Orally administered dehydroepiandrosterone-sulfate increases G6PD and transketolase activity in tumor tissue

Boros, László G.; Comin, Begoña; Puigjaner, Joaquim; Brandes, J.L.; Muscarella, Peter; Yusuf, Fouza; Williams, Renee; Lee, W.P.; Cascante, Marta; Schirmer, William J.; Melvin, W. Scott

doi:10.1016/s0016-5085(98)82306-8

Cited by 9 publications

(19 citation statements)

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“…In this context, it was previously demonstrated that the activity of human TKT could be effectively decreased both in vivo and in vitro by the addition of inactive cofactor analogues (24 -27). There is also evidence of a direct correlation between impaired TKT activity and reduced cancer growth (24).…”

Section: Reactions 1 Andmentioning

confidence: 99%

The Crystal Structure of Human Transketolase and New Insights into Its Mode of Action

Mitschke

Parthier

Schröder-Tittmann

et al. 2010

Journal of Biological Chemistry

169

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The crystal structure of human transketolase (TKT), a thiamine diphosphate (ThDP) and Ca 2؉ -dependent enzyme that catalyzes the interketol transfer between ketoses and aldoses as part of the pentose phosphate pathway, has been determined to 1.75 Å resolution. The recombinantly produced protein crystallized in space group C2 containing one monomer in the asymmetric unit. Two monomers form the homodimeric biological assembly with two identical active sites at the dimer interface. Transketolase (TKT 3 ; EC 2.2.1.1) is a ubiquitous enzyme in cellular carbon metabolism and requires thiamine diphosphate (ThDP), the biologically active derivative of vitamin B1, and Ca 2ϩ ions as cofactors for enzymatic activity (1, 2). TKT catalyzes the reversible transfer of two-carbon (1,2-dihydroxyethyl) units from ketose phosphates to the C1 position of aldose phosphates and thus provides, together with the Schiff base-forming transaldolase, a reversible link between glycolysis and the pentose phosphate pathway. This shunt permits cells a flexible adaptation to different metabolic needs as the pentose phosphate pathway supplies intermediates for other metabolic pathways; generates precursors for biosynthesis of nucleotides, aromatic amino acids, and vitamins; and further produces NADPH for sustaining the glutathione level and for reductive biosynthetic pathways of, for example, cholesterol and fatty acids.TKT acts on different ketose phosphate (donor) and aldose phosphate (acceptor) substrates of variable carbon chain length (3-7 carbons) in two major, essentially reversible reactions. REACTIONS 1 AND 2A simplified reaction scheme for the TKT-catalyzed conversion of substrates X5P and R5P into products S7P and G3P is shown in Fig. 1. The reaction cycle can be subdivided into a donor half-reaction (donor ligation and cleavage) and an acceptor half-reaction (acceptor ligation and product liberation) (3).After formation of the reactive ylide form of ThDP, the C2 carbanion of ThDP attacks the carbonyl of donor X5P in a nucleophilic manner to yield the covalent donor-ThDP adduct X5P-ThDP (step 1). Ionization of C3-OH and cleavage of the scissile C2-C3 bond of X5P-ThDP results in the formation of product G3P and of the 1,2-dihydroxylethyl-ThDP (DHEThDP) carbanion/enamine intermediate (step 2). This intermediate may then react with either G3P (reverse reaction of step 2) or R5P in competing equilibria. In the latter case, C2␣ of DHE-ThDP ligates to C1 of R5P (in the acyclic form), yielding * This work was supported by a grant from the "Fonds der Chemischen Industrie" (stipend to S. L.) and the Deutsche Forschungsgemeinschaft-funded Gö ttingen Graduate School for Neurosciences and Molecular Biosciences (to K. T.

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Section: Reactions 1 Andmentioning

confidence: 99%

The Crystal Structure of Human Transketolase and New Insights into Its Mode of Action

Mitschke

Parthier

Schröder-Tittmann

et al. 2010

Journal of Biological Chemistry

169

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“…Thiamine function during the maintenance of proliferative stem/initial cell growth may be conserved in plants and animals. The growth of animal cancer cells, actively dividing populations of malignant stem cells, is suppressed by treatment with thiamine antagonists (Boros et al, 1998;Liu et al, 2010). Thiamine is an essential cofactor for transketolase function, and the proliferation of tumor cells requires the nonoxidative, transketolase-dependent pentose phosphate pathway for ribose synthesis (Boros et al, 1998).…”

