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Hypoxia and cancer cell metabolism
Abstract and Figures
The past decade has witnessed a rapid accumulation of evidence showing that hypoxic microenvironment, which is typical during cancer development, plays key roles in regulating cancer cell metabolism. In this review, we will focus on the role of hypoxic response, particularly, its master regulator hypoxia-inducible factor-1, in regulating glucose, lipid, as well as amino acid metabolism in cancer cells. We will also discuss the therapeutic opportunities by targeting specific pathways that facilitate metabolic reprogramming in cancer cells.
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... Several enzymes of the glycolytic pathway, including glucose transporter 1 (GLUT1), glucose transporter 3 (GLUT3), HK1, HK2, glyceraldehyde-3-phosphate dehydrogenase (GAPDH), phosphoglycerate kinase 1 (PGK1), PKM2, LDH-A, and 3-phosphoinositide-dependent kinase 1 (PDK1), are activated by HIF-1A. Moreover, HIF-1 stimulates glucose absorption and lactate production by inhibiting the TCA cycle and oxidative phosphorylation in the mitochondria [59,60] (Figure 3). The most often dysregulated mechanism in cancer is PI3K signaling, which promotes growth, proliferation, and survival. ...
... The master regulator and tumor-suppressor p53 decrease glucose absorption in cells by downregulating GLUT1 and GLUT4 expression in cancer cells. Hence, it plays a vital role in suppressing glycolysis under normoxic or hypoxic conditions via its transcriptional target genes [59,60]. The DNA Binding Domain (DBD) especially the amino acid residues 98-293, which is located in exons 5, 6, 7, part of exons 4, and 8 of p53, contains the majority of the high-frequency oncogenic mutations, as well as an aggregation-prone region (APR), and has been proven in multiple studies to be a useful model system to emulate the behavior of full-length p53, including aggregation [61,62]. ...
Simple Summary: Deregulated cellular metabolism is one of the major hallmarks of cancer. Cancer cells orchestrate abnormal metabolic reprogramming to satisfy high energy demands. The review focuses on the mechanics of the major metabolic pathways, significant intermediates, and associated enzymes that are altered by the oncogenic progression. The emphasis is laid on therapeutically targeting clinically relevant metabolic intermediates which are crucial to cancer cell survival, and proliferation. The clinical intervention of metabolic pathways, critical enzymes, and the intermediate, thus offers a distinct niche in cancer therapies. Abstract: Metabolic reprogramming enables cancer cells to proliferate and produce tumor biomass under a nutrient-deficient microenvironment and the stress of metabolic waste. A cancer cell adeptly undergoes a variety of adaptations in metabolic pathways and differential expression of metabolic enzyme genes. Metabolic adaptation is mainly determined by the physiological demands of the cancer cell of origin and the host tissue. Numerous metabolic regulators that assist cancer cell proliferation include uncontrolled anabolism/catabolism of glucose metabolism, fatty acids, amino acids metabolism, nucleotide metabolism, tumor suppressor genes, microRNAs, and many regulatory enzymes and genes. Using this paradigm, we review the current understanding of metabolic reprogramming in tumors and discuss the new strategies of cancer metabolomics that can be tapped into for cancer therapeutics.
... Cancer cells boost glycolytic gene expression and glucose transporter production to offset ATP loss. Hypoxia-inducible Factor 1 (HIF-1), a key regulator activated by the PI3K/Akt/ mTOR pathway, orchestrates metabolic reprogramming in response to hypoxia [29]. The PI3K-dependent pathway governs cell growth and glucose metabolism. ...
... Acute hypoxia within the tumor is typically caused by temporary lack or restriction of the blood supply (Butturini et al., 2019;Bristow and Hill, 2008). Cancer cells induce hypoxia by mechanisms such as high metabolic rate and oxygen consumption, which can damage blood vessels and cause endothelial dysfunction (Bristow and Hill, 2008;Huang et al., 2014;Hernansanz-Agustín et al., 2020). Chronic hypoxia activates the hypoxia inducible factor (HIF) signaling pathway, which speeds up tumor expansion, enhances its ability to invade, and facilitates metastasis (Wigerup et al., 2016). ...
... Hypoxia activates vascular endothelial cells, stimulates tumor angiogenesis, and promotes tumor growth and metastasis [160,161]. More importantly, the hypoxic response triggers the "angiogenic switch" and promotes metabolic reprogramming in tumors [66,162]. Evidence suggests that tumors can adapt to these hypoxic environments by reprogramming cholesterol metabolism to enhance tumor stemness and angiogenesis, which promotes their survival and growth. ...
Cholesterol is crucial for cell survival and growth, and dysregulation of cholesterol homeostasis has been linked to the development of cancer. The tumor microenvironment (TME) facilitates tumor cell survival and growth, and crosstalk between cholesterol metabolism and the TME contributes to tumorigenesis and tumor progression. Targeting cholesterol metabolism has demonstrated significant antitumor effects in preclinical and clinical studies. In this review, we discuss the regulatory mechanisms of cholesterol homeostasis and the impact of its dysregulation on the hallmarks of cancer. We also describe how cholesterol metabolism reprograms the TME across seven specialized microenvironments. Furthermore, we discuss the potential of targeting cholesterol metabolism as a therapeutic strategy for tumors. This approach not only exerts antitumor effects in monotherapy and combination therapy but also mitigates the adverse effects associated with conventional tumor therapy. Finally, we outline the unresolved questions and suggest potential avenues for future investigations on cholesterol metabolism in relation to cancer.
