Symptom-based tendencies of Helicobacter pylori eradication in patients with functional dyspepsia.
Lan Ling,Yu Jing,Chen Yu-Long,Zhong Ya-Li,Zhang Hao,Jia Chang-He,Yuan Yuan,Liu Bo-Wei
World journal of gastroenterology
AIM:To investigate whether there were symptom-based tendencies in the Helicobacter pylori (H. pylori) eradication in functional dyspepsia (FD) patients. METHODS:A randomized, single-blind, placebo-controlled study of H. pylori eradication for FD was conducted. A total of 195 FD patients with H. pylori infection were divided into two groups: 98 patients in the treatment group were treated with rabeprazole 10 mg twice daily for 2 wk, amoxicillin 1.0 g and clarithromycin 0.5 g twice daily for 1 wk; 97 patients in the placebo group were given placebos as control. Symptoms of FD, such as postprandial fullness, early satiety, nausea, belching, epigastric pain and epigastric burning, were assessed 3 mo after H. pylori eradication. RESULTS:By per-protocol analysis in patients with successful H. pylori eradication, higher effective rates of 77.2% and 82% were achieved in the patients with epigastric pain and epigastric burning than those in the placebo group (P < 0.05). The effective rates for postprandial fullness, early satiety, nausea and belching were 46%, 36%, 52.5% and 33.3%, respectively, and there was no significant difference from the placebo group (39.3%, 27.1%, 39.1% and 31.4%) (P > 0.05). In 84 patients who received H. pylori eradication therapy, the effective rates for epigastric pain (73.8%) and epigastric burning (80.7%) were higher than those in the placebo group (P < 0.05). The effective rates for postprandial fullness, early satiety, nausea and belching were 41.4%, 33.3%, 50% and 31.4%, respectively, and did not differ from those in the placebo group (P > 0.05). By intention-to-treat analysis, patients with epigastric pain and epigastric burning in the treatment group achieved higher effective rates of 60.8% and 65.7% than the placebo group (33.3% and 31.8%) (P < 0.05). The effective rates for postprandial fullness, early satiety, nausea and belching were 34.8%, 27.9%, 41.1% and 26.7% respectively in the treatment group, with no significant difference from those in the placebo group (34.8%, 23.9%, 35.3% and 27.1%) (P > 0.05). CONCLUSION:The efficacy of H. pylori eradication has symptom-based tendencies in FD patients. It may be effective in the subgroup of FD patients with epigastric pain syndrome.
Changes in patients' symptoms and gastric emptying after Helicobacter pylori treatment.
Zhang Chun-Ling,Geng Chang-Hui,Yang Zhi-Wei,Li Yan-Lin,Tong Li-Quan,Gao Ping,Gao Yue-Qiu
World journal of gastroenterology
AIM:To investigate the changes in clinical symptoms and gastric emptying and their association in functional dyspepsia (FD) patients. METHODS:Seventy FD patients were enrolled and divided into 2 groups Helicobacter pylori (H. pylori)-negative group (28 patients), and H. pylori-positive group (42 patients). Patients in the H. pylori-positive group were further randomly divided into groups: H. pylori-treatment group (21 patients) and conventional treatment group (21 patients). Seventy two healthy subjects were selected as the control group. The proximal and distal stomach area was measured by ultrasound immediately after patients took the test meal, and at 20, 40, 60 and 90 min; then, gastric half-emptying time was calculated. The incidence of symptoms and gastric half-emptying time between the FD and control groups were compared. The H. pylori-negative and conventional treatment groups were given conventional treatment: domperidone 0.6 mg/(kg/d) for 1 mo. The H. pylori-treatment group was given H. pylori eradication treatment + conventional treatment: lansoprazole 30 mg once daily, clarithromycin 0.5 g twice daily and amoxicillin 1.0 g twice daily for 1 wk, then domperidone 0.6 mg/(kg/d) for 1 mo. The incidence of symptoms and gastric emptying were compared between the FD and control groups. The relationship between dyspeptic symptoms and gastric half-emptying time in the FD and control groups were analyzed. Then total symptom scores before and after treatment and gastric half-emptying time were compared among the 3 groups. RESULTS:The incidence of abdominal pain, epigastric burning sensation, abdominal distension, nausea, belching, and early satiety symptoms in the FD group were significantly higher than in the control group (50.0% vs 20.8%; 37.1% vs 12.5%; 78.6% vs 44.4%; 45.7% vs 22.2%; 52.9% vs 15.3%; 57.1% vs 19.4%; all P < 0.05). The gastric half-emptying times of the proximal end, distal end, and the whole stomach in the FD group were slower than in the control group (93.7 ± 26.2 vs 72.0 ± 14.3; 102.2 ± 26.4 vs 87.5 ± 18.2; 102.1 ± 28.6 vs 78.3 ± 14.1; all P < 0.05). Abdominal distension, belching and early satiety had an effect on distal gastric half-emptying time (P < 0.05). Abdominal distension and abdominal pain had an effect on the gastric half-emptying time of the whole stomach (P < 0.05). All were risk factors (odds ratio > 1). The total symptom score of the 3 groups after treatment was lower than before treatment (P < 0.05). Total symptom scores after treatment in the H. pylori-treatment group and H. pylori-negative group were lower than in the conventional treatment group (5.15 ± 2.27 vs 7.02 ± 3.04, 4.93 ± 3.22 vs 7.02 ± 3.04, All P < 0.05). The gastric half-emptying times of the proximal end, distal end, and the whole stomach in the H. pylori-negative and H. pylori-treatment groups were shorter than in the conventional treatment group (P < 0.05). CONCLUSION:FD patients have delayed gastric emptying. H. pylori infection treatment helps to improve symptoms of dyspepsia and is a reasonable choice for treatment in clinical practice.
The electron transport chain in anaerobically functioning eukaryotes.
Tielens A G,Van Hellemond J J
Biochimica et biophysica acta
Many lower eukaryotes can survive anaerobic conditions via a fermentation pathway that involves the use of the reduction of endogenously produced fumarate as electron sink. This fumarate reduction is linked to electron transport in an especially adapted, anaerobically functioning electron-transport chain. An aerobic energy metabolism with Krebs cycle activity is accompanied by electron transfer from succinate to ubiquinone via complex II of the respiratory chain. On the other hand, in an anaerobic metabolism, where fumarate functions as terminal electron acceptor, electrons are transferred from rhodoquinone to fumarate, which is the reversed direction. Ubiquinone cannot replace rhodoquinone in the process of fumarate reduction in vivo, as ubiquinone can only accept electrons from complex II and cannot donate them to fumarate. Rhodoquinone, with its lower redox potential than ubiquinone, is capable of donating electrons to fumarate. Eukaryotic fumarate reductases were shown to interact with rhodoquinone (a benzoquinone), whereas most prokaryotic fumarate reductases interact with the naphtoquinones menaquinone and demethylmenaquinone. Fumarate reductase, the enzyme essential for the anaerobic functioning of many eukaryotes, is structurally very similar to succinate dehydrogenase, the Krebs cycle enzyme catalysing the reverse reaction. In prokaryotes these enzymes are differentially expressed depending on the external conditions. Evidence is now emerging that also in eukaryotes two different enzymes exist for succinate oxidation and fumarate reduction that are differentially expressed.
Archaeal complex II: 'classical' and 'non-classical' succinate:quinone reductases with unusual features.
Schäfer Günter,Anemüller Stefan,Moll Ralf
Biochimica et biophysica acta
Reversible succinate dehydrogenase (SDH) activities have been ubiquitously detected in organisms from the three domains of life. They represent constituents either of respiratory complexes II in aerobes, or of fumarate dehydrogenase complexes in anaerobes. The present review gives a survey on archaeal succinate:quinone oxidoreductases (SQRs) analyzed so far. Though some of these could be studied in detail enzymologically and spectroscopically, the existence of others has been deduced only from published genome sequences. Interestingly, two groups of enzyme complexes can be distinguished in Archaea. One group resembles the properties of SDHs known from bacteria and mitochondria. The other represents a novel class with an unusual iron-sulfur cluster in subunit B and atypical sequence motifs in subunit C which may influence electron transport mechanisms and pathways. This novel class of SQRs is discussed in comparison to the so-called 'classical' complexes. A phylogenetic analysis is presented suggesting a co-evolution of the flavoprotein-binding subunit A and subunit B containing the three iron-sulfur clusters.
Variation in proton donor/acceptor pathways in succinate:quinone oxidoreductases.
Cecchini Gary,Maklashina Elena,Yankovskaya Victoria,Iverson Tina M,Iwata So
The anaerobically expressed fumarate reductase and aerobically expressed succinate dehydrogenase from Escherichia coli comprise two different classes of succinate:quinone oxidoreductases (SQR), often termed respiratory complex II. The X-ray structures of both membrane-bound complexes have revealed that while the catalytic/soluble domains are structurally similar the quinone binding domains of the enzyme complexes are significantly different. These results suggest that the anaerobic and aerobic forms of complex II have evolved different mechanisms for electron and proton transfer in their respective membrane domains.
Synthetic atpenin analogs: Potent mitochondrial inhibitors of mammalian and fungal succinate-ubiquinone oxidoreductase.
Selby Thomas P,Hughes Kenneth A,Rauh James J,Hanna Wayne S
Bioorganic & medicinal chemistry letters
Atpenins and harzianopyridone represent a unique class of penta-substituted pyridine-based natural products that are potent inhibitors of complex II (succinate-ubiquinone oxidoreductase) in the mitochondrial respiratory chain. These compounds block electron transfer in oxidative phosphorylation by inhibiting oxidation of succinate to fumarate and the coupled reduction of ubiquinone to ubiquinol. From our investigations of complex II inhibitors as potential agricultural fungicides, we report here on the synthesis and complex II inhibition for a series of synthetic atpenin analogs against both mammalian and fungal forms of the enzyme. Synthetic atpenin 2e provided optimum mammalian and fungal inhibition with slightly higher potency than natural occurring atpenin A5.
