Identification of ATP citrate lyase as a positive regulator of glycolytic function in glioblastomas

Metabolic dysregulation of tricarboxylic acid cycle and oxidative phosphorylation in glioblastoma

Glioblastoma multiforme (GBM) exhibits genetic alterations that induce the deregulation of oncogenic pathways, thus promoting metabolic adaptation. The modulation of metabolic enzyme activities is necessary to generate nucleotides, amino acids, and fatty acids, which provide energy and metabolic intermediates essential for fulfilling the biosynthetic needs of glioma cells. Moreover, the TCA cycle produces intermediates that play important roles in the metabolism of glucose, fatty acids, or non-essential amino acids, and act as signaling molecules associated with the activation of oncogenic pathways, transcriptional changes, and epigenetic modifications. In this review, we aim to explore how dysregulated metabolic enzymes from the TCA cycle and oxidative phosphorylation, along with their metabolites, modulate both catabolic and anabolic metabolic pathways, as well as pro-oncogenic signaling pathways, transcriptional changes, and epigenetic modifications in GBM cells, contributing to the formation, survival, growth, and invasion of glioma cells. Additionally, we discuss promising therapeutic strategies targeting key players in metabolic regulation. Therefore, understanding metabolic reprogramming is necessary to fully comprehend the biology of malignant gliomas and significantly improve patient survival.

Targeting of REST with rationally-designed small molecule compounds exhibits synergetic therapeutic potential in human glioblastoma cells

BACKGROUND

Glioblastoma (GBM) is an aggressive brain cancer associated with poor prognosis, intrinsic heterogeneity, plasticity, and therapy resistance. In some GBMs, cell proliferation is fueled by a transcriptional regulator, repressor element-1 silencing transcription factor (REST).

RESULTS

Using CRISPR/Cas9, we identified GBM cell lines dependent on REST activity. We developed new small molecule inhibitory compounds targeting small C-terminal domain phosphatase 1 (SCP1) to reduce REST protein level and transcriptional activity in glioblastoma cells. Top leads of the series like GR-28 exhibit potent cytotoxicity, reduce REST protein level, and suppress its transcriptional activity. Upon the loss of REST protein, GBM cells can potentially compensate by rewiring fatty acid metabolism, enabling continued proliferation. Combining REST inhibition with the blockade of this compensatory adaptation using long-chain acyl-CoA synthetase inhibitor Triacsin C demonstrated substantial synergetic potential without inducing hepatotoxicity.

CONCLUSIONS

Our results highlight the efficacy and selectivity of targeting REST alone or in combination as a therapeutic strategy to combat high-REST GBM.

ATP Citrate Lyase is a General Tumour Biomarker and Contributes to the Development of Cutaneous Squamous Cell Carcinoma

ATP citrate lyase, the first rate-limiting enzyme in de novo lipogenesis, plays a crucial role in tumour progression. This study explores ATP citrate lyase's potential as a tumour biomarker and its role in cutaneous squamous cell carcinoma. ATP citrate lyase expression patterns were analysed using TCGA and TIMER databases, and patient skin specimens were collected for immunohistochemistry to determine ATP citrate lyase levels. Cell proliferation, cell cycle, apoptosis, and c-Myc expression were assessed in A431 and SCL-1 cells. Stable cell lines with reduced ATP citrate lyase expression were obtained and subcutaneously implanted into nude mice to evaluate in vivo tumour growth. Ki67, c-Myc expression and TUNEL staining were analysed in subcutaneous tumours. ATP citrate lyase exhibited upregulation in various tumours, and showed significant associations with prognosis and immune infiltrate. Moreover, ATP citrate lyase was highly expressed in cutaneous squamous cell carcinoma. After ATP citrate lyase silencing, cutaneous squamous cell carcinoma cell growth decelerated, the cell cycle halted, cell apoptosis increased, and c-Myc expression decreased. Animal experiments revealed that, following ATP citrate lyase knockdown, tumour tissue growth slowed down, and there was a reduction in Ki-67 and c-Myc expression, accompanied by enhanced TUNEL staining. In conclusion, ATP citrate lyase may serve as a tumour biomarker. It is highly expressed in cutaneous squamous cell carcinoma and may serve as a therapeutic target.

SIRT2-mediated deacetylation of ACLY promotes the progression of oesophageal squamous cell carcinoma

ATP citrate lyase (ACLY), as a key enzyme in lipid metabolism, plays an important role in energy metabolism and lipid biosynthesis of a variety of tumours. Many studies have shown that ACLY is highly expressed in various tumours, and its pharmacological or gene inhibition significantly inhibits tumour growth and progression. However, the roles of ACLY in oesophageal squamous cell carcinoma (ESCC) remain unclear. Here, our data showed that ACLY inhibitor significantly attenuated cell proliferation, migration, invasion and lipid synthesis in different ESCC cell lines, whereas the proliferation, migration, invasion and lipid synthesis of ESCC cells were enhanced after ACLY overexpression. Furthermore, ACLY inhibitor dramatically suppressed tumour growth and lipid metabolism in ESCC cells xenografted tumour model, whereas ACLY overexpression displayed the opposite effect. Mechanistically, ACLY protein harboured acetylated modification and interacted with SIRT2 protein in ESCC cells. The SIRT2 inhibitor AGK2 significantly increased the acetylation level of ACLY protein and inhibited the proliferation and migration of ESCC cells, while overexpression of ACLY partially reversed the inhibitory effect of AGK2 on ESCC cells. Overall, these results suggest that targeting the SIRT2/ACLY signalling axis may be a potential therapeutic strategy for ESCC patients.

Emerging Lipid Targets in Glioblastoma

GBM accounts for most of the fatal brain cancer cases, making it one of the deadliest tumor types. GBM is characterized by severe progression and poor prognosis with a short survival upon conventional chemo- and radiotherapy. In order to improve therapeutic efficiency, considerable efforts have been made to target various features of GBM. One of the targetable features of GBM is the rewired lipid metabolism that contributes to the tumor's aggressive growth and penetration into the surrounding brain tissue. Lipid reprogramming allows GBM to acquire survival, proliferation, and invasion benefits as well as supportive modulation of the tumor microenvironment. Several attempts have been made to find novel therapeutic approaches by exploiting the lipid metabolic reprogramming in GBM. In recent studies, various components of de novo lipogenesis, fatty acid oxidation, lipid uptake, and prostaglandin synthesis have been considered promising targets in GBM. Emerging data also suggest a significant role hence therapeutic potential of the endocannabinoid metabolic pathway in GBM. Here we review the lipid-related GBM characteristics in detail and highlight specific targets with their potential therapeutic use in novel antitumor approaches.

Role of Glycolytic and Glutamine Metabolism Reprogramming on the Proliferation, Invasion, and Apoptosis Resistance through Modulation of Signaling Pathways in Glioblastoma

Glioma cells exhibit genetic and metabolic alterations that affect the deregulation of several cellular signal transduction pathways, including those related to glucose metabolism. Moreover, oncogenic signaling pathways induce the expression of metabolic genes, increasing the metabolic enzyme activities and thus the critical biosynthetic pathways to generate nucleotides, amino acids, and fatty acids, which provide energy and metabolic intermediates that are essential to accomplish the biosynthetic needs of glioma cells. In this review, we aim to explore how dysregulated metabolic enzymes and their metabolites from primary metabolism pathways in glioblastoma (GBM) such as glycolysis and glutaminolysis modulate anabolic and catabolic metabolic pathways as well as pro-oncogenic signaling and contribute to the formation, survival, growth, and malignancy of glioma cells. Also, we discuss promising therapeutic strategies by targeting the key players in metabolic regulation. Therefore, the knowledge of metabolic reprogramming is necessary to fully understand the biology of malignant gliomas to improve patient survival significantly.

Acetyl-CoA metabolism as a therapeutic target for cancer

Acetyl-coenzyme A (acetyl-CoA), an essential metabolite, not only takes part in numerous intracellular metabolic processes, powers the tricarboxylic acid cycle, serves as a key hub for the biosynthesis of fatty acids and isoprenoids, but also serves as a signaling substrate for acetylation reactions in post-translational modification of proteins, which is crucial for the epigenetic inheritance of cells. Acetyl-CoA links lipid metabolism with histone acetylation to create a more intricate regulatory system that affects the growth, aggressiveness, and drug resistance of malignancies such as glioblastoma, breast cancer, and hepatocellular carcinoma. These fascinating advances in the knowledge of acetyl-CoA metabolism during carcinogenesis and normal physiology have raised interest regarding its modulation in malignancies. In this review, we provide an overview of the regulation and cancer relevance of main metabolic pathways in which acetyl-CoA participates. We also summarize the role of acetyl-CoA in the metabolic reprogramming and stress regulation of cancer cells, as well as medical application of inhibitors targeting its dysregulation in therapeutic intervention of cancers.

