THE GROWTH RESPONSE OF MAMMALIAN CELLS IN TISSUE CULTURE TO l-GLUTAMINE AND l-GLUTAMIC ACID

Glutamine sensing licenses cholesterol synthesis

The mevalonate pathway produces essential lipid metabolites such as cholesterol. Although this pathway is negatively regulated by metabolic intermediates, little is known of the metabolites that positively regulate its activity. We found that the amino acid glutamine is required to activate the mevalonate pathway. Glutamine starvation inhibited cholesterol synthesis and blocked transcription of the mevalonate pathway-even in the presence of glutamine derivatives such as ammonia and α-ketoglutarate. We pinpointed this glutamine-dependent effect to a loss in the ER-to-Golgi trafficking of SCAP that licenses the activation of SREBP2, the major transcriptional regulator of cholesterol synthesis. Both enforced Golgi-to-ER retro-translocation and the expression of a nuclear SREBP2 rescued mevalonate pathway activity during glutamine starvation. In a cell model of impaired mitochondrial respiration in which glutamine uptake is enhanced, SREBP2 activation and cellular cholesterol were increased. Thus, the mevalonate pathway senses and is activated by glutamine at a previously uncharacterized step, and the modulation of glutamine synthesis may be a strategy to regulate cholesterol levels in pathophysiological conditions.

Serum-Free Media Formulation Using Marine Microalgae Extracts and Growth Factor Cocktails for Madin-Darby Canine Kidney and Vero Cell Cultures

The development of serum-free media (SFM) is critical to advance cell culture techniques used in viral vaccine production and address the ethical concerns and contamination risks associated with fetal bovine serum (FBS). This study evaluated the effects of marine microalgal extracts and growth factor cocktails on the activity of Madin-Darby canine kidney (MDCK) and Vero cells. Five marine microalgal species were used: Spirulina platensis (SP), Dunaliella salina (DS), Haematococcus pluvialis (HP), Nannochloropsis salina (NS), and Tetraselmis sp. (TS). DS and SP extracts significantly increased the proliferation rate of both MDCK and Vero cells. DS had a proliferation rate of 149.56% and 195.50% in MDCK and Vero cells, respectively, compared with that in serum-free medium (SFM). Notably, DS and SP extracts significantly increased superoxide dismutase (SOD) activity, which was 118.61% in MDCK cells and 130.08% in Vero cells for DS, and 108.72% in MDCK cells and 125.63% in Vero cells for SP, indicating a reduction in intracellular oxidative stress. Marine microalgal extracts, especially DS and SP, are feasible alternatives to FBS in cell culture as they promote cell proliferation, ensure safety, and supply essential nutrients while reducing oxidative stress.

Stable isotope-resolved metabolomics analyses of metabolic phenotypes reveal variable glutamine metabolism in different patient-derived models of non-small cell lung cancer from a single patient

INTRODUCTION

Stable isotope tracers have been increasingly used in preclinical cancer model systems, including cell culture and mouse xenografts, to probe the altered metabolism of a variety of cancers, such as accelerated glycolysis and glutaminolysis and generation of oncometabolites. Comparatively little has been reported on the fidelity of the different preclinical model systems in recapitulating the aberrant metabolism of tumors.

OBJECTIVES

We have been developing several different experimental model systems for systems biochemistry analyses of non-small cell lung cancer (NSCLC1) using patient-derived tissues to evaluate appropriate models for metabolic and phenotypic analyses.

METHODS

To address the issue of fidelity, we have carried out a detailed Stable Isotope-Resolved Metabolomics study of freshly resected tissue slices, mouse patient derived xenografts (PDXs), and cells derived from a single patient using both 13C6-glucose and 13C5,15N2-glutamine tracers.

RESULTS

Although we found similar glucose metabolism in the three models, glutamine utilization was markedly higher in the isolated cell culture and in cell culture-derived xenografts compared with the primary cancer tissue or direct tissue xenografts (PDX).

CONCLUSIONS

This suggests that caution is needed in interpreting cancer biochemistry using patient-derived cancer cells in vitro or in xenografts, even at very early passage, and that direct analysis of patient derived tissue slices provides the optimal model for ex vivo metabolomics. Further research is needed to determine the generality of these observations.

Enzymatic depletion of circulating glutamine is immunosuppressive in cancers

Although glutamine addiction in cancer cells is extensively reported, there is controversy on the impact of glutamine metabolism on the immune cells within the tumor microenvironment (TME). To address the role of extracellular glutamine, we enzymatically depleted circulating glutamine using PEGylated Helicobacter pylori gamma-glutamyl transferase (PEG-GGT) in syngeneic mouse models of breast and colon cancers. PEG-GGT treatment inhibits growth of cancer cells in vitro, but in vivo it increases myeloid-derived suppressor cells (MDSCs) and has no significant impact on tumor growth. By deriving a glutamine depletion signature, we analyze diverse human cancers within the TCGA and illustrate that glutamine depletion is not associated with favorable clinical outcomes and correlates with accumulation of MDSC. Broadly, our results help clarify the integrated impact of glutamine depletion within the TME and advance PEG-GGT as an enzymatic tool for the systemic and selective depletion (no asparaginase activity) of circulating glutamine in live animals.

The potential of Rhodobacter sphaeroides extract as an alternative supplement for cell culture systems

It is essential to identify suitable supplements that enhance cell growth, viability, and functional development in cell culture systems. The use of fetal bovine serum (FBS) has been common, but it has limitations, such as batch-to-batch variability, ethical concerns, and risks of environmental contamination. In this study, we explore the potential of Rhodobacter sphaeroides extract, derived from a probiotic photosynthetic bacterium, as an alternative supplement. Our results demonstrate that the extract from R. sphaeroides significantly improves various aspects of cell behavior compared to serum-free conditions. It enhances cell growth and viability to a greater extent than FBS supplementation. Additionally, the extract alleviates oxidative stress by reducing intracellular levels of reactive oxygen species and stimulates lysosomal activity, contributing to cellular processes. The presence of abundant amino acids, glycine and arginine, in the extract may play a role in promoting cell growth. These findings emphasize the potential of R. sphaeroides extract as a valuable supplement for cell culture, offering advantages over the use of FBS.IMPORTANCEThe choice of supplements for cell culture is crucial in biomedical research, but the widely used fetal bovine serum (FBS) has limitations in terms of variability, ethics, and environmental risks. This study explores the potential of an extract from Rhodobacter sphaeroides, a probiotic bacterium, as an alternative supplement. The findings reveal that the R. sphaeroides extract surpasses FBS in enhancing cell growth, viability, and functionality. It also mitigates oxidative stress and stimulates lysosomal activity, critical for cellular health. The extract's abundance of glycine and arginine, amino acids with known growth-promoting effects, further highlights its potential. By providing a viable substitute for FBS, the R. sphaeroides extract addresses the need for consistent, ethical, and environmentally friendly cell culture supplements. This research paves the way for sustainable and reliable cell culture systems, revolutionizing biomedical research and applications in drug development and regenerative medicine.

