Glycolysis and glucose transporter 1 as markers of response to hormonal therapy in breast cancer

SOX2 promotes vasculogenic mimicry by accelerating glycolysis via the lncRNA AC005392.2-GLUT1 axis in colorectal cancer

Vasculogenic mimicry (VM), a new model of angiogenesis, fulfills the metabolic demands of solid tumors and contributes to tumor aggressiveness. Our previous study demonstrated the effect of SOX2 in promoting VM in colorectal cancer (CRC). However, the underlying mechanisms behind this effect remain elusive. Here, we show that SOX2 overexpression enhanced glycolysis and sustained VM formation via the transcriptional activation of lncRNA AC005392.2. Suppression of either glycolysis or AC005392.2 expression curbed SOX2-driven VM formation in vivo and in vitro. Mechanistically, SOX2 combined with the promoter of AC005392.2, which decreased H3K27me3 enrichment and thus increased its transcriptional activity. Overexpression of AC005392.2 increased the stability of GLUT1 protein by enhancing its SUMOylation, leading to a decrease in the ubiquitination and degradation of GLUT1. Accumulation of GLUT1 contributed to SOX2-mediated glycolysis and VM. Additionally, clinical analyses showed that increased levels of AC005392.2, GLUT1, and EPHA2 expression were positively correlated with SOX2 and were also associated with poor prognoses in patients with CRC. Our study conclusively demonstrates that the SOX2-lncRNA AC005392.2-GLUT1 signaling axis regulates VM formation in CRC, offering a foundation for the development of new antiangiogenic drugs or new drug combination regimens.

Biodegradable nanoplatform upregulates tumor microenvironment acidity for enhanced cancer therapy via synergistic induction of apoptosis, ferroptosis, and anti-angiogenesis

Chemodynamic therapy of cancer is limited by insufficient endogenous H₂O₂ generation and acidity in the tumor microenvironment (TME). Herein, we developed a biodegradable theranostic platform (pLMOFePt-TGO) involving composite of dendritic organosilica and FePt alloy, loaded with tamoxifen (TAM) and glucose oxidase (GOx), and encapsulated by platelet-derived growth factor-B (PDGFB)-labeled liposomes, that effectively uses the synergy among chemotherapy, enhanced chemodynamic therapy (CDT), and anti-angiogenesis. The increased concentration of glutathione (GSH) present in the cancer cells induces the disintegration of pLMOFePt-TGO, releasing FePt, GOx, and TAM. The synergistic action of GOx and TAM significantly enhanced the acidity and H₂O₂ level in the TME by aerobiotic glucose consumption and hypoxic glycolysis pathways, respectively. The combined effect of GSH depletion, acidity enhancement, and H₂O₂ supplementation dramatically promotes the Fenton-catalytic behavior of FePt alloys, which, in combination with tumor starvation caused by GOx and TAM-mediated chemotherapy, significantly increases the anticancer efficacy of this treatment. In addition, T₂-shortening caused by FePt alloys released in TME significantly enhances contrast in the MRI signal of tumor, enabling a more accurate diagnosis. Results of in vitro and in vivo experiments suggest that pLMOFePt-TGO can effectively suppress tumor growth and angiogenesis, thus providing an exciting potential strategy for developing satisfactory tumor theranostics.

MORC2 and MAX contributes to the expression of glycolytic enzymes, breast cancer cell proliferation and migration

Cancer cell proliferation is a high energy demanding process, where the cancer cells acquire energy by high rates of glycolysis, and this phenomenon is known as the "Warburg effect". Microrchidia 2 (MORC2), an emerging chromatin remodeler, is over expressed in several cancers including breast cancer and found to promote cancer cell proliferation. However, the role of MORC2 in glucose metabolism in cancer cells remains unexplored. In this study, we report that MORC2 interacts indirectly with the genes involved in glucose metabolism via transcription factors MAX (MYC-associated factor X) and MYC. We also found that MORC2 co-localizes and interacts with MAX. Further, we observed a positive correlation of expression of MORC2 with glycolytic enzymes Hexokinase 1 (HK1), Lactate dehydrogenase A (LDHA) and Phosphofructokinase platelet (PFKP) type in multiple cancers. Surprisingly, the knockdown of either MORC2 or MAX not only decreased the expression of glycolytic enzymes but also inhibited breast cancer cell proliferation and migration. Together, these results demonstrate the involvement of the MORC2/MAX signaling axis in the expression of glycolytic enzymes and breast cancer cell proliferation and migration.

Modulating Glycolysis to Improve Cancer Therapy

Cancer cells undergo metabolic reprogramming and switch to a 'glycolysis-dominant' metabolic profile to promote their survival and meet their requirements for energy and macromolecules. This phenomenon, also known as the 'Warburg effect,' provides a survival advantage to the cancer cells and make the tumor environment more pro-cancerous. Additionally, the increased glycolytic dependence also promotes chemo/radio resistance. A similar switch to a glycolytic metabolic profile is also shown by the immune cells in the tumor microenvironment, inducing a competition between the cancer cells and the tumor-infiltrating cells over nutrients. Several recent studies have shown that targeting the enhanced glycolysis in cancer cells is a promising strategy to make them more susceptible to treatment with other conventional treatment modalities, including chemotherapy, radiotherapy, hormonal therapy, immunotherapy, and photodynamic therapy. Although several targeting strategies have been developed and several of them are in different stages of pre-clinical and clinical evaluation, there is still a lack of effective strategies to specifically target cancer cell glycolysis to improve treatment efficacy. Herein, we have reviewed our current understanding of the role of metabolic reprogramming in cancer cells and how targeting this phenomenon could be a potential strategy to improve the efficacy of conventional cancer therapy.

Progesterone Receptor-Mediated Regulation of Cellular Glucose and 18F-Fluorodeoxyglucose Uptake in Breast Cancer

Context

Positron emission tomography imaging with 2-deoxy-2-[¹⁸F]-fluoro-D-glucose (FDG) is used clinically for initial staging, restaging, and assessing therapy response in breast cancer. Tumor FDG uptake in steroid hormone receptor-positive breast cancer and physiologic FDG uptake in normal breast tissue can be affected by hormonal factors such as menstrual cycle phase, menopausal status, and hormone replacement therapy.

Objective

The purpose of this study was to determine the role of the progesterone receptor (PR) in regulating glucose and FDG uptake in breast cancer cells.

Methods and Results

PR-positive T47D breast cancer cells treated with PR agonists had increased FDG uptake compared with ethanol control. There was no significant change in FDG uptake in response to PR agonists in PR-negative MDA-MB-231 cells, MDA-MB-468 cells, or T47D PR knockout cells. Treatment of T47D cells with PR antagonists inhibited the effect of R5020 on FDG uptake. Using T47D cell lines that only express either the PR-A or the PR-B isoform, PR agonists increased FDG uptake in both cell types. Experiments using actinomycin D and cycloheximide demonstrated the requirement for both transcription and translation in PR regulation of FDG uptake. GLUT1 and PFKFB3 mRNA expression and the enzymatic activity of glucose-6-phosphate dehydrogenase and 6-phosphogluconate dehydrogenase were increased after progestin treatment of T47D cells.

Conclusion

Thus, progesterone and progestins increase FDG uptake in T47D breast cancer cells through the classical action of PR as a ligand-activated transcription factor. Ligand-activated PR ultimately increases expression and activity of proteins involved in glucose uptake, glycolysis, and the pentose phosphate pathway.

