Hypoxia, glucose metabolism and the Warburg's effect

FIH-1 engages novel binding partners to positively influence epithelial proliferation via p63

Whereas much is known about the genes regulated by ΔNp63α in keratinocytes, how ΔNp63α is regulated is less clear. During studies with the hydroxylase, factor inhibiting hypoxia-inducible factor 1 (FIH-1), we observed increases in epidermal ΔNp63α expression along with proliferative capacity in a conditional FIH-1 transgenic mouse. Conversely, loss of FIH-1 in vivo and in vitro attenuated ΔNp63α expression. To elucidate the FIH-1/p63 relationship, BioID proteomics assays identified FIH-1 binding partners that had the potential to regulate p63 expression. FIH-1 interacts with two previously unknown partners, Plectin1 and signal transducer and activator of transcription 1 (STAT1) leading to the regulation of ΔNp63α expression. Two known interactors of FIH-1, apoptosis-stimulating of P53 protein 2 (ASPP2) and histone deacetylase 1 (HDAC1), were also identified. Knockdown of ASPP2 upregulated ΔNp63α and reversed the decrease in ΔNp63α by FIH-1 depletion. Additionally, FIH-1 regulates growth arrest and DNA damage-45 alpha (GADD45α), a negative regulator of ΔNp63α by interacting with HDAC1. GADD45α knockdown rescued reduction in ΔNp63α by FIH-1 depletion. Collectively, our data reveal that FIH-1 positively regulates ΔNp63α in keratinocytes via variety of signaling partners: (a) Plectin1/STAT1, (b) ASPP2, and (c) HDAC1/GADD45α signaling pathways.

Fish response to hypoxia stress: growth, physiological, and immunological biomarkers

Water quality encompasses the water physical, biological, and chemical parameters. It generally affects the fish growth and welfare. Thus, the success of a commercial aquaculture project depends on supplying the optimum water quality for prompt fish growth at the minimum cost of resources. Although the aquaculture environment is a complicated system, depending on various water quality variables, only less of them have a critical role. One of these vital parameters is dissolved oxygen (DO) level, which requires continuous oversight in aquaculture systems. In addition, the processes of natural stream refinement require suitable DO levels in order to extend for aerobic life forms. The depletion of DO concentration (called hypoxia) in pond water causes great stress on fish where DO levels that remain below 1-2 mg/L for a few hours can adversely affect fish growth resulting in fish death. Furthermore, hypoxia has substantial effects on fish physiological and immune responses, making them more susceptible to diseases. Therefore, to avoid disease outbreak in modern aquaculture production systems where fish are intensified and more crowded, increasing attention should be taken into account on DO levels.

Response of AMP-activated protein kinase and lactate metabolism of largemouth bass (Micropterus salmoides) under acute hypoxic stress

To study adaptation of largemouth bass (Micropterus salmoides) to hypoxic stress, we investigated physiological responses and lactate metabolism of the fish under acute hypoxia. The objectives of this study were to (a) observe changes in glucose, glycogen, and lactate content; (b) detect the activity of lactate dehydrogenase (LDH) in serum, brain, heart, and liver tissues; and (c) quantify the dynamic gene expression of AMP activated protein kinase alpha (AMPKα), hypoxia-inducible factor-1 alpha (HIF-1α), monocarboxylate transporter 1 (MCT1), monocarboxylate transporter 4 (MCT4), and lactate dehydrogenase-a (LDHa) following exposure to hypoxia. The fish were subjected to two hypoxia stresses (dissolved oxygen [DO] 1.20 ± 0.2 mg/L and 3.50 ± 0.3 mg/L, respectively) for 24 h. Our results showed that hypoxic stress significantly increased the decomposition of liver glycogen and significantly increased the concentration of blood glucose; however, the muscle glycogen content was not significantly decreased, which indicates that liver glycogen was the main energy source under acute hypoxia. Moreover, hypoxia led to accumulation of a large amount of lactic acid in tissues, possibly due to the activity of lactic acid dehydrogenase, but this process was delayed in the heart and brain relative to the liver. Additionally, hypoxia induced the expression of AMPKα, HIF-1α, MCT1, MCT4, and LDHa, suggesting that glycometabolism had switched from aerobic to anaerobic. Our results contribute to a better understanding of the molecular mechanisms of the response to hypoxia in largemouth bass.

The Emerging Role of Glucose Metabolism in Cartilage Development

PURPOSE OF REVIEW

Proper cartilage development is critical to bone formation during endochondral ossification. This review highlights the current understanding of various aspects of glucose metabolism in chondrocytes during cartilage development.

RECENT FINDINGS

Recent studies indicate that chondrocytes transdifferentiate into osteoblasts and bone marrow stromal cells during endochondral ossification. In cartilage development, signaling molecules, including IGF2 and BMP2, tightly control glucose uptake and utilization in a stage-specific manner. Perturbation of glucose metabolism alters the course of chondrocyte maturation, suggesting a key role for glucose metabolism during endochondral ossification. During prenatal and postnatal growth, chondrocytes experience bursts of nutrient availability and energy expenditure, which demand sophisticated control of the glucose-dependent processes of cartilage matrix production, cell proliferation, and hypertrophy. Investigating the regulation of glucose metabolism may therefore lead to a unifying mechanism for signaling events in cartilage development and provide insight into causes of skeletal growth abnormalities.

Effect of lincRNA-p21 targeting HIF-1α on biological functions of liver cancer cells

The effects of long intergenic non-coding ribonucleic acid (lincRNA)-p21 targeting hypoxia-inducible factor-1α (HIF-1α) on proliferation, apoptosis and migration of liver cancer cells were investigated. MHCC97H liver cancer cells were infected with control lentivirus (control group) and lincRNA-p21 lentivirus (observation group), and control stable cell lines and lincRNA-p21 stable cell lines were screened and obtained by using puromycin. The expression levels of lincRNA-p21 messenger RNA (mRNA) in the control and observation groups were analyzed via reverse transcription-quantitative polymerase chain reaction (RT-qPCR). Bioinformatics was used to search for the lincRNA-p21 target. The expression of target gene was analyzed via western blotting, and the proliferation, apoptosis, migration and in vivo tumor formation of MHCC97H cells in the control and observation groups were also analyzed. Compared with that in control group, the lincRNA-p21 mRNA level in observation group was increased significantly (P<0.05). It was found via bioinformatic comparison that HIF-1α was one of the targets of lincRNA-p21. Results of Western blotting revealed that the expression level of HIF-1α protein in cells in observation group was significantly downregulated (P<0.05). Besides, the level of vascular endothelial growth factor (VEGF) protein in cells in control group was obviously higher than that in observation group (P<0.05). Compared with those in control group, the cell proliferation and migration capacities in observation group were markedly reduced, but the apoptosis level was significantly increased (P<0.05). According to the in vivo tumor formation assay, the cell proliferation rate in control group was obviously higher than that in observation group (P<0.05). The number of tumor blood vessels in cells in control group was obviously reduced compared with that in observation group (P<0.05). lincRNA-p21 can significantly downregulate the level of HIF-1α, thus downregulating the expression of VEGF and affecting the cell proliferation, apoptosis and migration.