Metabolic regulation of the hallmarks of stem cell biology

Stem cells perform many different functions, each of which requires specific metabolic adaptations. Over the past decades, studies of pluripotent and tissue stem cells have uncovered a range of metabolic preferences and strategies that correlate with or exert control over specific cell states. This review aims to describe the common themes that emerge from the study of stem cell metabolism: (1) metabolic pathways supporting stem cell proliferation, (2) metabolic pathways maintaining stem cell quiescence, (3) metabolic control of cellular stress responses and cell death, (4) metabolic regulation of stem cell identity, and (5) metabolic requirements of the stem cell niche.

Glutamine addiction in tumor cell: oncogene regulation and clinical treatment

After undergoing metabolic reprogramming, tumor cells consume additional glutamine to produce amino acids, nucleotides, fatty acids, and other substances to facilitate their unlimited proliferation. As such, the metabolism of glutamine is intricately linked to the survival and progression of cancer cells. Consequently, targeting the glutamine metabolism presents a promising strategy to inhibit growth of tumor cell and cancer development. This review describes glutamine uptake, metabolism, and transport in tumor cells and its pivotal role in biosynthesis of amino acids, fatty acids, nucleotides, and more. Furthermore, we have also summarized the impact of oncogenes like C-MYC, KRAS, HIF, and p53 on the regulation of glutamine metabolism and the mechanisms through which glutamine triggers mTORC1 activation. In addition, role of different anti-cancer agents in targeting glutamine metabolism has been described and their prospective applications are assessed.

The key role of glutamine for protein expression and isotopic labeling in insect cells

Nuclear magnetic resonance studies of many physiologically important proteins have long been impeded by the necessity to express such proteins in isotope-labeled form in higher eukaryotic cells and the concomitant high costs of providing isotope-labeled amino acids in the growth medium. Economical routes use isotope-labeled yeast or algae extracts but still require expensive isotope-labeled glutamine. Here, we have systematically quantified the effect of 15N2-glutamine on the expression and isotope labeling of different proteins in insect cells. Sufficient levels of glutamine in the medium increase the protein expression by four to five times relative to deprived conditions. 1H-15N nuclear magnetic resonance spectroscopy shows that the 15N atoms from 15N2-glutamine are scrambled with surprisingly high (60-70%) efficiency into the three amino acids alanine, aspartate, and glutamate. This phenomenon gives direct evidence that the high energy demand of insect cells during baculovirus infection and concomitant heterologous protein expression is predominantly satisfied by glutamine feeding the tricarboxylic acid cycle. To overcome the high costs of supplementing isotope-labeled glutamine, we have developed a robust method for the large-scale synthesis of 15N2-glutamine and partially deuterated 15N2-glutamine-α,β,β-d3 from inexpensive precursors. An application is shown for the effective large-scale expression of the isotope-labeled β1-adrenergic receptor using the synthesized 15N2-glutamine-α,β,β-d3.

Elucidating the molecular mechanisms of ozone therapy for neuropathic pain management by integrated transcriptomic and metabolomic approach

Introduction: Neuropathic pain remains a prevalent and challenging condition to treat, with current therapies often providing inadequate relief. Ozone therapy has emerged as a promising treatment option; however, its mechanisms of action in neuropathic pain remain poorly understood. Methods: In this study, we investigated the effects of ozone treatment on gene expression and metabolite levels in the brainstem and hypothalamus of a rat model, using a combined transcriptomic and metabolomic approach. Results: Our findings revealed significant alterations in key genes, including DCST1 and AIF1L, and metabolites such as Aconitic acid, L-Glutamic acid, UDP-glucose, and Tyrosine. These changes suggest a complex interplay of molecular pathways and region-specific mechanisms underlying the analgesic effects of ozone therapy. Discussion: Our study provides insights into the molecular targets of ozone treatment for neuropathic pain, laying the groundwork for future research on validating these targets and developing novel therapeutic strategies.

Cancer Metabolism Historical Perspectives: A Chronicle of Controversies and Consensus

A century ago, Otto Warburg's work sparked the field of cancer metabolism, which has since taken a tortuous path. As evidence accumulated over the decades, consensus views of causes of cancer emerged, whereby genetic and epigenetic oncogenic drivers promoted immune evasion and induced new blood vessels and neoplastic metabolism to support tumor growth. Neoplastic cells abandon social cues of intercellular cooperation, escape tissue confinement, metastasize, and ultimately kill the host. Herein, key milestones in the study of cancer metabolism are chronicled with an emphasis on carbohydrate metabolism. The field began with a cancer cell-autonomous view that has been refined by a richer understanding of solid cancers as growing, immune-suppressive, complex organs comprising different cell types that are nourished by a variety of nutrients and variable amounts of oxygen through abnormal neovasculatures. Based on foundational historical studies, our current understanding of cancer metabolism offers a hopeful outlook for targeting metabolism to enhance cancer therapy.

Role of ammonia in NAFLD: An unusual suspect

Mechanistically, the symptomatology and disease progression of non-alcoholic fatty liver disease (NAFLD) remain poorly understood, which makes therapeutic progress difficult. In this review, we focus on the potential importance of decreased urea cycle activity as a pathogenic mechanism. Urea synthesis is an exclusive hepatic function and is the body's only on-demand and definitive pathway to remove toxic ammonia. The compromised urea cycle activity in NAFLD is likely caused by epigenetic damage to urea cycle enzyme genes and increased hepatocyte senescence. When the urea cycle is dysfunctional, ammonia accumulates in liver tissue and blood, as has been demonstrated in both animal models and patients with NAFLD. The problem may be augmented by parallel changes in the glutamine/glutamate system. In the liver, the accumulation of ammonia leads to inflammation, stellate cell activation and fibrogenesis, which is partially reversible. This may be an important mechanism for the transition of bland steatosis to steatohepatitis and further to cirrhosis and hepatocellular carcinoma. Systemic hyperammonaemia has widespread negative effects on other organs. Best known are the cerebral consequences that manifest as cognitive disturbances, which are prevalent in patients with NAFLD. Furthermore, high ammonia levels induce a negative muscle protein balance leading to sarcopenia, compromised immune function and increased risk of liver cancer. There is currently no rational way to reverse reduced urea cycle activity but there are promising animal and human reports of ammonia-lowering strategies correcting several of the mentioned untoward aspects of NAFLD. In conclusion, the ability of ammonia-lowering strategies to control the symptoms and prevent the progression of NAFLD should be explored in clinical trials.

Nutritional requirements of human induced pluripotent stem cells

The nutritional requirements for human induced pluripotent stem cell (hiPSC) growth have not been extensively studied. Here, building on our prior work that established the suitable non-basal medium components for hiPSC growth, we develop a simplified basal medium consisting of just 39 components, demonstrating that many ingredients of DMEM/F12 are either not essential or are at suboptimal concentrations. This new basal medium along with the supplement, which we call BMEM, enhances the growth rate of hiPSCs over DMEM/F12-based media, supports derivation of multiple hiPSC lines, and allows differentiation to multiple lineages. hiPSCs cultured in BMEM consistently have enhanced expression of undifferentiated cell markers such as POU5F1 and NANOG, along with increased expression of markers of the primed state and reduced expression of markers of the naive state. This work describes titration of the nutritional requirements of human pluripotent cell culture and identifies that suitable nutrition enhances the pluripotent state.

