The role of phosphometabolites in cell proliferation, energy metabolism, and tumor therapy

Targeting metabolic reprogramming in hepatocellular carcinoma to overcome therapeutic resistance: A comprehensive review

Hepatocellular carcinoma (HCC) poses a heavy burden on human health with high morbidity and mortality rates. Systematic therapy is crucial for advanced and mid-term HCC, but faces a significant challenge from therapeutic resistance, weakening drug effectiveness. Metabolic reprogramming has gained attention as a key contributor to therapeutic resistance. Cells change their metabolism to meet energy demands, adapt to growth needs, or resist environmental pressures. Understanding key enzyme expression patterns and metabolic pathway interactions is vital to comprehend HCC occurrence, development, and treatment resistance. Exploring metabolic enzyme reprogramming and pathways is essential to identify breakthrough points for HCC treatment. Targeting metabolic enzymes with inhibitors is key to addressing these points. Inhibitors, combined with systemic therapeutic drugs, can alleviate resistance, prolong overall survival for advanced HCC, and offer mid-term HCC patients a chance for radical resection. Advances in metabolic research methods, from genomics to metabolomics and cells to organoids, help build the HCC metabolic reprogramming network. Recent progress in biomaterials and nanotechnology impacts drug targeting and effectiveness, providing new solutions for systemic therapeutic drug resistance. This review focuses on metabolic enzyme changes, pathway interactions, enzyme inhibitors, research methods, and drug delivery targeting metabolic reprogramming, offering valuable references for metabolic approaches to HCC treatment.

Dose-dependent toxic effects of di-(2-ethylhexyl) phthalate in male rats: Focus on behavioral alterations and inducing TLR4/NF-κB signaling pathway

Di -(2-ethylhexyl) phthalate (DEHP) is a widely used phthalate that possesses a public health concern. Different concentrations of DEHP, including 50, 300, and 750 mg/kg, were administrated orally for 28 days in male rats. Body weight and vital organs weight were measured as well as anxiety-like behavior, short and long-term memory were investigated. Brain inflammatory cytokines, including IL-1β, TLR4, NF-κB, TNF-α, and IL1-6, were assessed. Brain caspase-3, neuropeptide-Y (NPY), and brain histopathology were also evaluated. DEHP triggers the release of pro-inflammatory cytokines via inducing the nuclear translocation of the signaling pathway; TLR 4/ NF-κB leads to cognitive impairment and neurodegeneration, which is confirmed by the impaired brain architecture. Also, DEHP upgrades the expression levels of brain caspase-3 and NPY. In conclusion, exposure to high doses of DEHP persuades great toxicity visualized by behavioral, biochemical, and histological impairments when compared to the low dose.

Glutamine-Driven Metabolic Adaptation to COVID-19 Infection

Background

COVID-19 is known to be transmitted by direct contact, droplets or feces/orally. There are many factors which determines the clinical progression of the disease. Aminoacid disturbance in viral disease is shown in many studies. İn this study we aimed to evaluate the change of aminoacid metabolism especially the aspartate, glutamine and glycine levels which have been associated with an immune defence effect in viral disease.

Methods

Blood samples from 35 volunteer patients with COVID-19, concretized diagnosis was made by oropharyngeal from nazofaringeal swab specimens and reverse transcriptase-polymerase chain reaction, and 35 control group were analyzed. The amino acid levels were measured with liquid chromatography-mass spectrometry technology. Two groups were compared by Kolmogorov-Smirnov analysis, Kruskal-Wallis and the Mann-Whitney U. The square test was used to evaluate the tests obtained by counting, and the error level was taken as 0.05.

Results

The average age of the patient and control group were 48.5 ± 14.9 and 48.8 ± 14.6 years respectively. The decrease in aspartate (p = 5.5 × 10^-9) and glutamine levels (p = 9.0 × 10^-17) were significiantly in COVID group, whereas Glycine (p = 0.243) increase was not significiant.

Conclusions

Metabolic pathways, are affected in rapidly dividing cells in viral diseases which are important for immun defence. We determined that aspartate, glutamine and glycine levels in Covid 19 patients were affected by the warburg effect, malate aspartate shuttle, glutaminolysis and pentose phosphate pathway. Enteral or parenteral administration of these plasma amino acid levels will correct the duration and pathophysiology of the patients' stay in hospital and intensive care.

Mitochondrial Dysfunction: Pathophysiology and Mitochondria-Targeted Drug Delivery Approaches

Mitochondria are implicated in a wide range of functions apart from ATP generation, and, therefore, constitute one of the most important organelles of cell. Since healthy mitochondria are essential for proper cellular functioning and survival, mitochondrial dysfunction may lead to various pathologies. Mitochondria are considered a novel and promising therapeutic target for the diagnosis, treatment, and prevention of various human diseases including metabolic disorders, cancer, and neurodegenerative diseases. For mitochondria-targeted therapy, there is a need to develop an effective drug delivery approach, owing to the mitochondrial special bilayer structure through which therapeutic molecules undergo multiple difficulties in reaching the core. In recent years, various nanoformulations have been designed such as polymeric nanoparticles, liposomes, inorganic nanoparticles conjugate with mitochondriotropic moieties such as mitochondria-penetrating peptides (MPPs), triphenylphosphonium (TPP), dequalinium (DQA), and mitochondrial protein import machinery for overcoming barriers involved in targeting mitochondria. The current approaches used for mitochondria-targeted drug delivery have provided promising ways to overcome the challenges associated with targeted-drug delivery. Herein, we review the research from past years to the current scenario that has identified mitochondrial dysfunction as a major contributor to the pathophysiology of various diseases. Furthermore, we discuss the recent advancements in mitochondria-targeted drug delivery strategies for the pathologies associated with mitochondrial dysfunction.

Mitochondrial Genetic and Epigenetic Regulations in Cancer: Therapeutic Potential

Mitochondria are dynamic organelles managing crucial processes of cellular metabolism and bioenergetics. Enabling rapid cellular adaptation to altered endogenous and exogenous environments, mitochondria play an important role in many pathophysiological states, including cancer. Being under the control of mitochondrial and nuclear DNA (mtDNA and nDNA), mitochondria adjust their activity and biogenesis to cell demands. In cancer, numerous mutations in mtDNA have been detected, which do not inactivate mitochondrial functions but rather alter energy metabolism to support cancer cell growth. Increasing evidence suggests that mtDNA mutations, mtDNA epigenetics and miRNA regulations dynamically modify signalling pathways in an altered microenvironment, resulting in cancer initiation and progression and aberrant therapy response. In this review, we discuss mitochondria as organelles importantly involved in tumorigenesis and anti-cancer therapy response. Tumour treatment unresponsiveness still represents a serious drawback in current drug therapies. Therefore, studying aspects related to genetic and epigenetic control of mitochondria can open a new field for understanding cancer therapy response. The urgency of finding new therapeutic regimens with better treatment outcomes underlines the targeting of mitochondria as a suitable candidate with new therapeutic potential. Understanding the role of mitochondria and their regulation in cancer development, progression and treatment is essential for the development of new safe and effective mitochondria-based therapeutic regimens.

