Metabolic Alterations In Cancer Cells Research Articles

Multiparametric High-Resolution MRI as a Tool for Mapping of Hypoxic Level in Tumors.

Hypoxia is a condition, common to most malignant tumors, where oxygen tension in the tissue is below the physiological level. Among consequences of tumor hypoxia is also altered cancer cell metabolism that contributes to cancer therapy resistance. Therefore, precise assessment of tumor hypoxia is important for monitoring the tumor treatment progression. In this study, we propose a simple model for prediction of hypoxic level in tumors based on multiparametric magnetic resonance imaging. The study was performed on B16F1 murine melanoma tumors ex vivo that were first magnetic resonance scanned and then analyzed for hypoxic level using hypoxia-inducable factor 1-alpha antibody staining. Each tumor was analyzed in identical sections and in identical regions of interest for pairs of hypoxic level and magnetic resonance values (apparent diffusion coefficient and T 2). This was followed by correlation analysis between hypoxic level and respective magnetic resonance values. A moderate correlation was found between hypoxic level and apparent diffusion coefficient (ρ = 0.56, P < .00001) and lower between hypoxic level and T 2 (ρ = 0.38, P < .00001). The data were analyzed further to obtain simple predictive models based on the multiple linear regression analysis of the measured hypoxic level (dependent variable) and apparent diffusion coefficient and T 2 (independent variables). Among the hypoxic level models, the most efficient was the 3-parameter model given by relation (HL = k ADC ADC + k T2 T 2 + b), where k ADC = 26%/µm2/ms, k T2 = 0.8%/ms, and b = −32%. The model can be used for calculation of the predicted hypoxic level map based on magnetic resonance–measured apparent diffusion coefficient and T 2 maps. Similar prediction models, based on tumor apparent diffusion coefficient and T 2 maps, can be done also for other tumor types in vivo and can therefore help in assessment of tumor treatment as well as to better understand the role of hypoxia in cancer progression.

Multi-omics analysis reveals that ornithine decarboxylase contributes to erlotinib resistance in pancreatic cancer cells.

Molecular and metabolic alterations in cancer cells are one of the leading causes of acquired resistance to chemotherapeutics. In this study, we explored an experimental strategy to identify which of these alterations can induce erlotinib resistance in human pancreatic cancer. Using genetically matched erlotinib-sensitive (BxPC-3) and erlotinib-resistant (BxPC-3ER) pancreatic cancer cells, we conducted a multi-omics analysis of metabolomes and transcriptomes in these cells. Untargeted and targeted metabolomic analyses revealed significant changes in metabolic pathways involved in the regulation of polyamines, amino acids, and fatty acids. Further transcriptomic analysis identified that ornithine decarboxylase (ODC) and its major metabolite, putrescine, contribute to the acquisition of erlotinib resistance in BxPC-3ER cells. Notably, either pharmacological or genetic blockage of ODC was able to restore erlotinib sensitivity, and this could be rescued by treatment with exogenous putrescine in erlotinib-resistant BxPC-3ER cells. Moreover, using a panel of cancer cells we demonstrated that ODC expression levels in cancer cells are inversely correlated with sensitivity to chemotherapeutics. Taken together, our findings will begin to uncover mechanisms of acquired drug resistance and ultimately help to identify potential therapeutic markers in cancer.

Oncogenic Activities of IDH1/2 Mutations: From Epigenetics to Cellular Signaling.

Gliomas and leukemias remain highly refractory to treatment, thus highlighting the need for new and improved therapeutic strategies. Mutations in genes encoding enzymes involved in the tricarboxylic acid (TCA) cycle, such as the isocitrate dehydrogenases 1 and 2 (IDH1/2), are frequently encountered in astrocytomas and secondary glioblastomas, as well as in acute myeloid leukemias; however, the precise molecular mechanisms by which these mutations promote tumorigenesis remain to be fully characterized. Gain-of-function mutations in IDH1/2 have been shown to stimulate production of the oncogenic metabolite R-2-hydroxyglutarate (R-2HG), which inhibits α-ketoglutarate (αKG)-dependent enzymes. We review recent advances on the elucidation of oncogenic functions of IDH1/2 mutations, and of the associated oncometabolite R-2HG, which link altered metabolism of cancer cells to epigenetics, RNA methylation, cellular signaling, hypoxic response, and DNA repair.

