Effect of extracellular AMP on cell proliferation and metabolism of breast cancer cell lines with high and low glycolytic rates

A new copper(II) complex containing long-chain aliphatic hydrazide and 1,10-phenanthroline upregulates ADP hydrolysis in triple-negative breast cancer cells

Copper can be opportunely complexed to modulate oncogenic pathways, being a promising strategy for cancer treatment. Herein, three new copper(II) complexes containing long-chain aliphatic hydrazides and 1,10-phenanthroline (1,10-phen), namely, [Cu(octh)(1,10-phen)(H2O)](NO3)21, [Cu(dech)(1,10-phen)(H2O)](NO3)22 and [Cu(dodh)(1,10-phen)(H2O)](NO3)2.H2O 3 (where octh = octanoic hydrazide, dech = decanoic hydrazide, dodh = dodecanoic hydrazide) were successfully prepared and characterized by several physical-chemical methods. Furthermore, X-ray structural analysis of complex 2 indicated that the geometry around the copper(II) ion is distorted square-pyramidal, in which hydrazide and 1,10-phenanthroline act as bidentate ligands. A water molecule in the apical position completes the coordination sphere of the metal ion. All new copper(II) complexes were cytotoxic to breast cancer cell lines (MCF7, MDA-MB-453, MDA-MB-231, and MDA-MB-157) and selective when compared to the non tumor lineage MCF-10A. In particular, complex 2 showed half-maximal inhibitory concentration (IC50) values ranging between 2.7 and 13.4 μM in MDA-MB231 cells after 24 and 48 h of treatment, respectively. Furthermore, this complex proved to be more selective for tumor cell lines when compared to doxorubicin and docetaxel. Complex 2 inhibited the clonogenicity of MDA-MB231 cells, increasing adenosine diphosphate (ADP) hydrolysis and upregulating ecto-nucleoside triphosphate diphosphohydrolase 1 (ENTPD1) transcriptional levels. In this sense, we suggest that the inhibitory effect on cell proliferation may be related to the modulation of adenosine monophosphate (AMP) levels. Thus, a novel copper(II) complex with increased cytotoxic effects and selectivity against breast cancer cells was obtained, contributing to medicinal chemistry efforts toward the development of new chemotherapeutic agents.

Targeting Mitochondria for Cancer Treatment

There is an increasing accumulation of data on the exceptional importance of mitochondria in the occurrence and treatment of cancer, and in all lines of evidence for such participation, there are both energetic and non-bioenergetic functional features of mitochondria. This analytical review examines three specific features of adaptive mitochondrial changes in several malignant tumors. The first feature is characteristic of solid tumors, whose cells are forced to rebuild their energetics due to the absence of oxygen, namely, to activate the fumarate reductase pathway instead of the traditional succinate oxidase pathway that exists in aerobic conditions. For such a restructuring, the presence of a low-potential quinone is necessary, which cannot ensure the conventional conversion of succinate into fumarate but rather enables the reverse reaction, that is, the conversion of fumarate into succinate. In this scenario, complex I becomes the only generator of energy in mitochondria. The second feature is the increased proliferation in aggressive tumors of the so-called mitochondrial (peripheral) benzodiazepine receptor, also called translocator protein (TSPO) residing in the outer mitochondrial membrane, the function of which in oncogenic transformation stays mysterious. The third feature of tumor cells is the enhanced retention of certain molecules, in particular mitochondrially directed cations similar to rhodamine 123, which allows for the selective accumulation of anticancer drugs in mitochondria. These three features of mitochondria can be targets for the development of an anti-cancer strategy.

Cannabis sativa L. modulates altered metabolic pathways involved in key metabolisms in human breast cancer (MCF-7) cells: A metabolomics study

The present study investigated the ability of Cannabis sativa leaves infusion (CSI) to modulate major metabolisms implicated in cancer cells survival, as well as to induce cell death in human breast cancer (MCF-7) cells. MCF-7 cell lines were treated with CSI for 48 h, doxorubicin served as the standard anticancer drug, while untreated MCF-7 cells served as the control. CSI caused 21.2% inhibition of cell growth at the highest dose. Liquid chromatography-mass spectroscopy (LC-MS) profiling of the control cells revealed the presence of carbohydrate, vitamins, oxidative, lipids, nucleotides, and amino acids metabolites. Treatment with CSI caused a 91% depletion of these metabolites, while concomitantly generating selenomethionine, l-cystine, deoxyadenosine triphosphate, cyclic AMP, selenocystathionine, inosine triphosphate, adenosine phosphosulfate, 5'-methylthioadenosine, uric acid, malonic semialdehyde, 2-methylguanosine, ganglioside GD2 and malonic acid. Metabolomics analysis via pathway enrichment of the metabolites revealed the activation of key metabolic pathways relevant to glucose, lipid, amino acid, vitamin, and nucleotide metabolisms. CSI caused a total inactivation of glucose, vitamin, and nucleotide metabolisms, while inactivating key lipid and amino acid metabolic pathways linked to cancer cell survival. Flow cytometry analysis revealed an induction of apoptosis and necrosis in MCF-7 cells treated with CSI. High-performance liquid chromatography (HPLC) analysis of CSI revealed the presence of cannabidiol, rutin, cinnamic acid, and ferulic. These results portray the antiproliferative potentials of CSI as an alternative therapy for the treatment and management of breast cancer as depicted by its modulation of glucose, lipid, amino acid, vitamin, and nucleotide metabolisms, while concomitantly inducing cell death in MCF-7 cells.

Rapid nutrient depletion to below the physiological range by cancer cells cultured in Plasmax

Mammalian cell culture is a fundamental tool used to study living cells. Presently, the standard protocol for performing cell culture involves the use of commercial media that contain an excess of nutrients. While this reduces the likelihood of cell starvation, it creates non-physiologic culture conditions that have been shown to 're-wire' cellular metabolism. Recently, researchers have developed new media like Plasmax, formulated to approximate the nutrient composition of human blood plasma. Although this represents an improvement in cell culture practice, physiologic media may be vulnerable to nutrient depletion. In this study we directly addressed this concern by measuring the rates of glucose and amino acid depletion from Plasmax in several cancer cell lines (PC-3, LNCaP, MCF-7, SH-SY5Y) over 48 hours. In all cell lines, depletion of glucose from Plasmax was rapid such that, by 48h, cells were hypoglycemic (<2mM glucose). Most amino acids were similarly rapidly depleted to sub-physiological levels by 48h. In contrast, glucose and most amino acids remained within the physiological range at 24h. When the experiment was done at physiological oxygen (5%) versus standard (18%) with LNCaP cells, no effect on glucose or amino acid consumption was observed. Using RNA sequencing, we show that this nutrient depletion is associated with enrichment of starvation responses, apoptotic signalling, and endoplasmic reticulum stress. A shift from glycolytic metabolism to mitochondrial respiration at 5% O2 was also measured using Seahorse analysis. Taken together, these results exemplify the metabolic considerations for Plasmax, highlighting that cell culture in Plasmax requires daily media exchange.

