3-Bromopyruvate induces necrotic cell death in sensitive melanoma cell lines

3-Bromopyruvate Suppresses the Malignant Phenotype of Vemurafenib-Resistant Melanoma Cells

(1) BRAF mutations are associated with high mortality and are a substantial factor in therapeutic decisions. Therapies targeting BRAF-mutated tumors, such as vemurafenib (PLX), have significantly improved the overall survival of melanoma patients. However, patient relapse and low response rates remain challenging, even with contemporary therapeutic alternatives. Highly proliferative tumors often rely on glycolysis to sustain their aggressive phenotype. 3-bromopyruvate (3BP) is a promising glycolysis inhibitor reported to mitigate resistance in tumors. This study aimed to evaluate the potential of 3BP as an antineoplastic agent for PLX-resistant melanoma treatment. (2) The effect of 3BP alone or in combination with PLX on viability, proliferation, colony formation, cell death, migration, invasion, epithelial-mesenchymal marker and metabolic protein expression, extracellular glucose and lactate, and reactive species were evaluated in two PLX-resistant melanoma cell lines. (3) 3BP treatment, which was more effective as monotherapy than combined with PLX, disturbed the metabolic and epithelial-mesenchymal profile of PLX-resistant cells, impairing their proliferation, migration, and invasion and triggering cell death. (4) 3BP monotherapy is a potent metabolic-disrupting agent against PLX-resistant melanomas, supporting the suppression of the malignant phenotype in this type of neoplasia.

Novel Hydrazone Derivatives of 3-Bromopyruvate: Synthesis, Evaluation of the Cytotoxic Effects, Molecular Docking and ADME Studies

A series of 3-bromopyruvate (3-BP) derivatives were synthesized to develop new potent anticancer agents. The chemical structures of the compounds were characterized using FT-IR, ¹ H-, ¹³ C-NMR spectroscopy, and elemental analysis (CHN). Their cytotoxic activities were investigated against four cancer cell lines, including colon (SW1116), breast (MDA-MB-231), lung (A549), and liver (HepG2) cancer cell lines. Among the synthesized compounds, 3b showed promising cytotoxic activity compared to 3-BP, with IC₅₀ values of 16.3 μM, 19.1 μM, 27.8 μM, and 14.5 μM against A549, MDA-MB-231, SW1116 and, HepG2 cell lines, respectively. Furthermore, the effect of these compounds on MCF-10A (a normal breast cell lines) was investigated to determine their selectivity between tumorigenic and non-tumorigenic cells. Since the 3-BP inhibits hexokinase II (HK II), molecular docking of 3-BP derivatives was carried out using AutoDock 4.2. The binding energies of these derivatives were greater than 3-BP, indicating that they had a higher affinity for HK II. For validation of docking, a 40 ns MD simulation was performed. SwissADME was used to predict pharmacokinetics, drug-likeness, and ADME parameters of the screened compounds. The results demonstrated that these derivatives are suitable candidates for developing orally potent HK II inhibitors.

Mitochondrial Respiratory Complexes as Targets of Drugs: The PPAR Agonist Example

Mitochondrial bioenergetics are progressively acquiring significant pathophysiological roles. Specifically, mitochondria in general and Electron Respiratory Chain in particular are gaining importance as unintentional targets of different drugs. The so-called PPAR ligands are a class of drugs which not only link and activate Peroxisome Proliferator-Activated Receptors but also show a myriad of extrareceptorial activities as well. In particular, they were shown to inhibit NADH coenzyme Q reductase. However, the molecular picture of this intriguing bioenergetic derangement has not yet been well defined. Using high resolution respirometry, both in permeabilized and intact HepG2 cells, and a proteomic approach, the mitochondrial bioenergetic damage induced by various PPAR ligands was evaluated. Results show a derangement of mitochondrial oxidative metabolism more complex than one related to a simple perturbation of complex I. In fact, a partial inhibition of mitochondrial NADH oxidation seems to be associated not only with hampered ATP synthesis but also with a significant reduction in respiratory control ratio, spare respiratory capacity, coupling efficiency and, last but not least, serious oxidative stress and structural damage to mitochondria.

Delphinidin Increases the Sensitivity of Ovarian Cancer Cell Lines to 3-Bromopyruvate

3-Bromopyruvic acid (3-BP) is a promising anticancer compound. Two ovary cancer (OC) cell lines, PEO1 and SKOV3, showed relatively high sensitivity to 3-BP (half maximal inhibitory concentration (IC₅₀) of 18.7 and 40.5 µM, respectively). However, the further sensitization of OC cells to 3-BP would be desirable. Delphinidin (D) has been reported to be cytotoxic for cancer cell lines. We found that D was the most toxic for PEO1 and SKOV3 cells from among several flavonoids tested. The combined action of 3-BP and D was mostly synergistic in PEO1 cells and mostly weakly antagonistic in SKOV3 cells. The viability of MRC-5 fibroblasts was not affected by both compounds at concentrations of up to 100 µM. The combined action of 3-BP and D decreased the level of ATP and of dihydroethidium (DHE)-detectable reactive oxygen species (ROS), cellular mobility and cell staining with phalloidin and Mitotracker Red in both cell lines but increased the 2’,7’-dichlorofluorescein (DCFDA)-detectable ROS level and decreased the mitochondrial membrane potential and mitochondrial mass only in PEO1 cells. The glutathione level was increased by 3-BP+D only in SKOV3 cells. These differences may contribute to the lower sensitivity of SKOV3 cells to 3-BP+D. Our results point to the possibility of sensitization of at least some OC cells to 3-BP by D.

3-Bromopyruvate regulates the status of glycolysis and BCNU sensitivity in human hepatocellular carcinoma cells

Chloroethylnitrosoureas (CENUs) are bifunctional antitumor alkylating agents, which exert their antitumor activity through inducing the formation of dG-dC interstrand crosslinks (ICLs) within DNA double strand. However, the complex process of tumor biology enables tumor cells to escape the killing triggered by CENUs, as for instance with the detoxifying activity of O⁶-methylguanine DNA methyltransferase (MGMT) to accomplish DNA damage repair. Considering the fact that most tumor cells highly depend on aerobic glycolysis to provide energy for survival even in the presence of oxygen (Warburg effect), inhibition of aerobic glycolysis may be an attractive strategy to overcome the resistance and improve the chemotherapeutic effects of CENUs. Especially, 3-bromopyruvate (3-BrPA), a small molecule alkylating agent, has been emerged as an effective glycolytic inhibitor (energy blocker) in cancer treatment. In view of its tumor specificity and inhibition on cellular multiple targets, it is likely to reduce the chemoresistance when chemotherapeutic drugs are combined with 3-BrPA. In this study, we investigated the effects of 3-BrPA on the chemosensitivity of two human hepatocellular carcinoma (HCC) cell lines to the cytotoxic effects of l,3-bis(2-chloroethyl)-1-nitrosourea (BCNU) and the underlying molecular mechanism. The sensitivity of SMMC-7721 and HepG2 cells to BCNU was significantly increased by 2 h pretreatment with micromolar dosage of 3-BrPA. Moreover, 3-BrPA decreased the cellular ATP and GSH levels, and extracellular lactate excreted by tumor cells, and the effects were more effective when 3-BrPA was combined with BCNU. Cellular hexokinase-II (HK-II) activity was also reduced after exposure to the treatment of 3-BrPA plus BCNU. Based on the above results, the effects of 3-BrPA on the formation of dG-dC ICLs induced by BCNU was investigated by stable isotope dilution high-performance liquid chromatography electrospray ionization tandem mass spectrometry (HPLC-ESI-MS/MS). The results indicated that BCNU produced higher levels of dG-dC ICLs in SMMC-7721 and HepG2 cells pretreated with 3-BrPA compared to that without 3-BrPA pretreatment. Notably, in MGMT-deficient HepG2 cells, the levels of dG-dC ICLs were significantly higher than MGMT-proficient SMMC-7721 cells. In general, these findings revealed that 3-BrPA, as an effective glycolytic inhibitor, may be considered as a potential clinical chemosensitizer to optimize the therapeutic index of CENUs.

