bims-mascan Biomed News
on Mass spectrometry in cancer research
Issue of 2020‒08‒09
twenty-five papers selected by
Giovanny Rodriguez Blanco
University of Edinburgh

  1. Methods Protoc. 2020 Jul 30. pii: E54. [Epub ahead of print]3(3):
      Stable isotopic tracer analysis is a technique used to determine carbon or nitrogen atom incorporation into biological systems. A number of mass spectrometry based approaches have been developed for this purpose, including high-resolution tandem mass spectrometry (HR-LC-MS/MS), selected reaction monitoring (SRM) and parallel reaction monitoring (PRM). We have developed an approach for analyzing untargeted metabolomic and lipidomic datasets using high-resolution mass spectrometry with polarity switching and implemented our approach in the open-source R script IsoSearch and in Scaffold Elements software. Using our strategy, which requires an unlabeled reference dataset and isotope labeled datasets across various biological conditions, we traced metabolic isotopomer alterations in breast cancer cells (MCF-7) treated with the metabolic drugs 2-deoxy-glucose, 6-aminonicotinamide, compound 968, and rapamycin. Metabolites and lipids were first identified by the commercial software Scaffold Elements and LipidSearch, then IsoSearch successfully profiled the 13C-isotopomers extracted metabolites and lipids from 13C-glucose labeled MCF-7 cells. The results interpreted known models, such as glycolysis and pentose phosphate pathway inhibition, but also helped to discover new metabolic/lipid flux patterns, including a reactive oxygen species (ROS) defense mechanism induced by 6AN and triglyceride accumulation in rapamycin treated cells. The results suggest the IsoSearch/Scaffold Elements platform is effective for studying metabolic tracer analysis in diseases, drug metabolism, and metabolic engineering for both polar metabolites and non-polar lipids.
    Keywords:  13C; 15N; LC-MS/MS; cancer; cell culture; flux; glucose; glutamine; high resolution; isotopic tracer analysis; lipidomics; liquid chromatography; mass spectrometry; metabolism; metabolomics; polarity switching; stable isotope labeling
  2. Cell Metab. 2020 Jul 30. pii: S1550-4131(20)30367-3. [Epub ahead of print]
      Cancer relapse begins when malignant cells pass through the extreme metabolic bottleneck of stress from chemotherapy and the byproducts of the massive cell death in the surrounding region. In acute myeloid leukemia, complete remissions are common, but few are cured. We tracked leukemia cells in vivo, defined the moment of maximal response following chemotherapy, captured persisting cells, and conducted unbiased metabolomics, revealing a metabolite profile distinct from the pre-chemo growth or post-chemo relapse phase. Persisting cells used glutamine in a distinctive manner, preferentially fueling pyrimidine and glutathione generation, but not the mitochondrial tricarboxylic acid cycle. Notably, malignant cell pyrimidine synthesis also required aspartate provided by specific bone marrow stromal cells. Blunting glutamine metabolism or pyrimidine synthesis selected against residual leukemia-initiating cells and improved survival in leukemia mouse models and patient-derived xenografts. We propose that timed cell-intrinsic or niche-focused metabolic disruption can exploit a transient vulnerability and induce metabolic collapse in cancer cells to overcome chemoresistance.
    Keywords:  acute myeloid leukemia; aspartate; bone marrow niche; cell metabolism; chemotherapy; glutamine; mouse models; patient-derived xenografts; pyrimidine synthesis; tumor microenvironment
  3. Nat Metab. 2020 Aug 03.
      Cancer cells have high demands for non-essential amino acids (NEAAs), which are precursors for anabolic and antioxidant pathways that support cell survival and proliferation. It is well-established that cancer cells consume the NEAA cysteine, and that cysteine deprivation can induce cell death; however, the specific factors governing acute sensitivity to cysteine starvation are poorly characterized. Here, we show that that neither expression of enzymes for cysteine synthesis nor availability of the primary precursor methionine correlated with acute sensitivity to cysteine starvation. We observed a strong correlation between efflux of the methionine-derived metabolite methylthioadenosine (MTA) and sensitivity to cysteine starvation. MTA efflux results from genetic deletion of methylthioadenosine phosphorylase (MTAP), which is frequently deleted in cancers. We show that MTAP loss upregulates polyamine metabolism which, concurrently with cysteine withdrawal, promotes elevated reactive oxygen species and prevents cell survival. Our results reveal an unexplored metabolic weakness at the intersection of polyamine and cysteine metabolism.
