism

BACKGROUND

Despite an improvement of prognosis in breast and colon cancer, the outcome of the metastatic disease is still severe. Microevolution of cancer cells often leads to drug resistance and tumor-recurrence. To target the driving forces of the tumor microevolution, we focused on synergistic drug combinations of selected compounds. The aim is to prevent the tumor from evolving in order to stabilize disease remission. To identify synergisms in a high number of compounds, we propose here a three-step concept that is cost efficient, independent of high-throughput machines and reliable in its predictions.

METHODS

We created dose response curves using MTT- and SRB-assays with 14 different compounds in MCF-7, HT-29 and MDA-MB-231 cells. In order to efficiently screen for synergies, we developed a screening tool in which 14 drugs were combined (91 combinations) in MCF-7 and HT-29 using EC25 or less. The most promising combinations were verified by the method of Chou and Talalay.

RESULTS

All 14 compounds exhibit antitumor effects on each of the three cell lines. The screening tool resulted in 19 potential synergisms detected in HT-29 (20.9%) and 27 in MCF-7 (29.7%). Seven of the top combinations were further verified over the whole dose response curve, and for five combinations a significant synergy could be confirmed. The combination Nutlin-3 (inhibition of MDM2) and PX-478 (inhibition of HIF-1α) could be confirmed for all three cell lines. The same accounts for the combination of Dichloroacetate (PDH activation) and NHI-2 (LDH-A inhibition). Our screening method proved to be an efficient tool that is reliable in its projections.

CONCLUSIONS

The presented three-step concept proved to be cost- and time-efficient with respect to the resulting data. The newly found combinations show promising results in MCF-7, HT-29 and MDA-MB231 cancer cells.

Impact of hypoxia on chemoresistance of mesothelioma mediated by the proton-coupled folate transporter, and preclinical activity of new anti-LDH-A compounds

BACKGROUND

Expression of proton-coupled folate transporter (PCFT) is associated with survival of mesothelioma patients treated with pemetrexed, and is reduced by hypoxia, prompting studies to elucidate their correlation.

METHODS

Modulation of glycolytic gene expression was evaluated by PCR arrays in tumour cells and primary cultures growing under hypoxia, in spheroids and after PCFT silencing. Inhibitors of lactate dehydrogenase (LDH-A) were tested in vitro and in vivo. LDH-A expression was determined in tissue microarrays of radically resected malignant pleural mesothelioma (MPM, N = 33) and diffuse peritoneal mesothelioma (DMPM, N = 56) patients.

RESULTS

Overexpression of hypoxia marker CAIX was associated with low PCFT expression and decreased MPM cell growth inhibition by pemetrexed. Through integration of PCR arrays in hypoxic cells and spheroids and following PCFT silencing, we identified the upregulation of LDH-A, which correlated with shorter survival of MPM and DMPM patients. Novel LDH-A inhibitors enhanced spheroid disintegration and displayed synergistic effects with pemetrexed in MPM and gemcitabine in DMPM cells. Studies with bioluminescent hypoxic orthotopic and subcutaneous DMPM athymic-mice models revealed the marked antitumour activity of the LDH-A inhibitor NHI-Glc-2, alone or combined with gemcitabine.

CONCLUSIONS

This study provides novel insights into hypoxia/PCFT-dependent chemoresistance, unravelling the potential prognostic value of LDH-A, and demonstrating the preclinical activity of LDH-A inhibitors.

Lactate Dehydrogenase Inhibition: Biochemical Relevance and Therapeutical Potential

Lactate dehydrogenase (LHD) is a key enzyme of anaerobic metabolism in almost all living organisms and it is also a functional checkpoint for glucose restoration during gluconeogenesis and single-stranded DNA metabolism. This enzyme has a well preserved structure during evolution and among the species, with little, but sometimes very useful, changes in the amino acid sequence, which makes it an attractive target for the design and construction of functional molecules able to modulate its catalytic potential and expression. Research has focused mainly on the selection of modulator especially as far as LDH isozymes (especially LDH-5) and lactate dehydrogenases of Plasmodium falciparum (pfLDH) are concerned. This review summarizes the recent advances in the design and development of inhibitors, pointing out their specificity and therapeutic potentials.