Metastatic prostate cancer cells are highly sensitive to 3-bromopyruvic acid

AIMS

3-Bromopyruvate (3-BP), an alkylating agent and a glycolytic inhibitor, is a promising anticancer agent, which can be efficient also against multidrug-resistant cancer cells. The aim of this study was to examine how 3-BP affects the survival and mobility of rat (MAT-LyLu and AT-2) and human (DU-145 and PC-3) metastatic prostate cancer cell lines.

MAIN METHODS

Cytotoxicity was estimated with Neutral Red. Cell mobility was analyzed by time-lapse microscopic monitoring of trajectories of individual cells at 5-min intervals for 6h. ATP was estimated with luciferin/luciferase and glutathione (GSH) with o-phthalaldehyde. Actin cytoskeleton was visualized with phalloidin conjugated with Atto-488.

KEY FINDINGS

All metastatic prostate cell lines studied were very sensitive to 3-BP (IC₅₀ of 4-26μM). 3-Bromopyruvate drastically reduced cell movement even at concentrations of 5-10μM after 1h treatment. This compound depleted also cellular ATP and GSH, and disrupted actin cytoskeleton.

SIGNIFICANCE

The data obtained suggest that 3-BP can potentially be useful for treatment of metastatic prostate cancer and, especially, be efficient in limiting metastasis.

Tumor Energy Metabolism and Potential of 3-Bromopyruvate as an Inhibitor of Aerobic Glycolysis: Implications in Tumor Treatment

Tumor formation and growth depend on various biological metabolism processes that are distinctly different with normal tissues. Abnormal energy metabolism is one of the typical characteristics of tumors. It has been proven that most tumor cells highly rely on aerobic glycolysis to obtain energy rather than mitochondrial oxidative phosphorylation (OXPHOS) even in the presence of oxygen, a phenomenon called “Warburg effect”. Thus, inhibition of aerobic glycolysis becomes an attractive strategy to specifically kill tumor cells, while normal cells remain unaffected. In recent years, a small molecule alkylating agent, 3-bromopyruvate (3-BrPA), being an effective glycolytic inhibitor, has shown great potential as a promising antitumor drug. Not only it targets glycolysis process, but also inhibits mitochondrial OXPHOS in tumor cells. Excellent antitumor effects of 3-BrPA were observed in cultured cells and tumor-bearing animal models. In this review, we described the energy metabolic pathways of tumor cells, mechanism of action and cellular targets of 3-BrPA, antitumor effects, and the underlying mechanism of 3-BrPA alone or in combination with other antitumor drugs (e.g., cisplatin, doxorubicin, daunorubicin, 5-fluorouracil, etc.) in vitro and in vivo. In addition, few human case studies of 3-BrPA were also involved. Finally, the novel chemotherapeutic strategies of 3-BrPA, including wafer, liposomal nanoparticle, aerosol, and conjugate formulations, were also discussed for future clinical application.

The antimetabolite 3-bromopyruvate selectively inhibits Staphylococcus aureus

Increased antibacterial resistance jeopardizes current therapeutic strategies to control infections, soliciting the development of novel antibacterial drugs with new mechanisms of action. This study reports the discovery of potent and selective antistaphylococcal activity of 3-bromopyruvate (3BP), an antimetabolite in preclinical development as an anticancer drug. 3BP showed bactericidal activity against Staphylococcus aureus, with active concentrations comparable with those reported to be effective against cancer cells. In contrast, no relevant activity was observed against other ESKAPE bacteria (Enterococcus faecium, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa and Enterobacter spp.). The antistaphylococcal activity of 3BP was confirmed using a panel of human and veterinary strains, including multi-drug-resistant isolates. 3BP showed highest antibacterial activity under conditions that increase its stability (acidic pH) or promote S. aureus fermentative metabolism (anaerobiosis), although 3BP was also able to kill metabolically inactive cells. 3BP showed synergism with gentamicin, and also disrupted preformed S. aureus biofilms at concentrations only slightly higher than those inhibiting planktonic cells. This study unravels novel antibacterial and antibiofilm activities for the anticancer drug 3BP, paving the way for further preclinical studies.

Bioorthogonal Profiling of a Cancer Cell Proteome Identifies a Large Set of 3-Bromopyruvate Targets beyond Glycolysis

3-Bromopyruvate (3BP) is a potential anticancer agent viewed as a glycolytic inhibitor that preferentially kills cancer cells through inhibition of glyceraldehyde 3-phosphate dehydrogenase (GAPDH), resulting in severe energy depletion. We previously identified four cysteine residues in GAPDH that are alkylated by 3BP, resulting in its inactivation. However, we also showed that addition of excess pyruvate, the final product of glycolysis, was unable to rescue cells from 3BP treatment. This result indicates that GAPDH may not be the only relevant target and is consistent with the chemical reactivity of 3BP that should result in the modification of cysteine residues in many different proteins. To directly test this hypothesis, we first synthesized a probe of 3BP activity bearing an alkyne functionality, termed AO3BP, and then demonstrated that this probe could modify a variety of proteins in living cells. Subsequent competition of AO3BP labeling with pretreatment by 3BP identified 62 statistically significant proteins of various functions as targets of 3BP, confirming that 3BP labeling is indeed widespread. We conclude that 3BP's cytotoxic impact on cancer cells does not only result from selective inhibition of glycolysis but rather from a more widespread effect on cellular proteins that could be driven by the pharmacokinetics of the 3BP. These pleiotropic consequences should be considered when thinking about the potential toxicity of this highly reactive compound.