Lipid metabolism reprogramming in head and neck cancer

Lipid metabolism reprogramming is one of the most prominent metabolic anomalies in cancer, wherein cancer cells undergo dysregulation of lipid metabolism to acquire adequate energy, cell membrane building blocks, as well as signaling molecules essential for cell proliferation, survival, invasion, and metastasis. These adaptations enable cancer cells to effectively respond to challenges posed by the tumor microenvironment, leading to cancer therapy resistance and poor cancer prognosis. Head and neck cancer, ranking as the seventh most prevalent cancer, exhibits numerous abnormalities in lipid metabolism. Nevertheless, the precise role of lipid metabolic rewiring in head and neck cancer remains unclear. In line with the LIPID MAPS Lipid Classification System and cancer risk factors, the present review delves into the dysregulated molecules and pathways participating in the process of lipid uptake, biosynthesis, transportation, and catabolism. We also present an overview of the latest advancements in understanding alterations in lipid metabolism and how they intersect with the carcinogenesis, development, treatment, and prognosis of head and neck cancer. By shedding light on the significance of metabolic therapy, we aspire to improve the overall prognosis and treatment outcomes of head and neck cancer patients.

Allosteric role of the citrate synthase homology domain of ATP citrate lyase

ATP citrate lyase (ACLY) is the predominant nucleocytosolic source of acetyl-CoA and is aberrantly regulated in many diseases making it an attractive therapeutic target. Structural studies of ACLY reveal a central homotetrameric core citrate synthase homology (CSH) module flanked by acyl-CoA synthetase homology (ASH) domains, with ATP and citrate binding the ASH domain and CoA binding the ASH-CSH interface to produce acetyl-CoA and oxaloacetate products. The specific catalytic role of the CSH module and an essential D1026A residue contained within it has been a matter of debate. Here, we report biochemical and structural analysis of an ACLY-D1026A mutant demonstrating that this mutant traps a (3S)-citryl-CoA intermediate in the ASH domain in a configuration that is incompatible with the formation of acetyl-CoA, is able to convert acetyl-CoA and OAA to (3S)-citryl-CoA in the ASH domain, and can load CoA and unload acetyl-CoA in the CSH module. Together, this data support an allosteric role for the CSH module in ACLY catalysis.

Mitochondrial uncoupler DNP induces coexistence of dual-state hyper-energy metabolism leading to tumor growth advantage in human glioma xenografts

Introduction

Cancer bioenergetics is an essential hallmark of neoplastic transformation. Warburg postulated that mitochondrial OXPHOS is impaired in cancer cells, leading to aerobic glycolysis as the primary metabolic pathway. However, mitochondrial function is altered but not entirely compromised in most malignancies, and that mitochondrial uncoupling is known to increase the carcinogenic potential and modifies treatment response by altering metabolic reprogramming. Our earlier study showed that transient DNP exposure increases glycolysis in human glioma cells (BMG-1). The current study investigated the persistent effect of DNP on the energy metabolism of BMG-1 cells and its influence on tumor progression in glioma xenografts.

Methods

BMG-1 cells were treated with 2,4-dinitrophenol (DNP) in-vitro, to establish the OXPHOS-modified (OPM-BMG) cells. Further cellular metabolic characterization was carried out in both in-vitro cellular model and in-vivo tumor xenografts to dissect the role of metabolic adaptation in these cells and compared them with their parental phenotype.

Results and Discussion

Chronic exposure to DNP in BMG-1 cells resulted in dual-state hyper-energy metabolism with elevated glycolysis⁺⁺ and OXPHOS⁺⁺ compared to parental BMG-1 cells with low glycolysis⁺ and OXPHOS⁺. Tumor xenograft of OPM-BMG cells showed relatively increased tumor-forming potential and accelerated tumor growth in nude mice. Moreover, compared to BMG-1, OPM-BMG tumor-derived cells also showed enhanced migration and invasion potential. Although mitochondrial uncouplers are proposed as a valuable anti-cancer strategy; however, our findings reveal that prolonged exposure to uncouplers provides tumor growth advantage over the existing glioma phenotype that may lead to poor clinical outcomes.

An Update on the Metabolic Landscape of Oncogenic Viruses

Viruses play an important role in cancer development as about 12% of cancer types are linked to viral infections. Viruses that induce cellular transformation are known as oncoviruses. Although the mechanisms of viral oncogenesis differ between viruses, all oncogenic viruses share the ability to establish persistent chronic infections with no obvious symptoms for years. During these prolonged infections, oncogenic viruses manipulate cell signaling pathways that control cell cycle progression, apoptosis, inflammation, and metabolism. Importantly, it seems that most oncoviruses depend on these changes for their persistence and amplification. Metabolic changes induced by oncoviruses share many common features with cancer metabolism. Indeed, viruses, like proliferating cancer cells, require increased biosynthetic precursors for virion production, need to balance cellular redox homeostasis, and need to ensure host cell survival in a given tissue microenvironment. Thus, like for cancer cells, viral replication and persistence of infected cells frequently depend on metabolic changes. Here, we draw parallels between metabolic changes observed in cancers or induced by oncoviruses, with a focus on pathways involved in the regulation of glucose, lipid, and amino acids. We describe whether and how oncoviruses depend on metabolic changes, with the perspective of targeting them for antiviral and onco-therapeutic approaches in the context of viral infections.

Metabolic Pathways, Enzymes, and Metabolites: Opportunities in Cancer Therapy

Metabolic reprogramming enables cancer cells to proliferate and produce tumor biomass under a nutrient-deficient microenvironment and the stress of metabolic waste. A cancer cell adeptly undergoes a variety of adaptations in metabolic pathways and differential expression of metabolic enzyme genes. Metabolic adaptation is mainly determined by the physiological demands of the cancer cell of origin and the host tissue. Numerous metabolic regulators that assist cancer cell proliferation include uncontrolled anabolism/catabolism of glucose metabolism, fatty acids, amino acids metabolism, nucleotide metabolism, tumor suppressor genes, microRNAs, and many regulatory enzymes and genes. Using this paradigm, we review the current understanding of metabolic reprogramming in tumors and discuss the new strategies of cancer metabolomics that can be tapped into for cancer therapeutics.

ARHGEF3 regulates the stability of ACLY to promote the proliferation of lung cancer

Rho GTPases play an essential role in many cellular processes, including cell cycle progress, cell motility, invasion, migration, and transformation. Several studies indicated that the dysregulation of Rho GTPase signaling is closely related to tumorigenesis. Rho GEFs considered being positive regulators of Rho GTPase, promoting the dissociation of Rho protein from GDP and binding to GTP, thus activating the downstream signaling pathway. Herein, we demonstrated that ARHGEF3, a member of the Rho GEFs family, played an important role in non-small cell lung cancer (NSCLC). We found that ARHGEF3 was highly expressed in non-small cell lung cancer and facilitated cancer cell proliferation of NSCLC cells in vitro and in vivo. Further studies demonstrated that ARHGEF3 enhanced the protein homeostasis of ATP-citrate lyase (ACLY) by reducing its acetylation on Lys17 and Lys86, leading to the dissociation between ACLY and its E3 ligase-NEDD4. Interestingly, this function of ARHGEF3 on the protein homeostasis of ACLY was independent of its GEF activity. Taken together, our findings uncover a novel function of ARHGEF3, suggesting that ARHGEF3 is a promising therapeutic target in non-small cell lung cancer.

Identification of ENO1 as a prognostic biomarker and molecular target among ENOs in bladder cancer

Background

Enolase is an essential enzyme in the process of glycolysis and has been implicated in cancer progression. Though dysregulation of ENOs has been reported in multiple cancers, their prognostic value and specific role in bladder cancer (BLCA) remain unclear.

Methods

Multiple databases were employed to examine the expression of ENOs in BLCA. The expression of ENO1 was also validated in BLCA cell lines and tissue samples by western blotting and immunohistochemistry. Kaplan–Meier analysis, ROC curve, univariate and multivariate Cox regression were performed to evaluate the predictive capability of the ENO1. Gene ontology (GO) and Gene Set Enrichment Analyses (GSEA) analysis were employed to perform the biological processes enrichment. Function experiments were performed to explore the biological role of ENO1 in BLCA. The correlation of ENO1 with immune cell infiltration was explored by CIBERSORT.

