Survival Pathways of HIF-Deficient Tumour Cells: TCA Inhibition, Peroxisomal Fatty Acid Oxidation Activation and an AMPK-PGC-1α Hypoxia Sensor

The HIF-1 and HIF-2 (HIF1/2) hypoxia responses are frequently upregulated in cancers, and HIF1/2 inhibitors are being developed as anticancer drugs. How could cancers resist anti-HIF1/2 therapy? We studied metabolic and molecular adaptations of HIF-1β-deficient Hepa-1c4, a hepatoma model lacking HIF1/2 signalling, which mimics a cancer treated by a totally effective anti-HIF1/2 agent. [1,2-13C2]-D-glucose metabolism was measured by SiDMAP metabolic profiling, gene expression by TaqMan, and metabolite concentrations by 1H MRS. HIF-1β-deficient Hepa-1c4 responded to hypoxia by increasing glucose uptake and lactate production. They showed higher glutamate, pyruvate dehydrogenase, citrate shuttle, and malonyl-CoA fluxes than normal Hepa-1 cells, whereas pyruvate carboxylase, TCA, and anaplerotic fluxes decreased. Hypoxic HIF-1β-deficient Hepa-1c4 cells increased expression of PGC-1α, phospho-p38 MAPK, and PPARα, suggesting AMPK pathway activation to survive hypoxia. They had higher intracellular acetate, and secreted more H2O2, suggesting increased peroxisomal fatty acid β-oxidation. Simultaneously increased fatty acid synthesis and degradation would have "wasted" ATP in Hepa-1c4 cells, thus raising the [AMP]:[ATP] ratio, and further contributing to the upregulation of the AMPK pathway. Since these tumour cells can proliferate without the HIF-1/2 pathways, combinations of HIF1/2 inhibitors with PGC-1α or AMPK inhibitors should be explored.

An Inhibitor of GSK3B and HDACs Kills Pancreatic Cancer Cells and Slows Pancreatic Tumor Growth and Metastasis in Mice

BACKGROUND & AIMS

Growth, progression, and drug resistance of pancreatic ductal adenocarcinomas (PDACs) have been associated with increased levels and activity of glycogen synthase kinase 3 beta (GSK3B) and histone deacetylases (HDACs). We designed and synthesized molecules that simultaneously inhibit the activities of both enzymes. We tested the effects of one of these molecules, Metavert, in pancreatic cancer cells and mice with pancreatic tumors.

METHODS

We tested the ability of Metavert to bind GSK3B and HDACs using surface plasmon resonance. MIA PaCa-2, Bx-PC3, HPAF-II, and HPDE6 cell lines were incubated with different concentrations of Metavert, with or without paclitaxel or gemcitabine, or with other inhibitors of GSK3B and HDACs; cells were analyzed for apoptosis and migration and by immunoblotting, immunofluorescence, and real-time polymerase chain reaction. Krasþ/LSLG12D;Trp53þ/LSLR172H;Pdx-1-Cre (KPC) mice (2 months old) were given injections of Metavert (5 mg/kg, 3 times/week) or vehicle (control). B6.129J mice with tumors grown from UN-KPC961-Luc cells were given injections of Metavert or vehicle. Tumors and metastases were counted and pancreata were analyzed by immunohistochemistry. Glucose metabolism was measured using 13C-glucose tracer and mass spectroscopy and flow cytometry. Cytokine levels in blood samples were measured using multiplexing enzyme-linked immunosorbent assay.

RESULTS

Metavert significantly reduced survival of PDAC cells but not nontransformed cells; the agent reduced markers of the epithelial-to-mesenchymal transition and stem cells in PDAC cell lines. Cells incubated with Metavert in combination with irradiation and paclitaxel or gemcitabine had reduced survival compared with cells incubated with either agent alone; Metavert increased killing of drug-resistant PDAC cells by paclitaxel and gemcitabine. PDAC cells incubated with Metavert acquired normalized glucose metabolism. Administration of Metavert (alone or in combination with gemcitibine) to KPC mice or mice with syngeneic tumors significantly increased their survival times, slowed tumor growth, prevented tumor metastasis, decreased tumor infiltration by tumor-associated macrophages, and decreased blood levels of cytokines.

CONCLUSIONS

In studies of PDAC cells and 2 mouse models of PDAC, we found a dual inhibitor of GSK3B and HDACs (Metavert) to induce cancer cell apoptosis, reduce migration and expression of stem cell markers, and slow growth of tumors and metastases. Metavert had synergistic effects with gemcitabine.

De novo lipogenesis represents a therapeutic target in mutant Kras non-small cell lung cancer

Oncogenic Kras mutations are one of the most common alterations in non-small cell lung cancer and are associated with poor response to treatment and reduced survival. Driver oncogenes, such as Kras are now appreciated for their ability to promote tumor growth via up-regulation of anabolic pathways. Therefore, we wanted to identify metabolic vulnerabilities in Kras-mutant lung cancer. Using the Kras LSL-G12D lung cancer model, we show that mutant Kras drives a lipogenic gene-expression program. Stable-isotope analysis reveals that mutant Kras promotes de novo fatty acid synthesis in vitro and in vivo. The importance of fatty acid synthesis in Kras-induced tumorigenesis was evident by decreased tumor formation in Kras LSL-G12D mice after treatment with a fatty acid synthesis inhibitor. Importantly, with gain and loss of function models of mutant Kras, we demonstrate that mutant Kras potentiates the growth inhibitory effects of several fatty acid synthesis inhibitors. These studies highlight the potential to target mutant Kras tumors by taking advantage of the lipogenic phenotype induced by mutant Kras.-Singh, A., Ruiz, C., Bhalla, K., Haley, J. A., Li, Q. K., Acquaah-Mensah, G., Montal, E., Sudini, K. R., Skoulidis, F., Wistuba, I. I., Papadimitrakopoulou, V., Heymach, J. V., Boros, L. G., Gabrielson, E., Carretero, J., Wong, K.-k., Haley, J. D., Biswal, S., Girnun, G. D. De novo lipogenesis represents a therapeutic target in mutant Kras non-small cell lung cancer.

Biological Reductionism versus Redundancy in a Degenerate World

The precision medicine narrative relies on the reductionist assumption that there is a strong linkage between genotype and complex traits (phenotypes). This essay uses examples from humans and other "higher" animals to argue that redundant and degenerate mechanisms operating at the physiological level limit both the general utility of this assumption and the specific utility of the precision medicine narrative.

Abstract B41: Post-transcriptional regulation of IDH1 by the RNA-binding protein HuR is important for pancreatic cancer cell survival under nutrient deprivation

Introduction: Isocitrate dehydrogenase 1(IDH1) has been prioritized in the recent cancer biology literature because of mutations occurring in some tumor types. Additionally the wild type isoenzyme is important for metabolic reprogramming under hypoxic stress. Importantly, the role of IDH1 under other forms of metabolic stress, such as nutrient deprivation (hallmark of the PDA microenvironment) has not been explored, and the regulatory mechanism of IDH1 expression remains unknown. We recently showed that the regulatory RNA binding protein, HuR, binds and directly regulates IDH1 expression in multiple PDA cell lines. The regulatory protein becomes biologically engaged under nutrient deprivation by translocating with the IDH1 transcript form the nucleus to the cytoplasm under glucose deprivation, and HuR silencing sensitized cells under these conditions. Here, we hone in on the regulatory HuR binding site to the IDH1 transcript, explore the importance of HuR in the context of additional metabolic stressors and utilize stable isotope metabolomic profiling to gain mechanistic insight into how HuR is protective under nutrient deprivation.

Methods: IDH1 and HuR expression were knocked down by siRNA, and cell viability was determined by PicoGreen and Trypan blue exclusion assays. Immunofluorescence was used to image HuR subcellular localization under glutamine deprivation. Based on computational predictions of 5 HuR binding sites in the IDH1 mRNA 3'UTR, we subcloned this entire region into a luciferase reporter construct to further study this regulatory interaction. In order to determine the impact of HuR expression in cellular metabolism targeted tracer fate association studies were performed using GC-MS of pellets from cells cultured with 13C-labeled glucose and glutamine in BxPC3 pancreatic cancer cells that differed only in HuR expression. We calculated Pearson correlations of measured metabolites after HuR silencing.

Results: Cell viability was impaired by depletion of both IDH1 and HuR (vs. controls) upon glutamine and glucose withdrawal. Moreover, HuR silencing resulted in potent suppression of IDH1 at the mRNA and protein levels. HuR silencing substantially decremented luciferase activity in the IDH1 3'UTR construct compared to the control (> 2-fold decrease). HuR translocated to the cytoplasm under glutamine deprivation, as previously published observed with glucose deprivation by our group. Metabolic tracer fate association studies revealed that HuR silencing impaired carbon flux from glutamine into fatty acid end products (myristate and palmitate, > 0.9-Pearson's Correlation) under low glucose conditions, implicating HuR's regulatory role in the IDH1-mediated reductive carboxylation step of this metabolic pathway. Additionally, HuR silencing impaired ribose and glycogen synthesis from glucose, and futile carbon exchange fluxes were prevalent.

Conclusions: HuR is important for pancreatic cancer cell survival under glutamine deprivation, as previously observed for glucose deprivation. Carbon flux from glutamine to fatty acid end products suggests a role for HuR in reductive carboxylation of glutamine-derived α-ketoglutarate by IDH1, as a way to maintain adequate lipid synthesis under glucose deprivation. Our Studies provide a rationale to pursue pharmacologic strategies that target HuR or its regulation of IDH1 as a novel treatment of PDA.

Citation Format: Mahsa Zarei, Fernando F. Blanco, Laszlo G. Boros, Charles J. Yeo, Jonathan R. Brody, Jordan M. Winter. Post-transcriptional regulation of IDH1 by the RNA-binding protein HuR is important for pancreatic cancer cell survival under nutrient deprivation. [abstract]. In: Proceedings of the AACR Special Conference: Metabolism and Cancer; Jun 7-10, 2015; Bellevue, WA. Philadelphia (PA): AACR; Mol Cancer Res 2016;14(1_Suppl):Abstract nr B41.