Enhancing anticancer effects, decreasing risks and solving practical problems facing 3-bromopyruvate in clinical oncology: 10 years of research experience

3-Bromopyruvate (3BP) is a promising powerful general anticancer agent. Unfortunately, 3BP release faces many practical and biochemical problems in clinical human oncology, for example, 3BP induces burning venous sensation (during intravenous infusion) and rapid inactivation by thiol groups of glutathione and proteins. 3BP exhibits resistance in glutathione-rich tumors without being able to exert selective targeting. 3BP does not cross the blood–brain barrier and cannot treat nervous system tumors. Importantly, 3BP cannot persist in tumor tissues due to the phenomenon of enhanced permeability and retention effect. Here, the author presents the practical solutions for clinical problems facing 3BP use in clinical oncology, based on over 10 years of experience in 3BP research. Crude (unformulated 3BP that is purchased from chemical companies without being formulated in liposomes or other nanocarriers) should not be administered in clinical oncology. Instead, 3BP is better formulated with liposomes, polyethylene glycol (PEG), PEGylated liposomes (stealth liposomes) or perillyl alcohol that are used currently with many chemotherapeutics for treating clinical tumors in cancer patients. Formulating 3BP with targeted liposomes, for example, with folate, transferrin or other ligands, improves tumor targeting. Formulating 3BP with liposomes, PEG, stealth liposomes or perillyl alcohol may improve its pharmacokinetics, hide it from thiols in the circulation, protect it from serum proteins and enzymes, prevent burning sensation, prolong 3BP’s longevity and facilitate crossing the BBB. Formulating 3BP with stealth liposomes protects 3BP from the reticuloendothelial cells. Liposomal 3BP formulations may retain 3BP better inside the relatively large tumor capillary pores (abolish enhanced permeability and retention effect) sparing normal tissues, facilitate new delivery routes for 3BP (eg, topical and intranasal 3BP administration using perillyl alcohol) and improve cancer cytotoxicity. Formulating 3BP may be promising in overcoming many obstacles in clinical oncology.

A perillyl alcohol-conjugated analog of 3-bromopyruvate without cellular uptake dependency on monocarboxylate transporter 1 and with activity in 3-BP-resistant tumor cells

The anticancer agent 3-bromopyruvate (3-BP) is viewed as a glycolytic inhibitor that preferentially kills glycolytic cancer cells through energy depletion. However, its cytotoxic activity is dependent on cellular drug import through transmembrane monocarboxylate transporter 1 (MCT-1), which restricts its anticancer potential to MCT-1-positive tumor cells. We created and characterized an MCT-1-independent analog of 3-BP, called NEO218. NEO218 was synthesized by covalently conjugating 3-BP to perillyl alcohol (POH), a natural monoterpene. The responses of various tumor cell lines to treatment with either compound were characterized in the presence or absence of supplemental pyruvate or antioxidants N-acetyl-cysteine (NAC) and glutathione (GSH). Drug effects on glyceraldehyde 3-phosphate dehydrogenase (GAPDH) enzyme activity were investigated by mass spectrometric analysis. The development of 3-BP resistance was investigated in MCT-1-positive HCT116 colon carcinoma cells in vitro. Our results show that NEO218: (i) pyruvylated GAPDH on all 4 of its cysteine residues and shut down enzymatic activity; (ii) severely lowered cellular ATP content below life-sustaining levels, and (iii) triggered rapid necrosis. Intriguingly, supplemental antioxidants effectively prevented cytotoxic activity of NEO218 as well as 3-BP, but supplemental pyruvate powerfully protected cells only from 3-BP, not from NEO218. Unlike 3-BP, NEO218 exerted its potent cytotoxic activity irrespective of cellular MCT-1 status. Treatment of HCT116 cells with 3-BP resulted in prompt development of resistance, based on the emergence of MCT-1-negative cells. This was not the case with NEO218, and highly 3-BP-resistant cells remained exquisitely sensitive to NEO218. Thus, our study identifies a mechanism by which tumor cells develop rapid resistance to 3-BP, and presents NEO218 as a superior agent not subject to this cellular defense. Furthermore, our results offer alternative interpretations of previously published models on the role of supplemental antioxidants: Rather than quenching reactive oxygen species (ROS), supplemental NAC or GSH directly interact with 3-BP, thereby neutralizing the drug's cytotoxic potential before it can trigger ROS production. Altogether, our study introduces new aspects of the cytotoxic mechanism of 3-BP, and characterizes NEO218 as an analog able to overcome a key cellular defense mechanism towards this drug.

Mycoepoxydiene suppresses HeLa cell growth by inhibiting glycolysis and the pentose phosphate pathway

Upregulation of glycolysis and the pentose phosphate pathway (PPP) is a major characteristic of the metabolic reprogramming of cancer and provides cancer cells with energy and vital metabolites to support their rapid proliferation. Targeting glycolysis and the PPP has emerged as a promising antitumor therapeutic strategy. Marine natural products are attractive sources for anticancer therapeutics, as evidenced by the antitumor drug Yondelis. Mycoepoxydiene (MED) is a natural product isolated from a marine fungus that has shown promising inhibitory efficacy against HeLa cells in vitro. We used a proteomic approach with two-dimensional gel electrophoresis (2-DE) coupled with mass spectrometry to explore the cellular targets of MED and to unravel the molecular mechanisms underlying the antitumor activity of MED in HeLa cells. Our proteomic data showed that triosephosphate isomerase (TPI) and 6-phosphogluconolactonase (PGLS), which participate in glycolysis and the PPP, respectively, were significantly downregulated by MED treatment. Functional studies revealed that the expression levels of several other enzymes involved in glycolysis and the PPP, including hexokinase 2 (HK2), phosphofructokinase 1 (PFKM), aldolase A (ALDOA), enolase 1 (ENO1), lactate dehydrogenase A (LDHA), and glucose-6-phosphate dehydrogenase (G6PD), were also reduced in a dose-dependent manner. Moreover, the LDHA and G6PD enzymatic activities in HeLa cells were inhibited by MED, and overexpression of these downregulated enzymes rescued HeLa cells from the growth inhibition induced by MED. Our data suggest that MED suppresses HeLa cell growth by inhibiting glycolysis and the PPP, which provides a mechanistic basis for the development of new therapeutics against cervical cancer.

The anticancer agent 3-bromopyruvate: a simple but powerful molecule taken from the lab to the bedside

At the beginning of the twenty-first century, 3-bromopyruvate (3BP), a simple alkylating chemical compound was presented to the scientific community as a potent anticancer agent, able to cause rapid toxicity to cancer cells without bystander effects on normal tissues. The altered metabolism of cancers, an essential hallmark for their progression, also became their Achilles heel by facilitating 3BP's selective entry and specific targeting. Treatment with 3BP has been administered in several cancer type models both in vitro and in vivo, either alone or in combination with other anticancer therapeutic approaches. These studies clearly demonstrate 3BP's broad action against multiple cancer types. Clinical trials using 3BP are needed to further support its anticancer efficacy against multiple cancer types thus making it available to more than 30 million patients living with cancer worldwide. This review discusses current knowledge about 3BP related to cancer and discusses also the possibility of its use in future clinical applications as it relates to safety and treatment issues.

Hexokinase 2 is a determinant of neuroblastoma metastasis

Background:

Intersecting a genome-wide expression profile of metastatic and nonmetastatic human neuroblastoma xenograft variants with expression profiles of tumours from stage 1 and 4 neuroblastoma patients, we previously characterised hexokinase 2 (HK2) as a gene whose expression was upregulated in both metastatic neuroblastoma variants and tumours from stage 4 neuroblastoma patients.