A Novel Metabolic Reprogramming Strategy for the Treatment of Diabetes-Associated Breast Cancer

Diabetes is directly related to the risk of breast cancer (BC) occurrence and worsened BC prognosis. Currently, there are no specific treatments for diabetes-associated BC. This paper aims to understand the fundamental mechanisms of diabetes-induced BC progression and to develop personalized treatments. It reports a metabolic reprogramming strategy (MRS) that pharmaceutical induction of glucose import and glycolysis with metformin and NF-κB inhibitor (NF-κBi) while blocking the export of excessive lactate via inhibiting monocarboxylate transporter 4 (MCT4) leads to a metabolic crisis within the cancer cells. It demonstrates that the MRS shifts the metabolism of BC cells toward higher production of lactate, blocks lactate secretion, prompts intracellular acidification and induces significant cytotoxicity. Moreover, a novel MCT4 inhibitor CB-2 has been identified by structure-based virtual screening. A triple combination of metformin, CB-2, and trabectedin, a drug that impedes NF-κB signaling, strongly inhibits BC cells. Compared to normal glucose condition, MRS elicits more potent cancer cell-killing effects under high glucose condition. Animal model studies show that diabetic conditions promote the proliferation and progression of BC xenografts in nude mice and that MRS treatment significantly inhibits HG-induced BC progression. Therefore, inhibition of MCT4 combined with metformin/NF-κBi is a promising cancer therapy, especially for diabetes-associated BC.

Virtual screening of the multi-gene regulatory molecular mechanism of Si-Wu-tang against non-triple-negative breast cancer based on network pharmacology combined with experimental validation

ETHNOPHARMACOLOGICAL RELEVANCE

Si-Wu-Tang (SWT), a prestigious herbal formula from China, has been extensively used for centuries for female-related diseases. It has been documented that SWT has a significant inhibitory effect on non-triple-negative breast cancer (non-TNBC) cells. However, there has been limited comprehensive analysis of the targeted effects of the anticancer components of SWT and its exact biological mechanism.

AIM OF THE STUDY

This study aims to uncover the mechanism by which SWT treats non-TNBC by applying a network pharmacological method combined with experimental validation.

MATERIALS AND METHODS

First, SWT compounds were collected from the Traditional Chinese Medicines Systems Pharmacology database (TCMSP) and The Encyclopedia of Traditional Chinese Medicine (ETCM), and then the targets related to SWT were obtained from the TCMSP and SwissTarget databases. Second, a target data set of non-TNBC proteins was established by using the Online Mendelian Inheritance in Man (OMIM), GeneCards and Gene Expression Omnibus (GEO) databases. Third, based on the overlap of targets between SWT and non-TNBC, a protein-protein interaction (PPI) network was built to analyse the interactions among these targets, which focused on screening for hub targets by topology. On these hub genes, we conducted a meta-analysis and survival analysis to screen the best match targets, ESR1, PPARG, CAT, and PTGS2, which had a strong correlation with the ingredients of SWT in our verification by molecular docking. In vitro experiments further proved the reliability of the network pharmacology findings. Finally, FunRich software and the ClusterProfiler package were utilized for the enrichment analysis of Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) data.

RESULTS

A total of 141 active ingredients and 116 targets of SWT were selected. GO enrichment analysis showed that the biological processes through which SWT acted against non-TNBC (FDR<0.01) mainly involved modulating energy metabolism and apoptosis. According to RT-qPCR and Western blotting, the mRNA and protein expression of ESR1, PPARG and PTGS2 were upregulated (P < 0.01), and the mRNA and protein levels of CAT were downregulated (P < 0.01), suggesting a multi-gene regulatory molecular mechanism of SWT against non-triple-negative breast cancer.

CONCLUSIONS

This research explored the multi-gene pharmacological mechanism of action of SWT against non-TNBC through network pharmacology and in vitro experiments. The findings provide new ideas for research on the mechanism of action of Chinese medicine against breast cancer.

On the Origin of ATP Synthesis in Cancer

ATP is required for mammalian cells to remain viable and to perform genetically programmed functions. Maintenance of the ΔG′_ATP hydrolysis of −56 kJ/mole is the endpoint of both genetic and metabolic processes required for life. Various anomalies in mitochondrial structure and function prevent maximal ATP synthesis through OxPhos in cancer cells. Little ATP synthesis would occur through glycolysis in cancer cells that express the dimeric form of pyruvate kinase M2. Mitochondrial substrate level phosphorylation (mSLP) in the glutamine-driven glutaminolysis pathway, substantiated by the succinate-CoA ligase reaction in the TCA cycle, can partially compensate for reduced ATP synthesis through both OxPhos and glycolysis. A protracted insufficiency of OxPhos coupled with elevated glycolysis and an auxiliary, fully operational mSLP, would cause a cell to enter its default state of unbridled proliferation with consequent dedifferentiation and apoptotic resistance, i.e., cancer. The simultaneous restriction of glucose and glutamine offers a therapeutic strategy for managing cancer.

Regulation of trophoblast cell invasion by Pyruvate Kinase isozyme M2 (PKM2)

The Pyruvate kinase isozymes M2 (PKM2) protein is a metabolic enzyme that regulates the final step of glycolysis. This enzyme is present in highly proliferating cells and is expressed in the placenta. We recently demonstrated upregulated placental PKM2 during human intrauterine growth restriction (IUGR). Our current objective was to determine PKM2 regulation of trophoblast invasion, trophoblast PKM2 localization as well as mTOR protein expression, and to determine effects of activation of PKM2 during IUGR. Human placental tissues were obtained and analyzed by immunohistochemistry and western blot. Trophoblast cells were cultured in normoxic and hypoxic conditions and real time cell invasion and PKM2 protein were determined during activation (Fructose-6-bisphosphate; FBP6) or inhibition (Shikonin) of PKM2. In vivo studies determined the effects of PKM2 activation on placental and fetal weights. IUGR samples had elevated levels of p-PKM2. Different trophoblast PKM2 localization and expression was observed during normoxia and hypoxia. Decreased trophoblast invasion and PKM2 expression was observed during mTOR inhibition. Protection from decreased placental and fetal weights was observed by PKM2 activation. We conclude that PKM2 regulates trophoblast cell invasion depending on its subcellular location. Our results suggest that PKM2 regulation in trophoblast cells is more directly affected during hypoxia and its expression is regulated by mTOR activity. Additionally, we conclude that activation of PKM2 could reverse and/or rescue the deceased placental and fetal weights observed during IUGR. These results suggest that PKM2 could be a mediator of trophoblast cell invasion and its abundance influences the development of complicated pregnancies like IUGR.

Metabolic requirements of Besnoitia besnoiti tachyzoite-triggered NETosis

Besnoitia besnoiti is the causative agent of bovine besnoitiosis, a disease affecting both, animal welfare and cattle productivity. NETosis represents an important and early host innate effector mechanism of polymorphonuclear neutrophils (PMN) that also acts against B. besnoiti tachyzoites. So far, no data are available on metabolic requirements of B. besnoiti tachyzoite-triggered NETosis. Therefore, here we analyzed metabolic signatures of tachyzoite-exposed PMN and determined the relevance of distinct PMN-derived metabolic pathways via pharmacological inhibition experiments. Overall, tachyzoite exposure induced a significant increase in glucose and serine consumption as well as glutamate production in PMN. Moreover, tachyzoite-induced cell-free NETs were significantly diminished via PMN pre-treatments with oxamate and dichloroacetate which both induce an inhibition of lactate release as well as oxythiamine, which inhibits pyruvate dehydrogenase, α-ketoglutarate dehydrogenase, and transketolase, thereby indicating a key role of pyruvate- and lactate-mediated metabolic pathways for proper tachyzoite-mediated NETosis. Furthermore, NETosis was increased by enhanced pH conditions; however, inhibitors of MCT-lactate transporters (AR-C141900, AR-C151858) failed to influence NET formation. Moreover, a significant reduction of tachyzoite-induced NET formation was also achieved by treatments with oligomycin A (inhibitor of ATP synthase) and NF449 (purinergic receptor P2X₁ antagonist) thereby suggesting a pivotal role of ATP availability for tachyzoite-mediated NETosis. In summary, the current data provide first evidence on carbohydrate-related metabolic pathways and energy supply to be involved in B. besnoiti tachyzoite-induced NETosis.