Fatty acid metabolism and prospects for targeted therapy of cancer

Fatty acids are fundamental substrates required for energy storage, synthesis of membranes, generation of signaling molecules and lipid droplet formation in cancer cells. High levels of fatty acid metabolic activity are one of the most aberrant metabolic alterations in cancer cells. The de novo fatty acid synthesis pathway is the primary source of fatty acids in cancer cells, but cancer cells can also acquire fatty acids through the lipolytic pathway, which helps cells survive and maintain their invasiveness. Key enzymes, including ATP‐citrate lyase (ACLY), fatty acid synthase (FASN), acetyl‐coenzyme A (CoA) carboxylase (ACC), stearoyl‐CoA desaturase 1(SCD1) and monoacylglycerol lipase (MAGL), which are involved in fatty acid synthesis and degradation, are overexpressed in cancer cells. The alterations in fatty acid metabolomics in different cancers, at different stages of cancer, and in different tissues are clinically significant. This review focuses on current research into fatty acid metabolism to explore new targets against the fatty acid metabolic pathways for anticancer therapy.Practical applications: High levels of fatty acid metabolic activity are one of the most aberrant metabolic alterations in cancer cells. Reprogramming in fatty acid metabolism plays an important role in energy storage, membrane proliferation, the generation of signaling molecules and lipid droplet formation in cancer cells. Understanding the mechanism of regulated the fatty acid metabolic pathways in cancer would reveal novel targeted therapy of cancer.To maintain the balance of the free fatty acid composition and thus promote cancer cell growth, survival, and progression, the levels of de novo fatty acid synthesis and degradation are elevated. Therefore, the targeted inhibition of key enzymes involved in fatty acid metabolism, such as ACLY, ACC, FASN, MAGL, and SCD1, and the utilization of anticancer exogenous fatty acids might constitute effective cancer therapies. ATP, adenosine‐triphosphate; DAG, diacylglycerol; IHBTIS, inhibitors; MUFA, monounsaturated fatty acids; MAG, monoacylglycerol; TAG triacylglycerol.

Abstract 441: GOT1 regulates anaplerotic glutamine metabolism under chronic acidosis stress in pancreatic cancer

Abstract Epithelial-cell derived tumors exhibit the Warburg effect that is characterized by an increased rate of glycolysis and lactate release, as well as, reduced oxidative metabolism. It is known that these metabolic alterations of cancer cells result in a tumor microenvironment with a lower pH than that of the plasma. However, little is known regarding the physiology and metabolism of cancer cells enduring chronic acidosis. Here, we cultured pancreatic cancer cells in chronic acidosis, i.e. pH 6.9 to 7.0, and observed a shift from glycolytic metabolism to oxidative metabolism that also results in reduced cell growth and increased intracellular ROS levels. We identified that this is due to an increase in glutamine uptake and increased expression of the transaminase enzyme GOT1 that enhances glutamine metabolism. Survival in low pH is reduced upon depletion of GOT1 due to further increased intracellular ROS levels. Thus, GOT1 plays an important role in energy metabolism and ROS balance in chronic acidosis stress. Our studies suggest the therapeutic potential of targeting anaplerotic glutamine metabolism in pancreatic cancer. Citation Format: Jaime Abrego, Venugopal Gunda, Enza Vernucci, Surendra Shukla, Ryan J. King, Aneesha Dasgupta, Nina Chaika, Pankaj Kumar Singh. GOT1 regulates anaplerotic glutamine metabolism under chronic acidosis stress in pancreatic cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 441. doi:10.1158/1538-7445.AM2017-441