Methods:

Local and metastatic neuroblastoma cell variants as well as metastatic neuroblastoma cells genetically manipulated to downregulate the expression of HK2 were utilised for in vitro and in vivo examinations of the involvement of HK2 in neuroblastoma.

Results:

Hexokinase 2 expression and its activity levels were increased in neuroblastoma metastatic variants as compared with the local variants. The upregulation of HK2 confers upon the metastatic cells high resistance to the antiproliferative effect of the HK2 inhibitor 3-BrPa and to the chemotherapy agent Deferoxamine. The inhibition of HK2 transcript lowered the proliferation and motility of sh-HK2 cells as compared with sh-control cells. Mice that were inoculated with sh-HK2 cells had a lower incidence of local tumours, smaller tumour volumes and a diminished load of lung metastasis compared with mice inoculated with sh-control cells.

Conclusions:

Hexokinase 2 plays a significant role in shaping the malignant phenotype of neuroblastoma and influences the progression of this disease.

Anticancer agent 3-bromopyruvic acid forms a conjugate with glutathione

BACKGROUND

3-Bromopyruvic acid (3-BP), a glycolytic inhibitor and a promising anticancer compound, induces oxidative stress and depletes cells of glutathione (GSH). The causes of GSH loss remain unclear. The aim of this study was to ascertain whether 3-BP forms a conjugate with glutathione.

METHODS

GSH was incubated with various amounts of 3-BP and the extent of reaction was titrated with (1)H NMR and (1)H-(1)H NMR. The reaction outcome was identified by MS/MS. Intracellular formation of the conjugate was assessed in cells treated with 3-BP and 3-BP((13)C) and analyzed using the targeted LC-MS/MS method in negative ionization MRM mode.

RESULTS

3-BP was found to react with GSH in a 1:1 ratio forming an S-conjugate. The same conjugate was formed intracellularly in erythrocytes and MCF-7 cells.

CONCLUSIONS

3-BP reacts with GSH in the absence of cells and intracellularly. This reaction appears to be the main cause of GSH loss in 3-BP treated cells.

3-Bromopyruvate induces rapid human prostate cancer cell death by affecting cell energy metabolism, GSH pool and the glyoxalase system

3-bromopyruvate (3-BP) is an anti-tumour drug effective on hepatocellular carcinoma and other tumour cell types, which affects both glycolytic and mitochondrial targets, depleting cellular ATP pool. Here we tested 3-BP on human prostate cancer cells showing, differently from other tumour types, efficient ATP production and functional mitochondrial metabolism. We found that 3-BP rapidly induced cultured androgen-insensitive (PC-3) and androgen-responsive (LNCaP) prostate cancer cell death at low concentrations (IC(50) values of 50 and 70 μM, respectively) with a multimodal mechanism of action. In particular, 3-BP-treated PC-3 cells showed a selective, strong reduction of glyceraldeide 3-phosphate dehydrogenase activity, due to the direct interaction of the drug with the enzyme. Moreover, 3-BP strongly impaired both glutamate/malate- and succinate-dependent mitochondrial respiration, membrane potential generation and ATP synthesis, concomitant with the inhibition of respiratory chain complex I, II and ATP synthase activities. The drastic reduction of cellular ATP levels and depletion of GSH pool, associated with significant increase in cell oxidative stress, were found after 3-BP treatment of PC-3 cells. Interestingly, the activity of both glyoxalase I and II, devoted to the elimination of the cytotoxic methylglyoxal, was strongly inhibited by 3-BP. Both N-acetylcysteine and aminoguanidine, GSH precursor and methylglyoxal scavenger, respectively, prevented 3-BP-induced PC-3 cell death, showing that impaired cell antioxidant and detoxifying capacities are crucial events leading to cell death. The provided information on the multi-target cytotoxic action of 3-BP, finally leading to PC-3 cell necrosis, might be useful for future development of 3-BP as a therapeutic option for prostate cancer treatment.

The energy blockers bromopyruvate and lonidamine lead GL15 glioblastoma cells to death by different p53-dependent routes

The energy metabolism of tumor cells relies on aerobic glycolysis rather than mitochondrial oxidation. This difference between normal and cancer cells provides a biochemical basis for new therapeutic strategies aimed to block the energy power plants of cells. The effects produced by the energy blockers bromopyruvate (3BP) and lonidamine (LND) and the underlying biochemical mechanisms were investigated in GL15 glioblastoma cells. 3BP exerts early effects compared to LND, even though both drugs lead cells to death but by different routes. A dramatic decrease of ATP levels occurred after 1 hour treatment with 3BP, followed by cytochrome c and hexokinase II degradation, and by the decrease of both LC3I/LC3II ratio and p62, markers of an autophagic flux. In addition, Akt(Ser(473)) and p53(Ser(15)/Ser(315)) dephosphorylation occurred. In LND treatment, sustained ATP cellular levels were maintained up to 40 hours. The autophagic response of cells was overcome by apoptosis that was preceded by phosphatidylinositol disappearance and pAkt decrease. This last event favored p53 translocation to mitochondria triggering a p53-dependent apoptotic route, as observed at 48 and 72 hours. Adversely, in 3BP treatment, phospho-p53 dephosphorylation targeted p53 to MDM2-dependent proteolysis, thus channeling cells to irreversible autophagy.

Differentiate or Die: 3-Bromopyruvate and Pluripotency in Mouse Embryonic Stem Cells

Background

Pluripotent embryonic stem cells grown under standard conditions (ESC) have a markedly glycolytic profile, which is shared with many different types of cancer cells. Thus, some therapeutic strategies suggest that pharmacologically shifting cancer cells towards an oxidative phenotype, using glycolysis inhibitors, may reduce cancer aggressiveness. Given the metabolic parallels between cancer and stemness would chemotherapeutical agents have an effect on pluripotency, and could a strategy involving these agents be envisioned to modulate stem cell fate in an accessible manner? In this manuscript we attempted to determine the effects of 3-bromopyruvate (3BrP) in pluripotency. Although it has other intracellular targets, this compound is a potent inhibitor of glycolysis enzymes thought to be important to maintain a glycolytic profile. The goal was also to determine if we could contribute towards a pharmacologically accessible metabolic strategy to influence cell differentiation.

Methodology/Principal Findings

Mouse embryonic stem cells (mESC) grown under standard pluripotency conditions (in the presence of Leukemia Inducing Factor- LIF) were treated with 3BrP. As a positive control for differentiation other mESCs were grown without LIF. Overall our results demonstrate that 3BrP negatively affects pluripotency, forcing cells to become less glycolytic and with more active mitochondria. These changes in metabolism are correlated with increased differentiation, even under pluripotency conditions (i.e. in the presence of LIF). However, 3BrP also significantly impaired cell function, and may have other roles besides affecting the metabolic profile of mESCs.

Conclusions/Findings

Treatment of mESCs with 3BrP triggered a metabolic switch and loss of pluripotency, even in the presence of LIF. Interestingly, the positive control for differentiation allowed for a distinction between 3BrP effects and changes associated with spontaneous differentiation/loss of pluripotency in the absence of LIF. Additionally, there was a slight differentiation bias towards mesoderm in the presence of 3BrP. However, the side effects on cellular function suggest that the use of this drug is probably not adequate to efficiently push cells towards specific differentiation fates.