Results

By analyzing three ENO isoforms in multiple databases, we identified that ENO1 was the only significantly upregulated gene in BLCA. High expression level of ENO1 was further confirmed in BLCA tissue samples. Aberrant ENO1 overexpression was associated with clinicopathological characteristics and unfavorable prognosis. Functional studies demonstrated that ENO1 depletion inhibited cancer cell aggressiveness. Furthermore, the expression level of ENO1 was correlated with the infiltration levels of immune cells and immune-related functions.

Conclusions

Taken together, our results indicated that ENO1 might serve as a promising prognostic biomarker for prognosticating prognosis associated with the tumor immune microenvironment, suggesting that ENO1 could be a potential immune-related target against BLCA.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12967-022-03509-1.

Novel Insights on Lipid Metabolism Alterations in Drug Resistance in Cancer

Chemotherapy is one of the primary treatments for most human cancers. Despite great progress in cancer therapeutics, chemotherapy continues to be important for improving the survival of cancer patients, especially for those who has unresectable metastatic tumors or fail to respond to immunotherapy. However, intrinsic or acquired chemoresistance results in tumor recurrence, which remains a major obstacle in anti-cancer treatment. The high prevalence of chemoresistant cancer makes it urgent to deepen our understanding on chemoresistance mechanisms and to develop novel therapeutic strategies. Multiple mechanisms, including drug efflux, enhanced DNA damage reparability, increased detoxifying enzymes levels, presence of cancer stem cells (CSCs), epithelial mesenchymal transition (EMT), autophagy, ferroptosis and resistance to apoptosis, underlie the development of chemoresistance. Recently, accumulating evidence suggests that lipid metabolism alteration is closely related to drug resistance in tumor. Targeting lipid metabolism in combination with traditional chemotherapeutic drugs is a promising strategy to overcome drug resistance. Therefore, this review compiles the current knowledge about aberrant lipid metabolism in chemoresistant cancer, mainly focusing on aberrant fatty acid metabolism, and presents novel therapeutic strategies targeting altered lipid metabolism to overcome chemoresistance in cancer.

Lipid metabolism in cancer progression and therapeutic strategies

Dysregulated lipid metabolism represents an important metabolic alteration in cancer. Fatty acids, cholesterol, and phospholipid are the three most prevalent lipids that act as energy producers, signaling molecules, and source material for the biogenesis of cell membranes. The enhanced synthesis, storage, and uptake of lipids contribute to cancer progression. The rewiring of lipid metabolism in cancer has been linked to the activation of oncogenic signaling pathways and cross talk with the tumor microenvironment. The resulting activity favors the survival and proliferation of tumor cells in the harsh conditions within the tumor. Lipid metabolism also plays a vital role in tumor immunogenicity via effects on the function of the noncancer cells within the tumor microenvironment, especially immune‐associated cells. Targeting altered lipid metabolism pathways has shown potential as a promising anticancer therapy. Here, we review recent evidence implicating the contribution of lipid metabolic reprogramming in cancer to cancer progression, and discuss the molecular mechanisms underlying lipid metabolism rewiring in cancer, and potential therapeutic strategies directed toward lipid metabolism in cancer. This review sheds new light to fully understanding of the role of lipid metabolic reprogramming in the context of cancer and provides valuable clues on therapeutic strategies targeting lipid metabolism in cancer.

Biomarker identification and pathway analysis of rheumatoid arthritis based on metabolomics in combination with ingenuity pathway analysis

Rheumatoid arthritis (RA) is a common autoimmune and inflammatory disease worldwide, but understanding its pathogenesis is still limited. In this study, plasma untargeted metabolomics of a discovery cohort and targeted analysis of a verification cohort were performed by gas chromatograph mass spectrometry (GC/MS). Univariate and multivariate statistical analysis were utilized to reveal differential metabolites, followed by the construction of biomarker panel through random forest (RF) algorithm. The pathways involved in RA were enriched by differential metabolites using Ingenuity Pathway Analysis (IPA) suite. Untargeted metabolomics revealed eighteen significantly altered metabolites in RA. Among these metabolites, a three-metabolite marker panel consisting of L-cysteine, citric acid and L-glutamine was constructed, using random forest algorithm that could predict RA with high accuracy, sensitivity and specificity based on a multivariate exploratory receiver operator characteristic (ROC) curve analysis. The panel was further validated by support vector machine (SVM) and partial least squares discriminant analysis (PLS-DA) algorithms, and also verified with targeted metabolomics using a verification cohort. Additionally, the dysregulated taurine biosynthesis pathway in RA was revealed by an integrated analysis of metabolomics and transcriptomics. Our findings in this study not only provided a mechanism underlying RA pathogenesis, but also offered alternative therapeutic targets for RA.

Regulation and metabolic functions of mTORC1 and mTORC2

Cells metabolize nutrients for biosynthetic and bioenergetic needs to fuel growth and proliferation. The uptake of nutrients from the environment and their intracellular metabolism is a highly controlled process that involves cross talk between growth signaling and metabolic pathways. Despite constant fluctuations in nutrient availability and environmental signals, normal cells restore metabolic homeostasis to maintain cellular functions and prevent disease. A central signaling molecule that integrates growth with metabolism is the mechanistic target of rapamycin (mTOR). mTOR is a protein kinase that responds to levels of nutrients and growth signals. mTOR forms two protein complexes, mTORC1, which is sensitive to rapamycin, and mTORC2, which is not directly inhibited by this drug. Rapamycin has facilitated the discovery of the various functions of mTORC1 in metabolism. Genetic models that disrupt either mTORC1 or mTORC2 have expanded our knowledge of their cellular, tissue, as well as systemic functions in metabolism. Nevertheless, our knowledge of the regulation and functions of mTORC2, particularly in metabolism, has lagged behind. Since mTOR is an important target for cancer, aging, and other metabolism-related pathologies, understanding the distinct and overlapping regulation and functions of the two mTOR complexes is vital for the development of more effective therapeutic strategies. This review discusses the key discoveries and recent findings on the regulation and metabolic functions of the mTOR complexes. We highlight findings from cancer models but also discuss other examples of the mTOR-mediated metabolic reprogramming occurring in stem and immune cells, type 2 diabetes/obesity, neurodegenerative disorders, and aging.

ATP citrate lyase inhibitor triggers endoplasmic reticulum stress to induce hepatocellular carcinoma cell apoptosis via p-eIF2α/ATF4/CHOP axis

ATP citrate lyase (ACLY), a key enzyme in the metabolic reprogramming of many cancers, is widely expressed in various mammalian tissues. This study aimed to evaluate the effects and mechanisms of ACLY and its inhibitor BMS-303141 on hepatocellular carcinoma (HCC). In this study, ACLY was highly expressed in HCC tissues, especially in HepG2 and Huh7 cells, but was down-regulated in Hep3B and HCC-LM3 cells. Besides, ACLY knockdown inhibited HepG2 proliferation and clone formation, while opposite result was noticed in HCC-LM3 cells with ACLY overexpression. Moreover, ACLY knockdown impeded the migration and invasion abilities of HepG2 cells. Similarly, BMS-303141 suppressed HepG2 and Huh-7 cell proliferation. The p-eIF2α, ATF4, CHOP p-IRE1α, sXBP1 and p-PERK were activated in HepG2 cells stimulated by BMS-303141. In cells where ER stress was induced, ATF4 was involved in BMS-303141-mediated cell death procession, and ATF4 knockdown reduced HCC cell apoptosis stimulated by BMS-303141. In a mouse xenograft model, combined treatment with BMS-303141 and sorafenib reduced HepG2 tumour volume and weight. In addition, ACLY expression was associated with HCC metastasis and tumour-node-metastases staging. Survival analysis and Cox proportional hazards regression model showed that overall survival was lower in HCC patients with high ACLY expression; AFP level, TNM staging, tumour size and ACLY expression level were independent risk factors affecting their overall survival. In conclusion, ACLY might represent a promising target in which BMS-303141 could induce ER stress and activate p-eIF2α/ATF4/CHOP axis to promote apoptosis of HCC cells, and synergized with sorafenib to enhance the efficacy of HCC treatment.