A Novel Lactate Dehydrogenase Inhibitor, 1-(Phenylseleno)-4-(Trifluoromethyl) Benzene, Suppresses Tumor Growth through Apoptotic Cell Death

The Warburg effect, wherein cancer cells prefer glycolysis rather than oxidative phosphorylation even under normoxic conditions, is a major characteristic of malignant tumors. Lactate dehydrogenase A (LDHA) is the main enzyme regulating the Warburg effect, and is thus, a major target for novel anti-cancer drug development. Through our ongoing screening of novel inhibitors, we found that several selenobenzene compounds have inhibitory effects on LDHA activity. Among them, 1-(phenylseleno)-4-(trifluoromethyl) benzene (PSTMB) had the most potent inhibitory effect on the enzymatic activity of LDHA. The results from biochemical assays and computational modeling showed that PSTMB inhibited LDHA activity. In addition, PSTMB inhibited the growth of several tumor cell lines, including NCI-H460, MCF-7, Hep3B, A375, HT29, and LLC. In HT29 human colon cancer cells, PSTMB dose-dependently inhibited the viability of the cells and activity of LDHA, without affecting the expression of LDHA. Under both normoxic and hypoxic conditions, PSTMB effectively reduced LDHA activity and lactate production. Furthermore, PSTMB induced mitochondria-mediated apoptosis of HT29 cells via production of reactive oxygen species. These results suggest that PSTMB may be a novel candidate for development of anti-cancer drugs by targeting cancer metabolism.

Targeting the Cardiomyocyte Cell Cycle for Heart Regeneration

Adult mammalian cardiomyocytes (CMs) exhibit limited proliferative capacity, as cell cycle activity leads to an increase in DNA content, but mitosis and cytokinesis are infrequent. This makes the heart highly inefficient in replacing with neoformed cardiomyocytes lost contractile cells as occurs in diseases such as myocardial infarction and dilated cardiomyopathy. Regenerative therapies based on the implant of stem cells of diverse origin do not warrant engraftment and electromechanical connection of the new cells with the resident ones, a fundamental condition to restore the physiology of the cardiac syncytium. Consequently, there is a growing interest in identifying factors playing relevant roles in the regulation of the CM cell cycle to be targeted in order to induce the resident cardiomyocytes to divide into daughter cells and thus achieve myocardial regeneration with preservation of physiologic syncytial performance.

Wogonin affects proliferation and the energy metabolism of SGC-7901 and A549 cells

Many studies have focused on the identification of therapeutic targets for the treatment of certain types of cancer. Wogonin is a natural flavonoid compound that exhibits a potent anti-cancer effect. The underlying mechanism of wogonin may therefore reveal an effective way to identify novel therapeutic targets. In the current study, growth curves and MTT assays were performed to determine the effects of wogonin in human gastric cancer cells (SGC-7901) and human lung adenocarcinoma cells (A549), respectively. Changes in morphology were observed using hematoxylin and eosin (H&E) staining. The activities of key enzymes in the glycolysis and tricarboxylic acid cycle were measured using spectrophotometry. Western blot analysis was performed to determine the expression levels of hypoxia inducible factor-1α (HIF-1α) and monocarboxylate transporter-4 (MCT-4). Wogonin inhibited cell proliferation in a time- and dose-dependent manner in SGC-7901 and A549 cells. H&E staining suggested that wogonin induced cell morphology changes. In SGC-7901 cells, lactate dehydrogenase (LDH) and succinate dehydrogenase (SDH) activities and adenosine triphosphate (ATP) generation were decreased significantly by wogonin treatment compared with the untreated control. In A549 cells, wogonin significantly reduced LDH activity, but exhibited no significant effects on kinase activities or ATP generation. Furthermore, wogonin significantly decreased HIF-1α and MCT-4 protein expression in SGC-7901 cells, but not in A549 cells. The results demonstrated that wogonin inhibited the energy metabolism, cell proliferation and angiogenesis in SGC-7901 and A549 cells by negatively regulating HIF-1α and MCT-4 expression. The differential regulatory roles of wogonin in metabolism-associated enzymes in human gastric cancer and lung adenocarcinoma cells indicated its various antitumor mechanisms. The different metabolic regulatory mechanisms exhibited by wogonin in different tumor tissues should therefore be considered for antitumor therapy.

Potential roles of IL-1 subfamily members in glycolysis in disease

The interleukin-(IL)-1 subfamily consists of IL-1α, IL-1β, IL-1 receptor antagonist IL-1Ra and IL-33. These cytokines are the main members of the IL-1 family and have been widely recognized as having significant roles in pro-inflammatory and immunomodulatory actions. Mounting evidence has revealed that these cytokines also play key roles in the regulation of glycolysis, which is an important metabolic pathway in most organisms that provides energy. Dysregulation of glycolysis is associated with various diseases, including type 2 diabetes, rheumatoid arthritis (RA) and cancer. We reviewed studies addressing the important roles of IL-1 subfamily cytokines, with particular focus on their ability to regulate glycolysis in disease states. In this review, we summarize the potential roles of IL-1 subfamily members in glycolysis in disease states and address the underlying mechanisms. Furthermore, we discuss the potential of these cytokines as therapeutic targets in clinical applications to provide insight into possible therapeutic strategies for treatment, especially for cancers.

Fructose 2,6-Bisphosphate in Cancer Cell Metabolism

For a long time, pioneers in the field of cancer cell metabolism, such as Otto Warburg, have focused on the idea that tumor cells maintain high glycolytic rates even with adequate oxygen supply, in what is known as aerobic glycolysis or the Warburg effect. Recent studies have reported a more complex situation, where the tumor ecosystem plays a more critical role in cancer progression. Cancer cells display extraordinary plasticity in adapting to changes in their tumor microenvironment, developing strategies to survive and proliferate. The proliferation of cancer cells needs a high rate of energy and metabolic substrates for biosynthesis of biomolecules. These requirements are met by the metabolic reprogramming of cancer cells and others present in the tumor microenvironment, which is essential for tumor survival and spread. Metabolic reprogramming involves a complex interplay between oncogenes, tumor suppressors, growth factors and local factors in the tumor microenvironment. These factors can induce overexpression and increased activity of glycolytic isoenzymes and proteins in stromal and cancer cells which are different from those expressed in normal cells. The fructose-6-phosphate/fructose-1,6-bisphosphate cycle, catalyzed by 6-phosphofructo-1-kinase/fructose 1,6-bisphosphatase (PFK1/FBPase1) isoenzymes, plays a key role in controlling glycolytic rates. PFK1/FBpase1 activities are allosterically regulated by fructose-2,6-bisphosphate, the product of the enzymatic activity of the dual kinase/phosphatase family of enzymes: 6-phosphofructo-2-kinase/fructose 2,6-bisphosphatase (PFKFB1-4) and TP53-induced glycolysis and apoptosis regulator (TIGAR), which show increased expression in a significant number of tumor types. In this review, the function of these isoenzymes in the regulation of metabolism, as well as the regulatory factors modulating their expression and activity in the tumor ecosystem are discussed. Targeting these isoenzymes, either directly or by inhibiting their activating factors, could be a promising approach for treating cancers.

The miR-15b-5p/PDK4 axis regulates osteosarcoma proliferation through modulation of the Warburg effect

Blocking aerobic glycolysis has been proposed as an attractive therapeutic strategy for impairing the proliferation of cancer cells. However, the underlying mechanisms are poorly understood. Here, we show that miR-15b-5p was downregulated in osteosarcoma (OS) and that lower expression of miR-15b-5p promoted proliferation and contributed to the Warburg effect in OS cells. Mechanistically, miR-15b-5p acted as a tumor suppressor in OS by directly targeting pyruvate dehydrogenase kinase-4 and inhibiting its expression. These results reveal a previously unknown function of miR-15b-5p in OS, which is associated with metabolic alterations that promote cancer progression. miR-15b-5p may play an essential role in the molecular therapy of patients with OS.