Biology of glucose metabolization in cancer cells

Abstract Cancer is a disease at the cellular level involving heritable disorders in cellular control mechanism. Cancer cells also need to adapt their metabolism to survive and multiply under the metabolically compromised conditions provided by the tumor microenvironment. Tumor cells alter their metabolism to maintain unregulated cellular proliferation and survival, but this transformation leaves them reliant on constant supply of nutrients and energy. They alter their metabolism to support their rapid proliferation and expansion across the body. After the discovery of based on the altered cancer cell metabolism in 1930, loads of studies have shed light on several aspects of cancer metabolism with a common goal to find new ways for effectively eliminating tumor cells by targeting their energy metabolism. Research has directed most of its resources to elucidate the causes, prevention and possible cure for cancer, yet the process has been elusive claiming human lives more than ever. This disease is a manifestation of etiological and pathological disturbances of mechanisms that control cell division, differentiation and metabolism. 50% of all human tumors carry genetic alterations that lead to the inactivation of some tumor suppressor proteins. Cancer cells are shown to experience characteristic changes in their metabolic programs, including increased uptake of glucose, enhanced rates of glutaminolysis and fatty acids synthesis, suggesting that metabolic shifts supports tumor cells growth and survival. In this review, we summarized the major concepts of glucose metabolization and explore the molecular basis of aerobic glycolysis of cancer cells.

Abstract 5893: Bioenergetic signature from cocultures of pancreatic tumor cell lines and fibroblasts

Abstract Pancreatic ductal adenocarcinoma (PDAC) is one of the tumors with greater invasiveness and metastasis. PDAC is associated with a large desmoplastic reaction, characterized by fibroblastic proliferation and extracellular matrix secretion. Besides, cellular bioenergetics has become a central issue of investigation in cancer biology, because the altered energy metabolism of cancer cells has been proposed as a potential target for cancer treatment. We have established co-cultures between PDAC cell lines (Capan-1 or PL-45) and fibroblasts (LC5). A reverse phase protein microarray (RPMA) approach has been applied to quantify proteins of energy metabolism in theses co-cultures, with the aim of identifying potential biomarkers in PDACs. The fifteen proteins of energy metabolism studied included members of the mitochondrial oxidation of pyruvate, the tricarboxylic acid cycle, β-oxidation of fatty acids, electron transport and oxidative phosphorylation, glycogen metabolism, glycolysis and oxidative stress using highly specific antibodies. Co-cultures modified proteins expression of energy metabolism, respect to monocultures. Capan-1 in co-culture increased several proteins belonging to OXPHOS (NDUFS3, SDHB, CORE2 and COXII), the antioxidant SOD2, the mitochondrial HSP60, and G6PDH. The expression of the glycolitic PKM2 decreased. Their fibroblasts partners increased the expression of SDHB and also decreased PKM2. PL-45 in co-culture, experimented an increase in HADHA. Their fibroblasts partners showed a decrease in PKM2, LDHA, IF1, PDHe and HSP60.Capann-1 and PL-45 in co-culture with fibroblast, differ en their energy metabolism phenotype. Overall, the results indicate that the quantification of bioenergetic signature offers potential biomarkers that could be implemented to refine the understanding of the biological principles of PDAC and, eventually, the management of patients with these tumors. Citation Format: Mª Teresa Agulló-Ortuño, Elena Prieto-García, C. Vanesa Díaz-García, Irene Otero Blas, Inmaculada García-Ruíz, José A. López-Martín. Bioenergetic signature from cocultures of pancreatic tumor cell lines and fibroblasts [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 5893. doi:10.1158/1538-7445.AM2017-5893

Multifaceted Roles of Glutathione and Glutathione-Based Systems in Carcinogenesis and Anticancer Drug Resistance.

Glutathione is the most abundant antioxidant molecule in living organisms and has multiple functions. Intracellular glutathione homeostasis, through its synthesis, consumption, and degradation, is an intricately balanced process. Glutathione levels are often high in tumor cells before treatment, and there is a strong correlation between elevated levels of intracellular glutathione/sustained glutathione-mediated redox activity and resistance to pro-oxidant anticancer therapy. Recent Advances: Ample evidence demonstrates that glutathione and glutathione-based systems are particularly relevant in cancer initiation, progression, and the development of anticancer drug resistance. This review highlights the multifaceted roles of glutathione and glutathione-based systems in carcinogenesis, anticancer drug resistance, and clinical applications. The evidence summarized here underscores the important role played by glutathione and the glutathione-based systems in carcinogenesis and anticancer drug resistance. Future studies should address mechanistic questions regarding the distinct roles of glutathione in different stages of cancer development and cancer cell death. It will be important to study how metabolic alterations in cancer cells can influence glutathione homeostasis. Sensitive approaches to monitor glutathione dynamics in subcellular compartments will be an indispensible step. Therapeutic perspectives should focus on mechanism-based rational drug combinations that are directed against multiple redox targets using effective, specific, and clinically safe inhibitors. This new strategy is expected to produce a synergistic effect, prevent drug resistance, and diminish doses of single drugs. Antioxid. Redox Signal. 27, 1217-1234.