  4. Analyst. 2020 Aug 06.
      Triacylglycerol (TG) is a class of lipids that is responsible for energy storage and cell metabolism in biological systems; it is found in relatively high abundances in biological fluids such as human plasma. Due to structural complexity, analyzing TGs using shotgun lipidomic approaches is challenging because of the presence of multiple fatty acyl compositional isomers. In this work, reversed-phase liquid chromatography (RPLC) was used for separation of TG species due to the capability of separating lipids based on fatty acyl chain lengths and degrees of unsaturation. RPLC alone does not provide structurally informative information for the location of carbon-carbon double-bonds (C[double bond, length as m-dash]Cs) without using synthesized standards that correspond to each species analyzed. The Paternò-Büchi (PB) reaction was employed online to confidently characterize the location of C[double bond, length as m-dash]Cs within lipid species via photo-initiated modification of the alkene group with acetone, which was later subjected to electrospray ionization (ESI) and tandem mass spectrometry (MS/MS) to form signature fragmentation peaks. This online RPLC-PB-MS/MS system was able to distinguish fatty acyl level and C[double bond, length as m-dash]C level isomeric species. The systems allowed for the identification of 46 TG molecular species in human plasma with confident C[double bond, length as m-dash]C location assignment in fatty acyls at a limit of identification of 50 nM.
  5. Electrophoresis. 2020 Aug 03.
      Currently, feature annotation remains one of the main challenges in untargeted metabolomics. In this context, the information provided by high-resolution mass spectrometry (HRMS) in addition to accurate mass can improve the quality of metabolite annotation, and MS/MS fragmentation patterns are widely used. Accurate mass and a separation index, such as retention time or effective mobility (μeff ), in chromatographic and electrophoretic approaches, respectively, must be used for unequivocal metabolite identification. The possibility of measuring collision cross section (CCS) values by using ion mobility (IM) is becoming increasingly popular in metabolomic studies thanks to the new generation of IM mass spectrometers. Based on their similar separation mechanisms involving electric field and the size of the compounds, the complementarity of DT CCSN2 and μeff needs to be evaluated. In this study, a comparison of DT CCSN2 and μeff was achieved in the context of feature identification ability in untargeted metabolomics by capillary zone electrophoresis (CZE) coupled with HRMS. This study confirms the high correlation of DT CCSN2 with the mass of the studied metabolites as well as the orthogonality between accurate mass and μeff , making this combination particularly interesting for the identification of several endogenous metabolites. The use of IM-MS remains of great interest for facilitating the annotation of neutral metabolites present in the electroosmotic flow (EOF) that are poorly or not separated by CZE. This article is protected by copyright. All rights reserved.
    Keywords:  Cross collision section; Effective mobility; Features annotation; Ion mobility; Metabolomics
  6. Redox Biol. 2020 Aug 01. pii: S2213-2317(20)30862-4. [Epub ahead of print]36 101657
      Metabolic reprogramming is a hallmark of cancer cells. In Waldenstrom Macroglobulinemia (WM), the infiltration of IgM-secreting lymphoplamacytic cells into the bone marrow (BM) could shift the homeostasis of proteins and metabolites towards a permissive niche for tumor growth. Here, we investigated whether alerted metabolic pathways contribute to the pathobiology of WM and whether the cytokine composition of the BM promotes such changes. Metabolomics analysis on WM patients and normal donors' serum samples revealed a total of 75 metabolites that were significantly altered between two groups. While these metabolites belonged to amino acids, glucose, glutathione and lipid metabolism pathways, the highest number of the differentially expressed metabolites belonged to glutathione metabolism. Proteomics analysis and immunohistochemical staining both confirmed the increased protein levels mediating glutathione metabolism, including GCLC, MT1X, QPCT and GPX3. Moreover, treatment with IL-6 and IL-21, cytokines that induce WM cell proliferation and IgM secretion, increased gene expression of the amino acid transporters mediating glutathione metabolism, including ASCT2, SLC7A11 and 4F2HC, indicating that cytokines in the WM BM could modulate glutathione metabolism. Glutathione synthesis inhibition using Buthionine sulphoximine (BSO) significantly reduced WM cells proliferation in vitro, accompanied with decreased NFκB-p65 and MAPK-p38 phosphorylation. Moreover, BSO treatment significantly reduced the tumor growth rate in a WM xenograft model, further highlighting the role of glutathione metabolism in promoting tumor growth and proliferation. In summary, our data highlight a central role for glutathione metabolism in WM pathobiology and indicate that intervening with the metabolic processes could be a potential therapy for WM patients.