Abstract 1191: The RNA binding protein, HuR, regulates pancreatic cancer cell metabolism

Introduction: Few proteins have been found to be master-regulators of pancreatic ductal adenocarcinoma (PDA) cell metabolism (e.g., LKB1, KRAS). We recently demonstrated that the regulatory RNA binding protein, HuR, binds to numerous metabolic mRNA transcripts and regulates their expression. Additionally, HuR silencing with small interfering RNAs(siRNAs) inhibited growth of PDA cells in vitro under glucose deprivation. Herein, we manipulated HuR expression levels in PDA cells and performed isotope tracer fate association studies to better understand HuR's role in metabolic reprogramming.

Methods: We used 13C-labeled nutrients to map carbon flux in BxPC3 pancreatic cancer cells that were either transiently transfected with siRNA oligos against HuR (siHuR) or scrambled control (siCTRL). Cells were incubated with standard DMEM or mild glucose deprivation (5 mM glucose) for 48 hours, and media were supplemented with [1,2-13C2]-D-glucose or [U-13C5]-L-glutamine tracers for the final 24 hours. A total of 24 samples were snap frozen and prepared for GC-MS isotopomer analysis (3 replicates X 2 different siRNA oligos X 2 isotope tracers X 2 glucose concentrations). Transfection experiments were validated for reduced HuR expression (>70% reduction) and reduced protein expression of at least one metabolic and established HuR target (e.g., IDH1) by immunoblot.

Results: HuR silencing directly impaired fatty acid (Table, line 1-3), ribose (line 5) and glycogen synthesis (line 6). Reductive carboxylation of glutamine-derived isocitrate was impaired and futile carbon exchange fluxes were prevalent (not shown).

Conclusions: HuR enhances metabolic efficiency in PDA cells by directly regulating multiple metabolic pathways. Ongoing microarray studies will highlight which metabolic transcripts are post-transcriptionally regulated by HuR, resulting in the observed phenotype.

Altered metabolites due to HuR silencing in PDA cells ([1,2-13C2]-D-glucose tracer)PathwayMetabolitesiHuR 25mM glucosesiHuR 5 mM glucoseCorrelation1Myristate (C:14) Intracell13C enrichment70.271.01.02Myristate (C:14) intracellFNS (direct)56.060.41.03Oleate (C:18-1) IntracellIndirect synthes-m187.689.51.04Glutam extracell [C2-C5]13C-m1 (m/z198)97.497.91.05RNA-ribose Intracell [C1-C4]13C-m3(m/z242)99.399.10.9846Glucose intracell [C3-C6]Peak area, Glycog-gluc74.180.10.983

Citation Format: Fernando F. Blanco, Mahsa Zarei, Jonathan R. Brody, Laszlo G. Boros, Jordan M. Winter. The RNA binding protein, HuR, regulates pancreatic cancer cell metabolism. [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 1191. doi:10.1158/1538-7445.AM2015-1191

A roadmap for interpreting (13)C metabolite labeling patterns from cells

Measuring intracellular metabolism has increasingly led to important insights in biomedical research. (13)C tracer analysis, although less information-rich than quantitative (13)C flux analysis that requires computational data integration, has been established as a time-efficient method to unravel relative pathway activities, qualitative changes in pathway contributions, and nutrient contributions. Here, we review selected key issues in interpreting (13)C metabolite labeling patterns, with the goal of drawing accurate conclusions from steady state and dynamic stable isotopic tracer experiments.

Abstract 1434: Metformin-induced metabolic changes are k-ras-dependent in animal models of pancreatic cancer

Pancreatic ductal adenocarcinoma (PDA) is an aggressive malignancy, that is very difficult to treat. To date, systemic treatment for PDA, either a single agent or combinations of agents, has shown only modest benefits. Numerous epidemiological studies have reported that metformin (MET), a widely used anti-diabetic drug, provides protective benefits in reducing PDA risk among the diabetic population. Using a stable isotope glucose (GLUC) tracer for dynamic metabolic profiling (SiDMAP), we recently reported that high cholesterol (CHOL) alters the cellular metabolism of MiaPaCa2 (a PDA cell line harboring mutant K-Ras) cells by redirecting glucose-derived acetyl-CoA toward fatty acid (FA) synthesis. This response to MET is depended on the level of intracellular CHOL synthesis. We now performed a SiDMAP study in the LSL-K-RasG12D/+, LSL-Trp53R172H/+, Pdx-1-Cre (KPC) and the LSL-K-RasG12D/+, Pdx-1-Cre (KC) mouse models for PDA, and their wild-type littermates (C57Bl6.129). The mice were treated (or not) with MET (250 mg/kg, i.p. Q5D) and subjected to an Intra Peritoneal GLUC Tolerance Test (IPGTT) pre- and post-MET treatment. The KPC mice with the average tumor volume of 80.83+8.57 mm3 and the KC mice with PanIN lesions (aver. 9 mo old) were put on study. K-Ras mutation, with the presence of the tumor (KPC mice), induced an increase in plasma GLUC production via de novo synthesis by the liver using futile cycling of GLUC derived lactate and pyruvate. MET treatment decreased this flux in mutated (KC) and tumor-bearing animals (KPC), but increased this flux in liver of control mice. MET treatment increased the complete GLUC oxidation into 13CO2 in the pancreas of KC and KPC animals. This indicates that the pancreas in MET-treated animals use less GLUC for RNA, DNA and FA synthesis. For 13CO2 production, we found that tumor growth has to be established; the mutation is not enough to induce changes in this flux. As in plasma, tumor growth increases pancreas lactate production from GLUC. MET treatment dramatically decreased the Warburg effect in the pancreas of mutated (KC) and mutated/tumor-bearing (KPC) mice. Finally, MET decreased GLUC-derived acetyl-CoA delivery to FAS and palmitate in control, mutated and tumor-bearing mice. Immunohistochemical analysis of the tumors from the KPC mice revealed that treatment with MET decreased the staining of phospho-Ser79-ACC by ∼54%, total FAS staining (mainly in the tumor stroma) by ∼43%, and the growth-associated transcription factor HMGA2 by ∼36.7%. These decreases correlated with a decrease in Ki67 staining by almost 80%, indicative of an inhibitory effect of MET on PDA growth. These results suggest that mutant K-Ras is responsible for the metabolic adaptation in both the tumor- (KPC) and non-tumor-bearing animals (KC). Our findings provide a strong rationale for targeting the metabolic changes induced by activated K-RAS in PDA patients which harbor mutations in K-RAS gene in >95% of cases.

Citation Format: Mary Jo Cantoria, Laszlo G. Boros, Hitendra Patel, Haiyong Han, Natalia Ignatenko, Emmanuelle J. Meuillet. Metformin-induced metabolic changes are k-ras-dependent in animal models of pancreatic cancer. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 1434. doi:10.1158/1538-7445.AM2014-1434

5'-AMP-activated protein kinase (AMPK) supports the growth of aggressive experimental human breast cancer tumors

Rapid tumor growth can establish metabolically stressed microenvironments that activate 5'-AMP-activated protein kinase (AMPK), a ubiquitous regulator of ATP homeostasis. Previously, we investigated the importance of AMPK for the growth of experimental tumors prepared from HRAS-transformed mouse embryo fibroblasts and for primary brain tumor development in a rat model of neurocarcinogenesis. Here, we used triple-negative human breast cancer cells in which AMPK activity had been knocked down to investigate the contribution of AMPK to experimental tumor growth and core glucose metabolism. We found that AMPK supports the growth of fast-growing orthotopic tumors prepared from MDA-MB-231 and DU4475 breast cancer cells but had no effect on the proliferation or survival of these cells in culture. We used in vitro and in vivo metabolic profiling with [(13)C]glucose tracers to investigate the contribution of AMPK to core glucose metabolism in MDA-MB-231 cells, which have a Warburg metabolic phenotype; these experiments indicated that AMPK supports tumor glucose metabolism in part through positive regulation of glycolysis and the nonoxidative pentose phosphate cycle. We also found that AMPK activity in the MDA-MB-231 tumors could systemically perturb glucose homeostasis in sensitive normal tissues (liver and pancreas). Overall, our findings suggest that the contribution of AMPK to the growth of aggressive experimental tumors has a critical microenvironmental component that involves specific regulation of core glucose metabolism.

Cancer-associated isocitrate dehydrogenase 1 (IDH1) R132H mutation and d-2-hydroxyglutarate stimulate glutamine metabolism under hypoxia

Mutations in the cytosolic NADP(+)-dependent isocitrate dehydrogenase (IDH1) occur in several types of cancer, and altered cellular metabolism associated with IDH1 mutations presents unique therapeutic opportunities. By altering IDH1, these mutations target a critical step in reductive glutamine metabolism, the metabolic pathway that converts glutamine ultimately to acetyl-CoA for biosynthetic processes. While IDH1-mutated cells are sensitive to therapies that target glutamine metabolism, the effect of IDH1 mutations on reductive glutamine metabolism remains poorly understood. To explore this issue, we investigated the effect of a knock-in, single-codon IDH1-R132H mutation on the metabolism of the HCT116 colorectal adenocarcinoma cell line. Here we report the R132H-isobolome by using targeted (13)C isotopomer tracer fate analysis to trace the metabolic fate of glucose and glutamine in this system. We show that introduction of the R132H mutation into IDH1 up-regulates the contribution of glutamine to lipogenesis in hypoxia, but not in normoxia. Treatment of cells with a d-2-hydroxyglutarate (d-2HG) ester recapitulated these changes, indicating that the alterations observed in the knocked-in cells were mediated by d-2HG produced by the IDH1 mutant. These studies provide a dynamic mechanistic basis for metabolic alterations observed in IDH1-mutated tumors and uncover potential therapeutic targets in IDH1-mutated cancers.