Microfabricated polymer-metal biosensors for multifarious data collection from electrogenic cellular models

Benchtop tissue cultures have become increasingly complex in recent years, as more on-a-chip biological technologies, such as microphysiological systems (MPS), are developed to incorporate cellular constructs that more accurately represent their respective biological systems. Such MPS have begun facilitating major breakthroughs in biological research and are poised to shape the field in the coming decades. These biological systems require integrated sensing modalities to procure complex, multiplexed datasets with unprecedented combinatorial biological detail. In this work, we expanded upon our polymer-metal biosensor approach by demonstrating a facile technology for compound biosensing that was characterized through custom modeling approaches. As reported herein, we developed a compound chip with 3D microelectrodes, 3D microfluidics, interdigitated electrodes (IDEs) and a microheater. The chip was subsequently tested using the electrical/electrochemical characterization of 3D microelectrodes with 1 kHz impedance and phase recordings and IDE-based high-frequency (~1 MHz frequencies) impedimetric analysis of differential localized temperature recordings, both of which were modeled through equivalent electrical circuits for process parameter extraction. Additionally, a simplified antibody-conjugation strategy was employed for a similar IDE-based analysis of the implications of a key analyte (l-glutamine) binding to the equivalent electrical circuit. Finally, acute microfluidic perfusion modeling was performed to demonstrate the ease of microfluidics integration into such a polymer-metal biosensor platform for potential complimentary localized chemical stimulation. Overall, our work demonstrates the design, development, and characterization of an accessibly designed polymer-metal compound biosensor for electrogenic cellular constructs to facilitate comprehensive MPS data collection.

Regulation and function of the mammalian tricarboxylic acid cycle

The tricarboxylic acid (TCA) cycle, otherwise known as the Krebs cycle, is a central metabolic pathway that performs the essential function of oxidizing nutrients to support cellular bioenergetics. More recently, it has become evident that TCA cycle behavior is dynamic, and products of the TCA cycle can be co-opted in cancer and other pathologic states. In this review, we revisit the TCA cycle, including its potential origins and the history of its discovery. We provide a detailed accounting of the requirements for sustained TCA cycle function and the critical regulatory nodes that can stimulate or constrain TCA cycle activity. We also discuss recent advances in our understanding of the flexibility of TCA cycle wiring and the increasingly appreciated heterogeneity in TCA cycle activity exhibited by mammalian cells. Deeper insight into how the TCA cycle can be differentially regulated and, consequently, configured in different contexts will shed light on how this pathway is primed to meet the requirements of distinct mammalian cell states.

MYCN and Metabolic Reprogramming in Neuroblastoma

Neuroblastoma is a pediatric cancer responsible for approximately 15% of all childhood cancer deaths. Aberrant MYCN activation, as a result of genomic MYCN amplification, is a major driver of high-risk neuroblastoma, which has an overall survival rate of less than 50%, despite the best treatments currently available. Metabolic reprogramming is an integral part of the growth-promoting program driven by MYCN, which fuels cell growth and proliferation by increasing the uptake and catabolism of nutrients, biosynthesis of macromolecules, and production of energy. This reprogramming process also generates metabolic vulnerabilities that can be exploited for therapy. In this review, we present our current understanding of metabolic reprogramming in neuroblastoma, focusing on transcriptional regulation as a key mechanism in driving the reprogramming process. We also highlight some important areas that need to be explored for the successful development of metabolism-based therapy against high-risk neuroblastoma.

Experimental Investigation on the Bioprotective Role of Trehalose on Glutamine Solutions by Infrared Spectroscopy

Glutamine plays a significant role in several basic metabolic processes and is an important regulator of heat shock protein response. The present work is focused on the analysis of the thermal response of aqueous solutions of Glutamine and aqueous solutions of Glutamine in the presence of Trehalose by means of infrared absorption technique. The performed study shows how in the case of a multicomponent system, characterized by a huge number of spectral contributions whose assignment are questionable, the Spectral Distance (SD) and the Cross Wavelet Correlation (XWT) approaches are able to furnish explanatory parameters that can characterize the variations in the spectra behaviour, which is an efficient tool for quantitative comparisons. With this purpose, the analysis has been performed by evaluating the SD and the XWT parameters for the whole investigated spectral range, i.e., 4000–400 cm⁻¹, for scans collected as a function of temperature in the range 20 °C ÷ 60 °C both for Glutamine/Water compounds and for Glutamine /Water/Trehalose mixtures. By means of these analyses, it is found that in aqueous solutions of Glutamine, with respect to aqueous solutions of Glutamine in the presence of Trehalose, the SD and XWT temperature trends follow a linear behaviour where the angular coefficient for Glutamine /Water/Trehalose compounds are lower than that of the Glutamine-Water system in both cases. The obtained findings suggest that Trehalose stabilizes Glutamine against heat treatment.

Metabolome analysis reveals a diversity of cancer tissues in advanced epithelial ovarian cancer

Background

Epithelial ovarian cancer remains one of the leading causes of cancer deaths among women worldwide, and advanced epithelial ovarian cancer frequently metastasizes to the omentum. The characteristics of metastatic cancer may differ from those of primary ovarian cancer and reflect the unique omental microenvironment. This study investigated metabolomic differences in epithelial ovarian cancers.

Methods

Patients with advanced epithelial ovarian cancer were eligible for this study. Five patients underwent surgery and resection of paired primary ovarian and omental metastatic cancer at Nagoya University. Metabolome analysis was performed in these paired cancer and metastatic cancer tissues through a facility service (C-SCOPE) at Human Metabolome Technologies, Inc. The concentrations of 116 compounds were measured by CE-TOFMS and CE-QqQMS, and 30 metabolic parameters were calculated. For statistical analyses, Welch’s t-test was used for comparisons between two independent groups.

Results

Metabolite profiles were all different, which reflects diversity among these cancer tissues. Of the measured compounds, urea was the only metabolite that was significantly decreased in omental metastatic cancers compared with the primary cancers (p = 0.031). Moreover, in omental metastatic cancers, the pentose phosphate pathway was more dominant than glycolysis. Furthermore, in some cases, lactic acids in omental metastatic cancers were markedly decreased compared with primary cancers. With regard to histological subtype, the total levels of amino acids, especially the percentage of glutamine, were significantly enriched in serous carcinomas compared with nonserous carcinomas (p = 0.004 and p = 0.001). Moreover, the reduced forms of glutathione and polyamines were also more abundant in serous carcinomas than in nonserous carcinomas (p = 0.025 and 0.048).

Conclusions

The metabolite profiles differed depending on tumor location and histological subtype. Metabolome analysis may be a useful tool for identifying cancer diagnostic and prognostic markers.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12935-021-02014-7.

