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      Sugar and fat – that's where it's at: metabolic changes in tumors

      review-article
      1 , 1 ,
      Breast Cancer Research : BCR
      BioMed Central

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          Abstract

          Tumor cells exhibit an altered metabolism, characterized by increased glucose uptake and elevated glycolysis, which was first recognized by Otto Warburg 70 years ago. Warburg originally hypothesized that these metabolic changes reflected damage to mitochondrial oxidative phosphorylation. Although hypoxia and hypoxia inducible factor can induce transcriptional changes that stimulate glucose transport and glycolysis, it is clear that these changes can occur in cultured tumor or transformed cells cultured under normoxic conditions, and thus there must be genetic alterations independent of hypoxia that can stimulate aerobic glycolysis. In recent years it has become clear that loss of p53 and activation of Akt can induce all or part of the metabolic changes reflected in the Warburg effect. Likewise, changes in expression of lactate dehydrogenase and other glycolytic control enzymes can contribute to increased or altered glycolysis. It is also clear that changes in lipid biosynthesis occur in tumor cells to support increased membrane biosynthesis and perhaps the altered energy needs of the cells. Changes in fatty acid synthase, Spot 14, Akt, and DecR1 (2,4-dienoylcoenzyme A reductase) may underlie altered lipid metabolism in tumor cells and contribute to the ability of tumor cells to proliferate or metastasize. Although these advances provide new therapeutic targets that merit exploration, there remain critical questions to be explored at the mechanistic level; this work may yield insights into tumor cell biology and identify additional therapeutic targets.

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          Most cited references60

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          On the origin of cancer cells.

          O WARBURG (1956)
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            TIGAR, a p53-Inducible Regulator of Glycolysis and Apoptosis

            The p53 tumor-suppressor protein prevents cancer development through various mechanisms, including the induction of cell-cycle arrest, apoptosis, and the maintenance of genome stability. We have identified a p53-inducible gene named TIGAR (TP53-induced glycolysis and apoptosis regulator). TIGAR expression lowered fructose-2,6-bisphosphate levels in cells, resulting in an inhibition of glycolysis and an overall decrease in intracellular reactive oxygen species (ROS) levels. These functions of TIGAR correlated with an ability to protect cells from ROS-associated apoptosis, and consequently, knockdown of endogenous TIGAR expression sensitized cells to p53-induced death. Expression of TIGAR may therefore modulate the apoptotic response to p53, allowing survival in the face of mild or transient stress signals that may be reversed or repaired. The decrease of intracellular ROS levels in response to TIGAR may also play a role in the ability of p53 to protect from the accumulation of genomic damage.
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              AMP-activated protein kinase induces a p53-dependent metabolic checkpoint.

              Replicative cell division is an energetically demanding process that can be executed only if cells have sufficient metabolic resources to support a doubling of cell mass. Here we show that proliferating mammalian cells have a cell-cycle checkpoint that responds to glucose availability. The glucose-dependent checkpoint occurs at the G(1)/S boundary and is regulated by AMP-activated protein kinase (AMPK). This cell-cycle arrest occurs despite continued amino acid availability and active mTOR. AMPK activation induces phosphorylation of p53 on serine 15, and this phosphorylation is required to initiate AMPK-dependent cell-cycle arrest. AMPK-induced p53 activation promotes cellular survival in response to glucose deprivation, and cells that have undergone a p53-dependent metabolic arrest can rapidly reenter the cell cycle upon glucose restoration. However, persistent activation of AMPK leads to accelerated p53-dependent cellular senescence. Thus, AMPK is a cell-intrinsic regulator of the cell cycle that coordinates cellular proliferation with carbon source availability.
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                Author and article information

                Journal
                Breast Cancer Res
                Breast Cancer Research : BCR
                BioMed Central
                1465-5411
                1465-542X
                2008
                20 February 2008
                : 10
                : 1
                : 202
                Affiliations
                [1 ]Department of Pathology and Program in Cancer Biology, University of Colorado Denver, Anschutz Medical Campus, East 17th Avenue, Aurora, Colorado 80045, USA
                Article
                bcr1852
                10.1186/bcr1852
                2374962
                18304378
                96eb92c7-e5a8-4244-8027-b34af1907d6c
                Copyright © 2008 BioMed Central Ltd
                History
                Categories
                Review

                Oncology & Radiotherapy
                Oncology & Radiotherapy

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