The potential utility of PFKFB3 as a therapeutic target

INTRODUCTION

It has been known for over half a century that tumors exhibit an increased demand for nutrients to fuel their rapid proliferation. Interest in targeting cancer metabolism to treat the disease has been renewed in recent years with the discovery that many cancer-related pathways have a profound effect on metabolism. Considering the recent increase in our understanding of cancer metabolism and the enzymes and pathways involved, the question arises as to whether metabolism is cancer's Achilles heel. Areas covered: This review summarizes the role of 6-Phosphofructo-2-kinase/fructose-2,6-bisphosphatase 3 (PFKFB3) in glycolysis, cell proliferation, and tumor growth, discussing PFKFB3 gene and isoenzyme regulation and the changes that occur in cancer and inflammatory diseases. Pharmacological options currently available for selective PFKFB3 inhibition are also reviewed. Expert opinion: PFKFB3 plays an important role in sustaining the development and progression of cancer and might represent an attractive target for therapeutic strategies. Nevertheless, clinical trials are needed to follow up on the promising results from preclinical studies with PFKFB3 inhibitors. Combination therapies with PFKFB3 inhibitors, chemotherapeutic drugs, or radiotherapy might improve the efficacy of cancer treatments targeting PFKFB3.

Biochemistry of proinflammatory macrophage activation

In the last decade, metabolism has been recognized as a major determinant of immunological processes. During an inflammatory response, macrophages undergo striking changes in their metabolism. This metabolic reprogramming is governed by a complex interplay between metabolic enzymes and metabolites of different pathways and represents the basis for proper macrophage function. It is now evident that these changes go far beyond the well-known Warburg effect and the perturbation of metabolic targets is being investigated as a means to treat infections and auto-immune diseases. In the present review, we will aim to provide an overview of the metabolic responses during proinflammatory macrophage activation and show how these changes modulate the immune response.

SLIT2/ROBO1 axis contributes to the Warburg effect in osteosarcoma through activation of SRC/ERK/c-MYC/PFKFB2 pathway

Cellular metabolic reprogramming is the main characteristic of cancer cells and identification of targets using this metabolic pattern is extremely important to treat cancers, such as osteosarcoma (OS). In this study, SLIT2 and ROBO1 were upregulated in OS, and higher expression of ROBO1 was associated with worse overall survival rate. Furthermore, in vitro and in vivo experiments demonstrated that the SLIT2/ROBO1 axis promotes proliferation, inhibits apoptosis, and contributes to the Warburg effect in OS cells. Mechanistically, the SLIT2/ROBO1 axis exerted cancer-promoting effects on OS via activation of the SRC/ERK/c-MYC/PFKFB2 pathway. Taken together, the findings reveal a previously unappreciated function of SLIT2/ROBO1 signaling in OS, which is intertwined with metabolic alterations that promote cancer progression. Targeting the SLIT2/ROBO1 axis may be a potential therapeutic approach for patients with OS.

HIF-1, Metabolism, and Diabetes in the Embryonic and Adult Heart

The heart is able to metabolize any substrate, depending on its availability, to satisfy its energy requirements. Under normal physiological conditions, about 95% of ATP is produced by oxidative phosphorylation and the rest by glycolysis. Cardiac metabolism undergoes reprograming in response to a variety of physiological and pathophysiological conditions. Hypoxia-inducible factor 1 (HIF-1) mediates the metabolic adaptation to hypoxia and ischemia, including the transition from oxidative to glycolytic metabolism. During embryonic development, HIF-1 protects the embryo from intrauterine hypoxia, its deletion as well as its forced expression are embryonically lethal. A decrease in HIF-1 activity is crucial during perinatal remodeling when the heart switches from anaerobic to aerobic metabolism. In the adult heart, HIF-1 protects against hypoxia, although its deletion in cardiomyocytes affects heart function even under normoxic conditions. Diabetes impairs HIF-1 activation and thus, compromises HIF-1 mediated responses under oxygen-limited conditions. Compromised HIF-1 signaling may contribute to the teratogenicity of maternal diabetes and diabetic cardiomyopathy in adults. In this review, we discuss the function of HIF-1 in the heart throughout development into adulthood, as well as the deregulation of HIF-1 signaling in diabetes and its effects on the embryonic and adult heart.

CD44/CD44v6 a Reliable Companion in Cancer-Initiating Cell Maintenance and Tumor Progression

Metastasis is the leading cause of cancer death, tumor progression proceeding through emigration from the primary tumor, gaining access to the circulation, leaving the circulation, settling in distant organs and growing in the foreign environment. The capacity of a tumor to metastasize relies on a small subpopulation of cells in the primary tumor, so called cancer-initiating cells (CIC). CIC are characterized by sets of markers, mostly membrane anchored adhesion molecules, CD44v6 being the most frequently recovered marker. Knockdown and knockout models accompanied by loss of tumor progression despite unaltered primary tumor growth unraveled that these markers are indispensable for CIC. The unexpected contribution of marker molecules to CIC-related activities prompted research on underlying molecular mechanisms. This review outlines the contribution of CD44, particularly CD44v6 to CIC activities. A first focus is given to the impact of CD44/CD44v6 to inherent CIC features, including the crosstalk with the niche, apoptosis-resistance, and epithelial mesenchymal transition. Following the steps of the metastatic cascade, we report on supporting activities of CD44/CD44v6 in migration and invasion. These CD44/CD44v6 activities rely on the association with membrane-integrated and cytosolic signaling molecules and proteases and transcriptional regulation. They are not restricted to, but most pronounced in CIC and are tightly regulated by feedback loops. Finally, we discuss on the engagement of CD44/CD44v6 in exosome biogenesis, loading and delivery. exosomes being the main acteurs in the long-distance crosstalk of CIC with the host. In brief, by supporting the communication with the niche and promoting apoptosis resistance CD44/CD44v6 plays an important role in CIC maintenance. The multifaceted interplay between CD44/CD44v6, signal transducing molecules and proteases facilitates the metastasizing tumor cell journey through the body. By its engagement in exosome biogenesis CD44/CD44v6 contributes to disseminated tumor cell settlement and growth in distant organs. Thus, CD44/CD44v6 likely is the most central CIC biomarker.

Warburg effect-damping of electromagnetic oscillations

Mitochondrial dysfunction is a central defect in cells creating the Warburg and reverse Warburg effect cancers. However, the link between mitochondrial dysfunction and cancer has not yet been clearly explained. Decrease of mitochondrial oxidative energy production to about 50 % in comparison with healthy cells may be caused by inhibition of pyruvate transfer into mitochondrial matrix and/or disturbed H⁺ ion transfer across inner mitochondrial membrane into cytosol. Lowering of the inner membrane potential and shifting of the working point of mitochondria to high values of pH above an intermediate point causes reorganization of the ordered water layer at the mitochondrial membrane. The reorganized ordered water layers at high pH values release electrons which are transferred to the cytosol rim of the layer. The electrons damp electromagnetic activity of Warburg effect cancer cells or fibroblasts associated with reverse Warburg effect cancer cells leading to lowered electromagnetic activity, disturbed coherence, increased frequency of oscillations and decreased level of biological functions. In reverse Warburg effect cancers, associated fibroblasts supply energy-rich metabolites to the cancer cell resulting in increased power of electromagnetic field, fluctuations due to shift of oscillations to an unstable nonlinear region, decreased frequency and loss of coherence.