MicroRNAs as Regulators of Cancer Cell Energy Metabolism

To adapt to the tumor environment or to escape chemotherapy, cancer cells rapidly reprogram their metabolism. The hallmark biochemical phenotype of cancer cells is the shift in metabolic reprogramming towards aerobic glycolysis. It was thought that this metabolic shift to glycolysis alone was sufficient for cancer cells to meet their heightened energy and metabolic demands for proliferation and survival. Recent studies, however, show that cancer cells rely on glutamine, lipid, and mitochondrial metabolism for energy. Oncogenes and scavenging pathways control many of these metabolic changes, and several metabolic and tumorigenic pathways are post-transcriptionally regulated by microRNA (miRNAs). Genes that are directly or indirectly responsible for energy production in cells are either negatively or positively regulated by miRNAs. Therefore, some miRNAs play an oncogenic role by regulating the metabolic shift that occurs in cancer cells. Additionally, miRNAs can regulate mitochondrial calcium stores and energy metabolism, thus promoting cancer cell survival, cell growth, and metastasis. In the electron transport chain (ETC), miRNAs enhance the activity of apoptosis-inducing factor (AIF) and cytochrome c, and these apoptosome proteins are directed towards the ETC rather than to the apoptotic pathway. This review will highlight how miRNAs regulate the enzymes, signaling pathways, and transcription factors of cancer cell metabolism and mitochondrial calcium import/export pathways. The review will also focus on the metabolic reprogramming of cancer cells to promote survival, proliferation, growth, and metastasis with an emphasis on the therapeutic potential of miRNAs for cancer treatment.

Pathophysiological Integration of Metabolic Reprogramming in Breast Cancer

Simple Summary

Tumors exhibit metabolic changes that differentiate them from the normal tissues from which they derive. These metabolic changes favor tumor growth, are primarily induced by cancer cells, and produce metabolic and functional changes in the surrounding stromal cells. There is a close functional connection between the metabolic changes in tumor cells and those that appear in the surrounding stroma. A better understanding of intratumoral metabolic interactions may help identify new vulnerabilities that will facilitate new, more individualized treatment strategies against cancer. We review the metabolic changes described in tumor and stromal cells and their functional changes and then consider, in depth, the metabolic interactions between the cells of the two compartments. Although these changes are generic, we illustrate them mainly with reference to examples in breast cancer.

Abstract

Metabolic changes that facilitate tumor growth are one of the hallmarks of cancer. The triggers of these metabolic changes are located in the tumor parenchymal cells, where oncogenic mutations induce an imperative need to proliferate and cause tumor initiation and progression. Cancer cells undergo significant metabolic reorganization during disease progression that is tailored to their energy demands and fluctuating environmental conditions. Oxidative stress plays an essential role as a trigger under such conditions. These metabolic changes are the consequence of the interaction between tumor cells and stromal myofibroblasts. The metabolic changes in tumor cells include protein anabolism and the synthesis of cell membranes and nucleic acids, which all facilitate cell proliferation. They are linked to catabolism and autophagy in stromal myofibroblasts, causing the release of nutrients for the cells of the tumor parenchyma. Metabolic changes lead to an interstitium deficient in nutrients, such as glucose and amino acids, and acidification by lactic acid. Together with hypoxia, they produce functional changes in other cells of the tumor stroma, such as many immune subpopulations and endothelial cells, which lead to tumor growth. Thus, immune cells favor tissue growth through changes in immunosuppression. This review considers some of the metabolic changes described in breast cancer.

Estrogen Regulates Glucose Metabolism in Cattle Neutrophils Through Autophagy

Hypoglycemia resulting from a negative energy balance (NEB) in periparturient cattle is the major reason for a reduced glycogen content in polymorphonuclear neutrophils (PMNs). The lack of glycogen induces PMNs dysfunction and is responsible for the high incidence of perinatal diseases. The perinatal period is accompanied by dramatic changes in sex hormones levels of which estrogen (17β-estradiol, E2) has been shown to be closely associated with PMNs function. However, the precise regulatory mechanism of E2 on glucose metabolism in cattle PMNs has not been elucidated. Cattle PMNs were cultured in RPMI 1640 with 2.5 (LG), 5.5 (NG) and 25 (HG) mM glucose and E2 at 20 (EL), 200 (EM) and 450 (EH) pg/mL. We found that E2 maintained PMNs viability in different glucose conditions, and promoted glycogen synthesis by inhibiting PFK1, G6PDH and GSK-3β activity in LG while enhancing PFK1 and G6PDH activity and inhibiting GSK-3β activity in HG. E2 increased the ATP content in LG but decreased it in HG. This indicated that the E2-induced increase/decrease of ATP content may be independent of glycolysis and the pentose phosphate pathway (PPP). Further analysis showed that E2 promoted the activity of hexokinase (HK) and GLUT1, GLUT4 and SGLT1 expression in LG, while inhibiting GLUT1, GLUT4 and SGLT1 expression in HG. Finally, we found that E2 increased LC3, ATG5 and Beclin1 expression, inhibited p62 expression, promoting AMPK-dependent autophagy in LG, but with the opposite effect in HG. Moreover, E2 increased the Bcl-2/Bax ratio and decreased the apoptosis rate of PMNs in LG but had the opposite effect in HG. These results showed that E2 could promote AMPK-dependent autophagy and inhibit apoptosis in response to glucose-deficient environments. This study elucidated the detailed mechanism by which E2 promotes glycogen storage through enhancing glucose uptake and retarding glycolysis and the PPP in LG. Autophagy is essential for providing ATP to maintain the survival and immune potential of PMNs. These results provided significant evidence for further understanding the effects of E2 on PMNs immune potential during the hypoglycemia accompanying perinatal NEB in cattle.

Nuclear Receptor-Mediated Metabolic Reprogramming and the Impact on HR+ Breast Cancer

Simple Summary

Breast cancer is the most commonly diagnosed and second leading cause of cancer-related deaths in women in the United States, with hormone receptor positive (HR+) tumors representing more than two-thirds of new cases. Recent evidence has indicated that dysregulation of multiple metabolic programs, which can be driven through nuclear receptor activity, is essential for tumor genesis, progression, therapeutic resistance and metastasis. This study will review the current advances in our understanding of the impact and implication of altered metabolic processes driven by nuclear receptors, including hormone-dependent signaling, on HR+ breast cancer.

Abstract

Metabolic reprogramming enables cancer cells to adapt to the changing microenvironment in order to maintain metabolic energy and to provide the necessary biological macromolecules required for cell growth and tumor progression. While changes in tumor metabolism have been long recognized as a hallmark of cancer, recent advances have begun to delineate the mechanisms that modulate metabolic pathways and the consequence of altered signaling on tumorigenesis. This is particularly evident in hormone receptor positive (HR+) breast cancers which account for approximately 70% of breast cancer cases. Emerging evidence indicates that HR+ breast tumors are dependent on multiple metabolic processes for tumor progression, metastasis, and therapeutic resistance and that changes in metabolic programs are driven, in part, by a number of key nuclear receptors including hormone-dependent signaling. In this review, we discuss the mechanisms and impact of hormone receptor mediated metabolic reprogramming on HR+ breast cancer genesis and progression as well as the therapeutic implications of these metabolic processes in this disease.

Treatment resistance analysis reveals GLUT-1-mediated glucose uptake as a major target of synthetic rocaglates in cancer cells

Rocaglates are natural compounds that have been extensively studied for their ability to inhibit translation initiation. Rocaglates represent promising drug candidates for tumor treatment due to their growth‐inhibitory effects on neoplastic cells. In contrast to natural rocaglates, synthetic analogues of rocaglates have been less comprehensively characterized, but were also shown to have similar effects on the process of protein translation. Here, we demonstrate an enhanced growth‐inhibitory effect of synthetic rocaglates when combined with glucose anti‐metabolite 2‐deoxy‐D‐glucose (2DG) in different cancer cell lines. Moreover, we unravel a new aspect in the mechanism of action of synthetic rocaglates involving reduction of glucose uptake mediated by downregulation or abrogation of glucose transporter GLUT‐1 expression. Importantly, cells with genetically induced resistance to synthetic rocaglates showed substantially less pronounced treatment effect on glucose metabolism and did not demonstrate GLUT‐1 downregulation, pointing at the crucial role of this mechanism for the anti‐tumor activity of the synthetic rocaglates. Transcriptome profiling revealed glycolysis as one of the major pathways differentially regulated in sensitive and resistant cells. Analysis of synthetic rocaglate efficacy in a 3D tissue context with a co‐culture of tumor and normal cells demonstrated a selective effect on tumor cells and substantiated the mechanistic observations obtained in cancer cell lines. Increased glucose uptake and metabolism is a universal feature across different tumor types. Therefore, targeting this feature by synthetic rocaglates could represent a promising direction for exploitation of rocaglates in novel anti‐tumor therapies.