    Keywords:  Glutathione; Metabolism; Waldenstrom Macroglobulinemia
  7. J Lipid Res. 2020 Aug 04. pii: jlr.RA120000899. [Epub ahead of print]
      Non-small cell lung cancer (NSCLC) is a leading cause of cancer-related deaths. Whilst mutations in Kras and over-expression of Myc are commonly found in patients, the role of altered lipid metabolism in lung cancer and its interplay with oncogenic Myc is poorly understood. Here we use a transgenic mouse model of Kras-driven lung adenocarcinoma with reversible activation of Myc, in combination with surface analysis lipid profiling of lung tumours and transcriptomics, to study the effect of Myc activity on cholesterol homeostasis. Our findings reveal that activation of Myc leads to the accumulation of cholesteryl esters (CE), stored in lipid droplets. Subsequent Myc deactivation leads to further increases in CEs, in contrast to tumours in which Myc was never activated. Gene expression analysis linked cholesterol transport and storage pathways to Myc activity. Our results suggest that increased Myc activity is associated with increased cholesterol influx, reduced efflux and accumulation of CE-rich lipid droplets in lung tumours. Targeting cholesterol homeostasis is proposed as a promising avenue to explore for novel treatments of lung cancer, with diagnostic and stratification potential in human NSCLC.
    Keywords:  Cancer; Cholesterol; Lipidomics; Lung; Mass spectrometry; adenocarcinoma; cholesteryl ester; lipid metabolism; liquid extraction surface analysis; mass spectrometry
  8. Front Mol Biosci. 2020 ;7 153
      Branched chain fatty acids perform very important functions in human diet and drug metabolism. they cannot be metabolized in mitochondria and are instead processed and degraded in peroxisomes due to the presence of methyl groups on the carbon chains. Oxidative degradation pathways for lipids include α- and β-oxidation and several pathways. In all metabolic pathways, α-methyl acyl-CoA racemase (AMACR) plays an essential role by regulating the metabolism of lipids and drugs. AMACR regulates β-oxidation of branched chain lipids in peroxisomes and mitochondria and promotes chiral reversal of 2-methyl acids. AMACR defects cause sensory-motor neuronal and liver abnormalities in humans. These phenotypes are inherited and are caused by mutations in AMACR. In addition, AMACR has been found to be overexpressed in prostate cancer. In addition, the protein levels of AMACR have increased significantly in many types of cancer. Therefore, AMACR may be an important marker in tumors. In this review, a comprehensive overview of AMACR studies in human disease will be described.
    Keywords:  AMACR; branched-chain fatty acid; cancer development; lipid metabolism; β-oxidation
  9. Angew Chem Int Ed Engl. 2020 Aug 02.
      Ambient ionization based on liquid extraction is widely used in mass spectrometry imaging (MSI) of molecules in biological samples. The development of nanospray desorption electrospray ionization (nano-DESI) has enabled the robust imaging of tissue sections with high spatial resolution. However, the fabrication of the nano-DESI probe is challenging, which limits its dissemination to the broader scientific community. Herein, we describe the design and performance of an integrated microfluidic probe (iMFP) for nano-DESI MSI. The glass iMFP fabricated using photolithography, wet etching, and polishing shows comparable performance to the capillary-based nano-DESI MSI in terms of stability and sensitivity; the spatial resolution of better than 25 µm was obtained in these first proof-of-principle experiments. The iMFP is easy to operate and align in front of a mass spectrometer, which will facilitate broader use of liquid extraction-based MSI in biological research, drug discovery, and clinical studies.