Phosphorylation of PPARγ at Ser84 promotes glycolysis and cell proliferation in hepatocellular carcinoma by targeting PFKFB4

Peroxisome proliferator-activating receptor γ (PPARγ), a transcription factor, is involved in many important biological processes, including cell terminal differentiation, survival and apoptosis. However, the role of PPARγ, which regulates tumour promoter and oncogene expression, is not well understood in hepatocellular carcinoma (HCC). In the present study, based on evidence from clinical samples that phosphorylation of PPARγ at Ser84 is up-regulated in human liver tumours, we confirmed that phosphorylation of PPARγ was also significantly increased in an HCC mouse model and was increased by Mitogen-activated protein kinase (MEK)/ Extracellular-signal-regulated kinases (ERK) kinase. Next, we performed an RNA microarray analysis, and our data indicated that dephosphorylation of PPARγ at Ser84 affects the expression of glycolysis-related genes and pro-proliferation genes, which supposedly promote proliferation of HCC cells. Using a chromatin immunoprecipitation (ChIP) assay, we demonstrated that the observed PPARγ-mediated induction of 6-phosphofructo-2-kinase/fructose-2,6-biphosphatase 4 (PFKFB4) expression was directly modulated by the transcriptional activity of its promoter. Furthermore, using knockdown of PFKFB4, we elucidated that the stimulation of PPARγ phosphorylation on glycolysis and proliferation in HCC is dependent on PFKFB4. Together, these findings extend our understanding of how liver tumour cells reprogram their glycolytic pathways by post-translational modification of specific transcription factors and lay a foundation for the screening of new targets for the treatment of HCC.

TP53-inducible Glycolysis and Apoptosis Regulator (TIGAR) Metabolically Reprograms Carcinoma and Stromal Cells in Breast Cancer

A subgroup of breast cancers has several metabolic compartments. The mechanisms by which metabolic compartmentalization develop in tumors are poorly characterized. TP53 inducible glycolysis and apoptosis regulator (TIGAR) is a bisphosphatase that reduces glycolysis and is highly expressed in carcinoma cells in the majority of human breast cancers. Hence we set out to determine the effects of TIGAR expression on breast carcinoma and fibroblast glycolytic phenotype and tumor growth. The overexpression of this bisphosphatase in carcinoma cells induces expression of enzymes and transporters involved in the catabolism of lactate and glutamine. Carcinoma cells overexpressing TIGAR have higher oxygen consumption rates and ATP levels when exposed to glutamine, lactate, or the combination of glutamine and lactate. Coculture of TIGAR overexpressing carcinoma cells and fibroblasts compared with control cocultures induce more pronounced glycolytic differences between carcinoma and fibroblast cells. Carcinoma cells overexpressing TIGAR have reduced glucose uptake and lactate production. Conversely, fibroblasts in coculture with TIGAR overexpressing carcinoma cells induce HIF (hypoxia-inducible factor) activation with increased glucose uptake, increased 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase-3 (PFKFB3), and lactate dehydrogenase-A expression. We also studied the effect of this enzyme on tumor growth. TIGAR overexpression in carcinoma cells increases tumor growth in vivo with increased proliferation rates. However, a catalytically inactive variant of TIGAR did not induce tumor growth. Therefore, TIGAR expression in breast carcinoma cells promotes metabolic compartmentalization and tumor growth with a mitochondrial metabolic phenotype with lactate and glutamine catabolism. Targeting TIGAR warrants consideration as a potential therapy for breast cancer.

Hypoxia-induced NIPP1 activation enhances metastatic potential and predicts poor prognosis in hepatocellular carcinoma

Hypoxia is known to promote hepatocellular carcinoma (HCC) invasion and metastasis and nuclear inhibitor of protein phosphatase 1 (NIPP1) overexpression contributes to the malignant phenotype in HCC. The aim of this study was to investigate the role of NIPP1 in HCC development under hypoxia. We first conducted a study with 106 cases to explore the association of NIPP1 and/or enhancer of zeste homolog 2 (EZH2) expression with poor prognosis in HCC. Then additional 352 independent cases were recruited to validate the results in the first stage. Hypoxia was induced by culturing HCC cells in 1 % O₂ or of the treatment with hypoxic agent. The expression levels of NIPP1/EZH2 in both HCC tissues and HCC cell lines were detected by RT-PCR, Western blot, or immunohistochemistry. We also studied the effects of the loss of function of NIPP1 and EZH2 on malignant phenotypes, downstream pathway, and inflammatory factors activities using gene silencing strategy. Overall, we found that NIPP1 and EZH2 were overexpressed in both HCC tissue samples and HCC cell lines. High expression of HIPP1 was associated with poor prognosis and clinicopathological features in patients with advanced HCC. HIPP1 expression positively correlated with the expression of hypoxia marker (carbonic anhydrase IX). Hypoxia induced high expression of NIPP1. NIPP1/EZH2 knockdown in HCC cell lines under hypoxia suppressed the malignant phenotypes, reduced the expression of hypoxia-inducible Factor 1α, downstream molecules of EZH2, and inhibit the activity of inflammatory factors. In conclusion, we found that NIPP1 could be activated by hypoxia and contributed to hypoxia-induced invasive and metastatic potential in HCC.

Akt mediates TIGAR induction in HeLa cells following PFKFB3 inhibition

Neoplastic cells metabolize higher amounts of glucose relative to normal cells in order to cover increased energetic and anabolic needs. Inhibition of the glycolytic enzyme 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase 3 (PFKFB3) diminishes cancer cell proliferation and tumour growth in animals. In this work, we investigate the crosstalk between PFKFB3 and TIGAR (TP53-Induced Glycolysis and Apoptosis Regulator), a protein known to protect cells from oxidative stress. Our results show consistent TIGAR induction in HeLa cells in response to PFKFB3 knockdown. Upon PFKFB3 silencing, cells undergo oxidative stress and trigger Akt phosphorylation. This leads to induction of a TIGAR-mediated prosurvival pathway that reduces both oxidative stress and cell death. As TIGAR is known to have a role in DNA repair, it could serve as a potential target for the development of effective antineoplastic therapies.

Myristica fragrans Suppresses Tumor Growth and Metabolism by Inhibiting Lactate Dehydrogenase A

Most cancer cells predominantly produce ATP by maintaining a high rate of lactate fermentation, rather than by maintaining a comparatively low rate of tricarboxylic acid cycle, i.e., Warburg's effect. In the pathway, the pyruvate produced by glycolysis is converted to lactic acid by lactate dehydrogenase (LDH). Here, we demonstrated that water extracts from the seeds of Myristica fragrans Houtt. (MF) inhibit the in vitro enzymatic activity of LDH. MF effectively suppressed cell growth and the overall Warburg effect in HT29 human colon cancer cells. Although the expression of LDH-A was not changed by MF, both lactate production and LDH activity were decreased in MF-treated cells under both normoxic and hypoxic conditions. In addition, intracellular ATP levels were also decreased by MF treatment, and the uptake of glucose was also reduced by MF treatment. Furthermore, the experiment on tumor growth in the in vivo mice model revealed that MF effectively reduced the growth of allotransplanted Lewis lung carcinoma cells. Taken together, these results suggest that MF effectively inhibits cancer growth and metabolism by inhibiting the activity of LDH, a major enzyme responsible for regulating cancer metabolism. These results implicate MF as a potential candidate for development into a novel drug against cancer through inhibition of LDH activity.

