Myeloid-derived suppressor cell mitochondrial fitness governs chemotherapeutic efficacy in hematologic malignancies

Myeloid derived suppressor cells (MDSCs) are key regulators of immune responses and correlate with poor outcomes in hematologic malignancies. Here, we identify that MDSC mitochondrial fitness controls the efficacy of doxorubicin chemotherapy in a preclinical lymphoma model. Mechanistically, we show that triggering STAT3 signaling via β2-adrenergic receptor (β2-AR) activation leads to improved MDSC function through metabolic reprograming, marked by sustained mitochondrial respiration and higher ATP generation which reduces AMPK signaling, altering energy metabolism. Furthermore, induced STAT3 signaling in MDSCs enhances glutamine consumption via the TCA cycle. Metabolized glutamine generates itaconate which downregulates mitochondrial reactive oxygen species via regulation of Nrf2 and the oxidative stress response, enhancing MDSC survival. Using β2-AR blockade, we target the STAT3 pathway and ATP and itaconate metabolism, disrupting ATP generation by the electron transport chain and decreasing itaconate generation causing diminished MDSC mitochondrial fitness. This disruption increases the response to doxorubicin and could be tested clinically.

CD8+ T cell metabolic flexibility elicited by CD28-ARS2 axis-driven alternative splicing of PKM supports antitumor immunity

Metabolic flexibility has emerged as a critical determinant of CD8+ T-cell antitumor activity, yet the mechanisms driving the metabolic flexibility of T cells have not been determined. In this study, we investigated the influence of the nuclear cap-binding complex (CBC) adaptor protein ARS2 on mature T cells. In doing so, we discovered a novel signaling axis that endows activated CD8+ T cells with flexibility of glucose catabolism. ARS2 upregulation driven by CD28 signaling reinforced splicing factor recruitment to pre-mRNAs and affected approximately one-third of T-cell activation-induced alternative splicing events. Among these effects, the CD28-ARS2 axis suppressed the expression of the M1 isoform of pyruvate kinase in favor of PKM2, a key determinant of CD8+ T-cell glucose utilization, interferon gamma production, and antitumor effector function. Importantly, PKM alternative splicing occurred independently of CD28-driven PI3K pathway activation, revealing a novel means by which costimulation reprograms glucose metabolism in CD8+ T cells.

Metabolic reprogramming driven by EZH2 inhibition depends on cell-matrix interactions

EZH2 (Enhancer of Zeste Homolog 2), a subunit of Polycomb Repressive Complex 2 (PRC2), catalyzes the trimethylation of histone H3 at lysine 27 (H3K27me3), which represses expression of genes. It also has PRC2-independent functions, including transcriptional coactivation of oncogenes, and is frequently overexpressed in lung cancers. Clinically, EZH2 inhibition can be achieved with the FDA-approved drug EPZ-6438 (tazemetostat). To realize the full potential of EZH2 blockade, it is critical to understand how cell-cell/cell-matrix interactions present in 3D tissue and cell culture systems influences this blockade in terms of growth-related metabolic functions. Here, we show that EZH2 suppression reduced growth of human lung adenocarcinoma A549 cells in 2D cultures but stimulated growth in 3D cultures. To understand the metabolic underpinnings, we employed [13C6]-glucose stable isotope-resolved metabolomics to determine the effect of EZH2 suppression on metabolic networks in 2D versus 3D A549 cultures. The Krebs cycle, neoribogenesis, γ-aminobutyrate metabolism, and salvage synthesis of purine nucleotides were activated by EZH2 suppression in 3D spheroids but not in 2D cells, consistent with the growth effect. Using simultaneous 2H7-glucose + 13C5,15N2-Gln tracers and EPZ-6438 inhibition of H3 trimethylation, we delineated the effects on the Krebs cycle, γ-aminobutyrate metabolism, gluconeogenesis, and purine salvage to be PRC2-dependent. Furthermore, the growth/metabolic effects differed for mouse Matrigel versus self-produced A549 extracellular matrix. Thus, our findings highlight the importance of the presence and nature of extracellular matrix in studying the function of EZH2 and its inhibitors in cancer cells for modeling the in vivo outcomes.

Cyclin D1 extensively reprograms metabolism to support biosynthetic pathways in hepatocytes

Cell proliferation requires metabolic reprogramming to accommodate biosynthesis of new cell components, and similar alterations occur in cancer cells. However, the mechanisms linking the cell cycle machinery to metabolism are not well defined. Cyclin D1, along with its main partner cyclin-dependent kinase 4 (Cdk4), is a pivotal cell cycle regulator and driver oncogene that is overexpressed in many cancers. Here, we examine hepatocyte proliferation to define novel effects of cyclin D1 on biosynthetic metabolism. Metabolomic studies reveal that cyclin D1 broadly promotes biosynthetic pathways including glycolysis, the pentose phosphate pathway, and the purine and pyrimidine nucleotide synthesis in hepatocytes. Proteomic analyses demonstrate that overexpressed cyclin D1 binds to numerous metabolic enzymes including those involved in glycolysis and pyrimidine synthesis. In the glycolysis pathway, cyclin D1 activates aldolase and GAPDH, and these proteins are phosphorylated by cyclin D1/Cdk4 in vitro. De novo pyrimidine synthesis is particularly dependent on cyclin D1. Cyclin D1/Cdk4 phosphorylates the initial enzyme of this pathway, carbamoyl-phosphate synthetase 2, aspartate transcarbamylase, and dihydroorotase (CAD), and metabolomic analysis indicates that cyclin D1 depletion markedly reduces the activity of this enzyme. Pharmacologic inhibition of Cdk4 along with the downstream pyrimidine synthesis enzyme dihydroorotate dehydrogenase synergistically inhibits proliferation and survival of hepatocellular carcinoma cells. These studies demonstrate that cyclin D1 promotes a broad network of biosynthetic pathways in hepatocytes, and this model may provide insights into potential metabolic vulnerabilities in cancer cells.

Asparagine restriction enhances CD8+ T cell metabolic fitness and antitumoral functionality through an NRF2-dependent stress response

Robust and effective T cell immune surveillance and cancer immunotherapy require proper allocation of metabolic resources to sustain energetically costly processes, including growth and cytokine production. Here, we show that asparagine (Asn) restriction on CD8+ T cells exerted opposing effects during activation (early phase) and differentiation (late phase) following T cell activation. Asn restriction suppressed activation and cell cycle entry in the early phase while rapidly engaging the nuclear factor erythroid 2-related factor 2 (NRF2)-dependent stress response, conferring robust proliferation and effector function on CD8+ T cells during differentiation. Mechanistically, NRF2 activation in CD8+ T cells conferred by Asn restriction rewired the metabolic program by reducing the overall glucose and glutamine consumption but increasing intracellular nucleotides to promote proliferation. Accordingly, Asn restriction or NRF2 activation potentiated the T cell-mediated antitumoral response in preclinical animal models, suggesting that Asn restriction is a promising and clinically relevant strategy to enhance cancer immunotherapy. Our study revealed Asn as a critical metabolic node in directing the stress signaling to shape T cell metabolic fitness and effector functions.

Differential Inhibition of Anaplerotic Pyruvate Carboxylation and Glutaminolysis-Fueled Anabolism Underlies Distinct Toxicity of Selenium Agents in Human Lung Cancer

Past chemopreventive human trials on dietary selenium supplements produced controversial outcomes. They largely employed selenomethionine (SeM)-based diets. SeM was less toxic than selenite or methylseleninic acid (MSeA) to lung cancer cells. We thus investigated the toxic action of these Se agents in two non-small cell lung cancer (NSCLC) cell lines and ex vivo organotypic cultures (OTC) of NSCLC patient lung tissues. Stable isotope-resolved metabolomics (SIRM) using 13C6-glucose and 13C5,15N2-glutamine tracers with gene knockdowns were employed to examine metabolic dysregulations associated with cell type- and treatment-dependent phenotypic changes. Inhibition of key anaplerotic processes, pyruvate carboxylation (PyC) and glutaminolysis were elicited by exposure to MSeA and selenite but not by SeM. They were accompanied by distinct anabolic dysregulation and reflected cell type-dependent changes in proliferation/death/cell cycle arrest. NSCLC OTC showed similar responses of PyC and/or glutaminolysis to the three agents, which correlated with tissue damages. Altogether, we found differential perturbations in anaplerosis-fueled anabolic pathways to underlie the distinct anti-cancer actions of the three Se agents, which could also explain the failure of SeM-based chemoprevention trials.

Abstract 4840: Dysregulation of mitochondrial function by PLK1-mediated PDHA1 phosphorylation promotes Cr(VI)-associated lung cancer progression

Hexavalent chromium (Cr(VI)), an class I environmental carcinogen, not only induces lung epithelial cell transformation but also promotes lung cancer progression by alterations of the cell cycle and cellular energy metabolism. Using Cr(VI)-transformed (CrT) bronchial epithelial cells (BEAS-2B) and parental BEAS-2B cells, we demonstrate that the level of polo-like kinase 1 (PLK1) is highly upregulated in CrT cells, which blocks mitochondrial function, and further promotes cell proliferation both in vitro and in vivo. Cells expressing a high level of PLK1 exhibited repressed mitochondrial activity due to defective modulation of pyruvate dehydrogenase E1 subunit alpha 1 (PDHA1), which facilitates the carbon influx to TCA cycle via catalyzing pyruvate/Acetyl-CoA conversion. Mechanistically, we show that PDHA1 can be directly phosphorylated by PLK1 at T57, which triggers collapse of E1 and PDHA1 degradation via activation of mitophagy. These defects resulted in the inhibition of oxidative phosphorylation and reduction of mitochondrial reactive oxygen species (ROS) generation, eventually inhibiting mitochondrial-mediated apoptotic response. Defining the role of PLK1 in metabolic reprogramming in Cr(VI)-associated cancer progression may give us a new perspective and a target to inhibit Cr(VI)-induced cancer development. In addition, PLK1 inhibitors may be used to increase the chemo-sensitivity of cancer cells by restoring the normal function of mitochondria, thus alleviating the drug resistance caused by dysfunction and hyperpolarization of mitochondria.