New avenues in pancreatic cancer: exploiting microRNAs as predictive biomarkers and new approaches to target aberrant metabolism

Introduction: Most pancreatic cancer patients are diagnosed at advanced-stages and first-line regimens (FOLFIRINOX and gemcitabine/nab-paclitaxel) provide limited survival advantage and are associated with considerable toxicities. In this grim scenario, novel treatments and biomarkers are warranted.Areas covered: MicroRNAs (miRNAs) emerged as biomarkers for cancer prognosis and chemoresistance and blood-based miRNAs are being evaluated as indicators of therapeutic activity. Moreover, aberrant metabolism, such as aerobic glycolysis, has been correlated to tumor aggressiveness and poor prognosis. Against this background, innovative approaches to tackle metabolic aberrations are being implemented and glycolytic inhibitors targeting lactate dehydrogenase-A (LDH-A) showed promising effects in preclinical models. A PubMed search was used to compile relevant publications until February 2019.Expert opinion: Analysis of tissue/circulating miRNA might improve selection for optimal treatment regimens. For instance, miR-181a modulation seems to predict response to FOLFIRINOX. However, we need further studies to validate predictive miRNA profiles, as well as to exploit miRNAs for treatment-tailoring. Several miRNAs have also a key role in regulating metabolic aberrations. Since preliminary evidence supports the development of new agents targeting these aberrations, such as LDH-A inhibitors, the identification of biomarkers for these treatments, including the above-mentioned miRNAs, should shorten the gap between preclinical studies and personalized therapies.

Synthesis and Biological Evaluation of New Glycoconjugated LDH Inhibitors as Anticancer Agents

Conjugation of known biologically active molecules to carbohydrate frameworks represents a valuable option for the preparation of hybrid, structurally-related families of compounds with the aim of modulating their biological response. Therefore, we present here a study on the preparation of d-galacto, d-manno, d-gluco, and d-lactose glycoconjugates of an established N-hydroxyindole-based (NHI) inhibitor of lactated dehydrogenase (LDH). Structural variations involved the sugar stereochemistry and size as well as the anchoring point of the NHI on the carbohydrate frame (either C-1 or C-6). In the case of the galactose anomeric glycoconjugate (C-1), intriguing solvent-dependent effects were observed in the glycosylation stereochemical outcome. The biological activity of the deprotected glycoconjugates in contrasting lactate formation and cancer cell proliferation are described.

Extrinsic and Intrinsic Immunometabolism Converge: Perspectives on Future Research and Therapeutic Development for Obesity

PURPOSE OF REVIEW

Research over the past decade has shown that immunologic and metabolic pathways are intricately linked. This burgeoning field of immunometabolism includes intrinsic and extrinsic pathways and is known to be associated with obesity-accelerated metabolic disease. Intrinsic immunometabolism includes the study of fuel utilization and bioenergetic pathways that influence immune cell function. Extrinsic immunometabolism includes the study of immune cells and products that influence systemic metabolism.

RECENT FINDINGS

Th2 immunity, macrophage iron handling, adaptive immune memory, and epigenetic regulation of immunity, which all require intrinsic metabolic changes, play a role in systemic metabolism and metabolic function, linking the two arms of immunometabolism. Together, this suggests that targeting intrinsic immunometabolism can directly affect immune function and ultimately systemic metabolism. We highlight important questions for future basic research that will help improve translational research and provide therapeutic targets to help establish new treatments for obesity and associated metabolic disorders.