Dual Regulation of Cell Death and Cell Survival upon Induction of Cellular Stress by Isopimara-7,15-Dien-19-Oic Acid in Cervical Cancer, HeLa Cells In vitro

The Fritillaria imperialis is an ornamental flower that can be found in various parts of the world including Iraq, Afghanistan, Pakistan, and the Himalayas. The use of this plant as traditional remedy is widely known. This study aims to unveil the anti-cancer potentials of Isopimara-7,15-Dien-19-Oic Acid, extracted from the bulbs of F. imperialis in cervical cancer cell line, HeLa cells. Flow cytometry analysis of cell death, gene expression analysis via cDNA microarray and protein array were performed. Based on the results, Isopimara-7,15-Dien-19-Oic acid simultaneously induced cell death and promoted cell survival. The execution of apoptosis was apparent based on the flow cytometry results and regulation of both pro and anti-apoptotic genes. Additionally, the regulation of anti-oxidant genes were up-regulated especially thioredoxin, glutathione and superoxide dismutase- related genes. Moreover, the treatment also induced the activation of pro-survival heat shock proteins. Collectively, Isopimara-7,15-Dien-19-Oic Acid managed to induce cellular stress in HeLa cells and activate several anti- and pro survival pathways.

Glucose metabolic phenotype of pancreatic cancer

AIM: To construct a global “metabolic phenotype” of pancreatic ductal adenocarcinoma (PDAC) reflecting tumour-related metabolic enzyme expression.

METHODS: A systematic review of the literature was performed using OvidSP and PubMed databases using keywords “pancreatic cancer” and individual glycolytic and mitochondrial oxidative phosphorylation (MOP) enzymes. Both human and animal studies investigating the oncological effect of enzyme expression changes and inhibitors in both an in vitro and in vivo setting were included in the review. Data reporting changes in enzyme expression and the effects on PDAC cells, such as survival and metastatic potential, were extracted to construct a metabolic phenotype.

RESULTS: Seven hundred and ten papers were initially retrieved, and were screened to meet the review inclusion criteria. 107 unique articles were identified as reporting data involving glycolytic enzymes, and 28 articles involving MOP enzymes in PDAC. Data extraction followed a pre-defined protocol. There is consistent over-expression of glycolytic enzymes and lactate dehydrogenase in keeping with the Warburg effect to facilitate rapid adenosine-triphosphate production from glycolysis. Certain isoforms of these enzymes were over-expressed specifically in PDAC. Altering expression levels of HK, PGI, FBA, enolase, PK-M2 and LDA-A with metabolic inhibitors have shown a favourable effect on PDAC, thus identifying these as potential therapeutic targets. However, the Warburg effect on MOP enzymes is less clear, with different expression levels at different points in the Krebs cycle resulting in a fundamental change of metabolite levels, suggesting that other essential anabolic pathways are being stimulated.

CONCLUSION: Further characterisation of the PDAC metabolic phenotype is necessary as currently there are few clinical studies and no successful clinical trials targeting metabolic enzymes.

Pyruvate Kinase M2: A Novel Biomarker for the Early Detection of Acute Kidney Injury

The identification of biomarkers for the early detection of acute kidney injury (AKI) is clinically important. Acute kidney injury (AKI) in critically ill patients is closely associated with increased morbidity and mortality. Conventional biomarkers, such as serum creatinine (SCr) and blood urea nitrogen (BUN), are frequently used to diagnose AKI. However, these biomarkers increase only after significant structural damage has occurred. Recent efforts have focused on identification and validation of new noninvasive biomarkers for the early detection of AKI, prior to extensive structural damage. Furthermore, AKI biomarkers can provide valuable insight into the molecular mechanisms of this complex and heterogeneous disease. Our previous study suggested that pyruvate kinase M2 (PKM2), which is excreted in the urine, is a sensitive biomarker for nephrotoxicity. To appropriately and optimally utilize PKM2 as a biomarker for AKI requires its complete characterization. This review highlights the major studies that have addressed the diagnostic and prognostic predictive power of biomarkers for AKI and assesses the potential usage of PKM2 as an early biomarker for AKI. We summarize the current state of knowledge regarding the role of biomarkers and the molecular and cellular mechanisms of AKI. This review will elucidate the biological basis of specific biomarkers that will contribute to improving the early detection and diagnosis of AKI.

lncRNAs in Stress Response

All living organisms sense and respond to harmful changes in their intracellular and extracellular environment through complex signaling pathways that lead to changes in gene expression and cellular function in order to maintain homeostasis. Long non-coding RNAs (lncRNAs), a large and heterogeneous group of functional RNAs, play important roles in cellular response to stressful conditions. lncRNAs constitute a significant fraction of the genes differentially expressed in response to diverse stressful stimuli and, once induced, contribute to the regulation of downstream cellular processes, including feedback regulation of key stress response proteins. While many lncRNAs seem to be induced in response to a specific stress, there is significant overlap between lncRNAs induced in response to different stressful stimuli. In addition to stress-induced RNAs, several constitutively expressed lncRNAs also exert a strong regulatory impact on the stress response. Although our understanding of the contribution of lncRNAs to the cellular stress response is still highly rudimentary, the existing data point to the presence of a complex network of lncRNAs, miRNAs, and proteins in regulation of the cellular response to stress.

The Warburg effect: molecular aspects and therapeutic possibilities

It has been about nine decades since the proposal of Otto Warburg on the metabolism of cancer cells. Unlike normal cells which undergo glycolysis and oxidative phosphorylation in the presence of oxygen, proliferating and cancer cells exhibit an increased uptake of glucose and increased rate of glycolysis and predominantly undergo lactic acid fermentation. Whether this phenomenon is the consequence of genetic dysregulation in cancer or is the cause of cancer still remains unknown. However, there is certainly a strong link between the genetic factors, epigenetic modulation, cancer immunosurveillance and the Warburg effect, which will be discussed in this review. Dichloroacetate and 3-bromopyruvate are among the substances that have been studied as potential cancer therapies. With our expanding knowledge of cellular metabolism, therapies targeting the Warburg effect appear very promising. This review discusses different aspects of these emerging therapies.

Hypoxia preconditioning induced HIF-1α promotes glucose metabolism and protects mitochondria in liver I/R injury

BACKGROUND

Ischemia and reperfusion (I/R) injury is one of the main lesions after liver transplantation. This study aims to detect hypoxia-induced HIF-1α protects transplanted liver against I/R injury by promoting glucose metabolism to decrease mitochondrial injury and apoptosis on rat model.

METHODS

The rats were given a treatment of 90 min non-lethal hypoxic preconditioning to induce and increase the HIF-1α expression. The autologous orthotopic liver transplantation model was used to imitate liver I/R injury.

RESULTS

Hypoxic-induced HIF-1α was detected to increase in liver tissue after 90-minute hypoxic environment (HP vs. Ctrl, *P<0.001). After operation, the expression of HIF-1α in liver tissue was also stayed at a high level. At 24h after operation, several genes were promoted, such as the levels of HK-2 (HP vs. AT, 24h, *P=0.004), Lactate dehydrogenase (LDHA) (HP vs. AT, 24h, *P=0.003), pyruvate dehydrogenase kinase (PDK-1) (HP vs. AT, 24h, *P=0.007), even the NF-κB and Erk pathways. From the TUNEL assay, the apoptosis in hypoxic preconditioning liver tissue was decreased compared with non-HP operative group at 12h after operation. The expressions of cleaved-caspase 3 (HP vs. AT, *P=0.0119) and PARP (HP vs. AT, *P=0.0134) in HP group were also significantly lower than AT group.