Carnosine suppresses human glioma cells under normoxic and hypoxic conditions partly via inhibiting glutamine metabolism

L-Carnosine (β-alanyl-L-histidine) is a naturally occurring dipeptide, which has shown broad-spectrum anticancer activity. But the anticancer mechanisms and regulators remain unknown. In this study, we investigated the effects of carnosine on human glioma U87 and U251 cell lines under normoxia (21% O2) and hypoxia (1% O2). We showed that carnosine (25-75 mM) dose-dependently inhibited the proliferation of the glioma cells; carnosine (50 mM) inhibited their colony formation, migration, and invasion capacity. But there was no significant difference in the inhibitory effects of carnosine under normoxia and hypoxia. Treatment with carnosine (50 mM) significantly decreased the expression of glutamine synthetase (GS) at the translation level rather than the transcription level in U87 and U251 cells, both under normoxia and hypoxia. Furthermore, the silencing of GS gene with shRNA and glutamine (Gln) deprivation significantly suppressed the growth, migratory, and invasive potential of the glioma cells. The inhibitory effect of carnosine on U87 and U251 cells was partly achieved by inhibiting the Gln metabolism pathway. Carnosine reduced the expression of GS in U87 and U251 cells by promoting the degradation of GS through the proteasome pathway, shortening the protein half-life, and reducing its stability. Given that targeting tumor metabolism is a proven efficient therapeutic tactic, our results may present new treatment strategies and drugs for improving the prognosis of gliomas.

Towards Physiologic Culture Approaches to Improve Standard Cultivation of Mesenchymal Stem Cells

Mesenchymal stem cells (MSCs) are of great interest for their use in cell-based therapies due to their multipotent differentiation and immunomodulatory capacities. In consequence of limited numbers following their isolation from the donor tissue, MSCs require extensive expansion performed in traditional 2D cell culture setups to reach adequate amounts for therapeutic use. However, prolonged culture of MSCs in vitro has been shown to decrease their differentiation potential and alter their immunomodulatory properties. For that reason, preservation of these physiological characteristics of MSCs throughout their in vitro culture is essential for improving the efficiency of therapeutic and in vitro modeling applications. With this objective in mind, many studies already investigated certain parameters for enhancing current standard MSC culture protocols with regard to the effects of specific culture media components or culture conditions. Although there is a lot of diversity in the final therapeutic uses of the cells, the primary stage of standard isolation and expansion is imperative. Therefore, we want to review on approaches for optimizing standard MSC culture protocols during this essential primary step of in vitro expansion. The reviewed studies investigate and suggest improvements focused on culture media components (amino acids, ascorbic acid, glucose level, growth factors, lipids, platelet lysate, trace elements, serum, and xenogeneic components) as well as culture conditions and processes (hypoxia, cell seeding, and dissociation during passaging), in order to preserve the MSC phenotype and functionality during the primary phase of in vitro culture.

Diverse metabolic response of cancer cells treated with a 213Bi-anti-EGFR-immunoconjugate

Evaluation of treatment response is among the major challenges in modern oncology. We herein used a monoclonal antibody targeting the EGF receptor (EGFR) labelled with the alpha emitter ²¹³Bi (²¹³Bi-anti-EGFR-MAb). EJ28Luc (bladder) and LN18 (glioma) cancer cells, both overexpressing EGFR, were incubated for 3 h with the radioimmunoconjugate. To assess the responses in the core carbon metabolism upon this treatment, these cancer cell lines were subsequently cultivated for 18 h in the presence of [U-¹³C₆]glucose. ¹³C-enrichment and isotopologue profiles of key amino acids were monitored by gas chromatography–mass spectrometry (GC/MS), in order to monitor the impacts of the radionuclide-treatment upon glucose metabolism. In comparison to untreated controls, treatment of EJ28Luc cells with ²¹³Bi-anti-EGFR-MAb resulted in a significantly decreased incorporation of ¹³C from [U-¹³C₆]glucose into alanine, aspartate, glutamate, glycine, proline and serine. In sharp contrast, the same amino acids did not display less ¹³C-enrichments during treatment of the LN18 cells. The data indicate early treatment response of the bladder cancer cells, but not of the glioma cells though cell lines were killed following ²¹³Bi-anti-EGFR-MAb treatment. The pilot study shows that the ¹³C-labelling approach is a valid tool to assess the responsiveness of cancer cells upon radionuclide-treatment in considerable metabolic detail.

From Glucose to Lactate and Transiting Intermediates Through Mitochondria, Bypassing Pyruvate Kinase: Considerations for Cells Exhibiting Dimeric PKM2 or Otherwise Inhibited Kinase Activity

A metabolic hallmark of many cancers is the increase in glucose consumption coupled to excessive lactate production. Mindful that L-lactate originates only from pyruvate, the question arises as to how can this be sustained in those tissues where pyruvate kinase activity is reduced due to dimerization of PKM2 isoform or inhibited by oxidative/nitrosative stress, posttranslational modifications or mutations, all widely reported findings in the very same cells. Hereby 17 pathways connecting glucose to lactate bypassing pyruvate kinase are reviewed, some of which transit through the mitochondrial matrix. An additional 69 converging pathways leading to pyruvate and lactate, but not commencing from glucose, are also examined. The minor production of pyruvate and lactate by glutaminolysis is scrutinized separately. The present review aims to highlight the ways through which L-lactate can still be produced from pyruvate using carbon atoms originating from glucose or other substrates in cells with kinetically impaired pyruvate kinase and underscore the importance of mitochondria in cancer metabolism irrespective of oxidative phosphorylation.

Brain Tumor Stem Cell Dependence on Glutaminase Reveals a Metabolic Vulnerability through the Amino Acid Deprivation Response Pathway

Cancer cells can metabolize glutamine to replenish TCA cycle intermediates, leading to a dependence on glutaminolysis for cell survival. However, a mechanistic understanding of the role that glutamine metabolism has on the survival of glioblastoma (GBM) brain tumor stem cells (BTSC) has not yet been elucidated. Here, we report that across a panel of 19 GBM BTSC lines, inhibition of glutaminase (GLS) showed a variable response from complete blockade of cell growth to absolute resistance. Surprisingly, BTSC sensitivity to GLS inhibition was a result of reduced intracellular glutamate triggering the amino acid deprivation response (AADR) and not due to the contribution of glutaminolysis to the TCA cycle. Moreover, BTSC sensitivity to GLS inhibition negatively correlated with expression of the astrocytic glutamate transporters EAAT1 and EAAT2. Blocking glutamate transport in BTSCs with high EAAT1/EAAT2 expression rendered cells susceptible to GLS inhibition, triggering the AADR and limiting cell growth. These findings uncover a unique metabolic vulnerability in BTSCs and support the therapeutic targeting of upstream activators and downstream effectors of the AADR pathway in GBM. Moreover, they demonstrate that gene expression patterns reflecting the cellular hierarchy of the tissue of origin can alter the metabolic requirements of the cancer stem cell population. SIGNIFICANCE: Glioblastoma brain tumor stem cells with low astrocytic glutamate transporter expression are dependent on GLS to maintain intracellular glutamate to prevent the amino acid deprivation response and cell death.

Computational models applied to metabolomics data hints at the relevance of glutamine metabolism in breast cancer

Background

Metabolomics has a great potential in the development of new biomarkers in cancer and it has experiment recent technical advances.

Methods

In this study, metabolomics and gene expression data from 67 localized (stage I to IIIB) breast cancer tumor samples were analyzed, using (1) probabilistic graphical models to define associations using quantitative data without other a priori information; and (2) Flux Balance Analysis and flux activities to characterize differences in metabolic pathways.

Results

On the one hand, both analyses highlighted the importance of glutamine in breast cancer. Moreover, cell experiments showed that treating breast cancer cells with drugs targeting glutamine metabolism significantly affects cell viability. On the other hand, these computational methods suggested some hypotheses and have demonstrated their utility in the analysis of metabolomics data and in associating metabolomics with patient’s clinical outcome.