The quinone-binding and catalytic site of complex II.
Maklashina Elena,Cecchini Gary
Biochimica et biophysica acta
The complex II family of proteins includes succinate:quinone oxidoreductase (SQR) and quinol:fumarate oxidoreductase (QFR). In the facultative bacterium Escherichia coli both are expressed as part of the aerobic (SQR) and anaerobic (QFR) respiratory chains. SQR from E. coli is homologous to mitochondrial complex II and has proven to be an excellent model system for structure/function studies of the enzyme. Both SQR and QFR from E. coli are tetrameric membrane-bound enzymes that couple succinate/fumarate interconversion with quinone/quinol reduction/oxidation. Both enzymes are capable of binding either ubiquinone or menaquinone, however, they have adopted different quinone binding sites where catalytic reactions with quinones occur. A comparison of the structures of the quinone binding sites in SQR and QFR reveals how the enzymes have adapted in order to accommodate both benzo- and napthoquinones. A combination of structural, computational, and kinetic studies of members of the complex II family of enzymes has revealed that the catalytic quinone adopts different positions in the quinone-binding pocket. These data suggest that movement of the quinone within the quinone-binding pocket is essential for catalysis.
Energetics of Respiration and Oxidative Phosphorylation in Mycobacteria.
Cook Gregory M,Hards Kiel,Vilchèze Catherine,Hartman Travis,Berney Michael
Mycobacteria inhabit a wide range of intracellular and extracellular environments. Many of these environments are highly dynamic and therefore mycobacteria are faced with the constant challenge of redirecting their metabolic activity to be commensurate with either replicative growth or a non-replicative quiescence. A fundamental feature in this adaptation is the ability of mycobacteria to respire, regenerate reducing equivalents and generate ATP via oxidative phosphorylation. Mycobacteria harbor multiple primary dehydrogenases to fuel the electron transport chain and two terminal respiratory oxidases, an aa3 -type cytochrome c oxidase and cytochrome bd-type menaquinol oxidase, are present for dioxygen reduction coupled to the generation of a protonmotive force. Hypoxia leads to the downregulation of key respiratory complexes, but the molecular mechanisms regulating this expression are unknown. Despite being obligate aerobes, mycobacteria have the ability to metabolize in the absence of oxygen and a number of reductases are present to facilitate the turnover of reducing equivalents under these conditions (e.g. nitrate reductase, succinate dehydrogenase/fumarate reductase). Hydrogenases and ferredoxins are also present in the genomes of mycobacteria suggesting the ability of these bacteria to adapt to an anaerobic-type of metabolism in the absence of oxygen. ATP synthesis by the membrane-bound F1FO-ATP synthase is essential for growing and non-growing mycobacteria and the enzyme is able to function over a wide range of protonmotive force values (aerobic to hypoxic). The discovery of lead compounds that target respiration and oxidative phosphorylation in Mycobacterium tuberculosis highlights the importance of this area for the generation of new front line drugs to combat tuberculosis.
Role of mitochondrial dysfunction in cancer progression.
Hsu Chia-Chi,Tseng Ling-Ming,Lee Hsin-Chen
Experimental biology and medicine (Maywood, N.J.)
Deregulated cellular energetics was one of the cancer hallmarks. Several underlying mechanisms of deregulated cellular energetics are associated with mitochondrial dysfunction caused by mitochondrial DNA mutations, mitochondrial enzyme defects, or altered oncogenes/tumor suppressors. In this review, we summarize the current understanding about the role of mitochondrial dysfunction in cancer progression. Point mutations and copy number changes are the two most common mitochondrial DNA alterations in cancers, and mitochondrial dysfunction induced by chemical depletion of mitochondrial DNA or impairment of mitochondrial respiratory chain in cancer cells promotes cancer progression to a chemoresistance or invasive phenotype. Moreover, defects in mitochondrial enzymes, such as succinate dehydrogenase, fumarate hydratase, and isocitrate dehydrogenase, are associated with both familial and sporadic forms of cancer. Deregulated mitochondrial deacetylase sirtuin 3 might modulate cancer progression by regulating cellular metabolism and oxidative stress. These mitochondrial defects during oncogenesis and tumor progression activate cytosolic signaling pathways that ultimately alter nuclear gene expression, a process called retrograde signaling. Changes in the intracellular level of reactive oxygen species, Ca(2+), or oncometabolites are important in the mitochondrial retrograde signaling for neoplastic transformation and cancer progression. In addition, altered oncogenes/tumor suppressors including hypoxia-inducible factor 1 and tumor suppressor p53 regulate mitochondrial respiration and cellular metabolism by modulating the expression of their target genes. We thus suggest that mitochondrial dysfunction plays a critical role in cancer progression and that targeting mitochondrial alterations and mitochondrial retrograde signaling might be a promising strategy for the development of selective anticancer therapy.
Use of bacteria in anti-cancer therapies.
Ryan Rachel M,Green Jeffrey,Lewis Claire E
BioEssays : news and reviews in molecular, cellular and developmental biology
While a number of valid molecular targets have been discovered for tumours over the past decade, finding an effective way of delivering therapeutic genes specifically to tumours has proved more problematic. A variety of viral and non-viral delivery vehicles have been developed and applied in anti-cancer gene therapies. However, these suffer from either inefficient and/or short-lived gene transfer to target cells, instability in the bloodstream and inadequate tumour targeting. Recently, various types of non-pathogenic obligate anaerobic and facultative anaerobic bacteria have been shown to infiltrate and selectively replicate within solid tumours when delivered systemically. This has prompted the development of cancer gene therapy protocols that use such bacteria as gene delivery vehicles. Here, we review the evidence for the success of these in pre-clinical models and clinical trials, as single modality treatments and in combination with conventional cancer therapies.
Anoxia tolerance in turtles: metabolic regulation and gene expression.
Storey Kenneth B
Comparative biochemistry and physiology. Part A, Molecular & integrative physiology
Freshwater turtles of the Trachemys and Chrysemys genera are champion facultative anaerobes able to survive for several months without oxygen during winter hibernation in cold water. They have been widely used as models to identify and understand the molecular mechanisms of natural anoxia tolerance and the molecular basis of the hypoxic/ischemic injuries that occur in oxygen-sensitive systems and underlie medical problems such as heart attack and stroke. Peter L. Lutz spent much of his career investigating turtle anaerobiosis with a particular focus on the mechanisms of brain ion homeostasis and neurotransmitter responses to anoxia exposure and the mechanisms that suppress brain ion channel function and neuronal excitability during anaerobiosis. Our interests intersected over the mechanisms of metabolic rate depression which is key to long term anoxia survival. Studies in my lab have shown that a key mechanism of metabolic arrest is reversible protein phosphorylation which provides coordinated suppression of the rates of multiple ATP-producing, ATP-utilizing and related cellular processes to allow organisms to enter a stable hypometabolic state. Anoxia tolerance is also supported by selective gene expression as revealed by recent studies using cDNA library and DNA array screening. New studies with both adult T. scripta elegans and hatchling C. picta marginata have identified prominent groups of genes that are up-regulated under anoxia in turtle organs, in several cases suggesting aspects of cell function and metabolic regulation that have not previously been associated with anaerobiosis. These groups of anoxia-responsive genes include mitochondrially-encoded subunits of electron transport chain proteins, iron storage proteins, antioxidant enzymes, serine protease inhibitors, transmembrane solute carriers, neurotransmitter receptors and transporters, and shock proteins.
Facultative or obligate anaerobic bacteria have the potential for multimodality therapy of solid tumours.
Wei Ming Q,Ellem Kay A O,Dunn Paul,West Malcolm J,Bai Chun Xue,Vogelstein Bert
European journal of cancer (Oxford, England : 1990)
Recent understanding of the unique pathology of solid tumours has shed light on the difficult and disappointing nature of their clinical treatment. All solid tumours undergo angiogenesis that results in biological changes and adaptive metabolisms, i.e. formation of defective vessels, appearance of hypoxic areas, and emergence of an heterogeneous tumour cell population. This micro-milieu provides a haven for anaerobic bacteria. The strictly anaerobic clostridia have several advantages over other facultative anaerobes such as salmonella or lactic acid-producing, Gram-positive, obligate, anaerobic bifidobacteria. Both pathogenic and non-pathogenic clostridia have been demonstrated to specifically colonise and destroy solid tumours. Early trials of non-pathogenic strains in humans had shown plausible safety. Genetic modifications and adaptation of pathogenic and non-pathogenic strains have further created improved features. However, these manipulations rarely generate strains that resulted in complete tumour control alone. Combined modalities of therapies with chemo and radiation therapies, on the other hand, often perform better, including 'cure' of solid tumours in a high percentage of animals. Considering that clostridia have unlimited capacities for genetic improvement, we predict that designer clostridia forecast a promising future for the development of potent strains for tumour destruction, incorporating mechanisms such as immunotherapy to overcome immune suppression and to elicit strong anti-tumour responses.
Forever young: mechanisms of natural anoxia tolerance and potential links to longevity.
Krivoruchko Anastasia,Storey Kenneth B
Oxidative medicine and cellular longevity
While mammals cannot survive oxygen deprivation for more than a few minutes without sustaining severe organ damage, some animals have mastered anaerobic life. Freshwater turtles belonging to the Trachemys and Chrysemys genera are the champion facultative anaerobes of the vertebrate world, often surviving without oxygen for many weeks at a time. The physiological and biochemical mechanisms that underlie anoxia tolerance in turtles include profound metabolic rate depression, post-translational modification of proteins, strong antioxidant defenses, activation of specific stress-responsive transcription factors, and enhanced expression of cytoprotective proteins. Turtles are also known for their incredible longevity and display characteristics of "negligible senescence". We propose that the robust stress-tolerance mechanisms that permit long term anaerobiosis by turtles may also support the longevity of these animals. Many of the mechanisms involved in natural anoxia tolerance, such as hypometabolism or the induction of various protective proteins/pathways, have been shown to play important roles in mammalian oxygen-related diseases and improved understanding of how cells survive without oxygen could aid in the understanding and treatment of various pathological conditions that involve hypoxia or oxidative stress. In the present review we discuss the recent advances made in understanding the molecular nature of anoxia tolerance in turtles and the potential links between this tolerance and longevity.