Citation Format: Qiongsi Zhang, Zhiguo Li, Xiongjian Rao, Derek B. Allison, Qi Qiao, Zhuangzhuang Zhang, Yifan Kong, Ruixin Wang, Teresa W. Fan, Richard M. Higashi, Andrew N. Lane, Xiaoqi Liu. Dysregulation of mitochondrial function by PLK1-mediated PDHA1 phosphorylation promotes Cr(VI)-associated lung cancer progression. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 4840.

Ultrahigh resolution MS1/MS2-based reconstruction of metabolic networks in mammalian cells reveals changes for selenite and arsenite action

Metabolic networks are complex, intersecting, and composed of numerous enzyme-catalyzed biochemical reactions that transfer various molecular moieties among metabolites. Thus, robust reconstruction of metabolic networks requires metabolite moieties to be tracked, which cannot be readily achieved with mass spectrometry (MS) alone. We previously developed an Ion Chromatography-ultrahigh resolution-MS1/data independent-MS2 method to track the simultaneous incorporation of the heavy isotopes 13C and 15N into the moieties of purine/pyrimidine nucleotides in mammalian cells. Ultrahigh resolution-MS1 resolves and counts multiple tracer atoms in intact metabolites, while data independent-tandem MS (MS2) determines isotopic enrichment in their moieties without concern for the numerous mass isotopologue source ions to be fragmented. Together, they enabled rigorous MS-based reconstruction of metabolic networks at specific enzyme levels. We have expanded this approach to trace the labeled atom fate of [13C6]-glucose in 3D A549 spheroids in response to the anticancer agent selenite and that of [13C5,15N2]-glutamine in 2D BEAS-2B cells in response to arsenite transformation. We deduced altered activities of specific enzymes in the Krebs cycle, pentose phosphate pathway, gluconeogenesis, and UDP-GlcNAc synthesis pathways elicited by the stressors. These metabolic details help elucidate the resistance mechanism of 3D versus 2D A549 cultures to selenite and metabolic reprogramming that can mediate the transformation of BEAS-2B cells by arsenite.

Polarization and β-Glucan Reprogram Immunomodulatory Metabolism in Human Macrophages and Ex Vivo in Human Lung Cancer Tissues

Immunomodulatory (IM) metabolic reprogramming in macrophages (Mϕs) is fundamental to immune function. However, limited information is available for human Mϕs, particularly in response plasticity, which is critical to understanding the variable efficacy of immunotherapies in cancer patients. We carried out an in-depth analysis by combining multiplex stable isotope-resolved metabolomics with reversed phase protein array to map the dynamic changes of the IM metabolic network and key protein regulators in four human donors' Mϕs in response to differential polarization and M1 repolarizer β-glucan (whole glucan particles [WGPs]). These responses were compared with those of WGP-treated ex vivo organotypic tissue cultures (OTCs) of human non-small cell lung cancer. We found consistently enhanced tryptophan catabolism with blocked NAD+ and UTP synthesis in M1-type Mϕs (M1-Mϕs), which was associated with immune activation evidenced by increased release of IL-1β/CXCL10/IFN-γ/TNF-α and reduced phagocytosis. In M2a-Mϕs, WGP treatment of M2a-Mϕs robustly increased glucose utilization via the glycolysis/oxidative branch of the pentose phosphate pathway while enhancing UDP-N-acetyl-glucosamine turnover and glutamine-fueled gluconeogenesis, which was accompanied by the release of proinflammatory IL-1β/TNF-α to above M1-Mϕ's levels, anti-inflammatory IL-10 to above M2a-Mϕ's levels, and attenuated phagocytosis. These IM metabolic responses could underlie the opposing effects of WGP, i.e., reverting M2- to M1-type immune functions but also boosting anti-inflammation. Variable reprogrammed Krebs cycle and glutamine-fueled synthesis of UTP in WGP-treated OTCs of human non-small cell lung cancer were observed, reflecting variable M1 repolarization of tumor-associated Mϕs. This was supported by correlation with IL-1β/TNF-α release and compromised tumor status, making patient-derived OTCs unique models for studying variable immunotherapeutic efficacy in cancer patients.

Abstract 2537: Beta-glucan reprograms immunomodulatory metabolism in human macrophage and ex vivo in lung cancer tissues

We combined multiplex Stable Isotope-Resolved Metabolomics (mSIRM) with Reverse Phase Protein Array (RPPA) to map the time course changes of IM metabolic network and key protein regulators in four human donors’ MΦ’s in response to differential polarization and whole glucan particulates (WGP) treatments. We found consistent and plastic network responses to polarization durations and WGP treatments compared to those of the mouse counterparts. Consistent responses included enhanced 15N2-tryptophan catabolism to quinolinate, 2H2-glucose oxidation to ribose/ribulose-5-phosphate, and conversion of 13C5-glutamine to itaconate in response to pro-inflammatory (M1) versus anti-inflammatory (M2) stimuli. WGP robustly induced the buildup of 2H2-glucose-derived 6-phosphogluconate, -lactate, and -IMP, 13C5-glutamine-derived fructose-1,6-bisphosphate, and increased enrichment of 2H-labeled UDP-N-acetylglucosamine in M2-MΦ’s. However, the Krebs cycle activity was variably enhanced by M2 stimuli or WGP treatment. The consistent effects were related to increased release of proinflammatory IM effectors IL-1β/CXCL10/IFNγ/TNFα by M1-MΦ’s and enhanced release of IL-1β/TNFα to above M1-MΦ’s levels in WGP-treated M2-MΦ’s while boosting the latter in anti-inflammatory IL-10 release and maintenance of NAD+ synthesis. They were also related to lower phagocytosis in M1-MΦ’s and WGP-treated M2-MΦ’s versus M2-MΦ’s. Together with the expression changes of key protein regulators, we suggest enhanced tryptophan catabolism with blocked NAD+ and UTP synthesis to be key to the consistent changes in immune functions in response to M1 stimuli. Likewise, increased glucose utilization via glycolysis and the oxidative branch of the pentose phosphate pathway, and blockade of glutamine-fueled N-linked glycosylation could be linked to reversion of M2 to M1-type immune functions. Reprogrammed Krebs cycle and glutamine conversion to UTP occurred variably in WGP-treated ex vivo organotypic tissue cultures (OTCs) of human non-small cell lung cancer (NSCLC), which could reflect variable M1 repolarization of tumor associated MΦ’s. This in turn correlated with IL-1β/TNFα releases and compromised tumor status, making patient-derived OTCs a unique model for studying variable immunotherapeutic efficacy in cancer patients. In conclusion, consistent and variable IM metabolic responses were evident in four human donors’ MΦ’s. WGP repolarized some M2 to M1-type responses while boosting other M2-type responses. NSCLC OTCs from six patients showed variable M1 repolarization in response to WGP.

Citation Format: Teresa W. M. Fan, Saeed Daneshmandi, Teresa A. Cassel, Mohammad B. Uddin, James Sledziona, Patrick T. Thompson, Penghui Lin, Richard M. Higashi, Andrew N. Lane. Beta-glucan reprograms immunomodulatory metabolism in human macrophage and ex vivo in lung cancer tissues [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 2537.

Abstract 2324: Small-scale microwave-assisted acid hydrolysis method for glycogen determination and turnover in tumors using Stable Isotope Resolved Metabolomics

Introduction: Glycogen is a readily deployed intracellular energy storage macromolecule composed of branched chains of glucose. Although glycogen primarily occurs in the liver and muscle, it can be found in most tissues throughout the body, and its metabolism has been shown to be important in cancers and immune cells. Robust analysis of glycogen turnover requires stable isotope tracing plus a reliable means of quantifying total and labeled glycogen derived from precursors such as 13C6-glucose. Current methods for analyzing glycogen are time- and sample-consuming, at best semi-quantitative, and unable to measure stable isotope enrichment.

Methods: We have developed a microscale method for quantifying both intact and acid-hydrolyzed glycogen by ultra-high-resolution Fourier transform mass spectrometric (UHR-FTMS) and/or NMR analysis in stable isotope resolved metabolomics (SIRM) studies. Polar metabolites, including intact glycogen and their 13C positional isotopomer distributions were first measured in crude biological extracts by high resolution NMR, followed by rapid and efficient acid hydrolysis to glucose in 1 N HCl for 10 minutes at 110 °C under a N2 atmosphere in a microwave-assisted synthesis reactor. The resulting glucose and its 13C isotopologues were then analyzed by UHR-FTMS and/or NMR.

Results: We optimized the microwave digestion time, temperature, and oxygen purging in terms of recovery versus degradation and found 10 minutes at 110-115 °C to give > 90% recovery. The method was applied to track the fate of 13C6-glucose in primary human lung BEAS-2B cells, human macrophages, murine liver and patient-derived tumor xenograft (PDTX) in vivo, and the fate of 2H7-glucose in ex vivo lung organotypic tissue cultures of a lung cancer patient. We showed the incorporation of 13C6-glucose into glycogen and its metabolic intermediates, UDP-Glucose and glucose-1-phosphate, both in terms of the 13C levels and fractional enrichment, thereby demonstrating the utility of the method in tracing glycogen turnover in cells and tissues.

Conclusions: The method offers a quantitative, sensitive, and convenient means to analyze glycogen turnover in mg amounts of complex biological materials.

Keywords: glycogen turnover; 13C6-glucose, stable isotope resolved metabolomics (SIRM); microwave-assisted hydrolysis.

Citation Format: Andrew N. Lane, Timothy L. Scott, Juan Zhu, Teresa A. Cassel, Sara Vicente-Munoz, Penghui Lin, Richard M. Higashi, Teresa W-M Fan. Small-scale microwave-assisted acid hydrolysis method for glycogen determination and turnover in tumors using Stable Isotope Resolved Metabolomics [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 2324.