Polyunsaturated Fatty Acid Desaturation Is a Mechanism for Glycolytic NAD+ Recycling

The reactions catalyzed by the delta-5 and delta-6 desaturases (D5D/D6D), key enzymes responsible for highly unsaturated fatty acid (HUFA) synthesis, regenerate NAD⁺ from NADH. Here, we show that D5D/D6D provide a mechanism for glycolytic NAD⁺ recycling that permits ongoing glycolysis and cell viability when the cytosolic NAD⁺/NADH ratio is reduced, analogous to lactate fermentation. Although lesser in magnitude than lactate production, this desaturase-mediated NAD⁺ recycling is acutely adaptive when aerobic respiration is impaired in vivo. Notably, inhibition of either HUFA synthesis or lactate fermentation increases the other, underscoring their interdependence. Consistent with this, a type 2 diabetes risk haplotype in SLC16A11 that reduces pyruvate transport (thus limiting lactate production) increases D5D/D6D activity in vitro and in humans, demonstrating a chronic effect of desaturase-mediated NAD⁺ recycling. These findings highlight key biologic roles for D5D/D6D activity independent of their HUFA end products and expand the current paradigm of glycolytic NAD⁺ regeneration.

First Examples of H2S-Releasing Glycoconjugates: Stereoselective Synthesis and Anticancer Activities

H2S donors are currently emerging as promising therapeutic agents in a wide variety of pathologies, including tumors. Cancer cells are characterized by an enhanced uptake of sugars, such as glucose. Therefore, novel glycoconjugated H2S donors were synthesized so that high concentrations of H2S can be selectively achieved therein. Dithiolethione portions or isothiocyanate portions were selected for their well-known H2S-releasing properties in the presence of biological substrates. A synthetic procedure employing trichloroacetimidate glycosyl donors was applied to produce, in a stereoselective fashion, C1-glycoconjugates, whereas C6-glycoconjugates were obtained by a Mitsunobu-based transformation. The resulting molecules were then tested for their anticancer effects on human pancreas adenocarcinoma ascites metastasis cell line AsPC-1. The most potent inhibitors of cell viability (6aβ and 7b) proved to release H2S inside the AsPC-1 cells and to alter the basal cell cycle.

A rhodamine based fluorescent probe validates substrate and cellular hypoxia specific NADH expression

A novel rhodamine-based redox probe (MQR) was developed to visualize the alteration of the NADH level under diverse metabolic perturbations.

Increased Lactate Secretion by Cancer Cells Sustains Non-cell-autonomous Adaptive Resistance to MET and EGFR Targeted Therapies

The microenvironment influences cancer drug response and sustains resistance to therapies targeting receptor-tyrosine kinases. However, if and how the tumor microenvironment can be altered during treatment, contributing to resistance onset, is not known. We show that, under prolonged treatment with tyrosine kinase inhibitors (TKIs), EGFR- or MET-addicted cancer cells displayed a metabolic shift toward increased glycolysis and lactate production. We identified secreted lactate as the key molecule instructing cancer-associated fibroblasts to produce hepatocyte growth factor (HGF) in a nuclear factor κB-dependent manner. Increased HGF, activating MET-dependent signaling in cancer cells, sustained resistance to TKIs. Functional or pharmacological targeting of molecules involved in the lactate axis abrogated in vivo resistance, demonstrating the crucial role of this metabolite in the adaptive process. This adaptive resistance mechanism was observed in lung cancer patients progressed on EGFR TKIs, demonstrating the clinical relevance of our findings and opening novel scenarios in the challenge to drug resistance.

Three-Dimensional Analysis of the Interactions between hLDH5 and Its Inhibitors

Inhibitors of human lactate dehydrogenase (hLDH5)—the enzyme responsible for the conversion of pyruvate to lactate coupled with oxidation of NADH to NAD⁺—are promising therapeutic agents against cancer because this enzyme is generally found to be overexpressed in most invasive cancer cells and is linked to their vitality especially under hypoxic conditions. Consequently, significant efforts have been made for the identification of small-molecule hLDH5 inhibitors displaying high inhibitory potencies. X-ray structure of hLDH5 complexes as well as molecular modeling studies contribute to identify and explain the main binding modes of hLDH5 inhibitors reported in literature. The purpose of this review is to analyze the main three-dimensional interactions between some of the most potent inhibitors and hLDH5, in order to provide useful suggestions for the design of new derivatives.