The Metabolic Mechanisms of Breast Cancer Metastasis

Breast cancer is one of the most common malignancy among women worldwide. Metastasis is mainly responsible for treatment failure and is the cause of most breast cancer deaths. The role of metabolism in the progression and metastasis of breast cancer is gradually being emphasized. However, the regulatory mechanisms that conduce to cancer metastasis by metabolic reprogramming in breast cancer have not been expounded. Breast cancer cells exhibit different metabolic phenotypes depending on their molecular subtypes and metastatic sites. Both intrinsic factors, such as MYC amplification, PIK3CA, and TP53 mutations, and extrinsic factors, such as hypoxia, oxidative stress, and acidosis, contribute to different metabolic reprogramming phenotypes in metastatic breast cancers. Understanding the metabolic mechanisms underlying breast cancer metastasis will provide important clues to develop novel therapeutic approaches for treatment of metastatic breast cancer.

Targeting Glucose Metabolism to Overcome Resistance to Anticancer Chemotherapy in Breast Cancer

Breast cancer (BC) is the most prevalent cancer in women. BC is heterogeneous, with distinct phenotypical and morphological characteristics. These are based on their gene expression profiles, which divide BC into different subtypes, among which the triple-negative breast cancer (TNBC) subtype is the most aggressive one. The growing interest in tumor metabolism emphasizes the role of altered glucose metabolism in driving cancer progression, response to cancer treatment, and its distinct role in therapy resistance. Alterations in glucose metabolism are characterized by increased uptake of glucose, hyperactivated glycolysis, decreased oxidative phosphorylation (OXPHOS) component, and the accumulation of lactate. These deviations are attributed to the upregulation of key glycolytic enzymes and transporters of the glucose metabolic pathway. Key glycolytic enzymes such as hexokinase, lactate dehydrogenase, and enolase are upregulated, thereby conferring resistance towards drugs such as cisplatin, paclitaxel, tamoxifen, and doxorubicin. Besides, drug efflux and detoxification are two energy-dependent mechanisms contributing to resistance. The emergence of resistance to chemotherapy can occur at an early or later stage of the treatment, thus limiting the success and outcome of the therapy. Therefore, understanding the aberrant glucose metabolism in tumors and its link in conferring therapy resistance is essential. Using combinatory treatment with metabolic inhibitors, for example, 2-deoxy-D-glucose (2-DG) and metformin, showed promising results in countering therapy resistance. Newer drug designs such as drugs conjugated to sugars or peptides that utilize the enhanced expression of tumor cell glucose transporters offer selective and efficient drug delivery to cancer cells with less toxicity to healthy cells. Last but not least, naturally occurring compounds of plants defined as phytochemicals manifest a promising approach for the eradication of cancer cells via suppression of essential enzymes or other compartments associated with glycolysis. Their benefits for human health open new opportunities in therapeutic intervention, either alone or in combination with chemotherapeutic drugs. Importantly, phytochemicals as efficacious instruments of anticancer therapy can suppress events leading to chemoresistance of cancer cells. Here, we review the current knowledge of altered glucose metabolism in contributing to resistance to classical anticancer drugs in BC treatment and various ways to target the aberrant metabolism that will serve as a promising strategy for chemosensitizing tumors and overcoming resistance in BC.

Targeted Prodrug-Based Self-Assembled Nanoparticles for Cancer Therapy

Background

Targeted prodrug has various applications as drug formulation for tumor therapy. Therefore, amphoteric small-molecule prodrug combined with nanoscale characteristics for the self-assembly of the nano-drug delivery system (DDS) is a highly interesting research topic.

Methods and Results

In this study, we developed a prodrug self-assembled nanoplatform, 2-glucosamine-fluorescein-5(6)-isothiocyanate-glutamic acid-paclitaxel (2DA-FITC-PTX NPs) by integration of targeted small molecule and nano-DDS with regular structure and perfect targeting ability. 2-glucosamine (DA) and paclitaxel were conjugated as the targeted ligand and anti-tumor chemotherapy drug by amino acid group. 2-DA molecular structure can enhance the targeting ability of prodrug-based 2DA-FITC-PTX NPs and prolong retention time, thereby reducing the toxicity of normal cell/tissue. The fluorescent dye FITC or near-infrared fluorescent dye ICG in prodrug-based DDS was attractive for in vivo optical imaging to study the behavior of 2DA-FITC-PTX NPs. In vitro and in vivo results proved that 2DA-FITC-PTX NPs exhibited excellent targeting ability, anticancer activity, and weak side effects.

Conclusion

This work demonstrates a new combination of nanomaterials for chemotherapy and may promote prodrug-based DDS clinical applications in the future.

Targeting Glucose Transporters for Breast Cancer Therapy: The Effect of Natural and Synthetic Compounds

Reprogramming of cellular energy metabolism is widely accepted to be a cancer hallmark. The deviant energetic metabolism of cancer cells-known as the Warburg effect-consists in much higher rates of glucose uptake and glycolytic oxidation coupled with the production of lactic acid, even in the presence of oxygen. Consequently, cancer cells have higher glucose needs and thus display a higher sensitivity to glucose deprivation-induced death than normal cells. So, inhibitors of glucose uptake are potential therapeutic targets in cancer. Breast cancer is the most commonly diagnosed cancer and a leading cause of cancer death in women worldwide. Overexpression of facilitative glucose transporters (GLUT), mainly GLUT1, in breast cancer cells is firmly established, and the consequences of GLUT inhibition and/or knockout are under investigation. Herein we review the compounds, both of natural and synthetic origin, found to interfere with uptake of glucose by breast cancer cells, and the consequences of interference with that mechanism on breast cancer cell biology. We will also present data where the interaction with GLUT is exploited in order to increase the efficiency or selectivity of anticancer agents, in breast cancer cells.

Simvastatin Evokes An Unpredicted Antagonism For Tamoxifen In MCF-7 Breast Cancer Cells

Purpose

Tamoxifen (TAM) is a non-steroidal antiestrogen drug, used in the prevention and treatment of all stages of hormone-responsive breast cancer. Simvastatin (SIM) is a lipid-lowering agent and has been shown to inhibit cancer cell growth. The study aimed to investigate the effect of the combination of TAM and SIM in the treatment of estrogen receptor positive (ER+) breast cancer cell line, MCF-7, and in mice-bearing Ehrlich solid tumors.

Methods

MCF-7 cells were treated with different concentrations of TAM or/and SIM for 72 hours and the effects of the combination treatment on cytotoxicity, oxidative stress markers, apoptosis, angiogenesis, and metastasis were investigated using different techniques. In addition, tumor volume, oxidative markers, and inflammatory markers of the combined therapy were explored in mice bearing solid EAC tumors.

Results

The results showed that treatment of MCF-7 cells with the combination of 10 µM TAM, and 2 µM SIM significantly inhibited the increase in oxidative stress markers, LDH, and NF-kB induced by TAM. In addition, there was a significant decrease in the total apoptotic ratio, caspase-3 activity, and glucose uptake, while there was a non-significant change in Bax/bcl-2 ratio compared to the TAM-treated group. Using the isobologram equation, the drug interaction was antagonistic with combination index, CI=1.18. On the other hand, the combination regimen decreased VEGF, and matrix metalloproteinases, MMP 2&9 compared to TAM-treated cells. Additionally, in vivo, the combination regimen resulted in a non-significant decrease in the tumor volume, decreased oxidative markers, and the protein expression of TNF-α, and NF-κB compared to the TAM treated group.

Conclusion

Although the combination regimen of TAM and SIM showed an antagonistic drug interaction in MCF-7 breast cancer, it displayed favorable antiangiogenic, anti-metastatic, and anti-inflammatory effects.