6-Phosphogluconate dehydrogenase (6PGD), a key checkpoint in reprogramming of regulatory T cells metabolism and function

Cellular metabolism has key roles in T cells differentiation and function. CD4+ T helper-1 (Th1), Th2, and Th17 subsets are highly glycolytic while regulatory T cells (Tregs) use glucose during expansion but rely on fatty acid oxidation for function. Upon uptake, glucose can enter pentose phosphate pathway (PPP) or be used in glycolysis. Here, we showed that blocking 6-phosphogluconate dehydrogenase (6PGD) in the oxidative PPP resulted in substantial reduction of Tregs suppressive function and shifts toward Th1, Th2, and Th17 phenotypes which led to the development of fetal inflammatory disorder in mice model. These in turn improved anti-tumor responses and worsened the outcomes of colitis model. Metabolically, 6PGD blocked Tregs showed improved glycolysis and enhanced non-oxidative PPP to support nucleotide biosynthesis. These results uncover critical role of 6PGD in modulating Tregs plasticity and function, which qualifies it as a novel metabolic checkpoint for immunotherapy applications.

Innate immune activation by checkpoint inhibition in human patient-derived lung cancer tissues

Although Pembrolizumab-based immunotherapy has significantly improved lung cancer patient survival, many patients show variable efficacy and resistance development. A better understanding of the drug’s action is needed to improve patient outcomes. Functional heterogeneity of the tumor microenvironment (TME) is crucial to modulating drug resistance; understanding of individual patients’ TME that impacts drug response is hampered by lack of appropriate models. Lung organotypic tissue slice cultures (OTC) with patients’ native TME procured from primary and brain-metastasized (BM) non-small cell lung cancer (NSCLC) patients were treated with Pembrolizumab and/or beta-glucan (WGP, an innate immune activator). Metabolic tracing with ¹³C₆-Glc/¹³C₅,¹⁵N₂-Gln, multiplex immunofluorescence, and digital spatial profiling (DSP) were employed to interrogate metabolic and functional responses to Pembrolizumab and/or WGP. Primary and BM PD-1⁺ lung cancer OTC responded to Pembrolizumab and Pembrolizumab + WGP treatments, respectively. Pembrolizumab activated innate immune metabolism and functions in primary OTC, which were accompanied by tissue damage. DSP analysis indicated an overall decrease in immunosuppressive macrophages and T cells but revealed microheterogeneity in immune responses and tissue damage. Two TMEs with altered cancer cell properties showed resistance. Pembrolizumab or WGP alone had negligible effects on BM-lung cancer OTC but Pembrolizumab + WGP blocked central metabolism with increased pro-inflammatory effector release and tissue damage. In-depth metabolic analysis and multiplex TME imaging of lung cancer OTC demonstrated overall innate immune activation by Pembrolizumab but heterogeneous responses in the native TME of a patient with primary NSCLC. Metabolic and functional analysis also revealed synergistic action of Pembrolizumab and WGP in OTC of metastatic NSCLC.

NMR Methods for Determining Lipid Turnover via Stable Isotope Resolved Metabolomics

Lipids comprise diverse classes of compounds that are important for the structure and properties of membranes, as high-energy fuel sources and as signaling molecules. Therefore, the turnover rates of these varied classes of lipids are fundamental to cellular function. However, their enormous chemical diversity and dynamic range in cells makes detailed analysis very complex. Furthermore, although stable isotope tracers enable the determination of synthesis and degradation of complex lipids, the numbers of distinguishable molecules increase enormously, which exacerbates the problem. Although LC-MS-MS (Liquid Chromatography-Tandem Mass Spectrometry) is the standard for lipidomics, NMR can add value in global lipid analysis and isotopomer distributions of intact lipids. Here, we describe new developments in NMR analysis for assessing global lipid content and isotopic enrichment of mixtures of complex lipids for two cell lines (PC3 and UMUC3) using both 13C6 glucose and 13C5 glutamine tracers.

Blockade of 6-phosphogluconate dehydrogenase generates CD8+ effector T cells with enhanced anti-tumor function

Although T cell expansion depends on glycolysis, T effector cell differentiation requires signaling via the production of reactive oxygen species (ROS). Because the pentose phosphate pathway (PPP) regulates ROS by generating nicotinamide adenine dinucleotide phosphate (NADPH), we examined how PPP blockade affects T cell differentiation and function. Here, we show that genetic ablation or pharmacologic inhibition of the PPP enzyme 6-phosphogluconate dehydrogenase (6PGD) in the oxidative PPP results in the generation of superior CD8+ T effector cells. These cells have gene signatures and immunogenic markers of effector phenotype and show potent anti-tumor functions both in vitro and in vivo. In these cells, metabolic reprogramming occurs along with increased mitochondrial ROS and activated antioxidation machinery to balance ROS production against oxidative damage. Our findings reveal a role of 6PGD as a checkpoint for T cell effector differentiation/survival and evidence for 6PGD as an attractive metabolic target to improve tumor immunotherapy.

An Ion Chromatography-Ultrahigh-Resolution-MS1/Data-Independent High-Resolution MS2 Method for Stable Isotope-Resolved Metabolomics Reconstruction of Central Metabolic Networks

The metabolome comprises a complex network of interconnecting enzyme-catalyzed reactions that involve transfers of numerous molecular subunits. Thus, the reconstruction of metabolic networks requires metabolite substructures to be tracked. Subunit tracking can be achieved by tracing stable isotopes through metabolic transformations using NMR and ultrahigh -resolution (UHR)-mass spectrometry (MS). UHR-MS¹ readily resolves and counts isotopic labels in metabolites but requires tandem MS to help identify isotopic enrichment in substructures. However, it is challenging to perform chromatography-based UHR-MS¹ with its long acquisition time, while acquiring MS² data on many coeluting labeled isotopologues for each metabolite. We have developed an ion chromatography (IC)-UHR-MS¹/data-independent(DI)-HR-MS² method to trace the fate of ¹³C atoms from [¹³C₆]-glucose ([¹³C₆]-Glc) in 3D A549 spheroids in response to anticancer selenite and simultaneously ¹³C/¹⁵N atoms from [¹³C₅,¹⁵N₂]-glutamine ([¹³C₅,¹⁵N₂]-Gln) in 2D BEAS-2B cells in response to arsenite transformation. This method retains the complete isotopologue distributions of metabolites via UHR-MS¹ while simultaneously acquiring substructure label information via DI-MS². These details in metabolite labeling patterns greatly facilitate rigorous reconstruction of multiple, intersecting metabolic pathways of central metabolism, which are illustrated here for the purine/pyrimidine nucleotide biosynthesis. The pathways reconstructed based on subunit-level isotopologue analysis further reveal specific enzyme-catalyzed reactions that are impacted by selenite or arsenite treatments.

Abstract PO-006: Tracking S-Adenosylmethionine (SAM) and S-Adenosylhomocysteine (SAH) biosynthesis pathway using stable isotope-resolved metabolomics (SIRM)

S-Adenosylmethionine (SAM) and S-Adenosylhomocysteine (SAH) are low abundance, key metabolites in one-carbon metabolism. The ratio of SAM/SAH controls epigenetic DNA and histone methylation, which is central to regulating gene expression in both normal and disease states including cancers (1,2). Stable isotope resolved metabolomics (SIRM) is a powerful approach for mapping metabolic networks in cells and tissues, which employs untargeted ultrahigh resolution MS1 to quantify a full set of isotopologues for a large number of metabolites (3). This demand makes it difficult to implement liquid chromatography (LC)-based analysis. We have developed a simple, rapid and robust LC-free method for analyzing SAM and SAH in mouse tissue, A549 cells, and human plasma. This method has sub nmol detection and is fully compatible with SIRM analysis of many other metabolites. Flash frozen mouse liver tissues or A549 cells were quenched and extracted with ice-cold acetonitrile:water:chloroform (2:0.75:1, v/v). Prior to extraction, A549 cells were grown for 24 h in the presence of either 13C6-glucose or 13CH3-methionine. No extraction was applied to human plasmas. SAM and SAH were captured by solid phase extraction (SPE) using a Bond-Elut phenylboronic acid (PBA) column (Agilent). SAM and SAH levels in liver tissues and plasma obtained by our method was comparable to those found by other methods (4). Tracing with 13C6 glucose showed extensive incorporation of label into the ribose ring and purine of the adenosyl subunit in both SAM and SAH. In contrast, tracing with 13CH3-methioinine showed predominant, single carbon label in SAM and none in SAH, suggesting the prevalence in the incorporation of exogenous methionine into SAM and turnover into SAH. Thus, it is practical to determine SAM and SAH turnover in the methionine cycle in various biological samples, which provides important insights into epigenetic metabolism. Funding: This work was supported in part by grants: 1R01ES022191-01 (to TWMF and RMH), 1P01CA163223-01A1 (to ANL and TWMF), and 1U24DK097215-01A1 (to RMH, TWMF, and ANL). References 1. Cheng et al. (2019) Targeting epigenetic regulators for cancer therapy:mechanisms and advances in clinical trials. Signal Transduction and Targeted Therapy 4:622. 2. U. Hübner, et al. (2007) Stability of Plasma Homocysteine, S-Adenosylmethionine, and S-Adenosylhomocysteine in EDTA, Acidic Citrate, and Primavette™Collection Tubes. Clinical Chemistry 53, 2217-2218. 3. Q. Sun, T. W-M. Fan, A. N. Lane, R. M. Higashi (2019). Applications of Chromatography-Ultra High-resolution MS for Stable Isotope-Resolved Metabolomics (SIRM) Reconstruction of Metabolic Networks. TrAC 123, 115676 4. H. Gellekink, D. et al. (2005) Stable-isotope dilution liquid chromatography-electrospray injection tandem mass spectrometry method for fast, selective measurement of S-adenosylmethionine and S-adenosylhomocysteine in plasma, Clin Chem, 51, 1487-1492.

Citation Format: Joon S Yang, Teresa W-M Fan, Andrew N. Lane, Jason A. Brandon, Richard M. Higashi. Tracking S-Adenosylmethionine (SAM) and S-Adenosylhomocysteine (SAH) biosynthesis pathway using stable isotope-resolved metabolomics (SIRM) [abstract]. In: Abstracts: AACR Special Virtual Conference on Epigenetics and Metabolism; October 15-16, 2020; 2020 Oct 15-16. Philadelphia (PA): AACR; Cancer Res 2020;80(23 Suppl):Abstract nr PO-006.