    Keywords:  Mass Spectrometry Imaging; integrated microfluidic probe; lipids; mouse brain; mouse uterine sections
  10. Prostaglandins Leukot Essent Fatty Acids. 2020 Jun 26. pii: S0952-3278(20)30114-9. [Epub ahead of print]160 102156
      Cystic fibrosis (CF) is a recessively inherited fatal disease that is the subject of extensive research and ongoing development of therapeutics targeting the defective protein, cystic fibrosis transmembrane conductance regulator (CFTR). Despite progress, the link between CFTR and clinical symptoms is incomplete. The severe CF phenotypes are associated with a deficiency of linoleic acid, which is the precursor of arachidonic acid. The release of arachidonic acid from membranes via phospholipase A2 is the rate-limiting step for eicosanoid synthesis and is increased in CF, which contributes to the observed inflammation. A potential deficiency of docosahexaenoic acid may lead to decreased levels of specialized pro-resolving mediators. This pathophysiology may contribute to an early and sterile inflammation, mucus production, and to bacterial colonization, which further increases inflammation and potentiates the clinical symptoms. Advances in lipid technology will assist in elucidating the role of lipid metabolism in CF, and stimulate therapeutic modulations of inflammation.
    Keywords:  Annexin 1; Arachidonic acid; Docosahexaenoic acid; Eicosanoids; Linoleic acid; Mucus
  11. Cancers (Basel). 2020 Aug 03. pii: E2147. [Epub ahead of print]12(8):
      A major hallmark of cancer is the metabolic reprogramming of cancer cells to fuel tumor growth and proliferation. Various plant-derived bioactive compounds efficiently target the metabolic vulnerabilities of cancer cells and exhibit potential as emerging therapeutic agents. Due to their safety and common use as dietary components, they are also ideal for cancer prevention. However, to render their use as efficient as possible, the mechanism of action of these phytochemicals needs to be well characterized. Stable isotope tracing is an essential technology to study the molecular mechanisms by which nutraceuticals modulate and target cancer metabolism. The use of positionally labeled tracers as exogenous nutrients and the monitoring of their downstream metabolites labeling patterns enable the analysis of the specific metabolic pathway activity, via the relative production and consumption of the labeled metabolites. Although stable isotope tracing metabolomics is a powerful tool to investigate the molecular activity of bioactive compounds as well as to design synergistic nutraceutical combinations, this methodology is still underutilized. This review aims to investigate the research efforts and potentials surrounding the use of stable isotope tracing metabolomics to examine the metabolic alterations mediated by bioactive compounds in cancer.
    Keywords:  bioactive compounds; cancer metabolism; cancer prevention; metabolic pathways; natural products; stable isotope tracing
  12. FASEB J. 2020 Aug 06.
      Cancer cells rely on several metabolic pathways such as lipid metabolism to meet the increase in energy demand, cell division, and growth and successfully adapt to challenging environments. Fatty acid synthesis is therefore commonly enhanced in many cancer cell lines. Thus, relevant efforts are being made by the scientific community to inhibit the enzymes involved in lipid metabolism to disrupt cancer cell proliferation. We review the rapidly expanding body of inhibitors that target lipid metabolism, their side effects, and current status in clinical trials as potential therapeutic approaches against cancer. We focus on their molecular, biochemical and structural properties, selectivity and effectiveness and discuss their potential role as antitumor drugs.
    Keywords:  cancer drugs; lipid metabolism; lipogenic enzyme inhibitors
  13. Nat Cell Biol. 2020 Aug;22(8): 973-985
      Autophagy is a homeostatic process with multiple functions in mammalian cells. Here, we show that mammalian Atg8 proteins (mAtg8s) and the autophagy regulator IRGM control TFEB, a transcriptional activator of the lysosomal system. IRGM directly interacted with TFEB and promoted the nuclear translocation of TFEB. An mAtg8 partner of IRGM, GABARAP, interacted with TFEB. Deletion of all mAtg8s or GABARAPs affected the global transcriptional response to starvation and downregulated subsets of TFEB targets. IRGM and GABARAPs countered the action of mTOR as a negative regulator of TFEB. This was suppressed by constitutively active RagB, an activator of mTOR. Infection of macrophages with the membrane-permeabilizing microbe Mycobacterium tuberculosis or infection of target cells by HIV elicited TFEB activation in an IRGM-dependent manner. Thus, IRGM and its interactors mAtg8s close a loop between the autophagosomal pathway and the control of lysosomal biogenesis by TFEB, thus ensuring coordinated activation of the two systems that eventually merge during autophagy.
