Edelfosine-induced metabolic changes in cancer cells that precede the overproduction of reactive oxygen species and apoptosis

Background: Metabolic flux profiling based on the analysis of distribution of stable isotope tracer in metabolites is an important method widely used in cancer research to understand the regulation of cell metabolism and elaborate new therapeutic strategies. Recently, we developed software Isodyn, which extends the methodology of kinetic modeling to the analysis of isotopic isomer distribution for the evaluation of cellular metabolic flux profile under relevant conditions. This tool can be applied to reveal the metabolic effect of proapoptotic drug edelfosine in leukemia Jurkat cell line, uncovering the mechanisms of induction of apoptosis in cancer cells. Results: The study of 13C distribution of Jukat cells exposed to low edelfosine concentration, which induces apoptosis in ¿5% of cells, revealed metabolic changes previous to the development of apoptotic program. Specifically, it was found that low dose of edelfosine stimulates the TCA cycle. These metabolic perturbations were coupled with an increase of nucleic acid synthesis de novo, which indicates acceleration of biosynthetic and reparative processes. The further increase of the TCA cycle fluxes, when higher doses of drug applied, eventually enhance reactive oxygen species (ROS) production and trigger apoptotic program. Conclusion: The application of Isodyn to the analysis of mechanism of edelfosine-induced apoptosis revealed primary drug-induced metabolic changes, which are important for the subsequent initiation of apoptotic program. Initiation of such metabolic changes could be exploited in anticancer therapy

Edelfosine induced suicidal death of human erythrocytes

Background/Aims: The anti-inflammatory, anti-autoimmune, antiparasitic, and anti-viral ether phospholipid edelfosine (1-O-octadecyl-2-O-methylglycero-3-phosphocholine) stimulates apoptosis of tumor cells and is thus considered for the treatment of malignancy. Similar to apoptosis of nucleated cells, erythrocytes may enter eryptosis, the suicidal erythrocyte death characterized by cell shrinkage and phospholipid scrambling of the cell membrane with phosphatidylserine translocation to the erythrocyte surface. Triggers of eryptosis include Ca2+ entry with increase of cytosolic Ca2+ activity ([Ca2+]i) and oxidative stress. The present study explored, whether and how edelfosine induces eryptosis. Methods: Flow cytometry and photometry, respectively, were employed to estimate phosphatidylserine exposure at the cell surface from annexin-V-binding, cell volume from forward scatter, hemolysis from hemoglobin release, [Ca2+]i from Fluo3-fluorescence, and abundance of reactive oxygen species (ROS) from 2',7'-dichlorodihydrofluorescein diacetate (DCFDA) fluorescence. Results: A 6 hours exposure of human erythrocytes to edelfosine (5 \u3bcM) significantly increased the percentage of annexin-V-binding cells, significantly decreased forward scatter, and significantly increased Fluo3-fluorescence, but did not significantly modify DCFDA fluorescence. The effect of edelfosine on annexin-V-binding was significantly blunted, but not abolished by removal of extracellular Ca2+. Conclusions: Edelfosine triggers cell shrinkage and phospholipid scrambling of the erythrocyte cell membrane, an effect in part due to stimulation of Ca2+ entry

Edelfosine lipid nanosystems overcome drug resistance in leukemic cell lines

Although current therapies have improved leukemia survival rates, adverse drug effects and relapse are frequent. Encapsulation of edelfosine (ET) in lipid nanoparticles (LN) improves its oral bioavailability and decreases its toxicity. Here we evaluated the efficacy of ET-LN in myeloid leukemia cell lines. Drug-loaded LN were as effective as free ET in sensitive leukemia cell lines. Moreover, the encapsulated drug overcame the resistance of the K562 cell line to the drug. LN containing ET might be used as a promising drug delivery system in leukemia due to their capacity to overcome the in vivo pitfalls of the free drug and their efficacy in vitro in leukemia cell lines

Compartmentation of glycogen metabolism revealed from 13C isotopologue distributions