CONCLUSION

The hypoxia-induced HIF-1α could promote glucose metabolism to protect hepatocellular mitochondria from damage. It could be a useful way to protect liver against I/R injuries and inflammatory injury, and particularly promote the recovery of graft function.

Overexpression of miR-206 suppresses glycolysis, proliferation and migration in breast cancer cells via PFKFB3 targeting

miRNAs, sorting as non-coding RNAs, are differentially expressed in breast tumor and act as tumor promoters or suppressors. miR-206 could suppress the progression of breast cancer, the mechanism of which remains unclear. The study here was aimed to investigate the effect of miR-206 on human breast cancers. We found that miR-206 was down-regulated while one of its predicted targets, 6-Phosphofructo-2-kinase (PFKFB3) was up-regulated in human breast carcinomas. 17β-estradiol dose-dependently decreased miR-206 expression as well as enhanced PFKFB3 mRNA and protein expression in estrogen receptor α (ERα) positive breast cancer cells. Furthermore, we identified that miR-206 directly interacted with 3'-untranslated region (UTR) of PFKFB3 mRNA. miR-206 modulated PFKFB3 expression in MCF-7, T47D and SUM159 cells, which was influenced by 17β-estradiol depending on ERα expression. In addition, miR-206 overexpression impeded fructose-2,6-bisphosphate (F2,6BP) production, diminished lactate generation and reduced cell proliferation and migration in breast cancer cells. In conclusion, our study demonstrated that miR-206 regulated PFKFB3 expression in breast cancer cells, thereby stunting glycolysis, cell proliferation and migration.

CD44, Hyaluronan, the Hematopoietic Stem Cell, and Leukemia-Initiating Cells

CD44 is an adhesion molecule that varies in size due to glycosylation and insertion of so-called variant exon products. The CD44 standard isoform (CD44s) is highly expressed in many cells and most abundantly in cells of the hematopoietic system, whereas expression of CD44 variant isoforms (CD44v) is more restricted. CD44s and CD44v are known as stem cell markers, first described for hematopoietic stem cells and later on confirmed for cancer- and leukemia-initiating cells. Importantly, both abundantly expressed CD44s as well as CD44v actively contribute to the maintenance of stem cell features, like generating and embedding in a niche, homing into the niche, maintenance of quiescence, and relative apoptosis resistance. This is surprising, as CD44 is not a master stem cell gene. I here will discuss that the functional contribution of CD44 relies on its particular communication skills with neighboring molecules, adjacent cells and, last not least, the surrounding matrix. In fact, it is the interaction of the hyaluronan receptor CD44 with its prime ligand, which strongly assists stem cells to fulfill their special and demanding tasks. Recent fundamental progress in support of this “old” hypothesis, which may soon pave the way for most promising new therapeutics, is presented for both hematopoietic stem cell and leukemia-initiating cell. The contribution of CD44 to the generation of a stem cell niche, to homing of stem cells in their niche, to stem cell quiescence and apoptosis resistance will be in focus.

SIRT1 deacetylates and stabilizes hypoxia-inducible factor-1α (HIF-1α) via direct interactions during hypoxia

Upon shift to a hypoxic environment, cellular HIF-1α protein is stabilized, with a rapid decline in oxygen-sensitive hydroxylation. Several additional post-translational modifications of HIF-1α are critical in controlling protein stability during hypoxia. In the present study, we showed that SIRT1 stabilizes HIF-1α via direct binding and deacetylation during hypoxia. SIRT1 depletion or inactivation led to reduced hypoxic HIF-1α accumulation, accompanied by an increase in HIF-1α acetylation. Impaired HIF-1α accumulation was recovered upon inhibition of 26S proteasome activity, indicating that SIRT1 is essential for HIF-1α stabilization during hypoxia. Consistently, HIF-1α accumulation was enhanced upon overexpression of wild-type SIRT1, but not its dominant-negative form. SIRT1-mediated accumulation of HIF-1α protein led to increased expression of HIF-1α target genes, including VEGF, GLUT1 and MMP2, and ultimate promotion of cancer cell invasion. These findings collectively imply that hypoxic HIF-1α stabilization requires SIRT1 activation. Furthermore, SIRT1 protection of HIF-1α from acetylation may be a prerequisite for stabilization and consequent enhancement of cell invasion.

TGFβ-induced deptor suppression recruits mTORC1 and not mTORC2 to enhance collagen I (α2) gene expression

Enhanced TGFβ activity contributes to the accumulation of matrix proteins including collagen I (α2) by proximal tubular epithelial cells in progressive kidney disease. Although TGFβ rapidly activates its canonical Smad signaling pathway, it also recruits noncanonical pathway involving mTOR kinase to regulate renal matrix expansion. The mechanism by which chronic TGFβ treatment maintains increased mTOR activity to induce the matrix protein collagen I (α2) expression is not known. Deptor is an mTOR interacting protein that suppresses mTOR activity in both mTORC1 and mTORC2. In proximal tubular epithelial cells, TGFβ reduced deptor levels in a time-dependent manner with concomitant increase in both mTORC1 and mTORC2 activities. Expression of deptor abrogated activity of mTORC1 and mTORC2, resulting in inhibition of collagen I (α2) mRNA and protein expression via transcriptional mechanism. In contrast, neutralization of endogenous deptor by shRNAs increased activity of both mTOR complexes and expression of collagen I (α2) similar to TGFβ treatment. Importantly, downregulation of deptor by TGFβ increased the expression of Hif1α by increasing translation of its mRNA. TGFβ-induced deptor downregulation promotes Hif1α binding to its cognate hypoxia responsive element in the collagen I (α2) gene to control its protein expression via direct transcriptional mechanism. Interestingly, knockdown of raptor to specifically block mTORC1 activity significantly inhibited expression of collagen I (α2) and Hif1α while inhibition of rictor to prevent selectively mTORC2 activation did not have any effect. Critically, our data provide evidence for the requirement of TGFβ-activated mTORC1 only by deptor downregulation, which dominates upon the bystander mTORC2 activity for enhanced expression of collagen I (α2). Our results also suggest the presence of a safeguard mechanism involving deptor-mediated suppression of mTORC1 activity against developing TGFβ-induced renal fibrosis.