Constituents of Polygala flavescens ssp. flavescens and Their Activity as Inhibitors of Human Lactate Dehydrogenase

Four new flavonol glycosides (1-4), two oligosaccharides (5, 6), one α-ionone (7), and three triterpenoid saponins (8-10), together with four known secondary metabolites (11-14), were isolated from the aerial parts of Polygala flavescens ssp. flavescens. All structures were elucidated on the basis of their spectroscopic and spectrometric data. The isolates were assayed for their inhibitory activity against isoform 5 of human lactate dehydrogenase, and compound 11 (3,6'-di-O-sinapoylsucrose) showed an IC₅₀ value of 90.4 μM. Modeling studies were carried out to suggest the putative interaction mode of compound 11 in the enzyme active site.

Brucella abortus Induces a Warburg Shift in Host Metabolism That Is Linked to Enhanced Intracellular Survival of the Pathogen

Intracellular bacterial pathogens exploit host cell resources to replicate and survive inside the host. Targeting these host systems is one promising approach to developing novel antimicrobials to treat intracellular infections. We show that human macrophage-like cells infected with Brucella abortus undergo a metabolic shift characterized by attenuated tricarboxylic acid cycle metabolism, reduced amino acid consumption, altered mitochondrial localization, and increased lactate production. This shift to an aerobic glycolytic state resembles the Warburg effect, a change in energy production that is well described in cancer cells and also occurs in activated inflammatory cells. B. abortus efficiently uses lactic acid as its sole carbon and energy source and requires the ability to metabolize lactate for normal survival in human macrophage-like cells. We demonstrate that chemical inhibitors of host glycolysis and lactate production do not affect in vitro growth of B. abortus in axenic culture but decrease its survival in the intracellular niche. Our data support a model in which infection shifts host metabolism to a Warburg-like state, and B. abortus uses this change in metabolism to promote intracellular survival. Pharmacological perturbation of these features of host cell metabolism may be a useful strategy to inhibit infection by intracellular pathogens.IMPORTANCEBrucella spp. are intracellular bacterial pathogens that cause disease in a range of mammals, including livestock. Transmission from livestock to humans is common and can lead to chronic human disease. Human macrophage-like cells infected with Brucella abortus undergo a Warburg-like metabolic shift to an aerobic glycolytic state where the host cells produce lactic acid and have reduced amino acid catabolism. We provide evidence that the pathogen can exploit this change in host metabolism to support growth and survival in the intracellular niche. Drugs that inhibit this shift in host cell metabolism inhibit intracellular replication and decrease the survival of B. abortus in an in vitro infection model; these drugs may be broadly useful therapeutics for intracellular infections.

Reactive Oxygen Species Synergize To Potently and Selectively Induce Cancer Cell Death

A distinctive feature of cancer cells is their elevated levels of reactive oxygen species (ROS), a trait that can cause cancer cells to be more sensitive to ROS-inducing agents than normal cells. ROS take several forms, each with different reactivity and downstream consequence. Here we show that simultaneous generation of superoxide and hydrogen peroxide within cancer cells results in significant synergy, potently and selectively causing cancer cell death. In these experiments superoxide is generated using the NAD(P)H quinone oxidoreductase 1 (NQO1) substrate deoxynyboquinone (DNQ), and hydrogen peroxide is generated using the lactate dehydrogenase A (LDH-A) inhibitor NHI-Glc-2. This combination reduces tumor burden and prolongs survival in a mouse model of lung cancer. These data suggest that simultaneous induction of superoxide and hydrogen peroxide can be a powerful and selective anticancer strategy.