Section: Thiamine Is a Regulator Of Stem/initial Cell Activitymentioning

confidence: 99%

“…The growth of animal cancer cells, actively dividing populations of malignant stem cells, is suppressed by treatment with thiamine antagonists (Boros et al, 1998;Liu et al, 2010). Thiamine is an essential cofactor for transketolase function, and the proliferation of tumor cells requires the nonoxidative, transketolase-dependent pentose phosphate pathway for ribose synthesis (Boros et al, 1998). The use of transketolase inhibitors, such as the thiamine analog oxythiamine, leads to significant decreases in tumor proliferation (Comín-Anduix et al, 2001).…”

Section: Thiamine Is a Regulator Of Stem/initial Cell Activitymentioning

confidence: 99%

A Maize Thiamine Auxotroph Is Defective in Shoot Meristem Maintenance

et al. 2010

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Plant shoots undergo organogenesis throughout their life cycle via the perpetuation of stem cell pools called shoot apical meristems (SAMs). SAM maintenance requires the coordinated equilibrium between stem cell division and differentiation and is regulated by integrated networks of gene expression, hormonal signaling, and metabolite sensing. Here, we show that the maize (Zea mays) mutant bladekiller1-R (blk1-R) is defective in leaf blade development and meristem maintenance and exhibits a progressive reduction in SAM size that results in premature shoot abortion. Molecular markers for stem cell maintenance and organ initiation reveal that both of these meristematic functions are progressively compromised in blk1-R mutants, especially in the inflorescence and floral meristems. Positional cloning of blk1-R identified a predicted missense mutation in a highly conserved amino acid encoded by thiamine biosynthesis2 (thi2). Consistent with chromosome dosage studies suggesting that blk1-R is a null mutation, biochemical analyses confirm that the wild-type THI2 enzyme copurifies with a thiazole precursor to thiamine, whereas the mutant enzyme does not. Heterologous expression studies confirm that THI2 is targeted to chloroplasts. All blk1-R mutant phenotypes are rescued by exogenous thiamine supplementation, suggesting that blk1-R is a thiamine auxotroph. These results provide insight into the role of metabolic cofactors, such as thiamine, during the proliferation of stem and initial cell populations.

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“…Jurkat cell continuous S phase-independent nucleic acid synthesis rates were measured by the incorporation of [1,2-13 C 2 ]glucose into RNA ribose as the single tracer and biological mass spectrometry. 13 C label accumulation into RNA was determined by measuring the molar enrichment (ME) of ribose using chemical ionization methods, which is capable of determining both total activity (⌺m n ) and positional distribution of 13 C labels in nucleic acid ribose as described previously (22,23).…”

Section: Gel Electrophoresis and Immunoblotting Of Parp-to Analyze Pamentioning

confidence: 99%

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

Comı́n-Anduix

Boros

Marín

et al. 2002

Journal of Biological Chemistry

113

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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 iodideand annexin V-stained cells indicated that the growthinhibiting 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.The preventive and therapeutic potential of two natural wheat products, wheat bran and fermented wheat germ (Avemar), in experimental carcinogenesis has recently been described (1, 2). Although no chemical constituents are yet isolated and tested experimentally, it is likely that benzoquinones and wheat germ agglutinin in wheat germ and fiber and lipids and phytic acid in wheat bran play a significant role in exerting anti-carcinogenic effects. In a recent report utilizing intracellular carbon flow studies with a 13 C-labeled isotope of glucose and biological mass spectrometry (GC/MS), 1 it was demonstrated that the crude powder of fermented wheat germ dosedependently inhibits nucleic acid ribose synthesis primarily through the nonoxidative steps of the pentose cycle while increasing direct glucose carbon oxidation and acetyl-CoA utilization toward fatty acid synthesis in pancreatic adenocarcinoma cells (3). These metabolic changes indicate that fermented wheat germ exerts its anti-proliferative action through altering metabolic enzyme activities, which primarily control glucose carbon flow toward nucleic acid synthesis.In vivo, Avemar has a marked inhibitory effect on metastasis formation in tumor-bearing animals (4), an...

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Orally administered dehydroepiandrosterone-sulfate increases G6PD and transketolase activity in tumor tissue

Cited by 9 publications

References 0 publications

The Crystal Structure of Human Transketolase and New Insights into Its Mode of Action

The Crystal Structure of Human Transketolase and New Insights into Its Mode of Action

A Maize Thiamine Auxotroph Is Defective in Shoot Meristem Maintenance

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

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