AMPK activation through mitochondrial regulation results in increased substrate oxidation and improved metabolic parameters in models of diabetes

Modulation of mitochondrial function through inhibiting respiratory complex I activates a key sensor of cellular energy status, the 5'-AMP-activated protein kinase (AMPK). Activation of AMPK results in the mobilization of nutrient uptake and catabolism for mitochondrial ATP generation to restore energy homeostasis. How these nutrient pathways are affected in the presence of a potent modulator of mitochondrial function and the role of AMPK activation in these effects remain unclear. We have identified a molecule, named R419, that activates AMPK in vitro via complex I inhibition at much lower concentrations than metformin (IC₅₀ 100 nM vs 27 mM, respectively). R419 potently increased myocyte glucose uptake that was dependent on AMPK activation, while its ability to suppress hepatic glucose production in vitro was not. In addition, R419 treatment of mouse primary hepatocytes increased fatty acid oxidation and inhibited lipogenesis in an AMPK-dependent fashion. We have performed an extensive metabolic characterization of its effects in the db/db mouse diabetes model. In vivo metabolite profiling of R419-treated db/db mice showed a clear upregulation of fatty acid oxidation and catabolism of branched chain amino acids. Additionally, analyses performed using both ¹³C-palmitate and ¹³C-glucose tracers revealed that R419 induces complete oxidation of both glucose and palmitate to CO₂ in skeletal muscle, liver, and adipose tissue, confirming that the compound increases mitochondrial function in vivo. Taken together, our results show that R419 is a potent inhibitor of complex I and modulates mitochondrial function in vitro and in diabetic animals in vivo. R419 may serve as a valuable molecular tool for investigating the impact of modulating mitochondrial function on nutrient metabolism in multiple tissues and on glucose and lipid homeostasis in diabetic animal models.

Abstract C151: Contribution of serine, folate, and glycine metabolism to the ATP, NADPH, and purine requirements of cancer cells

Background: Recent observations on cancer cell metabolism indicate increased serine synthesis from glucose as a marker of poor prognosis. Expression of genes in this pathway also correlate with sensitivity to the antifolate methotrexate (Vazquez A, et al, Cancer Res. 2013 Jan 15;73(2):478-82). Using a large-scale model of human cell metabolism we have predicted that serine synthesis can be routed to a pathway for ATP production. The pathway is composed by reactions from the serine synthesis, one carbon (folate) metabolism and the glycine cleavage system (SOG pathway) and its flux is predicted to increase at high proliferation rates.

Results: Here we show that the SOG pathway is upregulated at the level of gene expression in a subset of human tumors and its level of expression correlates with gene signatures of cell proliferation and Myc targets activation. To investigate the activity of the SOG pathway at the level of metabolic fluxes we estimated the metabolic fluxes of the NCI60 panel of tumor derived cell lines, using previously reported exchange fluxes and a flux balance model of cell metabolism. We show that the estimated rates of reactions in the SOG pathway are highly correlated with the proliferation rates of these cell lines. We also find that the SOG pathway contributes significantly to the energy requirements of biosynthesis, the NADPH requirements of fatty acid synthesis and to the synthesis of purines. Finally, when the PC-3 prostate cancer cell line is subject to treatment with the antifolate methotrexate, we observe a decrease in the ATP levels, an inhibition of the proliferation rate and a decrease in the ribonucleotides and fatty acids synthesized from glucose.

Conclusions: Taken together our results indicate that the SOG pathway activity increases with the rate of cell proliferation and it contributes to the biosynthetic requirements of purines, ATP and NADPH.

Citation Information: Mol Cancer Ther 2013;12(11 Suppl):C151.

Citation Format: Philip M. Tedeschi, Elke K. Markert, Murugesan Gounder, HongXia Lin, Sonia C. Dolfi, Leo Li-Ying Chan, Jean Qiu, Kim M. Hirshfield, Laszlo G. Boros, Joseph R. Bertino, Zoltan N. Oltvai, Alexei Vazquez. Contribution of serine, folate, and glycine metabolism to the ATP, NADPH, and purine requirements of cancer cells. [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2013 Oct 19-23; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2013;12(11 Suppl):Abstract nr C151.

Contribution of serine, folate and glycine metabolism to the ATP, NADPH and purine requirements of cancer cells

Recent observations on cancer cell metabolism indicate increased serine synthesis from glucose as a marker of poor prognosis. We have predicted that a fraction of the synthesized serine is routed to a pathway for ATP production. The pathway is composed by reactions from serine synthesis, one-carbon (folate) metabolism and the glycine cleavage system (SOG pathway). Here we show that the SOG pathway is upregulated at the level of gene expression in a subset of human tumors and that its level of expression correlates with gene signatures of cell proliferation and Myc target activation. We have also estimated the SOG pathway metabolic flux in the NCI60 tumor-derived cell lines, using previously reported exchange fluxes and a personalized model of cell metabolism. We find that the estimated rates of reactions in the SOG pathway are highly correlated with the proliferation rates of these cell lines. We also observe that the SOG pathway contributes significantly to the energy requirements of biosynthesis, to the NADPH requirement for fatty acid synthesis and to the synthesis of purines. Finally, when the PC-3 prostate cancer cell line is treated with the antifolate methotrexate, we observe a decrease in the ATP levels, AMP kinase activation and a decrease in ribonucleotides and fatty acids synthesized from [1,2-¹³C₂]-D-glucose as the single tracer. Taken together our results indicate that the SOG pathway activity increases with the rate of cell proliferation and it contributes to the biosynthetic requirements of purines, ATP and NADPH of cancer cells.

Metabolic reprogramming for producing energy and reducing power in fumarate hydratase null cells from hereditary leiomyomatosis renal cell carcinoma

Fumarate hydratase (FH)-deficient kidney cancer undergoes metabolic remodeling, with changes in mitochondrial respiration, glucose, and glutamine metabolism. These changes represent multiple biochemical adaptations in glucose and fatty acid metabolism that supports malignant proliferation. However, the metabolic linkages between altered mitochondrial function, nucleotide biosynthesis and NADPH production required for proliferation and survival have not been elucidated. To characterize the alterations in glycolysis, the Krebs cycle and the pentose phosphate pathways (PPP) that either generate NADPH (oxidative) or do not (non-oxidative), we utilized [U-¹³C]-glucose, [U-¹³C,¹⁵N]-glutamine, and [1,2- ¹³C₂]-glucose tracers with mass spectrometry and NMR detection to track these pathways, and measured the oxygen consumption rate (OCR) and extracellular acidification rate (ECAR) of growing cell lines. This metabolic reprogramming in the FH null cells was compared to cells in which FH has been restored. The FH null cells showed a substantial metabolic reorganization of their intracellular metabolic fluxes to fulfill their high ATP demand, as observed by a high rate of glucose uptake, increased glucose turnover via glycolysis, high production of glucose-derived lactate, and low entry of glucose carbon into the Krebs cycle. Despite the truncation of the Krebs cycle associated with inactivation of fumarate hydratase, there was a small but persistent level of mitochondrial respiration, which was coupled to ATP production from oxidation of glutamine-derived α–ketoglutarate through to fumarate. [1,2- ¹³C₂]-glucose tracer experiments demonstrated that the oxidative branch of PPP initiated by glucose-6-phosphate dehydrogenase activity is preferentially utilized for ribose production (56-66%) that produces increased amounts of ribose necessary for growth and NADPH. Increased NADPH is required to drive reductive carboxylation of α-ketoglutarate and fatty acid synthesis for rapid proliferation and is essential for defense against increased oxidative stress. This increased NADPH producing PPP activity was shown to be a strong consistent feature in both fumarate hydratase deficient tumors and cell line models.

Transcription factor NRF2 regulates miR-1 and miR-206 to drive tumorigenesis

The mechanisms by which deregulated nuclear factor erythroid-2-related factor 2 (NRF2) and kelch-like ECH-associated protein 1 (KEAP1) signaling promote cellular proliferation and tumorigenesis are poorly understood. Using an integrated genomics and ¹³C-based targeted tracer fate association (TTFA) study, we found that NRF2 regulates miR-1 and miR-206 to direct carbon flux toward the pentose phosphate pathway (PPP) and the tricarboxylic acid (TCA) cycle, reprogramming glucose metabolism. Sustained activation of NRF2 signaling in cancer cells attenuated miR-1 and miR-206 expression, leading to enhanced expression of PPP genes. Conversely, overexpression of miR-1 and miR-206 decreased the expression of metabolic genes and dramatically impaired NADPH production, ribose synthesis, and in vivo tumor growth in mice. Loss of NRF2 decreased the expression of the redox-sensitive histone deacetylase, HDAC4, resulting in increased expression of miR-1 and miR-206, and not only inhibiting PPP expression and activity but functioning as a regulatory feedback loop that repressed HDAC4 expression. In primary tumor samples, the expression of miR-1 and miR-206 was inversely correlated with PPP gene expression, and increased expression of NRF2-dependent genes was associated with poor prognosis. Our results demonstrate that microRNA-dependent (miRNA-dependent) regulation of the PPP via NRF2 and HDAC4 represents a novel link between miRNA regulation, glucose metabolism, and ROS homeostasis in cancer cells.

Iron regulates glucose homeostasis in liver and muscle via AMP-activated protein kinase in mice

Excess iron is associated with hepatic damage and diabetes in humans, although the detailed molecular mechanisms are not known. To investigate how iron regulates glucose homeostasis, we fed C57BL/6J male mice with high-iron (HI) diets (2 or 20 g Fe/kg chow). Mice fed an HI diet exhibited elevated AMP-activated protein kinase (AMPK) activity and impaired insulin signaling in skeletal muscle and liver. Consistent with the increased AMPK activity, glucose uptake was enhanced in mice fed an HI diet. The effects of improved glucose tolerance induced by HI feeding were abolished in transgenic mice with expression of muscle specific dominant-negative AMPK. Glucose output was suppressed in the liver of wild-type mice fed an HI diet, due to decreased expression of gluconeogenic genes and decreased substrate (lactate) from peripheral glycolysis. Iron activated AMPK by increasing deacetylase and decreasing LKB1 acetylation, in turn stimulating the phosphorylation of LKB1 and AMPK. The effects of HI diet were abrogated by treatment of the mice with N-acetyl cysteine, suggesting a redox-dependent mechanism for increasing deacetylase activity. In addition, tissue from iron-fed mice exhibited an elevated AMP/ATP ratio, further contributing to AMPK activation. In summary, a diet high in iron improves glucose tolerance by activating AMPK through mechanisms that include deacetylation.