Synthesis, Binding Properties, and Differences in Cell Uptake of G-Quadruplex Ligands Based on Carbohydrate Naphthalene Diimide Conjugates

The G-quadruplexes (G4s) are currently being explored as therapeutic targets in cancer and other pathologies. Six carbohydrate naphthalene diimide conjugates (carb-NDIs) have been synthesized as G4 ligands to investigate their potential selectivity in G4 binding and cell penetration. Carb-NDIs have shown certain selectivity for G4 structures against DNA duplexes, but different sugar moieties do not induce a preference for a specific G4 topology. Interestingly, when monosaccharides were attached through a short ethylene linker to the NDI scaffold, their cellular uptake was two- to threefold more efficient than that when the sugar was directly attached through its anomeric position. Moreover, a correlation between more efficient cell uptake of these carb-NDIs and their higher toxicity in cancerous cell lines has been observed. Carb-NDIs seem to be mainly translocated into cancer cells through glucose transporters (GLUT), of which GLUT4 plays a major role.

d- Versus l-Glucose Conjugation: Mitochondrial Targeting of a Light-Activated Dual-Mode-of-Action Ruthenium-Based Anticancer Prodrug

Light-activated ruthenium polypyridyl anticancer prodrugs often suffer from poor water solubility, poor selectivity, and/or ill-defined intracellular targets. Coordination of the d- or l-glucose thioether ligand 3 (2-(2-(2-(methylthio)ethoxy)ethoxy)ethyl-β-glucopyranoside) to the highly lipophilic ruthenium complex [Ru(tpy)(dppn)(H2 O)]2+ ([1]2+ ; dppn=benzo[i]dipyrido-[3,2-a:2',3'-c]phenazine, tpy=2,2':6',2''-terpyridine) solved all these problems at once. The two enantiomers of [Ru(tpy)(dppn)(3)][PF6 ]2 , [d-2][PF6 ]2 and [l-2][PF6 ]2 , were soluble in water, which allowed the influence of the chirality of the glucose moiety on uptake, toxicity, and intracellular localization of the prodrug to be probed without changing any other physicochemical properties. Both compounds showed mild, but different, cytotoxicity in A549 (human lung carcinoma) and MCF-7 (human breast adenocarcinoma) cancer cells in the dark, whereas following low doses of visible light irradiation (3.1 J cm-2 at λ = 454 nm), a similar, but high cytotoxicity (EC50 < 1 μm), was observed. Irrespective of the chirality, both slightly emissive Ru complexes were found in the mitochondria, and two modes of action may contribute to light-induced cell death: 1) the glucose thioether ligand is photosubstituted by water, thus [1]2+ , which interacts with DNA at an exceptionally high 400:1 base pair/Ru ratio, is released; 2) both [1]2+ and [2]2+ produce massive amounts of singlet oxygen, which leads to very efficient photodynamic DNA cleavage.

Emerging concepts of T cell metabolism as a target of immunotherapy

T cells have a pivotal protective role in defense against infection and cancer but also are instrumental in the development of many autoimmune diseases. The regulation of nutrient uptake and utilization in T cells is critically important for the control of their differentiation, and manipulating metabolic pathways in these cells can alter their function and longevity. While the importance of T cell metabolic remodeling in different physiological settings is not fully understood, there is a growing realization that inappropriate metabolic remodeling underlies many aberrant immune responses and that manipulating cellular metabolism can beneficially enhance or temper immunity. Here we comment on the basic metabolic pathways in T cells, followed by a discussion on up-to-date findings about the relationship between metabolism and T cell function and longevity. Furthermore, we expand on potential approaches and applications in which T cells might be manipulated by the reprogramming of metabolic pathways for therapeutic purposes.

Anticancer agents interacting with membrane glucose transporters

The altered metabolism observed in cancer cells generally consists in increased glucose uptake and glycolytic activity. This is associated with an overexpression of glucose transporter proteins (GLUTs), which facilitate glucose uptake across the plasma membrane and play a crucial role in the survival of cancer cells. Therefore GLUTs are considered as suitable targets for the treatment of cancer. Herein we review some of the most relevant GLUT inhibitors that have been recently developed as prospective anticancer agents.