The Role of a Proprotein Convertase Inhibitor in Reactivation of Tumor-Associated Macrophages and Inhibition of Glioma Growth

Tumors are characterized by the presence of malignant and non-malignant cells, such as immune cells including macrophages, which are preponderant. Macrophages impact the efficacy of chemotherapy and may lead to drug resistance. In this context and based on our previous work, we investigated the ability to reactivate macrophages by using a proprotein convertases inhibitor. Proprotein convertases process immature proteins into functional proteins, with several of them having a role in immune cell activation and tumorigenesis. Macrophages were treated with a peptidomimetic inhibitor targeting furin, PC1/3, PC4, PACE4, and PC5/6. Their anti-glioma activity was analyzed by mass spectrometry-based proteomics and viability assays in 2D and 3D in vitro cultures. Comparison with temozolomide, the drug used for glioma therapy, established that the inhibitor was more efficient for the reduction of cancer cell density. The inhibitor was also able to reactivate macrophages through the secretion of several immune factors with antitumor properties. Moreover, two proteins considered as good glioma patient survival indicators were also identified in 3D cultures treated with the inhibitor. Finally, we established that the proprotein convertases inhibitor has a dual role as an anti-glioma drug and anti-tumoral macrophage reactivation drug. This strategy could be used together with chemotherapy to increase therapy efficacy in glioma.

Suppressed "Warburg Effect" in Nasopharyngeal Carcinoma Via the Inhibition of Pyruvate Kinase Type M2-Mediated Energy Generation Pathway

Warburg effect describes the abnormal energy metabolism in cancer cells and pyruvate kinase type M2 is involved in the regulation of this effect. In the current study, the role of pyruvate kinase type M2 in the initiation of Warburg effect in nasopharyngeal carcinoma cells was explored. The expression status of pyruvate kinase type M2 was detected in nasopharyngeal carcinoma samples and analyzed by different clinicopathological characteristics. Then the level of pyruvate kinase type M2 was suppressed in 2 nasopharyngeal carcinoma cell lines. The effects of pyruvate kinase type M2 inhibition on cell viability, apoptosis, invasion, glucose uptake, ATP generation, and glycolysis metabolism were determined. The data showed that the high expression of pyruvate kinase type M2 in nasopharyngeal carcinoma tissues was associated with the larger tumor size and advanced metastasis in the patients. The inhibition of pyruvate kinase type M2 resulted in the repressed proliferation and invasion in nasopharyngeal carcinoma cells, along with the increased apoptotic rate. The lack of pyruvate kinase type M2 function inhibited glucose uptake, while increased ATP generation in nasopharyngeal carcinoma cells. Moreover, the production of glycolysis metabolites, including pyruvic acid, lactate, citrate, and malate, was also suppressed by pyruvate kinase type M2 inhibition. At molecular level, the expressions of glucose transporter and hexokinase 2 were downregulated by pyruvate kinase type M2 inhibition, confirming the changes in glucose metabolism. Collectively, the current study demonstrated that the function of pyruvate kinase type M2 was important to maintain the proliferation and invasion of nasopharyngeal carcinoma cells, and the inhibition of the factor would antagonize nasopharyngeal carcinoma by blocking Warburg effect.

Altered cellular metabolism in gliomas - an emerging landscape of actionable co-dependency targets

Altered cellular metabolism is a hallmark of gliomas. Propelled by a set of recent technological advances, new insights into the molecular mechanisms underlying glioma metabolism are rapidly emerging. In this Review, we focus on the dynamic nature of glioma metabolism and how it is shaped by the interaction between tumour genotype and brain microenvironment. Recent advances integrating metabolomics with genomics are discussed, yielding new insight into the mechanisms that drive glioma pathogenesis. Studies that shed light on interactions between the tumour microenvironment and tumour genotype are highlighted, providing important clues as to how gliomas respond to and adapt to their changing tissue and biochemical contexts. Finally, a road map for the discovery of potential new glioma drug targets is suggested, with the goal of translating these new insights about glioma metabolism into clinical benefits for patients.

The vital role of ATP citrate lyase in chronic diseases

Chronic or non-communicable diseases are the leading cause of death worldwide; they usually result in long-term illnesses and demand long-term care. Despite advances in molecular therapeutics, specific biomarkers and targets for the treatment of these diseases are required. The dysregulation of de novo lipogenesis has been found to play an essential role in cell metabolism and is associated with the development and progression of many chronic diseases; this confirms the link between obesity and various chronic diseases. The main enzyme in this pathway-ATP-citrate lyase (ACLY), a lipogenic enzyme-catalyzes the critical reaction linking cellular glucose catabolism and lipogenesis. Increasing lines of evidence suggest that the modulation of ACLY expression correlates with the development and progressions of various chronic diseases such as neurodegenerative diseases, cardiovascular diseases, diabetes, obesity, inflammation, and cancer. Recent studies suggest that the inhibition of ACLY activity modulates the glycolysis and lipogenesis processes and stimulates normal physiological functions. This comprehensive review aimed to critically evaluate the role of ACLY in the development and progression of different diseases and the effects of its downregulation in the prevention and treatment of these diseases.

Heat Shock Proteins in Glioblastoma Biology: Where Do We Stand?

Heat shock proteins (HSPs) are evolutionary conserved proteins that work as molecular chaperones and perform broad and crucial roles in proteostasis, an important process to preserve the integrity of proteins in different cell types, in health and disease. Their function in cancer is an important aspect to be considered for a better understanding of disease development and progression. Glioblastoma (GBM) is the most frequent and lethal brain cancer, with no effective therapies. In recent years, HSPs have been considered as possible targets for GBM therapy due their importance in different mechanisms that govern GBM malignance. In this review, we address current evidence on the role of several HSPs in the biology of GBMs, and how these molecules have been considered in different treatments in the context of this disease, including their activities in glioblastoma stem-like cells (GSCs), a small subpopulation able to drive GBM growth. Additionally, we highlight recent works that approach other classes of chaperones, such as histone and mitochondrial chaperones, as important molecules for GBM aggressiveness. Herein, we provide new insights into how HSPs and their partners play pivotal roles in GBM biology and may open new therapeutic avenues for GBM based on proteostasis machinery.

Glycolytic Switch Is Required for Transdifferentiation to Endothelial Lineage

BACKGROUND

We have previously shown that activation of cell-autonomous innate immune signaling facilitates the transdifferentiation of fibroblasts into induced endothelial cells, and is required to generate induced endothelial cells with high fidelity for endothelial lineage. Recent studies indicate that a glycolytic switch plays a role in induced pluripotent stem cell generation from somatic cells.

METHODS

Seahorse and metabolomics flux assays were used to measure the metabolic changes during transdifferentiation in vitro, and Matrigel plug assay was used to assess the effects of glycolysis modulators on transdifferentiation in vivo.

RESULTS

The metabolic switch begins rapidly after activation of innate immunity, before the expression of markers of endothelial lineage. Inhibiting glycolysis impaired, whereas facilitating glycolysis enhanced, the generation of induced endothelial cells. The toll-like receptor 3 agonist poly I:C increased expression of the mitochondrial citrate transporter Slc25A1, and the nuclear ATP-citrate lyase, in association with intracellular accumulation of citrate, the precursor for acetyl coenzyme A. These metabolic changes were coordinated with increased histone acetylation during transdifferentiation.

CONCLUSION

Innate immune signaling promotes a glycolytic switch that is required for transdifferentiation, both processes being attenuated by ATP-citrate lyase knockdown. These data shed light on a novel link between metabolism and epigenetic modulation in transdifferentiation.

