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Review
. 2008;10(1):202.
doi: 10.1186/bcr1852. Epub 2008 Feb 20.

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

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Review

"V体育安卓版" Sugar and fat - that's where it's at: metabolic changes in tumors

Christian D Young et al. Breast Cancer Res. 2008.

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 VSports手机版. .

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Figures

Figure 1
Figure 1
Glycolysis overview. Glycolysis involves the metabolism of glucose to two molecules of pyruvate via nine other intermediates by the actions of nine enzymes (depicted in red). CoA, coenzyme A; NAD, nicotinamide adenine dinucleotide; NADH, nicotinamide adenine dinucleotide, reduced.
Figure 2
Figure 2
Regulation of glycolysis and fatty acid synthesis. The regulation of glycolysis and metabolism is far too complicated for one figure, but some of the key players described in the text are pictured. Akt promotes plasma membrane association of the glucose transporter, GLUT1, which transports glucose into the cell; it activates hexokinase (HK) association with the mitochondria; and it phosphorylates ATP citrate lyase (ACL), stimulating its activity of cleaving citrate to form oxaloacetate (OAA) and acetyl-coenzyme A (Ac-CoA), with downstream activation of fatty acid (FA) synthesis, which requires fatty acid synthase (FASN) and nicotinamide adenine dinucleotide phosphate (NADPH). Akt also inhibits fatty acid β-oxidation (β ox) via inhibition of carnitine palmitoyltransferase (CPT)1A, which imports fatty acids for mitochondrial β-oxidation. 2,4-Dienoyl-coenzyme A reductase (DecR1) is a β-oxidation enzyme, and its expression is often decreased in breast cancer. Impaired oxidative phosphorylation (Ox/Phos) leads to Akt activation. HK association with the mitochondria promotes phosphorylation of glucose to form glucose-6-phosphate, which can be metabolized via either glycolysis or the pentose phosphate pathway (PPP). Low levels of nutrients (such as high levels of AMP and low levels of ATP) cause activation of AMP-activated protein kinase (AMPK), which inhibits fatty acid synthesis and promotes fatty acid β-oxidation, and also phosphorylates/activates p53. p53 can inhibit glycolysis by inhibition of phosphoglycerate mutase (PGM) and can also arrest the cell cycle. However, p53 is commonly mutated in cancer cells, leading to a lack of cell cycle arrest and lack of PGM inhibition, as well as decreased expression of two p53 targets: TP53-induced glycolysis and apoptosis regulator (TIGAR) and synthesis of cytochrome oxidase (SCO)2. This drives glycolysis by disfavoring oxidative phosphorylation and PPP. Hypoxia and/or oncogenes can activate hypoxia inducible factor (HIF), which can drive transcription of nearly all glycolysis-related enzymes (most not depicted), including pyruvate kinase (PK) and lactate dehydrogenase (LDH). Some oncogenes can activate PK and LDH independently of hypoxia and HIF.

References (V体育官网)

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