The thioredoxin system in the dental caries pathogen Streptococcus mutans and the food-industry bacterium Streptococcus thermophilus.
Marco Salvatore,Rullo Rosario,Albino Antonella,Masullo Mariorosario,De Vendittis Emmanuele,Amato Massimo
The Streptococcus genus includes the pathogenic species Streptococcus mutans, the main responsible of dental caries, and the safe microorganism Streptococcus thermophilus, used for the manufacture of dairy products. These facultative anaerobes control the levels of reactive oxygen species (ROS) and indeed, both S. mutans and S. thermophilus possess a cambialistic superoxide dismutase, the key enzyme for a preventive action against ROS. To evaluate the properties of a crucial mechanism for repairing ROS damages, the molecular and functional characterization of the thioredoxin system in these streptococci was investigated. The putative genes encoding its protein components in S. mutans and S. thermophilus were analysed and the corresponding recombinant proteins were purified. A single thioredoxin reductase was obtained from either S. mutans (SmTrxB) or S. thermophilus (StTrxB1), whereas two thioredoxins were prepared from either S. mutans (SmTrxA and SmTrxH1) or S. thermophilus (StTrxA1 and StTrxA2). Both SmTrxB and StTrxB1 reduced the synthetic substrate DTNB in the presence of NADPH, whereas only SmTrxA and StTrxA1 accelerated the insulin reduction in the presence of DTT. To reconstitute an in vitro streptococcal thioredoxin system, the combined activity of the thioredoxin components was tested through the insulin precipitation in the absence of DTT. The assay functions with a combination of SmTrxB or StTrxB1 with either SmTrxA or StTrxA1. These results suggest that the streptococcal members of the thioredoxin system display a direct functional interaction between them and that these protein components are interchangeable within the Streptococcus genus. In conclusion, our data prove the existence of a functioning thioredoxin system even in these microaerophiles.
One-carbon metabolic pathway rewiring in Escherichia coli reveals an evolutionary advantage of 10-formyltetrahydrofolate synthetase (Fhs) in survival under hypoxia.
Sah Shivjee,Aluri Srinivas,Rex Kervin,Varshney Umesh
Journal of bacteriology
In cells, N(10)-formyltetrahydrofolate (N(10)-fTHF) is required for formylation of eubacterial/organellar initiator tRNA and purine nucleotide biosynthesis. Biosynthesis of N(10)-fTHF is catalyzed by 5,10-methylene-tetrahydrofolate dehydrogenase/cyclohydrolase (FolD) and/or 10-formyltetrahydrofolate synthetase (Fhs). All eubacteria possess FolD, but some possess both FolD and Fhs. However, the reasons for possessing Fhs in addition to FolD have remained unclear. We used Escherichia coli, which naturally lacks fhs, as our model. We show that in E. coli, the essential function of folD could be replaced by Clostridium perfringens fhs when it was provided on a medium-copy-number plasmid or integrated as a single-copy gene in the chromosome. The fhs-supported folD deletion (ΔfolD) strains grow well in a complex medium. However, these strains require purines and glycine as supplements for growth in M9 minimal medium. The in vivo levels of N(10)-fTHF in the ΔfolD strain (supported by plasmid-borne fhs) were limiting despite the high capacity of the available Fhs to synthesize N(10)-fTHF in vitro. Auxotrophy for purines could be alleviated by supplementing formate to the medium, and that for glycine was alleviated by engineering THF import into the cells. The ΔfolD strain (harboring fhs on the chromosome) showed a high NADP(+)-to-NADPH ratio and hypersensitivity to trimethoprim. The presence of fhs in E. coli was disadvantageous for its aerobic growth. However, under hypoxia, E. coli strains harboring fhs outcompeted those lacking it. The computational analysis revealed a predominant natural occurrence of fhs in anaerobic and facultative anaerobic bacteria.
Fueling the Cell Division Cycle.
Salazar-Roa María,Malumbres Marcos
Trends in cell biology
Cell division is a complex process with high energy demands. However, how cells regulate the generation of energy required for DNA synthesis and chromosome segregation is not well understood. Recent data suggest that changes in mitochondrial dynamics and metabolic pathways such as oxidative phosphorylation (OXPHOS) and glycolysis crosstalk with, and are tightly regulated by, the cell division machinery. Alterations in energy availability trigger cell-cycle checkpoints, suggesting a bidirectional connection between cell division and general metabolism. Some of these connections are altered in human disease, and their manipulation may help in designing therapeutic strategies for specific diseases including cancer. We review here recent studies describing the control of metabolism by the cell-cycle machinery.
Treatment of Neuroblastoma with an Engineered "Obligate" Anaerobic Strain YB1.
Ning Bo-Tao,Yu Bin,Chan Shing,Chan Jian-Liang,Huang Jian-Dong,Chan Godfrey Chi-Fung
Journal of Cancer
Neuroblastoma is an embryonic solid tumor derived from the progenitors of the sympathetic nervous system. More than half of the patients developed metastatic disease at the time of initial diagnosis and had poor outcome with current therapeutic approaches. In recent years, some obligate and facultative anaerobic bacteria were reported to target the hypoxic and necrotic region of solid tumor models and caused tumor regression. We recently successfully constructed an "obligate" anaerobic strain YB1 that was applied in breast cancer nude mice model by us. Here, we report the application of YB1 in neuroblastoma treatment. The anti-cancer effect and side-effects of YB1 was examined in both and experiment. Previous established orthotopic neuroblastoma SCID/beige murine model using SK-NLP/luciferase cell line was adopted. , YB1 induced apoptosis for up to 31.4% of the neuroblastoma cells under anaerobic condition, three times more than that under aerobic condition (10.9%). The expression of both Toll like Receptor 4 and 5 (TLR4 and TLR5) in cancer cells were significantly up-regulated (<0.05<0.01 respectively) after the treatment of YB1 under anaerobic condition. In mouse model, YB1 preferentially accumulated inside the core of the tumors, rather than in normal tissues as our previous reported. This is suggestive of the hypoxic nature of tumor core. Tumor growth was significantly retarded in YB1 treatment group (). Furthermore, there was no long-term organ damage noted in all the organs examined including heart, lung, liver, spleen and brain in the YB1 treated mice. The genetic modified strain YB1 is a promising anti-tumor strategy against the tumor bulk for neuroblastoma. Future study can be extended to other common cancer types to verify the relative efficacy on different neoplastic cells.
Targeting Melanoma Hypoxia with the Food-Grade Lactic Acid Bacterium .
Garza-Morales Rodolfo,Rendon Beatriz E,Malik Mohammad Tariq,Garza-Cabrales Jeannete E,Aucouturier Anne,Bermúdez-Humarán Luis G,McMasters Kelly M,McNally Lacey R,Gomez-Gutierrez Jorge G
Melanoma is the most aggressive form of skin cancer. Hypoxia is a feature of the tumor microenvironment that reduces efficacy of immuno- and chemotherapies, resulting in poor clinical outcomes. is a facultative anaerobic gram-positive lactic acid bacterium (LAB) that is Generally Recognized as Safe (GRAS). Recently, the use of LAB as a delivery vehicle has emerged as an alternative strategy to deliver therapeutic molecules; therefore, we investigated whether can target and localize within melanoma hypoxic niches. To simulate hypoxic conditions , melanoma cells A2058, A375 and MeWo were cultured in a chamber with a gas mixture of 5% CO, 94% N and 1% O. Among the cell lines tested, MeWo cells displayed greater survival rates when compared to A2058 and A375 cells. Co-cultures of expressing GFP or mCherry and MeWo cells revealed that efficiently express the transgenes under hypoxic conditions. Moreover, multispectral optoacoustic tomography (MSOT), and near infrared (NIR) imaging of tumor-bearing BALB/c mice revealed that the intravenous injection of either expressing β-galactosidase (β-gal) or infrared fluorescent protein (IRFP713) results in the establishment of the recombinant bacteria within tumor hypoxic niches. Overall, our data suggest that represents an alternative strategy to target and deliver therapeutic molecules into the tumor hypoxic microenvironment.
Phages in Anaerobic Systems.
Hernández Santiago,Vives Martha J
Since the discovery of phages in 1915, these viruses have been studied mostly in aerobic systems, or without considering the availability of oxygen as a variable that may affect the interaction between the virus and its host. However, with such great abundance of anaerobic environments on the planet, the effect that a lack of oxygen can have on the phage-bacteria relationship is an important consideration. There are few studies on obligate anaerobes that investigate the role of anoxia in causing infection. In the case of facultative anaerobes, it is a well-known fact that their shifting from an aerobic environment to an anaerobic one involves metabolic changes in the bacteria. As the phage infection process depends on the metabolic state of the host bacteria, these changes are also expected to affect the phage infection cycle. This review summarizes the available information on phages active on facultative and obligate anaerobes and discusses how anaerobiosis can be an important parameter in phage infection, especially among facultative anaerobes.
Eukaryotic pyruvate formate lyase and its activating enzyme were acquired laterally from a Firmicute.