AK2 is an AMP-sensing negative regulator of BRAF in tumorigenesis

The RAS-BRAF signaling is a major pathway of cell proliferation and their mutations are frequently found in human cancers. Adenylate kinase 2 (AK2), which modulates balance of adenine nucleotide pool, has been implicated in cell death and cell proliferation independently of its enzyme activity. Recently, the role of AK2 in tumorigenesis was in part elucidated in some cancer types including lung adenocarcinoma and breast cancer, but the underlying mechanism is not clear. Here, we show that AK2 is a BRAF-suppressor. In in vitro assays and cell model, AK2 interacted with BRAF and inhibited BRAF activity and downstream ERK phosphorylation. Energy-deprived conditions in cell model and the addition of AMP to cell lysates strengthened the AK2-BRAF interaction, suggesting that AK2 is involved in the regulation of BRAF activity in response to cell metabolic state. AMP facilitated the AK2-BRAF complex formation through binding to AK2. In a panel of HCC cell lines, AK2 expression was inversely correlated with ERK/MAPK activation, and AK2-knockdown or -knockout increased BRAF activity and promoted cell proliferation. Tumors from HCC patients showed low-AK2 protein expression and increased ERK activation compared to non-tumor tissues and the downregulation of AK2 was also verified by two microarray datasets (TCGA-LIHC and GSE14520). Moreover, AK2/BRAF interaction was abrogated by RAS activation in in vitro assay and cell model and in a mouse model of HRAS^G12V-driven HCC, and AK2 ablation promoted tumor growth and BRAF activity. AK2 also bound to BRAF inhibitor-insensitive BRAF mutants and attenuated their activities. These findings indicate that AK2 monitoring cellular AMP levels is indeed a negative regulator of BRAF, linking the metabolic status to tumor growth.

Nuclear Magnetic Resonance Spectroscopy in Clinical Metabolomics and Personalized Medicine: Current Challenges and Perspectives

Personalized medicine is probably the most promising area being developed in modern medicine. This approach attempts to optimize the therapies and the patient care based on the individual patient characteristics. Its success highly depends on the way the characterization of the disease and its evolution, the patient’s classification, its follow-up and the treatment could be optimized. Thus, personalized medicine must combine innovative tools to measure, integrate and model data. Towards this goal, clinical metabolomics appears as ideally suited to obtain relevant information. Indeed, the metabolomics signature brings crucial insight to stratify patients according to their responses to a pathology and/or a treatment, to provide prognostic and diagnostic biomarkers, and to improve therapeutic outcomes. However, the translation of metabolomics from laboratory studies to clinical practice remains a subsequent challenge. Nuclear magnetic resonance spectroscopy (NMR) and mass spectrometry (MS) are the two key platforms for the measurement of the metabolome. NMR has several advantages and features that are essential in clinical metabolomics. Indeed, NMR spectroscopy is inherently very robust, reproducible, unbiased, quantitative, informative at the structural molecular level, requires little sample preparation and reduced data processing. NMR is also well adapted to the measurement of large cohorts, to multi-sites and to longitudinal studies. This review focus on the potential of NMR in the context of clinical metabolomics and personalized medicine. Starting with the current status of NMR-based metabolomics at the clinical level and highlighting its strengths, weaknesses and challenges, this article also explores how, far from the initial “opposition” or “competition”, NMR and MS have been integrated and have demonstrated a great complementarity, in terms of sample classification and biomarker identification. Finally, a perspective discussion provides insight into the current methodological developments that could significantly raise NMR as a more resolutive, sensitive and accessible tool for clinical applications and point-of-care diagnosis. Thanks to these advances, NMR has a strong potential to join the other analytical tools currently used in clinical settings.

The Genomes of Two Billfishes Provide Insights into the Evolution of Endothermy in Teleosts

Endothermy is a typical convergent phenomenon which has evolved independently at least eight times in vertebrates, and is of significant advantage to organisms in extending their niches. However, how vertebrates other than mammals or birds, especially teleosts, achieve endothermy has not previously been fully understood. In this study, we sequenced the genomes of two billfishes (swordfish and sailfish), members of a representative lineage of endothermic teleosts. Convergent amino acid replacements were observed in proteins related to heat production and the visual system in two endothermic teleost lineages, billfishes and tunas. The billfish-specific genetic innovations were found to be associated with heat exchange, thermoregulation, and the specialized morphology, including elongated bill, enlarged dorsal fin in sailfish and loss of the pelvic fin in swordfish.

The Role of PKM2 in Metabolic Reprogramming: Insights into the Regulatory Roles of Non-Coding RNAs

Pyruvate kinase is a key regulator in glycolysis through the conversion of phosphoenolpyruvate (PEP) into pyruvate. Pyruvate kinase exists in various isoforms that can exhibit diverse biological functions and outcomes. The pyruvate kinase isoenzyme type M2 (PKM2) controls cell progression and survival through the regulation of key signaling pathways. In cancer cells, the dimer form of PKM2 predominates and plays an integral role in cancer metabolism. This predominance of the inactive dimeric form promotes the accumulation of phosphometabolites, allowing cancer cells to engage in high levels of synthetic processing to enhance their proliferative capacity. PKM2 has been recognized for its role in regulating gene expression and transcription factors critical for health and disease. This role enables PKM2 to exert profound regulatory effects that promote cancer cell metabolism, proliferation, and migration. In addition to its role in cancer, PKM2 regulates aspects essential to cellular homeostasis in non-cancer tissues and, in some cases, promotes tissue-specific pathways in health and diseases. In pursuit of understanding the diverse tissue-specific roles of PKM2, investigations targeting tissues such as the kidney, liver, adipose, and pancreas have been conducted. Findings from these studies enhance our understanding of PKM2 functions in various diseases beyond cancer. Therefore, there is substantial interest in PKM2 modulation as a potential therapeutic target for the treatment of multiple conditions. Indeed, a vast plethora of research has focused on identifying therapeutic strategies for targeting PKM2. Recently, targeting PKM2 through its regulatory microRNAs, long non-coding RNAs (lncRNAs), and circular RNAs (circRNAs) has gathered increasing interest. Thus, the goal of this review is to highlight recent advancements in PKM2 research, with a focus on PKM2 regulatory microRNAs and lncRNAs and their subsequent physiological significance.

Type B lactic acidosis due to Warburg effect in a child presenting with T cell acute lymphoblastic leukaemia: a milder phenotype

Lactic acidosis (LA) is characterised by persistently increased blood lactate >5 mmol/L. Type A LA due to anaerobic glycolysis is frequently seen during management of haematological malignancies. A rare form of LA known as type B LA, which occurs as a result of metabolic dysregulation at cellular level has been described recently. This has been reported to be because of Warburg effect (WE) or aerobic glycolysis, which is seen in cancerous cells as they rely on aerobic glycolysis rather than oxidative phosphorylation for energy generation. Presence of type B LA at initial presentation of haematological malignancies is a poor prognosticating factor and has rarely been reported in children. We present a child with T cell acute lymphoblastic leukaemia with mild phenotype of type B LA due to WE. She responded dramatically to definitive chemotherapy and tolerated intensive phase of chemotherapy without any significant morbidity.