Recent Advances in Biosensing With Photonic Crystal Surfaces: A Review

Photonic crystal surfaces that are designed to function as wavelength-selective optical resonators have become a widely adopted platform for label-free biosensing, and for enhancement of the output of photon-emitting tags used throughout life science research and in vitro diagnostics. While some applications, such as analysis of drug-protein interactions, require extremely high resolution and the ability to accurately correct for measurement artifacts, others require sensitivity that is high enough for detection of disease biomarkers in serum with concentrations less than 1 pg/ml. As the analysis of cells becomes increasingly important for studying the behavior of stem cells, cancer cells, and biofilms under a variety of conditions, approaches that enable high resolution imaging of live cells without cytotoxic stains or photobleachable fluorescent dyes are providing new tools to biologists who seek to observe individual cells over extended time periods. This paper will review several recent advances in photonic crystal biosensor detection instrumentation and device structures that are being applied towards direct detection of small molecules in the context of high throughput drug screening, photonic crystal fluorescence enhancement as utilized for high sensitivity multiplexed cancer biomarker detection, and label-free high resolution imaging of cells and individual nanoparticles as a new tool for life science research and single-molecule diagnostics.

Glucose-bearing biodegradable poly(amino acid) and poly(amino acid)-poly(ester) conjugates for controlled payload release

The glucoseamine-initiated ring-opening polymerisation of amino acid N-carboxyanhydrides and O-carboxanhydrides to yield amphiphilic block copolymers that are capable of self-assembly in aqueous solution to form well-defined, glucose-presenting, particles is reported.

Lactate dehydrogenase-A inhibition induces human glioblastoma multiforme stem cell differentiation and death

Therapies that target the signal transduction and metabolic pathways of cancer stem cells (CSCs) are innovative strategies to effectively reduce the recurrence and significantly improve the outcome of glioblastoma multiforme (GBM). CSCs exhibit an increased rate of glycolysis, thus rendering them intrinsically more sensitive to prospective therapeutic strategies based on the inhibition of the glycolytic pathway. The enzyme lactate dehydrogenase-A (LDH-A), which catalyses the interconversion of pyruvate and lactate, is up-regulated in human cancers, including GBM. Although several papers have explored the benefits of targeting cancer metabolism in GBM, the effects of direct LDH-A inhibition in glial tumours have not yet been investigated, particularly in the stem cell subpopulation. Here, two representative LDH-A inhibitors (NHI-1 and NHI-2) were studied in GBM-derived CSCs and compared to differentiated tumour cells. LDH-A inhibition was particularly effective in CSCs isolated from different GBM cell lines, where the two compounds blocked CSC formation and elicited long-lasting effects by triggering both apoptosis and cellular differentiation. These data demonstrate that GBM, particularly the stem cell subpopulation, is sensitive to glycolytic inhibition and shed light on the therapeutic potential of LDH-A inhibitors in this tumour type.

Recent Update on Human Lactate Dehydrogenase Enzyme 5 (hLDH5) Inhibitors: A Promising Approach for Cancer Chemotherapy

Human lactate dehydrogenase (hLDH5), a glycolytic enzyme responsible for the conversion of pyruvate to lactate coupled with oxidation of NADH to NAD(+), plays a crucial role in the promotion of glycolysis in invasive tumor cells. Recently, hLDH5 has been considered a vital therapeutic target for invasive cancers. Selective inhibition of hLDH5 using small molecules holds potential prospects for the treatment of cancer and associated diseases. Consequently, significant progress has been made in the discovery of selective small-molecule hLDH5 inhibitors displaying remarkable inhibitory potencies. The purpose of this review is to discuss briefly the roles of hLDH isoforms and to compile small hLDH5 inhibitors into groups based on their chemical classes and pharmacological applications.