  14. Mol Cell Proteomics. 2020 Aug 05. pii: mcp.RA120.002189. [Epub ahead of print]
      Amino acid hydroxylation is a common post-translational modification, which generally regulates protein interactions or adds a functional group that can be further modified. Such hydroxylation is currently considered irreversible, necessitating the degradation and re-synthesis of the entire protein to reset the modification. Here we present evidence that the cellular machinery can reverse FIH-mediated asparagine hydroxylation on intact proteins. These data suggest that asparagine hydroxylation is a flexible and dynamic post-translational modification akin to modifications involved in regulating signalling networks, such as phosphorylation, methylation and ubiquitylation.
    Keywords:  Affinity proteomics; Mass Spectrometry; Post-translational modifications*; SILAC; Signal Transduction*; factor-inhibiting-HIF; hydroxylation
  15. Biol Res Nurs. 2020 Aug 07. 1099800420942900
      BACKGROUND: Obesity plays a major role in the development of insulin resistance (IR) and diabetes (T2DM). Increased adipose tissue (AT) is particularly of interest because it activates a chronic inflammatory response in adipocytes and other tissues. AT plays key endocrine and metabolic functions, acting in the regulation of insulin sensitivity and energy homeostasis. Additionally, it can be easily collected during bariatric surgery. The purpose of this pilot study was to explore the potential differences in AT metabolism, through comparing the untargeted metabolomic profiles of diabetic and non-diabetic obese patients undergoing bariatric surgery.METHODS: For this exploratory study, samples were collected from 17 subjects. Subcutaneous AT (SAT) samples from obese-diabetic (n = 8) and Obese-non-Diabetic (n = 9) subjects were obtained from the Human Metabolic Tissue Bank. Untargeted metabolomic profiling was performed by Metabolon® Inc. Statistical analysis was performed using the MetaboAnalyst 4.0 platform.
    RESULTS: Among the 421 metabolites identified and analyzed there were no significant differences between the Obese-Diabetics and the Obese-non-Diabetics. Small changes were observed by fold change analysis mainly in lipid (n = 12; e.g. NEFAs) and amino acid (n = 8; e.g. BCAAs) metabolic pathways. Dysregulation of these metabolites has been associated with IR and other T2DM-related pathophysiological processes.
    CONCLUSION: Obesity may influence SAT metabolism masking T2DM-dependent dysregulation. Better understanding the metabolic differences within SAT in diabetic populations may help identify potential biomarkers for diagnosis and monitoring of T2DM in patients undergoing bariatric surgery.
    Keywords:  diabetes (T2DM); insulin resistance (IR), bariatric surgery; obesity; subcutaneous adipose tissue (SAT); untargeted metabolomics
  16. Analyst. 2020 Aug 06.
      Clinical metabolic phenotyping employs metabolomics and lipidomics to detect and measure hundreds to thousands of metabolites and lipids within human samples. This approach aims to identify metabolite and lipid changes between phenotypes (e.g. disease status) that aid understanding of biochemical mechanisms driving the phenotype. Sample preparation is a critical step in clinical metabolic phenotyping: it must be reproducible and give a high extraction yield of metabolites and lipids, and in high-throughput studies it needs to be rapid. Here, we assessed the extraction of polar metabolites from human urine and polar metabolites and lipids from human plasma for analysis by ultra-high-performance liquid chromatography-mass spectrometry (UHPLC-MS) metabolomics and lipidomics. We evaluated several monophasic (urine and plasma) and biphasic (plasma) extractions, and we also tested alterations to (a) solvent-biofluid incubation time and temperature during monophasic extraction, and (b) phase partitioning time during biphasic extraction. Extracts were analysed by three UHPLC-MS assays: (i) hydrophilic interaction chromatography (HILIC) for urine and plasma, (ii) C18 aqueous reversed phase for urine, and (iii) C18 reversed phase for plasma lipids, and the yield and reproducibility of each method was assessed. We measured UHPLC-MS injection reproducibility as well as sample preparation reproducibility to assess sample solvent composition compatibility with UHPLC-MS and to pinpoint the origin of variance within the methods. For HILIC UHPLC-MS plasma and urine analysis, monophasic 50 : 50 methanol : acetonitrile had the most detected putatively-identified polar metabolites with high method reproducibility. This method had the highest lipid yield for plasma extracts analysed by the HILIC method. If lipid removal from the plasma polar HILIC extract is required, then the biphasic methanol/chloroform/water method is recommended. For C18 (aqueous) UHPLC-MS urine analysis, 50 : 50 methanol : water had high reproducibility and yield. For C18 UHPLC-MS plasma lipidomics, monophasic 100% isopropanol had the highest detection response of all annotated lipid classes with high reproducibility. Increasing monophasic incubation time and temperature had little benefit on metabolite and lipid yield and reproducibility for all methods.