PKM2 promotes glucose metabolism through a let-7a-5p/Stat3/hnRNP-A1 regulatory feedback loop in breast cancer cells

Tumor cells metabolize more glucose to lactate in aerobic or hypoxic conditions than normal cells. Pyruvate kinase isoenzyme type M2 (PKM2) is crucial for tumor cell aerobic glycolysis. We established a role for let-7a-5p/Stat3/hnRNP-A1/PKM2 signaling in breast cancer cell glucose metabolism. PKM2 depletion via small interfering RNA (siRNA) inhibits cell proliferation and aerobic glycolysis in breast cancer cells. Signal transducer and activator of transcription 3 (Stat3) promotes upregulation of heterogeneous nuclear ribonucleoprotein (hnRNP)-A1 expression, hnRNP-A1 binding to pyruvate kinase isoenzyme (PKM) pre messenger RNA, and the subsequent formation of PKM2. This pathway is downregulated by the microRNA let-7a-5p, which functionally targets Stat3, whereas hnRNP-A1 blocks the biogenesis of let-7a-5p to counteract its ability to downregulate the Stat3/hnRNP-A1/PKM2 signaling pathway. The downregulation of Stat3/hnRNP-A1/PKM2 by let-7a-5p is verified using a breast cancer. These results suggest that let-7a-5p, Stat3, and hnRNP-A1 form a feedback loop, thereby regulating PKM2 expression to modulate glucose metabolism of breast cancer cells. These findings elucidate a new pathway mediating aerobic glycolysis in breast cancers and provide an attractive potential target for breast cancer therapeutic intervention.

Virtual high-throughput screens identifying hPK-M2 inhibitors: Exploration of model extrapolation

Glycolysis with PK-M2 occurs typically in anaerobic conditions and atypically in aerobic conditions, which is known as the Warburg effect. The Warburg effect is found in many oncogenic situations and is believed to provide energy and biomass for oncogenesis to persist. The work presented targets human PK-M2 (hPK-M2) in a virtual high-throughput screen to identify new inhibitors and leads for further study. In the initial screen, one of the 12 candidates selected for experimental validation showed biological activity (hit-rate = 8.13%). In the second screen with retrained models, six of 11 candidates selected for experimental validation showed biological activity (hit-rate: 54.5%). Additionally, four different scaffolds were identified for further analysis when examining the tested candidates and compounds in the training data. Finally, extrapolation was necessary to identify a sufficient number of candidates to test in the second screen. Examination of the results suggested stepwise extrapolation to maximize efficiency.

Targeting Strategies for Glucose Metabolic Pathways and T Cells in Colorectal Cancer

Colorectal cancer is a heterogeneous group of diseases that result from the accumulation of different sets of genomic alterations, together with epigenomic alterations, and it is influenced by tumor-host interactions, leading to tumor cell growth and glycolytic imbalances. This review summarizes recent findings that involve multiple signaling molecules and downstream genes in the dysregulated glycolytic pathway. This paper further discusses the role of the dysregulated glycolytic pathway in the tumor initiation, progression and the concomitant systemic immunosuppression commonly observed in colorectal cancer patients. Moreover, the relationship between colorectal cancer cells and T cells, especially CD8+ T cells, is discussed, while different aspects of metabolic pathway regulation in cancer cell proliferation are comprehensively defined. Furthermore, this study elaborates on metabolism in colorectal cancer, specifically key metabolic modulators together with regulators, glycolytic enzymes, and glucose deprivation induced by tumor cells and how they inhibit T-cell glycolysis and immunogenic functions. Moreover, metabolic pathways that are integral to T cell function, differentiation, and activation are described. Selective metabolic inhibitors or immunemodulation agents targeting these pathways may be clinically useful to increase effector T cell responses for colorectal cancer treatment. However, there is a need to identify specific antigens using a cancer patient-personalized approach and combination strategies with other therapeutic agents to effectively target tumor metabolic pathways.

Acute Lymphoblastic Leukemia Presenting with Liver Infiltration and Severe Lactic Acidosis

BACKGROUND Type-B lactic acidosis is a rare complication of solid tumors and hematological malignancies. It occurs secondary to Warburg effect, when glucose metabolism in cancer cells switches from the oxidative pathway to the glycolytic pathway. Malignant lactic acidosis is a life-threatening condition if not promptly diagnosed and treated urgently. CASE REPORT We report the case of a 58-year-old male patient who presented with severe chest pain, dyspnea, systemic symptoms, leukopenia, normocytic anemia, and severe lactic acidosis. He was admitted with a possible diagnosis of acute pericarditis and lactic acidosis. Sodium bicarbonate replacement did not improve the lactic acidosis. Liver biopsy was performed because of persistently elevated alkaline phosphatase and gamma-glutamyl transferase; the biopsy showed atypical lymphoblasts and bone marrow biopsy confirmed the diagnosis of precursor B acute lymphoblastic leukemia. Lactic acidosis normalized after initiation of chemotherapy. CONCLUSIONS Cancer, particularly hematological malignancy, should be considered as an etiology and differential diagnosis of type-B lactic acidosis. Prompt recognition and urgent initiation of specific therapy to control the underlying malignancy are critical to manage this serious metabolic complication.

Pyruvate kinase activators as a therapy target: a patent review 2011-2017

INTRODUCTION

It is well known that cancer cells have an altered metabolism both to meet the energy needs and to provide initial molecules for the synthesis of macromolecules. To cope with the new metabolic state, different forms of certain enzymes are expressed in extreme amounts. These enzymes are seen as very attractive targets to deal with cancer. Pyruvate kinases isoenzyme M2 (PKM2) is a key enzyme that determines whether glucose is used for energy or synthesis of biosynthetic molecules. The dimeric form of PKM2 main form in several cancer cells serves the formation of synthetic precursors required for the cell growth and proliferation from glycolytic intermediates.

AREAS COVERED

This article reviews appropriate publications on PKM2 activators from the points of view of synthesis and biological activities between 2011-2017. Herein, based on the chemical structure, PKM2 activators are classified into sulfonamide, phenolic, carboxamide and pyridopyrimidinone derivatives.

EXPERT OPINION

PKM2 activation inhibits cell growth and proliferation by decreasing a number of biomolecules required for cell building. Therefore; PKM2 activators are considered as an ideal drug for or the treatment of many cancer pathogens. It is necessary to discover new, more active and selective compounds for PKM2 activation.

Long intergenic non-coding RNA GALMD3 in chicken Marek's disease

Long intergenic non-coding RNAs (lincRNAs) are transcribed from non-coding DNA sequences. Studies have revealed that aberrant expressions of lincRNAs are associated with various types of cancers and neurological disorders. Marek's disease (MD) is a highly contagious T-cell lymphoid neoplasia of chicken induced by Marek's disease virus (MDV). In this study, we first identified and validated linc-GALMD3 highly expressed in MDV-infected CD4+ T cells by RNA-Seq and qRT-PCR. By RNA-Seq analysis in MDCC-MSB1 cells after loss of function of linc-GALMD3 by shRNA, we found that linc-GALMD3 could positively cis-regulate its downstream gga-miR-223 gene expression. In contrast, it could trans-regulate the 748 differentially expressed genes (FDR < 0.01) that were mainly enriched into mitochondrial structure and cell cycle processes using GO analysis. Of these, the most significantly expressed gene EPYC might cause iris lesion in MD. The other eight genes, NDUFA4, NDUFB6, NDUFV1, NDUFS8, SDHB, UQCRC1, UQCRC2, and COX7A2, actively participated in oxidative phosphorylation in mitochondrial dysfunction and cell death. Most importantly, we found that the MDV replication was repressed when linc-GALMD3 was knocked down in CEF cells. Our results suggested that linc-GALMD3 might be a critical regulator in chicken MD and could be used as a candidate-promising mark for MD prevention, diagnosis, and treatment.

