American Journal of Clinical Oncology:
Targeting Glucose Metabolism: An Emerging Concept for Anticancer Therapy
Madhok, Brijesh M. MBBS, MS, MRCS; Yeluri, Sashidhar MBBS, MS, MRCS; Perry, Sarah L. BSc(Hons); Hughes, Thomas A. BA(Hons), DPhil; Jayne, David G. MD, FRCS
Leeds Institute of Molecular Medicine, University of Leeds, Leeds, United Kingdom
The authors declare no conflicts of interest.
Reprints: Brijesh M. Madhok, MBBS, MS, MRCS, Section of Translational Anaesthesia and Surgery, Level 7 Clinical Sciences Building, St. James's University Hospital, LS9 7TF Leeds, United Kingdom. e-mail: firstname.lastname@example.org.
Mortality from locally advanced and metastatic cancer remains high despite advances in our understanding of the molecular basis of the disease and improved adjuvant therapies. Recently, there has been an increased interest in cancer metabolomics, and in particular, the potential for targeting glucose metabolism, for therapeutic gain. This interest stems from the fact that cancer cells metabolize glucose very differently from normal cells. Cancer cells preferentially switch to aerobic glycolysis rather than oxidative phosphorylation as their means of glucose metabolism. This metabolic switch is believed to enhance cancer cell survival. Several therapeutic agents that target tumor metabolism have shown significant cancer cell cytotoxicity in preclinical studies, and some have progressed to clinical trials. In this review, we discuss the alteration of carbohydrate metabolism seen in cancer cells, the underlying mechanisms, and opportunities for targeting cancer metabolism for therapeutic purposes.
CARBOHYDRATE METABOLISM IN CANCER CELLS: A WEALTH OF POTENTIAL DRUG TARGETS
Normal cells rely on glycolysis for the production of adenosine 5′-triphosphate (ATP) in hypoxic conditions, but cancer cells are highly dependent on glycolysis even under normoxia. This phenomenon of “aerobic glycolysis” was first discovered by Otto Warburg in the 1920s, and hence it is known as the “Warburg effect.”1 Warburg suggested that aerobic glycolysis was a consequence of attenuated mitochondrial function in cancer cells, and hence they switch to glycolysis for energy production. He opined that mitochondrial dysfunction was responsible for the origin of cancer. There is now mounting evidence that cancer cells undergo increased glycolysis and reduced oxidative phosphorylation.2,3 Mechanisms underlying the Warburg effect seem to be multifacto-rial,4 with factors such as the hypoxic tumor microenvironment,5 hypoxia inducible factor 1 (HIF1),6,7 mitochondrial dysfunction,8 p53 mutations,9 and oncogenes10,11 playing important roles. Intriguingly, recent research indicates that pyruvate kinase, which regulates the final rate-limiting step of glycolysis plays a key role in the Warburg phenotype. In particular, increased expression of the M2 isoform of pyruvate kinase and its phosphorylation mediated by tyrosine kinase have been shown to promote aerobic glycolysis in tumors.12,13 This shift in basic glucose metabolism results from changes in expression or activity of a wide range of metabolic enzymes and other glucose-related molecules. Changes include increased expression of glucose transporters (GLUT) facilitating increased uptake of glucose from the extracellular environment, increased expression of most of the enzymes of glycolysis leading to increased glycolytic activity, and increased expression of pyruvate dehydrogenase kinase (PDK) resulting in reduced entry of pyruvate into oxidative phosphorylation via suppression of pyruvate dehydrogenase (PDH) activity.14,15 These changes give the cancer cells a selective growth advantage and favor cancer progression by downregulating apoptotic pathways (Fig. 1), and cause acidification of the extracellular environment, which is both toxic to the noncancer cells and enhances cancer-cell invasion and metastasis.5,16
The metabolic differences between cancer cells and normal cells present 2 potential therapeutic strategies. The first is to inhibit any of the glycolytic enzymes, the assumption being that cancer cells are more dependent on their activity for production of ATP than normal cells, and as a result the treatment would preferentially target the cancer cells. The second is to promote oxidative phosphorylation, with the intention of reactivating metabolic pathways that have been downregulated in cancer cells and reactivating apoptotic mechanisms.
A further possibility is to influence specific upstream regulators that are responsible for these metabolic changes, and thereby simultaneously inhibit glycolysis and promote oxidative phosphorylation. The metabolic changes are induced directly or indirectly by deregulated expression of various oncogenes (eg, c-myc and akt) or loss of tumor suppressor activity (eg, p53).9,10,17 However, each of these also influences many other aspects of cancer cell behavior and it is unclear whether the metabolic changes are a cause or an effect of their oncogenic influence. In contrast, 1 upstream factor, HIF1, directly regulates the expression of many of these key metabolic enzymes.6 Solid tumors are known to have increased expression of the HIFl α subunit,18,19 and it is thought that this has a substantial controlling influence on their metabolism. HIF1 itself represents a drug target which potentially has a diverse impact on metabolism.
Below, we describe strategies employed to manipulate the activity of individual proteins involved with glucose metabolism, under the headings of inhibition of glucose metabolism, promotion of oxidative phosphorylation, and inhibition of HIF1.