Multiplexed Single-Cell Measurements of FDG Uptake and Lactate Release Using Droplet Microfluidics

INTRODUCTION

Glucose utilization and lactate release are 2 important indicators of cancer metabolism. Most tumors consume glucose and release lactate at a higher rate than normal tissues due to enhanced aerobic glycolysis. However, these 2 indicators of metabolism have not previously been studied on a single-cell level, in the same cell.

OBJECTIVE

To develop and characterize a novel droplet microfluidic device for multiplexed measurements of glucose uptake (via its analog ¹⁸F-fluorodeoxyglucose) and lactate release, in single live cells encapsulated in an array of water-in-oil droplets.

RESULTS

Surprisingly, ¹⁸F-fluorodeoxyglucose uptake and lactate release were only marginally correlated at the single-cell level, even when assayed in a standard cell line (MDA-MB-231). While ¹⁸F-fluorodeoxyglucose-avid cells released substantial amounts of lactate, the reverse was not true, and many cells released high amounts of lactate without taking up ¹⁸F-fluorodeoxyglucose.

DISCUSSION

These results confirm that cancer cells rely on multiple metabolic pathways in addition to aerobic glycolysis and that the use of these pathways is highly heterogeneous, even under controlled culture conditions. Clinically, the large cell-to-cell variability suggests that positron emission tomography measurements of ¹⁸F-fluorodeoxyglucose uptake represent metabolic flux only in an aggregate sense, not for individual cancer cells within the tumor.

Impact of biopersistent fibrous dusts on glycolysis, glutaminolysis and serine metabolism in A549 cells

The conversion rates of different metabolic pathways summarized as a metabolic signature mirror the physiological functions and the general physiological status of a cell. The present study compared the impact of crocidolite and chrysotile asbestos, glass fibers and multi‑walled carbon nanotubes (MWCN) of two different lengths (1‑2 µm and 5‑15 µm) on the conversion rates in glycolysis, glutaminolysis and serine metabolism of A549 cells. The concentration tested was 1 µg/cm2 for all fibers. A concentration of 5 µg/cm2 was additionally used for chrysotile and crocidolite, and 25 µg/cm2 for glass fibers and MWCN. With respect to the inhibitory effect on cell proliferation and the extent of metabolic alterations, the present study revealed the following ranking among the fibers tested: Chrysotile>crocidolite>glass fibers>MWCN 5‑15 µm>MWCN 1‑2 µm. For the asbestos and glass fibers this ranking correlated best with the number of fibers. It appeared that the results observed for MWCN did not match this correlation. However, electron microscopy revealed an agglomeration of MWCN. The agglomeration decreased the toxicologically relevant number of fibers by forming larger particle‑like shapes and explained the smaller effects of MWCN 5‑15 µm and 1‑2 µm on cell proliferation and metabolism.

Insulin, not glutamine dipeptide, reduces lipases expression and prevents fat wasting and weight loss in Walker 256 tumor-bearing rats

Cachexia is the main cause of mortality in advanced cancer patients. We investigated the effects of insulin (INS) and glutamine dipeptide (GDP), isolated or associated, on cachexia and metabolic changes induced by Walker 256 tumor in rats. INS (NPH, 40 UI/kg, sc) or GDP (1.5g/kg, oral gavage) was once-daily administered during 11 days after tumor cell inoculation. GDP, INS or INS+GDP treatments did not influence the tumor growth. However, INS and INS+GDP prevented retroperitoneal fat wasting and body weight loss of tumor-bearing rats. In consistency, INS and INS+GDP prevented the increased expression of triacylglycerol lipase (ATGL) and hormone sensitive lipase (HSL), without changing the expression of tumor necrosis factor α (TNF-α) and interleukin-6 (IL-6) in the retroperitoneal adipose tissue of tumor-bearing rats. INS and INS+GDP also prevented anorexia and hyperlactatemia of tumor-bearing rats. However, INS and INS+GDP accentuated the loss of muscle mass (gastrocnemius, soleus and long digital extensor) without affecting the myostatin expression in the gastrocnemius muscle and blood corticosterone. GDP treatment did not promote beneficial effects. It can be concluded that treatment with INS (INS or INS+GDP), not with GDP, prevented fat wasting and weight loss in tumor-bearing rats without reducing tumor growth. These effects might be attributed to the reduction of lipases expression (ATGL and LHS) and increased food intake. The results show the physiological function of INS in the suppression of lipolysis induced by cachexia mediators in tumor-bearing rats.

Bardoxolone-methyl inhibits migration and metabolism in MCF7 cells

Bardoxolone-methyl (BAR) is reported to have anti-inflammatory, anti-proliferative and anti-fibrotic effects. BAR activates Nrf2 and may ameliorate oxidative stress through induction of antioxidant genes. However, off-target effects, probably concentration and NFkB-dependent, have limited the clinical use of BAR. Nrf2 regulates expression of antioxidant and mitochondrial genes and has been proposed as a target for both obesity and breast cancer. Therefore, we explored whether BAR can alter migration and proliferation in the MCF7 cell line and whether metabolic function is affected by BAR. Incubation with BAR caused a time-dependent migratory inhibition and an associated decrease in mitochondrial respiration. Both migratory and mitochondrial inhibition by BAR were further enhanced in the presence of fatty acids. In addition to the activation of Nrf2, BAR altered the expression of target mRNA GCLC and UCP1. After 24 h, BAR inhibited both glycolytic capacity, reserve (p < 0.05) and oxidative phosphorylation (p < 0.001) with an associated increase in mitochondrial ROS and loss of intracellular glutathione in MCF7 cells; however, impairment of mitochondrial activity was prevented by N-acetyl cysteine. The fatty acid, palmitate, increased mitochondrial ROS, impaired migration and oxidative phosphorylation but palmitate toxicity towards MCF7 could not be inhibited by N-acetyl cysteine suggesting that they exert effects through different pathways. BAR-activated AKT, induced DNA damage and inhibited cell proliferation. When the proteasome was inhibited, there was loss of BAR-mediated changes in p65 phosphorylation and SOD2 expression suggesting non-canonical NFkB signaling effects. These data suggest that BAR-induced ROS are important in inhibiting MCF7 migration and metabolism by negatively affecting glycolytic capacity and mitochondrial function.

Uncaria tomentosa extract alters the catabolism of adenine nucleotides and expression of ecto-5'-nucleotidase/CD73 and P2X7 and A1 receptors in the MDA-MB-231 cell line

ETHOPHARMACOLOGICAL RELEVANCE

Uncaria tomentosa (Willd.) DC. (Rubiaceae) (Ut), also known as cat's claw, is a woody liana widely spread throughout the Amazon rainforest of Central and South America, containing many chemical constituents such as oxindole alkaloids, which are responsible for various biological activities. Since ancient times, the indigenous people of Peru have used it as a bark infusion for the treatment of a wide range of health problems gastric ulcers, arthritis and rheumatism. Recently, Ut is distributed worldwide and used as an immunomodulatory and anti-inflammatory herbal remedy. Additionally, U. tomentosa also has antitumural activity. However, little is known about the action of U. tomentosa on the purinergic system mechanisms, which is involved in tumor progression.

AIM OF THE STUDY

Considering the pharmacological properties of U. tomentosa, we sought to evaluate the hydroalcoholic extract U tomentosa is able to influence the purinergic system in breast cancer cells, MDA-MB-231. Through the activity and expression of ectonucleotidases (NTPDase - CD39; Ecto-5'-nucleotidase - CD73) and purinergic repceptores (P2X7 and A1).