Hemodialysis for Lactic Acidosis

Lactic acidosis (Type A) is common in critically ill patients and usually treated by correcting the underlying etiology. We present the case of a young female who presented with life-threatening lactic acidosis secondary to hematological malignancy. Timely initiation of hemodialysis was lifesaving. The case highlights the importance of considering Type B lactic acidosis (in this case secondary to a hematological malignancy) and also initiating renal replacement therapy when routine measures are ineffective.

Biosynthesis and Biological Activity of Carbasugars

The first synthesis of carbasugars, compounds in which the ring oxygen of a monosaccharide had been replaced by a methylene moiety, was described in 1966 by Professor G. E. McCasland’s group. Seven years later, the first true natural carbasugar (5a-carba-R-D-galactopyranose) was isolated from a fermentation broth of Streptomyces sp. MA-4145. In the following decades, the chemistry and biology of carbasugars have been extensively studied. Most of these compounds show interesting biological properties, especially enzymatic inhibitory activities, and, in consequence, an important number of analogues have also been prepared in the search for improved biological activities. The aim of this review is to give coverage on the progress made in two important aspects of these compounds: the elucidation of their biosynthesis and the consideration of their biological properties, including the extensively studied carbapyranoses as well as the much less studied carbafuranoses.

The proliferation impairment induced by AQP3 deficiency is the result of glycerol uptake and metabolism inhibition in gastric cancer cells

Gastric cancer is a big threat to human health. Effective therapeutic cancer target remains to be discovered. Aquaporin 3 (AQP3) belongs to a family of transmembrane channels that are important in transporting water, glycerol, and other small molecules across the cell membrane. Glycerol that is transported by AQP3 is necessary for cell energy generation and lipid synthesis which fulfill the cell biological processes. Previous studies have shown that AQP3 is implicated in disease progression in several cancer types. However, whether AQP3-regulated glycerol uptake and metabolism were involved in cancer progression remains to be further studied. Our study demonstrated that the expression of AQP3 was positively correlated with glycerol level in human gastric cancer tissues. AQP3 inhibition induced proliferation impairment in gastric cancer cells both in vitro and in vivo. AQP3 inhibition that induced glycerol uptake reduction and glycerol administration would rehabilitate the cell proliferation. The energy and lipid production decreased when AQP3 was knocked down since the cellular glycerol level and several lipogenesis enzymes were downregulated. PI3K/Akt signaling pathway, which was involved in the impaired lipid and ATP production, was also inhibited after AQP3 knockdown. Our study indicated that the energy and lipid production inhibition, which were responsible for gastric cancer cell proliferation impairment, were induced by glycerol uptake reduction after AQP3 knockdown.

Factor inhibiting HIF1α (FIH-1) functions as a tumor suppressor in human colorectal cancer by repressing HIF1α pathway

Colorectal cancer (CRC) is one of the most common cancers worldwide. The molecular mechanisms underlying CRC development involve a multistep process with the accumulation of both genetic and epigenetic changes. To deeply understand CRC tumorigenesis and progression, advances in identification of novel mechanisms and key factors are therefore in an urgent need. Here, we examined the correlation of factor inhibiting HIF-1α (FIH-1) expression with clinicopathological features of CRC. The finding that FIH-1 was not only significantly decreased in tumor tissue but also was significantly correlated with tumor invading depth, lymph node involvement, and metastasis suggested the role of FIH-1 as a tumor suppressor in CRC development. To further support the above hypothesis, we performed both in vitro and in vivo experiments to identify the role of FIH-1 in CRC development. FIH-1 was found to inhibit CRC cell proliferation, migration, invasion, and colony formation in vitro. FIH-1 was also shown to repress LOVO xenograft tumor growth in vivo. To decipher the mechanism, we examined the expression level of HIF-1α and its target genes. We found that FIH-1 was able to inhibit HIF1α mediated transcription of GLUT1 and VEGF in CRC cells. The above observation points to the possibility that loss or decreased expression of FIH-1 gene may lead to a constitutive activation of HIF1α and an alteration of HIF-1 targets such as GLUT-1 and VEGF. These findings highlight the critical role of FIH-1 in CRC and indicate FIH-1 functions as a tumor suppressor in human CRC by repressing HIF1α pathway.

ERK2-Pyruvate Kinase Axis Permits Phorbol 12-Myristate 13-Acetate-induced Megakaryocyte Differentiation in K562 Cells

Metabolic changes that contribute to differentiation are not well understood. Overwhelming evidence shows the critical role of glycolytic enzyme pyruvate kinase (PK) in directing metabolism of proliferating cells. However, its role in metabolism of differentiating cells is unclear. Here we studied the role of PK in phorbol 12-myristate 13-acetate (PMA)-induced megakaryocytic differentiation in human leukemia K562 cells. We observed that PMA treatment decreased cancer-type anabolic metabolism but increased ATP production, along with up-regulated expression of two PK isoforms (PKM2 and PKR) in an ERK2-dependent manner. Interestingly, silencing of PK (PKM2 and PKR) inhibited PMA-induced megakaryocytic differentiation, as revealed by decreased expression of megakaryocytic differentiation marker CD61 and cell cycle behavior. Further, PMA-induced ATP production reduced greatly upon PK silencing, suggesting that PK is required for ATP synthesis. In addition to metabolic effects, PMA treatment also translocated PKM2, but not PKR, into nucleus. ERK1/2 knockdowns independently and together suggested the role of ERK2 in the up-regulation of both the isoforms of PK, proposing a role of ERK2-PK isoform axis in differentiation. Collectively, our findings unravel ERK2 guided PK-dependent metabolic changes during PMA induction, which are important in megakaryocytic differentiation.

PKM2 promotes glucose metabolism and cell growth in gliomas through a mechanism involving a let-7a/c-Myc/hnRNPA1 feedback loop

Tumor cells metabolize more glucose to lactate in aerobic or hypoxic conditions than non-tumor cells. Pyruvate kinase isoenzyme type M2 (PKM2) is crucial for tumor cell aerobic glycolysis. We established a role for let-7a/c-Myc/hnRNPA1/PKM2 signaling in glioma cell glucose metabolism. PKM2 depletion via siRNA inhibits cell proliferation and aerobic glycolysis in glioma cells. C-Myc promotes up-regulation of hnRNPA1 expression, hnRNPA1 binding to PKM pre-mRNA, and the subsequent formation of PKM2. This pathway is downregulated by the microRNA let-7a, which functionally targets c-Myc, whereas hnRNPA1 blocks the biogenesis of let-7a to counteract its ability to downregulate the c-Myc/hnRNPA1/PKM2 signaling pathway. The down-regulation of c-Myc/ hnRNPA1/PKM2 by let-7a is verified using a glioma xenograft model. These results suggest that let-7a, c-Myc and hnRNPA1 from a feedback loop, thereby regulating PKM2 expression to modulate glucose metabolism of glioma cells. These findings elucidate a new pathway mediating aerobic glycolysis in gliomas and provide an attractive potential target for therapeutic intervention.