Diverse mechanisms of growth inhibition by luteolin, resveratrol, and quercetin in MIA PaCa-2 cells: a comparative glucose tracer study with the fatty acid synthase inhibitor C75

The rationale of this dose matching/dose escalating study was to compare a panel of flavonoids-luteolin, resveratrol, and quercetin-against the metabolite flux-controlling properties of a synthetic targeted fatty acid synthase inhibitor drug C75 on multiple macromolecule synthesis pathways in pancreatic tumor cells using [1,2-(13)C(2)]-d-glucose as the single precursor metabolic tracer. MIA PaCa-2 pancreatic adenocarcinoma cells were cultured for 48 h in the presence of 0.1% DMSO (control), or 50 or 100 μM of each test compound, while intracellular glycogen, RNA ribose, palmitate and cholesterol as well as extra cellular (13)CO(2), lactate and glutamate production patterns were measured using gas chromatography/mass spectrometry (GC/MS) and stable isotope-based dynamic metabolic profiling (SiDMAP). The use of 50% [1,2-(13)C(2)]-d-glucose as tracer resulted in an average of 24 excess (13)CO(2) molecules for each 1,000 CO(2) molecule in the culture media, which was decreased by 29 and 33% (P < 0.01) with 100 μM C75 and luteolin treatments, respectively. Extracellular tracer glucose-derived (13)C-labeled lactate fractions (Σm) were between 45.52 and 47.49% in all cultures with a molar ratio of 2.47% M + 1/Σm lactate produced indirectly by direct oxidation of glucose in the pentose cycle in control cultures; treatment with 100 μM C75 and luteolin decreased this figure to 1.80 and 1.67%. The tracer glucose-derived (13)C labeled fraction (Σm) of ribonucleotide ribose was 34.73% in controls, which was decreased to 20.58 and 8.45% with C75, 16.15 and 6.86% with luteolin, 27.66 and 19.25% with resveratrol, and 30.09 and 25.67% with quercetin, respectively. Luteolin effectively decreased nucleotide precursor synthesis pentose cycle flux primarily via the oxidative branch, where we observed a 41.74% flux (M + 1/Σm) in control cells, in comparison with only a 37.19%, 32.74%, or a 26.57%, 25.47% M + 1/Σm flux (P < 0.001) after 50 or 100 μM C75 or luteolin treatment. Intracellular de novo fatty acid palmitate (C16:0) synthesis was severely and equally blocked by C75 and luteolin treatments indicated by the 5.49% (control), 2.29 or 2.47% (C75) and 2.21 or 2.73% (luteolin) tracer glucose-derived (13)C-labeled fractions, respectively. On the other hand there was a significant 192 and 159% (P < 0.001), and a 103 and 117% (P < 0.01) increase in tracer glucose-derived cholesterol after C75 or luteolin treatment. Only resveratrol and quercetin at 100 μM inhibited tracer glucose-derived glycogen labeling (Σm) and turnover by 34.8 and 23.8%, respectively. The flavonoid luteolin possesses equal efficacy to inhibit fatty acid palmitate de novo synthesis as well as nucleotide RNA ribose turnover via the oxidative branch of the pentose cycle in comparison with the targeted fatty acid synthase inhibitor synthetic compound C75. Luteolin is also effective in stringently controlling glucose entry and anaplerosis in the TCA cycle, while it promotes less glucose flux towards cholesterol synthesis than that of C75. In contrast, quercetin and resveratrol inhibit glycogen synthesis and turnover as their underlying mechanism of controlling tumor cell proliferation. Therefore the flavonoid luteolin controls fatty and nucleic acid syntheses as well as energy production with pharmacological strength, which can be explored as a non-toxic natural treatment modality for pancreatic cancer.

Assessment of usnic acid toxicity in rat primary hepatocytes using ¹³C isotopomer distribution analysis of lactate, glutamate and glucose

The lichen metabolite usnic acid (UA) has been promoted as a dietary supplement for weight loss, although cases of hepatotoxicity have been reported. Here we evaluated UA-associated hepatotoxicity in vitro using isolated rat hepatocytes. We measured cell viability and ATP content to evaluate UA induced cytotoxicity and applied (13)C isotopomer distribution measuring techniques to gain a better understanding of glucose metabolism during cytotoxicity. The cells were exposed to 0, 1, 5 or 10 μM UA concentrations for 2, 6 or 24h. Aliquots of media were collected at the end of these time periods and the (13)C mass isotopomer distribution determined for CO(2), lactate, glucose and glutamate. The 1 μM UA exposure did not appear to cause significant change in cell viability compared to controls. However, the 5 and 10 μM UA concentrations significantly reduced cell viability as exposure time increased. Similar results were obtained for ATP depletion experiments. The 1 and 5 μM UA doses suggest increased oxidative phosphorylation. Conversely, oxidative phosphorylation and gluconeogenesis were dramatically inhibited by 10 μM UA. Augmented oxidative phosphorylation at the lower UA concentrations may be an adaptive response by the cells to compensate for diminished mitochondrial function.

Pharmacological targeting of glucagon and glucagon-like peptide 1 receptors has different effects on energy state and glucose homeostasis in diet-induced obese mice

Pharmacologic contributions of directly agonizing glucagon-like peptide 1 (GLP-1) receptor or antagonizing glucagon receptor (GCGR) on energy state and glucose homeostasis were assessed in diet-induced obese (DIO) mice. Metabolic rate and respiratory quotient (RQ), hyperglycemic clamp, stable isotope-based dynamic metabolic profiling (SiDMAP) studies of (13)C-labeled glucose during glucose tolerance test (GTT) and gene expression were assessed in cohorts of DIO mice after a single administration of GLP-1 analog [GLP-1-(23)] or anti-GCGR antibody (Ab). GLP-1-(23) and GCGR Ab similarly improved GTT. GLP-1-(23) decreased food intake and body weight trended lower. GCGR Ab modestly decreased food intake without significant effect on body weight. GLP-1-(23) and GCGR Ab decreased RQ with GLP-1, causing a greater effect. In a hyperglycemic clamp, GLP-1-(23) reduced hepatic glucose production (HGP), increased glucose infusion rate (GIR), increased glucose uptake in brown adipose tissue, and increased whole-body glucose turnover, glycolysis, and rate of glycogen synthesis. GCGR Ab slightly decreased HGP, increased GIR, and increased glucose uptake in the heart. SiDMAP showed that GLP-1-(23) and GCGR Ab increased (13)C lactate labeling from glucose, indicating that liver, muscle, and other organs were involved in the rapid disposal of glucose from plasma. GCGR Ab and GLP-1-(23) caused different changes in mRNA expression levels of glucose- and lipid metabolism-associated genes. The effect of GLP-1-(23) on energy state and glucose homeostasis was greater than GCGR Ab. Although GCGR antagonism is associated with increased circulating levels of GLP-1, most GLP-1-(23)-associated pharmacologic effects are more pronounced than GCGR Ab.

Fructose impairs glucose-induced hepatic triglyceride synthesis

Obesity, type 2 diabetes and hyperlipidemia frequently coexist and are associated with significantly increased morbidity and mortality. Consumption of refined carbohydrate and particularly fructose has increased significantly in recent years and has paralled the increased incidence of obesity and diabetes. Human and animal studies have demonstrated that high dietary fructose intake positively correlates with increased dyslipidemia, insulin resistance, and hypertension. Metabolism of fructose occurs primarily in the liver and high fructose flux leads to enhanced hepatic triglyceride accumulation (hepatic steatosis). This results in impaired glucose and lipid metabolism and increased proinflammatory cytokine expression. Here we demonstrate that fructose alters glucose-stimulated expression of activated acetyl CoA carboxylase (ACC), pSer hormone sensitive lipase (pSerHSL) and adipose triglyceride lipase (ATGL) in hepatic HepG2 or primary hepatic cell cultures in vitro. This was associated with increased de novo triglyceride synthesis in vitro and hepatic steatosis in vivo in fructose- versus glucose-fed and standard-diet fed mice. These studies provide novel insight into the mechanisms involved in fructose-mediated hepatic hypertriglyceridemia and identify fructose-uptake as a new potential therapeutic target for lipid-associated diseases.

Fructose induces transketolase flux to promote pancreatic cancer growth

Carbohydrate metabolism via glycolysis and the tricarboxylic acid cycle is pivotal for cancer growth, and increased refined carbohydrate consumption adversely affects cancer survival. Traditionally, glucose and fructose have been considered as interchangeable monosaccharide substrates that are similarly metabolized, and little attention has been given to sugars other than glucose. However, fructose intake has increased dramatically in recent decades and cellular uptake of glucose and fructose uses distinct transporters. Here, we report that fructose provides an alternative substrate to induce pancreatic cancer cell proliferation. Importantly, fructose and glucose metabolism are quite different; in comparison with glucose, fructose induces thiamine-dependent transketolase flux and is preferentially metabolized via the nonoxidative pentose phosphate pathway to synthesize nucleic acids and increase uric acid production. These findings show that cancer cells can readily metabolize fructose to increase proliferation. They have major significance for cancer patients given dietary refined fructose consumption, and indicate that efforts to reduce refined fructose intake or inhibit fructose-mediated actions may disrupt cancer growth.