Abstract IA22: Tracking metabolic compartmentation and epigenetic metabolism in human lung cancer

Although metabolic reprogramming has been recognized as a hallmark of human cancers, our understanding of metabolic heterogeneities/compartmentation and regulation of epigenetics in human tumors is largely unknown. This is crucial to elucidating metabolic checkpoints and strategizing therapeutic target(s) for human cancer. The slow progress is at least in part due to the lack of relevant models and tools for studying these processes. We have established patient-derived organotypic tissue cultures (OTC) that recapitulate the in vivo metabolic reprogramming of human cancer while retaining native patient tumor microenvironment and 3D architecture 1,2. The matched pairs of cancerous (CA) and non-cancerous (NC) lung OTC from the same patient enable reprogrammed cancer tissue metabolism and on-/off-target drug responses for individual patients to be defined. We have deployed this system along with multiplexed Stable Isotope-Resolved Metabolomics (mSIRM) to probe the efficiency of different substates that fuel de novo synthesis of purine nucleotides in matched patients’ CA versus NC lung OTC 3. We found for seven non-small cell lung cancer (NSCLC) patients that 13C6-glucose was the preferred substrate over D3-serine, D2-glycine, or 13C2-glycine in supporting purine synthesis in CA tissues but not or less so in matched NC tissues. Kinetic modeling of the tracer data along with gene/protein expression data suggests that cytoplasmic activation and dynamic compartmentation of the glucose-to-serine pathway as well as reversal of mitochondrial serine to glycine fluxes can account for this preference for glucose. In all seven patients’ CA tissues, c-MYC was overexpressed and its suppression in NSCLC PC9 cells blocked de novo serine synthesis from glucose, enhanced serine-glycine exchanges, and reduced the efficiency of glucose versus serine incorporation into ATP/GTP. However, serine rather than glucose was the preferred substrate for purine synthesis in NSCLC cell lines but c-MYC could alter this preference for serine towards glucose in fueling purine synthesis. This tissue and cell line difference should be considered in designing serine starvation-based cancer therapy. To track metabolism that modulates epigenetic regulation, we employed a fast, sensitive, and robust Fourier transform-mass spectrometric method to analyze S-adenosylmethionine (SAM) and S-adenosylhomocysteine (SAH) levels in A549 cells under anti-cancer methylseleninic acid (MSA) and selenite treatments. We found that SAM/SAH levels were reduced by both treatments and MSA but not selenite increased the SAM to SAH ratio. These changes were accompanied by reduced proliferation, central metabolism, and H3K27Me3 levels in MSA and less so in selenite-treated A549 cells. Thus, the tool for tracking SAM/SAH metabolism along with the SIRM approach opens the opportunity for interrogating epigenetic metabolism and its regulation of growth-promoting central metabolic events. Funding: This work was supported in part by grants: 1R01ES022191-01 (to TWMF and RMH), 1P01CA163223-01A1 (to ANL and TWMF), and 1U24DK097215-01A1 (to RMH, TWMF, and ANL). Refs: 1 Sellers, K. et al. Pyruvate carboxylase is critical for non–small-cell lung cancer proliferation. The Journal of Clinical Investigation 125, 687-698, doi:10.1172/JCI72873 (2015). 2 Fan, T. W., Lane, A. N. & Higashi, R. M. Stable Isotope Resolved Metabolomics Studies in ex vivo Tissue Slices. Bio-protocol 6, e1730 (2016). 3 Fan, T. W. M. et al. De novo synthesis of serine and glycine fuels purine nucleotide biosynthesis in human lung cancer tissues. The Journal of biological chemistry 294, 13464-13477, doi:10.1074/jbc.RA119.008743 (2019).

Citation Format: Teresa W-M Fan, Andrew N. Lane, Jason A. Brandon, Joonseon Yang, Chi V. Dang, Richard M. Higashi. Tracking metabolic compartmentation and epigenetic metabolism in human lung cancer [abstract]. In: Abstracts: AACR Special Virtual Conference on Epigenetics and Metabolism; October 15-16, 2020; 2020 Oct 15-16. Philadelphia (PA): AACR; Cancer Res 2020;80(23 Suppl):Abstract nr IA22.

Metabolic reprogramming in tumors: Contributions of the tumor microenvironment

The genetic alterations associated with cell transformation are in large measure expressed in the metabolic phenotype as cancer cells proliferate and change their local environment, and prepare for metastasis. Qualitatively, the fundamental biochemistry of cancer cells is generally the same as in the untransformed cells, but the cancer cells produce a local environment, the TME, that is hostile to the stromal cells, and compete for nutrients. In order to proliferate, cells need sufficient nutrients, either those that cannot be made by the cells themselves, or must be made from simpler precursors. However, in solid tumors, the nutrient supply is often limiting given the potential for rapid proliferation, and the poor quality of the vasculature. Thus, cancer cells may employ a variety of strategies to obtain nutrients for survival, growth and metastasis. Although much has been learned using established cell lines in standard culture conditions, it is becoming clear from in vivo metabolic studies that this can also be misleading, and which nutrients are used for energy production versus building blocks for synthesis of macromolecules can vary greatly from tumor to tumor, and even within the same tumor. Here we review the operation of metabolic networks, and how recent understanding of nutrient supply in the TME and utilization are being revealed using stable isotope tracers in vivo as well as in vitro.

Nitric oxide orchestrates metabolic rewiring in M1 macrophages by targeting aconitase 2 and pyruvate dehydrogenase

Profound metabolic changes are characteristic of macrophages during classical activation and have been implicated in this phenotype. Here we demonstrate that nitric oxide (NO) produced by murine macrophages is responsible for TCA cycle alterations and citrate accumulation associated with polarization. ¹³C tracing and mitochondrial respiration experiments map NO-mediated suppression of metabolism to mitochondrial aconitase (ACO2). Moreover, we find that inflammatory macrophages reroute pyruvate away from pyruvate dehydrogenase (PDH) in an NO-dependent and hypoxia-inducible factor 1α (Hif1α)-independent manner, thereby promoting glutamine-based anaplerosis. Ultimately, NO accumulation leads to suppression and loss of mitochondrial electron transport chain (ETC) complexes. Our data reveal that macrophages metabolic rewiring, in vitro and in vivo, is dependent on NO targeting specific pathways, resulting in reduced production of inflammatory mediators. Our findings require modification to current models of macrophage biology and demonstrate that reprogramming of metabolism should be considered a result rather than a mediator of inflammatory polarization.

Production of inflammatory mediators by M1-polarized macrophages is thought to rely on suppression of mitochondrial metabolism in favor of glycolysis. Refining this concept, here the authors define metabolic targets of nitric oxide as responsible for the mitochondrial rewiring resulting from polarization.

Applications of Chromatography-Ultra High-Resolution MS for Stable Isotope-Resolved Metabolomics (SIRM) Reconstruction of Metabolic Networks

Metabolism is a complex network of compartmentalized and coupled chemical reactions, which often involve transfers of substructures of biomolecules, thus requiring metabolite substructures to be tracked. Stable isotope resolved metabolomics (SIRM) enables pathways reconstruction, even among chemically identical metabolites, by tracking the provenance of stable isotope-labeled substructures using NMR and ultrahigh resolution (UHR) MS. The latter can resolve and count isotopic labels in metabolites and can identify isotopic enrichment in substructures when operated in tandem MS mode. However, MS2 is difficult to implement with chromatography-based UHR-MS due to lengthy MS1 acquisition time that is required to obtain the molecular isotopologue count, which is further exacerbated by the numerous isotopologue source ions to fragment. We review here recent developments in tandem MS applications of SIRM to obtain more detailed information about isotopologue distributions in metabolites and their substructures.

Differential Abundance Analysis with Bayes Shrinkage Estimation of Variance (DASEV) for Zero-Inflated Proteomic and Metabolomic Data

Mass spectrometry (MS) is frequently used for proteomic and metabolomic profiling of biological samples. Data obtained by MS are often zero-inflated. Those zero values are called point mass values (PMVs). Zero values can be further grouped into biological PMVs and technical PMVs. The former type is caused by true absence of a compound and the later type is caused by a technical detection limit. Methods based on a mixture model have been developed to separate the two types of zeros and to perform differential abundance analysis comparing proteomic/metabolomic profiles between different groups of subjects. However, we notice that those methods may give unstable estimate of the model variance, and thus lead to false positive and false negative results when the number of non-zero values is small. In this paper, we propose a new differential abundance analysis method, DASEV, which uses an empirical Bayes shrinkage method to more robustly estimate the variance and enhance the accuracy of differential abundance analysis. Simulation studies and real data analysis show that DASEV substantially improves parameter estimation of the mixture model and outperforms current methods in identifying differentially abundant features.

Software Supporting a Workflow of Quantitative Dynamic Flux Maps Estimation in Central Metabolism from SIRM Experimental Data

Stable isotope-resolved metabolomics (SIRM), based on the analysis of biological samples from living cells incubated with artificial isotope enriched substrates, enables mapping the rates of biochemical reactions (metabolic fluxes). We developed software supporting a workflow of analysis of SIRM data obtained with mass spectrometry (MS). The evaluation of fluxes starting from raw MS recordings requires at least three steps of computer support: first, extraction of mass spectra of metabolites of interest, then correction of the spectra for natural isotope abundance, and finally, evaluation of fluxes by simulation of the corrected spectra using a corresponding mathematical model. A kinetic model based on ordinary differential equations (ODEs) for isotopomers of metabolites of the corresponding biochemical network supports the final part of the analysis, which provides a dynamic flux map.