Stairs Courtney W,Roger Andrew J,Hampl Vladimir
Molecular biology and evolution
Most of the major groups of eukaryotes have microbial representatives that thrive in low oxygen conditions. Those that have been studied in detail generate ATP via pathways involving anaerobically functioning enzymes of pyruvate catabolism that are typically absent in aerobic eukaryotes and whose origins remain controversial. These enzymes include pyruvate:ferredoxin oxidoreductase, pyruvate:NADP(+) oxidoreductase, and pyruvate formate lyase (Pfl). Pfl catalyzes the nonoxidative generation of formate and acetyl-Coenzyme A (CoA) from pyruvate and CoA and is activated by Pfl activating enzyme (Pfla). Within eukaryotes, this extremely oxygen-sensitive pathway was first described in the hydrogenosomes of anaerobic chytrid fungi and has more recently been characterized in the mitochondria and chloroplasts of the chlorophyte alga Chlamydomonas reinhardtii. To clarify the origins of this pathway, we have comprehensively searched for homologs of Pfl and Pfla in publicly available large-scale eukaryotic genomic and cDNA sequencing data, including our own from the anaerobic amoebozoan Mastigamoeba balamuthi. Surprisingly, we find that these enzymes are widely distributed and are present in diverse facultative or obligate anaerobic eukaryotic representatives of the archaeplastidan, metazoan, amoebozoan, and haptophyte lineages. Using maximum likelihood and Bayesian phylogenetic methods, we show that the eukaryotic Pfl and Pfla sequences each form monophyletic groups that are most closely related to homologs in firmicute gram-positive bacteria. Topology tests exclude both α-proteobacterial and cyanobacterial affinities for these genes suggesting that neither originated from the endosymbiotic ancestors of mitochondria or chloroplasts. Furthermore, the topologies of the eukaryote portion of the Pfl and Pfla trees significantly differ from well-accepted eukaryote relationships. Collectively, these results indicate that the Pfl pathway was first acquired by lateral gene transfer into a eukaryotic lineage most probably from a firmicute bacterial lineage and that it has since been spread across diverse eukaryotic groups by more recent eukaryote-to-eukaryote transfer events.
A commensal symbiotic interrelationship for the growth of Symbiobacterium toebii with its partner bacterium, Geobacillus toebii.
Kim Kwang,Kim Joong-Jae,Masui Ryoji,Kuramitsu Seiki,Sung Moon-Hee
BMC research notes
BACKGROUND:Symbiobacterium toebii is a commensal symbiotic thermophile that absolutely requires its partner bacterium Geobacillus toebii for growth. Despite development of an independent cultivation method using cell-free extracts, the growth of Symbiobacterium remains unknown due to our poor understanding of the symbiotic relationship with its partner bacterium. Here, we investigated the interrelationship between these two bacteria for growth of S. toebii using different cell-free extracts of G. toebii. RESULTS:Symbiobacterium toebii growth-supporting factors were constitutively produced through almost all growth phases and under different oxygen tensions in G. toebii, indicating that the factor may be essential components for growth of G. toebii as well as S. toebii. The growing conditions of G. toebii under different oxygen tension dramatically affected to the initial growth of S. toebii and the retarded lag phase was completely shortened by reducing agent, L-cysteine indicating an evidence of commensal interaction of microaerobic and anaerobic bacterium S. toebii with a facultative aerobic bacterium G. toebii. In addition, the growth curve of S. toebii showed a dependency on the protein concentration of cell-free extracts of G. toebii, demonstrating that the G. toebii-derived factors have nutrient-like characters but not quorum-sensing characters. CONCLUSIONS:Not only the consistent existence of the factor in G. toebii during all growth stages and under different oxygen tensions but also the concentration dependency of the factor for proliferation and optimal growth of S. toebii, suggests that an important biosynthetic machinery lacks in S. toebii during evolution. The commensal symbiotic bacterium, S. toebii uptakes certain ubiquitous and essential compound for its growth from environment or neighboring bacteria that shares the equivalent compounds. Moreover, G. toebii grown under aerobic condition shortened the lag phase of S. toebii under anaerobic and microaerobic conditions, suggests a possible commensal interaction that G. toebii scavengers ROS/RNS species and helps the initial growth of S. toebii.
Proteomic evidences for rex regulation of metabolism in toxin-producing Bacillus cereus ATCC 14579.
Laouami Sabrina,Clair Géremy,Armengaud Jean,Duport Catherine
The facultative anaerobe, Bacillus cereus, causes diarrheal diseases in humans. Its ability to deal with oxygen availability is recognized to be critical for pathogenesis. The B. cereus genome comprises a gene encoding a protein with high similarities to the redox regulator, Rex, which is a central regulator of anaerobic metabolism in Bacillus subtilis and other Gram-positive bacteria. Here, we showed that B. cereus rex is monocistronic and down-regulated in the absence of oxygen. The protein encoded by rex is an authentic Rex transcriptional factor since its DNA binding activity depends on the NADH/NAD+ ratio. Rex deletion compromised the ability of B. cereus to cope with external oxidative stress under anaerobiosis while increasing B. cereus resistance against such stress under aerobiosis. The deletion of rex affects anaerobic fermentative and aerobic respiratory metabolism of B. cereus by decreasing and increasing, respectively, the carbon flux through the NADH-recycling lactate pathway. We compared both the cellular proteome and exoproteome of the wild-type and Δrex cells using a high throughput shotgun label-free quantitation approach and identified proteins that are under control of Rex-mediated regulation. Proteomics data have been deposited to the ProteomeXchange with identifier PXD000886. The data suggest that Rex regulates both the cross-talk between metabolic pathways that produce NADH and NADPH and toxinogenesis, especially in oxic conditions.
Microbial oxidative stress response: Novel insights from environmental facultative anaerobic bacteria.
Fu Huihui,Yuan Jie,Gao Haichun
Archives of biochemistry and biophysics
Facultative bacteria can grow under either oxic or anoxic conditions. While oxygen provides substantial advantages in energy yield by respiration, it can become life-threatening because of reactive oxygen species that derive from the molecule naturally. Thus, to survive and thrive in a given niche, these bacteria have to constantly regulate physiological processes to make maximum benefits from oxygen respiration while restraining oxidative stress. Molecular mechanisms and physiological consequences of oxidative stress have been under extensive investigation for decades, mostly on research model Escherichia coli, from which our understanding of bacterial oxidative stress response is largely derived. Nevertheless, given that bacteria live in enormously diverse environments, to cope with oxidative stress different strategies are conceivably developed.
Gsy, a novel glucansucrase from Leuconostoc mesenteroides, mediates the formation of cell aggregates in response to oxidative stress.
Yan Minghui,Han Jin,Xu Xiaofen,Liu Lianliang,Gao Caixia,Zheng Huajun,Chen Yunxia,Tao Yimin,Zhou Hu,Li Yunfei,Wu Zhengjun
Leuconostoc mesenteroides is a member of lactic acid bacteria (LAB) with wide applications in the food and medical industries. Species in the genus Leuconostoc are catalase-negative and generally regarded as facultative anaerobic or aerotolerant organisms. Despite their extensive use in industry, certain issues concerning the aerobic life of L. mesenteroides, e.g., the mechanism involved in the tolerance to oxygen, remain to be addressed. In this manuscript, a survival strategy employed by L. mesenteroides BD3749 in response to oxidative stress was elucidated. BD3749 cells cultivated in medium with sucrose available synthesized large amounts of exopolysaccharides, mostly consisting of insoluble EPS. When BD3749 cells were challenged with oxidative stress, the amount of insoluble EPS was greatly enhanced. The synthesized EPSs reduced the accumulation of reactive oxygen species (ROS) in bacterial cells and improved their survival during chronic oxidative stress. Another study showed that Gsy, a novel glucansucrase in the GH70 family that is induced by sucrose and up-regulated following exposure to oxygen, was responsible for the synthesis of insoluble EPS. Gsy was subsequently demonstrated to play pivotal roles in the formation of aggregates to alleviate the detrimental effects on BD3749 cells exerted by oxygen.
[Endogenous production and physiological functions of hydrogen sulfide in facultative anaerobic bacteria].
Wu Genfu,Gao Haichun
Wei sheng wu xue bao = Acta microbiologica Sinica
H2S is the third gaseous signaling molecule next to nitric oxide and carbon monoxide, but studies on its physiological functions in bacteria are just emerging. In this paper, we review recent findings regarding endogenous production and physiological functions of H2S in facultative anaerobic bacteria, partly based on our own research on Shewanella oneidensis. There are two principal H2S producing pathways in S. oneidensis:one is through cysteine degradation, and the other is via inorganic sulfur respiration. Endogenous H2S could either benefit mutual growing bacteria by supplying energy and inorganic, or inhibit competing bacteria. Our review attaches particular importance to the role of H2S in bacterial oxidative stress response. On one hand, H2S is able to directly inhibit heme-containing catalase, enhancing killing by H2O2. On the other hand, H2S could activate oxidative response as a signaling molecule, leading to cell protection from the oxidative stress due to elevated expression of H2O2 scavenging and repairing systems. Intriguingly, the dominance of either role is determined by H2S-treating time, that is, inhibition is the immediate response whereas activation of oxidative stress response needs extended treatment. The elucidation of endogenous production and its physiological function of H2S in facultative anaerobic bacteria would improve understanding of biogeochemical sulfur recycling, and facilitate control of infectious bacterial pathogens.
Involvement of ERK-Nrf-2 signaling in ionizing radiation induced cell death in normal and tumor cells.
Patwardhan Raghavendra S,Checker Rahul,Sharma Deepak,Sandur Santosh K,Sainis Krishna B
Prolonged oxidative stress favors tumorigenic environment and inflammation. Oxidative stress may trigger redox adaptation mechanism(s) in tumor cells but not normal cells. This may increase levels of intracellular antioxidants and establish a new redox homeostasis. Nrf-2, a master regulator of battery of antioxidant genes is constitutively activated in many tumor cells. Here we show that, murine T cell lymphoma EL-4 cells show constitutive and inducible radioresistance via activation of Nrf-2/ERK pathway. EL-4 cells contained lower levels of ROS than their normal counterpart murine splenic lymphocytes. In response to radiation, the thiol redox circuits, GSH and thioredoxin were modified in EL-4 cells. Pharmacological inhibitors of ERK and Nrf-2 significantly enhanced radiosensitivity and reduced clonogenic potential of EL-4 cells. Unirradiated lymphoma cells showed nuclear accumulation of Nrf-2, upregulation of its dependent genes and protein levels. Interestingly, MEK inhibitor abrogated its nuclear translocation suggesting role of ERK in basal and radiation induced Nrf-2 activation in tumor cells. Double knockdown of ERK and Nrf-2 resulted in higher sensitivity to radiation induced cell death as compared to individual knockdown cells. Importantly, NF-kB which is reported to be constitutively active in many tumors was not present at basal levels in EL-4 cells and its inhibition did not influence radiosensitivity of EL-4 cells. Thus our results reveal that, tumor cells which are subjected to heightened oxidative stress employ master regulator cellular redox homeostasis Nrf-2 for prevention of radiation induced cell death. Our study reveals the molecular basis of tumor radioresistance and highlights role of Nrf-2 and ERK.