Inhibitin of Glycolysis
Inhibiting glycolysis may deprive cancer cells of ATP and curtail tumor growth. This effect has been demonstrated in vitro, and some glycolytic inhibitors are in phase II/III clinical trials. Importantly, these drugs appear to be more effective in terms of killing tumor cells in conditions of tumor hypoxia, which is usually associated with resistance to conventional chemotherapy or irradiation. Strategies to inhibit most of the individual enzymes of glycolysis have been attempted, and are described below. The role of each enzyme in the pathway is depicted in Figure 2.
Lonidamine (LND) was one of the first antiglycolytic drugs to be tested as a cancer therapeutic. It acts as a selective inhibitor of aerobic glycolysis in cancer cells, due to its inhibitory effects on mitochondrial bound hexokinase,20 although the mechanisms behind this remain poorly understood. Preclinical studies demonstrated that LND enhanced the cytotoxic effects of traditional chemotherapeutic agents,21,22 and it is in this context that LND entered clinical trials. Initial studies showed that LND could increase response rates to doxorubicin in liver metastases from breast cancer,23 however, 2 large phase III clinical trials failed to reproduce this.24,25 Similarly, LND gave no significant benefit in terms of disease-free or overall survival from early stage breast cancer when combined with Epirubicin and Cyclophosphamide.26 LND did, however, improve response rates and overall survival when combined with mitomycin-C or vindesine for treatment of non–small-cell lung cancer.27 Early phase trials have also been carried out for advanced ovarian cancer and have demonstrated that LND is safe and well tolerated when combined with conventional chemotherapy.28,29 Use of LND has now been approved in Europe in some cancer chemotherapy protocols,30 although this is not common practice.
2-Deoxyglucose (2-DG) is a glucose analogue that competitively inhibits hexokinase activity by acting as an alternative substrate. 2-DG is phosphorylated by hexokinase to form 2-DG-P, which cannot be metabolized further. 2-DG has been shown to deplete cellular ATP and cause cell death in hypoxic tumors31 while additionally, in normoxia, cancer cells apparently undergo cell death by an alternative mechanism involving changes to N-linked glycosylation patterns.32 Following promising results from many experimental studies in which 2-DG reduced cancer cell growth,33–36 2-DG has advanced into phase I/II clinical trials. Initial data demonstrate that 2-DG is well-tolerated at doses that were effective in animal models37,38 and further early phase trials have either been recently completed (ClinicalTrials.gov identifier: NCT00096707) or are underway (NCT00633087, NCT00247403). As yet, there are very few published data on the efficacy of 2-DG in clinical cancer therapy although initial results indicate that the combination of 2-DG with docetaxel is safe, and 2-DG has some antitumor effects in both breast cancer and head and neck tumors.39
3-Bromopyruvate (3-BrPA) is a lactate analogue that, unlike 2-DG, directly inhibits hexokinase by alkylation of its sulfhydryl groups.40 3-BrPA is reported to be a more potent hexokinase inhibitor, being effective in μM concentrations, as compared with 2-DG that is only effective at mM concentrations. In addition, 3-BrPA may exhibit an extra level of cancer specificity since it is taken up by lactate transporters that are frequently overexpressed in cancer cells.41,42 Accordingly, studies have demonstrated that it leads to ATP depletion and cell death in malignant cells.4 However, these promising results must be tempered with the knowledge that 3-BrPA is a strong alkylating agent that is likely to interact with molecules other than hexokinase, hence it is certainly not a highly-specific hexokinase inhibitor.43 Despite this concern, 3-BrPA has shown very encouraging anticancer activity as a single agent in a range of animal models bearing hepatocellular and breast cancer.44–46 In addition, in animal tumor models, 3-BrPA appears to synergize with some established anticancer agents, including Geldanamycin, an inhibitor of heat shock protein 90, and cisplatin, adeoxyribonucleic acid (DNA) damaging agent.47,48 Despite this wealth of encouraging data, 3-BrPA has not progressed to clinical trials, which may reflect concerns regarding its potential adverse effects.