Inhibition of Anaplerotic Glutaminolysis Underlies Selenite Toxicity in Human Lung Cancer

Large clinical trials and model systems studies suggest that the chemical form of selenium dictates chemopreventive and chemotherapeutic efficacy. Selenite induces excess ROS production, which mediates autophagy and eventual cell death in non-small cell lung cancer adenocarcinoma A549 cells. As the mechanisms underlying these phenotypic effects are unclear, the clinical relevance of selenite for cancer therapy remains to be determined. The authors' previous stable isotope-resolved metabolomics and gene expression analysis showed that selenite disrupts glycolysis, the Krebs cycle, and polyamine metabolism in A549 cells, potentially through perturbed glutaminolysis, a vital anaplerotic process for proliferation of many cancer cells. Herein, the role of the glutaminolytic enzyme glutaminase 1 (GLS1) in selenite's toxicity in A549 cells and in patient-derived lung cancer tissues is investigated. Using [¹³ C₆ ]-glucose and [¹³ C₅ ,¹⁵ N₂ ]-glutamine tracers, selenite's action on metabolic networks is determined. Selenite inhibits glutaminolysis and glutathione synthesis by suppressing GLS1 expression, and blocks the Krebs cycle, but transiently activates pyruvate carboxylase activity. Glutamate supplementation partially rescues these anti-proliferative and oxidative stress activities. Similar metabolic perturbations and necrosis are observed in selenite-treated human patients' cancerous lung tissues ex vivo. The results support the hypothesis that GLS1 suppression mediates part of the anti-cancer activity of selenite both in vitro and ex vivo.

De novo synthesis of serine and glycine fuels purine nucleotide biosynthesis in human lung cancer tissues

Nucleotide synthesis is essential to proliferating cells, but the preferred precursors for de novo biosynthesis are not defined in human cancer tissues. We have employed multiplexed stable isotope-resolved metabolomics to track the metabolism of [¹³C₆]glucose, D₂-glycine, [¹³C₂]glycine, and D₃-serine into purine nucleotides in freshly resected cancerous and matched noncancerous lung tissues from nonsmall cell lung cancer (NSCLC) patients, and we compared the metabolism with established NSCLC PC9 and A549 cell lines in vitro Surprisingly, [¹³C₆]glucose was the best carbon source for purine synthesis in human NSCLC tissues, in contrast to the noncancerous lung tissues from the same patient, which showed lower mitotic indices and MYC expression. We also observed that D₃-Ser was preferentially incorporated into purine rings over D₂-glycine in both tissues and cell lines. MYC suppression attenuated [¹³C₆]glucose, D₃-serine, and [¹³C₂]glycine incorporation into purines and reduced proliferation in PC9 but not in A549 cells. Using detailed kinetic modeling, we showed that the preferred use of glucose as a carbon source for purine ring synthesis in NSCLC tissues involves cytoplasmic activation/compartmentation of the glucose-to-serine pathway and enhanced reversed one-carbon fluxes that attenuate exogenous serine incorporation into purines. Our findings also indicate that the substrate for de novo nucleotide synthesis differs profoundly between cancer cell lines and fresh human lung cancer tissues; the latter preferred glucose to exogenous serine or glycine but not the former. This distinction in substrate utilization in purine synthesis in human cancer tissues should be considered when targeting one-carbon metabolism for cancer therapy.

Improved segmented-scan spectral stitching for stable isotope resolved metabolomics (SIRM) by ultra-high-resolution Fourier transform mass spectrometry

We have implemented a linear ion trap (LIT)-based SIM-stitching method for ultra-high-resolution Fourier transform mass spectrometry (FTMS) that increases the S/N over a wide m/z range compared to non-segmented wide full-scan (WFS) spectra. Here we described an improved segmented spectral scan stitching method that was based on quadrupole mass filter (QMF)-SIM, which overcame previous limitations of ion signal loss in LIT. This allowed for accurate representation of isotopologue distributions, both at natural abundance and in stable isotope-resolved metabolomics (SIRM)-based experiments. We also introduced a new spectral binning method that provided more precise and resolution-independent bins for irreversibly noise-suppressed FTMS spectra. We demonstrated a substantial improvement in S/N and sensitivity (typically > 10-fold) for ¹³C labeled lipid extracts of human macrophages grown as three-dimensional (3D) cell culture, with detection of an increased number of ¹³C isotopologue ions. The method also enabled analysis of extracts from very limited biological samples.

Quantification of Isotopologues of Amino Acids by Multiplexed Stable Isotope-Resolved Metabolomics Using Ultrahigh-Resolution Mass Spectrometry Coupled with Direct Infusion

Stable isotope-resolved metabolomics (SIRM) is increasingly used among researchers for metabolic studies including amino acid metabolism. However, the classical GC- or HPLC-based methods for amino acid quantification do not meet the needs for multiplexed stable isotope-enriched analysis by ultrahigh-resolution Fourier transform mass spectrometry (UHR-FTMS). This is due to insufficient acquisition time during chromatographic separations and large dynamic range in concentrations of analytes, which compromises detection and quantification of the numerous metabolite isotopologues present in crude extracts. This chapter discusses a modified ethyl chloroformate derivatization method to enable rapid quantitative analysis of stable isotope-enriched amino acids using direct infusion ion introduction coupled with UHR-FTMS.

Exosomal lipids for classifying early and late stage non-small cell lung cancer

Lung cancer is the leading cause of cancer deaths in the United States. Patients with early stage lung cancer have the best prognosis with surgical removal of the tumor, but the disease is often asymptomatic until advanced disease develops, and there are no effective blood-based screening methods for early detection of lung cancer in at-risk populations. We have explored the lipid profiles of blood plasma exosomes using ultra high-resolution Fourier transform mass spectrometry (UHR-FTMS) for early detection of the prevalent non-small cell lung cancers (NSCLC). Exosomes are nanovehicles released by various cells and tumor tissues to elicit important biofunctions such as immune modulation and tumor development. Plasma exosomal lipid profiles were acquired from 39 normal and 91 NSCLC subjects (44 early stage and 47 late stage). We have applied two multivariate statistical methods, Random Forest (RF) and Least Absolute Shrinkage and Selection Operator (LASSO) to classify the data. For the RF method, the Gini importance of the assigned lipids was calculated to select 16 lipids with top importance. Using the LASSO method, 7 features were selected based on a grouped LASSO penalty. The Area Under the Receiver Operating Characteristic curve for early and late stage cancer versus normal subjects using the selected lipid features was 0.85 and 0.88 for RF and 0.79 and 0.77 for LASSO, respectively. These results show the value of RF and LASSO for metabolomics data-based biomarker development, which provide robust an independent classifiers with sparse data sets. Application of LASSO and Random Forests identifies lipid features that successfully distinguish early stage lung cancer patient from healthy individuals.

NMR and MS-based Stable Isotope-Resolved Metabolomics and Applications in Cancer Metabolism

There is considerable interest in defining metabolic reprogramming in human diseases, which is recognized as a hallmark of human cancer. Although radiotracers have a long history in specific metabolic studies, stable isotope-enriched precursors coupled with modern high resolution mass spectrometry and NMR spectroscopy have enabled systematic mapping of metabolic networks and fluxes in cells, tissues and living organisms including humans. These analytical platforms are high in information content, are complementary and cross-validating in terms of compound identification, quantification, and isotope labeling pattern analysis of a large number of metabolites simultaneously. Furthermore, new developments in chemoselective derivatization and in vivo spectroscopy enable tracking of labile/low abundance metabolites and metabolic kinetics in real-time. Here we review developments in Stable Isotope Resolved Metabolomics (SIRM) and recent applications in cancer metabolism using a wide variety of stable isotope tracers that probe both broad and specific aspects of cancer metabolism required for proliferation and survival.

New methods to identify high peak density artifacts in Fourier transform mass spectra and to mitigate their effects on high-throughput metabolomic data analysis

INTRODUCTION

Direct injection Fourier-transform mass spectrometry (FT-MS) allows for the high-throughput and high-resolution detection of thousands of metabolite-associated isotopologues. However, spectral artifacts can generate large numbers of spectral features (peaks) that do not correspond to known compounds. Misassignment of these artifactual features creates interpretive errors and limits our ability to discern the role of representative features within living systems.

OBJECTIVES

Our goal is to develop rigorous methods that identify and handle spectral artifacts within the context of high-throughput FT-MS-based metabolomics studies.

RESULTS

We observed three types of artifacts unique to FT-MS that we named high peak density (HPD) sites: fuzzy sites, ringing and partial ringing. While ringing artifacts are well-known, fuzzy sites and partial ringing have not been previously well-characterized in the literature. We developed new computational methods based on comparisons of peak density within a spectrum to identify regions of spectra with fuzzy sites. We used these methods to identify and eliminate fuzzy site artifacts in an example dataset of paired cancer and non-cancer lung tissue samples and evaluated the impact of these artifacts on classification accuracy and robustness.

CONCLUSION

Our methods robustly identified consistent fuzzy site artifacts in our FT-MS metabolomics spectral data. Without artifact identification and removal, 91.4% classification accuracy was achieved on an example lung cancer dataset; however, these classifiers rely heavily on artifactual features present in fuzzy sites. Proper removal of fuzzy site artifacts produces a more robust classifier based on non-artifactual features, with slightly improved accuracy of 92.4% in our example analysis.

Quantitative profiling of carbonyl metabolites directly in crude biological extracts using chemoselective tagging and nanoESI-FTMS

The extensive range of chemical structures, wide range of abundances, and chemical instability of metabolites present in the metabolome pose major analytical challenges that are difficult to address with existing technologies. To address these issues, one approach is to target a subset of metabolites that share a functional group, such as ketones and aldehydes, using chemoselective tagging. Here we report a greatly improved chemoselective method for the quantitative analysis of hydrophilic and hydrophobic carbonyl-containing metabolites directly in biological samples. This method is based on direct tissue or cells extraction with simultaneous derivatization of stable and labile carbonylated metabolites using N-[2-(aminooxy)ethyl]-N,N-dimethyl-1-dodecylammonium (QDA) and ¹³CD₃ labeled QDA. We combined innovations of direct quenching of biological sample with frozen derivatization conditions under the catalyst N,N-dimethyl-p-phenylenediamine, which facilitated the formation of oxime stable-isotope ion pairs differing by m/z 4.02188 while minimizing metabolite degradation. The resulting oximes were extracted by HyperSep C8 tips to remove interfering compounds, and the products were detected using nano-electrospray ionization interfaced with a Thermo Fusion mass spectrometer. The quaternary ammonium tagging greatly increased electrospray MS detection sensitivity and the signature ions pairs enabled simple identification of carbonyl compounds. The improved method showed the lower limits of quantification for carbonyl standards to be in the range of 0.20-2 nM, with linearity of R² > 0.99 over 4 orders of magnitude. We have applied the method to assign 66 carbonyls in mouse tumor tissues, many of which could not be assigned solely by accurate mass and tandem MS. Fourteen of the metabolites were quantified using authentic standards. We also demonstrated the suitability of this method for determining ¹³C labeled isotopologues of carbonyl metabolites in ¹³C₆-glucose-based stable isotope-resolved metabolomic (SIRM) studies.