Conclusions

Computational analyses applied to metabolomics data suggested that glutamine metabolism is a relevant process in breast cancer. Cell experiments confirmed this hypothesis. In addition, these computational analyses allow associating metabolomics data with patient prognosis.

NUDT21 suppresses the growth of small cell lung cancer by modulating GLS1 splicing

The mRNA precursor 3'-end modification factor NUDT21 is a major regulator of 3'UTR shortening and an important component of pre-mRNA cleavage and polyadenylation. However, its role in pathologic progress of small cell lung cancer (SCLC) remains unclear. In this study, we observed that NUDT21 expression is downregulated in SCLC tissues. Hypoxia-induced down-regulation of NUDT21 through HIF-1α. NUDT21 shRNA transduction promotes proliferation and inhibits apoptosis of A549 cells. NUDT21 inhibition also promotes tumor growth in a mouse xenograft model. Furthermore, we clarified that HIF-1α mediated NUDT21 downregulation which altered the expression patterns of two isoforms of GLS1, GAC and KGA. These results link the hypoxic tumor environments to aberrant glutamine metabolism which is important for cellular energy in SCLC cells. Therefore, NUDT21 could be considered as a potential target for the treatment of SCLC.

Nitrogen Metabolism in Cancer and Immunity

As one of the fundamental requirements for cell growth and proliferation, nitrogen acquisition and utilization must be tightly regulated. Nitrogen can be generated from amino acids (AAs) and utilized for biosynthetic processes through transamination and deamination reactions. Importantly, limitations of nitrogen availability in cells can disrupt the synthesis of proteins, nucleic acids, and other important nitrogen-containing compounds. Rewiring cellular metabolism to support anabolic processes is a feature common to both cancer and proliferating immune cells. In this review, we discuss how nitrogen is utilized in biosynthetic pathways and highlight different metabolic and oncogenic programs that alter the flow of nitrogen to sustain biomass production and growth, an important emerging feature of cancer and immune cell proliferation.

Glutamine Metabolism and Its Role in Immunity, a Comprehensive Review

In the body of an animal, glutamine is a plentiful and very useful amino acid. Glutamine consumption in the body of animals in normal or disease conditions is the same or higher than the glucose. Many in vivo as well as in vitro experiments have been conducted to evaluate the importance of glutamine. Glutamine is a valuable nutrient for the proliferation of the lymphocytes. It also plays a crucial role in the production of cytokines, macrophages, phagocytic, and neutrophil to kill the bacteria. Most of the metabolic organs like the liver, gut, and skeletal muscles control the circulation and availability secretion of glutamine. In catabolic and hypercatabolic conditions, glutamine can turn out to be essential and plays a vital role in metabolism; however, availability may be compromised due to the impairment of homeostasis in the inter-tissue metabolism of amino acids. This is why the supplementation of glutamine is commonly used in clinical nutrition and is especially recommended to immune-suppressed persons. Despite this, in catabolic and hyper-catabolic conditions, it is challenging due to the amino acid concentration in plasma/bloodstream and glutamine should be provided via either the oral, enteral or parenteral route. However, the effect of glutamine as an immune-based supplement has been previously recognized as many research studies conducted in vivo and in-vitro evaluated the beneficial effects of glutamine. Hence, the present study delivers a combined review of glutamine metabolism in essential organs of the cell immune system. In this review, we have also reviewed the metabolism and action of glutamine and crucial problems due to glutamine supplementation in catabolic conditions.

Understanding the role of key amino acids in regulation of proline dehydrogenase/proline oxidase (prodh/pox)-dependent apoptosis/autophagy as an approach to targeted cancer therapy

In stress conditions, as neoplastic transformation, amino acids serve not only as nutrients to maintain the cell survival but also as mediators of several regulatory pathways which are involved in apoptosis and autophagy. Especially, under glucose deprivation, in order to maintain the cell survival, proline and glutamine together with other glutamine-derived products such as glutamate, alpha-ketoglutarate, and ornithine serve as alternative sources of energy. They are substrates for production of pyrroline-5-carboxylate which is the product of conversion of proline by proline dehydrogenase/ proline oxidase (PRODH/POX) to produce ATP for protective autophagy or reactive oxygen species for apoptosis. Interconversion of proline, ornithine, and glutamate may therefore regulate PRODH/POX-dependent apoptosis/autophagy. The key amino acid is proline, circulating between mitochondria and cytoplasm in the proline cycle. This shuttle is known as proline cycle. It is coupled to pentose phosphate pathway producing nucleotides for DNA biosynthesis. PRODH/POX is also linked to p53 and AMP-activated protein kinase (AMPK)-dependent pathways. Proline availability for PRODH/POX-dependent apoptosis/autophagy is regulated at the level of collagen biosynthesis (proline utilizing process) and prolidase activity (proline supporting process). In this review, we suggest that amino acid metabolism linking TCA and Urea cycles affect PRODH/POX-dependent apoptosis/autophagy and the knowledge might be useful to targeted cancer therapy.

Mitochondrial Substrate-Level Phosphorylation as Energy Source for Glioblastoma: Review and Hypothesis

Glioblastoma multiforme (GBM) is the most common and malignant of the primary adult brain cancers. Ultrastructural and biochemical evidence shows that GBM cells exhibit mitochondrial abnormalities incompatible with energy production through oxidative phosphorylation (OxPhos). Under such conditions, the mitochondrial F0-F1 ATP synthase operates in reverse at the expense of ATP hydrolysis to maintain a moderate membrane potential. Moreover, expression of the dimeric M2 isoform of pyruvate kinase in GBM results in diminished ATP output, precluding a significant ATP production from glycolysis. If ATP synthesis through both glycolysis and OxPhos was impeded, then where would GBM cells obtain high-energy phosphates for growth and invasion? Literature is reviewed suggesting that the succinate-CoA ligase reaction in the tricarboxylic acid cycle can substantiate sufficient ATP through mitochondrial substrate-level phosphorylation (mSLP) to maintain GBM growth when OxPhos is impaired. Production of high-energy phosphates would be supported by glutaminolysis—a hallmark of GBM metabolism—through the sequential conversion of glutamine → glutamate → alpha-ketoglutarate → succinyl CoA → succinate. Equally important, provision of ATP through mSLP would maintain the adenine nucleotide translocase in forward mode, thus preventing the reverse-operating F0-F1 ATP synthase from depleting cytosolic ATP reserves. Because glucose and glutamine are the primary fuels driving the rapid growth of GBM and most tumors for that matter, simultaneous restriction of these two substrates or inhibition of mSLP should diminish cancer viability, growth, and invasion.