MATERIALS AND METHODS

A hydroalcoholic extract was prepared in two concentrations, 250 and 500μg/mL. (Ut250; Ut500). The effect of these concentrations on the activity and expression of ectonucleotidases, as well as on the density of purinergic receptors were investigated in MDA-MB-231 breast cancer cells. Cells were treated with the hydroalcoholic extract of Uncaria tomentosa and/or doxorubicin (Doxo 1μM; Ut250+Doxo; Ut500+Doxo) for 24h.

RESULTS

Although the results were not significant for the hydrolysis of the ATP, they presented an increase in the ADP hydrolysis in the Ut500+Doxo group when compared to the control group. Additionally, the activity of 5'-nucleotidase was inhibited in all groups when compared with the untreated group of cells. Inhibition of the enzyme was more evident in groups with U. tomentosa per se. The expression of CD39 was increased in the Ut250 and Ut250+Doxo groups when compared to the control group. No changes were found in the CD73 expression. Furthermore, a reduction in the density of the P2X7 receptor in all treated groups was detected. On the other hand, the density of the A1 receptor increased in all groups compared to the control group, with the exception of the Ut500+Doxo group.

CONCLUSION

Therefore, we conclude that hydroalcoholic extract of U. tomentosa may be responsible for the reduction of adenosine levels in the extracellular medium, which accelerates tumor progression. Interestingly, the dysregulation of A1 and P2X7 receptors in the MDA-MB-231 cells exacerbate the proliferation of this cells and U. tomentosa treatment may be stimulate the antitumor activity of adenosine A1 receptor and control the P2X7 effects. Our study demonstrates the significant participation of purinergic pathway in the regulation of MDA-MB-231 progression; additionally, U. tomentosa treatment alone or combined with chemotherapy may favor the action of doxorubicin.

Metabolic signatures of Besnoitia besnoiti-infected endothelial host cells and blockage of key metabolic pathways indicate high glycolytic and glutaminolytic needs of the parasite

Besnoitia besnoiti is an obligate intracellular and emerging coccidian parasite of cattle with a significant economic impact on cattle industry. During acute infection, fast-proliferating tachyzoites are continuously formed mainly in endothelial host cells of infected animals. Given that offspring formation is a highly energy and cell building block demanding process, the parasite needs to exploit host cellular metabolism to meet its metabolic demands. Here, we analyzed the metabolic signatures of B. besnoiti-infected endothelial host cells and aimed to influence parasite proliferation by inhibitors of specific metabolic pathways. The following inhibitors were tested: fluoro 2-deoxy-D-glucose and 2-deoxy-D-glucose (FDG, DG; inhibitors of glycolysis), 6-diazo-5-oxo-L-norleucin (DON; inhibitor of glutaminolysis), dichloroacetate (DCA; inhibitor of pyruvate dehydrogenase kinase which favorites channeling of glucose carbons into the TCA cycle) and adenosine-monophosphate (AMP; inhibitor of ribose 5-P synthesis). Overall, B. besnoiti infections of bovine endothelial cells induced a significant and infection rate-dependent increase of glucose, lactate, glutamine, glutamate, pyruvate, alanine, and serine conversion rates which together indicate a parasite-triggered up-regulation of glycolysis and glutaminolysis. Thus, addition of DON, FDG, and DG into the cultivation medium of B. besnoiti infected endothelial cells led to a dose-dependent inhibition of parasite replication (4 μM DON, 99.5 % inhibition; 2 mM FDG, 99.1 % inhibition; 2 mM DG, 93 % inhibition; and 8 mM DCA, 71.9 % inhibition). In contrast, AMP had no significant effects on total tachyzoite production up to a concentration of 20 mM. Together, these data may open new strategies for the development of therapeutics for B. besnoiti infections.

VER-246608, a novel pan-isoform ATP competitive inhibitor of pyruvate dehydrogenase kinase, disrupts Warburg metabolism and induces context-dependent cytostasis in cancer cells

Pyruvate dehydrogenase kinase (PDK) is a pivotal enzyme in cellular energy metabolism that has previously been implicated in cancer through both RNAi based studies and clinical correlations with poor prognosis in several cancer types.

Here, we report the discovery of a novel and selective ATP competitive pan-isoform inhibitor of PDK, VER-246608. Consistent with a PDK mediated MOA, VER-246608 increased pyruvate dehydrogenase complex (PDC) activity, oxygen consumption and attenuated glycolytic activity. However, these effects were only observed under D-glucose-depleted conditions and required almost complete ablation of PDC E1α subunit phosphorylation. VER-246608 was weakly anti-proliferative to cancer cells in standard culture media; however, depletion of either serum or combined D-glucose/L-glutamine resulted in enhanced cellular potency. Furthermore, this condition-selective cytostatic effect correlated with reduced intracellular pyruvate levels and an attenuated compensatory response involving deamination of L-alanine. In addition, VER-246608 was found to potentiate the activity of doxorubicin. In contrast, the lipoamide site inhibitor, Nov3r, demonstrated sub-maximal inhibition of PDK activity and no evidence of cellular activity.

These studies suggest that PDK inhibition may be effective under the nutrient-depleted conditions found in the tumour microenvironment and that combination treatments should be explored to reveal the full potential of this therapeutic strategy.

Nutrient depletion and metabolic profiles in breast carcinoma cell lines measured with a label-free platform

The response of two well-characterized human breast cancer cell lines (MCF-7 and MDA-MB-231) to a series of nutrient deficiencies is investigated with a label-free cell assay platform. The motivation of the research is to analyze adaptive responses of tumor cell metabolism and to find limiting conditions for cell survival. The platform measures extracellular values of pH and dissolved oxygen saturation to provide data of extracellular acidification rates and oxygen uptake rates. Additional electric cell substrate impedance sensing and bright-field cell imaging supports the data interpretation by providing information about cell morphological parameters. A sequential administration of nutrient depletions does not cause metabolic reprogramming, since the ratios of oxygen uptake to acidification return to their basal values. While the extracellular acidification drops sharply upon reduction of glucose and glutamine, the oxygen uptake is not affected. In contrast to other published data, cell death is not observed when both glucose and glutamine are depleted and cell proliferation is not inhibited, at least in MCF-7 cultures. It is assumed that residual concentrations of nutrients from the serum component are able to maintain cell viability when delivered regularly by active flow like in the cell assay platform, and, in a similar way, under physiological conditions.

Inosine strongly enhances proliferation of human C32 melanoma cells through PLC-PKC-MEK1/2-ERK1/2 and PI3K pathways

Malignant melanoma is the most deadly type of skin cancer. The lack of effective pharmacological approaches for this tumour can be related to the incomplete understanding of the pathophysiological mechanisms involved in melanoma cell proliferation. Adenosine has growth-promoting and growth inhibitory effects on tumour cells. We aimed to investigate effects of adenosine and its metabolic product, inosine, on human C32 melanoma cells and the signalling pathways involved. The 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) reduction and bromodeoxyuridine (BrdU) proliferation assays were used to evaluate adenosine, adenosine deaminase and inosine effects, in the absence or presence of adenosine receptor (AR), A3 AR and P2Y1 R antagonists and PLC, PKC, MEK1/2 and PI3K inhibitors. ERK1/2 levels were determined using an ELISA kit. Adenosine and inosine levels were quantified using an enzyme-coupled assay. Adenosine caused cell proliferation through AR activation. Adenosine deaminase increased inosine levels (nanomolar concentrations) on the extracellular space, in a time-dependent manner, inducing proliferation through A3 AR activation. Micromolar concentrations of inosine enhanced proliferation through A3 AR activation, causing an increase in ERK1/2 levels, and P2Y1 R activation via ENT-dependent mechanisms. We propose the simultaneous activation of PLC-PKC-MEK1/2-ERK1/2 and PI3K pathways as the main mechanism responsible for the proliferative effect elicited by inosine and its significant role in melanoma cancer progression.