Dual modulation of both lipid oxidation and synthesis by peroxisome proliferator-activated receptor-gamma coactivator-1alpha and -1beta in cultured myotubes

The peroxisome proliferator-activated receptor gamma coactivator-1 (PGC-1) family is a key regulator of mitochondrial function, and reduced mRNA expression may contribute to muscle lipid accumulation in obesity and type 2 diabetes. To characterize the effects of PGC-1 on lipid metabolism, we overexpressed PGC-1alpha and PGC-1beta in C2C12 myotubes using adenoviral vectors. Both PGC-1alpha and -1beta increased palmitate oxidation [31% (P<0.01) and 26% (P<0.05), respectively] despite reductions in cellular uptake [by 6% (P<0.05) and 21% (P<0.001)]. Moreover, PGC-1alpha and -1beta increased mRNA expression of genes regulating both lipid oxidation (e.g., CPT1b and ACADL/M) and synthesis (FAS, CS, ACC1/2, and DGAT1). To determine the net effect, we assessed lipid composition in PGC-1-expressing cells. Total lipid content decreased by 42% in palmitate-loaded serum-starved cells overexpressing PGC-1alpha (P<0.05). In contrast, in serum-replete cells, total lipid content was not significantly altered, but fatty acids C14:0, C16:0, C18:0, and C18:1 were increased 2- to 4-fold for PGC-1alpha/beta (P<0.05). Stable isotope-based dynamic metabolic profiling in serum-replete cells labeled with (13)C substrates revealed both increased de novo fatty acid synthesis from glucose and increased fatty acid synthesis by chain elongation with either PGC-1alpha or -1beta expression. These results indicate that PGC-1 can promote both lipid oxidation and synthesis, with net balance determined by the nutrient/hormonal environment.-Espinoza, D. O., Boros, L. G., Crunkhorn, S., Gami, H., Patti, M.-E. Dual Modulation of both lipid oxidation and synthesis by peroxisome proliferator-activated receptor-gamma coactivator-1alpha and -1beta in cultured myotubes.

Single valproic acid treatment inhibits glycogen and RNA ribose turnover while disrupting glucose-derived cholesterol synthesis in liver as revealed by the [U-C(6)]-d-glucose tracer in mice

Previous genetic and proteomic studies identified altered activity of various enzymes such as those of fatty acid metabolism and glycogen synthesis after a single toxic dose of valproic acid (VPA) in rats. In this study, we demonstrate the effect of VPA on metabolite synthesis flux rates and the possible use of abnormal (13)C labeled glucose-derived metabolites in plasma or urine as early markers of toxicity. Female CD-1 mice were injected subcutaneously with saline or 600 mg/kg) VPA. Twelve hours later, the mice were injected with an intraperitoneal load of 1 g/kg [U-(13)C]-d-glucose. (13)C isotopomers of glycogen glucose and RNA ribose in liver, kidney and brain tissue, as well as glucose disposal via cholesterol and glucose in the plasma and urine were determined. The levels of all of the positional (13)C isotopomers of glucose were similar in plasma, suggesting that a single VPA dose does not disturb glucose absorption, uptake or hepatic glucose metabolism. Three-hour urine samples showed an increase in the injected tracer indicating a decreased glucose re-absorption via kidney tubules. (13)C labeled glucose deposited as liver glycogen or as ribose of RNA were decreased by VPA treatment; incorporation of (13)C via acetyl-CoA into plasma cholesterol was significantly lower at 60 min. The severe decreases in glucose-derived carbon flux into plasma and kidney-bound cholesterol, liver glycogen and RNA ribose synthesis, as well as decreased glucose re-absorption and an increased disposal via urine all serve as early flux markers of VPA-induced adverse metabolic effects in the host.

Abnormalities in glucose uptake and metabolism in imatinib-resistant human BCR-ABL-positive cells

The development of imatinib resistance has become a significant therapeutic problem in which the etiology seems to be multifactorial and poorly understood. As of today, clinical criteria to predict the development of imatinib resistance in chronic myelogenous leukemia (CML), other than rebound of the myeloproliferation, are under development. However, there is evidence that the control of glucose-substrate flux is an important mechanism of the antiproliferative action of imatinib because imatinib-resistant gastrointestinal stromal KIT-positive tumors reveal highly elevated glucose uptake in radiologic images. We used nuclear magnetic resonance spectroscopy and gas chromatography mass spectrometry to assess (13)C glucose uptake and metabolism (glycolysis, TCA cycle, and nucleic acid ribose synthesis) during imatinib treatment in CML cell lines with different sensitivities to imatinib. Our results show that sensitive K562-s and LAMA84-s BCR-ABL-positive cells have decreased glucose uptake, decreased lactate production, and an improved oxidative TCA cycle following imatinib treatment. The resistant K562-r and LAMA84-r cells maintained a highly glycolytic metabolic phenotype with elevated glucose uptake and lactate production. In addition, oxidative synthesis of RNA ribose from (13)C-glucose via glucose-6-phosphate dehydrogenase was decreased, and RNA synthesis via the nonoxidative transketolase pathway was increased in imatinib-resistant cells. CML cells which exhibited a (oxidative/nonoxidative) flux ratio for nucleic acid ribose synthesis of >1 were sensitive to imatinib. The resistant K562-r and LAMA84-r exhibited a (oxidative/nonoxidative) flux ratio of <0.7. The changes in glucose uptake and metabolism were accompanied by intracellular translocation of GLUT-1 from the plasma membrane into the intracellular fraction in sensitive cells treated with imatinib, whereas GLUT-1 remained located at the plasma membrane in LAMA84-r and K562-r cells. The total protein load of GLUT-1 was unchanged among treated sensitive and resistant cell lines. In summary, elevated glucose uptake and nonoxidative glycolytic metabolic phenotype can be used as sensitive markers for early detection of imatinib resistance in BCR-ABL-positive cells.

In utero nicotine exposure alters fetal rat lung alveolar type II cell proliferation, differentiation, and metabolism

We recently suggested that alveolar interstitial fibroblast-to-myofibroblast transdifferentiation may be a key mechanism underlying in utero nicotine-induced lung injury. However, the effects of in utero nicotine exposure on fetal alveolar type II (ATII) cells have not been fully determined. Placebo, nicotine (1 mg/kg), or nicotine (1 mg/kg) + the peroxisome proliferator-activated receptor (PPAR)-γ agonist prostaglandin J2 (PGJ2, 0.3 mg/kg) was administered intraperitoneally once daily to time-mated pregnant Sprague-Dawley rats from embryonic day 6 until their death on embryonic day 20. Fetal ATII cells were isolated, and ATII cell proliferation, differentiation (surfactant synthesis), and metabolism (metabolic profiling with the stable isotope [1,2-13C2]-d-glucose) were determined after nicotine exposure in utero or in vitro. In utero nicotine exposure significantly stimulated ATII cell proliferation, differentiation, and metabolism. Although the effects on ATII cell proliferation and metabolism were almost completely prevented by concomitant treatment with PGJ2, the effects on surfactant synthesis were not. On the basis of in utero and in vitro data, we conclude that surfactant synthesis is stimulated by nicotine's direct effect on ATII cells, whereas cell proliferation and metabolism are affected via a paracrine mechanism(s) secondary to its effects on the adepithelial fibroblasts. These data provide evidence for direct and indirect effects of in utero nicotine exposure on fetal ATII cells that could permanently alter the “developmental program” of the developing lung. More importantly, concomitant administration of PPAR-γ agonists can effectively attenuate many of the effects of in utero exposure to nicotine on ATII cells.

K-ras codon-specific mutations produce distinctive metabolic phenotypes in NIH3T3 mice [corrected] fibroblasts

Among K-ras mutations, codon 12 mutations have been identified as those conferring a more aggressive phenotype. This aggressiveness is primarily associated with slow proliferation but greatly increased resistance to apoptosis. Using transfected NIH3T3 fibroblasts with a mutated K-ras minigene either at codon 12 (K12) or at codon 13 (K13), and taking advantage of [1,2-13C2]glucose tracer labeling, we show that codon 12 mutant K-ras (K12)-transformed cells exhibit greatly increased glycolysis with only a slight increase in activity along pathways that produce nucleic acid and lipid synthesis precursors in the oxidative branch of the pentose phosphate pathway and via pyruvate dehydrogenase flux. K13 mutants display a modest increase in anaerobic glycolysis associated with a large increase in oxidative pentose phosphate pathway activity and pyruvate dehydrogenase flux. The distinctive differences in metabolic profiles of K12 and K13 codon mutated cells indicate that a strong correlation exists between the flow of glucose carbons towards either increased anaerobic glycolysis, and resistance to apoptosis (K12), or increased macromolecule synthesis, rapid proliferation, and increased sensitivity to apoptosis.

Fermented Wheat Germ Extract (Avemar) in the Treatment of Cancer and Autoimmune Diseases

Avemar, the product of industrial fermentation of wheat germ, possesses unique cancer-fighting characteristics. Taken orally, Avemar can inhibit metastatic tumor dissemination and proliferation during and after chemotherapy, surgery, or radiation. Benefits of Avemar treatment have been shown in various human cancers, in cultures of in vitro grown cancer cells, in the prevention of chemical carcinogenesis, and also in some autoimmune conditions. This document reviews the clinical and experimental results obtained with this extract so far. Special references are made for its safety, including its coadministration with anticancer drugs, as well as for its immunomodulatory activity, its molecular targets, and its use in cancer clinical trials.

Polymorphism of the TNF-alpha, HSP70-2, and CD14 genes increases susceptibility to severe acute pancreatitis

OBJECTIVES

Proinflammatory cytokines and heat shock proteins play fundamental roles in the pathogenesis of acute pancreatitis. We studied whether polymorphisms of the tumor necrosis factor alpha (TNF-alpha), heat shock protein 70-2 (HSP70-2), and CD14 genes correlate with the severity of acute pancreatitis.

METHODS

Patients with acute pancreatitis (n = 77) of mixed etiology were grouped according to the severity of the disease on the basis of the Ranson scores. Healthy blood donors (n = 71) served as controls. TNF-alpha-308 polymorphism was determined by NcoI RFLP, HSP70-2 polymorphism by PstI RFLP, and CD14-159 polymorphism by melting point analysis.

RESULTS

There was a moderate increase in the frequency of the TNF1/2 genotype (P = 0.046) among patients with severe acute pancreatitis as compared with those with mild disease. A more significant increase was observed in the frequency of the HSP70-2 G allele between groups of patients with mild or severe pancreatitis (18.9% vs. 53%; P < 0.001). Conversely, the A/A genotype was markedly more frequent among the patients with mild pancreatitis (P < 0.0001). There was no significant correlation between CD14-159 promoter polymorphism and the severity of pancreatitis.