2-Deoxy-2-fluoro-d-glucose metabolism in Arabidopsis thaliana

2-Deoxy-2-fluoro-d-glucose (FDG) is glucose analog routinely used in clinical and animal radiotracer studies to trace glucose uptake but it has rarely been used in plants. Previous studies analyzed FDG translocation and distribution pattern in plants and proposed that FDG could be used as a tracer for photoassimilates in plants. Elucidating FDG metabolism in plants is a crucial aspect for establishing its application as a radiotracer in plant imaging. Here, we describe the metabolic fate of FDG in the model plant species Arabidopsis thaliana. We fed FDG to leaf tissue and analyzed leaf extracts using MS and NMR. On the basis of exact mono-isotopic masses, MS/MS fragmentation, and NMR data, we identified 2-deoxy-2-fluoro-gluconic acid, FDG-6-phosphate, 2-deoxy-2-fluoro-maltose, and uridine-diphosphate-FDG as four major end products of FDG metabolism. Glycolysis and starch degradation seemed to be the important pathways for FDG metabolism. We showed that FDG metabolism in plants is considerably different than animal cells and goes beyond FDG-phosphate as previously presumed.

Glycolysis is governed by growth regime and simple enzyme regulation in adherent MDCK cells

Due to its vital importance in the supply of cellular pathways with energy and precursors, glycolysis has been studied for several decades regarding its capacity and regulation. For a systems-level understanding of the Madin-Darby canine kidney (MDCK) cell metabolism, we couple a segregated cell growth model published earlier with a structured model of glycolysis, which is based on relatively simple kinetics for enzymatic reactions of glycolysis, to explain the pathway dynamics under various cultivation conditions. The structured model takes into account in vitro enzyme activities, and links glycolysis with pentose phosphate pathway and glycogenesis. Using a single parameterization, metabolite pool dynamics during cell cultivation, glucose limitation and glucose pulse experiments can be consistently reproduced by considering the cultivation history of the cells. Growth phase-dependent glucose uptake together with cell-specific volume changes generate high intracellular metabolite pools and flux rates to satisfy the cellular demand during growth. Under glucose limitation, the coordinated control of glycolytic enzymes re-adjusts the glycolytic flux to prevent the depletion of glycolytic intermediates. Finally, the model's predictive power supports the design of more efficient bioprocesses.

Glycolysis generates biomass precursors and energy from sugars and is therefore a key element in the metabolism of mammalian cells. Changes in its activity greatly affect cellular function which is often recognized as metabolic disease but also as opportunity for the design of efficient bioprocesses. Metabolic research discovered that continuously growing mammalian cells often exhibit a high glycolytic activity but also delivered seemingly endless facets in the pathway operation. The latter call for a systems-level understanding regarding capacity and regulation for a broad range of cultivation conditions. In this work, we couple a cell growth model to a simple kinetic description of glycolysis to consistently explain intracellular metabolite pool dynamics of the Madin-Darby canine kidney cell line over a variety of experiments and time scales while considering the growth status and cultivation history of the cells. We argue that the many different dynamics in glycolysis result from an interplay between a growth-dependent sugar uptake together with simple intrinsic enzyme regulation.

High-throughput sequencing in mitochondrial DNA research

Next-generation sequencing, also known as high-throughput sequencing, has greatly enhanced researchers' ability to conduct biomedical research on all levels. Mitochondrial research has also benefitted greatly from high-throughput sequencing; sequencing technology now allows for screening of all 16,569 base pairs of the mitochondrial genome simultaneously for SNPs and low level heteroplasmy and, in some cases, the estimation of mitochondrial DNA copy number. It is important to realize the full potential of high-throughput sequencing for the advancement of mitochondrial research. To this end, we review how high-throughput sequencing has impacted mitochondrial research in the categories of SNPs, low level heteroplasmy, copy number, and structural variants. We also discuss the different types of mitochondrial DNA sequencing and their pros and cons. Based on previous studies conducted by various groups, we provide strategies for processing mitochondrial DNA sequencing data, including assembly, variant calling, and quality control.

PKM2 inhibitor shikonin suppresses TPA-induced mitochondrial malfunction and proliferation of skin epidermal JB6 cells

Chemoprevention has been a pivotal and effective strategy during the skin cancer treatment. Using human skin normal and tumor samples, we demonstrated that both the expression and activity levels of pyruvate kinase M2 (PKM2) were higher in skin tumor tissues than normal tissues, suggesting that PKM2, one of important metabolic enzyme, might serve as a target for skin cancer prevention and/or therapy. Shikonin, a small-molecule active chemical, has been studied as an anti-cancer drug candidate in human cancer models. However, the mechanism of action and the chemopreventive potential of shikonin are unclear. Herein, we used the skin epidermal JB6 P+ cells and demonstrated that shikonin suppressed the tumor promoter 12-O-tetradecanoylphorbol 13-acetate (TPA) induced neoplastic cell transformation and PKM2 activation in the early stage of carcinogenesis. Mitochondrial functions were inhibited by TPA treatment, as indicated by reduced mitochondrial membrane potential and mitochondrial respiration, which were restored by shikonin. We also examined the levels of lactate as a glycolysis marker, and shikonin suppressed its increase caused by tumor promoter treatment. Modulation of cell metabolism by shikonin was associated with G2-M phase accumulation, and Fra-1 (a major subunit of activator protein 1 in skin tumorigenesis) downregulation. In addition, we demonstrated that AMP-activated protein kinase (AMPK), an energy sensor, which is inactivated by TPA, shikonin could reverse AMPK activity. These results suggest that shikonin bears chemopreventive potential for human skin cancers in which PKM2 is upregulated, which might be mediated by inhibiting oncogenic activation, PKM2 activation, and mitochondrial dysfunction.

Linking vitamin B1 with cancer cell metabolism

The resurgence of interest in cancer metabolism has linked alterations in the regulation and exploitation of metabolic pathways with an anabolic phenotype that increases biomass production for the replication of new daughter cells. To support the increase in the metabolic rate of cancer cells, a coordinated increase in the supply of nutrients, such as glucose and micronutrients functioning as enzyme cofactors is required. The majority of co-enzymes are water-soluble vitamins such as niacin, folic acid, pantothenic acid, pyridoxine, biotin, riboflavin and thiamine (Vitamin B1). Continuous dietary intake of these micronutrients is essential for maintaining normal health. How cancer cells adaptively regulate cellular homeostasis of cofactors and how they can regulate expression and function of metabolic enzymes in cancer is underappreciated. Exploitation of cofactor-dependent metabolic pathways with the advent of anti-folates highlights the potential vulnerabilities and importance of vitamins in cancer biology. Vitamin supplementation products are easily accessible and patients often perceive them as safe and beneficial without full knowledge of their effects. Thus, understanding the significance of enzyme cofactors in cancer cell metabolism will provide for important dietary strategies and new molecular targets to reduce disease progression. Recent studies have demonstrated the significance of thiamine-dependent enzymes in cancer cell metabolism. Therefore, this review discusses the current knowledge in the alterations in thiamine availability, homeostasis, and exploitation of thiamine-dependent pathways by cancer cells.