Other molecules known to inhibit hexokinase, such as 5-thio-glucose, Mannoheptulose, and methyl jasmonate are currently being investigated for their anticancer effects.43,49
Glucose-6-phophate isomerase (GPI) is an especially interesting component of the glycolytic cascade as, in addition to its enzymatic role, it also functions as a secreted ligand, autocrine motility factor (AMF), that can regulate proliferation and invasion.50 Expression of GPI/AMF and its receptor AMFR is often increased in cancer, and is associated with poor prognosis.51,52 Downregulation of GPI/AMF expression using small interfering ribonucleic acid (siRNA) in human fibrosarcoma cells in culture sensitized the cells to oxidative stress leading to cellular senescence and reduced proliferation.53 Importantly, these results were reproduced by treatment of the cells with the GPI or AMF inhibitor, Erythrose 4-Phosphate. Several compounds, such as D-fructose-6-phosphate, 6-phosphogluconic acid and N-bromoacetyl-aminoethyl phosphate, have been suggested as potential GPI inhibitors.43
Control of 6-phosphofructo-l-kinase (PFK-1) activity is thought to have a key regulatory influence on glycolysis and therefore PFK-1 represents an attractive drug target. PFK-1 activity is believed to be indirectly upregulated in cancer cells as a result of overexpression of 6-phosphofructo-2-kinase/fructose-2,6-biphosphotase (PFKFB). PFKFB is overexpressed in a variety of highly aggressive human carcinomas54 leading to high levels of fructose-2,6-biphosphate, which activate PFK-1 allosterically.55 The small molecule, 3PO [3-(3-pyridinyl)-l-(4-pyridinyl)-2-propen-l-one] was recently established as an inhibitor of PFKFB, leading to suppression of glycolysis and tumor growth in several cancer cells in vitro and in xenograft models of lung and breast cancer.56
Glyceraldehyde-3-phosphate dehydrogenase (GAPDH) has been implicated in various nonmetabolic functions in addition to its glycolytic role; these include DNA repair, regulation of transcription, and prevention of caspase-independent cell death. As with GPI, these extra functions are thought to contribute to cancer survival and growth making the molecule additionally attractive as a drug target.43,57 Lai et al demonstrated that iodoacetate, an inhibitor of GAPDH, reduced cell survival in several cancer cell lines.58 In addition, downregulation of GAPDH expression using ribonucleic acid interference sensitized resistant leukemic cells to imatinib and prednisolone.59,60 One concern with iodoacetate is that it is a strong alkylating agent, and hence may not be a selective inhibitor of GAPDH.49 Other compounds that have been shown to have anti-GAPDH activity are koningic acid, α-chlorohydrin, and ornidazole.4,61
Three major isozymes of enolase have been identified in mammals: α, β and γ. Downregulation of α-enolase expression employing siRNA has been shown to improve the cytotoxic effects of tamoxifen, even in tamoxifen-resistant breast cancer cells.62 Another study reported α-enolase to be a novel pancreatic ductal adenocarcinoma-associated antigen, and a-enolase specific T-cells reduced growth of pancreatic ductal adenocarcinoma cells in immunodeficient mice.63 Importantly, several compounds are currently being evaluated as potential enolase inhibitors. These include sodium fluoride, phosphonoacetohydroxamic acid, and 2-phospho-D-glyceric acid.43
Various compounds such as fluorophosphates, creatine phosphate, oxalate, L-phospholactate, and some phosphoenolpyruvate analogues with modified phosphate and carboxylate groups have been described as experimental inhibitors of pyruvate kinase (PK).43,64 The most widely tested PK inhibitor, TT-232, is a structural analogue of Somatostatin, which has been shown to reduce proliferation of various human malignancies both in vitro and in vivo.65,66 At least 2 phase II trials examining this PK inhibitor (TLN-232) are registered on the clinicaltrials.gov website: one in patients with recurring metastatic melanoma is currently suspended due to an ongoing dispute with the licensor (NCT00735332), however another phase II study in patients with refractory metastatic renal cell carcinoma has been completed (NCT00422786). Initial results indicate that TLN-232 is well tolerated without any clinically significant adverse effects, and is likely to have antitumor activity in patients with metastatic melanoma and advanced renal cell carcinoma.67
Inhibition of the Pentose Phosphate Pathway
Once glucose has been phosphorylated to glucoses-6-phosphate in the first step of glycolysis, it may undergo further metabolism through the pentose phosphate pathway. Thus, the pentose phosphate pathway is an alternative to glycolysis that generates NADPH and pentoses; NADPH plays an important role in preventing oxidative stress and pentoses are required for nucleic acids synthesis. Both NADPH and pentoses are needed in abundance by the rapidly proliferating cancer cells, and indeed tumor cells are known to upregulate their pentose phosphate pathway by increased expression of 2 key enzymes: transketolase, which controls the nonoxidative part of the pathway, and glucose-6-phosphate dehydrogenase (G6PD), which controls the oxidative part.68,69
Overexpression of one of the transketolase isoforms, Transketolase-like protein 1 (TKTL1), is associated with higher tumor grades and worse patient survival,70,71 whereas downregulation of TKTL1 by ribonucleic acid interference has been shown to inhibit tumor growth in vitro.71 Oxythiamine, a thiamine antagonist and inhibitor of transketolase, has been reported to have anticancer effects both in vitro and in vivo.72,73 Downregulation of G6PD with short hairpin ribonucleic acid has been shown to reduce cancer cell proliferation, enhance apoptosis, and render cancer cells more susceptible to oxidative stress.74 6-Aminonicotinamide (6-AN) inhibits G6PD, causes oxidative stress, and sensitizes human cancer cells to radiotherapy and Cisplatin.75,76 However 6-AN has significant neurotoxic effects, and hence is unlikely to be useful clinically.
Promotion of Oxidative Phosphorylation
The aim of promoting mitochondrial oxidative phosphorylation in cancer cells is to deviate the cells' metabolism away from dependence on glycolysis with the result of inducing apoptosis through the mitochondrial pathway. One of the ways this can be achieved is by inhibiting the enzyme lactate dehydrogenase (LDH), thus preventing conversion of pyruvate to lactate. This promotes conversion of pyruvate to acetyl CoA catalyzed by PDH, which can then enter oxidative phosphorylation. Downregulation of LDH-A by short hairpin ribonucleic acid has been shown to stimulate mitochondrial respiration, reduce proliferation of cancer cells in vitro under both normoxic and hypoxic conditions, and attenuate tumorigenicity.77 Another study recently confirmed that downregulation of LDH-A causes significant attenuation of tumor growth in a xenograft mouse model of renal cancer.78
An alternative strategy is to activate the enzyme PDH, thereby stimulating uptake of pyruvate into oxidative phosphorylation. PDH activity is regulated by a family of kinases, the PDKs, with hypophosphoryated PDH being highly active. In cancer cells, PDH is typically hyperphosphorylated and relatively inactive as a result of PDK over-expression.79 Downregulation of PDK activity with siRNA or with its pharmacological inhibitor dichloroacetate (DCA) has been shown to promote hypophosphorylation of PDH and consequently to increase mitochondrial oxidative phosphorylation, induce apoptosis, and inhibit cancer cell proliferation in vitro and in vivo.16,80,81 One study has reported that DCA inhibits proliferation in breast cancer cells, but does not to induce apoptosis,82 whereas in contrast, work in the authors' laboratory has shown that DCA reduces proliferation and induces apoptosis and growth arrest in colorectal cancer cells (Madhok et al unpublished data). Currently, there are 3 on-going phase I/II clinical trials evaluating the role of DCA in patients with recurrent and/or metastatic solid tumors, glioblastoma multiforme, and malignant gliomas (NCT00566410, NCT00703859, and NCT00540176).