Causes and Consequences of A Glutamine Induced Normoxic HIF1 Activity for the Tumor Metabolism

The transcription factor hypoxia-inducible factor 1 (HIF1) is the crucial regulator of genes that are involved in metabolism under hypoxic conditions, but information regarding the transcriptional activity of HIF1 in normoxic metabolism is limited. Different tumor cells were treated under normoxic and hypoxic conditions with various drugs that affect cellular metabolism. HIF1α was silenced by siRNA in normoxic/hypoxic tumor cells, before RNA sequencing and bioinformatics analyses were performed while using the breast cancer cell line MDA-MB-231 as a model. Differentially expressed genes were further analyzed and validated by qPCR, while the activity of the metabolites was determined by enzyme assays. Under normoxic conditions, HIF1 activity was significantly increased by (i) glutamine metabolism, which was associated with the release of ammonium, and it was decreased by (ii) acetylation via acetyl CoA synthetase (ACSS2) or ATP citrate lyase (ACLY), respectively, and (iii) the presence of L-ascorbic acid, citrate, or acetyl-CoA. Interestingly, acetylsalicylic acid, ibuprofen, L-ascorbic acid, and citrate each significantly destabilized HIF1α only under normoxia. The results from the deep sequence analyses indicated that, in HIF1-siRNA silenced MDA-MB-231 cells, 231 genes under normoxia and 1384 genes under hypoxia were transcriptionally significant deregulated in a HIF1-dependent manner. Focusing on glycolysis genes, it was confirmed that HIF1 significantly regulated six normoxic and 16 hypoxic glycolysis-associated gene transcripts. However, the results from the targeted metabolome analyses revealed that HIF1 activity affected neither the consumption of glucose nor the release of ammonium or lactate; however, it significantly inhibited the release of the amino acid alanine. This study comprehensively investigated, for the first time, how normoxic HIF1 is stabilized, and it analyzed the possible function of normoxic HIF1 in the transcriptome and metabolic processes of tumor cells in a breast cancer cell model. Furthermore, these data imply that HIF1 compensates for the metabolic outcomes of glutaminolysis and, subsequently, the Warburg effect might be a direct consequence of the altered amino acid metabolism in tumor cells.

Modeling Monogenic Diabetes using Human ESCs Reveals Developmental and Metabolic Deficiencies Caused by Mutations in HNF1A

Human monogenic diabetes, caused by mutations in genes involved in beta cell development and function, has been a challenge to study because multiple mouse models have not fully recapitulated the human disease. Here, we use genome edited human embryonic stem cells to understand the most common form of monogenic diabetes, MODY3, caused by mutations in the transcription factor HNF1A. We found that HNF1A is necessary to repress an alpha cell gene expression signature, maintain endocrine cell function, and regulate cellular metabolism. In addition, we identified the human-specific long non-coding RNA, LINKA, as an HNF1A target necessary for normal mitochondrial respiration. These findings provide a possible explanation for the species difference in disease phenotypes observed with HNF1A mutations and offer mechanistic insights into how the HNF1A gene may also influence type 2 diabetes.

Aberrant lipid metabolism as a therapeutic target in liver cancer

INTRODUCTION

Hepatocellular carcinoma (HCC) is one of the most common and lethal cancers. Progress has been made in treatment of HCC; however, improved outcomes are much needed. The increased metabolic needs of cancer cells underscore the importance of metabolic pathways in cancer cell survival. Lipid metabolism has a role in HCC development; aberrant overexpression of several key enzymes is seen in many solid human tumors. Areas covered: We discuss aberrant lipid metabolism and the promise of multiple targets, in particular related to HCC treatment. We searched PubMed and clinicaltrials.gov for published and unpublished studies from 2000 to 2019. These terms were used: lipids, fatty acid metabolism, lipid metabolism, liver cancer, HCC, de novo fatty acid synthesis, ATP citrate lyase, stearoyl CoA denaturase, fatty acid synthase, acetyl coenzyme A carboxylase, CD147, KLF4, monoglyceride lipase, AMP activated protein kinase. Expert opinion: The importance of dysregulation of fatty acid synthesis in cancer is a growing area of research. HCC demonstrates significant alteration in lipid metabolism, representing great potential as a target for novel therapeutics. Various agents have demonstrated promising anti-neoplastic activity. This strategy deserves further development for improved outcomes.

Epigenetic-Transcriptional Regulation of Fatty Acid Metabolism and Its Alterations in Leukaemia

In recent years fatty acid metabolism has gained greater attention in haematologic cancers such as acute myeloid leukaemia. The oxidation of fatty acids provides fuel in the form of ATP and NADH, while fatty acid synthesis provides building blocks for cellular structures. Here, we will discuss how leukaemic cells differ from healthy cells in their increased reliance on fatty acid metabolism. In order to understand how these changes are achieved, we describe the main pathways regulating fatty acid metabolism at the transcriptional level and highlight the limited knowledge about related epigenetic mechanisms. We explore these mechanisms in the context of leukaemia and consider the relevance of the bone marrow microenvironment in disease management. Finally, we discuss efforts to interfere with fatty acid metabolism as a therapeutic strategy along with the use of metabolic parameters as biomarkers.

[Small interfering RNA-mediated α-enolase knockdown suppresses glycolysis and proliferation of human glioma U251 cells in vitro]

OBJECTIVE

To investigate the role of α-enolase (ENO1) in regulating glucose metabolism and cell growth in human glioma cells.

METHODS

Glucose uptake and lactate generation were assessed to evaluate the changes in glucose metabolism in human glioma U251 cells with small interfering RNA (siRNA)-mediated ENO1 knockdown. MTT assay and 5-ethynyl-2'-deoxyuridine (EdU) staining were used to examine the cell growth and cell cycle changes following siRNA transfection of the cells.

RESULTS

Transfection of U251 cells with siRNA-ENO1 markedly reduced glucose uptake (P=0.023) and lactate generation (P=0.007) in the cells and resulted in significant suppression of cell proliferation (*P<0.05) since the second day following the transfection. Transfection with siRNA-ENO1 also obviously suppressed cell cycle G1/S transition in the cells (P=0.0425). The expressions of HK2 and LDHA, the marker genes for glucose metabolism, were significantly down-regulated in the cells with siRNA-mediated ENO1 knockdown.

CONCLUSION

ENO1 as a potential oncogene promotes glioma cell growth by positively modulating glucose metabolism.

Nutrient sensor O-GlcNAc transferase controls cancer lipid metabolism via SREBP-1 regulation

Elevated O-GlcNAcylation is associated with disease states such as diabetes and cancer. O-GlcNAc transferase (OGT) is elevated in multiple cancers and inhibition of this enzyme genetically or pharmacologically inhibits oncogenesis. Here we show that O-GlcNAcylation modulates lipid metabolism in cancer cells. OGT regulates expression of the master lipid regulator the transcription factor sterol regulatory element binding protein 1 (SREBP-1) and its transcriptional targets both in cancer and lipogenic tissue. OGT regulates SREBP-1 protein expression via AMP Activated protein kinase (AMPK). SREBP-1 is critical for OGT-mediated regulation of cell survival and of lipid synthesis, as overexpression of SREBP-1 rescues lipogenic defects associated with OGT suppression, and tumor growth in vitro and in vivo. These results unravel a previously unidentified link between O-GlcNAcylation, lipid metabolism and the regulation of SREBP-1 in cancer and suggests a crucial role for O-GlcNAc signaling in transducing nutritional state to regulate lipid metabolism.

Extracellular Proton Concentrations Impacts LN229 Glioblastoma Tumor Cell Fate via Differential Modulation of Surface Lipids

Background

Glioblastoma multiforme (GBM) is a highly aggressive form of brain cancer with marginal survival rates. GBM extracellular acidosis can profoundly impact its cell fate heterogeneities and progression. However, the molecules and mechanisms that enable GBM tumor cells acid adaptation and consequent cell fate competencies are weakly understood. Since extracellular proton concentrations (pHe) directly intercept the tumor cell plasma membrane, surface lipids must play a crucial role in pHe-dependent tumor cell fate dynamics. Hence, a more detailed insight into the finely tuned pH-dependent modulation of surface lipids is required to generate strategies that can inhibit or surpass tumor cell acid adaptation, thereby forcing the eradication of heterogeneous oncogenic niches, without affecting the normal cells.

Results

By using image-based single cell analysis and physicochemical techniques, we made a small-scale survey of the effects of pH ranges (physiological: pHe 7.4, low: 6.2, and very low: 3.4) on LN229 glioblastoma cell line surface remodeling and analyzed the consequent cell fate heterogeneities with relevant molecular targets and behavioral assays. Through this basic study, we uncovered that the extracellular proton concentration (1) modulates surface cholesterol-driven cell fate dynamics and (2) induces ‘differential clustering’ of surface resident GM3 glycosphingolipid which together coordinates the proliferation, migration, survival, and death reprogramming via distinct effects on the tumor cell biomechanical homeostasis. A novel synergy of anti-GM3 antibody and cyclophilin A inhibitor was found to mimic the very low pHe-mediated GM3 supraclustered conformation that elevated the surface rigidity and mechano-remodeled the tumor cell into a differentiated phenotype which eventually succumbed to the anoikis type of cell death, thereby eradicating the tumorigenic niches.