Metabolic reprogramming in transformed mouse cortical astrocytes: A proteomic study

Metabolic reprogramming is thought to play a key role in sustaining the survival and proliferation of cancer cells. These changes facilitate for example the uptake and release of nutrients required for nucleotide, protein and lipid synthesis necessary for macromolecule assembly and tumor growth. We applied a 2D-DIGE (two-dimensional differential in-gel electrophoresis) quantitative proteomic analysis to characterize the proteomes of mouse astrocytes that underwent in vitro cancerous transformation, and of their normal counterparts. Metabolic reprogramming effects on enzymatic and structural protein expression as well as associated metabolites abundance were quantified. Using enzymatic activity measurements and zymography, we documented and confirmed several changes in abundance and activity of various isoenzymes likely to participate in metabolic reprogramming. We found that after transformation, the cells increase their expression of glycolytic enzymes, thus augmenting their ability to use aerobic glycolysis (Warburg effect). An increased capacity to dispose of reducing equivalents through lactate production was also documented. Major effects on carbohydrates, amino acids and nucleotides metabolic enzymes were also observed. Conversely, the transformed cells reduced their enzymatic capacity for reactions of tricarboxylic acid oxidation, for neurotransmitter (glutamate) metabolism, for oxidative stress defense and their expression of astroglial markers.

BIOLOGICAL SIGNIFICANCE

The use of a global approach based on a 2D DIGE analysis allows obtaining a comprehensive view of the metabolic reprogramming undergone by astrocytes upon cancerous transformation. Indeed, except for a few enzymes such as pyruvate carboxylase and glutaminase that were not detected in our initial analysis, pertinent information on the abundance of most enzymes belonging to pathways relevant to metabolic reprogramming was directly obtained. In this in vitro model, transformation causes major losses of astrocyte-specific proteins and functions and the acquisition of metabolic adaptations that favor intermediate metabolites production for increased macromolecule biosynthesis. Thus our approach appears to be readily applicable for the investigation of changes in protein abundance that determine various transformed cell phenotypes. It could similarly be applied to the evaluation of the effects of treatments aimed at correcting the consequences of cell transformation.

Metabolic scaling in solid tumours

Tumour metabolism is an outstanding topic of cancer research, as it determines the growth rate and the global activity of tumours. Recently, by combining the diffusion of oxygen, nutrients, and metabolites in the extracellular environment, and the internal motions that mix live and dead cells, we derived a growth law of solid tumours which is linked to parameters at the cellular level1. Here we use this growth law to obtain a metabolic scaling law for solid tumours, which is obeyed by tumours of different histotypes both in vitro and in vivo, and we display its relation with the fractal dimension of the distribution of live cells in the tumour mass. The scaling behaviour is related to measurable parameters, with potential applications in the clinical practice.

Who controls the ATP supply in cancer cells? Biochemistry lessons to understand cancer energy metabolism

Applying basic biochemical principles, this review analyzes data that contrasts with the Warburg hypothesis that glycolysis is the exclusive ATP provider in cancer cells. Although disregarded for many years, there is increasing experimental evidence demonstrating that oxidative phosphorylation (OxPhos) makes a significant contribution to ATP supply in many cancer cell types and under a variety of conditions. Substrates oxidized by normal mitochondria such as amino acids and fatty acids are also avidly consumed by cancer cells. In this regard, the proposal that cancer cells metabolize glutamine for anabolic purposes without the need for a functional respiratory chain and OxPhos is analyzed considering thermodynamic and kinetic aspects for the reductive carboxylation of 2-oxoglutarate catalyzed by isocitrate dehydrogenase. In addition, metabolic control analysis (MCA) studies applied to energy metabolism of cancer cells are reevaluated. Regardless of the experimental/environmental conditions and the rate of lactate production, the flux-control of cancer glycolysis is robust in the sense that it involves the same steps: glucose transport, hexokinase, hexosephosphate isomerase and glycogen degradation, all at the beginning of the pathway; these steps together with phosphofructokinase 1 also control glycolysis in normal cells. The respiratory chain complexes exert significantly higher flux-control on OxPhos in cancer cells than in normal cells. Thus, determination of the contribution of each pathway to ATP supply and/or the flux-control distribution of both pathways in cancer cells is necessary in order to identify differences from normal cells which may lead to the design of rational alternative therapies that selectively target cancer energy metabolism.

Pharmacologic activation of PKM2 slows lung tumor xenograft growth

Inactivation of the M2 form of pyruvate kinase (PKM2) in cancer cells is associated with increased tumorigenicity. To test the hypothesis that tumor growth may be inhibited through the PKM2 pathway, we generated a series of small-molecule PKM2 activators. The compounds exhibited low nanomolar activity in both biochemical and cell-based PKM2 activity assays. These compounds did not affect the growth of cancer cell lines under normal conditions in vitro, but strongly inhibited the proliferation of multiple lung cancer cell lines when serine was absent from the cell culture media. In addition, PKM2 activators inhibited the growth of an aggressive lung adenocarcinoma xenograft. These findings show that PKM2 activation by small molecules influences the growth of cancer cells in vitro and in vivo, and suggest that such compounds may augment cancer therapies.

A cyclic peptide inhibitor of C-terminal binding protein dimerization links metabolism with mitotic fidelity in breast cancer cells

Identification of direct modulators of transcription factor protein-protein interactions is a key challenge for ligand discovery that promises to significantly advance current approaches to cancer therapy. Here, we report an inhibitor of NADH-dependent dimerization of the C-terminal binding protein (CtBP) transcriptional repressor, identified by screening genetically encoded cyclic peptide libraries of up to 64 million members. CtBP dimers form the core of transcription complexes associated with epigenetic regulation of multiple genes that control many characteristics of cancer cells, including proliferation, survival and migration. CtBP monomers also have distinct and critical cellular function, thus current experimental tools that deplete all forms of a targeted protein (e.g. siRNA) do not allow the cellular consequences of this metabolically regulated transcription factor to be deciphered. The most potent inhibitor from our screen (cyclo-SGWTVVRMY) is demonstrated to disrupt CtBP dimerization in vitro and in cells. This compound is used as a chemical tool to establish that the NADH-dependent dimerization of CtBPs regulates the maintenance of mitotic fidelity in cancer cells. Treatment of highly glycolytic breast cancer cell lines with the identified inhibitor significantly reduced their mitotic fidelity, proliferation and colony forming potential, whereas the compound does not affect mitotic fidelity of cells with lower glycolytic flux. This work not only links the altered metabolic state of transformed cells to a key determinant of the tumor cell phenotype, but the uncovered compound also serves as the starting point for the development of potential therapeutic agents that target tumors by disrupting the CtBP chromatin-modifying complex.

Insulin enhances metabolic capacities of cancer cells by dual regulation of glycolytic enzyme pyruvate kinase M2

Background

Insulin is tightly associated with cancer progression; however, mechanistic insights into such observations are poorly understood. Recent studies show that metabolic transformation is critical to cancer cell proliferation. Here, we attempt to understand the role of insulin in promotion of cancer metabolism. To this end, the role of insulin in regulating glycolytic enzyme pyruvate kinase M2 (PKM2) was examined.