Synthesis and biological evaluation of non-glucose glycoconjugated N-hydroyxindole class LDH inhibitors as anticancer agents

Inhibitors of human lactate dehydrogenase A (LDH-A) are promising therapeutic agents against cancer. The development of LDH-A inhibitors that possess cellular activities has so far proved to be particularly challenging, since the enzyme's active site is narrow and highly polar. In the recent past, we were able to develop a glucose-conjugated N-hydroxyindole-based LDH-A inhibitor designed to exploit the sugar avidity expressed by cancer cells (the Warburg effect). Herein we describe a structural modulation of the sugar moiety of this class of inhibitors, with the insertion of α-D-mannose, β-D-gulose, or β-N-acetyl-D-glucosamine portions in their structures. Their stereospecific chemical synthesis, which involves a substrate-dependent stereospecific glycosylation step, and their biological activity in reducing lactate production and proliferation in cancer cells are reported. Interestingly, the α-D-mannose conjugate displayed the best properties in the cellular assays, demonstrating an efficient antiglycolytic and antiproliferative activity in cancer cells.

Development and validation of a docking-based virtual screening platform for the identification of new lactate dehydrogenase inhibitors

The human muscle isoform of lactate dehydrogenase (hLDH5) is one of the key enzymes of the glycolytic process. It is overexpressed in metastatic cancer cells and is linked to the vitality of tumors in hypoxic conditions. With the aim of identifying new hLDH5 inhibitors, a fully automated docking-based virtual screening platform was developed by considering different protein conformations and the consensus docking strategy. In order to verify the reliability of the reported platform, a small database of about 10,000 compounds was filtered by using this method, and the top-ranked compounds were tested for their hLDH5 inhibition activity. Enzymatic assays revealed that, among the ten selected compounds, two proved to efficiently inhibit enzyme activity with IC₅₀ values in the micromolar range. These results demonstrate the validity of the methodologies we followed, encouraging the application of larger virtual screening studies and further refinements of the platform. Furthermore, the two active compounds herein described may be considered as interesting leads for the development of new and more efficient LDH inhibitors.

Targeting T cell metabolism for therapy

In the past several years a wealth of evidence has emerged illustrating how metabolism supports many aspects of T cell biology, as well as how metabolic changes drive T cell differentiation and fate. We outline developing principles in the regulation of T cell metabolism, and discuss how these processes are affected in settings of inflammation and cancer. In this context we discuss how metabolic pathways might be manipulated for the treatment of human disease, including how metabolism may be targeted to prevent T cell dysfunction in inhospitable microenvironments, to generate more effective adoptive cellular immunotherapies in cancer, and to direct T cell differentiation and function towards non-pathogenic phenotypes in settings of autoimmunity.

Detection of protein-small molecule binding using a self-referencing external cavity laser biosensor

High throughput screening of protein-small molecule binding interactions using label-free optical biosensors is challenging, as the detected signals are often similar in magnitude to experimental noise. Here, we describe a novel self-referencing external cavity laser (ECL) biosensor approach that achieves high resolution and high sensitivity, while eliminating thermal noise with sub-picometer wavelength accuracy. Using the self-referencing ECL biosensor, we demonstrate detection of binding between small molecules and a variety of immobilized protein targets with binding affinities or inhibition constants in the sub-nanomolar to low micromolar range. The demonstrated ability to perform detection in the presence of several interfering compounds opens the potential for increasing the throughput of the approach. As an example application, we performed a "needle-in-the-haystack" screen for inhibitors against carbonic anhydrase isozyme II (CA II), in which known inhibitors are clearly differentiated from inactive molecules within a compound library.

An update on therapeutic opportunities offered by cancer glycolytic metabolism

Almost all invasive cancers, regardless of tissue origin, are characterized by specific modifications of their cellular energy metabolism. In fact, a strong predominance of aerobic glycolysis over oxidative phosphorylation (Warburg effect) is usually associated with aggressive tumour phenotypes. This metabolic shift offers a survival advantage to cancer cells, since they may continue to produce energy and anabolites even when they are exposed to either transient or permanent hypoxic conditions. Moreover, it ensures a high production rate of glycolysis intermediates, useful as building blocks for fast cell proliferation of cancer cells. This peculiar metabolic profile may constitute an ideal target for therapeutic interventions that selectively hit cancer cells with minimal residual systemic toxicity. In this review we provide an update about some of the most recent advances in the discovery of new bioactive molecules that are able to interfere with cancer glycolysis.