Conclusion and significance

This work presents an initial insight into the physicochemical capacities of extracellular protons in the generation of glioblastoma tumor cell heterogeneities and cell death via the crucial interplay of surface lipids and their conformational changes. Hence, monitoring of proton–cholesterol–GM3 correlations in vivo through diagnostic imaging and in vitro in clinical samples may assist better tumor staging and prognosis. The emerged insights have further led to the translation of a ‘pH-dependent mechanisms of oncogenesis control’ into the surface targeted anti-GBM therapeutics.

Targeting Lipid Metabolic Reprogramming as Anticancer Therapeutics

Cancer cells rewire their metabolism to satisfy the demands of growth and survival, and this metabolic reprogramming has been recognized as an emerging hallmark of cancer. Lipid metabolism is pivotal in cellular process that converts nutrients into energy, building blocks for membrane biogenesis and the generation of signaling molecules. Accumulating evidence suggests that cancer cells show alterations in different aspects of lipid metabolism. The changes in lipid metabolism of cancer cells can affect numerous cellular processes, including cell growth, proliferation, differentiation, and survival. The potential dependence of cancer cells on the deregulated lipid metabolism suggests that enzymes and regulating factors involved in this process are promising targets for cancer treatment. In this review, we focus on the features associated with the lipid metabolic pathways in cancer, and highlight recent advances on the therapeutic targets of specific lipid metabolic enzymes or regulating factors and target-directed small molecules that can be potentially used as anticancer drugs.

The Interconnections between Autophagy and Integrin-Mediated Cell Adhesion

Autophagy is a cellular degradation process integral for promoting cellular adaptation during metabolic stress while also functioning as a cellular homeostatic mechanism. Mounting evidence also demonstrates that autophagy is induced upon loss of integrin-mediated cell attachments to the surrounding extracellular matrix (ECM). Analogous to its established cytoprotective role during nutrient starvation, autophagy protects cells from detachment-induced cell death, termed anoikis. Here, we review the significance of autophagy as an anoikis resistance pathway, focusing on the intracellular signals associated with integrins that modulate the autophagy response and dictate the balance between cell death and survival following loss of cell-matrix contact. In addition, we highlight recent studies demonstrating that autophagy functions in the upstream regulation of integrin-mediated cell adhesion via the control of focal adhesion remodeling, and discuss how these emerging interconnections between integrin-mediated adhesion pathways and autophagy influence cancer progression and metastasis.

The chemomodulatory effects of glufosfamide on docetaxel cytotoxicity in prostate cancer cells

Background. Glufosfamide (GLU) is a glucose conjugate of ifosfamide in which isophosphoramide mustard is glycosidically linked to the β-D-glucose molecule. Based on GLU structure, it is considered a targeted chemotherapy with fewer side effects. The main objective of the current study is to assess the cytotoxic potential of GLU for the first time in prostate cancer (PC) cells representing different stages of the tumor. Furthermore, this study examined the potential synergistic activity of GLU in combination with docetaxel (DOC).

Methods. Two different cell lines were used, LNCaP and PC-3. Concentration-response curves were assessed. The tested groups per cell line were, control, GLU, DOC and combination. Treatment duration was 72 h. Cytotoxicity was assessed using sulforhodamine B (SRB) assay and half maximal inhibitory concentration (IC50) was calculated. Synergy analyses were performed using Calcusyn^®software. Subsequent mechanistic studies included β-glucosidase activity assay, glucose uptake and apoptosis studies, namely annexin V-FITC assay and the protein expression of mitochondrial pathway signals including Bcl-2, Bax, Caspase 9 and 3 were assessed. Data are presented as mean ± SD; comparisons were carried out using one way analysis of variance (ANOVA) followed by Tukey-Kramer’s test for post hoc analysis.

Results. GLU induced cytotoxicity in both cell lines in a concentration-dependent manner. The IC50 in PC-3 cells was significantly lower by 19% when compared to that of LNCaP cells. The IC50 of combining both drugs showed comparable effect to DOC in PC-3 but was tremendously lowered by 49% compared to the same group in LNCaP cell line. β-glucosidase activity was higher in LNCaP by about 67% compared to that determined in PC-3 cells while the glucose uptake in PC-3 cells was almost 2 folds that found in LNCaP cells. These results were directly correlated to the efficacy of GLU in each cell line. Treatment of PC cells with GLU as single agent or in combination with DOC induced significantly higher apoptosis as evidenced by Annexin V-staining. Apoptosis was significantly increased in combination group by 4.9 folds and by 2.1 Folds when compared to control in LNCaP cells and PC-3 cells; respectively. Similarly, the expression of Bcl-2 was significantly decreased while Bax, caspase 9 and 3 were significantly increased in the combined treatment groups compared to the control.

Conclusion. GLU has a synergistic effect in combination with DOC as it increases the cell kill which can be attributed at least partially to apoptosis in both the tested cell lines and it is suggested as a new combination regimen to be considered in the treatment of the prostate cancer. Further experiments and clinical investigations are needed for assessment of that regimen.

Cyclin E Associates with the Lipogenic Enzyme ATP-Citrate Lyase to Enable Malignant Growth of Breast Cancer Cells

Cyclin E is altered in nearly a third of invasive breast cancers where it is a powerful independent predictor of survival in women with stage I-III disease. Full-length cyclin E is posttranslationally cleaved into low molecular weight (LMW-E) isoforms, which are tumor-specific and accumulate in the cytoplasm because they lack a nuclear localization sequence. We hypothesized that aberrant localization of cytosolic LMW-E isoforms alters target binding and activation ultimately contributing to LMW-E-induced tumorigenicity. To address this hypothesis, we used a retrovirus-based protein complementation assay to find LMW-E binding proteins in breast cancer, identifying ATP-citrate lyase (ACLY), an enzyme in the de novo lipogenesis pathway, as a novel LMW-E-interacting protein in the cytoplasm. LMW-E upregulated ACLY enzymatic activity, subsequently increasing lipid droplet formation, thereby providing cells with essential building blocks to support growth. ACLY was also required for LMW-E-mediated transformation, migration, and invasion of breast cancer cells in vitro along with tumor growth in vivo In clinical specimens of breast cancer, the absence of LMW-E and low expression of adipophilin (PLIN2), a marker of lipid droplet formation, associated with favorable prognosis, whereas overexpression of both proteins correlated with a markedly worse prognosis. Taken together, our findings establish a novel relationship between LMW-E isoforms of cyclin E and aberrant lipid metabolism pathways in breast cancer tumorigenesis, warranting further investigation in additional malignancies exhibiting their expression. Cancer Res; 76(8); 2406-18. ©2016 AACR.

Advances in HSP27 and HSP90-targeting strategies for glioblastoma

Glioblastoma (GBM) is the most common and malignant primary brain tumor in adults. There is a critical need for novel strategies to abolish the molecular mechanisms that support GBM growth, invasion and treatment resistance. The heat shock proteins, HSP27 and HSP90, serve these pivotal roles in tumor cells and have been identified as effective targets for developing therapeutics. Natural and synthetic inhibitors have been evaluated in clinical trials for several forms of systemic cancer but none as yet for GBM. This topic review summarizes the current preclinical evidence and rationale to define the potential of HSP27 and HSP90 inhibitors in GBM management.

Reprogramming of glucose, fatty acid and amino acid metabolism for cancer progression

Metabolic reprogramming is widely observed during cancer development to confer cancer cells the ability to survive and proliferate, even under the stressed, such as nutrient-limiting, conditions. It is famously known that cancer cells favor the "Warburg effect", i.e., the enhanced glycolysis or aerobic glycolysis, even when the ambient oxygen supply is sufficient. In addition, deregulated anabolism/catabolism of fatty acids and amino acids, especially glutamine, serine and glycine, have been identified to function as metabolic regulators in supporting cancer cell growth. Furthermore, extensive crosstalks are being revealed between the deregulated metabolic network and cancer cell signaling. These exciting advancements have inspired new strategies for treating various malignancies by targeting cancer metabolism. Here we review recent findings related to the regulation of glucose, fatty acid and amino acid metabolism, their crosstalk, and relevant cancer therapy strategy.

Hypoxia is associated with a lower expression of genes involved in lipogenesis in visceral adipose tissue

Background

A key role for HIF-1α in the promotion and maintenance of dietary obesity has been proposed. We analyzed the association between hypoxia and de novo lipogenesis in human adipose tissue.