NAD+ Kinase as a Therapeutic Target in Cancer.
Tedeschi Philip M,Bansal Nitu,Kerrigan John E,Abali Emine E,Scotto Kathleen W,Bertino Joseph R
Clinical cancer research : an official journal of the American Association for Cancer Research
NAD kinase (NADK) catalyzes the phosphorylation of nicotinamide adenine dinucleotide (NAD) to nicotinamide adenine dinucleotide phosphate (NADP) using ATP as the phosphate donor. NADP is then reduced to NADPH by dehydrogenases, in particular glucose-6-phosphate dehydrogenase and the malic enzymes. NADPH functions as an important cofactor in a variety of metabolic and biosynthetic pathways. The demand for NADPH is particularly high in proliferating cancer cells, where it acts as a cofactor for the synthesis of nucleotides, proteins, and fatty acids. Moreover, NADPH is essential for the neutralization of the dangerously high levels of reactive oxygen species (ROS) generated by increased metabolic activity. Given its key role in metabolism and regulation of ROS, it is not surprising that several recent studies, including in vitro and in vivo assays of tumor growth and querying of patient samples, have identified NADK as a potential therapeutic target for the treatment of cancer. In this review, we will discuss the experimental evidence justifying further exploration of NADK as a clinically relevant drug target and describe our studies with a lead compound, thionicotinamide, an NADK inhibitor prodrug. Clin Cancer Res; 22(21); 5189-95. ©2016 AACR.
ROS signalling in the biology of cancer.
Moloney Jennifer N,Cotter Thomas G
Seminars in cell & developmental biology
Increased reactive oxygen species (ROS) production has been detected in various cancers and has been shown to have several roles, for example, they can activate pro-tumourigenic signalling, enhance cell survival and proliferation, and drive DNA damage and genetic instability. Counterintuitively ROS can also promote anti-tumourigenic signalling, initiating oxidative stress-induced tumour cell death. Tumour cells express elevated levels of antioxidant proteins to detoxify elevated ROS levels, establish a redox balance, while maintaining pro-tumourigenic signalling and resistance to apoptosis. Tumour cells have an altered redox balance to that of their normal counterparts and this identifies ROS manipulation as a potential target for cancer therapies. This review discusses the generation and sources of ROS within tumour cells, the regulation of ROS by antioxidant defence systems, as well as the effect of elevated ROS production on their signalling targets in cancer. It also provides an insight into how pro- and anti-tumourigenic ROS signalling pathways could be manipulated in the treatment of cancer.
ROS-modulated therapeutic approaches in cancer treatment.
Raza Muhammad Hassan,Siraj Sami,Arshad Abida,Waheed Usman,Aldakheel Fahad,Alduraywish Shatha,Arshad Muhammad
Journal of cancer research and clinical oncology
PURPOSE:Reactive oxygen species (ROS) are produced in cancer cells as a result of increased metabolic rate, dysfunction of mitochondria, elevated cell signaling, expression of oncogenes and increased peroxisome activities. Certain level of ROS is required by cancer cells, above or below which lead to cytotoxicity in cancer cells. This biochemical aspect can be exploited to develop novel therapeutic agents to preferentially and selectively target cancer cells. METHODS:We searched various electronic databases including PubMed, Web of Science, and Google Scholar for peer-reviewed english-language articles. Selected articles ranging from research papers, clinical studies, and review articles on the ROS production in living systems, its role in cancer development and cancer treatment, and the role of microbiota in ROS-dependent cancer therapy were analyzed. RESULTS:This review highlights oxidative stress in tumors, underlying mechanisms of different relationships of ROS and cancer cells, different ROS-mediated therapeutic strategies and the emerging role of microbiota in cancer therapy. CONCLUSION:Cancer cells exhibit increased ROS stress and disturbed redox homeostasis which lead to ROS adaptations. ROS-dependent anticancer therapies including ROS scavenging anticancer therapy and ROS boosting anticancer therapy have shown promising results in vitro as well as in vivo. In addition, response to cancer therapy is modulated by the human microbiota which plays a critical role in systemic body functions.
Emerging evidence for targeting mitochondrial metabolic dysfunction in cancer therapy.
Zhu Yueming,Dean Angela Elizabeth,Horikoshi Nobuo,Heer Collin,Spitz Douglas R,Gius David
The Journal of clinical investigation
Mammalian cells use a complex network of redox-dependent processes necessary to maintain cellular integrity during oxidative metabolism, as well as to protect against and/or adapt to stress. The disruption of these redox-dependent processes, including those in the mitochondria, creates a cellular environment permissive for progression to a malignant phenotype and the development of resistance to commonly used anticancer agents. An extension of this paradigm is that when these mitochondrial functions are altered by the events leading to transformation and ensuing downstream metabolic processes, they can be used as molecular biomarkers or targets in the development of new therapeutic interventions to selectively kill and/or sensitize cancer versus normal cells. In this Review we propose that mitochondrial oxidative metabolism is altered in tumor cells, and the central theme of this dysregulation is electron transport chain activity, folate metabolism, NADH/NADPH metabolism, thiol-mediated detoxification pathways, and redox-active metal ion metabolism. It is proposed that specific subgroups of human malignancies display distinct mitochondrial transformative and/or tumor signatures that may benefit from agents that target these pathways.
Spotlight on ROS and 3-Adrenoreceptors Fighting in Cancer Cells.
Calvani Maura,Subbiani Angela,Vignoli Marina,Favre Claudio
Oxidative medicine and cellular longevity
The role of ROS and RNS is a long-standing debate in cancer. Increasing the concentration of ROS reaching the toxic threshold can be an effective strategy for the reduction of tumor cell viability. On the other hand, cancer cells, by maintaining intracellular ROS concentration at an intermediate level called "mild oxidative stress," promote the activation of signaling that favors tumor progression by increasing cell viability and dangerous tumor phenotype. Many chemotherapeutic treatments induce cell death by rising intracellular ROS concentration. The persistent drug stimulation leads tumor cells to simulate a process called hormesis by which cancer cells exhibit a biphasic response to exposure to drugs used. After a first strong response to a low dose of chemotherapeutic agent, cancer cells start to decrease the response even if high doses of drugs were used. In this framework, 3-adrenoreceptors (3-ARs) fit with an emerging antioxidant role in cancer. 3-ARs are involved in tumor proliferation, angiogenesis, metastasis, and immune tolerance. Its inhibition, by the selective 3-ARs antagonist (SR59230A), leads cancer cells to increase ROS concentration thus inducing cell death and to decrease NO levels thus inhibiting angiogenesis. In this review, we report an overview on reactive oxygen biology in cancer cells focusing on 3-ARs as new players in the antioxidant pathway.
Oxidation of glutamine in HeLa cells: role and control of truncated TCA cycles in tumour mitochondria.
Piva T J,McEvoy-Bowe E
Journal of cellular biochemistry
The oxidative metabolism of glutamine in HeLa cells was investigated using intact cells and isolated mitochondria. The concentrations of the cytoplasmic amino acids were found to be aspartate, 8.0 mM; glutamate, 22.2 mM; glutamine, 11.3 mM; glycine, 9.8 mM; taurine, 2.3 mM; and alanine, < 1 mM. Incubation of the cells with [14C]glutamine gave steady-state recoveries of 14C-label (estimated as exogenous glutamine) in the glutamine, glutamate, and aspartate pools, of 103%, 80%, and 25%, respectively, indicating that glutamine synthetase activity was absent and that a significant proportion of glutamate oxidation proceeded through aspartate aminotransferase. No label was detected in the alanine pool, suggesting that alanine aminotransferase activity was low in these cells. The clearance rate of [14C]glutamine through the cellular compartment was 65 nmol/min per mg protein. There was a 28 s delay after [14C]glutamine was added to the cell before 14C-label was incorporated into the cytoplasm, while the formation of glutamate commenced 10 s later. Aspartate was the major metabolite formed when the mitochondria were incubated in a medium containing either glutamine, glutamate, or glutamate plus malate. The transaminase inhibitor AOA inhibited both aspartate efflux from the mitochondria and respiration. The addition of 2-oxoglutarate failed to relieve glutamate plus malate respiration, indicating that 2-oxoglutarate is part of a well-coupled truncated cycle, of which aspartate aminotransferase has been shown to be a component [Parlo and Coleman (1984): J Biol Chem 259:9997-10003]. This was confirmed by the observation that, although it inhibited respiration, AOA did not affect the efflux of citrate from the mitochondria. Thus citrate does not appear to be a cycle component and is directly transported to the medium. Therefore, it was concluded that the truncated TCA cycle in HeLa cells is the result of both a low rate of citrate synthesis and an active citrate transporter. DNP (10 microM) induced a state III-like respiration only in the presence of succinate, which supports the evidence that NAD-linked dehydrogenases were not coupled to respiration, and suggests that these mitochondria may have a defect in complex I of the electron transport chain. Arising from the present results with HeLa cells and results extant in the literature, it has been proposed that a major regulating mechanism for the flux of glutamate carbon in tumour cells is the competitive inhibition exerted by 2-oxoglutarate on aspartate and alanine aminotransferases. This has been discussed and applied to the data.
Succinate links TCA cycle dysfunction to oncogenesis by inhibiting HIF-alpha prolyl hydroxylase.