Exploiting metabolic differences in glioma therapy

Brain function depends upon complex metabolic interactions amongst only a few different cell types, with astrocytes providing critical support for neurons. Astrocyte functions include buffering the extracellular space, providing substrates to neurons, interchanging glutamate and glutamine for synaptic transmission with neurons, and facilitating access to blood vessels. Whereas neurons possess highly oxidative metabolism and easily succumb to ischemia, astrocytes rely more on glycolysis and metabolism associated with synthesis of critical intermediates, hence are less susceptible to lack of oxygen. Astrocytoma and higher grade glioma cells demonstrate both basic metabolic mechanisms of astrocytes as well as tumors in general, e.g. they show a high glycolytic rate, lactate extrusion, ability to proliferate even under hypoxia, and opportunistic use of mechanisms to enhance metabolism and blood vessel generation, and suppression of cell death pathways. There may be differences in metabolism between neurons, normal astrocytes and astrocytoma cells, providing therapeutic opportunities against astrocytomas, including a wide range of enzyme and transporter differences, regulation of hypoxia-inducible factor (HIF), glutamate uptake transporters and glutamine utilization, differential sensitivities of monocarboxylate transporters, presence of glycogen, high interlinking with gap junctions, use of NADPH for lipid synthesis, utilizing differential regulation of synthetic enzymes (e.g. isocitrate dehydrogenase, pyruvate carboxylase, pyruvate dehydrogenase, lactate dehydrogenase, malate-aspartate NADH shuttle) and different glucose uptake mechanisms. These unique metabolic susceptibilities may augment conventional therapeutic attacks based on cell division differences and surface receptors alone, and are starting to be implemented in clinical trials.

The insulin-like growth factor-system in a patient with diffuse large B-cell non-Hodgkin's lymphoma and lactic acidosis

Lactic acidosis is a rare complication of haematological malignancies with a poor prognostic outcome and unclear aetiology. Possible mechanisms include high rate of glycolysis by cancer cells, in part due to overexpression of hexokinase II. The insulin-like growth factor (IGF)-system has an important role in normal as well as tumour cell growth. We present a case of a 79-year-old man with a diffuse large B-cell lymphoma and lactic acidosis. Initially, the patient was successfully treated according to the R-CHOP scheme. After recurrence of disease, the patient was treated according to a protocol of the Dutch-Belgian Haemato-Oncology Group (HOVON-85 study). Eleven months after completion of the last therapy, the patient still appeared to be in complete remission. Serum levels of IGFs, pro-IGF-IIE[68-88], IGF binding proteins (IGFBPs)-1 to - 4 , acid labile subunit (ALS), as well as ternary IGF-I-IGFBP-3-ALS complex formation, were determined in samples taken before, during and after treatment, respectively. Before treatment patient's serum concentration of the growth hormone-dependent parameters of the IGF-system and IGF-II were clearly reduced when compared with patient's values during remission of disease. On the other hand, during acidosis a relatively higher proportion of IGFs is present in binary complexes, instead of 150 kDa complexes, that may allow an increased access of IGFs to target cells including the malignant ones. Pretreatment serum levels of IGFBP-1 and -2 were elevated, decreased during therapy and normalized at remission. Especially IGFBP-2 seems a suitable marker for disease activity.

Rocking cell metabolism: revised functions of the key glycolytic regulator PKM2 in cancer

Cancer cell metabolism is exemplified by high glucose consumption and lactate production. Pyruvate kinase (PK), which catalyzes the final step of glycolysis, has emerged as a potential regulator of this metabolic phenotype. The M2 isoform of PK (PKM2) is highly expressed in cancer cells. However, the mechanisms by which PKM2 coordinates high energy requirements with high anabolic activities to support cancer cell proliferation are still not completely understood. Current research has elucidated novel regulatory mechanisms for PKM2, contributing to its important role in cancer. This review summarizes the current understanding and explores future directions in the field, highlighting controversies regarding the activity and specificity of PKM2 in cancer. In light of this knowledge, the potential therapeutic implications and strategies are critically discussed.

Energy metabolism in cancer cells: how to explain the Warburg and Crabtree effects?

Cancer cells have a greater need for energy and a ready supply of the building blocks necessary for the synthesis of macromolecules (nucleotides, protein, lipids) in order to duplicate genome and biomass. The hypothesis can be postulated that those precursors for synthetic processes, which can only be furnished by glycolysis, cannot be sufficiently recruited from external sources (the blood stream) and that glycolysis is necessarily markedly activated. It can also be hypothesized that the Krebs cycle, which also furnishes precursors for macromolecule synthesis to meet the requirements of proliferating cells, is depleted of intermediates. In view of its cyclic nature requiring not only pyruvate but also oxalacetate as the "last" metabolite of the reaction sequence for its sustenance, the Krebs cycle may be partially inactivated. While anaplerotic reactions and other sources (amino acids and fatty acids) could supply the cycle with intermediates, those pathways constitute futile cycles for amino and fatty acids as they would be partially degraded in the cycle and the intermediates thus obtained would be exported into the cytoplasm for synthetic processes with no advantage for the cell. It is also hypothesized that glutamine, an important fuel for cancer cells and playing a critical role in anaplerosis, may not contribute to reinforce the cycle; malate and α-ketoglutarate, two products of glutamine metabolism, might be exported from the mitochondria as precursors of biosynthetic pathways. It is possible then that malate, used for NADPH production required in the biosynthetic pathways, and glycerol-phosphate, too used for biosynthetic purposes (lipid biosynthesis), are unable to sustain the mitochondrial redox shuttles reducing the respiratory capacity of the mitochondria. Low shuttle capacity implies that NADH generated by glycolysis needs to be continuously re-oxidized in the cytoplasm via lactate dehydrogenase to maintain glycolysis fully activated, causing the abnormal lactate production observed in cancer. The paper goes onto discuss the essential role of glucose in cancer cell proliferation also in inducing the Crabtree effect. It is finally hypothesized that respiration inhibition after cancer cells have been supplied with glucose is due to reactivation in a suited medium of biosynthetic pathways with the consequences described above.

Levels and patterns of expression of hypoxia-inducible factor-1α, vascular endothelial growth factor, glucose transporter-1 and CD105 in adenoid cystic carcinomas with high-grade transformation

AIMS

To compare the expression of proteins regulated by hypoxia between adenoid cystic carcinoma (ACC) with and without high-grade transformation (HGT).

METHODS AND RESULTS

  In eight ACC-HGT and 18 ACC without HGT, expression of hypoxia-inducible factor-1 (HIF-1α), vascular endothelial growth factor (VEGF), glucose transporter-1 (GLUT-1) and microvascular density (MVD) by CD105 (a hypoxia-inducible protein expressed in angiogenic endothelial cells) was determined. Expression levels of HIF-1α and VEGF as well as CD105-MVD did not differ significantly between: (i) transformed and conventional areas (TA and CA, respectively) of ACC-HGT, (ii) CA and ordinary ACC. HIF-1α was detected in 100% of cases and presented a diffuse expression pattern. No significant association was found between levels of HIF-1α expression and tumour size, metastasis and recurrence. GLUT-1 showed a prostromal expression pattern and was observed exclusively in TA (three of six cases) and in only three of 14 ACC.

CONCLUSIONS

Both the absence of significant alterations in levels of expression of HIF-1α, VEGF and CD105 and the patterns of expression of HIF-1α and GLUT-1 suggest that hypoxia may not play a key role in the process of high-grade transformation of ACC. Although HIF-1α expression is a common finding in ACC, it cannot be used as a marker of tumour aggressiveness.