Glutamine Metabolism Is Essential for Stemness of Bone Marrow Mesenchymal Stem Cells and Bone Homeostasis

Skeleton has emerged as an endocrine organ which is both capable of regulating energy metabolism and being a target for it. Glutamine is the most bountiful and flexible amino acid in the body which provides adenosine 5′-triphosphate (ATP) demands for cells. Emerging evidences support that glutamine which acts as the second metabolic regulator after glucose exerts crucial roles in bone homeostasis at cellular level, including the lineage allocation and proliferation of bone mesenchymal stem cells (BMSCs), the matrix mineralization of osteoblasts, and the biosynthesis in chondrocytes. The integrated mechanism consisting of WNT, mammalian target of rapamycin (mTOR), and reactive oxygen species (ROS) signaling pathway in a glutamine-dependent pattern is responsible to regulate the complex intrinsic biological process, despite more extensive molecules are deserved to be elucidated in glutamine metabolism further. Indeed, dysfunctional glutamine metabolism enhances the development of degenerative bone diseases, such as osteoporosis and osteoarthritis, and glutamine or glutamine progenitor supplementation can partially restore bone defects which may promote treatment of bone diseases, although the mechanisms are not quite clear. In this review, we will summarize and update the latest research findings and clinical trials on the crucial regulatory roles of glutamine metabolism in BMSCs and BMSC-derived bone cells, also followed with the osteoclasts which are important in bone resorption.

We're Not "DON" Yet: Optimal Dosing and Prodrug Delivery of 6-Diazo-5-oxo-L-norleucine

The broadly active glutamine antagonist 6-diazo-5-oxo-L-norleucine (DON) has been studied for 60 years as a potential anticancer therapeutic. Clinical studies of DON in the 1950s using low daily doses suggested antitumor activity, but later phase I and II trials of DON given intermittently at high doses were hampered by dose-limiting nausea and vomiting. Further clinical development of DON was abandoned. Recently, the recognition that multiple tumor types are glutamine-dependent has renewed interest in metabolic inhibitors such as DON. Here, we describe the prior experience with DON in humans. Evaluation of past studies suggests that the major impediments to successful clinical use included unacceptable gastrointestinal (GI) toxicities, inappropriate dosing schedules for a metabolic inhibitor, and lack of targeted patient selection. To circumvent GI toxicity, prodrug strategies for DON have been developed to enhance delivery of active compound to tumor tissues, including the CNS. When these prodrugs are administered in a low daily dosing regimen, appropriate for metabolic inhibition, they are robustly effective without significant toxicity. Patients whose tumors have genetic, metabolic, or imaging biomarker evidence of glutamine dependence should be prioritized as candidates for future clinical evaluations of novel DON prodrugs, given either as monotherapy or in rationally directed pharmacologic combinations. Mol Cancer Ther; 17(9); 1824-32. ©2018 AACR.

Aspulvinone O, a natural inhibitor of GOT1 suppresses pancreatic ductal adenocarcinoma cells growth by interfering glutamine metabolism

BACKGROUND

Distinctive from their normal counterparts, cancer cells exhibit unique metabolic dependencies on glutamine to fuel anabolic processes. Specifically, pancreatic ductal adenocarcinoma (PDAC) cells rely on an unconventional metabolic pathway catalyzed by aspartate transaminase 1 (GOT1) to rewire glutamine metabolism and support nicotinamide adenine dinucleotide phosphate (NADPH) production. Thus, the important role of GOT1 in energy metabolism and Reactive Oxygen Species (ROS) balance demonstrates that targeting GOT1 may serve as an important therapeutic target in PDAC.

METHODS

To assay the binding affinity between Aspulvinone O (AO) and GOT1 proteins, the virtual docking, microscale thermophoresis (MST), cellular thermal shift assay (CETSA) and drug affinity responsive target stability (DARTS) methods were employed. GOT1 was silenced in several PDAC cell lines. The level of OCR and ECR were assayed by seahorse. To evaluate the in vivo anti-tumor efficacy of AO, the xenograft model was built in CB17/scid mouse.

RESULTS

Screening of an in-house natural compound library identified the AO as a novel inhibitor of GOT1 and repressed glutamine metabolism, which sensitizes PDAC cells to oxidative stress and suppresses cell proliferation. Virtual docking analysis suggested that AO could bind to the active site of GOT1 and form obvious hydrophobic interaction with Trp141 together with hydrogen bonds with Thr110 and Ser256. Further in vitro validation, including MST, CETSA and DARTS, further demonstrated the specific combining capacity of AO. We also show that the selective inhibition of GOT1 by AO significantly reduces proliferation of PDAC in vitro and in vivo.

CONCLUSIONS

Taken together, our findings identify AO as a potent bioactive inhibitor of GOT1 and a novel anti-tumour agent for PDAC therapy.

Starve Cancer Cells of Glutamine: Break the Spell or Make a Hungry Monster?

Distinct from normal differentiated tissues, cancer cells reprogram nutrient uptake and utilization to accommodate their elevated demands for biosynthesis and energy production. A hallmark of these types of reprogramming is the increased utilization of, and dependency on glutamine, a nonessential amino acid, for cancer cell growth and survival. It is well-accepted that glutamine is a versatile biosynthetic substrate in cancer cells beyond its role as a proteinogenic amino acid. In addition, accumulating evidence suggests that glutamine metabolism is regulated by many factors, including tumor origin, oncogene/tumor suppressor status, epigenetic alternations and tumor microenvironment. However, despite the emerging understanding of why cancer cells depend on glutamine for growth and survival, the contribution of glutamine metabolism to tumor progression under physiological conditions is still under investigation, partially because the level of glutamine in the tumor environment is often found low. Since targeting glutamine acquisition and utilization has been proposed to be a new therapeutic strategy in cancer, it is central to understand how tumor cells respond and adapt to glutamine starvation for optimized therapeutic intervention. In this review, we first summarize the diverse usage of glutamine to support cancer cell growth and survival, and then focus our discussion on the influence of other nutrients on cancer cell adaptation to glutamine starvation as well as its implication in cancer therapy.

THZ1 suppresses human non-small-cell lung cancer cells in vitro through interference with cancer metabolism

Cancer cells always require more nutrients, energy, and biosynthetic activity to sustain their rapid proliferation than normal cells. Previous studies have shown the impact of THZ1, a covalent inhibitor of cyclin-dependent kinase 7 (CDK7), on transcription regulation and cell-cycle arrest in numerous cancers, but its effects on cellular metabolism in cancer cells remain unknown. In this study we elucidated the anticancer mechanism of THZ1 in human non-small-cell lung cancer (NSCLC) cells. We showed that treatment with THZ1 (10-1000 nM) dose-dependently suppressed the proliferation of human NSCLC cell lines H1299, A549, H292, and H23, and markedly inhibited the migration of these NSCLC cells. Furthermore, treatment with THZ1 (50 nM) arrested cell cycle at G2/M phase and induced apoptosis in these NSCLC cell lines. More importantly, we revealed that treatment with THZ1 (50 nM) blocked the glycolysis pathway but had no effect on glutamine metabolism. We further demonstrated that THZ1 treatment altered the expression pattern of glutaminase 1 (GLS1) isoforms through promoting the ubiquitination and degradation of NUDT21. Combined treatment of THZ1 with a glutaminase inhibitor CB-839 (500 nM) exerted a more potent anti-proliferative effect in these NSCLC cell lines than treatment with THZ1 or CB-839 alone. Our results demonstrate that the inhibitory effect of THZ1 on the growth of human NSCLC cells is partially attributed to interfering with cancer metabolism. Thus, we provide a new potential therapeutic strategy for NSCLC treatment by combining THZ1 with the inhibitors of glutamine metabolism.