Targeting metabolic reprogramming in KRAS-driven cancers.

Mutations of KRAS are found in a variety of human malignancies, including in pancreatic cancer, colorectal cancer, and non-small cell lung cancer at high frequency. To date, no effective treatments that target mutant variants of KRAS have been introduced into clinical practice. In recent years, a number of studies have shown that the oncogene KRAS plays a critical role in controlling cancer metabolism by orchestrating multiple metabolic changes. One of the metabolic hallmarks of malignant tumor cells is their dependency on aerobic glycolysis, known as the Warburg effect. The role of KRAS signaling in the regulation of aerobic glycolysis has been reported in several types of cancer. KRAS-driven cancers are characterized by altered metabolic pathways involving enhanced nutrients uptake, enhanced glycolysis, enhanced glutaminolysis, and elevated synthesis of fatty acids and nucleotides. However, Just how mutated KRAS can coordinate the metabolic shift to promote tumor growth and whether specific metabolic pathways are essential for the tumorigenesis of KRAS-driven cancers are questions which remain to be answered. In this context, the aim of this review is to summarize current data on KRAS-related metabolic alterations in cancer cells. Given that cancer cells rely on changes in metabolism to support their growth and survival, the targeting of metabolic processes may be a potential strategy for treating KRAS-driven cancers.

Mitochondrial dysregulation and glycolytic insufficiency functionally impair CD8 T cells infiltrating human renal cell carcinoma.

Cancer cells can inhibit effector T cells (Teff) through both immunomodulatory receptors and the impact of cancer metabolism on the tumor microenvironment. Indeed, Teff require high rates of glucose metabolism, and consumption of essential nutrients or generation of waste products by tumor cells may impede essential T cell metabolic pathways. Clear cell renal cell carcinoma (ccRCC) is characterized by loss of the tumor suppressor von Hippel-Lindau (VHL) and altered cancer cell metabolism. Here, we assessed how ccRCC influences the metabolism and activation of primary patient ccRCC tumor infiltrating lymphocytes (TIL). CD8 TIL were abundant in ccRCC, but they were phenotypically distinct and both functionally and metabolically impaired. ccRCC CD8 TIL were unable to efficiently uptake glucose or perform glycolysis and had small, fragmented mitochondria that were hyperpolarized and generated large amounts of ROS. Elevated ROS was associated with downregulated mitochondrial SOD2. CD8 T cells with hyperpolarized mitochondria were also visible in the blood of ccRCC patients. Importantly, provision of pyruvate to bypass glycolytic defects or scavengers to neutralize mitochondrial ROS could partially restore TIL activation. Thus, strategies to improve metabolic function of ccRCC CD8 TIL may promote the immune response to ccRCC.

Differential regulation of monocarboxylate transporter 8 expression in thyroid cancer and hyperthyroidism.

Thyroid hormone (TH) transporters are expressed in thyrocytes and most play a role in TH release. We asked whether expression of the monocarboxylate transporter 8 (MCT8) and the L-type amino acid transporters LAT2 and LAT4 is changed with thyrocyte dedifferentiation and in hyperfunctioning thyroid tissues. Protein expression and localization of transporters was determined by immunohistochemistry in human thyroid specimen including normal thyroid tissue (NT, n = 19), follicular adenoma (FA, n = 44), follicular thyroid carcinoma (FTC, n = 45), papillary thyroid carcinoma (PTC, n = 40), anaplastic thyroid carcinoma (ATC, n = 40) and Graves' disease (GD, n = 50) by calculating the 'hybrid' (H) score. Regulation of transporter expression was investigated in the rat follicular thyroid cell line PCCL3 under basal and thyroid stimulating hormone (TSH) conditions. MCT8 and LAT4 were localized at the plasma membrane, while LAT2 transporter showed cytoplasmic localization. MCT8 expression was downregulated in benign and malignant thyroid tumours as compared to NT. In contrast, significant upregulation of MCT8, LAT2 and LAT4 was found in GD. Furthermore, a stronger expression of MCT8 was demonstrated in PCCL3 cells after TSH stimulation. Downregulation of MCT8 in thyroid cancers qualifies MCT8 as a marker of thyroid differentiation. The more variable expression of LATs in distinct thyroid malignancies may be linked with other transporter properties relevant to altered metabolism in cancer cells, i.e. amino acid transport. Consistent upregulation of MCT8 in GD is in line with increased TH release in hyperthyroidism, an assumption supported by our in vitro results showing TSH-dependent upregulation of MCT8.