Selak Mary A,Armour Sean M,MacKenzie Elaine D,Boulahbel Houda,Watson David G,Mansfield Kyle D,Pan Yi,Simon M Celeste,Thompson Craig B,Gottlieb Eyal
Several mitochondrial proteins are tumor suppressors. These include succinate dehydrogenase (SDH) and fumarate hydratase, both enzymes of the tricarboxylic acid (TCA) cycle. However, to date, the mechanisms by which defects in the TCA cycle contribute to tumor formation have not been elucidated. Here we describe a mitochondrion-to-cytosol signaling pathway that links mitochondrial dysfunction to oncogenic events: succinate, which accumulates as a result of SDH inhibition, inhibits HIF-alpha prolyl hydroxylases in the cytosol, leading to stabilization and activation of HIF-1alpha. These results suggest a mechanistic link between SDH mutations and HIF-1alpha induction, providing an explanation for the highly vascular tumors that develop in the absence of VHL mutations.
Opportunities in discovery and delivery of anticancer drugs targeting mitochondria and cancer cell metabolism.
Pathania Divya,Millard Melissa,Neamati Nouri
Advanced drug delivery reviews
Cancer cells are characterized by self-sufficiency in the absence of growth signals, their ability to evade apoptosis, resistance to anti-growth signals, sustained angiogenesis, uncontrolled proliferation, and invasion and metastasis. Alterations in cellular bioenergetics are an emerging hallmark of cancer. The mitochondrion is the major organelle implicated in the cellular bioenergetic and biosynthetic changes accompanying cancer. These bioenergetic modifications contribute to the invasive, metastatic and adaptive properties typical in most tumors. Moreover, mitochondrial DNA mutations complement the bioenergetic changes in cancer. Several cancer management therapies have been proposed that target tumor cell metabolism and mitochondria. Glycolytic inhibitors serve as a classical example of cancer metabolism targeting agents. Several TCA cycle and OXPHOS inhibitors are being tested for their anticancer potential. Moreover, agents targeting the PDC/PDK (pyruvate dehydrogenase complex/pyruvate dehydrogenase kinase) interaction are being studied for reversal of Warburg effect. Targeting of the apoptotic regulatory machinery of mitochondria is another potential anticancer field in need of exploration. Additionally, oxidative phosphorylation uncouplers, potassium channel modulators, and mitochondrial redox are under investigation for their anticancer potential. To this end there is an increased demand for agents that specifically hit their target. Delocalized lipophilic cations have shown tremendous potential in delivering anticancer agents selectively to tumor cells. This review provides an overview of the potential anticancer agents that act by targeting cancer cell metabolism and mitochondria, and also brings us face to face with the emerging opportunities in cancer therapy.
Revisiting the TCA cycle: signaling to tumor formation.
Raimundo Nuno,Baysal Bora E,Shadel Gerald S
Trends in molecular medicine
A role for mitochondria in tumor formation is suggested by mutations in enzymes of the TCA cycle: isocitrate dehydrogenase (IDH), succinate dehydrogenase (SDH) and fumarate hydratase (FH). Although they are all components of the TCA cycle, the resulting clinical presentations do not overlap. Activation of the hypoxia pathway can explain SDH phenotypes, but recent data suggest that FH and IDH mutations lead to tumor formation by repressing cellular differentiation. In this review, we discuss recent findings in the context of both mitochondrial and cytoplasmic components of the TCA cycle, and we propose that extrametabolic roles of TCA cycle metabolites result in reduced cellular differentiation. Furthermore, activation of the pseudohypoxia pathway likely promotes the growth of these neoplasias into tumors.
Haem oxygenase is synthetically lethal with the tumour suppressor fumarate hydratase.
Frezza Christian,Zheng Liang,Folger Ori,Rajagopalan Kartik N,MacKenzie Elaine D,Jerby Livnat,Micaroni Massimo,Chaneton Barbara,Adam Julie,Hedley Ann,Kalna Gabriela,Tomlinson Ian P M,Pollard Patrick J,Watson Dave G,Deberardinis Ralph J,Shlomi Tomer,Ruppin Eytan,Gottlieb Eyal
Fumarate hydratase (FH) is an enzyme of the tricarboxylic acid cycle (TCA cycle) that catalyses the hydration of fumarate into malate. Germline mutations of FH are responsible for hereditary leiomyomatosis and renal-cell cancer (HLRCC). It has previously been demonstrated that the absence of FH leads to the accumulation of fumarate, which activates hypoxia-inducible factors (HIFs) at normal oxygen tensions. However, so far no mechanism that explains the ability of cells to survive without a functional TCA cycle has been provided. Here we use newly characterized genetically modified kidney mouse cells in which Fh1 has been deleted, and apply a newly developed computer model of the metabolism of these cells to predict and experimentally validate a linear metabolic pathway beginning with glutamine uptake and ending with bilirubin excretion from Fh1-deficient cells. This pathway, which involves the biosynthesis and degradation of haem, enables Fh1-deficient cells to use the accumulated TCA cycle metabolites and permits partial mitochondrial NADH production. We predicted and confirmed that targeting this pathway would render Fh1-deficient cells non-viable, while sparing wild-type Fh1-containing cells. This work goes beyond identifying a metabolic pathway that is induced in Fh1-deficient cells to demonstrate that inhibition of haem oxygenation is synthetically lethal when combined with Fh1 deficiency, providing a new potential target for treating HLRCC patients.
Mitochondrial dysfunctions in cancer: genetic defects and oncogenic signaling impinging on TCA cycle activity.
Desideri Enrico,Vegliante Rolando,Ciriolo Maria Rosa
The tricarboxylic acid (TCA) cycle is a central route for oxidative metabolism. Besides being responsible for the production of NADH and FADH2, which fuel the mitochondrial electron transport chain to generate ATP, the TCA cycle is also a robust source of metabolic intermediates required for anabolic reactions. This is particularly important for highly proliferating cells, like tumour cells, which require a continuous supply of precursors for the synthesis of lipids, proteins and nucleic acids. A number of mutations among the TCA cycle enzymes have been discovered and their association with some tumour types has been established. In this review we summarise the current knowledge regarding alterations of the TCA cycle in tumours, with particular attention to the three germline mutations of the enzymes succinate dehydrogenase, fumarate hydratase and isocitrate dehydrogenase, which are involved in the pathogenesis of tumours, and to the aberrant regulation of TCA cycle components that are under the control of oncogenes and tumour suppressors.
Vitamin D, intermediary metabolism and prostate cancer tumor progression.
Wang Wei-Lin W,Tenniswood Martin
Frontiers in physiology
Epidemiological data have demonstrated an inverse association between serum vitamin D3 levels, cancer incidence and related mortality. However, the effects of vitamin D on prostate cancer biology and its utility for prevention of prostate cancer progression are not as well-defined. The data are often conflicting: some reports suggest that vitamin D3 induces apoptosis in androgen dependent prostate cancer cell lines, while others suggest that vitamin D3 only induces cell cycle arrest. Recent molecular studies have identified an extensive synergistic crosstalk between the vitamin D- and androgen-mediated mRNA and miRNA expression, adding an additional layer of post-transcriptional regulation to the known VDR- and AR-regulated gene activation. The Warburg effect, the inefficient metabolic pathway that converts glucose to lactate for rapid energy generation, is a phenomenon common to many different types of cancer. This process supports cell proliferation and promotes cancer progression via alteration of glucose, glutamine and lipid metabolism. Prostate cancer is a notable exception to this general process since the metabolic switch that occurs early during malignancy is the reverse of the Warburg effect. This "anti-Warburg effect" is due to the unique biology of normal prostate cells that harbor a truncated TCA cycle that is required to produce and secret citrate. In prostate cancer cells, the TCA cycle activity is restored and citrate oxidation is used to produce energy for cancer cell proliferation. 1,25(OH)2D3 and androgen together modulates the TCA cycle via transcriptional regulation of zinc transporters, suggesting that 1,25(OH)2D3 and androgen maintain normal prostate metabolism by blocking citrate oxidation. These data demonstrate the importance of androgens in the anti-proliferative effect of vitamin D in prostate cancer and highlight the importance of understanding the crosstalk between these two signaling pathways.
Blocking anaplerotic entry of glutamine into the TCA cycle sensitizes K-Ras mutant cancer cells to cytotoxic drugs.
Saqcena M,Mukhopadhyay S,Hosny C,Alhamed A,Chatterjee A,Foster D A
Cancer cells undergo a metabolic transformation that allows for increased anabolic demands, wherein glycolytic and tricarboxylic acid (TCA) cycle intermediates are shunted away for the synthesis of biological molecules required for cell growth and division. One of the key shunts is the exit of citrate from the mitochondria and the TCA cycle for the generation of cytosolic acetyl-coenzyme A that can be used for fatty acid and cholesterol biosynthesis. With the loss of mitochondrial citrate, cancer cells rely on the 'conditionally essential' amino acid glutamine (Q) as an anaplerotic carbon source for TCA cycle intermediates. Although Q deprivation causes G1 cell cycle arrest in non-transformed cells, its impact on the cancer cell cycle is not well characterized. We report here a correlation between bypass of the Q-dependent G1 checkpoint and cancer cells harboring K-Ras mutations. Instead of arresting in G1 in response to Q-deprivation, K-Ras-driven cancer cells arrest in either S- or G2/M-phase. Inhibition of K-Ras effector pathways was able to revert cells to G1 arrest upon Q deprivation. Blocking anaplerotic utilization of Q mimicked Q deprivation--causing S- and G2/M-phase arrest in K-Ras mutant cancer cells. Significantly, Q deprivation or suppression of anaplerotic Q utilization created synthetic lethality to the cell cycle phase-specific cytotoxic drugs, capecitabine and paclitaxel. These data suggest that disabling of the G1 Q checkpoint could represent a novel vulnerability of cancer cells harboring K-Ras and possibly other mutations that disable the Q-dependent checkpoint.
Fumarate induces redox-dependent senescence by modifying glutathione metabolism.