Effect of amino-acid intake on physical conditions and skin state: a randomized, double-blind, placebo-controlled, crossover trial

The objective of this study is to elucidate the effect of a supplement enriched with l-leucine, l-arginine, and l-glutamine on body compositions/skin conditions. Healthy young women (n = 29) were allocated to a group (n = 14) receiving an amino-acid supplement (600 mg l-leucine, 250 mg l-arginine, and 300 mg l-glutamine) and a placebo group (n = 15) receiving a supplement not-containing the amino acids. The amino-acid supplement and placebo were given twice/day for 6 weeks. After a wash-out (2 months) from the 1st test, the amino-acid group received the placebo and the placebo group the amino-acid supplement. The body compositions/skin conditions were measured 4 times (day 1 and weeks 2, 4, and 6) in each test. Percentage-change of muscle mass in the amino-acid group increased up to 4 weeks (p = 0.05) and was higher than that in the placebo group (p = 0.09). Skin texture estimated by the image processing of neck skin replica tended to increase in the amino-acid group at 6 weeks compared with that at 0 week, though there was no significant intergroup difference. In conclusion, the young adult women having no fitness habit showed the significant increase of the muscle amount and improvement tendency of the skin texture by the continuous intake of the amino-acid supplement.

Glutamine Metabolism Regulates Proliferation and Lineage Allocation in Skeletal Stem Cells

Skeletal stem cells (SSCs) are postulated to provide a continuous supply of osteoblasts throughout life. However, under certain conditions, the SSC population can become incorrectly specified or is not maintained, resulting in reduced osteoblast formation, decreased bone mass, and in severe cases, osteoporosis. Glutamine metabolism has emerged as a critical regulator of many cellular processes in diverse pathologies. The enzyme glutaminase (GLS) deaminates glutamine to form glutamate-the rate-limiting first step in glutamine metabolism. Using genetic and metabolic approaches, we demonstrate GLS and glutamine metabolism are required in SSCs to regulate osteoblast and adipocyte specification and bone formation. Mechanistically, transaminase-dependent α-ketoglutarate production is critical for the proliferation, specification, and differentiation of SSCs. Collectively, these data suggest stimulating GLS activity may provide a therapeutic approach to expand SSCs in aged individuals and enhance osteoblast differentiation and activity to increase bone mass.

Current Status and Future Prospects of Clinically Exploiting Cancer-specific Metabolism-Why Is Tumor Metabolism Not More Extensively Translated into Clinical Targets and Biomarkers?

Tumor cells exhibit a specialized metabolism supporting their superior ability for rapid proliferation, migration, and apoptotic evasion. It is reasonable to assume that the specific metabolic needs of the tumor cells can offer an array of therapeutic windows as pharmacological disturbance may derail the biochemical mechanisms necessary for maintaining the tumor characteristics, while being less important for normally proliferating cells. In addition, the specialized metabolism may leave a unique metabolic signature which could be used clinically for diagnostic or prognostic purposes. Quantitative global metabolic profiling (metabolomics) has evolved over the last two decades. However, despite the technology’s present ability to measure 1000s of endogenous metabolites in various clinical or biological specimens, there are essentially no examples of metabolomics investigations being translated into actual utility in the cancer clinic. This review investigates the current efforts of using metabolomics as a tool for translation of tumor metabolism into the clinic and further seeks to outline paths for increasing the momentum of using tumor metabolism as a biomarker and drug target opportunity.

Glutamine regulates mitochondrial uncoupling protein 2 to promote glutaminolysis in neuroblastoma cells

Mitochondrial uncoupling protein 2 (UCP2) is highly abundant in rapidly proliferating cells that utilize aerobic glycolysis, such as stem cells, cancer cells, and cells of the immune system. However, the function of UCP2 has been a longstanding conundrum. Considering the strict regulation and unusually short life time of the protein, we propose that UCP2 acts as a "signaling protein" under nutrient shortage in cancer cells. We reveal that glutamine shortage induces the rapid and reversible downregulation of UCP2, decrease of the metabolic activity and proliferation of neuroblastoma cells, that are regulated by glutamine per se but not by glutamine metabolism. Our findings indicate a very rapid (within 1 h) metabolic adaptation that allows the cell to survive by either shifting its metabolism to the use of the alternative fuel glutamine or going into a reversible, more quiescent state. The results imply that UCP2 facilitates glutamine utilization as an energetic fuel source, thereby providing metabolic flexibility during glucose shortage. The targeting UCP2 by drugs to intervene with cancer cell metabolism may represent a new strategy for treatment of cancers resistant to other therapies.

Exogenous glutamine impairs neutrophils migration into infections sites elicited by lipopolysaccharide by a multistep mechanism

Glutamine (GLN) is the most abundant free amino acid in the body, and is considered as a conditionally essential amino acid under stress conditions, acting as an important modulator of the immune response. We here investigated the role of exogenous GLN treatment on leukocyte migration after the onset of endotoxemia and the intracellular mechanisms of GLN actions on neutrophils. Two in vivo models of endotoxemia caused by lipopolysaccharide of Escherichia coli (LPS) injection were carried out in male outbred Balb/C mice 2-3 months old, as follow: (1) LPS (50 μg/kg) was intravenously injected 1 h prior to intravenous injection of GLN (0.75 mg/kg) and samples were collected 2 h later to investigate the role of GLN on the acute lung inflammation; (2) LPS (1 mg/kg) was intraperitoneally injected 1 h prior to intravenous injection of GLN (0.75 mg/kg) and samples were collected 18 h later to measure the effects of GLN on local and later phases of inflammation in the peritoneum. Results showed that GLN administration reduced the number of neutrophils in the inflamed lungs, partially recovery of the reduced number of leukocytes in the blood; reduced adhesion molecules on lung endothelium and on circulating neutrophils. Moreover, GLN treatment diminished the number of neutrophils, levels of chemotactic cytokine CXCL2 in the inflamed peritoneum, and neutrophils collected from the peritoneum of GLN-treated mice presented lower levels of Rho, Rac, and JNK. Together, our data show novel mechanisms involved in the actions of GLN on neutrophils migration.

Glutamine: Metabolism and Immune Function, Supplementation and Clinical Translation

Glutamine is the most abundant and versatile amino acid in the body. In health and disease, the rate of glutamine consumption by immune cells is similar or greater than glucose. For instance, in vitro and in vivo studies have determined that glutamine is an essential nutrient for lymphocyte proliferation and cytokine production, macrophage phagocytic plus secretory activities, and neutrophil bacterial killing. Glutamine release to the circulation and availability is mainly controlled by key metabolic organs, such as the gut, liver, and skeletal muscles. During catabolic/hypercatabolic situations glutamine can become essential for metabolic function, but its availability may be compromised due to the impairment of homeostasis in the inter-tissue metabolism of amino acids. For this reason, glutamine is currently part of clinical nutrition supplementation protocols and/or recommended for immune suppressed individuals. However, in a wide range of catabolic/hypercatabolic situations (e.g., ill/critically ill, post-trauma, sepsis, exhausted athletes), it is currently difficult to determine whether glutamine supplementation (oral/enteral or parenteral) should be recommended based on the amino acid plasma/bloodstream concentration (also known as glutaminemia). Although the beneficial immune-based effects of glutamine supplementation are already established, many questions and evidence for positive in vivo outcomes still remain to be presented. Therefore, this paper provides an integrated review of how glutamine metabolism in key organs is important to cells of the immune system. We also discuss glutamine metabolism and action, and important issues related to the effects of glutamine supplementation in catabolic situations.