Background: Stable isotope tracers are used to assess metabolic flux profiles in living cells. The existing methods of measurement average out the isotopic isomer distribution in metabolites throughout the cell, whereas the knowledge of compartmental organization of analyzed pathways is crucial for the evaluation of true fluxes. That is why we accepted a challenge to create a software tool that allows deciphering the compartmentation of metabolites based on the analysis of average isotopic isomer distribution. Results: The software Isodyn, which simulates the dynamics of isotopic isomer distribution in central metabolic pathways, was supplemented by algorithms facilitating the transition between various analyzed metabolic schemes, and by the tools for model discrimination. It simulated 13C isotope distributions in glucose, lactate, glutamate and glycogen, measured by mass spectrometry after incubation of hepatocytes in the presence of only labeled glucose or glucose and lactate together (with label either in glucose or lactate). The simulations assumed either a single intracellular hexose phosphate pool, or also channeling of hexose phosphates resulting in a different isotopic composition of glycogen. Model discrimination test was applied to check the consistency of both models with experimental data. Metabolic flux profiles, evaluated with the accepted model that assumes channeling, revealed the range of changes in metabolic fluxes in liver cells. Conclusions: The analysis of compartmentation of metabolic networks based on the measured 13C distribution was included in Isodyn as a routine procedure. The advantage of this implementation is that, being a part of evaluation of metabolic fluxes, it does not require additional experiments to study metabolic compartmentation. The analysis of experimental data revealed that the distribution of measured 13C-labeled glucose metabolites is inconsistent with the idea of perfect mixing of hexose phosphates in cytosol. In contrast, the observed distribution indicates the presence of a separate pool of hexose phosphates that is channeled towards glycogen synthesis

The landscape of tiered regulation of breast cancer cell metabolism

Altered metabolism is a hallmark of cancer, but little is still known about its regulation. In this study, we measure transcriptomic, proteomic, phospho-proteomic and fluxomics data in a breast cancer cell-line (MCF7) across three different growth conditions. Integrating these multiomics data within a genome scale human metabolic model in combination with machine learning, we systematically chart the different layers of metabolic regulation in breast cancer cells, predicting which enzymes and pathways are regulated at which level. We distinguish between two types of reactions, directly and indirectly regulated. Directly-regulated reactions include those whose flux is regulated by transcriptomic alterations (~890) or via proteomic or phospho-proteomics alterations (~140) in the enzymes catalyzing them. We term the reactions that currently lack evidence for direct regulation as (putative) indirectly regulated (~930). Many metabolic pathways are predicted to be regulated at different levels, and those may change at different media conditions. Remarkably, we find that the flux of predicted indirectly regulated reactions is strongly coupled to the flux of the predicted directly regulated ones, uncovering a tiered hierarchical organization of breast cancer cell metabolism. Furthermore, the predicted indirectly regulated reactions are predominantly reversible. Taken together, this architecture may facilitate rapid and efficient metabolic reprogramming in response to the varying environmental conditions incurred by the tumor cells. The approach presented lays a conceptual and computational basis for mapping metabolic regulation in additional cancers

Mecanismo de acción de edelfosina en sarcoma de ewing y cáncer de cabeza y cuello

Memoria presentada por Ximena Marcela Bonilla Forero para optar al grado de Doctor por la Universidad de Salamanca, y realizada en el Instituto de Biología Molecular y Celular del Cáncer.Los tumores sólidos de sarcoma de Ewing y cáncer de cabeza y cuello son tumores altamente resistentes a la terapia convencional; además estos tumores emplean mecanismos moleculares que permiten la evasión de la respuesta apoptótica como mecanismo de supervivencia. Los lípidos antitumorales (ATLs) son compuestos ampliamente estudiados como posible herramienta terapéutica para el tratamiento de varios tipos de tumores, cuyo mecanismo de acción implica la activación de la respuesta apoptótica. En este trabajo se describe el mecanismo de acción del compuesto prototipo de este grupo de lípidos, la edelfosina, en la muerte de las células de estos tipos de tumores sólidos. En el caso del sarcoma de Ewing implica la activación de la respuesta apoptótica a través de un estrés de retículo endoplasmático, que conlleva a la activación de la ruta intrínseca mitocondrial de la apoptosis. También se describe el posible papel que cumplen los microdominios de membrana 'rafts' en la muerte de estas células, así como la actividad antitumoral in vivo de la edelfosina en un modelo de xenotransplante. Por otra parte, en las células de cáncer de cabeza y cuello, la edelfosina induce la respuesta apoptótica, implicando al retículo endoplasmático y la mitocondria. Sin embargo, en este caso se muestra la participación de mecanismos alternativos de muerte como la necrosis, y mecanismos reguladores a la apoptosis como es el caso de la autofagia. Este trabajo muestra el posible potencial que puede presentar la edelfosina en el tratamiento de estos dos tumores.Peer Reviewe