CONCLUSION

High frequencies of the HSP70-2 G and the TNF-alpha -308 A alleles were associated with risk of severe acute pancreatitis. Genotype assessments may be important prognostic tools to predict disease severity and the course of acute pancreatitis. Therefore, genotype assessments may also be used to guide treatment or to identify risk populations for severe acute pancreatitis.

Metabolic sensitivity of pancreatic tumour cell apoptosis to glycogen phosphorylase inhibitor treatment

Inhibitors of glycogen breakdown regulate glucose homeostasis by limiting glucose production in diabetes. Here we demonstrate that restrained glycogen breakdown also inhibits cancer cell proliferation and induces apoptosis through limiting glucose oxidation, as well as nucleic acid and de novo fatty acid synthesis. Increasing doses (50-100 microM) of the glycogen phosphorylase inhibitor CP-320626 inhibited [1,2-(13)C(2)]glucose stable isotope substrate re-distribution among glycolysis, pentose and de novo fatty acid synthesis in MIA pancreatic adenocarcinoma cells. Limited oxidative pentose-phosphate synthesis, glucose contribution to acetyl CoA and de novo fatty acid synthesis closely correlated with decreased cell proliferation. The stable isotope-based dynamic metabolic profile of MIA cells indicated a significant dose-dependent decrease in macromolecule synthesis, which was detected at lower drug doses and before the appearance of apoptosis markers. Normal fibroblasts (CRL-1501) did not show morphological or metabolic signs of apoptosis likely due to their slow rate of growth and metabolic activity. This indicates that limiting carbon re-cycling and rapid substrate mobilisation from glycogen may be an effective and selective target site for new drug development in rapidly dividing cancer cells. In conclusion, pancreatic cancer cell growth arrest and death are closely associated with a characteristic decrease in glycogen breakdown and glucose carbon re-distribution towards RNA/DNA and fatty acids during CP-320626 treatment.

Growth stimulation of COX-2-negative pancreatic cancer by a selective COX-2 inhibitor

Cyclooxygenase 2 (COX-2) inhibitors are promising antiangiogenic agents in several preclinical models. The aim of the present study was to evaluate the effect of selective COX-2 inhibitors on vascular endothelial growth factor (VEGF) production in vitro and angiogenesis and growth of pancreatic cancer in vivo, focusing on putative differences between COX-2-negative and COX-2-positive tumors. VEGF production and angiogenesis in vitro were determined by ELISA and endothelial cell migration assay. To determine whether the effect of COX-2 inhibitors was mediated by peroxisome proliferator-activated receptor gamma (PPAR-gamma), we used a dominant-negative PPAR-gamma and a pharmacologic inhibitor. In vitro findings were validated in a pancreatic cancer animal model. Microvessel density was assessed by CD31 immunostaining. Intratumoral prostaglandin and VEGF levels were measured by mass spectroscopy and ELISA. Selective COX-2 inhibitors had a concentration-dependent effect on VEGF production in vitro. Higher concentrations increased VEGF levels and stimulated angiogenesis by activating PPAR-gamma. In vivo, nimesulide increased VEGF production by cancer cells in COX-2-positive and COX-2-negative pancreatic tumors. In COX-2-negative pancreatic cancer, this effect was associated with an increase in angiogenesis and growth. In COX-2-positive pancreatic cancer, the nimesulide-induced increase of VEGF production by the cancer cells was offset by a decrease in VEGF production by the nonmalignant cell types leading to reduced tumor angiogenesis and growth. Selective COX-2 inhibitors had opposite effects on growth and angiogenesis in pancreatic cancer depending on COX-2 expression. These findings imply that assessing the COX-2 profile of the pancreatic tumor is mandatory before initiating therapy with a selective COX-2 inhibitor.

Growth Stimulation of COX-2–Negative Pancreatic Cancer by a Selective COX-2 Inhibitor

Cyclooxygenase 2 (COX-2) inhibitors are promising antiangiogenic agents in several preclinical models. The aim of the present study was to evaluate the effect of selective COX-2 inhibitors on vascular endothelial growth factor (VEGF) production in vitro and angiogenesis and growth of pancreatic cancer in vivo, focusing on putative differences between COX-2–negative and COX-2–positive tumors. VEGF production and angiogenesis in vitro were determined by ELISA and endothelial cell migration assay. To determine whether the effect of COX-2 inhibitors was mediated by peroxisome proliferator–activated receptor γ (PPAR-γ), we used a dominant-negative PPAR-γ and a pharmacologic inhibitor. In vitro findings were validated in a pancreatic cancer animal model. Microvessel density was assessed by CD31 immunostaining. Intratumoral prostaglandin and VEGF levels were measured by mass spectroscopy and ELISA. Selective COX-2 inhibitors had a concentration-dependent effect on VEGF production in vitro. Higher concentrations increased VEGF levels and stimulated angiogenesis by activating PPAR-γ. In vivo, nimesulide increased VEGF production by cancer cells in COX-2–positive and COX-2–negative pancreatic tumors. In COX-2–negative pancreatic cancer, this effect was associated with an increase in angiogenesis and growth. In COX-2–positive pancreatic cancer, the nimesulide-induced increase of VEGF production by the cancer cells was offset by a decrease in VEGF production by the nonmalignant cell types leading to reduced tumor angiogenesis and growth. Selective COX-2 inhibitors had opposite effects on growth and angiogenesis in pancreatic cancer depending on COX-2 expression. These findings imply that assessing the COX-2 profile of the pancreatic tumor is mandatory before initiating therapy with a selective COX-2 inhibitor.

Chromosomal aberrations in human lymphocytes exposed to the anticholinesterase pesticide isofenphos with mechanisms of leukemogenesis

Human lymphocytes were exposed to the leukemogenic pesticide isofenphos (IFP) to investigate its effects on chromosomal DNA and cholinergic homeostasis using cholinesterase activity as a marker. Isolated peripheral lymphocytes were administered concentrations of IFP ranging from 0.1 ng/ml to 10 microg/ml. The absence (Group 1) and presence (Group 2) of DNA repair inhibitors 4 mM hydroxyurea (HU), 40 microM cytosine arabinoside (ARA-C) and an NADPH regenerating system (NRS) (Group 3) were analyzed at 1, 6 and 24 h by single cell gel electrophoresis using the comet assay. Significant damage to DNA directly from IFP at 1 h by remarkably low concentrations was observed in Group 1, escalating in Group 2 with DNA repair inhibition, while Group 3 disruptions were highest due to the presence of the NRS P-450 microsomal fraction conducive to producing reactive IFP-oxon and N-desalkyl metabolites. The extent of DNA aberrations increased further in parallel within the groups at 6 and 24 h. Male and female chemical sensitivities were similar on average (P < 0.01). Cholinesterase activity measured in a satellite group was inhibited with 0.1 microg/ml IFP by 69, 62, and 48% at 1, 6, and 24 h, respectively, indicating gradual induction of compensatory synthesis. Restoration of cholinergic homeostasis may be exceptionally impaired at higher IFP concentrations from acetyl-CoA depletion [Leuk. Res. 25 (2001) 883]. In summary, these studies reveal that exposure to the organophosphate pesticide isofenphos induces human DNA mutation beyond endogenous repair capacity and disrupts cholinergic nuclear signaling affectively constructing the mutator phenotype of leukemogenesis.

Metabolic strategy of boar spermatozoa revealed by a metabolomic characterization

Metabolomic characteristics in boar spermatozoa were studied using [1,2-(13)C(2)]glucose and mass isotopomer analysis. In boar spermatozoa, glycolysis was the main pathway of glucose utilization producing lactate/pyruvate, whereas no gluconeogenesis was seen. Slight glycogen synthesis through the direct pathway and some incorporation of pyruvate into the Krebs cycle also took place. Neither RNA ribose-5-phosphate nor fatty acid synthesis from glucose occurred despite the detection of pyruvate dehydrogenase activity. In contrast to the known metabolic activities in dog sperm, boar spermatozoa have low levels of energy production and biosynthetic activities suggesting two different metabolic profiles for the two different phenotypes.

Spermatogenetic expression of RNA-binding motif protein 7, a protein that interacts with splicing factors

We have previously shown that a ubiquitously expressed RNA splicing factor, RNA-binding motif 7 (RBM7), cloned from a testis complementary DNA library, enhances messenger RNA (mRNA) splicing in vitro and is expressed in a cell-restricted fashion. Herein, we detail its mRNA and protein expression in the rodent testis. RNA in situ hybridization shows that Rbm7 expression in rat germ cells closely parallels the entry and progression of meiosis. The expression commences in type B spermatogonia, it rises during the preleptotene stage, peaks in leptotene spermatocytes, and declines afterward, but increases again in stage-associated pachytene spermatocytes. An affinity-purified polyclonal antibody raised against a peptide corresponding to amino acids 202-224 of the mouse RBM7 recognized the predicted 35 kd protein both in testicular lysates and in in vitro translation reactions. Consistent with the in situ hybridization results, RBM7 immunoreactivity was also detected in type B spermatogonia, spanned the entire period of spermatocyte development, and extended to round and early elongated spermatids. Moreover, RBM7 appeared nuclear up to the mid pachytene stage and became cytoplasmic thereafter. Consistent with its role in RNA splicing, yeast 2-hybrid and glutathione S-transferase pull-down assays show that RBM7 interacts with splicing factor 3b subunit 2 (SAP145), and with the splicing regulator, SRp20. These interactions and the nuclear localization of RBM7 provide insights into its function in pre-mRNA processing in developing spermatocytes during entry into meiosis and progression through the meiotic prophase.