Killing multiple myeloma cells with the small molecule 3-bromopyruvate: implications for therapy

The small molecule 3-bromopyruvate (3-BP), which has emerged recently as the first member of a new class of potent anticancer agents, was tested for its capacity to kill multiple myeloma (MM) cancer cells. Human MM cells (RPMI 8226) begin to lose viability significantly within 8 h of incubation in the presence of 3-BP. The Km (0.3 mmol/l) for intracellular accumulation of 3-BP in MM cells is 24 times lower than that in control cells (7.2 mmol/l). Therefore, the uptake of 3-BP by MM cells is significantly higher than that by peripheral blood mononuclear cells. Further, the IC50 values for human MM cells and control peripheral blood mononuclear cells are 24 and 58 µmol/l, respectively. Therefore, specificity and selectivity of 3-BP toward MM cancer cells are evident on the basis of the above. In MM cells the transcription levels of the gene encoding the monocarboxylate transporter MCT1 is significantly amplified compared with control cells. The level of intracellular ATP in MM cells decreases by over 90% within 1 h after addition of 100 µmol/l 3-BP. The cytotoxicity of 3-BP, exemplified by a marked decrease in viability of MM cells, is potentiated by the inhibitor of glutathione synthesis buthionine sulfoximine. In addition, the lack of mutagenicity and its superior capacity relative to Glivec to kill MM cancer cells are presented in this study.

3-Bromopyruvate induces apoptosis in breast cancer cells by downregulating Mcl-1 through the PI3K/Akt signaling pathway

The hexokinase inhibitor 3-bromopyruvate (3-BrPA) can inhibit glycolysis in tumor cells to reduce ATP production, resulting in apoptosis. However, as 3-BrPA is an alkylating agent, its cytotoxic action may be induced by other molecular mechanisms. The results presented here reveal that 3-BrPA-induced apoptosis is caspase independent. Further, 3-BrPA induces the generation of reactive oxygen species in MDA-MB-231 cells, leading to mitochondria-mediated apoptosis. These results suggest that caspase-independent apoptosis may be induced by the generation of reactive oxygen species. In this study, we also demonstrated that 3-BrPA induces apoptosis through the downregulation of myeloid cell leukemia-1 (Mcl-1) in MDA-MB-231 breast cancer cells. The results of Mcl-1 knockdown indicate that Mcl-1 plays an important role in 3-BrPA-induced apoptosis. Further, the upregulation of Mcl-1 expression in 3-BrPA-treated MDA-MB-231 cells significantly increases cell viability. In addition, 3-BrPA treatment resulted in the downregulation of p-Akt, suggesting that 3-BrPA may downregulate Mcl-1 through the phosphoinositide-3-kinase/Akt pathway. These findings indicate that 3-BrPA induces apoptosis in breast cancer cells by downregulating Mcl-1 through the phosphoinositide-3-kinase/Akt signaling pathway.

Metabolic vulnerabilities in endometrial cancer

Women with metabolic disorders, including obesity and diabetes, have an increased risk of developing endometrial cancer. However, the metabolism of endometrial tumors themselves has been largely understudied. Comparing human endometrial tumors and cells with their nonmalignant counterparts, we found that upregulation of the glucose transporter GLUT6 was more closely associated with the cancer phenotype than other hallmark cancer genes, including hexokinase 2 and pyruvate kinase M2. Importantly, suppression of GLUT6 expression inhibited glycolysis and survival of endometrial cancer cells. Glycolysis and lipogenesis were also highly coupled with the cancer phenotype in patient samples and cells. To test whether targeting endometrial cancer metabolism could be exploited as a therapeutic strategy, we screened a panel of compounds known to target diverse metabolic pathways in endometrial cells. We identified that the glycolytic inhibitor, 3-bromopyruvate, is a powerful antagonist of lipogenesis through pyruvylation of CoA. We also provide evidence that 3-bromopyruvate promotes cell death via a necrotic mechanism that does not involve reactive oxygen species and that 3-bromopyruvate impaired the growth of endometrial cancer xenografts.

Safety and outcome of treatment of metastatic melanoma using 3-bromopyruvate: a concise literature review and case study

3-Bromopyruvate (3BP) is a new, promising anticancer alkylating agent with several notable functions. In addition to inhibiting key glycolysis enzymes including hexokinase II and lactate dehydrogenase (LDH), 3BP also selectively inhibits mitochondrial oxidative phosphorylation, angiogenesis, and energy production in cancer cells. Moreover, 3BP induces hydrogen peroxide generation in cancer cells (oxidative stress effect) and competes with the LDH substrates pyruvate and lactate. There is only one published human clinical study showing that 3BP was effective in treating fibrolamellar hepatocellular carcinoma. LDH is a good measure for tumor evaluation and predicts the outcome of treatment better than the presence of a residual tumor mass. According to the Warburg effect, LDH is responsible for lactate synthesis, which facilitates cancer cell survival, progression, aggressiveness, metastasis, and angiogenesis. Lactate produced through LDH activity fuels aerobic cell populations inside tumors via metabolic symbiosis. In melanoma, the most deadly skin cancer, 3BP induced necrotic cell death in sensitive cells, whereas high glutathione (GSH) content made other melanoma cells resistant to 3BP. Concurrent use of a GSH depletor with 3BP killed resistant melanoma cells. Survival of melanoma patients was inversely associated with high serum LDH levels, which was reported to be highly predictive of melanoma treatment in randomized clinical trials. Here, we report a 28-year-old man presented with stage IV metastatic melanoma affecting the back, left pleura, and lung. The disease caused total destruction of the left lung and a high serum LDH level (4,283 U/L). After ethics committee approval and written patient consent, the patient received 3BP intravenous infusions (1-2.2 mg/kg), but the anticancer effect was minimal as indicated by a high serum LDH level. This may have been due to high tumor GSH content. On combining oral paracetamol, which depletes tumor GSH, with 3BP treatment, serum LDH level dropped maximally. Although a slow intravenous infusion of 3BP appeared to have minimal cytotoxicity, its anticancer efficacy via this delivery method was low. This was possibly due to high tumor GSH content, which was increased after concurrent use of the GSH depletor paracetamol. If the anticancer effectiveness of 3BP is less than expected, the combination with paracetamol may be needed to sensitize cancer cells to 3BP-induced effects.