Mecanismo de acción de edelfosina en sarcoma de ewing y cáncer de cabeza y cuello

[ES] Los tumores sólidos de sarcoma de Ewing y cáncer de cabeza y cuello son tumores altamente resistentes a la terapia convencional; además estos tumores emplean mecanismos moleculares que permiten la evasión de la respuesta apoptótica como mecanismo de supervivencia. Los lípidos antitumorales (ATLs) son compuestos ampliamente estudiados como posible herramienta terapéutica para el tratamiento de varios tipos de tumores, cuyo mecanismo de acción implica la activación de la respuesta apoptótica. En este trabajo se describe el mecanismo de acción del compuesto prototipo de este grupo de lípidos, la edelfosina, en la muerte de las células de estos tipos de tumores sólidos. En el caso del sarcoma de Ewing implica la activación de la respuesta apoptótica a través de un estrés de retículo endoplasmático, que conlleva a la activación de la ruta intrínseca mitocondrial de la apoptosis. También se describe el posible papel que cumplen los microdominios de membrana ¿rafts¿ en la muerte de estas células, así como la actividad antitumoral in vivo de la edelfosina en un modelo de xenotransplante. Por otra parte, en las células de cáncer de cabeza y cuello, la edelfosina induce la respuesta apoptótica, implicando al retículo endoplasmático y la mitocondria. Sin embargo, en este caso se muestra la participación de mecanismos alternativos de muerte como la necrosis, y mecanismos reguladores a la apoptosis como es el caso de la autofagia. Este trabajo muestra el posible potencial que puede presentar la edelfosina en el tratamiento de estos dos tumores

The study of RAS-induced metabolic reprogramming and the role of the pentose phosphate pathway in tumor metabolism