Cultured pancreatic ductal cells undergo cell cycle re-distribution and beta-cell-like differentiation in response to glucagon-like peptide-1

The intestinal hormone glucagon-like peptide-1 (GLP-1) has been shown to promote an increase in pancreatic beta-cell mass via proliferation of islet cells and differentiation of non-insulin-secreting cells. In this study, we have characterized some of the events that lead to the differentiation of pancreatic ductal cells in response to treatment with human GLP-1. Rat pancreatic ductal (ARIP) cells were cultured in the presence of GLP-1 and analyzed for cell counting, cell cycle distribution, expression of cyclin-dependent-kinase (Cdk) inhibitors, transcription of beta-cell-specific genes, loss of ductal-like phenotype and acquisition of beta-cell-like gene expression profile. Exposure of ARIP cells to 10 nM GLP-1 induced a significant reduction in the cell replication rate and a significant decrease in the percentage of cells in S phase of the cell cycle. This was associated with an increase in the number of cells in G0-G1 phase and a reduction of cells in G2-M phase. Western blot analysis for the Cdk inhibitors, kinase inhibitor protein 1 (p27(Kip1)) and Cdk-interacting protein 1 (p21(Cip1)), demonstrated a significant increase in p27(Kip1) and p21(Cip1) levels within the first 24 h from the beginning of GLP-1 treatment. As cells slowed down their proliferation rate, GLP-1 also induced a time-dependent expression of various beta-cell-specific mRNAs. The glucose transporter GLUT-2 was the first of those factors to be expressed (24 h treatment), followed by insulin (44 h) and finally by the enzyme glucokinase (56 h). In addition, immunocytochemistry analysis showed that GLP-1 induced a time-dependent down-regulation of the ductal marker cytokeratin-20 (CK-20) and a time-dependent induction of insulin expression. Finally, GLP-1 promoted a glucose-dependent secretion of insulin, as demonstrated by HPLC and RIA analyses of the cell culture medium. The present study has demonstrated that GLP-1 induces a cell cycle re-distribution with a decrease in cell proliferation rate prior to promoting the differentiation of cells towards an endocrine-like phenotype.

Fermented wheat germ extract inhibits glycolysis/pentose cycle enzymes and induces apoptosis through poly(ADP-ribose) polymerase activation in Jurkat T-cell leukemia tumor cells

The fermented extract of wheat germ, trade name Avemar, is a complex mixture of biologically active molecules with potent anti-metastatic activities in various human malignancies. Here we report the effect of Avemar on Jurkat leukemia cell viability, proliferation, cell cycle distribution, apoptosis, and the activity of key glycolytic/pentose cycle enzymes that control carbon flow for nucleic acid synthesis. The cytotoxic IC(50) concentration of Avemar for Jurkat tumor cells is 0.2 mg/ml, and increasing doses of the crude powder inhibit Jurkat cell proliferation in a dose-dependent fashion. At concentrations higher than 0.2 mg/ml, Avemar inhibits cell growth by more than 50% (72 h of incubation), which is preceded by the appearance of a sub-G(1) peak on flow histograms at 48 h. Laser scanning cytometry of propidium iodide- and annexin V-stained cells indicated that the growth-inhibiting effect of Avemar was consistent with a strong induction of apoptosis. Inhibition by benzyloxycarbonyl-Val-Ala-Asp fluoromethyl ketone of apoptosis but increased proteolysis of poly(ADP-ribose) indicate caspases mediate the cellular effects of Avemar. Activities of glucose-6-phosphate dehydrogenase and transketolase were inhibited in a dose-dependent fashion, which correlated with decreased (13)C incorporation and pentose cycle substrate flow into RNA ribose. This decrease in pentose cycle enzyme activities and carbon flow toward nucleic acid precursor synthesis provide the mechanistic understanding of the cell growth-controlling and apoptosis-inducing effects of fermented wheat germ. Avemar exhibits about a 50-fold higher IC(50) (10.02 mg/ml) for peripheral blood lymphocytes to induce a biological response, which provides the broad therapeutic window for this supplemental cancer treatment modality with no toxic effects.

Loss of regulation of lipogenesis in the Zucker diabetic rat. II. Changes in stearate and oleate synthesis

De novo lipogenesis and dietary fat uptake are two major sources of fatty acid deposits in fat of obese animals. To determine the relative contribution of fatty acids from these two sources in obesity, we have determined the distribution of c16 and c18 fatty acids of triglycerides in plasma, liver, and epididymal fat pad of Zucker diabetic fatty (ZDF) rats and their lean littermates (ZL) under two isocaloric dietary fat conditions. Lipogenesis was also determined using the deuterated water method. Conversion of palmitate to stearate and stearate to oleate was calculated from the deuterium incorporation by use of the tracer dilution principle. In the ZL rat, lipogenesis was suppressed from 70 to 24%, conversion of palmitate to stearate from 86 to 78%, and conversion of stearate to oleate from 56 to 7% in response to an increase in the dietary fat-to-carbohydrate ratio. The results suggest that suppression of fatty acid synthase and stearoyl-CoA desaturase activities is a normal adaptive mechanism to a high-fat diet. In contrast, de novo lipogenesis, chain elongation, and desaturation were not suppressed by dietary fat in the ZDF rat. The lack of ability to adapt to a high-fat diet resulted in a higher plasma triglyceride concentration and excessive fat accumulation from both diet and de novo synthesis in the ZDF rat.

Metabolic control analysis in drug discovery and disease

Metabolic control analysis (MCA) provides a quantitative description of substrate flux in response to changes in system parameters of complex enzyme systems. Medical applications of the approach include the following: understanding the threshold effect in the manifestation of metabolic diseases; investigating the gene dose effect of aneuploidy in inducing phenotypic transformation in cancer; correlating the contributions of individual genes and phenotypic characteristics in metabolic disease (e.g., diabetes); identifying candidate enzymes in pathways suitable as targets for cancer therapy; and elucidating the function of "silent" genes by identifying metabolic features shared with genes of known pathways. MCA complements current studies of genomics and proteomics, providing a link between biochemistry and functional genomics that relates the expression of genes and gene products to cellular biochemical and physiological events. Thus, it is an important tool for the study of genotype-phenotype correlations. It allows genes to be ranked according to their importance in controlling and regulating cellular metabolic networks. We can expect that MCA will have an increasing impact on the choice of targets for intervention in drug discovery.

A metabolic hypothesis of cell growth and death in pancreatic cancer

INTRODUCTION

Tumor cells, just as other living cells, possess the potential for proliferation, differentiation, cell cycle arrest, and apoptosis. There is a specific metabolic phenotype associated with each of these conditions, characterized by the production of both energy and special substrates necessary for the cells to function in that particular state. Unlike that of normal living cells, the metabolic phenotype of tumor cells supports the proliferative state.

AIM

To present the metabolic hypothesis that (1) cell transformation and tumor growth are associated with the activation of metabolic enzymes that increase glucose carbon utilization for nucleic acid synthesis, while enzymes of the lipid and amino acid synthesis pathways are activated in tumor growth inhibition, and (2) phosphorylation and allosteric and transcriptional regulation of intermediary metabolic enzymes and their substrate availability together mediate and sustain cell transformation from one condition to another.

CONCLUSION

Evidence is presented that demonstrates opposite changes in metabolic phenotypes induced by TGF-beta, a cell-transforming agent, and tumor growth-inhibiting phytochemicals such as genistein and Avemar, or novel synthetic anti-leukemic drugs such as STI571 (Gleevec). Intermediary metabolic enzymes that mediate the growth signaling pathways and promote malignant cell transformation may serve as high-efficacy nongenetic novel targets for cancer therapies.

Gleevec (STI571) influences metabolic enzyme activities and glucose carbon flow toward nucleic acid and fatty acid synthesis in myeloid tumor cells

Chronic myeloid leukemia cells contain a constitutively active Bcr-Abl tyrosine kinase, the target protein of Gleevec (STI571) phenylaminopyrimidine class protein kinase inhibitor. Here we provide evidence for metabolic phenotypic changes in cultured K562 human myeloid blast cells after treatment with increasing doses of STI571 using [1,2-13C2]glucose as the single tracer and biological mass spectrometry. In response to 0.68 and 6.8 microm STI571, proliferation of Bcr-Abl-positive K562 cells showed a 57% and 74% decrease, respectively, whereas glucose label incorporation into RNA decreased by 13.4% and 30.1%, respectively, through direct glucose oxidation, as indicated by the decrease in the m1/Sigma(m)n ratio in RNA. Based on the in vitro proliferation data, the IC50 of STI571 in K562 cultures is 0.56 microm. The decrease in 13C label incorporation into RNA ribose was accompanied by a significant fall in hexokinase and glucose-6-phosphate 1-dehydrogenase activities. The activity of transketolase, the enzyme responsible for nonoxidative ribose synthesis in the pentose cycle, was less affected, and there was a relative increase in glucose carbon incorporation into RNA through nonoxidative synthesis as indicated by the increase in the m2/Sigma(m)n ratio in RNA. The restricted use of glucose carbons for de novo nucleic acid and fatty acid synthesis by altering metabolic enzyme activities and pathway carbon flux of the pentose cycle constitutes the underlying mechanism by which STI571 inhibits leukemia cell glucose substrate utilization and growth. The administration of specific hexokinase/glucose-6-phosphate 1-dehydrogenase inhibitor anti-metabolite substrates or competitive enzyme inhibitor compounds, alone or in combination, should be explored for the treatment of STI571-resistant advanced leukemias as well as that of Bcr-Abl-negative human malignancies.

Isofenphos induced metabolic changes in K562 myeloid blast cells

The organophosphate pesticide, isofenphos, is associated with human myeloid leukemia. In this study we describe metabolic changes in K562 myeloid blast cells from exposure to varying concentrations of isofenphos using the stable [1,2-13C(2)]glucose isotope as the single tracer and biological mass spectrometry. Isofenphos (1, 10, 100 microg/ml/72 h) treated K562 cells showed increases of 10.7, 33.8 and 39.7% in lactate production as well as a 14.2% increase (1 microg/ml/72 h) in 13C incorporation into nucleic acid ribose from glucose. Concomitantly, we observed a decrease in glucose oxidation and the synthesis of glutamate, palmitate and stearate from glucose. Our results demonstrate that this organophosphate pesticide exerts a leukemogenic effect by the recruitment of glucose carbons for nucleic acid synthesis thus promoting proliferation simultaneous with poor differentiation. The imbalanced metabolic phenotype with a severe defect in glucose oxidation, lipid and amino acid synthesis concurrent with de novo synthesis of nucleic acids in response to isofenphos treatment conforms to the invasive proliferating phenotype observed in TGF-beta treated lung epithelial carcinoma cells.