Regulation of death induction and chemosensitizing action of 3-bromopyruvate in myeloid leukemia cells: energy depletion, oxidative stress, and protein kinase activity modulation

3-Bromopyruvate (3-BrP) is an alkylating, energy-depleting drug that is of interest in antitumor therapies, although the mechanisms underlying its cytotoxicity are ill-defined. We show here that 3-BrP causes concentration-dependent cell death of HL60 and other human myeloid leukemia cells, inducing both apoptosis and necrosis at 20-30 μM and a pure necrotic response at 60 μM. Low concentrations of 3-BrP (10-20 μM) brought about a rapid inhibition of glycolysis, which at higher concentrations was followed by the inhibition of mitochondrial respiration. The combination of these effects causes concentration-dependent ATP depletion, although this cannot explain the lethality at intermediate 3-BrP concentrations (20-30 μM). The oxidative stress caused by exposure to 3-BrP was evident as a moderate overproduction of reactive oxygen species and a concentration-dependent depletion of glutathione, which was an important determinant of 3-BrP toxicity. In addition, 3-BrP caused glutathione-dependent stimulation of p38 mitogen-activated protein kinase (MAPK), mitogen-induced extracellular kinase (MEK)/extracellular signal-regulated kinase (ERK), and protein kinase B (Akt)/mammalian target of rapamycin/p70S6K phosphorylation or activation, as well as rapid LKB-1/AMP kinase (AMPK) activation, which was later followed by Akt-mediated inactivation. Experiments with pharmacological inhibitors revealed that p38 MAPK activation enhances 3-BrP toxicity, which is conversely restrained by ERK and Akt activity. Finally, 3-BrP was seen to cooperate with antitumor agents like arsenic trioxide and curcumin in causing cell death, a response apparently mediated by both the generation of oxidative stress induced by 3-BrP and the attenuation of Akt and ERK activation by curcumin. In summary, 3-BrP cytotoxicity is the result of several combined regulatory mechanisms that might represent important targets to improve therapeutic efficacy.

Effect of 3-bromopyruvic acid on human erythrocyte antioxidant defense system

3-Bromopyruvate (3-BP) is a promising compound for anticancer therapy, its main mode of action being the inhibition of glycolytic enzymes, but this compound also induces oxidative stress. This study aimed at characterisation of the effect of 3-BP on the antioxidant defense system of erythrocytes. Suspensions of erythrocytes in PBS containing 5 mM glucose were treated with different concentration of 3-BP at 37°C for 1 h. Activities of antioxidant enzymes were estimated by standard colorimetric methods. The antioxidant capacity of erythrocytes was estimated using the 2,2'-azinobis(3-ethylbenzthiazoline-6-sulphonic acid) (ABTS(•+)) decolorisation assay and ferricyanide reduction. The content of reduced and oxidized glutathione was estimated fluorimetrically with o-phtalaldehyde. 3-BP did not affect the integrity of the erythrocyte membrane (lack of changes in the osmotic fragility). However, it induced oxidative stress in erythrocytes, as evidenced by the decrease in the content of acid-soluble thiols and reduced glutathione (GSH). Superoxide dismutase (SOD) and glutathione S-transferase (GST) activities were significantly decreased. 3-BP also decreased the transmembrane reduction of ferricyanide. Thus induction of oxidative stress in erythrocytes by 3-BP is due to depletion of glutathione and inhibition of antioxidant enzymes.

Separate and concurrent use of 2-deoxy-D-glucose and 3-bromopyruvate in pancreatic cancer cells

Unrestrained glycolysis characterizes energy meta-bolism in cancer cells. Thus, antiglycolytic reagents such as 2-deoxy-D-glucose (2-DG) and 3-bromopyruvate (3-BrPA) may be used as anticancer drugs. In the present study, we examined the anticancer effects of 2-DG and 3-BrPA in pancreatic cancer cells and investigated whether these effects were regulated by hypoxia-inducible factor-1α (HIF-1α). To this end, 2-DG and 3-BrPA were administered to wild-type (wt) MiaPaCa2 and Panc-1 pancreatic cancer cells that were incubated under hypoxic (HIF-1α-positive) or normoxic (HIF-1α-negative) conditions. In addition, 2-DG and 3-BrPA were also administered to si-MiaPaCa2 and si-Panc-1 cells that lacked HIF-1α as a result of RNA interference. Following drug exposure, cell population was measured using a viability assay. Both HIF-1α-positive and HIF-1α-negative MiaPaCa2 cells were further studied for their expression of Cu/Zn-superoxide dismutase (SOD1) and poly(ADP-ribose) polymerase (PARP) and for their contents of ATP and fumarate. In the viability assay, either 2-DG or 3-BrPA decreased the tested cells. Concurrent use of 2-DG and 3-BrPA resulted in a greater decrease of cells and also facilitated ATP depletion. In addition, 3-BrPA was seen to both decrease SOD1 and increase fumarate, which suggests that the reagent impaired the mitochondria. 3-BrPA also decreased both full-length PARP and cleaved PARP, which suggests that 3-BrPA-induced decrease in cell population was a result of cell necrosis rather than apoptosis. When HIF-1α was induced in wt-MiaPaCa2 cells by hypoxia, some effects of 2-DG and 3-BrPA were attenuated. We conclude that: i) concurrent use of 2-DG and 3-BrPA has better anticancer effects in pancreatic cancer cells, ii) 3-BrPA impairs the mitochondria of pancreatic cancer cells and induces cell necrosis, and iii) HIF-1α regulates the anticancer effects of 2-DG and 3-BrPA in pancreatic cancer cells.

2-Deoxy-D-glucose cooperates with arsenic trioxide to induce apoptosis in leukemia cells: involvement of IGF-1R-regulated Akt/mTOR, MEK/ERK and LKB-1/AMPK signaling pathways

While the anti-tumor efficacy of 2-deoxy-D-glucose (2-DG) is normally low in monotherapy, it may represent a valuable radio- and chemo-sensitizing agent. We here demonstrate that 2-10 mM 2-DG cooperates with arsenic trioxide (ATO) and other antitumor drugs to induce apoptosis in human myeloid leukemia cell lines. Using ATO and HL60 as drug and cell models, respectively, we observed that 2-DG/ATO combination activates the mitochondrial apoptotic pathway, as indicated by Bid-, and Bax-regulated cytochrome c and Omi/HtrA2 release, XIAP down-regulation, and caspase-9/-3 pathway activation. 2-DG neither causes oxidative stress nor increases ATO uptake, but causes inner mitochondria membrane permeabilization as well as moderate ATP depletion, which nevertheless do not satisfactorily explain the pro-apoptotic response. Surprisingly 2-DG causes cell line-specific decrease in LKB-1/AMPK phosphorylation/activation, and also causes Akt/mTOR/p70S6K and MEK/ERK activation, which is prevented by co-treatment with ATO. The use of kinase-specific pharmacologic inhibitors and/or siRNAs reveals that apoptosis is facilitated by AMPK inactivation and restrained by Akt and ERK activation, and that Akt and ERK activation mediates AMPK inhibition. Finally, 2-DG stimulates IGF-1R phosphorylation/activation, and co-treatment with IGF-1R inhibitor prevents 2-DG effects on Akt, ERK and AMPK, and facilitates 2-DG-provoked apoptosis. In summary 2-DG elicits IGF-1R-mediated AMPK inactivation and Akt and ERK activation, which facilitates or restrain apoptosis, respectively. 2-DG-provoked AMPK inactivation increases the apoptotic efficacy of ATO, while in turn ATO-provoked Akt and ERK inactivation may increase the efficacy of 2-DG as anti-tumor drug.