Acute loss of iron-sulfur clusters results in metabolic reprogramming and generation of lipid droplets in mammalian cells

Iron-sulfur (Fe-S) clusters are ancient cofactors in cells and participate in diverse biochemical functions, including electron transfer and enzymatic catalysis. Although cell lines derived from individuals carrying mutations in the Fe-S cluster biogenesis pathway or siRNA-mediated knockdown of the Fe-S assembly components provide excellent models for investigating Fe-S cluster formation in mammalian cells, these experimental strategies focus on the consequences of prolonged impairment of Fe-S assembly. Here, we constructed and expressed dominant-negative variants of the primary Fe-S biogenesis scaffold protein iron-sulfur cluster assembly enzyme 2 (ISCU2) in human HEK293 cells. This approach enabled us to study the early metabolic reprogramming associated with loss of Fe-S-containing proteins in several major cellular compartments. Using multiple metabolomics platforms, we observed a ∼12-fold increase in intracellular citrate content in Fe-S-deficient cells, a surge that was due to loss of aconitase activity. The excess citrate was generated from glucose-derived acetyl-CoA, and global analysis of cellular lipids revealed that fatty acid biosynthesis increased markedly relative to cellular proliferation rates in Fe-S-deficient cells. We also observed intracellular lipid droplet accumulation in both acutely Fe-S-deficient cells and iron-starved cells. We conclude that deficient Fe-S biogenesis and acute iron deficiency rapidly increase cellular citrate concentrations, leading to fatty acid synthesis and cytosolic lipid droplet formation. Our findings uncover a potential cause of cellular steatosis in nonadipose tissues.

Selenium toxicity to survival and reproduction of Collembola and Enchytraeids in a sandy loam soil

We investigated the toxicity of selenium (Se) to the soil invertebrates Folsomia candida (Collembola) and Enchytraeus crypticus (potworm). Studies were designed to generate ecotoxicological benchmarks for developing ecological soil screening levels (Eco-SSLs) for risk assessments of contaminated soils. For the present studies, we selected Sassafras sandy loam, an aerobic upland soil with soil characteristics (low levels of clay and organic matter, soil pH adjusted from 5.2 to 7.1) that support high relative bioavailability of the anionic Se species that is typically found in aerobic soil. The Se was amended into soil as sodium selenate, subjected to weathering and aging using 21 d of alternating cycles of air-drying/rehydration to 60% of the water-holding capacity of the Sassafras sandy loam soil, under ambient greenhouse conditions. Effective concentrations at 20 and 50% (EC20 and EC50) levels for production of juveniles (reproduction) were 4.7 and 10.9 mg of Se/kg of soil (dry mass basis), respectively, for Collembola, and 4.4 and 6.2 mg/kg, respectively, for the potworms. The data enabled the derivation of toxicity benchmarks, contributing to the development of a soil invertebrate-based Eco-SSL of 4.1 mg/kg for Se. Environ Toxicol Chem 2018;37:846-853. Published 2017 Wiley Periodicals Inc. on behalf of SETAC. This article is a US government work and, as such, is in the public domain in the United States of America.

Correction: Quantitative profiling of carbonyl metabolites directly in crude biological extracts using chemoselective tagging and nanoESI-FTMS

Correction for 'Quantitative profiling of carbonyl metabolites directly in crude biological extracts using chemoselective tagging and nanoESI-FTMS' by Pan Deng, et al., Analyst, 2018, 143, 311-322.

Exploring cancer metabolism using stable isotope-resolved metabolomics (SIRM)

Metabolic reprogramming is a hallmark of cancer. The changes in metabolism are adaptive to permit proliferation, survival, and eventually metastasis in a harsh environment. Stable isotope-resolved metabolomics (SIRM) is an approach that uses advanced approaches of NMR and mass spectrometry to analyze the fate of individual atoms from stable isotope-enriched precursors to products to deduce metabolic pathways and networks. The approach can be applied to a wide range of biological systems, including human subjects. This review focuses on the applications of SIRM to cancer metabolism and its use in understanding drug actions.

Abstract 2501: Assessing metabolic activity of patient-derived models of non-small cell lung cancer using stable isotope resolved metabolomics (SIRM)

Stable Isotope-Resolved Metabolomics (SIRM) has been a useful tool in interrogating metabolic reprogramming in cancer. We have recently published several protocols using SIRM in patient-derived models of non-small cell lung cancer (NSCLC)1. In this case study, we compared central metabolic activity in three different model systems, all derived from the same patient. Slices from the human tumor (Warburg slices 2,3), slices from an NSG mouse bearing the human tumor 4, and the patient-derived cell culture were incubated in [U-13C]-glucose or [U-13C,15N]-glutamine for 24 hours. Samples were then harvested and analyzed by gas-chromatography-mass spectrometry and NMR. All three models displayed similar levels of fractional enrichment after 24 hours, making metabolic comparison possible, despite their very different 3D architectures. Glucose metabolism in particular, showed consistent labeling patterns of metabolites in glycolysis and the Krebs cycle. Glutamine metabolism, however, was distinct in the cell culture, with a pattern that indicated upregulation of anaplerotic glutaminolysis. Activation of glutaminolysis may be an important transformative step in the establishment of a viable cell culture. We are also in the process of validating the present finding by comparing multiple patient-derived models of NSCLC and tracking the evolution of their metabolic activity.

1 Lane, A. N., Higashi, R. M. & Fan, T. W.-M. Preclinical models for interrogating drug action in human cancers using Stable Isotope Resolved Metabolomics (SIRM) Metabolomics 12, 1-15 (2016).

2 Fan, T. W.-M. et al. Distinctly perturbed metabolic networks underlie differential tumor tissue damages induced by immune modulator β-glucan in a two-case ex vivo non-small cell lung cancer study. CSH Molec. Case Studies J. 2, a00083, (2016).

3 Fan, T. W.-M., Lane, A. N. & Higashi, R. M. Stable Isotope Resolved Metabolomics Studies in ex vivo Tissue Slices. Bio-protocol 6, e1730 (2016).

4 Lane, A. N., Yan, J. & Fan, T. W.-M. 13C Tracer Studies of Metabolism in Mouse Tumor Xenografts. Bio-protocol 5, e1650 (2015).

Citation Format: Connor J. Kinslow, Jinlian Tan, Yihua Cai, Jun Yan, Richard M. Higashi, Andrew N. Lane, Teresa W. Fan. Assessing metabolic activity of patient-derived models of non-small cell lung cancer using stable isotope resolved metabolomics (SIRM) [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 2501. doi:10.1158/1538-7445.AM2017-2501

Abstract 2502: Liquid diet introduction of tracers into mice for stable isotope-resolved metabolomics (SIRM) investigations

Tracer-based mapping of metabolic networks in vivo is a powerful approach for revealing metabolic reprogramming in human cancer. However, current in vivo labeling techniques for model animals face important challenges including insufficient depth of pathway coverage (e.g. inability to detect labeled nucleotides, proteins, and lipids) and stress-related artifacts. Here, we report stress-free administration of 13C6-glucose via liquid diet into mice. 13C enrichment was observed in metabolites of glycolysis, the Krebs cycle, the pentose phosphate pathway, nucleobases, UDP-sugars, as well as macromolecules glycogen, lipids, and proteins from major organs in NSG mice. We have applied the liquid diet method to map the glucose metabolic networks in NSCLC tumors in a patient-derived xenograft (PDX) model. We observed a high enrichment in the metabolites of glycolysis, Krebs cycle, and PPP as well as de novo synthesized nucleotides and amino acids by IC-UHR-FTMS analysis. Lung PDX displayed unexpected metabolic complexity, such as the use of pyruvate to fuel anaplerosis as well as gluconeogenesis. We also found high 13C enrichment in both tumor and plasma glutamine, which implies that glutamine in the PDX tumors largely came from other organs via the blood rather than being synthesized in situ. Our data showed that liquid diet is an effective and noninvasive means for comprehensive analysis of glucose-associated metabolic networks in human tumor xenografts, which can also be extended to SIRM studies with other fuel sources.