Preclinical characterization of abemaciclib in hormone receptor positive breast cancer.

Abemaciclib is an ATP-competitive, reversible kinase inhibitor selective for CDK4 and CDK6 that has shown antitumor activity as a single agent in hormone receptor positive (HR+) metastatic breast cancer in clinical trials. Here, we examined the mechanistic effects of abemaciclib treatment using in vitro and in vivo breast cancer models. Treatment of estrogen receptor positive (ER+) breast cancer cells with abemaciclib alone led to a decrease in phosphorylation of Rb, arrest at G1, and a decrease in cell proliferation. Moreover, abemaciclib exposure led to durable inhibition of pRb, TopoIIα expression and DNA synthesis, which were maintained after drug removal. Treatment of ER+ breast cancer cells also led to a senescence response as indicated by accumulation of β-galactosidase, formation of senescence-associated heterochromatin foci, and a decrease in FOXM1 positive cells. Continuous exposure to abemaciclib altered breast cancer cell metabolism and induced apoptosis. In a xenograft model of ER+ breast cancer, abemaciclib monotherapy caused regression of tumor growth. Overall these data indicate that abemaciclib is a CDK4 and CDK6 inhibitor that, as a single agent, blocks breast cancer cell progression, and upon longer treatment can lead to sustained antitumor effects through the induction of senescence, apoptosis, and alteration of cellular metabolism.

Anti-cancer agents and reactive oxygen species modulators that target cancer cell metabolism

Abstract Traditionally the perspective on reactive oxygen species (ROS) has centered on the role they play as carcinogenic or cancer-causing radicals. Over the years, characterization and functional studies have revealed the complexity of ROS as signaling molecules that regulate various physiological cellular responses or whose levels are altered in various diseases. Cancer cells often maintain high basal level of ROS and are vulnerable to any further increase in ROS levels beyond a certain protective threshold. Consequently, ROS-modulation has emerged as an anticancer strategy with synthesis of various ROS-inducing or responsive agents that target cancer cells. Of note, an increased carbohydrate uptake and/or induction of death receptors of cancer cells was exploited to develop glycoconjugates that potentially induce cellular stress, ROS and apoptosis. This mini review highlights the development of compounds that target cancer cells by taking advantage of redox or metabolic alteration in cancer cells.

Metabolic reprogramming in cancer cells, consequences on pH and tumour progression: Integrated therapeutic perspectives with dietary lipids as adjuvant to anticancer treatment.

While tumours arise from acquired mutations in oncogenes or tumour-suppressor genes, it is clearly established that cancers are metabolic diseases characterized by metabolic alterations in tumour cells, and also non-tumour cells of the host organism resulting in tumour cachexia and patient weakness. In this review, we aimed at delineating details by which metabolic alterations in cancer cells, characterized by mitochondrial bioenergetics deregulations and the preference for aerobic glycolysis, are critical parameters controlling the aggressive progression of tumours. In particular, metabolic alteration in cancer cells are coupled to the modulation of intracellular and extracellular pH, epithelial-to-mesenchymal transition and associated increased invasiveness, autophagy, and the development of anticancer treatment resistance. Finally, based on mechanistic, pre-clinical and clinical studies, we proposed the adjuvant supplementation of dietary n-3 polyunsaturated fatty acids for a complementary holistic treatment of the cancer disease.