Attenuation of HIF1 Activity
HTF1 is a critical upstream regulator of glucose metabolism, and its overexpression is thought to be a major event in the upregulation of glycolysis and downregulation of oxidative phosphorylation in many cancers. Therefore, many different approaches have been used in an attempt to downregulate HIF1 activity. Upregulation of HIF1 in cancer results from over activity of the phosphatidylinositol 3-kinase and mitogen-activated protein kinase pathways.83,84 These pathways have a wide range of cancer-related targets and although their inhibition may have an effect on HIF1 activity, it is likely that it would only be a contributory factor to any anticancer effects. For the purpose of this review, we have focused on therapeutic strategies that target HIF1 directly and modify glucose metabolism in the target cells, while referencing previously published reviews for a more complete description of HIF inhibitors.85–87
Topotecan was initially identified in a cell-based high-throughput screen for small molecule inhibitors of the HIF1 transcriptional activation pathway.88 Topotecan, a topoisomerase I inhibitor, inhibits HIFl α translation by a DNA damage-independent mechanism, and has been shown to have cytotoxic effects in glioblastoma xenograft mice.89,90 A recent study reported that the antitumor effects of topotecan are because of reduction in levels of HIF1 targeted genes, for example, GLUT, HK, PDK, and PFKFB, all of which are crucial in glucose metabolism, and the effects are augmented with concomitant use of bevacizumab, a humanized monoclonal antibody against VEGF.91 Topotecan is approved by FDA as second-line chemotherapy in patients with small-cell lung cancer or ovarian cancer. In addition, there are several on-going clinical trials registered on the clinical trials website to evaluate its role in various advanced cancers as a single agent, in combination therapy, or as a radiosensitizing agent.
Digoxin and other cardiac glycosides have been to found to inhibit HIFl α protein synthesis, causing reduced expression of HIFl α target genes such as HK and GLUT in cancer cells.92 Digoxin administration led to reduced tumor growth in mice bearing human tumor xenograft, indicating that digoxin, which has traditionally been used for treatment of cardiac failure for decades, might have a new role in cancer therapy. Currently, there is an ongoing phase II study evaluating the potential benefit of adding digoxin to erlotinib in patients with non-small-cell lung cancer (NCT00281021). Another inhibitor of HIFl α activity, PX-478, has been reported to have significant antitumour activity in xenograft mice bearing different types of human cancers by inhibiting expression of HIF1 target genes including GLUT.93 Currently, it is in a phase I clinical trial in patients with advanced solid tumors or lymphoma (NCT00522652).
Another compound, YC-1 that is a soluble guanylyl-cyclase stimulator, has been reported to have antitumour activity by inhibiting HIFlα stability and reducing expression of HEF1 inducible genes including glycolytic enzymes, aldolase, and enolase, in xenograft mice bearing various types of human cancers.94,95 In addition to attenuating glycolysis, inhibition of HIF has also been shown to promote mitochondrial oxidative phosphorylation in tumor cells. Treatment of xenograft mice bearing human cancer with HIF1 inhibitor, echinomycin, increased tumor oxygen consumption, which led to increased tumor hypoxia and improved response to hypoxia-specific cytotoxin tirapazamine (TPZ) (Table 1).96 However, earlier clinical trials with echinomycin failed to reveal significant cytotoxic effects in patients with various types of cancer.86
The manipulation of cellular glucose metabolism is an emerging and attractive area for the development of novel anticancer therapies. Recently many anticancer agents, which target specific molecules in the glycolytic pathway, have been developed or proposed. Some of these have progressed into clinical trials, but to date they have yet to be incorporated into routine clinical practice. Further research into their mechanisms of action and their influence on normal cells, particularly those cells that rely on glycolysis, such as neurons, erythrocytes, and skeletal muscle cells, is required. It is also possible that targeting a single pathway may not be sufficient and cancer cells may switch to alternative sources for energy production, such as fatty acid oxidation.97 Fatty Acid Synthase has been shown to be highly expressed in various cancers and its inhibition has cytotoxic effects.98 There is also evidence that cancer cells can switch metabolism depending on substrate availability.99 Hence, a combination of metabolic drugs targeting different pathways might be needed to avoid resistance to a single agent. Nevertheless, targeting tumor metabolic pathways for therapeutic exploitation is promising and may form an important component of anticancer treatment in the near future.