Analysis of miRNA-mRNA network reveals miR-140-5p as a suppressor of breast cancer glycolysis via targeting GLUT1

Aim: Aerobic glycolysis is characteristic of breast cancer. Comprehensive expression profiles of key proteins, their prognosis and detailed relationships between miRNAs and mRNAs remain unclear. Materials & methods: Oncomine database, Kaplan-Meier overall survival and miRNA-mRNA network analysis were performed. A key miRNA was identified and explored in vitro and in vivo. Results & conclusion: Eleven key glycolytic proteins were found with higher expression and poor prognosis: GLUT1, SLC2A5, HK1, PFKP, ALDOA, TPI1, GAPDH, PGK1, ENO1, GOT1 and GOT2. Seven miRNAs were predicted targeting 11 key glycolytic proteins: miR-140-5p, miR-3064-5p, miR-152-3p, miR-449b-5p, miR-449a, miR-194-5p and miR-34a-5p. Among them, miR-140-5p was found to be downregulated in breast cancer and directly targeted GLUT1, resulting in an antiglycolytic and antiproliferative effect.

Manipulation of Glucose and Hydroperoxide Metabolism to Improve Radiation Response

Dysregulated glucose and redox metabolism are near universal features of cancers. They therefore represent potential selectively toxic metabolic targets. This review outlines the preclinical and clinical data for targeting glucose and hydroperoxide metabolism in cancer, with a focus on drug strategies that have the most available evidence. In particular, inhibition of glycolysis using 2-deoxyglucose, and inhibition of redox metabolism using the glutathione pathway inhibitor buthionine sulfoximine and the thioredoxin pathway inhibitor auranofin, have shown promise in preclinical studies to increase sensitivity to chemotherapy and radiation by increasing intracellular oxidative stress. Combined inhibition of glycolysis, glutathione, and thioredoxin pathways sensitizes highly glycolytic, radioresistant cancer models in vitro and in vivo. Although the preclinical data support this approach, clinical data are limited to exploratory trials using a single drug in combination with either chemotherapy or radiation. Open research questions include optimizing drug strategies for targeting glycolysis and redox metabolism, determining the appropriate timing for administering this therapy with concurrent chemotherapy and radiation, and identifying biomarkers to determine the cancers that would benefit most from this approach. Given the quality of preclinical evidence, dual targeting of glycolysis and redox metabolism in combination with chemotherapy and radiation should be further evaluated in clinical trials.

Metabolic Reprogramming in Breast Cancer and Its Therapeutic Implications

Current standard-of-care (SOC) therapy for breast cancer includes targeted therapies such as endocrine therapy for estrogen receptor-alpha (ERα) positive; anti-HER2 monoclonal antibodies for human epidermal growth factor receptor-2 (HER2)-enriched; and general chemotherapy for triple negative breast cancer (TNBC) subtypes. These therapies frequently fail due to acquired or inherent resistance. Altered metabolism has been recognized as one of the major mechanisms underlying therapeutic resistance. There are several cues that dictate metabolic reprogramming that also account for the tumors’ metabolic plasticity. For metabolic therapy to be efficacious there is a need to understand the metabolic underpinnings of the different subtypes of breast cancer as well as the role the SOC treatments play in targeting the metabolic phenotype. Understanding the mechanism will allow us to identify potential therapeutic vulnerabilities. There are some very interesting questions being tackled by researchers today as they pertain to altered metabolism in breast cancer. What are the metabolic differences between the different subtypes of breast cancer? Do cancer cells have a metabolic pathway preference based on the site and stage of metastasis? How do the cell-intrinsic and -extrinsic cues dictate the metabolic phenotype? How do the nucleus and mitochondria coordinately regulate metabolism? How does sensitivity or resistance to SOC affect metabolic reprogramming and vice-versa? This review addresses these issues along with the latest updates in the field of breast cancer metabolism.

Activation of pro-survival metabolic networks by 1,25(OH)2D3 does not hamper the sensitivity of breast cancer cells to chemotherapeutics

BACKGROUND

We have previously identified 1,25-dihydroxyvitamin D3 [1,25(OH)2D3], the bioactive form of vitamin D3, as a potent regulator of energy-utilization and nutrient-sensing pathways in prostate cancer cells. In the current study, we investigated the effects of 1,25(OH)2D3 on breast cancer (BCa) cell metabolism using cell lines representing distinct molecular subtypes, luminal (MCF-7 and T-47D), and triple-negative BCa (MDA-MB-231, MDA-MB-468, and HCC-1143).

METHODS

1,25(OH)2D3's effect on BCa cell metabolism was evaluated by employing a combination of real-time measurements of glycolysis/oxygen consumption rates using a biosensor chip system, GC/MS-based metabolomics, gene expression analysis, and assessment of overall energy levels. The influence of treatment on energy-related signaling molecules was investigated by immunoblotting.

RESULTS

We show that 1,25(OH)2D3 significantly induces the expression and activity of the pentose phosphate pathway enzyme glucose-6-phosphate dehydrogenase (G6PD) in all BCa cell lines, however differentially influences glycolytic and respiratory rates in the same cells. Although 1,25(OH)2D3 treatment was found to induce seemingly anti-oxidant responses in MCF-7 cells, such as increased intracellular serine levels, and reduce the expression of its putative target gene thioredoxin-interacting protein (TXNIP), intracellular reactive oxygen species levels were found to be elevated. Serine accumulation in 1,25(OH)2D3-treated cells was not found to hamper the efficacy of chemotherapeutics, including 5-fluorouracil. Detailed analyses of the nature of TXNIP's regulation by 1,25(OH)2D3 included genetic and pharmacological inhibition of signaling molecules and metabolic enzymes including AMP-activated protein kinase and G6PD, as well as by studying the ITCH (E3 ubiquitin ligase)-TXNIP interaction. While these investigations demonstrated minimal involvement of such pathways in the observed non-canonical regulation of TXNIP, inhibition of estrogen receptor (ER) signaling by tamoxifen mirrored the reduction of TXNIP levels by 1,25(OH)2D3, demonstrating that the latter's negative regulation of ER expression is a potential mechanism of TXNIP modulation.

CONCLUSIONS

Altogether, we propose that regulation of energy metabolism contributes to 1,25(OH)2D3's anti-cancer effects and that combining 1,25(OH)2D3 with drugs targeting metabolic networks in tumor cells may lead to synergistic effects.

Roles of microRNA in prostate cancer cell metabolism

MicroRNAs are non-coding RNA which functions as regulators of genes expression. MicroRNAs have shown their biological functions in cell proliferation, cell cycle, cell metabolism, apoptosis, invasion and metastasis. Cancer cells have the ability to grow in the absence of growth factors by increased metabolic activity. MicroRNAs regulate cell metabolic processes by targeting the key enzymes or transporters and change the metabolic activities by interfering with oncogenes/tumor suppressors, hypoxia, signalling pathways and cell adhesion. This review mainly explains the roles of microRNAs in prostate cancer cell metabolism, such as glucose uptake, glycolysis and lactate secretion, lipid metabolism and interaction with signalling pathways. The relation of microRNAs with hypoxia and cell adhesion in cell metabolism is also highlighted. Therefore, miRNAs help in regulating the metabolism of survived tumor cells, understanding such miRNA-mediated interaction could lead to new avenues in therapeutic application to treat PCa.

Impact of physiological hormonal fluctuations on 18F-fluorodeoxyglucose uptake in breast cancer

PURPOSE

Premenopausal physiologic steroid levels change cyclically, in contrast to steady state low levels seen in postmenopausal patients. The purpose of this study was to evaluate whether ¹⁸F-fluorodeoxyglucose (¹⁸F-FDG) uptake in breast cancer is influenced by physiological hormonal fluctuations.

METHODS

A total of 160 primary invasive breast cancers from 155 females (54 premenopausal, 101 postmenopausal) who underwent ¹⁸F-FDG positron emission tomography/computed tomography before therapy were retrospectively analyzed. The maximal standardized uptake values (SUVmax) of tumors were compared with menstrual phases and menopausal status according to the following subgroups: 'luminal A-like,' 'luminal B-like,' and 'non-luminal.' Additionally, the effect of estradiol (E2) on ¹⁸F-FDG uptake in breast cancer cells was evaluated in vitro.