  17. J Chromatogr B Analyt Technol Biomed Life Sci. 2020 Jul 30. pii: S1570-0232(20)30348-2. [Epub ahead of print]1154 122291
      Bempedoic acid, a new therapeutic for treatment of hypercholesterolemia, inhibits hepatic ATP-citrate lyase in the cholesterol synthesis pathway after its conjugation with coenzyme A. Sensitive and selective methods were required to study the pharmacokinetic behavior of bempedoic acid and its active 8-keto metabolite in clinical studies. A mixed mode anion exchange extraction on 96-well plates was developed to favor high, selective recoveries of these dicarboxylic acids from urine or plasma. Adsorptive losses in urine led to inaccurate measurements unless samples were acidified and diluted with isopropanol prior to any specimen transfers. Tandem mass spectrometry with negative ion electrospray ionization permitted lower limits of measurement of 20 and 10 ng/mL for the drug and metabolite in either matrix. The methods were validated to current regulatory standards and have been the basis for pharmacokinetic measurements in 26 clinical studies involving over 15,000 samples.
    Keywords:  Acyl glucuronides; Bempedoic acid; ESP15228; ETC-1002; Ezetimibe; Plasma; Statins; Urine
  18. Cancers (Basel). 2020 Aug 04. pii: E2157. [Epub ahead of print]12(8):
      Dedifferentiated liposarcoma (DDLPS) is an aggressive mesenchymal cancer marked by amplification of MDM2, an inhibitor of the tumor suppressor TP53. DDLPS patients with higher MDM2 amplification have lower chemotherapy sensitivity and worse outcome than patients with lower MDM2 amplification. We hypothesized that MDM2 amplification levels may be associated with changes in DDLPS metabolism. Six patient-derived DDLPS cell line models were subject to comprehensive metabolomic (Metabolon) and lipidomic (SCIEX 5600 TripleTOF-MS) profiling to assess associations with MDM2 amplification and their responses to metabolic perturbations. Comparing metabolomic profiles between MDM2 higher and lower amplification cells yielded a total of 17 differentially abundant metabolites across both panels (FDR < 0.05, log2 fold change < 0.75), including ceramides, glycosylated ceramides, and sphingomyelins. Disruption of lipid metabolism through statin administration resulted in a chemo-sensitive phenotype in MDM2 lower cell lines only, suggesting that lipid metabolism may be a large contributor to the more aggressive nature of MDM2 higher DDLPS tumors. This study is the first to provide comprehensive metabolomic and lipidomic characterization of DDLPS cell lines and provides evidence for MDM2-dependent differential molecular mechanisms that are critical factors in chemoresistance and could thus affect patient outcome.
    Keywords:  MDM2; atorvastatin; chemosensitivity; dedifferentiated liposarcoma (DDLPS); lipidomics; metabolomics; sphingolipid metabolism
  19. NAR Cancer. 2020 Jun;2(2): zcaa010
      Mechanistic understanding of hypoxia-responsive signaling pathways provides important insights into oxygen- and metabolism-dependent cellular phenotypes in diseases. Using SILAC-based quantitative proteomics, we provided a quantitative map identifying over 6300 protein groups in response to hypoxia in prostate cancer cells and identified both canonical and novel cellular networks dynamically regulated under hypoxia. Particularly, we identified SDE2, a DNA stress response modulator, that was significantly downregulated by hypoxia, independent of HIF (hypoxia-inducible factor) transcriptional activity. Mechanistically, hypoxia treatment promoted SDE2 polyubiquitination and degradation. Such regulation is independent of previously identified Arg/N-end rule proteolysis or the ubiquitin E3 ligase, CDT2. Depletion of SDE2 increased cellular sensitivity to DNA damage and inhibited cell proliferation. Interestingly, either SDE2 depletion or hypoxia treatment potentiated DNA damage-induced PCNA (proliferating cell nuclear antigen) monoubiquitination, a key step for translesion DNA synthesis. Furthermore, knockdown of SDE2 desensitized, while overexpression of SDE2 protected the hypoxia-mediated regulation of PCNA monoubiquitination upon DNA damage. Taken together, our quantitative proteomics and biochemical study revealed diverse hypoxia-responsive pathways that strongly associated with prostate cancer tumorigenesis and identified the functional roles of SDE2 and hypoxia in regulating DNA damage-induced PCNA monoubiquitination, suggesting a possible link between hypoxic microenvironment and the activation of error-prone DNA repair pathway in tumor cells.