Zheng Liang,Cardaci Simone,Jerby Livnat,MacKenzie Elaine D,Sciacovelli Marco,Johnson T Isaac,Gaude Edoardo,King Ayala,Leach Joshua D G,Edrada-Ebel RuAngelie,Hedley Ann,Morrice Nicholas A,Kalna Gabriela,Blyth Karen,Ruppin Eytan,Frezza Christian,Gottlieb Eyal
Mutations in the tricarboxylic acid (TCA) cycle enzyme fumarate hydratase (FH) are associated with a highly malignant form of renal cancer. We combined analytical chemistry and metabolic computational modelling to investigate the metabolic implications of FH loss in immortalized and primary mouse kidney cells. Here, we show that the accumulation of fumarate caused by the inactivation of FH leads to oxidative stress that is mediated by the formation of succinicGSH, a covalent adduct between fumarate and glutathione. Chronic succination of GSH, caused by the loss of FH, or by exogenous fumarate, leads to persistent oxidative stress and cellular senescence in vitro and in vivo. Importantly, the ablation of p21, a key mediator of senescence, in Fh1-deficient mice resulted in the transformation of benign renal cysts into a hyperplastic lesion, suggesting that fumarate-induced senescence needs to be bypassed for the initiation of renal cancers.
Loss of succinate dehydrogenase activity results in dependency on pyruvate carboxylation for cellular anabolism.
The tricarboxylic acid (TCA) cycle is a central metabolic pathway responsible for supplying reducing potential for oxidative phosphorylation and anabolic substrates for cell growth, repair and proliferation. As such it thought to be essential for cell proliferation and tissue homeostasis. However, since the initial report of an inactivating mutation in the TCA cycle enzyme complex, succinate dehydrogenase (SDH) in paraganglioma (PGL), it has become clear that some cells and tissues are not only able to survive with a truncated TCA cycle, but that they are also able of supporting proliferative phenotype observed in tumours. Here, we show that loss of SDH activity leads to changes in the metabolism of non-essential amino acids. In particular, we demonstrate that pyruvate carboxylase is essential to re-supply the depleted pool of aspartate in SDH-deficient cells. Our results demonstrate that the loss of SDH reduces the metabolic plasticity of cells, suggesting vulnerabilities that can be targeted therapeutically.
The Emerging Hallmarks of Cancer Metabolism.
Pavlova Natalya N,Thompson Craig B
Tumorigenesis is dependent on the reprogramming of cellular metabolism as both direct and indirect consequence of oncogenic mutations. A common feature of cancer cell metabolism is the ability to acquire necessary nutrients from a frequently nutrient-poor environment and utilize these nutrients to both maintain viability and build new biomass. The alterations in intracellular and extracellular metabolites that can accompany cancer-associated metabolic reprogramming have profound effects on gene expression, cellular differentiation, and the tumor microenvironment. In this Perspective, we have organized known cancer-associated metabolic changes into six hallmarks: (1) deregulated uptake of glucose and amino acids, (2) use of opportunistic modes of nutrient acquisition, (3) use of glycolysis/TCA cycle intermediates for biosynthesis and NADPH production, (4) increased demand for nitrogen, (5) alterations in metabolite-driven gene regulation, and (6) metabolic interactions with the microenvironment. While few tumors display all six hallmarks, most display several. The specific hallmarks exhibited by an individual tumor may ultimately contribute to better tumor classification and aid in directing treatment.
The emerging role and targetability of the TCA cycle in cancer metabolism.
Anderson Nicole M,Mucka Patrick,Kern Joseph G,Feng Hui
Protein & cell
The tricarboxylic acid (TCA) cycle is a central route for oxidative phosphorylation in cells, and fulfills their bioenergetic, biosynthetic, and redox balance requirements. Despite early dogma that cancer cells bypass the TCA cycle and primarily utilize aerobic glycolysis, emerging evidence demonstrates that certain cancer cells, especially those with deregulated oncogene and tumor suppressor expression, rely heavily on the TCA cycle for energy production and macromolecule synthesis. As the field progresses, the importance of aberrant TCA cycle function in tumorigenesis and the potentials of applying small molecule inhibitors to perturb the enhanced cycle function for cancer treatment start to evolve. In this review, we summarize current knowledge about the fuels feeding the cycle, effects of oncogenes and tumor suppressors on fuel and cycle usage, common genetic alterations and deregulation of cycle enzymes, and potential therapeutic opportunities for targeting the TCA cycle in cancer cells. With the application of advanced technology and in vivo model organism studies, it is our hope that studies of this previously overlooked biochemical hub will provide fresh insights into cancer metabolism and tumorigenesis, subsequently revealing vulnerabilities for therapeutic interventions in various cancer types.
Cytosolic Aspartate Availability Determines Cell Survival When Glutamine Is Limiting.
Alkan H Furkan,Walter Katharina E,Luengo Alba,Madreiter-Sokolowski Corina T,Stryeck Sarah,Lau Allison N,Al-Zoughbi Wael,Lewis Caroline A,Thomas Craig J,Hoefler Gerald,Graier Wolfgang F,Madl Tobias,Vander Heiden Matthew G,Bogner-Strauss Juliane G
Mitochondrial function is important for aspartate biosynthesis in proliferating cells. Here, we show that mitochondrial aspartate export via the aspartate-glutamate carrier 1 (AGC1) supports cell proliferation and cellular redox homeostasis. Insufficient cytosolic aspartate delivery leads to cell death when TCA cycle carbon is reduced following glutamine withdrawal and/or glutaminase inhibition. Moreover, loss of AGC1 reduces allograft tumor growth that is further compromised by treatment with the glutaminase inhibitor CB-839. Together, these findings argue that mitochondrial aspartate export sustains cell survival in low-glutamine environments and AGC1 inhibition can synergize with glutaminase inhibition to limit tumor growth.
Cancer-associated mutation and beyond: The emerging biology of isocitrate dehydrogenases in human disease.
Tommasini-Ghelfi Serena,Murnan Kevin,Kouri Fotini M,Mahajan Akanksha S,May Jasmine L,Stegh Alexander H
Isocitrate dehydrogenases (IDHs) are critical metabolic enzymes that catalyze the oxidative decarboxylation of isocitrate to α-ketoglutarate (αKG), NAD(P)H, and CO. IDHs epigenetically control gene expression through effects on αKG-dependent dioxygenases, maintain redox balance and promote anaplerosis by providing cells with NADPH and precursor substrates for macromolecular synthesis, and regulate respiration and energy production through generation of NADH. Cancer-associated mutations in and represent one of the most comprehensively studied mechanisms of IDH pathogenic effect. Mutant enzymes produce ()-2-hydroxyglutarate, which in turn inhibits αKG-dependent dioxygenase function, resulting in a global hypermethylation phenotype, increased tumor cell multipotency, and malignancy. Recent studies identified wild-type IDHs as critical regulators of normal organ physiology and, when transcriptionally induced or down-regulated, as contributing to cancer and neurodegeneration, respectively. We describe how mutant and wild-type enzymes contribute on molecular levels to disease pathogenesis, and discuss efforts to pharmacologically target IDH-controlled metabolic rewiring.
Disrupting Mitochondrial Pyruvate Uptake Directs Glutamine into the TCA Cycle away from Glutathione Synthesis and Impairs Hepatocellular Tumorigenesis.
Tompkins Sean C,Sheldon Ryan D,Rauckhorst Adam J,Noterman Maria F,Solst Shane R,Buchanan Jane L,Mapuskar Kranti A,Pewa Alvin D,Gray Lawrence R,Oonthonpan Lalita,Sharma Arpit,Scerbo Diego A,Dupuy Adam J,Spitz Douglas R,Taylor Eric B
Hepatocellular carcinoma (HCC) is a devastating cancer increasingly caused by non-alcoholic fatty liver disease (NAFLD). Disrupting the liver Mitochondrial Pyruvate Carrier (MPC) in mice attenuates NAFLD. Thus, we considered whether liver MPC disruption also prevents HCC. Here, we use the N-nitrosodiethylamine plus carbon tetrachloride model of HCC development to test how liver-specific MPC knock out affects hepatocellular tumorigenesis. Our data show that liver MPC ablation markedly decreases tumorigenesis and that MPC-deficient tumors transcriptomically downregulate glutathione metabolism. We observe that MPC disruption and glutathione depletion in cultured hepatomas are synthetically lethal. Stable isotope tracing shows that hepatocyte MPC disruption reroutes glutamine from glutathione synthesis into the tricarboxylic acid (TCA) cycle. These results support a model where inducing metabolic competition for glutamine by MPC disruption impairs hepatocellular tumorigenesis by limiting glutathione synthesis. These findings raise the possibility that combining MPC disruption and glutathione stress may be therapeutically useful in HCC and additional cancers.
Rescue of TCA Cycle Dysfunction for Cancer Therapy.
Marquez Jubert,Flores Jessa,Kim Amy Hyein,Nyamaa Bayalagmaa,Nguyen Anh Thi Tuyet,Park Nammi,Han Jin
Journal of clinical medicine
Mitochondrion, a maternally hereditary, subcellular organelle, is the site of the tricarboxylic acid (TCA) cycle, electron transport chain (ETC), and oxidative phosphorylation (OXPHOS)-the basic processes of ATP production. Mitochondrial function plays a pivotal role in the development and pathology of different cancers. Disruption in its activity, like mutations in its TCA cycle enzymes, leads to physiological imbalances and metabolic shifts of the cell, which contributes to the progression of cancer. In this review, we explored the different significant mutations in the mitochondrial enzymes participating in the TCA cycle and the diseases, especially cancer types, that these malfunctions are closely associated with. In addition, this paper also discussed the different therapeutic approaches which are currently being developed to address these diseases caused by mitochondrial enzyme malfunction.
Colorectal cancers utilize glutamine as an anaplerotic substrate of the TCA cycle in vivo.