[spa] La presente tesis doctoral se centra en las adaptaciones metabólicas inducidas por la activación de oncogenes así como en el potencial del entramado metabólico como diana antitumoral. A lo largo de los últimos años, ha resurgido un renovado interés en el estudio del metabolismo, particularmente en el metabolismo de las células tumorales, dando lugar a una nueva disciplina conocida como metabolismo tumoral. Numerosas investigaciones se han centrado en la asociación entre mutaciones en oncogenes o genes supresores de tumores con perfiles metabólicos característicos, en busca de dependencias metabólicas que ofrezcan nuevas posibilidades para el tratamiento de los tumores. La búsqueda de alteraciones metabólicas que constituyan vulnerabilidades de la célula tumoral representa la piedra angular de esta interesante disciplina. Así, esta tesis doctoral tiene como objetivo general elucidar las alteraciones metabólicas que acompañan a la mutación de oncogenes y explorar el potencial del entramado metabólico como diana antitumoral. Por tanto, los objetivos principales de este trabajo son los siguientes: i) análisis de la reprogramación metabólica inducida por la activación oncogénica de RAS empleando líneas celulares transfectadas de manera estable con copias mutadas de los oncogenes K-RAS y H-RAS y, ii) validación de la vía de las pentosas fosfato como potencial diana antitumoral y estudio de su papel en el metabolismo tumoral de modelos celulares de cáncer de colon y de mama. Así, en este trabajo de tesis doctoral hemos concluido que la activación oncogénica de RAS promueve una profunda reprogramación del metabolismo induciendo cambios significativos en la glucólisis, la vía de las pentosas fosfato, el metabolismo de la glutamina y la lipogénesis. Por otro lado, hemos determinado que la inhibición de la vía de las pentosas fosfato tiene distintos efectos según el tipo de tumor. La inhibición de la G6PD en la línea celular de cáncer colon HT29 no produjo efectos sobre la proliferación mientras que su inhibición en células de cáncer de mama MCF7 indujo una notable reducción de la proliferación y un incremento de la muerte celular. Por otra parte, en la inhibición en MCF7 del otro enzima clave de la vía de las pentosas fosfato, la TKT, no se observaron cambios significativos en términos de proliferación y viabilidad celular. Además, en este trabajo también se ha puesto de manifiesto una conexión funcional entre la vía de las pentosas fosfato y el metabolismo de la glutamina en ambos modelos celulares, sugiriendo un papel complementario de estas dos vías metabólicas.[eng] The present doctoral thesis is focused on the metabolic adaptations induced by oncogene activation as well as the potential role of the metabolic network as antitumor therapy. Over the last years, it has emerged a renewed interest in the field of metabolism, particularly in cancer metabolism. Great efforts have been focused on the association of mutated oncogenes or tumor suppressor genes and tumor metabolic profiles, in the search of metabolic dependencies that offer new potential avenues for cancer treatment. The pursuit of discovering tumor metabolic alterations in which cancer cells rely on has represented the cornerstone of this interesting discipline. Thus, this thesis is part of this recent and promising scientific current and is intended to shed light on the metabolic alterations accompanying oncogene mutation and on potential metabolic pathways that might be of therapeutic interest in the future. Hence, the objectives of this thesis can be divided into two specific aims: i) analysis of the metabolic reprogramming of RAS oncogenic activation using stable transfected cell lines with mutated copies of K-RAS and H-RAS and ii) validation of the pentose phosphate pathway as a potential therapeutic target and exploration of its role within tumor metabolism in colon and breast cancer cell models. Thus, according to the proposed objectives, the main conclusions obtained are as follow: 1. The study of flux distribution in combination with metabolic control analysis performed by analyzing solely the sign of fixed-sign control coefficients, is a reliable approach to identify the key enzymes involved in metabolic reprogramming. The use of this methodology has allowed us to identify an increase in glycolysis and PPP fluxes as metabolic features of KRAS-induced metabolic reprogramming and to propose G6PD, PK and LDH as the key enzymes responsible for this metabolic transition. 2. H-RAS oncogenic activation reprograms glucose and glutamine metabolism by enhancing glycolytic and PPP fluxes as well as mitochondrial metabolism. Glutamine is responsible for sustaining the activated mitochondrial metabolism in BJ-HRasV12, while glucose-derived carbons in the mitochondria are primarily used to fuel lipogenesis. Moreover, lipogenesis is overactivated in BJ-HRasV12 cells, which are more sensitive to FAS inhibition than BJ cells. 3. G6PD enzyme is overactivated in colon cancer cells with oncogenic activation of the RAS signaling pathway. Nevertheless, G6PD seems to be dispensable for proliferation and survival in BRAF-mutated HT29 cell line. Furthermore, a new connection between PPP and glutamine metabolism has been unveiled, as G6PD is overexpressed in HT29 cells under glutamine-deprived conditions by a mechanism involving a concomitantly increase in ROS levels and NRF2 induction. 4. G6PD enzyme is important in proliferation, survival and regulation of ROS levels in breast cancer MCF7 cells. However, it exerts a low regulation over ribose synthesis flux through the oxidative branch of PPP. G6PD inhibition enhances glycolytic flux, promotes lactate secretion and increases glutamine consumption, which is used to maintain energy homeostasis, although it is not essential for cell proliferation. 5. TKT enzyme is dispensable for proliferation of breast cancer MCF7 cells, but it exerts a high control over ribose synthesis flux through the nonoxidative branch of PPP. TKT impairment reduces glycolytic flux and increases the consumption of glutamine, which is intended to maintain energy homeostasis but it is not essential for cell proliferatio

Role of adipose tissue in the pathogenesis and treatment of metabolic syndrome

© Springer International Publishing Switzerland 2014. Adipocytes are highly specialized cells that play a major role in energy homeostasis in vertebrate organisms. Excess adipocyte size or number is a hallmark of obesity, which is currently a global epidemic. Obesity is not only the primary disease of fat cells, but also a major risk factor for the development of Type 2 diabetes, cardiovascular disease, hypertension, and metabolic syndrome (MetS). Today, adipocytes and adipose tissue are no longer considered passive participants in metabolic pathways. In addition to storing lipid, adipocytes are highly insulin sensitive cells that have important endocrine functions. Altering any one of these functions of fat cells can result in a metabolic disease state and dysregulation of adipose tissue can profoundly contribute to MetS. For example, adiponectin is a fat specific hormone that has cardio-protective and anti-diabetic properties. Inhibition of adiponectin expression and secretion are associated with several risk factors for MetS. For this purpose, and several other reasons documented in this chapter, we propose that adipose tissue should be considered as a viable target for a variety of treatment approaches to combat MetS