  20. Metabolites. 2020 Jul 31. pii: E314. [Epub ahead of print]10(8):
      Metabolic reprogramming is increasingly recognised as one of the defining hallmarks of tumorigenesis. There is compelling evidence to suggest that endometrial cancer develops and progresses in the context of profound metabolic dysfunction. Whilst the incidence of endometrial cancer continues to rise in parallel with the global epidemic of obesity, there are, as yet, no validated biomarkers that can aid risk prediction, early detection, prognostic evaluation or surveillance. Advances in high-throughput technologies have, in recent times, shown promise for biomarker discovery based on genomic, transcriptomic, proteomic and metabolomic platforms. Metabolomics, the large-scale study of metabolites, deals with the downstream products of the other omics technologies and thus best reflects the human phenotype. This review aims to provide a summary and critical synthesis of the existing literature with the ultimate goal of identifying the most promising metabolite biomarkers that can augment current endometrial cancer diagnostic, prognostic and recurrence surveillance strategies. Identified metabolites and their biochemical pathways are discussed in the context of what we know about endometrial carcinogenesis and their potential clinical utility is evaluated. Finally, we underscore the challenges inherent in metabolomic biomarker discovery and validation and provide fresh perspectives and directions for future endometrial cancer biomarker research.
    Keywords:  biomarkers; endometrial cancer; metabolic profiling; metabolomics
  21. Biochim Biophys Acta Mol Cell Biol Lipids. 2020 Aug 04. pii: S1388-1981(20)30180-3. [Epub ahead of print] 158788
      Adipose tissue exerts multiple vital functions that critically maintain energy balance, including storing and expending energy, as well as secreting factors that systemically modulate nutrient metabolism. Since lipids are the major constituents of the adipocytes, it is unsurprising that the lipid composition of these cells plays a critical role in maintaining their functions and communicating with other organs and cells. In both positive and negative energy balance conditions, lipids and free fatty acids secreted from adipocytes exert either beneficial or detrimental effects in other tissues, such as the liver, pancreas and muscle. The way the adipocytes communicate with other organs tightly depends on the nature of their lipidome composition. Notwithstanding, the lipidome composition of the adipocytes is affected by physiological factors such as adipocyte type, gender and age, but also by environmental cues such as diet composition, thermal stress and physical activity. Here we provide an updated overview on how the adipose tissue lipidome profile is shaped by different physiological and environmental factors and how these changes impact the way the adipocytes regulate whole-body energy metabolism.
    Keywords:  adipocytes; lipids; lipokine; thermogenesis
  22. Life Sci. 2020 Aug 04. pii: S0024-3205(20)30936-X. [Epub ahead of print] 118184
      Autophagy is an essential mechanism of cellular degradation, a way to protect the cells under stress conditions, such as deprivation of nutrients, growth factors and cellular damage. However, in normal physiology autophagy plays a significant role in cancer cells. Current research is in progress to understand how autophagy and cancer cells go hand in hand to support cancer cell progression. The important aspect in cancer and autophagy is the interdependence of autophagy in the survival and progression of cancer cells. Autophagy is known to be a major cause of chemotherapeutic resistance in various cancer cell types. Therefore, inhibition of autophagy as an effective therapeutic approach is being actively studied and tested in clinical studies. Multiple metabolic pathways are linked with autophagy that could potentially be a significant target for chemotherapeutic strategy. The comprehension of the interconnection of autophagy with cancer metabolism can pave a novel findings for effective combinatorial therapeutic strategies.