Acknowledgements: This work was supported in part by grants: 1R01ES022191-01 (to TWMF and RMH), 1P01CA163223-01A1 (to ANL and TWMF), and 1U24DK097215-01A1 (to RMH, TWMF, and ANL)

R.C. Sun was supported by a T32 training grant to M. Vore (5T32ES007266-25)

Citation Format: Ramon C. Sun, Marc O. Warmoes, Ye Yang, Pan Deng, Qiushi Sun, Andrew N. Lane, Richard M. Higashi, Teresa W-M Fan. Liquid diet introduction of tracers into mice for stable isotope-resolved metabolomics (SIRM) investigations [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 2502. doi:10.1158/1538-7445.AM2017-2502

Chloroformate derivatization for tracing the fate of Amino acids in cells and tissues by multiple stable isotope resolved metabolomics (mSIRM)

Amino acids have crucial roles in central metabolism, both anabolic and catabolic. To elucidate these roles, steady-state concentrations of amino acids alone are insufficient, as each amino acid participates in multiple pathways and functions in a complex network, which can also be compartmentalized. Stable Isotope-Resolved Metabolomics (SIRM) is an approach that uses atom-resolved tracking of metabolites through biochemical transformations in cells, tissues, or whole organisms. Using different elemental stable isotopes to label multiple metabolite precursors makes it possible to resolve simultaneously the utilization of these precursors in a single experiment. Conversely, a single precursor labeled with two (or more) different elemental isotopes can trace the allocation of e.g. C and N atoms through the network. Such dual-label experiments however challenge the resolution of conventional mass spectrometers, which must distinguish the neutron mass differences among different elemental isotopes. This requires ultrahigh resolution Fourier transform mass spectrometry (UHR-FTMS). When combined with direct infusion nano-electrospray ion source (nano-ESI), UHR-FTMS can provide rapid, global, and quantitative analysis of all possible mass isotopologues of metabolites. Unfortunately, very low mass polar metabolites such as amino acids can be difficult to analyze by current models of UHR-FTMS, plus the high salt content present in typical cell or tissue polar extracts may cause unacceptable ion suppression for sources such as nano-ESI. Here we describe a modified method of ethyl chloroformate (ECF) derivatization of amino acids to enable rapid quantitative analysis of stable isotope labeled amino acids using nano-ESI UHR-FTMS. This method showed excellent linearity with quantifiable limits in the low nanomolar range represented in microgram quantities of biological specimens, which results in extracts with total analyte abundances in the low to sub-femtomole range. We have applied this method to profile amino acids and their labeling patterns in ¹³C and ²H doubly labeled PC9 cell extracts, cancerous and non-cancerous tissue extracts from a lung cancer patient and their protein hydrolysates as well as plasma extracts from mice fed with a liquid diet containing ¹³C₆-glucose (Glc). The multi-element isotopologue distributions provided key insights into amino acid metabolism and intracellular pools in human lung cancer tissues in high detail. The ¹³C labeling of Asp and Glu revealed de novo synthesis of these amino acids from ¹³C₆-Glc via the Krebs cycle, specifically the elevated level of ¹³C₃-labeled Asp and Glu in cancerous versus non-cancerous lung tissues was consistent with enhanced pyruvate carboxylation. In addition, tracking the fate of double tracers, (¹³C₆-Glc + ²H₂-Gly or ¹³C₆-Glc + ²H₃-Ser) in PC9 cells clearly resolved pools of Ser and Gly synthesized de novo from ¹³C₆-Glc (¹³C₃-Ser and ¹³C₂-Gly) versus Ser and Gly derived from external sources (²H₃-Ser, ²H₂-Gly). Moreover the complex ²H labeling patterns of the latter were results of Ser and Gly exchange through active Ser-Gly one-carbon metabolic pathway in PC9 cells.

Probing the metabolic phenotype of breast cancer cells by multiple tracer stable isotope resolved metabolomics

Breast cancers vary by their origin and specific set of genetic lesions, which gives rise to distinct phenotypes and differential response to targeted and untargeted chemotherapies. To explore the functional differences of different breast cell types, we performed Stable Isotope Resolved Metabolomics (SIRM) studies of one primary breast (HMEC) and three breast cancer cells (MCF-7, MDAMB-231, and ZR75-1) having distinct genotypes and growth characteristics, using ¹³C₆-glucose, ¹³C-1+2-glucose, ¹³C₅,¹⁵N₂-Gln, ¹³C₃-glycerol, and ¹³C₈-octanoate as tracers. These tracers were designed to probe the central energy producing and anabolic pathways (glycolysis, pentose phosphate pathway, Krebs Cycle, glutaminolysis, nucleotide synthesis and lipid turnover). We found that glycolysis was not associated with the rate of breast cancer cell proliferation, glutaminolysis did not support lipid synthesis in primary breast or breast cancer cells, but was a major contributor to pyrimidine ring synthesis in all cell types; anaplerotic pyruvate carboxylation was activated in breast cancer versus primary cells. We also found that glucose metabolism in individual breast cancer cell lines differed between in vitro cultures and tumor xenografts, but not the metabolic distinctions between cell lines, which may reflect the influence of tumor architecture/microenvironment.

Distinctly perturbed metabolic networks underlie differential tumor tissue damages induced by immune modulator β-glucan in a two-case ex vivo non-small-cell lung cancer study

Cancer and stromal cell metabolism is important for understanding tumor development, which highly depends on the tumor microenvironment (TME). Cell or animal models cannot recapitulate the human TME. We have developed an ex vivo paired cancerous (CA) and noncancerous (NC) human lung tissue approach to explore cancer and stromal cell metabolism in the native human TME. This approach enabled full control of experimental parameters and acquisition of individual patient's target tissue response to therapeutic agents while eliminating interferences from genetic and physiological variations. In this two-case study of non-small-cell lung cancer, we performed stable isotope-resolved metabolomic (SIRM) experiments on paired CA and NC lung tissues treated with a macrophage activator β-glucan and (13)C6-glucose, followed by ion chromatography-Fourier transform mass spectrometry (IC-FTMS) and nuclear magnetic resonance (NMR) analyses of (13)C-labeling patterns of metabolites. We demonstrated that CA lung tissue slices were metabolically more active than their NC counterparts, which recapitulated the metabolic reprogramming in CA lung tissues observed in vivo. We showed β-glucan-enhanced glycolysis, Krebs cycle, pentose phosphate pathway, antioxidant production, and itaconate buildup in patient UK021 with chronic obstructive pulmonary disease (COPD) and an abundance of tumor-associated macrophages (TAMs) but not in UK049 with no COPD and much less macrophage infiltration. This metabolic response of UK021 tissues was accompanied by reduced mitotic index, increased necrosis, and enhaced inducible nitric oxide synthase (iNOS) expression. We surmise that the reprogrammed networks could reflect β-glucan M1 polarization of human macrophages. This case study presents a unique opportunity for investigating metabolic responses of human macrophages to immune modulators in their native microenvironment on an individual patient basis.

Abstract 4271: Beta-glucan activates macrophages in human NSCLC demonstrated by Stable Isotope Resolved Metabolomics (SIRM)

Introduction: We use SIRM to evaluate metabolic reprogramming of lung cancer cells in monoculture, in mouse xenograft/explant models, and in NSCLC patients in situ (1,2). We have now extended the range of models to fresh human tissue slices, which retain the original tissue architecture and heterogeneity with a paired benign versus cancer tissue design under defined cell culture conditions. β-glucan is a polysaccharide that repolarizes tumor-associated macrophages (TAMs) from the M2 to the M1 phenotype in mice (3). Here we report the activation of TAMs in human NSCLC tissue slices.

Experimental: Freshly resected paired tissue slices from individual patients (approx. 1 mm or less thick and 5-40 mg wet weight) were incubated ± particulate β-glucan in standard cell culture conditions, with gentle rocking to enable efficient gas, nutrient, and waste product exchange. Tissue slices could be maintained metabolically viable for at least 48 h of incubation. The metabolic activity was determined by measuring the uptake and transformation of 13C and/or 15N-enriched common nutrient tracers such as glucose and glutamine, using high resolution mass spectrometry, GC-MS, and NMR after a period of incubation (2).

Findings: Time-course analysis of the slices by NMR, MS, and histology revealed that NSCLC tissue slices, both benign and tumorous, retained their architecture and a broad spectrum of metabolic activities. Glucose and glutamine metabolism was reprogrammed in the tumor relative to the paired benign tissues ex vivo, as the in vivo case. The paired tissues from different patients showed significantly different metabolic responses to β-glucan, as expected

Conclusions: This platform offers a human tissue model for preclinical studies on metabolic reprogramming of human cancer and stromal cells in their tissue context, and response to drug treatment (4). As the microenvironment of the target human tissue is maintained, including the resident immune cells, individualized response to immune-active agents can be determined in a clinically relevant setting.

Supported by NCI P01CA163223-01 and NIEHS 1R01ES022191-01

1. Lane, A.N., Fan, T.W.-M., Bousamra II, M., et al. (2011) Clinical Applications of Stable Isotope-Resolved Metabolomics (SIRM) in Non-Small Cell Lung Cancer. Omics, 15, 173-182.

2. Sellers, K., Fox, M.P., Bousamra, M., II, et al. (2015) Pyruvate carboxylase is critical for non-small-cell lung cancer proliferation. Journal of Clinical Investigation, 125, 687-698.

3. Liu, M., Luo, F., Ding, C., et al. (2015) Particulate β-Glucan Converts Immunosuppressive Macrophages into M1 Phenotype Through Dectin-1-induced Syk-Card9-Erk Pathway and Raf-1-c-Maf Pathway. J. Immunol., 195, 5055-5065.

4. Xie, H., Hanai, J., Ren, et al. (2014) Targeting lactate dehydrogenase-A (LDH-A) inhibits tumorigenesis and tumor progression in mouse models of lung cancer and impacts tumor initiating cells. Cell Metabolism 19, 795-809

Citation Format: Teresa W-M Fan, Andrew N. Lane, Jun Yan, Richard M. Higashi, Jeremiah T. Martin, Michael Bousamra. Beta-glucan activates macrophages in human NSCLC demonstrated by Stable Isotope Resolved Metabolomics (SIRM). [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 4271.

Preclinical models for interrogating drug action in human cancers using Stable Isotope Resolved Metabolomics (SIRM)

AIMS

In this review we compare the advantages and disadvantages of different model biological systems for determining the metabolic functions of cells in complex environments, how they may change in different disease states, and respond to therapeutic interventions.

BACKGROUND

All preclinical drug-testing models have advantages and drawbacks. We compare and contrast established cell, organoid and animal models with ex vivo organ or tissue culture and in vivo human experiments in the context of metabolic readout of drug efficacy. As metabolism reports directly on the biochemical state of cells and tissues, it can be very sensitive to drugs and/or other environmental changes. This is especially so when metabolic activities are probed by stable isotope tracing methods, which can also provide detailed mechanistic information on drug action. We have developed and been applying Stable Isotope-Resolved Metabolomics (SIRM) to examine metabolic reprogramming of human lung cancer cells in monoculture, in mouse xenograft/explant models, and in lung cancer patients in situ (Lane et al. 2011; T. W. Fan et al. 2011; T. W-M. Fan et al. 2012; T. W. Fan et al. 2012; Xie et al. 2014b; Ren et al. 2014a; Sellers et al. 2015b). We are able to determine the influence of the tumor microenvironment using these models. We have now extended the range of models to fresh human tissue slices, similar to those originally described by O. Warburg (Warburg 1923), which retain the native tissue architecture and heterogeneity with a paired benign versus cancer design under defined cell culture conditions. This platform offers an unprecedented human tissue model for preclinical studies on metabolic reprogramming of human cancer cells in their tissue context, and response to drug treatment (Xie et al. 2014a). As the microenvironment of the target human tissue is retained and individual patient's response to drugs is obtained, this platform promises to transcend current limitations of drug selection for clinical trials or treatments.