Mechanisms of regulation of PFKFB expression in pancreatic and gastric cancer cells

Enzymes 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase-3 and -4 (PFKFB-3 and PFKFB-4) play a significant role in the regulation of glycolysis in cancer cells as well as its proliferation and survival. The expression of these mRNAs is increased in malignant tumors and strongly induced in different cancer cell lines by hypoxia inducible factor (HIF) through active HIF binding sites in promoter region of PFKFB-4 and PFKFB-3 genes. Moreover, the expression and hypoxia responsibility of PFKFB-4 and PFKFB-3 was also shown for pancreatic (Panc1, PSN-1, and MIA PaCa-2) as well as gastric (MKN45 and NUGC3) cancer cells. At the same time, their basal expression level and hypoxia responsiveness vary in the different cells studied: the highest level of PFKFB-4 protein expression was found in NUGC3 gastric cancer cell line and lowest in Panc1 cells, with a stronger response to hypoxia in the pancreatic cancer cell line. Overexpression of different PFKFB in pancreatic and gastric cancer cells under hypoxic condition is correlated with enhanced expression of vascular endothelial growth factor (VEGF) and Glut1 mRNA as well as with increased level of HIF-1α protein. Increased expression of different PFKFB genes was also demonstrated in gastric, lung, breast, and colon cancers as compared to corresponding non-malignant tissue counterparts from the same patients, being more robust in the breast and lung tumors. Moreover, induction of PFKFB-4 mRNA expression in the breast and lung cancers is stronger than PFKFB-3 mRNA. The levels of both PFKFB-4 and PFKFB-3 proteins in non-malignant gastric and colon tissues were more pronounced than in the non-malignant breast and lung tissues. It is interesting to note that Panc1 and PSN-1 cells transfected with dominant/negative PFKFB-3 (dnPFKFB-3) showed a lower level of endogenous PFKFB-3, PFKFB-4, and VEGF mRNA expressions as well as a decreased proliferation rate of these cells. Moreover, a similar effect had dnPFKFB-4. In conclusion, there is strong evidence that PFKFB-4 and PFKFB-3 isoenzymes are induced under hypoxia in pancreatic and other cancer cell lines, are overexpressed in gastric, colon, lung, and breast malignant tumors and undergo changes in their metabolism that contribute to the proliferation and survival of cancer cells. Thus, targeting these PFKFB may therefore present new therapeutic opportunities.

Redox signaling in cardiac renewal

SIGNIFICANCE

Utilizing oxygen (O2) through mitochondrial oxidative phosphorylation enables organisms to generate adenosine triphosphate (ATP) with a higher efficiency than glycolysis, but it results in increased reactive oxygen species production from mitochondria, which can result in stem cell dysfunction and senescence.

RECENT ADVANCES

In the postnatal organism, the hematopoietic system represents a classic example of the role of stem cells in cellular turnover and regeneration. However, in other organs such as the heart, both the degree and source of cellular turnover have been heavily contested.

CRITICAL ISSUES

Although recent evidence suggests that the major source of the limited cardiomyocyte turnover in the adult heart is cardiomyocyte proliferation, the identity and potential role of undifferentiated cardiac progenitor cells remain controversial. Several types of cardiac progenitor cells have been identified, and several studies have identified an important role of redox and metabolic regulation in survival and differentiation of cardiac progenitor cells. Perhaps a simple way to approach these controversies is to focus on the multipotentiality characteristics of a certain progenitor population, and not necessarily its ability to give rise to all cell types within the heart. In addition, it is important to note that cycling cells in the heart may express markers of differentiation or may be truly undifferentiated, and for the purpose of this review, we will refer to these cycling cells as progenitors.

FUTURE DIRECTIONS

We propose that hypoxia, redox signaling, and metabolic phenotypes are major regulators of cardiac renewal, and may prove to be important therapeutic targets for heart regeneration.

Autophagy, Warburg, and Warburg reverse effects in human cancer

Autophagy is a highly regulated-cell pathway for degrading long-lived proteins as well as for clearing cytoplasmic organelles. Autophagy is a key contributor to cellular homeostasis and metabolism. Warburg hypothesized that cancer growth is frequently associated with a deviation of a set of energy generation mechanisms to a nonoxidative breakdown of glucose. This cellular phenomenon seems to rely on a respiratory impairment, linked to mitochondrial dysfunction. This mitochondrial dysfunction results in a switch to anaerobic glycolysis. It has been recently suggested that epithelial cancer cells may induce the Warburg effect in neighboring stromal fibroblasts in which autophagy was activated. These series of observations drove to the proposal of a putative reverse Warburg effect of pathophysiological relevance for, at least, some tumor phenotypes. In this review we introduce the autophagy process and its regulation and its selective pathways and role in cancer cell metabolism. We define and describe the Warburg effect and the newly suggested "reverse" hypothesis. We also discuss the potential value of modulating autophagy with several pharmacological agents able to modify the Warburg effect. The association of the Warburg effect in cancer and stromal cells to tumor-related autophagy may be of relevance for further development of experimental therapeutics as well as for cancer prevention.

The Warburg effect revisited--lesson from the Sertoli cell

Otto Warburg observed that cancerous cells prefer fermentative instead of oxidative metabolism of glucose, although the former is in theory less efficient. Since Warburg's pioneering works, special attention has been given to this difference in cell metabolism. The Warburg effect has been implicated in cell transformation, immortalization, and proliferation during tumorigenesis. Cancer cells display enhanced glycolytic activity, which is correlated with high proliferation, and thus, glycolysis appears to be an excellent candidate to target cancer cells. Nevertheless, little attention has been given to noncancerous cells that exhibit a "Warburg-like" metabolism with slight, but perhaps crucial, alterations that may provide new directions to develop new and effective anticancer therapies. Within the testis, the somatic Sertoli cell (SC) presents several common metabolic features analogous to cancer cells, and a clear "Warburg-like" metabolism. Nevertheless, SCs actively proliferate only during a specific time period, ceasing to divide in most species after puberty, when they become terminally differentiated. The special metabolic features of SC, as well as progression from the immature but proliferative state, to the mature nonproliferative state, where a high glycolytic activity is maintained, make these cells unique and a good model to discuss new perspectives on the Warburg effect. Herein we provide new insight on how the somatic SC may be a source of new and exciting information concerning the Warburg effect and cell proliferation.

1HNMR-based metabolomic profile of rats with experimental acute pancreatitis

Background

Acute pancreatitis (AP) is a common inflammatory disease of the pancreas accompanied by serious metabolic disturbances. Nevertheless, the specific metabolic process of this disease is still unclear. Characterization of the metabolome may help identify biomarkers for AP. To identify potential biomarkers, this study therefore investigated the 1H-nuclear magnetic resonance (NMR)-based metabolomic profile of AP.

Methods

Fourteen male adult Sprague–Dawley rats were randomized into two groups: the AP group, in which AP was induced by retrograde ductal infusion of 3.5% sodium taurocholate; and the sham operation group (SO), in which rats were infused with 0.9% saline. Blood samples were obtained 12 hours later and a 600 MHz superconducting NMR spectrometer was used to detect plasma metabolites. Principal components analysis (PCA) and partial least squares-discriminant analysis after orthogonal signal correction (OSC-PLS-DA) were used to analyze both longitudinal Eddy-delay (LED) and Carr–Purcell–Meiboom–Gill (CPMG) spectra.

Results

Differences in plasma metabolites between the two groups were detected by PCA and PLS-DA of 1HNMR spectra. Compared with the SO group, plasma levels of lactate (δ 1.3, 1.34, 4.1), valine (δ 0.98, 1.02), succinic acid (δ 2.38), 3-hydroxybutyric acid (3-HB, δ 1.18), high density lipoprotein (HDL, δ 0.8), and unsaturated fatty acid (UFA, δ 2.78, 5.3) were elevated in the AP group, while levels of glycerol (δ 3.58, 3.66), choline (δ 3.22), trimethylamine oxide (TMAO, δ 3.26), glucose (δ 3–4), glycine (δ 3.54), very low density lipoprotein (VLDL, δ 1.34) and phosphatidylcholine (Ptd, δ 2.78) were decreased.

Conclusions

AP has a characteristic metabolic profile. Lactate, valine, succinic acid, 3-HB, HDL, UFA, glycerol, choline, TMAO, glucose, glycine, VLDL, and Ptd may be potential biomarkers of early stage AP.