    Keywords:  Autophagy; Cancer; Glycolysis; Metabolism
  23. Int J Biol Sci. 2020 ;16(13): 2308-2322
      Perturbation in lipid homeostasis is one of the major bottlenecks in metabolic diseases, especially Non-alcoholic Fatty Liver Disease (NAFLD), which has emerged as a leading global cause of chronic liver disease. The bile acids (BAs) and their derivatives exert a variety of metabolic effects through complex and intertwined pathways, thus becoming the attractive target for metabolic syndrome treatment. To modulate the lipid homeostasis, the role of BAs, turn out to be paramount as it is essential for the absorption, transport of dietary lipids, regulation of metabolic enzymes and transporters that are essential for lipid modulation, flux, and excretion. The synthesis and transport of BAs (conjugated and unconjugated) is chiefly controlled by nuclear receptors and the uptake of long-chain fatty acids (LCFA) and BA conjugation via transporters. Among them, from in-vivo studies, farnesoid X receptor (FXR) and liver-specific fatty acid transport protein 5 (FATP5) have shown convincing evidence for their key roles in lipid homeostasis and reversal of fatty liver disease substantially. BAs have a wider range of biological effects as they are identified as modulators for FXR and FATP5 both and therefore hold a significant promise for altering the lipid content in the treatment of a metabolic disorder. BAs also have received noteworthy interest in drug delivery research due to its peculiar physicochemical properties and biocompatibility. Here, we are highlighting the connecting possibility of BAs as an agonist for FXR and antagonist for FATP5, paving an avenue to target them for designing synthetic small molecules for lipid homeostasis.
    Keywords:  Bile acids; FATP5; FXR; Fatty liver diseases; Triglycerides; cyp7a1
  24. Biochim Biophys Acta Mol Basis Dis. 2020 Jul 31. pii: S0925-4439(20)30256-8. [Epub ahead of print] 165908
      Circadian misalignment induced by a high-fat diet (HFD) increases the risk of metabolic diseases. Methionine restriction (MR) is known to have the potential of alleviating obesity by improving insulin sensitivity. However, the role of the circadian clock in mediating the effects of MR on obesity-related metabolic disorders remains unclear. Ten-week-old male C57BL/6J mice were fed with a low-fat diet (LFD) or a HFD for 4 wk, followed with a full diet (0.86 % methionine, w/w) or a methionine-restricted diet (0.17 % methionine, w/w) for 8 wk. Our results showed that MR attenuated insulin resistance triggered by HFD, especially at ZT12. Moreover, MR led to a time-specific enhancement of the expression of FGF21 and activated the AMPK/PGC-1α signaling. Notably, MR upregulated the cyclical levels of cholic acid (CA) and chenodeoxycholic acid (CDCA), and downregulated the cyclical level of deoxycholic acid (DCA) in the dark phase. MR restored the HFD-disrupted cyclical fluctuations of lipidolysis genes and BAs synthetic genes and improved the circulating lipid profile. Also, MR improved the expressions of clock-controlled genes (CCGs) in the liver and the brown adipose tissue throughout one day. In conclusion, MR exhibited the lipid-lowering effects on HFD-induced obesity and restored the diurnal metabolism of lipids and BAs, which could be partly explained by improving the expression of CCGs. These findings suggested that MR could be a potential nutritional intervention for attenuating obesity-induced metabolic misalignment.
    Keywords:  bile acid metabolism; circadian clock; high-fat diet; lipid metabolism; methionine restriction
  25. Bioanalysis. 2020 Aug 06.
      Aim: 2-Hydroxyglutarate (2-HG) is a target engagement biomarker in patients after treatment with inhibitors of mutated isocitrate dehydrogenase (mIDH). Accurate measurement of 2-HG is critical for monitoring the inhibition effectiveness of the inhibitors. Materials & methods: Human plasma samples were spiked with stable isotope labelled internal standard, processed by protein precipitation, and analyzed using LC-MS/MS. This method was validated following regulatory guidance and has been successfully applied in a clinical study for mIDH inhibition. Results: An LC-MS/MS method with a surrogate analyte approach was developed and validated to measure 2-HG in human plasma with acceptable intra- and inter-assay accuracy and precision. Conclusion: A sensitive and robust LC-MS/MS method was developed and validated for measuring 2-HG in human plasma.
    Keywords:  2-HG; 2-hydroxyglutarate; IDH inhibitor; LC–MS/MS; endogenous biomarkers; human plasma; small molecule; surrogate analyte; validation