Results

We observed that insulin up-regulated PKM2 expression, through PI3K/mTOR mediated HIF1α induction, but significantly reduced PKM2 activity independent of this pathway. Drop in PKM2 activity was attributed to subunit dissociation leading to formation of low activity PKM2 oligomers, as assessed by density gradient centrifugation. However, tyrosine 105 phosphorylation of PKM2, known for inhibiting PKM2 activity, remained unaffected on insulin treatment. Interestingly, insulin-induced ROS was found responsible for PKM2 activity reduction. The observed changes in PKM2 status led to augmented cancer metabolism. Insulin-induced PKM2 up-regulation resulted in enhanced aerobic glycolysis as confirmed by PKM2 knockdown studies. Further, PKM2 activity reduction led to characteristic pooling of glycolytic intermediates and increased accumulation of NADPH; suggesting diversion of glucose flux towards macromolecular synthesis, necessary for cancer cell growth.

Conclusion

The study identifies new PKM2-mediated effects of insulin on cancer metabolism, thus, advancing the understanding of insulin’s role in cancer.

Ectonucleotide pyrophosphatase/phosphodiesterase (E-NPP) and adenosine deaminase (ADA) activities in prostate cancer patients: influence of Gleason score, treatment and bone metastasis

The relation between adenine nucleotides and cancer has already been described in literature. Considering that the enzymes ectonucleotide pyrophosphatase/phosphodiesterase (E-NPP) and adenosine deaminase (ADA) act together to control nucleotide levels, we aimed to investigate the role of these enzymes in prostate cancer (PCa). E-NPP and ADA activities were determined in serum and platelets of PCa patients and controls. We also verified the influence of the Gleason score, bone metastasis and treatment in the enzyme activities. Platelets and serum E-NPP activity increased, whereas ADA activity in serum decreased in PCa patients. In addition, Gleason score, metastasis and treatment influenced E-NPP and ADA activities. We may propose that E-NPP and ADA are involved in the development of PCa. Moreover, E-NPP and ADA activities are modified in PCa patients with distinct Gleason score, with bone metastasis, as well as in patients under treatment.

Oncogenic viruses and tumor glucose metabolism: like kids in a candy store

Oncogenic viruses represent a significant public health burden in light of the multitude of malignancies that result from chronic or spontaneous viral infection and transformation. Although many of the molecular signaling pathways that underlie virus-mediated cellular transformation are known, the impact of these viruses on metabolic signaling and phenotype within proliferating tumor cells is less well understood. Whether the interaction of oncogenic viruses with metabolic signaling pathways involves enhanced glucose uptake and glycolysis (both hallmark features of transformed cells) or dysregulation of molecular pathways that regulate oxidative stress, viruses are adept at facilitating tumor expansion. Through their effects on cell proliferation pathways, such as the PI3K and MAPK pathways, the cell cycle regulatory proteins p53 and ATM, and the cell stress response proteins HIF-1α and AMPK, viruses exert control over critical metabolic signaling cascades. Additionally, oncogenic viruses modulate the tumor metabolomic profile through direct and indirect interactions with glucose transporters, such as GLUT1, and specific glycolytic enzymes, including pyruvate kinase, glucose 6-phosphate dehydrogenase, and hexokinase. Through these pathways, oncogenic viruses alter the phenotypic characteristics and energy-use methods of transformed cells; therefore, it may be possible to develop novel antiglycolytic therapies to target these dysregulated pathways in virus-derived malignancies.

Biochemical issues in estimation of cytosolic free NAD/NADH ratio

Cytosolic free NAD/NADH ratio is fundamentally important in maintaining cellular redox homeostasis but current techniques cannot distinguish between protein-bound and free NAD/NADH. Williamson et al reported a method to estimate this ratio by cytosolic lactate/pyruvate (L/P) based on the principle of chemical equilibrium. Numerous studies used L/P ratio to estimate the cytosolic free NAD/NADH ratio by assuming that the conversion in cells was at near-equilibrium but not verifying how near it was. In addition, it seems accepted that cytosolic free NAD/NADH ratio was a dependent variable responding to the change of L/P ratio. In this study, we show (1) that the change of lactate/glucose (percentage of glucose that converts to lactate by cells) and L/P ratio could measure the status of conversion between pyruvate + NADH and lactate + NAD that tends to or gets away from equilibrium; (2) that cytosolic free NAD/NADH could be accurately estimated by L/P only when the conversion is at or very close to equilibrium otherwise a calculation error by one order of magnitude could be introduced; (3) that cytosolic free NAD/NADH is stable and L/P is highly labile, that the highly labile L/P is crucial to maintain the homeostasis of NAD/NADH; (4) that cytosolic free NAD/NADH is dependent on oxygen levels. Our study resolved the key issues regarding accurate estimation of cytosolic free NAD/NADH ratio and the relationship between NAD/NADH and L/P.

The Xenopus oocyte: a model for studying the metabolic regulation of cancer cell death

Abnormal metabolism and the evasion of apoptosis are both considered hallmarks of cancer. A remarkable biochemical model system, the Xenopus laevis oocyte, exhibits altered metabolism coupled to its apoptotic machinery in a similar fashion to cancer cells. This review considers the theory that these two hallmarks of cancer are coupled in tumor cells and provides strong proof that the Xenopus laevis oocyte system is an appropriate model in which to dissect the biochemical events underlying the connection between the two hallmarks. By further elucidating the mechanisms through which metabolism suppresses apoptotic machinery, we may gain a better understanding about how normal cells transform into cancer cells.

Dynamic neuronal network organization of the circadian clock and possible deterioration in disease

In mammals, the suprachiasmatic nuclei (SCNs) function as a circadian pacemaker that drives 24-h rhythms in physiology and behavior. The SCN is a multicellular clock in which the constituent oscillators show dynamics in their functional organization and phase coherence. Evidence has emerged that plasticity in phase synchrony among SCN neurons determines (i) the amplitude of the rhythm, (ii) the response to continuous light, (iii) the capacity to respond to seasonal changes, and (iv) the phase-resetting capacity. A decrease in circadian amplitude and phase-resetting capacity is characteristic during aging and can be a result of disease processes. Whether the decrease in amplitude is caused by a loss of synchronization or by a loss of single-cell rhythmicity remains to be determined and is important for the development of strategies to ameliorate circadian disorders.

Pyruvate kinase expression (PKM1 and PKM2) in cancer-associated fibroblasts drives stromal nutrient production and tumor growth

We have previously demonstrated that enhanced aerobic glycolysis and/or autophagy in the tumor stroma supports epithelial cancer cell growth and aggressive behavior, via the secretion of high-energy metabolites. These nutrients include lactate and ketones, as well as chemical building blocks, such as amino acids (glutamine) and nucleotides. Lactate and ketones serve as fuel for cancer cell oxidative metabolism, and building blocks sustain the anabolic needs of rapidly proliferating cancer cells. We have termed these novel concepts the "Reverse Warburg Effect," and the "Autophagic Tumor Stroma Model of Cancer Metabolism." We have also identified a loss of stromal caveolin-1 (Cav-1) as a marker of stromal glycolysis and autophagy. The aim of the current study was to provide genetic evidence that enhanced glycolysis in stromal cells favors tumorigenesis. To this end, normal human fibroblasts were genetically-engineered to express the two isoforms of pyruvate kinase M (PKM1 and PKM2), a key enzyme in the glycolytic pathway. In a xenograft model, fibroblasts expressing PKM1 or PKM2 greatly promoted the growth of co-injected MDA-MB-231 breast cancer cells, without an increase in tumor angiogenesis. Interestingly, PKM1 and PKM2 promoted tumorigenesis by different mechanism(s). Expression of PKM1 enhanced the glycolytic power of stromal cells, with increased output of lactate. Analysis of tumor xenografts demonstrated that PKM1 fibroblasts greatly induced tumor inflammation, as judged by CD45 staining. In contrast, PKM2 did not lead to lactate accumulation, but triggered a "pseudo-starvation" response in stromal cells, with induction of an NFκB-dependent autophagic program, and increased output of the ketone body 3-hydroxy-buryrate. Strikingly, in situ evaluation of Complex IV activity in the tumor xenografts demonstrated that stromal PKM2 expression drives mitochondrial respiration specifically in tumor cells. Finally, immuno-histochemistry analysis of human breast cancer samples lacking stromal Cav-1 revealed PKM1 and PKM2 expression in the tumor stroma. Thus, our data indicate that a subset of human breast cancer patients with a loss of stromal Cav-1 show profound metabolic changes in the tumor microenvironment. As such, this subgroup of patients may benefit therapeutically from potent inhibitors targeting glycolysis, autophagy and/or mitochondrial activity (such as metformin).