Glutaminase inhibitors: a patent review

INTRODUCTION

The kidney-type glutaminase (GLS) controlling the first step of glutamine metabolism is overexpressed in many cancer cells. Targeting inhibition of GLS shows obvious inhibitory effects on cancer cell proliferation. Therefore, extensive research and development of GLS inhibitors have been carried out in industrial and academic institutions over the past decade to address this unmet medical need.

AREAS COVERED

This review covers researches and patent literatures in the field of discovery and development of small molecule inhibitors of GLS for cancer therapy over the past 16 years.

EXPERT OPINION

The detailed ligand-receptor interaction information from their complex structure not only guides the rational drug design, but also facilitates in silico structure-based virtual ligand screening of novel GLS inhibitors. Multi-drug combination administration is of great significance both in terms of safety and efficacy.

MDA-MB-231 and HeLa cells attachment to nanostructured zein surfaces

Detection and characterization of tumor cells are important for cancer diagnosis and therapy. Various surface attachment methods have been proposed for the capture and enumeration of cancer cells, including immunoaffinity and nanostructured surfaces. Zein, a corn protein, has shown good biocompatibility with human liver cells (HL-7702) and mice fibroblasts (NIH3T3). In previous work, it was found that tissue transglutaminase coated on zein substrates enhanced adhesion and spreading of NIH3T3 fibroblast cells. In the present study, cancer cell adhesion to nanostructured zein substrates was investigated. MDA-MB-231 and HeLa cells were used as cancer cell surrogates. MDA-MB-231 cell immobilization was enhanced on zein films, prepared with 80% ethanol, over glass surfaces. The application of tissue transglutaminase onto nanostructured zein substrates further increased cell spreading and adhesion. Cell immobilization increased linearly with the tissue transglutaminase content of the substrate. The effect of substrate morphology was also investigated by seeding cells on electrospun zein fibers. HeLa cell adhesion was also enhanced by zein substrates. This study provided preliminary supporting evidence for developing a zein platform for circulating tumor cells’ immobilization.

Amino Acid Signature in Human Melanoma Cell Lines from Different Disease Stages

Cancer cells rewire metabolism to sustain high proliferation rates. Beside glycolysis and glutaminolysis, amino acids substitute as energy source, feed fatty acid biosynthesis and represent part of the secretome of transformed cells, including melanoma. We have therefore investigated acetate, pyruvate and the amino acid composition of the secretome of human melanoma cells representing the early slow (WM35, WM278, WM793b and VM21) and metastatic fast (A375, 518a2, 6F and WM8) growth phase in order to identify possible signalling components within these profiles. Proliferation assays and a principle component analysis revealed a stringent difference between the fast and slow growing melanoma cells. Moreover, upon inhibition of the mevalonate pathway, glutamic acid and alanine were identified as the central difference in the conditional media. A supplementation of the media with glutamic acid and the combination with alanine significantly accelerated the proliferation, migration and invasion of early stage melanoma cells, but not metastatic cells. Finally, the inhibition of the mevalonate pathway abolished the growth advantage of the melanoma cells in a time dependent manner. Taken together, these data corroborate a stage specific response in growth and aggressiveness to extracellular glutamic acid and alanine, indicative for microenvironmental signalling of individual amino acids.

L-Glutamine in vitro Modulates some Immunomodulatory Properties of Bone Marrow Mesenchymal Stem Cells

Glutamine (GLUT) is a nonessential amino acid that can become conditionally essential under stress conditions, being able to act in the modulation of the immune responses. Mesenchymal stem cells (MSCs) are known to their capability in the modulation of immune responses through cell-cell contact and by the secretion of soluble factors. Considering that GLUT is an immunonutrient and little is known about the influence of GLUT on the capability of MSCs to modulate immune cells, this work aims to investigate how variations in GLUT concentrations in vitro could affect some immunomodulatory properties of MSCs. In order to evaluate the effects of GLUT on MSCs immunomodulatory properties, cell proliferation rates, the expression of NFκB and STAT-3, and the production of IL-1β, IL-6, IL-10, TGF-β and TNF-α by MSCs were assessed. Based on our findings, GLUT at high doses (10 mM) augmented the proliferation of MSCs and modulated immune responses by decreasing levels of pro-inflammatory cytokines, such as IL-1β and IL-6, and by increasing levels of anti-inflammatory cytokines IL-10 and TGF-β. In addition, MSCs cultured in higher GLUT concentrations (10 mM) expressed lower levels of NF-κB and higher levels of STAT-3. Furthermore, conditioned media from MSCs cultured at higher GLUT concentrations (10 mM) reduced lymphocyte and macrophage proliferation, increased IL-10 production by both cells types, and decreased IFN-γ production by lymphocytes. Overall, this study showed that 10 mM of GLUT is able to modify immunomodulatory properties of MSCs.

The redox requirements of proliferating mammalian cells

Cell growth and division require nutrients, and proliferating cells use a variety of sources to acquire the amino acids, lipids, and nucleotides that support macromolecule synthesis. Lipids are more reduced than other nutrients, whereas nucleotides and amino acids are typically more oxidized. Cells must therefore generate reducing and oxidizing (redox) equivalents to convert consumed nutrients into biosynthetic precursors. To that end, redox cofactor metabolism plays a central role in meeting cellular redox requirements. In this Minireview, we highlight the biosynthetic pathways that involve redox reactions and discuss their integration with metabolism in proliferating mammalian cells.

Effects of glutamine, taurine and their association on inflammatory pathway markers in macrophages

The immune system is essential for the control and elimination of infections, and macrophages are cells that act as important players in orchestrating the various parts of the inflammatory/immune response. Amino acids play important role in mediating functionality of the inflammatory response, especially mediating macrophages functions and cytokines production. We investigated the influence of glutamine, taurine and their association on the modulation of inflammatory pathway markers in macrophages. The RAW 264.7 macrophage cell line was cultivated in the presence of glutamine and taurine and proliferation rates, cell viability, cell cycle phases, IL-1α, IL-6, IL-10 and TNF-α as well as H₂O₂ production and the expression of the transcription factor, NFκB, and its inhibitor, IκBα, were evaluated. Our results showed an increase in viable cells and increased proliferation rates of cells treated with glutamine concentrations over 2 mM, as well as cells treated with both glutamine and taurine. The cell cycle showed a higher percentage of cells in the phases S, G2 and M when they were treated with 2 or 10 mM glutamine, or with glutamine and taurine in cells stimulated with lipopolysaccharide. The pNFκB/NFκB showed reduced ratio expression when cells were treated with 10 mM of glutamine or with glutamine in association with taurine. These conditions also resulted in reduced TNF-α, IL-1α and H₂O₂ production, and higher production of IL-10. These findings demonstrate that glutamine and taurine are able to modulate macrophages inflammatory pathways, and that taurine can potentiate the effects of glutamine, illustrating their immunomodulatory properties.