The effect of thiamine supplementation on tumour proliferation. A metabolic control analysis study

Thiamine deficiency frequently occurs in patients with advanced cancer and therefore thiamine supplementation is used as nutritional support. Thiamine (vitamin B1) is metabolized to thiamine pyrophosphate, the cofactor of transketolase, which is involved in ribose synthesis, necessary for cell replication. Thus, it is important to determine whether the benefits of thiamine supplementation outweigh the risks of tumor proliferation. Using oxythiamine (an irreversible inhibitor of transketolase) and metabolic control analysis (MCA) methods, we measured an in vivo tumour growth control coefficient of 0.9 for the thiamine-transketolase complex in mice with Ehrlich's ascites tumour. Thus, transketolase enzyme and thiamine clearly determine cell proliferation in the Ehrlich's ascites tumour model. This high control coefficient allows us to predict that in advanced tumours, which are commonly thiamine deficient, supplementation of thiamine could significantly increase tumour growth through transketolase activation. The effect of thiamine supplementation on tumour proliferation was demonstrated by in vivo experiments in mice with the ascites tumour. Thiamine supplementation in doses between 12.5 and 250 times the recommended dietary allowance (RDA) for mice were administered starting on day four of tumour inoculation. We observed a high stimulatory effect on tumour growth of 164% compared to controls at a thiamine dose of 25 times the RDA. This growth stimulatory effect was predicted on the basis of correction of the pre-existing level of thiamine deficiency (42%), as assayed by the cofactor/enzyme ratio. Interestingly, at very high overdoses of thiamine, approximately 2500 times the RDA, thiamine supplementation had the opposite effect and caused 10% inhibition of tumour growth. This effect was heightened, resulting in a 36% decrease, when thiamine supplementation was administered from the 7th day prior to tumour inoculation. Our results show that thiamine supplementation sufficient to correct existing thiamine deficiency stimulates tumour proliferation as predicted by MCA. The tumour inhibitory effect at high doses of thiamine is unexplained and merits further study.

Wheat germ extract decreases glucose uptake and RNA ribose formation but increases fatty acid synthesis in MIA pancreatic adenocarcinoma cells

The fermented wheat germ extract with standardized benzoquinone composition has potent tumor propagation inhibitory properties. The authors show that this extract induces profound metabolic changes in cultured MIA pancreatic adenocarcinoma cells when the [1,2-13C2]glucose isotope is used as the single tracer with biologic gas chromatography-mass spectrometry. MIA cells treated with 0.1, 1, and 10 mg/mL wheat germ extract showed a dose-dependent decrease in cell glucose consumption. uptake of isotope into ribosomal RNA (2.4%, 9.4%, and 28.0%), and release of 13CO2. Conversely, direct glucose oxidation and ribose recycling in the pentose cycle showed a dose-dependent increase of 1.2%, 20.7%, and 93.4%. The newly synthesized fraction of cell palmitate and the 13C enrichment of acetyl units were also significantly increased with all doses of wheat germ extract. The fermented wheat germ extract controls tumor propagation primarily by regulating glucose carbon redistribution between cell proliferation-related and cell differentiation-related macromolecules. Wheat germ extract treatment is likely associated with the phosphorylation and transcriptional regulation of metabolic enzymes that are involved in glucose carbon redistribution between cell proliferation-related structural and functional macromolecules (RNA, DNA) and the direct oxidative degradation of glucose, which have devastating consequences for the proliferation and survival of pancreatic adenocarcinoma cells in culture.

Role of thiamin (vitamin B-1) and transketolase in tumor cell proliferation

Metabolic control analysis predicts that stimulators of transketolase enzyme synthesis such as thiamin (vitamin B-1) support a high rate of nucleic acid ribose synthesis necessary for tumor cell survival, chemotherapy resistance, and proliferation. Metabolic control analysis also predicts that transketolase inhibitor drugs will have the opposite effect on tumor cells. This may have important implications in the nutrition and future treatment of patients with cancer.

Genistein inhibits nonoxidative ribose synthesis in MIA pancreatic adenocarcinoma cells: a new mechanism of controlling tumor growth

Genistein is a plant isoflavonoid bearing potent tumor growth-regulating characteristics. This effect of genistein has been attributed partially to its tyrosine kinase-regulating properties, resulting in cell-cycle arrest and limited angiogenesis. Genistein has been used in chemotherapy-resistant cases of advanced leukemia with promising results. Here we demonstrate that genistein primarily affects nucleic acid synthesis and glucose oxidation in tumor cells using the [1,2-(13)C2]glucose isotope as the single tracer and gas chromatography/mass spectrometry to follow various intracellular glucose metabolites. The ribose fraction of RNA demonstrated a rapid 4.6%, 16.4%, and 46.3% decrease in isotope uptake through the nonoxidative branch of the pentose cycle and a sharp 4.8%. 24.6%, and 48% decrease in 13CO2 release from glucose after 2, 20, and 200 micromol/L genistein treatment, respectively. Fatty acid synthesis and the 13C enrichment of acetyl units were not significantly affected by genistein treatment. De novo glycogen synthesis from media glucose was not detected in cultured MIA cells. It can be concluded from these studies that genistein controls tumor growth primarily through the regulation of glucose metabolism, specifically targeting glucose carbon incorporation into nucleic acid ribose through the nonoxidative steps of the pentose cycle, which represents a new paradigm for the antiproliferative action of a plant phytochemical.

Loss of regulation of lipogenesis in the Zucker diabetic (ZDF) rat

We present here a study on the role of leptin in the regulation of lipogenesis by examining the effect of dietary macronutrient composition on lipogenesis in the leptin receptor-defective Zucker diabetic fatty rat (ZDF) and its lean litter mate (ZL). Animals were pair fed two isocaloric diets differing in their fat-to-carbohydrate ratio providing 10 and 30% energy as fat. Lipogenesis was measured in the rats using deuterated water and isotopomer analysis. From the deuterium incorporation into plasma palmitate, stearate, and oleate, we determined de novo synthesis of palmitate and synthesis of stearate by chain elongation and of oleate by desaturation. Because the macronutrient composition and the caloric density were controlled, changes in de novo lipogenesis under these dietary conditions represent adaptation to changes in the fat-to-carbohydrate ratio of the diet. De novo lipogenesis was normally suppressed in response to the high-fat diet in the ZL rat to maintain a relatively constant amount of lipids transported. The ZDF rat had a higher rate of lipogenesis, which was not suppressed by the high-fat diet. The results suggest an important hormonal role of leptin in the feedback regulation of lipogenesis.

Population thiamine status and varying cancer rates between western, Asian and African countries

The role of food supplements in the form of vitamins has not been extensively investigated in relation to varying cancer rates between populations of different geographical regions. New data indicate that thiamine (vitamin B1), a common food supplement in Western food products, is directly involved in nucleic acid ribose synthesis of tumor cells in its biologically activated form through the non-oxidative transketolase catalyzed pentose cycle reaction. Whether thiamine plays a role in increased cancer rates in the Western World by enhancing tumor cell proliferation, while increased consumption of thiaminase rich food limiting thiamine availability protects against common malignancies in Asia and Africa has not been evaluated. In the Western World, thiamine is a popular vitamin supplement in the form of tablets and it is also added to basic food items such as milled flour, cereals, peanut butter, refreshment drinks and pastas. On the contrary, thiaminase, the natural thiamine-degrading enzyme, is abundantly present in raw and fermented fish, certain vegetables and roasted insects consumed primarily in Africa and Asia. Excess thiamine supplementation in common food products may contribute to the increased cancer rates of the Western World.

Transforming growth factor beta2 promotes glucose carbon incorporation into nucleic acid ribose through the nonoxidative pentose cycle in lung epithelial carcinoma cells

The invasive transformation of A-459 lung epithelial carcinoma cells has been linked to the autocrine regulation of malignant phenotypic changes by transforming growth factor beta (TGF-beta). Here we demonstrate, using stable 13C glucose isotopes, that the transformed phenotype is characterized by decreased CO2 production via direct glucose oxidation but increased nucleic acid ribose synthesis through the nonoxidative reactions of the pentose cycle. Increased nucleic acid synthesis through the nonoxidative pentose cycle imparts the metabolic adaptation of nontransformed cells to the invasive phenotype that potentially explains the fundamental metabolic disturbance in tumor cells: highly increased nucleic acid synthesis despite hypoxia and decreased glucose oxidation.

Oxythiamine and dehydroepiandrosterone induce a G1 phase cycle arrest in Ehrlich's tumor cells through inhibition of the pentose cycle

Transketolase (TK) reactions play a crucial role in tumor cell nucleic acid ribose synthesis utilizing glucose carbons, yet, current cancer treatments do not target this central pathway. Experimentally, a dramatic decrease in tumor cell proliferation after the administration of the TK inhibitor oxythiamine (OT) was observed in several in vitro and in vivo tumor models. Here, we demonstrate that pentose cycle (PC) inhibitors, OT and dehydroepiandrosterone (DHEA), efficiently regulate the cell cycle and tumor proliferation processes. Increasing doses of OT or DHEA were administered by daily intraperitoneal injections to Ehrlich's ascites tumor hosting mice for 4 days. The tumor cell number and their cycle phase distribution profile were determined by DNA flow histograms. Tumors showed a dose dependent increase in their G0-G1 cell populations after both OT and DHEA treatment and a simultaneous decrease in cells advancing to the S and G2-M cell cycle phases. This effect of PC inhibitors was significant, OT was more effective than DHEA, both drugs acted synergistically in combination and no signs of direct cell or host toxicity were observed. Direct inhibition of PC reactions causes a G1 cell cycle arrest similar to that of 2-deoxyglucose treatment. However, no interference with cell energy production and cell toxicity is observed. PC inhibitors, specifically ones targeting TK, introduce a new target site for the development of future cancer therapies to inhibit glucose utilizing pathways selectively for nucleic acid production.