RESULTS

Among premenopausal patients, SUVmax during the periovulatory-luteal phase was significantly higher than that during the follicular phase in luminal A-like tumors (n = 25, p = 0.004), while it did not differ between the follicular phase and the periovulatory-luteal phase in luminal B-like (n = 24) and non-luminal tumors (n = 7). Multiple regression analysis showed menstrual phase, tumor size, and Ki-67 index are independent predictors for SUVmax in premenopausal luminal A-like tumors. There were no significant differences in SUVmax between pre- and postmenopausal patients in any of the subgroups. In in vitro studies, uptake in estrogen receptor-positive cells was significantly augmented when E2 concentration was increased from 0.01 to ≥ 1 nM.

CONCLUSIONS

Our data suggest that ¹⁸F-FDG uptake may be impacted by physiological hormonal fluctuations during menstrual cycle in luminal A-like cancers, and that E2 could be partly responsible for these events.

Lack of effect of the procarcinogenic 17β-estradiol on nutrient uptake by the MCF-7 breast cancer cell line

Breast cancer is one of the most frequent cancers in the population, especially in older women. Estrogen is known to be a key hormone in the development and progression of mammary carcinogenesis. In this study, we investigated if the procarcinogenic effect of 17β-estradiol (E2) in breast cancer MCF-7 cells is dependent on changes in glucose or folic acid cellular uptake. The effect of E2 on uptake of ³H-deoxy-d-glucose, ³H-folic acid, cell proliferation (3-thymidine incorporation assay), culture growth (sulforhodamine B assay), viability (lactate dehydrogenase activity assay), lactate production and migration capacity (injury assay) was evaluated. E2 (48h; 100nM) increased culture growth (16%), proliferation rate (24%), cellular viability (36%) and lactate production (38%). In contrast, E2 did not significantly affect the migration capacity of MCF-7 cells. The pro-proliferative, but not the cytoprotective effect of E2 was found to be ERβ-dependent. The polyphenols rutin and caffeic acid were not able to counteract the effect of E2 upon cell proliferation and viability. Uptake of ³H-deoxy-d-glucose was not affected by E2, either in the absence or presence of GLUT inhibitors (cytochalasin B plus phloridzin). Moreover, E2 did not change GLUT1 mRNA levels. Finally, ³H-folic acid uptake was also not affected by E2, both in the absence and presence of the RFC1 inhibitor, methotrexate. The pro-proliferative and cytoprotective effects of E2 are not dependent neither of stimulation of glucose cellular uptake (both GLUT and non-GLUT-mediated) nor of stimulation of folic acid uptake (both RFC1-and non-RFC1-mediated).

Prognostic Significance of the Metabolic Marker Hexokinase-2 in Various Solid Tumors: A Meta-Analysis

Objective

Recently, numerous studies have reported that hexokinase-2 (HK2) is aberrantly expressed in cancer, indicating that HK2 plays a pivotal role in the development and progression of cancer. However, its prognostic significance in solid tumor remains unclear. Accordingly, we performed a meta-analysis to assess the prognostic value of HK2 in solid tumor.

Methods

Eligible studies were identified using PubMed, Embase, and Web of Science databases. Pooled hazard ratios (HRs) with 95% confidence intervals (CIs) for overall survival (OS) or progression-free survival (PFS)/disease-free survival (DFS)/relapse-free survival (RFS) were estimated with random effects or fixed effects models, respectively. Subgroup analysis was also performed according to patients’ ethnicities, tumor types, detection methods, and analysis types.

Results

Data from 21 included studies with 2532 patients were summarized. HK2 overexpression was significantly associated with worse OS (pooled HR = 1.90, 95% CI = 1.51–2.38, p < 0.001) and PFS (pooled HR = 2.91, 95% CI = 2.02–4.22, p < 0.001) in solid tumor. As to a specific form of cancer, the negative effect of HK2 on OS was observed in hepatocellular carcinoma (pooled HR = 2.06, 95% CI = 1.67–2.54, p < 0.001), gastric cancer (pooled HR = 1.72, 95% CI = 1.09–2.71, p = 0.020), colorectal cancer (pooled HR = 2.89, 95% CI = 1.62–5.16, p < 0.001), but not in pancreatic cancer (pooled HR = 1.13, 95% CI = 0.28–4.66, p = 0.864). No publication bias was found in the included studies for OS (Begg’s test, p = 0.325; Egger’s test, p = 0.441).

Conclusion

In this meta-analysis, we identified that elevated HK2 expression was significantly associated with shorter OS and PFS in patients with solid tumor, but the association varies according to cancer type.

Inhibition of Aerobic Glycolysis Represses Akt/mTOR/HIF-1α Axis and Restores Tamoxifen Sensitivity in Antiestrogen-Resistant Breast Cancer Cells

Tamoxifen resistance is often observed in the majority of estrogen receptor–positive breast cancers and it remains as a serious clinical problem in breast cancer management. Increased aerobic glycolysis has been proposed as one of the mechanisms for acquired resistance to chemotherapeutic agents in breast cancer cells such as adriamycin. Herein, we report that the glycolysis rates in LCC2 and LCC9—tamoxifen-resistant human breast cancer cell lines derived from MCF7— are higher than those in MCF7S, which is the parent MCF7 subline. Inhibition of key glycolytic enzyme such as hexokinase-2 resulted in cell growth retardation at higher degree in LCC2 and LCC9 than that in MCF7S. This implies that increased aerobic glycolysis even under O₂-rich conditions, a phenomenon known as the Warburg effect, is closely associated with tamoxifen resistance. We found that HIF-1α is activated via an Akt/mTOR signaling pathway in LCC2 and LCC9 cells without hypoxic condition. Importantly, specific inhibition of hexokinase-2 suppressed the activity of Akt/mTOR/HIF-1α axis in LCC2 and LCC9 cells. In addition, the phosphorylated AMPK which is a negative regulator of mTOR was decreased in LCC2 and LCC9 cells compared to MCF7S. Interestingly, either the inhibition of mTOR activity or increase in AMPK activity induced a reduction in lactate accumulation and cell survival in the LCC2 and LCC9 cells. Taken together, our data provide evidence that development of tamoxifen resistance may be driven by HIF-1α hyperactivation via modulation of Akt/mTOR and/or AMPK signaling pathways. Therefore, we suggest that the HIF-1α hyperactivation is a critical marker of increased aerobic glycolysis in accordance with tamoxifen resistance and thus restoration of aerobic glycolysis may be novel therapeutic target for treatment of tamoxifen-resistant breast cancer.

Rapid analysis of glycolytic and oxidative substrate flux of cancer cells in a microplate

Cancer cells exhibit remarkable alterations in cellular metabolism, particularly in their nutrient substrate preference. We have devised several experimental methods that rapidly analyze the metabolic substrate flux in cancer cells: glycolysis and the oxidation of major fuel substrates glucose, glutamine, and fatty acids. Using the XF Extracellular Flux analyzer, these methods measure, in real-time, the oxygen consumption rate (OCR) and extracellular acidification rate (ECAR) of living cells in a microplate as they respond to substrates and metabolic perturbation agents. In proof-of-principle experiments, we analyzed substrate flux and mitochondrial bioenergetics of two human glioblastoma cell lines, SF188s and SF188f, which were derived from the same parental cell line but proliferate at slow and fast rates, respectively. These analyses led to three interesting observations: 1) both cell lines respired effectively with substantial endogenous substrate respiration; 2) SF188f cells underwent a significant shift from glycolytic to oxidative metabolism, along with a high rate of glutamine oxidation relative to SF188s cells; and 3) the mitochondrial proton leak-linked respiration of SF188f cells increased significantly compared to SF188s cells. It is plausible that the proton leak of SF188f cells may play a role in allowing continuous glutamine-fueled anaplerotic TCA cycle flux by partially uncoupling the TCA cycle from oxidative phosphorylation. Taken together, these rapid, sensitive and high-throughput substrate flux analysis methods introduce highly valuable approaches for developing a greater understanding of genetic and epigenetic pathways that regulate cellular metabolism, and the development of therapies that target cancer metabolism.