D-Amino acid oxidase-induced oxidative stress, 3-bromopyruvate and citrate inhibit angiogenesis, exhibiting potent anticancer effects

Angiogenesis is critical for cancer growth and metastasis. Steps of angiogenesis are energy consuming, while vascular endothelial cells are highly glycolytic. Glioblastoma multiforme (GBM) is a highly vascular tumor and this enhances its aggressiveness. D-amino acid oxidase (DAO) is a promising therapeutic protein that induces oxidative stress upon acting on its substrates. Oxidative stress-energy depletion (OSED) therapy was recently reported (El Sayed et al., Cancer Gene Ther, 19, 1-18, 2012). OSED combines DAO-induced oxidative stress with energy depletion caused by glycolytic inhibitors such as 3-bromopyruvate (3BP), a hexokinase II inhibitor that depleted ATP in cancer cells and induced production of hydrogen peroxide. 3BP disturbs the Warburg effect and antagonizes effects of lactate and pyruvate (El Sayed et al., J Bioenerg Biomembr, 44, 61-79, 2012). Citrate is a natural organic acid capable of inhibiting glycolysis by targeting phosphofructokinase. Here, we report that DAO, 3BP and citrate significantly inhibited angiogenesis, decreased the number of vascular branching points and shortened the length of vascular tubules. OSED delayed the growth of C6/DAO glioma cells. 3BP combined with citrate delayed the growth of C6 glioma cells and decreased significantly the number and size of C6 glioma colonies in soft agar. Human GBM cells (U373MG) were resistant to chemotherapy e.g. cisplatin and cytosine arabinoside, while 3BP was effective in decreasing the viability and disturbing the morphology of U373MG cells.

Targeting aerobic glycolysis: 3-bromopyruvate as a promising anticancer drug

The Warburg effect refers to the phenomenon whereby cancer cells avidly take up glucose and produce lactic acid under aerobic conditions. Although the molecular mechanisms underlying tumor reliance on glycolysis remains not completely clear, its inhibition opens feasible therapeutic windows for cancer treatment. Indeed, several small molecules have emerged by combinatorial studies exhibiting promising anticancer activity both in vitro and in vivo, as a single agent or in combination with other therapeutic modalities. Therefore, besides reviewing the alterations of glycolysis that occur with malignant transformation, this manuscript aims at recapitulating the most effective pharmacological therapeutics of its targeting. In particular, we describe the principal mechanisms of action and the main targets of 3-bromopyruvate, an alkylating agent with impressive antitumor effects in several models of animal tumors. Moreover, we discuss the chemo-potentiating strategies that would make unparalleled the putative therapeutic efficacy of its use in clinical settings.

3-Bromopyruvate: targets and outcomes

The pyruvate mimetic 3-bromopyruvate (3-BP) is generally presented as an inhibitor of glycolysis and has shown remarkable efficacy in not only preventing tumor growth, but even eradicating existant tumors in animal studies. We here review reported molecular targets of 3-BP and suggest that the very range of possible targets, which pertain to the altered energy metabolism of tumor cells, contributes both to the efficacy and the tumor specificity of the drug. Its in vivo efficacy is suggested to be due to a combination of glycolytic and mitochondrial targets, as well as to secondary effects affecting the tumor microenvironment. The cytotoxicity of 3-BP is less due to pyruvate mimicry than to alkylation of, e.g., key thiols. Alkylation of DNA/RNA has not been reported. More research is warranted to better understand the pharmacokinetics of 3-BP, and its potential toxic effects to normal cells, in particular those that are highly ATP-/mitochondrion-dependent.

Transport and cytotoxicity of the anticancer drug 3-bromopyruvate in the yeast Saccharomyces cerevisiae

We have investigated the cytotoxicity in Saccharomyces cerevisiae of the novel antitumor agent 3-bromopyruvate (3-BP). 3-BP enters the yeast cells through the lactate/pyruvate H(+) symporter Jen1p and inhibits cell growth at minimal inhibitory concentration of 1.8 mM when grown on non-glucose conditions. It is not submitted to the efflux pumps conferring Pleiotropic Drug Resistance in yeast. Yeast growth is more sensitive to 3-BP than Gleevec (Imatinib methanesulfonate) which in contrast to 3-BP is submitted to the PDR network of efflux pumps. The sensitivity of yeast to 3-BP is increased considerably by mutations or chemical treatment by buthionine sulfoximine that decrease the intracellular concentration of glutathione.

Butyrate activates the monocarboxylate transporter MCT4 expression in breast cancer cells and enhances the antitumor activity of 3-bromopyruvate

Most malignant tumors exhibit the Warburg effect, which consists in increased glycolysis rates with production of lactate, even in the presence of oxygen. Monocarboxylate transporters (MCTs), maintain these glycolytic rates, by mediating the influx and/or efflux of lactate and are overexpressed in several cancer cell types. The lactate and pyruvate analogue 3-bromopyruvate (3-BP) is an inhibitor of the energy metabolism, which has been proposed as a specific antitumor agent. In the present study, we aimed at determining the effect of 3-BP in breast cancer cells and evaluated the putative role of MCTs on this effect. Our results showed that the three breast cancer cell lines used presented different sensitivities to 3-BP: ZR-75-1 ER (+)>MCF-7 ER (+)>SK-BR-3 ER (-). We also demonstrated that 3-BP reduced lactate production, induced cell morphological alterations and increased apoptosis. The effect of 3-BP appears to be cytotoxic rather than cytostatic, as a continued decrease in cell viability was observed after removal of 3-BP. We showed that pre-incubation with butyrate enhanced significantly 3-BP cytotoxicity, especially in the most resistant breast cancer cell line, SK-BR-3. We observed that butyrate treatment induced localization of MCT1 in the plasma membrane as well as overexpression of MCT4 and its chaperone CD147. Our results thus indicate that butyrate pre-treatment potentiates the effect of 3-BP, most probably by increasing the rates of 3-BP transport through MCT1/4. This study supports the potential use of butyrate as adjuvant of 3-BP in the treatment of breast cancer resistant cells, namely ER (-).

Bromopyruvate mediates autophagy and cardiolipin degradation to monolyso-cardiolipin in GL15 glioblastoma cells

The GL15 glioblastoma cell line undergoes viability loss upon treatment with bromopyruvate. The biochemical mechanisms triggered by the antiglycolytic agent indicate the activation of an autophagic pathway. Acridine orange stains acidic intracellular vesicles already 60 min after bromopyruvate treatment, whereas autophagosomes engulfing electron dense material are well evidenced 18 h later. The autophagic process is accompanied by the expression of the early autophagosomal marker Atg5 and by LC3-II formation, a late biochemical marker associated with autophagosomes. In agreement with the autophagic route activation, the inhibitory and the activator Akt and ERK signaling pathways are depressed and enhanced, respectively. In spite of the energetic collapse suffered by bromopyruvate-treated cells, MALDI-TOF mass spectrometry lipid analysis does not evidence a decrease of the major phospholipids, in accordance with the need of phospholipids for autophagosomal membranes biogenesis. Contrarily, mitochondrial cardiolipin decreases, accompanied by monolyso-cardiolipin formation and complete cytochrome c degradation, events that could target mitochondria to autophagy. However, in our experimental conditions cytochrome c degradation seems to be independent of the autophagic process.