Metabolic origins of spatial organization in the tumor microenvironment

The genetic and phenotypic diversity of cells within tumors is a major obstacle for cancer treatment. Because of the stochastic nature of genetic alterations, this intratumoral heterogeneity is often viewed as chaotic. Here we show that the altered metabolism of cancer cells creates predictable gradients of extracellular metabolites that orchestrate the phenotypic diversity of cells in the tumor microenvironment. Combining experiments and mathematical modeling, we show that metabolites consumed and secreted within the tumor microenvironment induce tumor-associated macrophages (TAMs) to differentiate into distinct subpopulations according to local levels of ischemia and their position relative to the vasculature. TAMs integrate levels of hypoxia and lactate into progressive activation of MAPK signaling that induce predictable spatial patterns of gene expression, such as stripes of macrophages expressing arginase 1 (ARG1) and mannose receptor, C type 1 (MRC1). These phenotypic changes are functionally relevant as ischemic macrophages triggered tube-like morphogenesis in neighboring endothelial cells that could restore blood perfusion in nutrient-deprived regions where angiogenic resources are most needed. We propose that gradients of extracellular metabolites act as tumor morphogens that impose order within the microenvironment, much like signaling molecules convey positional information to organize embryonic tissues. Unearthing embryology-like processes in tumors may allow us to control organ-like tumor features such as tissue repair and revascularization and treat intratumoral heterogeneity.

Metabolomics of cancer cell cultures to assess the effects of dietary phytochemicals

ABSTRACTCancer is a multi-factorial disease and is a major cause of morbidity and mortality worldwide. Dietary phytochemicals have been used for the treatment of cancer throughout history due to their safety, low toxicity, and general availability. Several studies have been performed to elucidate the effects of dietary phytochemicals on cancer metabolism, and many molecular targets of phytochemicals have been discovered. In spite of remarkable progress, their effects on cancer metabolism have not yet been fully clarified. Recent developments in metabolomics allowed to probe much further the metabolism of cancer, highlighting altered metabolic pathways and offering a new powerful tool to investigate cancer disease. In this review, we discuss the main metabolic alterations of cancer cells and the potentiality of phytochemicals as promising modulators of cancer metabolism. We will focus on the application of nuclear magnetic resonance-based metabolomics on breast and hepatocellular cancer cell lines to evaluate the impact of curcumin and resveratrol on cancer metabolome with the aim to demonstrate the premise of this approach to provide useful information for a better understanding of impact of diet components on cancer disease.

Phosphorylation-mediated activation of LDHA promotes cancer cell invasion and tumour metastasis.

Metastases remain the major cause of death from cancer. Recent molecular advances have highlighted the importance of metabolic alterations in cancer cells, including the Warburg effect that describes an increased glycolysis in cancer cells. However, how this altered metabolism contributes to tumour metastasis remains elusive. Here, we report that phosphorylation-induced activation of lactate dehydrogenase A (LDHA), an enzyme that catalyses the interconversion of pyruvate and lactate, promotes cancer cell invasion, anoikis resistance and tumour metastasis. We demonstrate that LDHA is phosphorylated at tyrosine 10 by upstream kinases, HER2 and Src. Targeting HER2 or Src attenuated LDH activity as well as invasive potential in head and neck cancer and breast cancer cells. Inhibition of LDH activity by small hairpin ribonucleic acid or expression of phospho-deficient LDHA Y10F sensitized the cancer cells to anoikis induction and resulted in attenuated cell invasion and elevated reactive oxygen species, whereas such phenotypes were reversed by its product lactate or antioxidant N-acetylcysteine, suggesting that Y10 phosphorylation-mediated LDHA activity promotes cancer cell invasion and anoikis resistance through redox homeostasis. In addition, LDHA knockdown or LDHA Y10F rescue expression in human cancer cells resulted in decreased tumour metastasis in xenograft mice. Furthermore, LDHA phosphorylation at Y10 positively correlated with progression of metastatic breast cancer in clinical patient tumour samples. Our findings demonstrate that LDHA phosphorylation and activation provide pro-invasive, anti-anoikis and pro-metastatic advantages to cancer cells, suggesting that Y10 phosphorylation of LDHA may represent a promising therapeutic target and a prognostic marker for metastatic human cancers.