1. Warburg O. On the origin of cancer cells. Science. 1956;123:309–314
2. Bi X, Lin Q, Foo TW, et al. Proteomic analysis of colorectal cancer reveals alterations in metabolic pathways: mechanism of tumorigenesis. Mol Cell Proteomics. 2006;5:1119–1130
3. Wu M, Neilson A, Swift AL, et al. Multiparameter metabolic analysis reveals a close link between attenuated mitochondrial bioenergetic function and enhanced glycolysis dependency in human tumor cells. Am J Physiol Cell Physiol. 2007;292:C125–C136
4. Pelicano H, Martin DS, Xu RH, et al. Glycolysis inhibition for anticancer treatment. Oncogene. 2006;25:4633–4646
5. Gatenby RA, Gillies RJ. Why do cancers have high aerobic glycolysis? Nat Rev Cancer. 2004;4:891–899
6. Semenza GL. Hypoxia-inducible factor 1: master regulator of O2 homeostasis. Curr Opin Genet Dev. 1998;8:588–594
7. Semenza GL. HIF-1 mediates the Warburg effect in clear cell renal carcinoma. J Bioenerg Biomembr. 2007;39:231–234
8. Taylor RW, Turnbull DM. Mitochondrial DNA mutations in human disease. Nat Rev Genet. 2005;6:389–402
9. Matoba S, Kang JG, Patino WD, et al. p53 regulates mitochondrial respiration. Science. 2006;312:1650–1653
10. Elstrom RL, Bauer DE, Buzzai M, et al. Akt stimulates aerobic glycolysis in cancer cells. Cancer Res. 2004;64:3892–3899
11. Kim JW, Gardner LB, Dang CV. Oncogenic alterations of metabolism and the Warburg effect. Drug Discov Today Dis Mech. 2005;2:233–238
12. Christofk HR, Vander Heiden MG, Harris MH, et al. The M2 splice isoform of pyruvate kinase is important for cancer metabolism and tumour growth. Nature. 2008;452:230–233
13. Hitosugi T, Kang S, Vander Heiden MG, et al. Tyrosine phosphorylation inhibits PKM2 to promote the Warburg effect and tumor growth. Sci Signal. 2009;2:ra73
14. Altenberg B, Greulich KO. Genes of glycolysis are ubiquitously overexpressed in 24 cancer classes. Genomics. 2004;84:1014–1020
15. Kim JW, Tchernyshyov I, Semenza GL, et al. HIF-1-mediated expression of pyruvate dehydrogenase kinase: a metabolic switch required for cellular adaptation to hypoxia. Cell Metab. 2006;3:177–185
16. Bonnet S, Archer SL, lalunis-Turner J, et al. A mitochondria-K+ channel axis is suppressed in cancer and its normalization promotes apoptosis and inhibits cancer growth.. Cancer Cell. 2007;11:37–51
17. Kim JW, Dang CV. Cancer's molecular sweet tooth and the Warburg effect. Cancer Res. 2006;66:8927–8930
18. Zhong H, De Marzo AM, Laughner E, et al. Overexpression of hypoxia-inducible factor 1 alpha in common human cancers and their metastases. Cancer Res. 1999;59:5830–5835
19. Talks KL, Turley H, Garter KC, et al. The expression and distribution of the hypoxia-inducible factors HIF-l alpha and HIF-2α in normal human tissues, cancers, and tumor-associated macrophages. Am J Pathol. 2000;157:411–421
20. Floridi A, Paggi MG, Marcante ML, et al. Lonidamine, a selective inhibitor of aerobic glycolysis of murine tumor cells. J Natl Cancer Inst. 1981;66:497–499
21. Rosbe KW, Brann TW, Holden SA, et al. Effect of lonidamine on the cytotoxicity of four alkylating agents in vitro. Cancer Chemother Pharmacol. 1989;25:32–36
22. Floridi A, Bruno T, Miccadei S, et al. Enhancement of doxorubicin content by the antitumor drug lonidamine in resistant Ehrlich ascites tumor cells through modulation of energy metabolism. Biochem Pharmacol. 1998;56:841–849
23. Amadori D, Frassineti GL, De MA, et al. Modulating effect of lonidamine on response to doxorubicin in metastatic breast cancer patients: results from a multicenter prospective randomized trial. Breast Cancer Res Treat. 1998;49:209–217
24. Pacini P, Rinaldini M, Algeri R, et al. FEC (5-fluorouracil, epidoxorubicin and cyclophosphamide) versus EM (epidoxorubicin and mitomycin-C) with or without lonidamine as first-line treatment for advanced breast cancer. A multicentric randomised study. Final results. Eur J Cancer. 2000;36:966–975
25. Berruti A, Bitossi R, Gorzegno G, et al. Time to progression in metastatic breast cancer patients treated with epirubicin is not improved by the addition of either cisplatin or lonidamine: final results of a phase III study with a factorial design. J Clin Oncol. 2002;20:4150–4159
26. Papaldo P, Lopez M, Cortesi E, et al. Addition of either lonidamine orgranulocyte colony-stimulating factor does not improve survival in early breast cancer patients treated with high-dose epirubicin and cyclophosphamide. J Clin Oncol. 2003;21:3462–3468
27. Gatzemeier U, Cavalli F, Haussinger K, et al. Phase III trial with and without lonidamine in non-small cell lung cancer. Semin Oncol. 1991;18:42–48
28. Gadducci A, Brunetti I, Muttini MP, et al. Epidoxorubicin and lonidamine in refractory or recurrent epithelial ovarian cancer. Eur J Cancer Am. 1994;30:1432–1435
29. De LM, Lorusso V, Latorre A, et al. Paclitaxel, cisplatin and lonidamine in advanced ovarian cancer: a phase II study. Eur J Cancer. 2001;37:364–368
30. Sweetman SC Martindale: The Complete Drug Reference. 200535th ed London, United Kingdom Pharmaceutical Press