CONCLUSIONS AND FUTURE WORK

Development of ex vivo human tissue and animal models with humanized organs including bone marrow and liver show considerable promise for analyzing drug responses that are more relevant to humans. Similarly using stable isotope tracer methods with these improved models in advanced stages of the drug development pipeline, in conjunction with tissue biopsy is expected significantly to reduce the high failure rate of experimental drugs in Phase II and III clinical trials.

An obligatory role for neurotensin in high-fat-diet-induced obesity

Obesity and its associated comorbidities (e.g., diabetes mellitus and hepatic steatosis) contribute to approximately 2.5 million deaths annually¹ and are among the most prevalent and challenging conditions confronting the medical profession^2,3. Neurotensin (NT), a 13-amino acid peptide predominantly localized in specialized enteroendocrine (EE) cells of the small bowel⁴ and released by fat ingestion⁵, facilitates fatty acid (FA) translocation in rat intestine⁶, and stimulates growth of various cancers⁷; the effects of NT are mediated through three known NT receptors (NTR1, 2 and 3)⁸. Increased fasting plasma levels of pro-NT (a stable NT precursor fragment produced in equimolar amounts relative to NT) are associated with increased risk of diabetes, cardiovascular disease and mortality⁹; however, a role for NT as a causative factor in these diseases is unknown. Here, we show that NT-deficient mice demonstrate significantly reduced intestinal fat absorption and are protected from obesity, hepatic steatosis and insulin resistance associated with high fat consumption. We further demonstrate that NT attenuates the activation of AMP-activated protein kinase (AMPK) and stimulates FA absorption in mice and in cultured intestinal cells, and that this occurs through a mechanism involving NTR1 and NTR3/sortilin. Consistent with the findings in mice, expression of NT in Drosophila midgut EE cells results in increased lipid accumulation in the midgut, fat body, and oenocytes (specialized hepatocyte-like cells) and decreased AMPK activation. Remarkably, in humans, we show that both obese and insulin-resistant subjects have elevated plasma concentrations of pro-NT, and in longitudinal studies among non-obese subjects, high levels of pro-NT denote a doubling of the risk of developing obesity later in life. Our findings directly link NT with increased fat absorption and obesity and suggest that NT may provide a prognostic marker of future obesity and a potential target for prevention and treatment.

Stable Isotope Resolved Metabolomics Studies in Ex Vivo TIssue Slices

An important component of this methodology is to assess the role of the tumor microenvironment on tumor growth and survival. To tackle this problem, we have adapted the original approach of Warburg ¹, by combining thin tissue slices with Stable Isotope Resolved Metabolomics (SIRM) to determine detailed metabolic activity of human tissues. SIRM enables the tracing of metabolic transformations of source molecules such as glucose or glutamine over defined time periods, and is a requirement for detailed pathway tracing and flux analysis. In our approach, we maintain freshly resected tissue slices (both cancerous and non- cancerous from the same organ of the same subject) in cell culture media, and treat with appropriate stable isotope-enriched nutrients, e.g.¹³C₆-glucose or ¹³C₅, ¹⁵N₂ -glutamine. These slices are viable for at least 24 h, and make it possible to eliminate systemic influence on the target tissue metabolism while maintaining the original 3D cellular architecture. It is therefore an excellent pre-clinical platform for assessing the effect of therapeutic agents on target tissue metabolism and their therapeutic efficacy on individual patients ^2,3.

Dectin-1 Activation by a Natural Product β-Glucan Converts Immunosuppressive Macrophages into an M1-like Phenotype

Tumor-associated macrophages (TAM) with an alternatively activated phenotype have been linked to tumor-elicited inflammation, immunosuppression, and resistance to chemotherapies in cancer, thus representing an attractive target for an effective cancer immunotherapy. In this study, we demonstrate that particulate yeast-derived β-glucan, a natural polysaccharide compound, converts polarized alternatively activated macrophages or immunosuppressive TAM into a classically activated phenotype with potent immunostimulating activity. This process is associated with macrophage metabolic reprograming with enhanced glycolysis, Krebs cycle, and glutamine utilization. In addition, particulate β-glucan converts immunosuppressive TAM via the C-type lectin receptor dectin-1-induced spleen tyrosine kinase-Card9-Erk pathway. Further in vivo studies show that oral particulate β-glucan treatment significantly delays tumor growth, which is associated with in vivo TAM phenotype conversion and enhanced effector T cell activation. Mice injected with particulate β-glucan-treated TAM mixed with tumor cells have significantly reduced tumor burden with less blood vascular vessels compared with those with TAM plus tumor cell injection. In addition, macrophage depletion significantly reduced the therapeutic efficacy of particulate β-glucan in tumor-bearing mice. These findings have established a new paradigm for macrophage polarization and immunosuppressive TAM conversion and shed light on the action mode of β-glucan treatment in cancer.

Abstract 3199: Stable isotope resolved metabolomics (SIRM) on fresh human tissues as a preclinical drug testing platform

Introduction: All preclinical drug testing models have advantages and drawbacks. We have been using SIRM to evaluate metabolic reprogramming of lung cancer cells in monoculture, in mouse xenograft/explant models, and in NSCLC patients in situ (1), and to determine the influence of the tumor microenvironment using these models. We have now extended the range of models to fresh human tissue slices, similar to those originally described by Warburg (2), which retain the original tissue architecture and heterogeneity with a paired benign versus cancer design under controlled cell culture conditions.

Experimental: Freshly resected tissue slices from individuals (ca. 1 mm or less thick and 5-40 mg wet weight) were incubated in standard cell culture conditions with gentle rocking for efficient gas, nutrient and waste product exchange. The metabolic activity was determined by measuring the uptake and transformation of 13C and/or 15N-enriched nutrient tracers such as glucose and glutamine, using high-resolution MS, GC-MS, and NMR after a period of incubation. Acute metabolic and histologic response to inhibitors or drugs was readily detected in treated tissue slices.

Findings: Analysis at different time points by NMR, MS and histology shows that the NSCLC tissue slices, both benign and tumorous, retained their architecture and remained metabolically viable for at least 48 h of incubation. Glucose and glutamine metabolism was reprogrammed in the tumor relative to the paired benign tissues. The paired tissue also showed very different responses to Se-containing compounds when incubated at the IC50 established for cell lines. After 24 h of incubation, large scale necrosis was evident in the tumor, but not in the benign slices, which was accompanied by large changes in metabolic activities observed by SIRM analysis.

Conclusions: This platform offers a human tissue model for preclinical studies on metabolic reprogramming of human cancer cells in their tissue context, and response to drug treatment (3). As the microenvironment of the target human tissue is retained and individualized response to drugs is obtained, this platform promises to transcend current limitations of drug selection for clinical trials or treatments.

Supported by NCI P01CA163223-01A1 and NIEHS 1R01ES022191-01

1. Lane, A.N., Fan, T.W.-M., Bousamra II, M., Higashi, R.M., Yan, J. and Miller, D.M. (2011) Clinical Applications of Stable Isotope-Resolved Metabolomics (SIRM) in Non-Small Cell Lung Cancer. Omics, 15, 173-182.

2. Warburg, O. (1923) Versuche an überlebendem Carcinomgewebe (Methoden). Biochem. Zeitschr., 142, 317-333.

3. Xie, H., Hanai, J., Ren, J.-G., Kats, L., Burgess, K., Bhargava, P., Signoretti, S., Billiard, J., Duffy, K.J., Grant, A. et al. (2014) Targeting lactate dehydrogenase-A (LDH-A) inhibits tumorigenesis and tumor progression in mouse models of lung cancer and impacts tumor initiating cells. Cell Metabolism 19, 795-809.

Citation Format: Andrew N. Lane, Teresa W-M Fan, Alexander C. Belshoff, Richard M. Higashi, Jeremiah Martin, Michael Bousamra. Stable isotope resolved metabolomics (SIRM) on fresh human tissues as a preclinical drug testing platform. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 3199. doi:10.1158/1538-7445.AM2015-3199

Chemoselective detection and discrimination of carbonyl-containing compounds in metabolite mixtures by 1H-detected 15N nuclear magnetic resonance

NMR spectra of mixtures of metabolites extracted from cells or tissues are extremely complex, reflecting the large number of compounds that are present over a wide range of concentrations. Although multidimensional NMR can greatly improve resolution as well as improve reliability of compound assignments, lower abundance metabolites often remain hidden. We have developed a carbonyl-selective aminooxy probe that specifically reacts with free keto and aldehyde functions, but not carboxylates. By incorporating (15)N in the aminooxy functional group, (15)N-edited NMR was used to select exclusively those metabolites that contain a free carbonyl function while all other metabolites are rejected. Here, we demonstrate that the chemical shifts of the aminooxy adducts of ketones and aldehydes are very different, which can be used to discriminate between aldoses and ketoses, for example. Utilizing the 2-bond or 3-bond (15)N-(1)H couplings, the (15)N-edited NMR analysis was optimized first with authentic standards and then applied to an extract of the lung adenocarcinoma cell line A549. More than 30 carbonyl-containing compounds at NMR-detectable levels, six of which we have assigned by reference to our database. As the aminooxy probe contains a permanently charged quaternary ammonium group, the adducts are also optimized for detection by mass spectrometry. Thus, this sample preparation technique provides a better link between the two structural determination tools, thereby paving the way to faster and more reliable identification of both known and unknown metabolites directly in crude biological extracts.