Alterations in the extracellular catabolism of nucleotides are involved in the antiproliferative effect of quercetin in human bladder cancer T24 cells

Bladder cancer is the most prevalent tumor in the genitourinary tract and the current treatments are not efficient to prevent recurrence and progression of tumor cases. Studies have revealed evidence of the involvement of the purinergic system in bladder tumorigenesis, particularly ecto-5'-NT/CD73, the enzyme responsible for AMP hydrolysis. Quercetin (3,3',4',5,7-pentahydroxyflavone) is a plant-derived flavonoid that has been shown to exert a broad range of pharmacologic properties, including potential anticancer activity. Here, we investigated the quercetin effect on the E-NTPDases and ecto-5'-nucleotidase/CD73, which catalyzes the introversion of the extracellular purine nucleotides in T24 human bladder cancer cells. The results showed that this flavonoid was able to increase ADP hydrolysis and inhibit the ecto-5'-nucleotidase/CD73 activity, with no effect on protein expression. The treatment with APCP (α,β-methyleneadenosine-5'-diphosphate), another ecto-5'-NT/CD73 inhibitor, led to a significant reduction in cell proliferation. In addition, we showed that AMP, which can be accumulating by enzyme inhibition, had an antiproliferative effect on T24 cells, which was enhanced when its hydrolysis was inhibited by APCP treatment. Otherwise, adenosine did not cause any significant effect on cell proliferation and the quercetin effects were not altered by the simultaneous presence of adenosine. Taken together, the results suggest that the antiproliferative effect of quercetin on tumor cells may occur, at least in part, via alterations in the extracellular catabolism of nucleotides, that could be by AMP accumulation, or could be due to blocked adenosine receptors by this flavonoid, supporting the potential use of quercetin in bladder cancer treatment.

Metabolic and electrochemical mechanisms of dimeric naphthoquinones cytotoxicity in breast cancer cells

Cancer cells reprogram their metabolism due to genetic alteration to compensate for increased energy demand and enhanced anabolism, cell proliferation, and protection from oxidative damage. Here, we assessed the cytotoxicity of three dimeric naphthoquinones against the glycolytic MCF-7 versus the oxidative MDA-453 breast carcinoma cell lines. Dimeric naphthoquinones 1 and 2 impaired MDA-453, but not MCF-7, cell growth at IC(50)=15 μM. Significant increase in reactive oxygen species, decrease in oxygen consumption and ATP production were observed in MDA-453 cells but not in MCF-7 cell. These findings suggest that oxidative stress and mitochondrial dysfunction are mechanisms by which these agents exert their cytotoxic effects. Cyclic voltammetry and semi-empirical molecular orbital calculations further characterized the electrochemical behavior of these compounds. These results also suggest that dimeric naphthoquinones may be used to selectively target cancer cells that depend on oxidative phosphorylation for energy production and macromolecular synthesis.

In vitro effects of an in silico-modelled 17β-estradiol derivative in combination with dichloroacetic acid on MCF-7 and MCF-12A cells

OBJECTIVES

  To investigate anti-proliferative properties of a novel in silico-modelled 17β-oestradiol derivative (C9), in combination with dichloroacetic acid (DCA), on MCF-7 and MCF-12A cells.

MATERIALS AND METHODS

  xCELLigence system was employed to determine optimal seeding number for cells, and crystal violet assay was used to assess cell number and to determine IC(50) value (24 h) for combination treatment. Light and fluorescent microscopy techniques were used to morphologically detect types of cell death. Flow cytometry was used to analyse cell cycle and apoptosis.

RESULTS

  Optimal seeding number for 96-well plates was determined to be 5000-10 000 cells/well for both MCF-7 and MCF-12A cells. IC(50) for MCF-7 cells of the combination treatment after 24 h was 130 nm of C9 in conjunction with 7.5 mm of DCA (P < 0.05). In contrast, the same concentration inhibited cell population growth by only 29.3% for MCF-12As after 24-h treatment (P < 0.05). Morphological studies revealed lower cell density of both types of combination-treated cells. Flow cytometric analyses demonstrated increase in sub-G(1) phase in combination-treated MCF-7 cells.

CONCLUSIONS

  These results demonstrate that the novel 17β-oestradiol derivative C9, in combination with DCA is a potent anti-proliferation treatment, with properties of selectivity towards tumourigenic cells. Thus, this warrants further studies as a potential combination chemotherapeutic agent for further cancer cell lines.

Comparison of metabolite profiles in U87 glioma cells and mesenchymal stem cells

Gas chromatography-mass spectrometry (GC-MS) profiles were generated from U87 glioma cells and human mesenchymal stem cells (hMSC). 37 metabolites representing glycolysis intermediates, TCA cycle metabolites, amino acids and lipids were selected for a detailed analysis. The concentrations of these metabolites were compared and Pearson correlation coefficients were used to calculate the relationship between pairs of metabolites. Metabolite profiles and correlation patterns differ significantly between the two cell lines. These profiles can be considered as a signature of the underlying biochemical system and provide snap-shots of the metabolism in mesenchymal stem cells and tumor cells.

Ifosfamide metabolite chloroacetaldehyde inhibits cell proliferation and glucose metabolism without decreasing cellular ATP content in human breast cancer cells MCF-7

Chloroacetaldehyde (CAA), a product of hepatic metabolism of the widely used anticancer drug ifosfamide (IFO), has been reported to decrease cancer cell proliferation. The basis of this effect is not completely known but has been attributed to a drop of cellular ATP content. Given the importance of glucose metabolism and of the 'Warburg effect' in cancer cells, we examined in the present study the ability of CAA to inhibit cancer cell proliferation by altering the glycolytic pathway. Cell proliferation, ATP content, glucose transport and metabolism as well as the activities of the main enzymes of glycolysis were determined in human breast cancer cells MCF-7 in the presence of various CAA concentrations (5-50 microm). Our results show that low CAA concentrations inhibited cell proliferation in a concentration-dependent manner. This inhibition was explained by a decrease in glucose utilization. Cellular ATP content was not reduced but even increased with 25 microm CAA. The inhibition of glucose metabolism was mainly explained by the decrease in glucose transport and hexokinase activity. The activity of glyceraldehyde-3-phosphate dehydrogenase, but not that of phosphofructokinase, was also inhibited. Glycolysis inhibition by CAA was effective in decreasing the proliferation of MCF-7 cells. Interestingly, this decrease was not due to ATP depletion; rather, it was linked to a drop of biosynthetic precursors from glycolytic intermediates. This CAA-induced inhibition of cell proliferation suggests that it might play a role in the antitumor activity of IFO.