31. Maher JC, Krishan A, Lampidis TJ. Greater cell cycle inhibition and cyto-toxicity induced by 2-deoxy-D-glucose in tumor cells treated under hypoxic versus aerobic conditions. Cancer Chemother Pharmacol. 2004;53:116–122
32. Kurtoglu M, Gao N, Shang J, et al. Under normoxia, 2-deoxy-D-glucose elicits cell death in select tumor types not by inhibition of glycolysis but by interfering with N-linked glycosylation. Mol Cancer Ther. 2007;6:3049–3058
33. Maher JC, Savaraj N, Priebe W, et al. Differential sensitivity to 2-deoxy-D-glucose between two pancreatic cell lines correlates with GLUT-1 expression. Pancreas. 2005;30:e34–e39
34. Liu H, Savaraj N, Priebe W, et al. Hypoxia increases tumor cell sensitivity to glycolytic inhibitors: a strategy for solid tumor therapy (Model C). Biochem Pharmacol. 2002;64:1745–1751
35. Liu H, Hu YP, Savaraj N, et al. Hypersensitization of tumor cells to glycolytic inhibitors. Biochemistry. 2001;40:5542–5547
36. Maschek G, Savaraj N, Priebe W, et al. 2-deoxy-D-glucose increases the efficacy of adriamycin and paclitaxel in human osteosarcoma and non-small cell lung cancers in vivo. Cancer Res. 2004;64:31–34
37. Mohanti BK, Rath GK, Anantha N, et al. Improving cancer radiotherapy with 2-deoxy-D-glucose: phase I/II clinical trials on human cerebral gliomas. Int J Radiat Oncol Biol Phys. 1996;35:103–111
38. Singh D, Banerji AK, Dwarakanath BS, et al. Optimizing cancer radiotherapy with 2-deoxy-d-glucose dose escalation studies in patients with glioblastoma multiforme. Strahlenther Onkol. 2005;181:507–514
39. Threshold Pharmaceuticals. Product pipeline, 2-deoxyglucose. 2009 Redwood City, CA Threshold Pharmaceuticals
40. Mathupala SP, Ko YH, Pedersen PL. Hexokinase II: cancer's double-edged sword acting as both facilitator and gatekeeper of malignancy when bound to mitochondria. Oncogene. 2006;25:4777–4786
41. Pedersen PL. Warburg, me and Hexokinase 2: Multiple discoveries of key molecular events underlying one of cancers' most common phenotypes, the “Warburg Effect,” ie., elevated glycolysis in the presence of oxygen. J Bioenerg Biomembr. 2007;39:211–222
42. Pedersen PL. The cancer cell's “power plants” as promising therapeutic targets: an overview. J Bioenerg Biomembr. 2007;39:1–12
43. Scatena R, Bottoni P, Pontoglio A, et al. Glycolytic enzyme inhibitors in cancer treatment. Expert Opin Investig Drugs. 2008;17:1533–1545
44. Ko YH, Smith BL, Wang Y, et al. Advanced cancers: eradication in all cases using 3-bromopyruvate therapy to deplete ATP. Biochem Biophys Res Commun. 2004;324:269–275
45. Vali M, Vossen JA, Buijs M, et al. Targeting of VX2 rabbit liver tumor by selective delivery of 3-bromopyruvate: a biodistribution and survival study. J Pharmacol Exp Ther. 2008;327:32–37
46. Buijs M, Vossen JA, Geschwind JF, et al. Specificity of the anti-glycolytic activity of 3-bromopyruvate confirmed by FDG uptake in a rat model of breast cancer. Invest New Drugs. 2009;27:120–123
47. Cao X, Bloomston M, Zhang T, et al. Synergistic antipancreatic tumor effect by simultaneously targeting hypoxic cancer cells with HSP90 inhibitor and glycolysis inhibitor. Clin Cancer Res. 2008;14:1831–1839
48. Zhang X, Varin E, Briand M, et al. Novel therapy for malignant pleural mesothelioma based on anti-energetic effect: an experimental study using 3-Bromopyruvate on nude mice. Anticancer Res. 2009;29:1443–1448
49. Pathania D, Millard M, Neamati N. Opportunities in discovery and delivery of anticancer drugs targeting mitochondria and cancer cell metabolism. Adv Drug Deliv Rev. 2009;61:1250–1275
50. Sun YJ, Chou CC, Chen WS, et al. The crystal structure of a multifunctional protein: phosphoglucose isomerase/autocrine motility factor/neuroleukin. Proc Natl Acad Sci USA. 1999;96:5412–5417
51. Niinaka Y, Paku S, Haga A, et al. Expression and secretion of neuroleukin/phosphohexose isomerase/maturation factor as autocrine motility factor by tumor cells. Cancer Res. 1998;58:2667–2674
52. Hirono Y, Fushida S, Yonemura Y, et al. Expression of autocrine motility factor receptor correlates with disease progression in human gastric cancer. Br J Cancer. 1996;74:2003–2007
53. Funasaka T, Hu H, Hogan V, et al. Down-regulation of phosphoglucose isomerase/autocrine motility factor expression sensitizes human fibrosarcoma cells to oxidative stress leading to cellular senescence. J Biol Chem. 2007;282:36362–36369
54. Atsumi T, Chesney J, Metz C, et al. High expression of inducible 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase (iPFK-2; PFKFB3) in human cancers. Cancer Res. 2002;62:5881–5887
55. Yalcin A, Telang S, Clem B, et al. Regulation of glucose metabolism by 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatases in cancer. Exp Mol Pathol. 2009;86:174–179
56. Clem B, Telang S, Clem A, et al. Small-molecule inhibition of 6-phospho-fructo-2-kinase activity suppresses glycolytic flux and tumor growth. Mol Cancer Ther. 2008;7:110–120
57. Kim JW, Dang CV. Multifaceted roles of glycolytic enzymes. Trends Biochem Sci. 2005;30:142–150
58. Glycolytic enzyme inhibitors as novel anti-cancer drugs. In: The Northwest Regional Meeting; June 17–20; 2007; Boise, ID.