MUC1-C oncoprotein regulates glycolysis and pyruvate kinase M2 activity in cancer cells

Aerobic glycolysis in cancer cells is regulated by multiple effectors that include Akt and pyruvate kinase M2 (PKM2). Mucin 1 (MUC1) is a heterodimeric glycoprotein that is aberrantly overexpressed by human breast and other carcinomas. Here we show that transformation of rat fibroblasts by the oncogenic MUC1-C subunit is associated with Akt-mediated increases in glucose uptake and lactate production, consistent with the stimulation of glycolysis. The results also demonstrate that the MUC1-C cytoplasmic domain binds directly to PKM2 at the B- and C-domains. Interaction between the MUC1-C cytoplasmic domain Cys-3 and the PKM2 C-domain Cys-474 was found to stimulate PKM2 activity. Conversely, epidermal growth factor receptor (EGFR)-mediated phosphorylation of the MUC1-C cytoplasmic domain on Tyr-46 conferred binding to PKM2 Lys-433 and inhibited PKM2 activity. In human breast cancer cells, silencing MUC1-C was associated with decreases in glucose uptake and lactate production, confirming involvement of MUC1-C in the regulation of glycolysis. In addition, EGFR-mediated phosphorylation of MUC1-C in breast cancer cells was associated with decreases in PKM2 activity. These findings indicate that the MUC1-C subunit regulates glycolysis and that this response is conferred in part by PKM2. Thus, the overexpression of MUC1-C oncoprotein in diverse human carcinomas could be of importance to the Warburg effect of aerobic glycolysis.

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

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

Enhancing mitochondrial respiration suppresses tumor promoter TPA-induced PKM2 expression and cell transformation in skin epidermal JB6 cells

Differentiated cells primarily metabolize glucose for energy via the tricarboxylic acid cycle and oxidative phosphorylation, but cancer cells thrive on a different mechanism to produce energy, characterized as the Warburg effect, which describes the increased dependence on aerobic glycolysis. The M2 isoform of pyruvate kinase (PKM2), which is responsible for catalyzing the final step of aerobic glycolysis, is highly expressed in cancer cells and may contribute to the Warburg effect. However, whether PKM2 plays a contributing role during early cancer development is unclear. In our studies, we have made an attempt to elucidate the effects of varying mitochondrial respiration substrates on skin cell transformation and expression of PKM2. Tumorigenicity in murine skin epidermal JB6 P+ (promotable) cells was measured in a soft agar assay using 12-O-tetradecanoylphorbol-13-acetate (TPA) as a tumor promoter. We observed a significant reduction in cell transformation upon pretreatment with the mitochondrial respiration substrate succinate or malate/pyruvate. We observed that increased expression and activity of PKM2 in TPA-treated JB6 P+ cells and pretreatment with succinate or malate/pyruvate suppressed the effects. In addition, TPA treatment also induced PKM2 whereas PKM1 expression was suppressed in mouse skin epidermal tissues in vivo. In comparison with JB6 P+ cells, the nonpromotable JB6 P- cells showed no increase in PKM2 expression or activity upon TPA treatment. Knockdown of PKM2 using a siRNA approach significantly reduced skin cell transformation. Thus, our results suggest that PKM2 activation could be an early event and play a contributing role in skin tumorigenesis.

Human pyruvate kinase M2: a multifunctional protein

Glycolysis, a central metabolic pathway, harbors evolutionary conserved enzymes that modulate and potentially shift the cellular metabolism on requirement. Pyruvate kinase, which catalyzes the last but rate-limiting step of glycolysis, is expressed in four isozymic forms, depending on the tissue requirement. M2 isoform (PKM2) is exclusively expressed in embryonic and adult dividing/tumor cells. This tetrameric allosterically regulated isoform is intrinsically designed to downregulate its activity by subunit dissociation (into dimer), which results in partial inhibition of glycolysis at the last step. This accumulates all upstream glycolytic intermediates as an anabolic feed for synthesis of lipids and nucleic acids, whereas reassociation of PKM2 into active tetramer replenishes the normal catabolism as a feedback after cell division. In addition, involvement of this enzyme in a variety of pathways, protein-protein interactions, and nuclear transport suggests its potential to perform multiple nonglycolytic functions with diverse implications, although multidimensional role of this protein is as yet not fully explored. This review aims to provide an overview of the involvement of PKM2 in various physiological pathways with possible functional implications.

Targeting glycolysis: a fragment based approach towards bifunctional inhibitors of hLDH-5

hLDH-5 has emerged as a promising target for anti-glycolytic cancer chemotherapy. Here we report a first generation of bifunctional inhibitors, which show promising activity against hLDH-5.

Hepatitis B virus surface antigen interacts with acid alpha-glucosidase and alters glycogen metabolism

AIM

Hepatitis B virus (HBV) infection is highly correlated with hepatocellular carcinoma. Previous studies have reported that expression of hepatitis B virus pre-S2 mutant surface antigen is related to hepatoma development. An aberrant carbohydrate metabolism is a hallmark of malignant transformation.

METHODS

We performed yeast two-hybrid screening with HBV pre-S2-del large surface protein (pre-S2Delta) by using human liver cDNA library, and identified the acid alpha-glucosidase (acid alpha-glucosidase) as the novel cellular interacting protein of pre-S2Delta. The association of pre-S2Delta with the acid alpha-glucosidase was confirmed by confocal immunofluorescence and co-immunoprecipitation assay. Further, the acid alpha-glucosidase activity and glycogen content were analyzed in ML-1 cells expressing pre-S2Delta.

RESULTS

The interaction between HBV large surface protein and acid alpha-glucosidase was demonstrated with co-immunoprecipitation in vitro and in vivo, and the binding was mediated through c-terminal region 889-952 amino acid of acid alpha-glucosidase. On the other hand, HBV large surface protein interacted with acid alpha-glucosidase through N-terminal region 1-157 amino acid of HBV large surface protein. Expression of HBV large surface protein enhanced acid alpha-glucosidase activity and resulted in decrease of cellular glycogen.

CONCLUSION

Our result demonstrates that HBV large surface protein interacts with acid alpha-glucosidase which plays an important role in glycogen balance. Together, these data suggest a novel pathway by which HBV large surface protein affects carbohydrate metabolism.

Amplex UltraRed enhances the sensitivity of fluorimetric pyruvate detection

Pyruvate, which is produced in the final step of glycolysis, participates in anabolic metabolism, catabolic metabolism, and signal transduction. We have recently reported a new sensitive and selective fluorimetric assay for pyruvate measurement using Amplex Red as a fluorogenic dye. However, the fluorescence of the reaction product, resorufin, is pH dependent, which limits the sensitivity of the assay at pH 6.7. In this Note, we evaluate Invitrogen's new dye, Amplex UltraRed, as a fluorogenic agent for pyruvate determination. Our results show that Amplex UltraRed improves the performance of the assay, providing brighter fluorescence and enhanced sensitivity.