Dephosphorylation and biodistribution of 1-¹³C-phospholactate in vivo

Here, we present a new approach for the delivery of a metabolic contrast agent for in vivo molecular imaging. The use of a phosphate-protecting group that facilitates parahydrogen-induced polarization of 1-(13)C-phospholactate potentially enables the in vivo administration of a hydrogenated hyperpolarized adduct. When injected, nonhyperpolarized 1-(13)C-phospholactate is retained in the vasculature during its metabolic conversion to 1-(13)C-lactate by blood phosphatases as demonstrated here using a mucin 1 mouse model of breast cancer and ex vivo high-resolution (13)C NMR. This multisecond process is a suitable mechanism for the delivery of relatively short-lived (13)C and potentially (15)N hyperpolarized contrast agents using -OH phosphorylated small molecules, which is demonstrated here for the first time as an example of 1-(13)C-phospholactate. Through this approach, DL-1-(13)C-lactate is taken up by tissues and organs including the liver, kidneys, brain, heart, and tumors according to a timescale amenable to hyperpolarized magnetic resonance imaging.

Systematic nucleo-cytoplasmic trafficking of proteins following exposure of MCF7 breast cancer cells to estradiol

We have used a proteomics subcellular spatial razor approach to look at changes in total protein abundance and in protein distribution between the nucleus and cytoplasm following exposure of MCF7 breast cancer cells to estradiol. The dominant response of MCF7 cells to estrogen stimulation involves dynamic changes in protein subcellular spatial distribution rather than changes in total protein abundance. Of the 3604 quantitatively monitored proteins, only about 2% show substantial changes in total abundance (>2-fold), whereas about 20% of the proteins show substantial changes in local abundance and/or redistribution of their subcellular location, with up to 16-fold changes in their local concentration in the nucleus or the cytoplasm. We propose that dynamic redistribution of the subcellular location of multiple proteins in response to stimuli is a fundamental characteristic of cells and suggest that perturbation of cellular spatial control may be an important feature of cancer.

Hyperpolarized 13C NMR studies of glucose metabolism in living breast cancer cell cultures

The recent development of dissolution dynamic nuclear polarization (DNP) gives NMR the sensitivity to follow metabolic processes in living systems with high temporal resolution. In this article, we apply dissolution DNP to study the metabolism of hyperpolarized U-(13)C,(2)H7-glucose in living, perfused human breast cancer cells. Spectrally selective pulses were used to maximize the signal of the main product, lactate, whilst preserving the glucose polarization; in this way, both C1-lactate and C3-lactate could be observed with high temporal resolution. The production of lactate by T47D breast cancer cells can be characterized by Michaelis-Menten-like kinetics, with K(m) = 3.5 ± 1.5 mM and V(max) = 34 ± 4 fmol/cell/min. The high sensitivity of this method also allowed us to observe and quantify the glycolytic intermediates dihydroxyacetone phosphate and 3-phosphoglycerate. Even with the enhanced DNP signal, many other glycolytic intermediates could not be detected directly. Nevertheless, by applying saturation transfer methods, the glycolytic intermediates glucose-6-phosphate, fructose-6-phosphate, fructose-1,6-bisphosphate, glyceraldehyde-3-phosphate, phosphoenolpyruvate and pyruvate could be observed indirectly. This method shows great promise for the elucidation of the distinctive metabolism and metabolic control of cancer cells, suggesting multiple ways whereby hyperpolarized U-(13)C,(2)H7-glucose NMR could aid in the diagnosis and characterization of cancer in vivo.

Role of the hypothalamus in mediating protective effects of dietary restriction during aging

Dietary restriction (DR) can extend lifespan and reduce disease burden across a wide range of animals and yeast but the mechanisms mediating these remarkably protective effects remain to be elucidated despite extensive efforts. Although it has generally been assumed that protective effects of DR are cell-autonomous, there is considerable evidence that many whole-body responses to nutritional state, including DR, are regulated by nutrient-sensing neurons. In this review, we explore the hypothesis that nutrient sensing neurons in the ventromedial hypothalamus hierarchically regulate the protective responses of dietary restriction. We describe multiple peripheral responses that are hierarchically regulated by the hypothalamus and we present evidence for non-cell autonomous signaling of dietary restriction gathered from a diverse range of models including invertebrates, mammalian cell culture, and rodent studies.

Comparison of near-infrared fluorescent deoxyglucose probes with different dyes for tumor diagnosis in vivo

Glucose plays a central role in the cellular energy metabolism. Malignant tumors exhibit an elevated rate of glycolysis over normal tissues. In this study, two near-infrared fluorescent dyes, Cypate and ICG-Der-02, with different water solubility, were conjugated to 2-amino-2-deoxy-D-glucose (2DG) to form Cypate-2DG and ICG-Der-02-2DG, respectively, for NIR fluorescent imaging of tumors in nude mice. The clear routes and tumor targeting abilities of the two NIR fluorescent 2DG probes were compared. Results showed that ICG-Der-02-2DG with higher hydrophilicity was cleared faster by kidneys than the more lipophilic Cypate-2DG. Cypate-2DG had slower but stronger tumor targeting ability compared with ICG-Der-02-2DG. To investigate the correlation between the targeting ability of the probe and the glucose transporter (GLUT1) expression levels of cancer cells, the accumulation of Cypate-2DG in tumors was assessed in MCF-7/estradiol, U87MG, MCF-7 and MDA-MB-435 tumor xenografts, which express different levels of GLUT1. The results show that both Cypate-2DG and ICG-Der-02-2DG possess tumor targeting ability on all the tumors examined, with a proportional correlation to GLUT1 expression. The findings demonstrate the broad applicability of these molecular probes for optical imaging of tumors and glucose-related pathologies.

Roles of microRNA on cancer cell metabolism

Advanced studies of microRNAs (miRNAs) have revealed their manifold biological functions, including control of cell proliferation, cell cycle and cell death. However, it seems that their roles as key regulators of metabolism have drawn more and more attention in the recent years. Cancer cells display increased metabolic autonomy in comparison to non-transformed cells, taking up nutrients and metabolizing them in pathways that support growth and proliferation. MiRNAs regulate cell metabolic processes through complicated mechanisms, including directly targeting key enzymes or transporters of metabolic processes and regulating transcription factors, oncogenes / tumor suppressors as well as multiple oncogenic signaling pathways. MiRNAs like miR-375, miR-143, miR-14 and miR-29b participate in controlling cancer cell metabolism by regulating the expression of genes whose protein products either directly regulate metabolic machinery or indirectly modulate the expression of metabolic enzymes, serving as master regulators, which will hopefully lead to a new therapeutic strategy for malignant cancer. This review focuses on miRNA regulations of cancer cell metabolism,including glucose uptake, glycolysis, tricarboxylic acid cycle and insulin production, lipid metabolism and amino acid biogenesis, as well as several oncogenic signaling pathways. Furthermore, the challenges of miRNA-based strategies for cancer diagnosis, prognosis and therapeutics have been discussed.

Lactate and glycine-potential MR biomarkers of prognosis in estrogen receptor-positive breast cancers

Breast cancer is a heterogeneous disease with a variable prognosis. Clinical factors provide some information about the prognosis of patients with breast cancer; however, there is a need for additional information to stratify patients for improved and more individualized treatment. The aim of this study was to examine the relationship between the metabolite profiles of breast cancer tissue and 5-year survival. Biopsies from breast cancer patients (n=98) were excised during surgery and analyzed by high-resolution magic angle spinning MRS. The data were analyzed by multivariate principal component analysis and partial least-squares discriminant analysis, and the findings of important metabolites were confirmed by spectral integration of the metabolite peaks. Predictions of 5-year survival using metabolite profiles were compared with predictions using clinical parameters. Based on the metabolite profiles, patients with estrogen receptor (ER)-positive breast cancer (n=71) were separated into two groups with significantly different survival rates (p=0.024). Higher levels of glycine and lactate were found to be associated with lower survival rates by both multivariate analyses and spectral integration, and are suggested as biomarkers for breast cancer prognosis. Similar metabolic differences were not observed for ER-negative patients, where survivors could not be separated from nonsurvivors. Predictions of 5-year survival of ER-positive patients using metabolite profiles gave better and more robust results than those using traditional clinical parameters. The results imply that the metabolic state of a tumor may provide additional information concerning breast cancer prognosis. Further studies should be conducted in order to evaluate the role of MR metabolomics as an additional clinical tool for determining the prognosis of patients with breast cancer.