Zhao Yiqing,Zhao Xuan,Chen Vanessa,Feng Ying,Wang Lan,Croniger Colleen,Conlon Ronald A,Markowitz Sanford,Fearon Eric,Puchowicz Michelle,Brunengraber Henri,Hao Yujun,Wang Zhenghe
Cancer cells in culture rely on glutamine as an anaplerotic substrate to replenish tricarboxylic acid (TCA) cycle intermediates that have been consumed. but it is uncertain whether cancers in vivo depend on glutamine for anaplerosis. Here, following in vivo infusions of [C]-glutamine in mice bearing subcutaneous colon cancer xenografts, we showed substantial amounts of infused [C]-glutamine enters the TCA cycle in the tumors. Consistent with our prior observation that colorectal cancers (CRCs) with oncogenic mutations in the phosphatidylinositol-4,5-bisphosphate 3-kinase catalytic (PIK3CA) subunit are more dependent on glutamine than CRCs with wild type PIK3CA, labeling from glutamine to most TCA cycle intermediates was higher in PIK3CA-mutant subcutaneous xenograft tumors than in wild type PIK3CA tumors. Moreover, using orthotopic mouse colon tumors estalished from human CRC cells or patient-derived xenografts, we demonstrated substantial amounts of infused [C]-glutamine enters the TCA cycle in the tumors and tumors utilize anaplerotic glutamine to a greater extent than adjacent normal colon tissues. Similar results were seen in spontaneous colon tumors arising in genetically engineered mice. Our studies provide compelling evidence CRCs utilizes glutamine to replenish the TCA cycle in vivo, suggesting that targeting glutamine metabolism could be a therapeutic approach for CRCs, especially for PIK3CA-mutant CRCs.
TCA Cycle Rewiring as Emerging Metabolic Signature of Hepatocellular Carcinoma.
Todisco Simona,Convertini Paolo,Iacobazzi Vito,Infantino Vittoria
Hepatocellular carcinoma (HCC) is a common malignancy. Despite progress in treatment, HCC is still one of the most lethal cancers. Therefore, deepening molecular mechanisms underlying HCC pathogenesis and development is required to uncover new therapeutic strategies. Metabolic reprogramming is emerging as a critical player in promoting tumor survival and proliferation to sustain increased metabolic needs of cancer cells. Among the metabolic pathways, the tricarboxylic acid (TCA) cycle is a primary route for bioenergetic, biosynthetic, and redox balance requirements of cells. In recent years, a large amount of evidence has highlighted the relevance of the TCA cycle rewiring in a variety of cancers. Indeed, aberrant gene expression of several key enzymes and changes in levels of critical metabolites have been observed in many solid human tumors. In this review, we summarize the role of the TCA cycle rewiring in HCC by reporting gene expression and activity dysregulation of enzymes relating not only to the TCA cycle but also to glutamine metabolism, malate/aspartate, and citrate/pyruvate shuttles. Regarding the transcriptional regulation, we focus on the link between NF-κB-HIF1 transcriptional factors and TCA cycle reprogramming. Finally, the potential of metabolic targets for new HCC treatments has been explored.
O-GlcNAcylation of PGK1 coordinates glycolysis and TCA cycle to promote tumor growth.
Nie Hao,Ju Haixing,Fan Jiayi,Shi Xiaoliu,Cheng Yaxian,Cang Xiaohui,Zheng Zhiguo,Duan Xiaotao,Yi Wen
Many cancer cells display enhanced glycolysis and suppressed mitochondrial metabolism. This phenomenon, known as the Warburg effect, is critical for tumor development. However, how cancer cells coordinate glucose metabolism through glycolysis and the mitochondrial tricarboxylic acid (TCA) cycle is largely unknown. We demonstrate here that phosphoglycerate kinase 1 (PGK1), the first ATP-producing enzyme in glycolysis, is reversibly and dynamically modified with O-linked N-acetylglucosamine (O-GlcNAc) at threonine 255 (T255). O-GlcNAcylation activates PGK1 activity to enhance lactate production, and simultaneously induces PGK1 translocation into mitochondria. Inside mitochondria, PGK1 acts as a kinase to inhibit pyruvate dehydrogenase (PDH) complex to reduce oxidative phosphorylation. Blocking T255 O-GlcNAcylation of PGK1 decreases colon cancer cell proliferation, suppresses glycolysis, enhances the TCA cycle, and inhibits tumor growth in xenograft models. Furthermore, PGK1 O-GlcNAcylation levels are elevated in human colon cancers. This study highlights O-GlcNAcylation as an important signal for coordinating glycolysis and the TCA cycle to promote tumorigenesis.
Metabolic changes related to the IDH1 mutation in gliomas preserve TCA-cycle activity: An investigation at the protein level.
Dekker Lennard J M,Wu Suying,Jurriëns Cherise,Mustafa Dana A N,Grevers Frederieke,Burgers Peter C,Sillevis Smitt Peter A E,Kros Johan M,Luider Theo M
FASEB journal : official publication of the Federation of American Societies for Experimental Biology
The discovery of the IDH1 R132H (IDH1 mut) mutation in low-grade glioma and the associated change in function of the IDH1 enzyme has increased the interest in glioma metabolism. In an earlier study, we found that changes in expression of genes involved in the aerobic glycolysis and the TCA cycle are associated with IDH1 mut. Here, we apply proteomics to FFPE samples of diffuse gliomas with or without IDH1 mutations, to map changes in protein levels associated with this mutation. We observed significant changes in the enzyme abundance associated with aerobic glycolysis, glutamate metabolism, and the TCA cycle in IDH1 mut gliomas. Specifically, the enzymes involved in the metabolism of glutamate, lactate, and enzymes involved in the conversion of α-ketoglutarate were increased in IDH1 mut gliomas. In addition, the bicarbonate transporter (SLC4A4) was increased in IDH1 mut gliomas, supporting the idea that a mechanism preventing intracellular acidification is active. We also found that enzymes that convert proline, valine, leucine, and isoleucine into glutamate were increased in IDH1 mut glioma. We conclude that in IDH1 mut glioma metabolism is rewired (increased input of lactate and glutamate) to preserve TCA-cycle activity in IDH1 mut gliomas.
Mitochondrial ubiquinol oxidation is necessary for tumour growth.
Martínez-Reyes Inmaculada,Cardona Luzivette Robles,Kong Hyewon,Vasan Karthik,McElroy Gregory S,Werner Marie,Kihshen Hermon,Reczek Colleen R,Weinberg Samuel E,Gao Peng,Steinert Elizabeth M,Piseaux Raul,Budinger G R Scott,Chandel Navdeep S
The mitochondrial electron transport chain (ETC) is necessary for tumour growth and its inhibition has demonstrated anti-tumour efficacy in combination with targeted therapies. Furthermore, human brain and lung tumours display robust glucose oxidation by mitochondria. However, it is unclear why a functional ETC is necessary for tumour growth in vivo. ETC function is coupled to the generation of ATP-that is, oxidative phosphorylation and the production of metabolites by the tricarboxylic acid (TCA) cycle. Mitochondrial complexes I and II donate electrons to ubiquinone, resulting in the generation of ubiquinol and the regeneration of the NAD+ and FAD cofactors, and complex III oxidizes ubiquinol back to ubiquinone, which also serves as an electron acceptor for dihydroorotate dehydrogenase (DHODH)-an enzyme necessary for de novo pyrimidine synthesis. Here we show impaired tumour growth in cancer cells that lack mitochondrial complex III. This phenotype was rescued by ectopic expression of Ciona intestinalis alternative oxidase (AOX), which also oxidizes ubiquinol to ubiquinone. Loss of mitochondrial complex I, II or DHODH diminished the tumour growth of AOX-expressing cancer cells deficient in mitochondrial complex III, which highlights the necessity of ubiquinone as an electron acceptor for tumour growth. Cancer cells that lack mitochondrial complex III but can regenerate NAD+ by expression of the NADH oxidase from Lactobacillus brevis (LbNOX) targeted to the mitochondria or cytosol were still unable to grow tumours. This suggests that regeneration of NAD+ is not sufficient to drive tumour growth in vivo. Collectively, our findings indicate that tumour growth requires the ETC to oxidize ubiquinol, which is essential to drive the oxidative TCA cycle and DHODH activity.
AMPK maintains TCA cycle through sequential phosphorylation of PDHA to promote tumor metastasis.
Cai Zhen,Peng Danni,Lin Hui-Kuan
Cancer represents the leading public health problem throughout the world. Globally, about one out of six deaths is related to cancer, which is largely due to the metastatic lesions. However, there are no effective strategies for targeting cancer metastasis. Identification of the key druggable targets maintaining metastasis is crucial for cancer treatment. In our recent study (Cai et al. (2020), Mol Cell, doi: 10.1016/j.molcel.2020.09.018), we found that activity of AMPK was enriched in metastatic tumors compared to primary tumors. Depletion of AMPK rendered cancer cells more sensitive to metabolic and oxidative stress, leading to the impairment of breast cancer lung metastasis. Activation of AMPK rewired cancer metabolism towards TCA cycle, which protects disseminated cancer cells from both metabolic and oxidative stress-induced cell death, and facilitates cancer metastasis. Further, AMPK critically maintained the activity of pyruvate dehydrogenase complex (PDH), the rate limiting enzyme involved in TCA cycle, thus favoring the pyruvate metabolism towards TCA cycle rather than converting it to lactate. Mechanistically, AMPK was shown to co-localize with PDHA, the catalytic subunit of PDH, in the mitochondrial matrix and directly triggered the phosphorylation of PDHA on Ser295 and Ser314. Hyper-phosphorylation of Ser295 and Ser314 of PDHA promotes lung metastasis through elevating activity of PDH. Of note, PDHA Ser314 phosphorylation abrogated the interaction between PDHA and PDHKs leading to the dephosphorylation on previously reported S293 site, whose phosphorylation serves as a negative signal for PDH activation, while S295 phosphorylation serves as an intrinsic catalytic site required for pyruvate metabolism. Our study presented the first evidence for the pro-metastatic property of the AMPK-PDH axis and advance our current understanding of how PDH is activated under physiological and pathological conditions.