Methods

We studied HIF-1α mRNA and protein expression in fasting status in visceral adipose tissue (VAT) from non-obese and morbidly obese subjects, and in VAT from wild-type and ob/ob C57BL6J mice in both fasting and feeding status. We also analyzed the effect of hypoxia on the VAT mRNA expression of genes involved in lipogenesis.

Results

HIF-1α was increased in VAT from morbidly obese subjects. In fasting status, C57BL6J ob/ob mice had a higher VAT HIF-1α mRNA expression than C57BL6J wild-type mice. In feeding status, VAT HIF-1α mRNA expression significantly increased in C57BL6J wild-type, but not in C57BL6J ob/ob mice. In humans, HIF-1α mRNA expression correlated positively with body mass index and insulin resistance. VAT HIF-1α mRNA expression correlated negatively with ACC1, PDHB and SIRT3 mRNA expression, and positively with PPAR-γ. VAT explants incubated in hypoxia showed reduced SIRT3 and increased PPAR-γ, SREBP-1c, ACLY, ACC1 and FASN mRNA expression.

Conclusions

Morbidly obese subjects have a higher level of VAT HIF-1α. Postprandial status is associated with an increase in HIF-1α mRNA expression in C57BL6J wild-type mice. Hypoxia alters the mRNA expression of genes involved in de novo lipogenesis in human VAT.

Glioblastomas with copy number gains in EGFR and RNF139 show increased expressions of carbonic anhydrase genes transformed by ENO1

Background

Prominence of glycolysis in glioblastomas may be non-specific or a feature of oncogene-related subgroups (i.e. amplified EGFR, etc.). Relationships between amplified oncogenes and expressions of metabolic genes associated with glycolysis, directly or indirectly via pH, were therefore investigated.

Methods

Using multiplex ligation-dependent probe amplification, copy numbers (CN) of 78 oncogenes were quantified in 24 glioblastomas. Related expressions of metabolic genes encoding lactate dehydrogenases (LDHA, LDHC), carbonic anhydrases (CA3, CA12), monocarboxylate transporters (SLC16A3 or MCT4, SLC16A4 or MCT5), ATP citrate lyase (ACLY), glycogen synthase1 (GYS1), hypoxia inducible factor-1A (HIF1A), and enolase1 (ENO1) were determined in 22 by RT-qPCR. To obtain supra-glycolytic levels and adjust for heterogeneity, concurrent ENO1 expression was used to mathematically transform the expression levels of metabolic genes already normalized with delta-delta crossing threshold methodology.

Results

Positive correlations with EGFR occurred for all metabolic genes. Significant differences (Wilcoxon Rank Sum) for oncogene CN gains in tumors of at least 2.00-fold versus less than 2.00-fold occurred for EGFR with CA3's expression (p < 0.03) and for RNF139 with CA12 (p < 0.004). Increased CN of XIAP associated negatively. Tumors with less than 2.00-fold CN gains differed from those with gains for XIAP with CA12 (p < 0.05). Male gender associated with CA12 (p < 0.05).

Conclusions

Glioblastomas with CN increases in EGFR had elevated CA3 expression. Similarly, tumors with RNF149 CN gains had elevated CA12 expression.

General significance

In larger studies, subgroups of glioblastomas may emerge according to oncogene-related effects on glycolysis, such as control of pH via effects on carbonic anhydrases, with prognostic and treatment implications.

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PCR of glioblastomas show oncogene copy numbers relate to metabolic gene expressions.

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ENO1(ENOLASE1) transformations yielded “supra-glycolytic” metabolic gene expressions.

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EGFR, RNF139, and XIAP associated with expressions of two carbonic anhydrase genes.

•

Male gender associated (+) with the transformed expression of carbonic anhydrase 12.

•

Oncogene amplifications may aid control of pH to protect glycolysis in glioblastomas.

Knockdown of PKM2 Suppresses Tumor Growth and Invasion in Lung Adenocarcinoma

Accumulating evidence shows that activity of the pyruvate kinase M2 (PKM2) isoform is closely related to tumorigenesis. In this study, we investigated the relationship between PKM2 expression, tumor invasion, and the prognosis of patients with lung adenocarcinoma. We retrospectively analyzed 65 cases of patients with lung adenocarcinoma who were divided into low and a high expression groups based on PKM2 immunohistochemical staining. High PKM2 expression was significantly associated with reduced patient survival. We used small interfering RNA (siRNA) technology to investigate the effect of targeted PKM2-knockout on tumor growth at the cellular level. In vitro, siRNA-mediated PKM2-knockdown significantly inhibited the proliferation, glucose uptake (25%), ATP generation (20%) and fatty acid synthesis of A549 cells, while the mitochondrial respiratory capacity of the cells increased (13%).Western blotting analysis showed that PKM2-knockout significantly inhibited the expression of the glucose transporter GLUT1 and ATP citrate lyase, which is critical for fatty acid synthesis. Further Western blotting analysis showed that PKM2-knockdown inhibited the expression of matrix metalloproteinase 2 (MMP-2) and vascular endothelial growth factor (VEGF), which are important in degradation of the extracellular matrix and angiogenesis, respectively. These observations show that PKM2 activates both glycolysis and lipid synthesis, thereby regulating cell proliferation and invasion. This information is important in elucidating the mechanisms by which PKM2 influences the growth and metastasis of lung adenocarcinoma at the cellular and molecular level, thereby providing the basic data required for the development of PKM2-targeted gene therapy.

Mutations in CIC and IDH1 cooperatively regulate 2-hydroxyglutarate levels and cell clonogenicity

The majority of oligodendrogliomas (ODGs) exhibit combined losses of chromosomes 1p and 19q and mutations of isocitrate dehydrogenase (IDH1-R132H or IDH2-R172K). Approximately 70% of ODGs with 1p19q co-deletions harbor somatic mutations in the Capicua Transcriptional Repressor (CIC) gene on chromosome 19q13.2. Here we show that endogenous long (CIC-L) and short (CIC-S) CIC proteins are predominantly localized to the nucleus or cytoplasm, respectively. Cytoplasmic CIC-S is found in close proximity to the mitochondria. To study wild type and mutant CIC function and motivated by the paucity of 1p19q co-deleted ODG lines, we created HEK293 and HOG stable cell lines ectopically co-expressing CIC and IDH1. Non-mutant lines displayed increased clonogenicity, but cells co-expressing the mutant IDH1-R132H with either CIC-S-R201W or -R1515H showed reduced clonogenicity in an additive manner, demonstrating cooperative effects in our assays. Expression of mutant CIC-R1515H increased cellular 2-Hydroxyglutarate (2HG) levels compared to wild type CIC in IDH1-R132H background. Levels of phosphorylated ATP-citrate Lyase (ACLY) were lower in cell lines expressing mutant CIC-S proteins compared to cells expressing wild type CIC-S, supporting a cytosolic citrate metabolism-related mechanism bof reduced clonogenicity in our in vitro model systems. ACLY or phospho-ACLY were similarly reduced in CIC-mutant 1p19q co-deleted oligodendroglioma patient samples.

Metabolic reprogramming in glioblastoma: the influence of cancer metabolism on epigenetics and unanswered questions

A defining hallmark of glioblastoma is altered tumor metabolism. The metabolic shift towards aerobic glycolysis with reprogramming of mitochondrial oxidative phosphorylation, regardless of oxygen availability, is a phenomenon known as the Warburg effect. In addition to the Warburg effect, glioblastoma tumor cells also utilize the tricarboxylic acid cycle/oxidative phosphorylation in a different capacity than normal tissue. Altered metabolic enzymes and their metabolites are oncogenic and not simply a product of tumor proliferation. Here we highlight the advantages of why tumor cells, including glioblastoma cells, require metabolic reprogramming and how tumor metabolism can converge on tumor epigenetics and unanswered questions in the field.

Alpha-enolase promotes cell glycolysis, growth, migration, and invasion in non-small cell lung cancer through FAK-mediated PI3K/AKT pathway

Background

During tumor formation and expansion, increasing glucose metabolism is necessary for unrestricted growth of tumor cells. Expression of key glycolytic enzyme alpha-enolase (ENO1) is controversial and its modulatory mechanisms are still unclear in non-small cell lung cancer (NSCLC).

Methods

The expression of ENO1 was examined in NSCLC and non-cancerous lung tissues, NSCLC cell lines, and immortalized human bronchial epithelial cell (HBE) by quantitative real-time reverse transcription PCR (qRT-PCR), immunohistochemistry, and Western blot, respectively. The effects and modulatory mechanisms of ENO1 on cell glycolysis, growth, migration, invasion, and in vivo tumorigenesis and metastasis in nude mice were also analyzed.