Progressive increase of glucose transporter-3 (GLUT-3) expression in estrogen-induced breast carcinogenesis

INTRODUCTION

Increased glucose uptake and glycolysis are main metabolic characteristics of malignant cells. A family of glucose transporters (GLUTs) facilitates glucose movement across the plasma membranes in a tumor-specific manner. Glucose transporter-1 (GLUT-1), GLUT-3 and recently GLUT-12, have been previously shown in breast cancer cells and are found to be associated with poor prognosis. In addition, it has been shown that estrogen plays critical roles in GLUT regulation, however, the stage-specific GLUT regulation of mammary carcinogenesis is unclear.

METHODS

GLUT expression patterns were investigated in an in vitro-in vivo progressive, estrogen-induced, mammary carcinogenesis model which consisted of four cell lines, with same genetic background. In this model, different stages of tumor initiation and progression are represented, MCF-10F being the normal stage, E2 cells the transformed stage by estrogen, C5 cells, the invasive stage, and T4 cells the tumorigenic stage. In addition, loss of ductulogenesis and solid mass formation in collagen matrix and invasiveness of the cells were counted.

RESULTS

Real time PCR showed that GLUT1 expression was downregulated in MCF10F after treatment with 17β-estradiol (E2), and in the invasive cell type (C5), but not in the tumor cells (T4), which had no changes compared to MCF10F. C5 and T4 cells showed the highest rate of GLUT-3 expression. These cells were also found to be associated with loss of ductulogenesis, solid mass formation and higher invasive capacity, whereas, GLUT-12 was downregulated in C5 and T4 cells.

CONCLUSION

Estrogen-induced malignant transformation is associated with remarkable and progressive GLUT-3 expression, GLUT-1 re-expression at further stages, as well as GLUT-12 downregulation.

Metabolic control analysis of cellular respiration in situ in intraoperational samples of human breast cancer

The aim of this study was to analyze quantitatively cellular respiration in intraoperational tissue samples taken from human breast cancer (BC) patients. We used oxygraphy and the permeabilized cell techniques in combination with Metabolic Control Analysis (MCA) to measure a corresponding flux control coefficient (FCC). The activity of all components of ATP synthasome, and respiratory chain complexes was found to be significantly increased in human BC cells in situ as compared to the adjacent control tissue. FCC(s) were determined upon direct activation of respiration with exogenously-added ADP and by titrating the complexes with their specific inhibitors to stepwise decrease their activity. MCA showed very high sensitivity of all complexes and carriers studied in human BC cells to inhibition as compared to mitochondria in normal oxidative tissues. The sum of FCC(s) for all ATP synthasome and respiratory chain components was found to be around 4, and the value exceeded significantly that for normal tissue (close to 1). In BC cells, the key sites of the regulation of respiration are Complex IV (FCC = 0.74), ATP synthase (FCC = 0.61), and phosphate carrier (FCC = 0.60); these FCC(s) exceed considerably (~10-fold) those for normal oxidative tissues. In human BC cells, the outer mitochondrial membrane is characterized by an increased permeability towards adenine nucleotides, the mean value of the apparent K(m) for ADP being equal to 114.8 ± 13.6 μM. Our data support the two-compartment hypothesis of tumor metabolism, the high sum of FCC(s) showing structural and functional organization of mitochondrial respiratory chain and ATP synthasome as supercomplexes in human BC.

Magnetic resonance spectroscopy of cancer metabolism and response to therapy

Magnetic resonance spectroscopy allows noninvasive in vivo measurements of biochemical information from living systems, ranging from cultured cells through experimental animals to humans. Studies of biopsies or extracts offer deeper insights by detecting more metabolites and resolving metabolites that cannot be distinguished in vivo. The pharmacokinetics of certain drugs, especially fluorinated drugs, can be directly measured in vivo. This review briefly describes these methods and their applications to cancer metabolism, including glycolysis, hypoxia, bioenergetics, tumor pH, and tumor responses to radiotherapy and chemotherapy.

Expression of GLUT1 and GLUT3 glucose transporters in endometrial and breast cancers

Cancer cells have accelerated metabolism and high glucose requirements. The up-regulation of specific glucose transporters may represent a key mechanism by which malignant cells may achieve increased glucose uptake to support the high rate of glycolysis. In present study we analyzed the mRNA and protein expression of GLUT1 and GLUT3 glucose transporters by quantitative real-time polymerase chain reaction (Q-PCR) and Western blotting technique in 76 cases of endometrial carcinoma and 70 cases of breast carcinoma. SLC2A1 and SLCA2A3 mRNAs expression was found, respectively in 100% and 97.4% samples of endometrial cancers and only in 50% and 40% samples of breast cancers. In endometrial cancers GLUT1 and GLUT3 protein expression was identified in 67.1% and 30.3% of cases. Analogously, in breast cancers in 48.7% and 21% of samples, respectively. The results showed that both endometrial and breast poorly differentiated tumors (grade 2 and 3) had significantly higher GLUT1 and GLUT3 expression than well-differentiated tumors (grade 1). Statistically significant association was found between SLCA2A3 mRNA expression and estrogen and progesterone receptors status in breast cancers. GLUT1 has been reported to be involved in the uptake of glucose by endometrial and breast carcinoma cells earlier and the present study determined that GLUT3 expression is also involved. GLUT1 and GLUT3 seem to be important markers in endometrial and breast tumors differentiation.

13C high-resolution-magic angle spinning MRS reveals differences in glucose metabolism between two breast cancer xenograft models with different gene expression patterns

Tumor cells have increased glycolytic activity, and glucose is mainly used to form lactate and alanine, even when high concentrations of oxygen are present (Warburg effect). The purpose of the present study was to investigate glucose metabolism in two xenograft models representing basal-like and luminal-like breast cancer using (13) C high-resolution-magic angle spinning (HR-MAS) MRS and gene expression analysis. Tumor tissue was collected from two groups for each model: untreated mice (n=19) and a group of mice (n=16) that received an injection of [1-(13) C]-glucose 10 or 15 min before harvesting the tissue. (13) C HR-MAS MRS was performed on the tumor samples and differences in the glucose/alanine (Glc/Ala), glucose/lactate (Glc/Lac) and alanine/lactate (Ala/Lac) ratios between the models were studied. The expression of glycolytic genes was studied using tumor tissue from the same models. In the natural abundance MR spectra, a significantly lower Glc/Ala and Glc/Lac ratio (p<0.001) was observed in the luminal-like model compared with the basal-like model. In the labeled samples, the predominant glucose metabolites were lactate and alanine. Significantly lower Glc/Ala and Glc/Lac ratios were observed in the luminal-like model (p<0.05). Most genes contributing to glycolysis were expressed at higher levels in the luminal-like model (fdr<0.001). The lower Glc/Ala and Glc/Lac ratios and higher glycolytic gene expression observed in the luminal-like model indicates that the transformation of glucose to lactate and alanine occurred faster in this model than in the basal-like model, which has a growth rate several times faster than that of the luminal-like model. The results from the present study suggest that the tumor growth rate is not necessarily a determinant of glycolytic activity.