59. Lavallard VJ, Pradelli LA, Paul A, et al. Modulation of caspase-independent cell death leads to resensitization of imatinib mesylate-resistant cells. Cancer Res. 2009;69:3013–3020
60. Hulleman E, Kazemier KM, Holleman A, et al. Inhibition of glycolysis modulates prednisolone resistance in acute lymphoblastic leukemia cells. Blood. 2009;113:2014–2021
61. Nakazawa M, Uehara T, Nomura Y. Koningic acid (a potent glyceraldehyde-3-phosphate dehydrogenase inhibitor)-induced fragmentation and condensation of DNA in NG108-15 cells. J Neurochem. 1997;68:2493–2499
62. Tu SH, Chang CC, Chen CS, et al. Increased expression of enolase alpha in human breast cancer confers tamoxifen resistance in human breast cancer cells. Breast Cancer Res Treat. 2010;121:539–553
63. Cappello P, Tomaino B, Chiarle R, et al. An integrated humoral and cellular response is elicited in pancreatic cancer by alpha-enolase, a novel pancreatic ductal adenocarcinoma-associated antigen. Int J Cancer. 2009;125:639–648
64. Garcia-Alles LF, Erni B. Synthesis of phosphoenol pyruvate (PEP) analogues and evaluation as inhibitors of PEP-utilizing enzymes. Eur J Biochem. 2002;269:3226–3236
65. Szokoloczi O, Schwab R, Petak I, et al. TT232, a novel signal transduction inhibitory compound in the therapy of cancer and inflammatory diseases. J Recept Signal Transduct Res. 2005;25:217–235
66. Tejeda M, Gaal D, Hullan L, et al. A comparison of the tumor growth inhibitory effect of intermittent and continuous administration of the somatostatin structural derivative TT-232 in various human tumor models. Anticancer Res. 2006;26:3011–3015
67. Thallion Pharmaceuticals. Drug development TLN-232. 2009 Quebec, Canada Thallion Pharmaceuticals
68. Vizan P, carraz-Vizan G, az-Moralli S, et al. Modulation of pentose phosphate pathway during cell cycle progression in human colon adenocarcinoma cell line HT29. Int J Cancer. 2009;124:2789–2796
69. Chen H, Yue JX, Yang SH, et al. Over expression of transketolase-like gene 1 is associated with cell proliferation in uterine cervix cancer. Exp Clin Cancer Res. 2009;28:43
70. Volker HU, Hagemann C, Coy J, et al. Expression of transketolase-like 1 and activation of Akt in grade IV glioblastomas compared with grades II and III astrocytic gliomas. Am J Clin Pathol. 2008;130:50–57
71. Xu X, Zur HA, Coy JF, et al. Transketolase-like protein 1 (TKTL1) is required for rapid cell growth and full viability of human tumor cells. Int J Cancer. 2009;124:1330–1337
72. Comin-Anduix B, Boren J, Martinez S, et al. The effect of thiamine supplementation on tumour proliferation: a metabolic control analysis study. Eur J Biochem. 2001;268:4177–4182
73. Rais B, Comin B, Puigjaner J, et al. Oxythiamine and dehydroepiandrosterone induce a Gl phase cycle arrest in Ehrlich's tumor cells through inhibition of the pentose cycle. FEES Lett. 1999;456:113–118
74. Li D, Zhu Y, Tang Q, et al. A new G6PD knockdown tumor-cell line with reduced proliferation and increased susceptibility to oxidative stress. Cancer Biother Radiopharm. 2009;24:81–90
75. Varshney R, Dwarakanath B, Jain V. Radiosensitization by 6-aminonicotin-amide and 2-deoxy-D-glucose in human cancer cells. Int J Radiat Biol. 2005;81:397–408
76. Budihardjo II, Walker DL, Svingen PA, et al. 6-Aminonicotinamide sensitizes human tumor cell lines to cisplatin. Clin Cancer Res. 1998;4:117–130
77. Fantin VR, St-Pierre J, Leder P. Attenuation of LDH-A expression uncovers a link between glycolysis, mitochondrial physiology, and tumor maintenance. Cancer Cell. 2006;9:425–434
78. Xie H, Valera VA, Merino MJ, et al. LDH-A inhibition, a therapeutic strategy for treatment of hereditary leiomyomatosis and renal cell cancer. Mol Cancer Ther. 2009;8:626–635
79. Wigfield SM, Winter SC, Giatromanolaki A, et al. PDK-1 regulates lactate production in hypoxia and is associated with poor prognosis in head and neck squamous cancer. Br J Cancer. 2008;98:1975–1984
80. Wong JY, Huggins GS, Debidda M, et al. Dichloroacetate induces apoptosis in endometrial cancer cells. Gynecol Oncol. 2008;109:394–402