Dominant negative mutations affect oligomerization of human pyruvate kinase M2 isozyme and promote cellular growth and polyploidy

This study was designed to understand the mechanism and functional implication of the two heterozygous mutations (H391Y and K422R) of human pyruvate kinase M2 isozyme (PKM(2)) observed earlier in a Bloom syndrome background. The co-expression of homotetrameric wild type and mutant PKM(2) in the cellular milieu resulting in the interaction between the two at the monomer level was substantiated further by in vitro experiments. The cross-monomer interaction significantly altered the oligomeric state of PKM(2) by favoring dimerization and heterotetramerization. In silico study provided an added support in showing that hetero-oligomerization was energetically favorable. The hetero-oligomeric populations of PKM(2) showed altered activity and affinity, and their expression resulted in an increased growth rate of Escherichia coli as well as mammalian cells, along with an increased rate of polyploidy. These features are known to be essential to tumor progression. This study provides insight in understanding the modulated role of large oligomeric multifunctional proteins such as PKM(2) by affecting cellular behavior, which is an essential observation to understand tumor sustenance and progression and to design therapeutic intervention in future.

Serum metabolome analysis by 1H-NMR reveals differences between chronic lymphocytic leukaemia molecular subgroups

Chronic lymphocytic leukaemia (CLL) is a heterogeneous disease exhibiting variable clinical course and survival rates. Mutational status of the immunoglobulin heavy chain variable regions (IGHVs) of CLL cells offers useful prognostic information for high-risk patients, but time and economical costs originally prevented it from being routinely used in a clinical setting. Instead, alternative markers of IGHV status, such as zeta-associated protein (ZAP70) or messenger RNA levels are often used. We report a (1)H-NMR-based metabolomics approach to examine serum metabolic profiles of early stage, untreated CLL patients (Binet stage A) classified on the basis of IGHV mutational status or ZAP70. Metabolic profiles of CLL patients (n=29) exhibited higher concentrations of pyruvate and glutamate and decreased concentrations of isoleucine compared with controls (n=9). Differences in metabolic profiles between unmutated (UM-IGHV; n=10) and mutated IGHV (M-IGHV; n=19) patients were determined using partial least square discriminatory analysis (PLS-DA; R(2)=0.74, Q(2)=0.36). The UM-IGHV patients had elevated levels of cholesterol, lactate, uridine and fumarate, and decreased levels of pyridoxine, glycerol, 3-hydroxybutyrate and methionine concentrations. The PLS-DA models derived from ZAP70 classifications showed comparatively poor goodness-of-fit values, suggesting that IGHV mutational status correlates better with disease-related metabolic profiles. Our results highlight the usefulness of (1)H-NMR-based metabolomics as a potential non-invasive prognostic tool for identifying CLL disease-state biomarkers.

Severe lactic acidosis in a patient with B-cell lymphoma: a case report and review of the literature

Lactic acidosis is commonly observed in clinical situations such as shock and sepsis, as a result of tissue hypoperfusion and hypoxia. Lymphoma and leukemia are among other clinical situations where lactic acidosis has been reported. We present a case of a 59-year-old female with lactic acidosis who was found to have aggressive B-cell lymphoma. There have been 29 cases of lymphoma induced lactic acidosis reported thus far; however all reported cases have abnormal vital signs or concomitant medical conditions that may lead to lactic acidosis. The pathogenesis of malignancy-induced lactic acidosis is not well understood; however associated factors include increased glycolysis, increased lactate production by cancer cells, and decreased hepatic clearance of lactate. When it occurs, lactic acidosis is a poor prognostic sign in these patients. Prompt diagnosis and treatment of underlying lymphoma or leukemia remains the only way to achieve complete resolution of lactic acidosis in these patients.

Complete absence of M2-pyruvate kinase expression in benign pancreatic ductal epithelium and pancreaticobiliary and duodenal neoplasia

Background

Elevated serum concentrations of M2-pyruvate kinase (M2-PK) correlate with poor prognosis in patients with pancreaticobiliary and duodenal cancer, but the expression of M2-PK in formalin-fixed pancreatic tissue is unknown. We aimed to characterise the immunohistochemical expression of M2-PK in archived specimens of pancreaticobiliary and duodenal cancers, premalignant lesions, chronic pancreatitis, and normal pancreas.

Methods

Immunohistochemical staining was performed with mouse anti-M2-PK monoclonal antibody (clone DF-4) at an optimal dilution of 1:25 on tissue microarrays constructed from formalin-fixed paraffin-embedded pancreatic tissue of 126 consecutive patients undergoing pancreatic resections between June 2001 and June 2006. 104 underwent resection for cancer and 22 for chronic pancreatitis. 78 specimens of chronic pancreatitis tissue were obtained adjacent to areas of cancer. Normal pancreatic tissue was obtained from the resection specimens in a total of 30 patients. Metastatic tumours in 61 regional lymph nodes from 61 patients were also studied. A further 11 premalignant pancreaticobiliary and duodenal lesions were studied. M2-PK expression was quantified with the immunohistochemical score (IHS; Range 0-12).

Results

Benign non-ductal tissue in chronic pancreatitis and normal pancreas showed variable expression of M2-PK (IHS = 1 in 25%, IHS = 2-3 in 40%, IHS>3 in 40%). Benign pancreatic ductal epithelium, all primary pancreaticobiliary and duodenal premalignant lesions and cancers (and lymph node metastasis) showed complete lack of expression (IHS = 0).

Conclusion

Complete lack of M2-PK expression was observed in benign pancreatic ducts, premalignant lesions and cancer. M2-PK is present only in benign non-ductal epithelium in normal pancreas and peri-tumoural tissue.

Faecal M2-pyruvate kinase: a novel, noninvasive marker of ileal pouch inflammation

BACKGROUND

Dimeric M2-pyruvate kinase (dM2-PK) is overexpressed in tumour cells with rapid cell turnover. Its concentrations correlate well with the staging and metastatic capability of the tumour cells. We investigated the use of faecal dM2-PK as a noninvasive marker of pouch inflammation (pouchitis) in patients having undergone restorative proctocolectomy.

METHODS

Stool samples were obtained from 46 patients with ulcerative colitis (UC) and eight with familial adenomatous polyposis. Pouchitis was defined using the objective pouchitis score (OPS) and the pouch disease activity index. Faecal dM2-PK was measured using a quantitative sandwich-type enzyme immunoassay (ScheBo Biotech UK) and the results compared with reciprocal faecal calprotectin concentrations.

RESULTS

Using the OPS, 6 of the 46 patients with UC had pouchitis and prepouch ileitis, 13 had UC pouchitis alone, and 27 had a non-inflamed UC pouch. One patient with familial adenomatous polyposis had pouchitis and prepouch ileitis and 7 had an non inflamed pouch. Respective median dM2-PK values (U/ml) for these five groups were 49.5 (4.5-110), 12 (1-192.3), 2.2 (0.1-95.2), 19.5 and 1 (0.1-3). Statistically significant differences were noted between inflamed and non inflamed pouches (P<0.0001). dM2-PK correlated significantly with the OPS, pouch disease activity index, endoscopic appearances, acute histological and neutrophil scores (<0.0001). The receiver operating characteristic analysis demonstrated a sensitivity and specificity of 80 and 70.6%, respectively. dM2-PK and faecal calprotectin concentrations correlated closely (r=0.87, P<0.0001).

CONCLUSION

This study demonstrates that faecal dM2-PK is a sensitive marker of pouch inflammation and that its concentration directly correlates with the objective markers of pouchitis severity.