Results

ENO1 expression was increased in NSCLC tissues in comparison to non-cancerous lung tissues. Similarly, NSCLC cell lines A549 and SPCA-1 also express higher ENO1 than HBE cell line in both mRNA and protein levels. Overexpressed ENO1 significantly elevated NSCLC cell glycolysis, proliferation, clone formation, migration, and invasion in vitro, as well as tumorigenesis and metastasis in vivo by regulating the expression of glycolysis, cell cycle, and epithelial-mesenchymal transition (EMT)-associated genes. Conversely, ENO1 knockdown reversed these effects. More importantly, our further study revealed that stably upregulated ENO1 activated FAK/PI3K/AKT and its downstream signals to regulate the glycolysis, cell cycle, and EMT-associated genes.

Conclusion

This study showed that ENO1 is responsible for NSCLC proliferation and metastasis; thus, ENO1 might serve as a potential molecular therapeutic target for NSCLC treatment.

Electronic supplementary material

The online version of this article (doi:10.1186/s13045-015-0117-5) contains supplementary material, which is available to authorized users.

Functional polymorphisms of ATP citrate lyase gene predicts clinical outcome of patients with advanced colorectal cancer

BACKGROUND

Previous studies have demonstrated that ATP citrate lyase (ACLY) plays an important role in the development of many cancers. Our current study aims to assess the effects of functional single nucleotide polymorphisms (SNPs) in ACLY gene on recurrence and survival of colorectal cancer (CRC) patients.

METHODS

A total of 697 resected Chinese CRC patients were included in this study. Two functional single nucleotide polymorphisms in ACLY gene were examined using the Sequenom iPLEX genotyping system. Multivariate Cox proportional hazards model and Kaplan-Meier curve were used for the prognosis analysis.

RESULTS

Multivariate Cox regression analysis showed that there was no significant association between SNPs in ACLY gene and the prognosis of total patient cohort. However, in patients with stage III + IV diseases, the two functional SNPs (rs2304497 and rs9912300) exhibited a significant association with the risks of death (HR = 0.47, 95% CI = 0.24-0.90 and HR = 0.59, 95% CI = 0.37-0.92, respectively) and recurrence (HR = 0.46, 95% CI = 0.24-0.86 and HR = 0.54, CI = 0.35-0.83, respectively). Kaplan-Meier analysis indicated that those CRC patients carrying heterozygous (WV) or homozygous variant (VV) genotypes in rs2304497 and rs9912300 had significantly better overall survival (OS) and recurrence-free survival (RFS). Moreover, we observed remarkable cumulative effects of these two SNPs on overall survival and recurrence-free survival (P for trend = 0.012 and 0.003, respectively). Compared with patients carrying zero unfavorable genotype, those carrying two unfavorable genotypes had a 2.24-fold and 2.33-fold increase of death and recurrence risks, respectively.

CONCLUSIONS

The SNPs in ACLY gene may serve as independent prognostic markers for patients with advanced stage CRC.

Cellular and metabolic functions for autophagy in cancer cells

Autophagy is a lysosomal degradation pathway that acts as a dynamic regulator of tumorigenesis. Specifically, autophagy has been shown to impede early cancer development while facilitating advanced tumor progression. Recent studies have uncovered several tumor-promoting functions for autophagy; these include the maintenance of multiple metabolic pathways critical for aggressive tumor growth and the promotion of tumor cell survival downstream of the unfolded protein response. Furthermore, autophagy supports anoikis resistance and cancer cell invasion. At the same time, because autophagy cargo receptors, which are essential for selective autophagy, lie upstream of diverse cancer-promoting signaling pathways, they may profoundly influence how alterations in autophagy affect tumor development. This review focuses on how these tumor cell autonomous functions of autophagy broadly impact tumorigenesis.

Alpha-enolase as a potential cancer prognostic marker promotes cell growth, migration, and invasion in glioma

BACKGROUND

The success of using glycolytic inhibitors for cancer treatment relies on better understanding the roles of each frequently deregulated glycolytic genes in cancer. This report analyzed the involvement of a key glycolytic enzyme, alpha-enolase (ENO1), in tumor progression and prognosis of human glioma.

METHODS

ENO1 expression levels were examined in glioma tissues and normal brain (NB) tissues. The molecular mechanisms of ENO1 expression and its effects on cell growth, migration and invasion were also explored by 3-[4,5-dimethylthiazol-2-yl]-2,5 diphenyl tetrazolium bromide (MTT) assay, Transwell chamber assay, Boyden chamber assay, Western blot and in vivo tumorigenesis in nude mice.

RESULTS

ENO1 mRNA and protein levels were upregulated in glioma tissues compared to NB. In addition, increased ENO1 was associated disease progression in glioma samples. Knocking down ENO1 expression not only significantly decreased cell proliferation, but also markedly inhibited cell migration and invasion as well as in vivo tumorigenesis. Mechanistic analyses revealed that Cyclin D1, Cyclin E1, pRb, and NF-κB were downregulated after stable ENO1 knockdown in glioma U251 and U87 cells. Conversely, knockdown of ENO1 resulted in restoration of E-cadherin expression and suppression of mesenchymal cell markers, such as Vimentin, Snail, N-Cadherin, β-Catenin and Slug. Furthermore, ENO1 suppression inactivated PI3K/Akt pathway regulating the cell growth and epithelial-mesenchymal transition (EMT) progression.

CONCLUSION

Overexpression of ENO1 is associated with glioma progression. Knockdown of ENO1 expression led to suppressed cell growth, migration and invasion progression by inactivating the PI3K/Akt pathway in glioma cells.

ATP citrate lyase mediates resistance of colorectal cancer cells to SN38

Combination chemotherapy is standard for metastatic colorectal cancer; however, nearly all patients develop drug resistance. Understanding the mechanisms that lead to resistance to individual chemotherapeutic agents may enable identification of novel targets and more effective therapy. Irinotecan is commonly used in first- and second-line therapy for patients with metastatic colorectal cancer, with the active metabolite being SN38. Emerging evidence suggests that altered metabolism in cancer cells is fundamentally involved in the development of drug resistance. Using Oncomine and unbiased proteomic profiling, we found that ATP citrate lyase (ACLy), the first-step rate-limiting enzyme for de novo lipogenesis, was upregulated in colorectal cancer compared with its levels in normal mucosa and in chemoresistant colorectal cancer cells compared with isogenic chemo-naïve colorectal cancer cells. Overexpression of exogenous ACLy by lentivirus transduction in chemo-naïve colorectal cancer cells led to significant chemoresistance to SN38 but not to 5-fluorouracil or oxaliplatin. Knockdown of ACLy by siRNA or inhibition of its activity by a small-molecule inhibitor sensitized chemo-naïve colorectal cancer cells to SN38. Furthermore, ACLy was significantly increased in cancer cells that had acquired resistance to SN38. In contrast to chemo-naïve cells, targeting ACLy alone was not effective in resensitizing resistant cells to SN38, due to a compensatory activation of the AKT pathway triggered by ACLy suppression. Combined inhibition of AKT signaling and ACLy successfully resensitized SN38-resistant cells to SN38. We conclude that targeting ACLy may improve the therapeutic effects of irinotecan and that simultaneous targeting of ACLy and AKT may be warranted to overcome SN38 resistance.

Regulation of metabolic products and gene expression in Fusarium asiaticum by agmatine addition

The metabolic products resulting from the cultivation of F. asiaticum in agmatine were identified using capillary electrophoresis–time of flight mass spectrometry. Glyoxylic acid was detected from fungal cultures grown in agmatine, while it was absent in control cells. The abundance of other metabolic products of the glycolytic pathway also increased because of agmatine; however, there was no increase in the amounts of pyruvic acid or metabolites from the tricarboxylic acid cycle. Moreover, gene expression levels within Fusarium asiaticum exposed to agmatine were analyzed by DNA microarray. Changes in gene expression levels directed the changes in metabolic products. Our results suggest that acetyl coenzyme A, which is a starting substrate for the biosynthesis of deoxynivalenol (DON), was simultaneously produced by activated β-oxidation. Furthermore, the content of 4-aminobutyrate (GABA) was increased in the agmatine addition culture medium. GABA can be synthesized from agmatine through putrescine and might influence the regulation of DON-related genes.