81. McFate T, Mohyeldin A, Lu H, et al. Pyruvate dehydrogenase complex activity controls metabolic and malignant phenotype in cancer cells. J Biol Chem. 2008;283:22700–22708
82. Sun RC, Fadia M, Dahlstrom JE, et al. Reversal of the glycolytic phenotype by dichloroacetate inhibits metastatic breast cancer cell growth in vitro and in vivo. Breast Cancer Res Treat. 2010;120:253–260
83. Jiang BH, Jiang G, Zheng JZ, et al. Phosphatidylinositol 3-kinase signaling controls levels of hypoxia-inducible factor 1. Cell Growth Differ. 2001;12:363–369
84. Berra E, Pages G, Pouyssegur J. MAP kinases and hypoxia in the control of VEGF expression. Cancer Metastasis Rev. 2000;19:139–145
85. Semenza GL. HIF-1 inhibitors for cancer therapy: from gene expression to drug discovery. Curr Pharm Des. 2009;15:3839–3843
86. Onnis B, Rapisarda A, Melillo G. Development of HIF-1 inhibitors for cancer therapy. J Cell Mol Med. 2009;13:2780–2786
87. Poon E, Harris AL, Ashcroft M. Targeting the hypoxia-inducible factor (HIF) pathway in cancer. Expert Rev Mol Med. 2009;11::e26
88. Rapisarda A, Uranchimeg B, Scudiero DA, et al. Identification of small molecule inhibitors of hypoxia-inducible factor 1 transcriptional activation pathway. Cancer Res. 2002;62:4316–4324
89. Rapisarda A, Uranchimeg B, Sordet O, et al. Topoisomerase I-mediated inhibition of hypoxia-inducible factor 1: mechanism and therapeutic implications. Cancer Res. 2004;64:1475–1482
90. Rapisarda A, Zalek J, Hollingshead M, et al. Schedule-dependent inhibition of hypoxia-inducible factor-1 alpha protein accumulation, angiogenesis, and tumor growth by topotecan in U251-HRE glioblastoma xenografts. Cancer Res. 2004;64:6845–6848
91. Rapisarda A, Hollingshead M, Uranchimeg B, et al. Increased antitumor activity of bevacizumab in combination with hypoxia inducible factor-1inhibition. Mol Cancer Ther. 2009;8:1867–1877
92. Zhang H, Qian DZ, Tan YS, et al. Digoxin and other cardiac glycosides inhibit HIF-1 alpha synthesis and block tumor growth. Proc Natl Acad Sci USA. 2008;105:19579–19586
93. Welsh S, Williams R, Kirkpatrick L, et al. Antitumor activity and pharma-codynamic properties of PX-478, an inhibitor of hypoxia-inducible factor-l alpha. Mol Cancer Ther. 2004;3:233–244
94. Yeo EJ, Chun YS, Cho YS, et al. YC-1: a potential anticancer drug targeting hypoxia-inducible factor 1. J Natl Cancer Inst. 2003;95:516–525
95. Kim HL, Yeo EJ, Chun YS, et al. A domain responsible for HIF-l alpha degradation by YC-1, a novel anticancer agent. Int J Oncol. 2006;29:255–260
96. Cairns RA, Papandreou I, Sutphin PD, et al. Metabolic targeting of hypoxia and HIF1 in solid tumors can enhance cytotoxic chemotherapy. Proc Natl Acad Sci USA. 2007;104:9445–9450
97. Liu Y. Fatty acid oxidation is a dominant bioenergetic pathway in prostate cancer. Prostate Cancer Prostatic Dis. 2006;9:230–234
98. Kuhajda FP. Fatty acid synthase and cancer: new application of an old pathway. Cancer Res. 2006;66:5977–5980
99. Buzzai M, Bauer DE, Jones RG, et al. The glucose dependence of Akt-transformed cells can be reversed by pharmacologic activation of fatty acid beta-oxidation. Oncogene. 2005;24:4165–4173
Warburg effect; glycolysis; hypoxia inducible factor; pyruvate dehydrogenase kinase
© 2011 by Lippincott Williams & Wilkins, Inc
What does "Remember me" mean?
By checking this box, you'll stay logged in until you logout. You'll get easier access to your articles, collections,
media, and all your other content, even if you close your browser or shut down your
To protect your most sensitive data and activities (like changing your password),
we'll ask you to re-enter your password when you access these services.
What if I'm on a computer that I share with others?
If you're using a public computer or you share this computer with others, we recommend
that you uncheck the "Remember me" box.
Highlight selected keywords in the article text.
Data is temporarily unavailable. Please try again soon.