Uptake of 2-NBDG as a method to monitor therapy response in breast cancer cell lines

This study quantifies uptake of a fluorescent glucose analog, (2-(N-(7-nitrobenz-2-oxa-1,3-diazol-4-yl)amino)-2-deoxyglucose) (2-NBDG), in a large panel of breast cancer cells and demonstrates potential to monitor changes in glycolysis caused by anticancer and endocrine therapies. Expressions of glucose transporter (GLUT 1) and hexokinase (HK I), which phosphorylates 2-NBDG, were measured via western blot in two normal mammary epithelial and eight breast cancer cell lines of varying biological subtype. Fluorescence intensity of each cell line labeled with 100 lM 2-NBDG for 20 min or unlabeled control was quantified. A subset of cancer cells was treated with anticancer and endocrine therapies, and 2-NBDG fluorescence changes were measured. Expression of GLUT 1 was necessary for uptake of 2-NBDG, as demonstrated by lack of 2-NBDG uptake in normal human mammary epithelial cells (HMECs). GLUT 1 expression and 2-NBDG uptake was ubiquitous among all breast cancer lines. Reduction and stimulation of 2-NBDG uptake was demonstrated by perturbation with anticancer agents, lonidamine (LND), and a-cyano-hydroxycinnamate (a-Cinn), respectively. LND directly inhibits HK and significantly reduced 2-NBDG fluorescence in a subset of two breast cancer cell lines. Conversely, when cells were treated with a-Cinn, a drug used to increase glycolysis, 2-NBDG uptake was increased. Furthermore, tamoxifen (tam), a common endocrine therapy, was administered to estrogen receptor positive and negative (ER?/-) breast cells and demonstrated a decreased 2-NBDG uptake in ER? cells, reflecting a decrease in glycolysis. Results indicate that 2-NBDG uptake can be used to measure changes in glycolysis and has potential for use in early drug development.

Metabolic effects of signal transduction inhibition in cancer assessed by magnetic resonance spectroscopy

Despite huge efforts in development of drugs targeting oncogenic signalling, the number of such drugs entering clinical practice to date remains limited. Rational use of biomarkers for drug candidate selection and early monitoring of response to therapy may accelerate this process. Magnetic resonance spectroscopy (MRS) can be used to assess metabolic effects of drug treatment both in vivo and in vitro, and technological advances are continuously increasing the utility of this non-invasive method. In this review, we summarise the use of MRS for monitoring the effect of targeted anticancer drugs, and discuss the potential role of MRS in the context of personalised cancer treatment.

SIRT3 opposes reprogramming of cancer cell metabolism through HIF1α destabilization

Tumor cells exhibit aberrant metabolism characterized by high glycolysis even in the presence of oxygen. This metabolic reprogramming, known as the Warburg effect, provides tumor cells with the substrates required for biomass generation. Here, we show that the mitochondrial NAD-dependent deacetylase SIRT3 is a crucial regulator of the Warburg effect. Mechanistically, SIRT3 mediates metabolic reprogramming by destabilizing hypoxia-inducible factor-1α (HIF1α), a transcription factor that controls glycolytic gene expression. SIRT3 loss increases reactive oxygen species production, leading to HIF1α stabilization. SIRT3 expression is reduced in human breast cancers, and its loss correlates with the upregulation of HIF1α target genes. Finally, we find that SIRT3 overexpression represses glycolysis and proliferation in breast cancer cells, providing a metabolic mechanism for tumor suppression.

Mitochondrial proteomics analysis of tumorigenic and metastatic breast cancer markers

Mitochondria are key organelles in mammary cells responsible for several cellular functions including growth, division, and energy metabolism. In this study, mitochondrial proteins were enriched for proteomics analysis with the state-of-the-art two-dimensional differential gel electrophoresis and matrix-assistant laser desorption ionization-time-of-flight mass spectrometry strategy to compare and identify the mitochondrial protein profiling changes between three breast cell lines with different tumorigenicity and metastasis. The proteomics results demonstrate more than 1,500 protein features were resolved from the equal amount pooled from three purified mitochondrial proteins, and 125 differentially expressed spots were identified by their peptide finger print, in which, 33 identified proteins belonged to mitochondrial proteins. Eighteen out of these 33 identified mitochondrial proteins such as SCaMC-1 have not been reported in breast cancer research to our knowledge. Additionally, mitochondrial protein prohibitin has shown to be differentially distributed in mitochondria and in nucleus for normal breast cells and breast cancer cell lines, respectively. To sum up, our approach to identify the mitochondrial proteins in various stages of breast cancer progression and the identified proteins may be further evaluated as potential breast cancer markers in prognosis and therapy.

17beta-estradiol augments 18F-FDG uptake and glycolysis of T47D breast cancer cells via membrane-initiated rapid PI3K-Akt activation

Use of (18)F-FDG uptake as a surrogate marker of therapeutic response requires the recognition of biologic factors that influence cancer cell glucose metabolism. Estrogen is a potent stimulator of breast cancer proliferation, a process that requires sufficient energy, which is likely met by increased glycolysis. We thus explored the effect of estrogen on (18)F-FDG uptake in responsive breast cancer cells and investigated the mediating molecular mechanisms.

METHODS

T47D breast cancer cells were stimulated with 17β-estradiol (E(2)) or bovine serum albumin (BSA)-E(2) and measured for (18)F-FDG uptake, lactate release, and mitochondrial hexokinase activity. The effects of antiestrogens, cycloheximide, and major protein kinase inhibitors were investigated. Immunoblots were performed for membrane glucose transporter type 1, phosphorylated phosphatidylinositol 3-kinase (PI3K), and Akt.

RESULTS

E(2) augmented T47D cell (18)F-FDG uptake in a dose- and time-dependent manner that preceded and surpassed its proliferative effect. With exposure to 10 nM E(2), protein content-corrected (18)F-FDG uptake reached 172.7% ± 6.6% and 294.4% ± 9.5% of controls by 24 and 48 h, respectively. Lactate release reached 110.9% ± 7.3% and 145.2% ± 10.5% of controls at 24 and 48 h, and mitochondrial hexokinase activity increased to 187.1% ± 31.6% at 24 h. Membrane glucose transporter type 1 expression was unaltered. The effect was absent in estrogen receptor (ER)-negative breast cancer cells and was abrogated by ICI182780, indicating ER dependence. The E(2) effect was not blocked by tamoxifen and was mimicked by membrane-impermeable BSA-E(2), consistent with nongenomic membrane-initiated E(2) action. Inhibition by cycloheximide demonstrated the requirement of a new protein synthesis. Immunoblots displayed rapid phosphorylation of PI3K and Akt within minutes of E(2) treatment, and the specific PI3K inhibitors wortmannin and LY294002 abolished the ability of E(2) to elevate (18)F-FDG uptake.

CONCLUSION

Estrogen augments breast cancer cell (18)F-FDG uptake by stimulating glycolysis and hexokinase activity via membrane-initiated E(2) action that activates the PI3K-Akt pathway. These findings yield important insight into our understanding of the biology of breast cancer metabolism and may have potential implications for (18)F-FDG uptake as a surrogate marker of therapeutic response.

Fast volumetric spatial-spectral MR imaging of hyperpolarized 13C-labeled compounds using multiple echo 3D bSSFP

PURPOSE

The goal of this work was to develop a fast 3D chemical shift imaging technique for the noninvasive measurement of hyperpolarized (13)C-labeled substrates and metabolic products at low concentration.

MATERIALS AND METHODS

Multiple echo 3D balanced steady state magnetic resonance imaging (ME-3DbSSFP) was performed in vitro on a syringe containing hyperpolarized [1,3,3-2H3; 1-(13)C]2-hydroxyethylpropionate (HEP) adjacent to a (13)C-enriched acetate phantom, and in vivo on a rat before and after intravenous injection of hyperpolarized HEP at 1.5 T. Chemical shift images of the hyperpolarized HEP were derived from the multiple echo data by Fourier transformation along the echoes on a voxel by voxel basis for each slice of the 3D data set.

RESULTS

ME-3DbSSFP imaging was able to provide chemical shift images of hyperpolarized HEP in vitro, and in a rat with isotropic 7-mm spatial resolution, 93 Hz spectral resolution and 16-s temporal resolution for a period greater than 45 s.

CONCLUSION

Multiple echo 3D bSSFP imaging can provide chemical shift images of hyperpolarized (13)C-labeled compounds in vivo with relatively high spatial resolution and moderate spectral resolution. The increased signal-to-noise ratio of this 3D technique will enable the detection of hyperpolarized (13)C-labeled metabolites at lower concentrations as compared to a 2D technique.