Cancer may be a pathway to cell survival under persistent hypoxia and elevated ROS: a model for solid-cancer initiation and early development

A number of proposals have been made in the past century regarding what may drive sporadic cancers to initiate and develop. Yet the problem remains largely unsolved as none of the proposals have been widely accepted as cancer-initiation drivers. We propose here a driver model for the initiation and early development of solid cancers associated with inflammation-induced chronic hypoxia and reactive oxygen species (ROS) accumulation. The model consists of five key elements: (i)human cells tend to have a substantial gap between ATP demand and supply during chronic hypoxia, which would inevitably lead to increased uptake of glucose and accumulation of its metabolites; (ii) the accumulation of these metabolites will cast mounting pressure on the cells and ultimately result in the production and export of hyaluronic acid; (iii) the exported hyaluronic acid will be degraded into fragments of various sizes, serving as tissue-repair signals, including signals for cell proliferation, cell survival and angiogenesis, which lead to the initial proliferation of the underlying cells; (iv) cell division provides an exit for the accumulated glucose metabolites using them towards macromolecular synthesis for the new cell, and hence alleviate the pressure from the metabolite accumulation; and (v) this process continues as long as the hypoxic condition persists. In tandem, genetic mutations may be selected to make cell divisions and hence survival more sustainable and efficient, also increasingly more uncontrollable. This model also applies to some hereditary cancers as their key mutations, such as BRCA for breast cancer, generally lead to increased ROS and ultimately to repression of mitochondrial activities and up-regulation of glycolysis, as well as hypoxia; hence the energy gap, glucose-metabolite accumulation, hyaluronic acid production and continuous cell division for survival.

Anticancer activity of structurally related ruthenium(II) cyclopentadienyl complexes

A set of structurally related Ru(η(5)-C5H5) complexes with bidentate N,N'-heteroaromatic ligands have been evaluated as prospective metallodrugs, with focus on exploring the uptake and cell death mechanisms and potential cellular targets. We have extended these studies to examine the potential of these complexes to target cancer cell metabolism, the energetic-related phenotype of cancer cells. The observations that these complexes can enter cells, probably facilitated by binding to plasma transferrin, and can be retained preferentially at the membranes prompted us to explore possible membrane targets involved in cancer cell metabolism. Most malignant tumors present the Warburg effect, which consists in increasing glycolytic rates with production of lactate, even in the presence of oxygen. The reliance of glycolytic cancer cells on trans-plasma-membrane electron transport (TPMET) systems for their continued survival raises the question of their appropriateness as a target for anticancer drug development strategies. Considering the interesting findings that some anticancer drugs in clinical use are cytotoxic even without entering cells and can inhibit TPMET activity, we investigated whether redox enzyme modulation could be a potential mechanism of action of antitumor ruthenium complexes. The results from this study indicated that ruthenium complexes can inhibit lactate production and TPMET activity in a way dependent on the cancer cell aggressiveness and the concentration of the complex. Combination approaches that target cell metabolism (glycolytic inhibitors) as well as proliferation are needed to successfully cure cancer. This study supports the potential use of some of these ruthenium complexes as adjuvants of glycolytic inhibitors in the treatment of aggressive cancers.

Marginal effects of glucose, insulin and insulin-like growth factor on chemotherapy response in endothelial and colorectal cancer cells

Resistance to chemotherapy is a major clinical issue for patients with colorectal cancer. Obesity has been associated with a poorer outcome and is a possible mechanism of resistance. The aim of the present study was to investigate the effect of obesity-related factors on the cell response to standard chemotherapy in stromal and colorectal cancer cells. Viability was measured following the treatment of colorectal cancer cell lines (WiDr and SW620) and stromal cells (human microvascular endothelial cells) in vitro with 5-fluorouracil, irinotecan and oxaliplatin under obesity-related conditions [elevated levels of insulin, insulin-like growth factor-1 (IGF-1) and glucose] and compared with non-elevated conditions. Obesity-related conditions alone increased cell viability and in selected cases, accumulation of the transcription factor, hypoxia-inducible factor-1. However, these conditions did not consistently increase resistance to the chemotherapy agents tested. The combination of IGF-1 and extremely low-dose chemotherapy significantly induced cell viability in WiDr colorectal cancer cells. These in vitro results may have clinical importance in an environment of increasing rates of obesity and colorectal cancer, and the frequent under-dosing of obese cancer patients.

Tumor initiating cells and chemoresistance: which is the best strategy to target colon cancer stem cells?

There is an emerging body of evidence that chemoresistance and minimal residual disease result from selective resistance of a cell subpopulation from the original tumor that is molecularly and phenotypically distinct. These cells are called “cancer stem cells” (CSCs). In this review, we analyze the potential targeting strategies for eradicating CSCs specifically in order to develop more effective therapeutic strategies for metastatic colon cancer. These include induction of terminal epithelial differentiation of CSCs or targeting some genes expressed only in CSCs and involved in self-renewal and chemoresistance. Ideal targets could be cell regulators that simultaneously control the stemness and the resistance of CSCs. Another important aspect of cancer biology, which can also be harnessed to create novel broad-spectrum anticancer agents, is the Warburg effect, also known as aerobic glycolysis. Actually, little is yet known with regard to the metabolism of CSCs population, leaving an exciting unstudied avenue in the dawn of the emerging field of metabolomics.

Hypoxia and metabolism in cancer

Interest in targeting metabolism has been renewed in recent years as research increases understanding of the altered metabolic profile of tumor cells compared with that of normal cells. Metabolic reprogramming allows cancer cells to survive and proliferate in the hostile tumor microenvironment. These metabolic changes support energy generation, anabolic processes, and the maintenance of redox potential, mechanisms that are all essential for the proliferation and survival of tumor cells. The metabolic switch in a number of key metabolic pathways is mainly regulated by genetic events, rendering cancer cells addicted to certain nutrients, such as glutamine. In addition, hypoxia is induced when highly proliferative tumor cells distance themselves from an oxygen supply. Hypoxia-inducible factor 1α is largely responsible for alterations in metabolism that support the survival of hypoxic tumor cells. Metabolic alterations and dependencies of cancer cells may be exploited to improve anticancer therapy. This chapter reviews the main aspects of altered metabolism in cancer cells, emphasizing recent advances in glucose, glutamine, and lipid metabolism.

Reciprocal regulation of HIF-1α and lincRNA-p21 modulates the Warburg effect

Hypoxia has long been linked to the Warburg effect, yet the underlying mechanism remains largely unclear. It is also not known if lncRNAs are involved in the contribution of hypoxia to the Warburg effect. Here we show that lincRNA-p21 is a hypoxia-responsive lncRNA and is essential for hypoxia-enhanced glycolysis. Hypoxia/HIF-1α-induced lincRNA-p21 is able to bind HIF-1α and VHL and thus disrupts the VHL-HIF-1α interaction. This disassociation attenuates VHL-mediated HIF-1α ubiquitination and causes HIF-1α accumulation. These data indicate the existence of a positive feedback loop between HIF-1α and lincRNA-p21 that promotes glycolysis under hypoxia. The ability of lincRNA-p21 to promote tumor growth is validated in mouse xenograft models. Together, these findings suggest that lincRNA-p21 is an important player in the regulation of the Warburg effect and also implicate lincRNA-p21 as a valuable therapeutic target for cancer.