Inhibitors of glucose transport and glycolysis as novel anticancer therapeutics

Metabolic reprogramming and altered energetics have become an emerging hallmark of cancer and an active area of basic, translational, and clinical cancer research in the recent decade. Development of effective anticancer therapeutics may depend on improved understanding of the altered cancer metabolism compared to that of normal cells. Changes in glucose transport and glycolysis, which are drastically upregulated in most cancers and termed the Warburg effect, are one of major focuses of this new research area. By taking advantage of the new knowledge and understanding of cancer’s mechanisms, numerous therapeutic agents have been developed to target proteins and enzymes involved in glucose transport and metabolism, with promising results in cancer cells, animal tumor models and even clinical trials. It has also been hypothesized that targeting a pathway or a process, such as glucose transport or glucose metabolism, rather than a specific protein or enzyme in a signaling pathway may be more effective. This is based on the observation that cancer somehow can always bypass the inhibition of a target drug by switching to a redundant or compensatory pathway. In addition, cancer cells have higher dependence on glucose. This review will provide background information on glucose transport and metabolism in cancer, and summarize new therapeutic developments in basic and translational research in these areas, with a focus on glucose transporter inhibitors and glycolysis inhibitors. The daunting challenges facing both basic and clinical researchers of the field are also presented and discussed.

Detection of protein-small molecule binding using a self-referencing external cavity laser biosensor

High-throughput screening has enabled the identification of small molecule modulators of important drug targets via well-established colorimetric or fluorimetric activity assays. However, existing methods to identify small molecule binders of nonenzymatic protein targets lack either the simplicity (e.g., require labeling one of the binding partners with a reporter) or throughput inherent in enzymatic assays widely used for HTS. Thus, there is intense interest in the development of high-throughput technologies for label-free detection of protein-small molecule interactions. Here we describe a novel self-referencing external cavity laser (ECL) biosensor approach that achieves high resolution and high sensitivity, while eliminating thermal noise with subpicometer wavelength accuracy. Using the self-referencing ECL biosensor, we demonstrate detection of binding between small molecules and a variety of immobilized protein targets, pairs that have binding affinities or inhibition constants ranging from subnanomolar to low micromolar. Finally, a "needle-in-the-haystack" screen for inhibitors against carbonic anhydrase isozyme II is performed, in which known inhibitors are clearly differentiated from inactive molecules within a compound library.

Smart nanodevice combined tumor-specific vector with cellular microenvironment-triggered property for highly effective antiglioma therapy

Malignant glioma, a highly aggressive tumor, is one of the deadliest types of cancer associated with dismal outcome despite optimal chemotherapeutic regimens. One explanation for this is the failure of most chemotherapeutics to accumulate in the tumors, additionally causing serious side effects in periphery. To solve these problems, we sought to develop a smart therapeutic nanodevice with cooperative dual characteristics of high tumor-targeting ability and selectively controlling drug deposition in tumor cells. This nanodevice was fabricated with a cross-linker, containing disulfide linkage to form an inner cellular microenvironment-responsive "-S-S-" barrier, which could shield the entrapped drug leaking in blood circulation. In addition, dehydroascorbic acid (DHA), a novel small molecular tumor-specific vector, was decorated on the nanodevice for tumor-specific recognition via GLUT1, a glucose transporter highly expressed on tumor cells. The drug-loaded nanodevice was supposed to maintain high integrity in the bloodstream and increasingly to specifically bind with tumor cells through the association of DHA with GLUT1. Once within the tumor cells, the drug release was triggered by a high level of intracellular glutathione. When these two features were combined, the smart nanodevice could markedly improve the drug tumor-targeting delivery efficiency, meanwhile decreasing systemic toxicity. Herein, this smart nanodevice showed promising potential as a powerful platform for highly effective antiglioma treatment.