Flow cytometric evaluation of the effects of 3-bromopyruvate (3BP) and dichloracetate (DCA) on THP-1 cells: a multiparameter analysis

Two human leukemia cells K562 and THP-1, the breast cancer lines MCF-7 and ZR-75-1, and the melanoma line MDA-MB-435S were compared by flowcytometry for their behaviour at increasing levels of 3BP. K562 and THP-1 responded to 3BP by membrane depolarization and increased ROS; MCF-7 and ZR-75-1 showed decreased polarization and low ROS increase; MDA-MB-435S had limited depolarization and no ROS increase. THP-1 cells exposed to a range of 3BP concentrations in combination with DCA showed increase of polarization, slight ROS increase, and weakened nuclear integrity. 3BP and DCA show no synergism, but have complementary destructive effects on THP-1 cells. The data led to the conclusion that the THP-1 cells do not carry a functional membrane monocarboxylate transporter (MCT) or that 3BP circumvents MCT binding and can enter these cells independently.

D-amino acid oxidase gene therapy sensitizes glioma cells to the antiglycolytic effect of 3-bromopyruvate

Glioma tumors are refractory to conventional treatment. Glioblastoma multiforme is the most aggressive type of primary brain tumors in humans. In this study, we introduce oxidative stress-energy depletion (OSED) therapy as a new suggested treatment for glioblastoma. OSED utilizes D-amino acid oxidase (DAO), which is a promising therapeutic protein that induces oxidative stress and apoptosis through generating hydrogen peroxide (H2O2). OSED combines DAO with 3-bromopyruvate (3BP), a hexokinase II (HK II) inhibitor that interferes with Warburg effect, a metabolic alteration of most tumor cells that is characterized by enhanced aerobic glycolysis. Our data revealed that 3BP induced depletion of energetic capabilities of glioma cells. 3BP induced H2O2 production as a novel mechanism of its action. C6 glioma transfected with DAO and treated with D-serine together with 3BP-sensitized glioma cells to 3BP and decreased markedly proliferation, clonogenic power and viability in a three-dimensional tumor model with lesser effect on normal astrocytes. DAO gene therapy using atelocollagen as an in vivo transfection agent proved effective in a glioma tumor model in Sprague-Dawley (SD) rats, especially after combination with 3BP. OSED treatment was safe and tolerable in SD rats. OSED therapy may be a promising therapeutic modality for glioma.

Mitochondrial metabolism inhibitors for cancer therapy

Cancer cells catabolise nutrients in a different way than healthy cells. Healthy cells mainly rely on oxidative phosphorylation, while cancer cells employ aerobic glycolysis. Glucose is the main nutrient catabolised by healthy cells, while cancer cells often depend on catabolism of both glucose and glutamine. A key organelle involved in this altered metabolism is mitochondria. Mitochondria coordinate the catabolism of glucose and glutamine across the cancer cell. Targeting mitochondrial metabolism in cancer cells has potential for the treatment of this disease. Perhaps the most promising target is the hexokinase-voltage dependent anion channel-adenine nucleotide translocase complex that spans the outer- and inner-mitochondrial membranes. This complex links glycolysis, oxidative phosphorylation and mitochondrial-mediated apoptosis in cancer cells. This review discusses cancer cell mitochondrial metabolism and the small molecule inhibitors of this metabolism that are in pre-clinical or clinical development.

Anticancer targets in the glycolytic metabolism of tumors: a comprehensive review

CANCER IS A METABOLIC DISEASE AND THE SOLUTION OF TWO METABOLIC EQUATIONS: to produce energy with limited resources and to fulfill the biosynthetic needs of proliferating cells. Both equations are solved when glycolysis is uncoupled from oxidative phosphorylation in the tricarboxylic acid cycle, a process known as the glycolytic switch. This review addresses in a comprehensive manner the main molecular events accounting for high-rate glycolysis in cancer. It starts from modulation of the Pasteur Effect allowing short-term adaptation to hypoxia, highlights the key role exerted by the hypoxia-inducible transcription factor HIF-1 in long-term adaptation to hypoxia, and summarizes the current knowledge concerning the necessary involvement of aerobic glycolysis (the Warburg effect) in cancer cell proliferation. Based on the many observations positioning glycolysis as a central player in malignancy, the most advanced anticancer treatments targeting tumor glycolysis are briefly reviewed.

Mitochondrial dysfunction and effect of antiglycolytic bromopyruvic acid in GL15 glioblastoma cells

Most cancer cells, including GL15 glioblastoma cells, rely on glycolysis for energy supply. The effect of antiglycolytic bromopyruvate on respiratory parameters and viability of GL15 cells was investigated. Bromopyruvate caused Δψ(m) and MTT collapse, ATP decrease, and cell viability loss without involving apoptotic or necrotic pathways. The autophagy marker LC3-II was increased. Δψ(m) decrease was accompanied by reactive oxygen species (ROS) increase and cytochrome c (cyt c) disappearance, suggesting a link between free radical generation and intramitochondrial cyt c degradation. Indeed, the free radical inducer menadione caused a decrease in cyt c that was reversed by N-acetylcysteine. Cyt c is tightly bound to the inner mitochondrial membrane in GL15 cells, which may confer protein peroxidase activity, resulting in auto-oxidation and protein targeting to degradation in the presence of ROS. This process is directed towards impairment of the apoptotic cyt c cascade, although cells are committed to die.

Targeting glutamine metabolism sensitizes melanoma cells to TRAIL-induced death

Targeting specific metabolic pathways has emerged for cancer therapeutics. For melanoma, metabolic studies have solely focused on high glucose uptake. By contrast, little is known regarding addiction to glutamine. Using five melanoma lines and two normal cell types, addition of aminooxyacetate (AOA), an inhibitor of glutamate-dependent transaminase regulating glutaminolytic pathway, two lines underwent low levels of apoptosis (>30%), while the other three lines were resistant, as were normal cells to AOA. However, three resistant lines (but not normal cells), became sensitized to undergoing apoptosis when TRAIL was combined with AOA. TRAIL by itself had minimal effects on all cell lines and normal cells, and did not augment AOA-induced killing in the two sensitive melanoma lines. AOA plus TRAIL induced a caspase-dependent apoptotic response. AOA did not influence TRAIL DR4 or DR5 cell surface death receptor levels, but AOA enhanced pro-apoptotic protein levels of Noxa, while reducing pro-survival protein Mcl-1. To verify AOA was targeting glutamine pathway, depletion of glutamine produced similar results, because absence of glutamine sensitized three melanoma lines, but not fibroblasts to killing by TRAIL. Glutamine depletion also led to Noxa induction. These results indicate some lines are addicted to glutamine, and treatment with AOA or glutamine depletion sensitizes melanoma to TRAIL-mediated killing, while sparing normal cells. Future studies are indicated to translate these discoveries to metastatic melanoma as there is currently no treatment available to prolong survival.