In vivo factors influencing tumour M2-pyruvate kinase level in human pancreatic cancer cell lines

In tumour cells, the tetramer/dimer ratio of the pyruvate kinase isoenzyme type M2 (M2-PK) determines whether glucose carbons are degraded to lactate with production of energy (tetrameric form) or are channelled into synthetic processes (dimeric form). The influence of different tumour microenvironment conditions on the tetramer/dimer ratio of M2-PK and cell doublings were investigated in a non-metastatic and metastatic pancreatic cancer cell line. The metastatic Colo357 cells contained about fourfold more M2-PK protein and about 3.5-fold more dimeric M2-PK than the non-metastatic Panc-1 cells. In Colo357 cells hypoxia, glucose starvation as well as acidification induced an increase of the dimeric form of M2-PK, whereas in Panc-1 cells no effect on M2-PK was observed. Under hypoxia in Colo357 cells, the dimerization and inactivation of M2-PK results in an inhibition of cell proliferation, whereas under glucose starvation and acidification the dimerization of M2-PK allowed further cell doublings. M2-PK expression and the quaternary structure of M2-PK are influenced by the tumour metastatic potential. The quaternary structure of M2-PK may be differently affected by hypoxia, glucose starvation and acidification with severe consequences on cell doublings.

Inhibition of lactate dehydrogenase A induces oxidative stress and inhibits tumor progression

As the result of genetic alterations and tumor hypoxia, many cancer cells avidly take up glucose and generate lactate through lactate dehydrogenase A (LDHA), which is encoded by a target gene of c-Myc and hypoxia-inducible factor (HIF-1). Previous studies with reduction of LDHA expression indicate that LDHA is involved in tumor initiation, but its role in tumor maintenance and progression has not been established. Furthermore, how reduction of LDHA expression by interference or antisense RNA inhibits tumorigenesis is not well understood. Here, we report that reduction of LDHA by siRNA or its inhibition by a small-molecule inhibitor (FX11 [3-dihydroxy-6-methyl-7-(phenylmethyl)-4-propylnaphthalene-1-carboxylic acid]) reduced ATP levels and induced significant oxidative stress and cell death that could be partially reversed by the antioxidant N-acetylcysteine. Furthermore, we document that FX11 inhibited the progression of sizable human lymphoma and pancreatic cancer xenografts. When used in combination with the NAD(+) synthesis inhibitor FK866, FX11 induced lymphoma regression. Hence, inhibition of LDHA with FX11 is an achievable and tolerable treatment for LDHA-dependent tumors. Our studies document a therapeutical approach to the Warburg effect and demonstrate that oxidative stress and metabolic phenotyping of cancers are critical aspects of cancer biology to consider for the therapeutical targeting of cancer energy metabolism.

Targeting of cancer energy metabolism

The main purpose of this review is to update and analyze the effect of several antineoplastic drugs (adriamycin, apoptodilin, casiopeinas, cisplatin, clotrimazole, cyclophosphamide, ditercalinium, NSAIDs, tamoxifen, taxol, 6-mercaptopurine, and alpha-tocopheryl succinate) and energy metabolism inhibitors (2-DOG, gossypol, delocalized lipophilic cations, and uncouplers) on tumor development and progression. The possibility that these antineoplastic drugs currently used in in vitro cancer models, in chemo-therapy, or under study in phase I to III clinical trials induce tumor cellular death by altering also metabolite concentration (i.e., ATP), enzyme activities, and/or energy metabolism fluxes is assessed. It is proposed that the use of energy metabolic therapy, as an alternative or complementary strategy, might be a promising novel approach in the treatment of cancer.

A comparison of tumour M2-PK with carcinoembryonic antigen and CA19-9 in patients undergoing liver resection for colorectal metastases

BACKGROUND

The currently available tumour markers used in the management of patients with colorectal metastases are of limited value. Tumour M2-pyruvate kinase (TuM2-PK), a tumour-associated isoenzyme of pyruvate kinase, is elevated in patients with gastrointestinal cancer. This study has measured TuM2-PK levels in patients before and after resection of colorectal liver metastases (CLM).

MATERIALS AND METHODS

Fifty patients with CLM and no local residual disease had TuM2-PK levels measured before liver resection. In 20 patients, TuM2-PK levels were repeated at 2 weeks, 5 weeks and 5 months after resection. Plasma levels were analysed by enzyme-linked immunosorbent assay (ScheBo, Giessen, Germany). Carcinoembryonic antigen (CEA) and CA19-9 levels were measured at the same time periods by electrochemiluminescence immunoassay. CEA, CA19-9 and TuM2-PK levels were compared with the tumour number, volume, differentiation and stage. Cut-off values used for TuM2-PK, CEA and CA19-9 were 15 IU/ml, 10 ng/ml and 39 IU/ml, respectively.

RESULTS

TuM2-PK was elevated in 68%, CEA in 62% and CA19-9 in 40% of patients with CLM. TuM2-PK+CEA was elevated in 88% and TuM2-PK+CA19-9 in 78% of patients. A significant correlation was observed between tumour volume and CEA (r=0.34, P<0.05) and CA19-9 (r=0.49, P<0.005). TuM2-PK levels did not show a significant correlation with tumour differentiation, volume or the number of metastases. At 2 weeks after liver resection, CEA and CA19-9 levels had decreased to normal value in 73 and 67% of patients, respectively, but TuM2-PK remained elevated in all patients. At 5 weeks, TuM2-PK, CEA and CA19-9 levels decreased to normal in 64, 93 and 70% of patients, respectively, and at 5 months levels were normal in 58, 92 and 67%.

CONCLUSION

Plasma TuM2-PK is commonly elevated in patients with CLM. Levels do not correlate with tumour volume, number or differentiation. Levels remain elevated after liver resection, the cause of which requires further investigation.

Causes and consequences of increased glucose metabolism of cancers

In this review we examine the mechanisms (causes) underlying the increased glucose consumption observed in tumors within a teleological context (consequences). In other words, we will ask not only "How do cancers have high glycolysis?" but also, "Why?" We believe that the insights gained from answering the latter question support the conclusion that elevated glucose consumption is a necessary component of carcinogenesis. Specifically we propose that glycolysis is elevated because it produces acid, which provides an evolutionary advantage to cancer cells vis-à-vis normal parenchyma into which they invade.

The role of ecto-5'-nucleotidase/CD73 in glioma cell line proliferation

Malignant gliomas are the most common and devastating primary tumors in the brain and, despite treatment, patients with these tumors have a poor prognosis. The participation of ecto-5'-NT/CD73 per se as a proliferative factor, being involved in the control of cell growth, differentiation, invasion, migration and metastasis processes has been previously proposed. In the present study, we evaluated the activity and functions of ecto-5'-NT/CD73 during the proliferation process of rat C6 and human U138MG glioma cell lines. Increasing confluences and culture times led to an increase in ecto-5'-NT/CD73 activity in both C6 and U138MG glioma cells. RT-PCR analysis and flow cytometry analysis showed a significant increase in ecto-5'-NT/CD73 mRNA and protein levels, respectively, comparing confluent with sub-confluent cultures in human U138MG glioma cells. Ecto-5'-nucleotidase/CD73 may regulate the extracellular adenosine 5'-monophosphate (AMP) and adenosine levels. Treatment with 1 microM APCP, a competitive ecto-5'-NT/CD73 inhibitor, caused a significant reduction of 30% in glioma cell proliferation. In addition, 100 microM adenosine increases cell proliferation by 36%, and the treatment with adenosine plus NBTI and dipyridamole, produced an additional and significant increase of on cell proliferation. The inhibitory effect on cell proliferation caused by APCP was reverted by co-treatment with NBTI and dipyridamole. AMP (1 mM and 3 mM) decreased U138MG glioma cell proliferation by 29% and 42%, respectively. Taken together, these results suggest the participation of ecto-5'-NT/CD73 in cell proliferation and that this process is dependent upon the enzyme's production of adenosine, a proliferative factor, and removal of AMP, a toxic molecule for gliomas.