Abstract P4-07-05: MicroRNA-27b mediates deregulation of energy metabolism in breast cancer

Abstract MicroRNAs (miRNAs) are a class of small, non-coding RNA which participate in gene regulation by targeted silencing of specific mRNA transcripts. Recently, it has become clear that dysfunctional miRNA expression is an important contributor to the deregulation of key signaling pathways underlying carcinogenesis. MicroRNA-27b is an example of one such pro-oncogenic miRNA, and correspondingly, its expression has been found to be upregulated in breast cancer cells and tissues. In this regard, several targets of miR-27b have previously been verified, and implicate miR-27b in multiple neoplastic processes including migration, invasion and metastasis. In order to enable future development of miRNA-based cancer therapies, the putative targets of each miRNA must be mapped more comprehensively. Such awareness is necessary in order to make informed choices regarding whether a miRNA-based therapy is likely to be effective and what side-effects should be anticipated. Therefore, this project seeks to further establish the role of miR-27b in the context of breast cancer, specifically by identifying novel target transcripts under its control. Using target prediction algorithms and breast cancer cell culture models, initial evidence has implicated Pyruvate Dehydrogenase Protein X (PDHX) to be a probable target. As a structural component of the Pyruvate Dehydrogenase Complex, the role of PDHX in linking the end products of glycolytic reactions with subsequent oxidative phosphorylation pathways is indispensable. However, a hallmark of cancer cell metabolism is the propensity to consume glucose aerobically, which liberates additional carbon skeletons for use in biosynthetic reactions that are crucial for tumor growth. In this way, miR-27b overexpression appears to sever the link between glycolysis and subsequent catabolic pathways, thus conferring a pro-growth advantage to the cancer cells. Expression profiling of PDHX using both breast cancer cell lines and human breast tissues (which overexpress miR-27b) reveal that PDHX levels are indeed significantly reduced, thus supporting the notion that miR-27b alters cancer cell metabolism specifically by targeting this gene in breast cancer. Improving the current understanding of miR-27b's functions will lay the necessary ground work to evaluate its potential as a novel target for cancer therapy. Similarly, the awareness of the expression status of miR-27b and its targets in breast cancer tumors will further efforts to find suitable miRNA tissue biomarkers to enhance screening and prognosis. In this way, microRNA-based approaches offer the distinct potential to improve cancer detection as well as treatment, making them a dynamic method to improve management of breast cancer patients in the future. Citation Format: Eastlack SC, Alahari SK, Dong S, Cole JT. MicroRNA-27b mediates deregulation of energy metabolism in breast cancer [abstract]. In: Proceedings of the 2016 San Antonio Breast Cancer Symposium; 2016 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2017;77(4 Suppl):Abstract nr P4-07-05.

Altered metabolite levels in cancer: implications for tumour biology and cancer therapy.

Altered cell metabolism is a characteristic feature of many cancers. Aside from well-described changes in nutrient consumption and waste excretion, altered cancer cell metabolism also results in changes to intracellular metabolite concentrations. Increased levels of metabolites that result directly from genetic mutations and cancer-associated modifications in protein expression can promote cancer initiation and progression. Changes in the levels of specific metabolites, such as 2-hydroxyglutarate, fumarate, succinate, aspartate and reactive oxygen species, can result in altered cell signalling, enzyme activity and/or metabolic flux. In this Review, we discuss the mechanisms that lead to changes in metabolite concentrations in cancer cells, the consequences of these changes for the cells and how they might be exploited to improve cancer therapy.

Mitochondria, cholesterol and cancer cell metabolism.

Given the role of mitochondria in oxygen consumption, metabolism and cell death regulation, alterations in mitochondrial function or dysregulation of cell death pathways contribute to the genesis and progression of cancer. Cancer cells exhibit an array of metabolic transformations induced by mutations leading to gain-of-function of oncogenes and loss-of-function of tumor suppressor genes that include increased glucose consumption, reduced mitochondrial respiration, increased reactive oxygen species generation and cell death resistance, all of which ensure cancer progression. Cholesterol metabolism is disturbed in cancer cells and supports uncontrolled cell growth. In particular, the accumulation of cholesterol in mitochondria emerges as a molecular component that orchestrates some of these metabolic alterations in cancer cells by impairing mitochondrial function. As a consequence, mitochondrial cholesterol loading in cancer cells may contribute, in part, to the Warburg effect stimulating aerobic glycolysis to meet the energetic demand of proliferating cells, while protecting cancer cells against mitochondrial apoptosis due to changes in mitochondrial membrane dynamics. Further understanding the complexity in the metabolic alterations of cancer cells, mediated largely through alterations in mitochondrial function, may pave the way to identify more efficient strategies for cancer treatment involving the use of small molecules targeting mitochondria, cholesterol homeostasis/trafficking and specific metabolic pathways.