... In order to meet the high energy requirements for their rapid proliferation, tumor cells shift their energy metabolic pathways to glycolysis that can be rapidly energized. This condition is a cellular shift from mitochondrial respiration to glycolysis-dependent metabolism, which is mainly accompanied by an increase of lactate production and glucose uptake (Huang et al. 2014). The dependence of tumor cells on glycolysis is further exacerbated under hypoxia conditions. ...
Hypoxia is one of the hallmarks of solid tumors, especially in hepatocellular carcinoma (HCC). CircRNAs are reported to be tightly connected to hypoxia and also have essential roles in cancer progression. However, many circRNAs implicated in hypoxia-mediated HCC progression are still unclear and require further exploration. In this study, a hypoxia cell model was structured by exposing cells to hypoxia conditions (1% O2) and normoxia conditions (21% O2) as a control. The effects of hypoxia and normoxia on cell viability, migration, invasion, and glycolysis were examined. The expressions of circRNARTN4IP1 under hypoxia were identified. Finally, molecular mechanisms and biological function of circRTN4IP1 were explored. We confirmed that hypoxia treatment facilitated capacities of proliferation, migration, invasion, and glycolysis in tumor cells. Hypoxia induced a significant increase expression of circRTN4IP1 in cells. Functionally, knockdown of circRTN4IP1 inhibited cell malignant progression and glycolysis under hypoxia HCC cells. Mechanistically, HIF1A targeted the promoter region of circRTN4IP1 and positively regulated the expression of circRTN4IP1. In addition, circRTN4IP1 targeted miR-532-5p/G6PC3 axis. In short, hypoxia induced activation of the HIF1A/circRTN4IP1/miR-532-5p/G6PC3 signaling axis, which promoted proliferation, migration, invasion, and glycolysis of HCC cells. This study may reveal a possible mechanism driving the progression of hypoxia HCC, so as to find potential effective candidates for targeting hypoxia microenvironment therapy.
Graphical abstract
... The widely known fact that chronic inflammation creates prerequisites for the development of malignant tumors [48,39,[50][51][52] and supports tumor progression [53,54] is not just a hypothesis, but a theoretically and experimentally confirmed model that has recently been emphasized not only by clinicians but also by pharmacologists [55]. Among the factors that mediate inflammation are oxidative stress [56,57] and hypoxia [53,58,59], microbiome alterations [48,[60][61][62] and oncogenic viruses [51,63,64], immune disorders [65][66][67] and pathological aging [68][69][70], and lifestyle features, including diet, physical activity, and chronic emotional stress [71][72][73][74][75]. Most of these factors have their own mechanisms of influence on the tumor development outside the inflammation model. ...
... With the continuous exploration of tumorigenesis mechanisms, how changes in cancer cell metabolic pathways affect development and progress of cancer has become a research hotspot 8 . There is a lot of evidence that mutation of many genes regulate tumorigenesis by affecting glucose metabolism pathways, such as HIF-1 and PDK1, which are also known as metabolic-related genes (MRGs) 9,10 . Cancer cells also need to use lipid metabolism to obtain energy and key biomolecules for survival and metastatic 11 . ...
Skin cutaneous melanoma (SKCM) is a fatal form of skin cancer. Metabolic-related genes (MRGs) are a set of genes which can mediate and control all of metabolic related pathways. In this study, the expression levels of MRGs were used to classify all patients into three molecular subtypes. Then the differentially expressed genes (DEGs) among the three MRGs molecular clusters were applied into the LASSO and COX regression analysis to identify five signature genes. Moreover, we constructed a prognostic model for forecasting the prognosis of SKCM and assess the response of the SKCM patients to immunotherapy according to the signature genes. Single-cell RNA-sequencing analyses are used to explore the expression of the five signature genes in immune or non-immune cells. Notably, different expression levels of the signature genes between normal melanocytes and SKCM cells were determined using in vitro experiments including western blot (WB), quantitative PCR (qPCR) and immunohistochemical (IHC) methods. In addition, silencing the expression of SLC5A3 in SKCM cells using small interfering RNAs (siRNAs) would inhibit the proliferation and migration of cells which could be observed by the EdU Fluorescence Labeling, CCK8 and cell transfection methods.
Rationale
Multicellular tumor spheroids (MCTSs) that reconstitute the metabolic characteristics of in vivo tumor tissue may facilitate the discovery of molecular biomarkers and effective anticancer therapies. However, little is known about how cancer cells adapt their metabolic changes in complex three‐dimensional (3D) microenvironments. Here, using the two‐dimensional (2D) cell model as control, the metabolic phenotypes of glioma U87MG multicellular tumor spheroids were systematically investigated based on static metabolomics and dynamic fluxomics analysis.
Methods
A liquid chromatography–mass spectrometry‐based global metabolomics and lipidomics approach was adopted to survey the cellular samples from 2D and 3D culture systems, revealing marked molecular differences between them. Then, by means of metabolomic pathway analysis, the metabolic pathways altered in glioma MCTSs were found using ¹³ C 6 ‐glucose as a tracer to map the metabolic flux of glycolysis, the tricarboxylic acid (TCA) cycle, de novo nucleotide synthesis, and de novo lipid biosynthesis in the MCTS model.
Results
We found nine metabolic pathways as well as glycerolipid, glycerophospholipid and sphingolipid metabolism to be predominantly altered in glioma MCTSs. The reduced nucleotide metabolism, amino acid metabolism and glutathione metabolism indicated an overall lower cellular activity in MCTSs. Through dynamic fluxomics analysis in the MCTS model, we found that cells cultured in MCTSs exhibited increased glycolysis activity and de novo lipid biosynthesis activity, and decreased the TCA cycle and de novo purine nucleotide biosynthesis activity.
Conclusions
Our study highlights specific, altered biochemical pathways in MCTSs, emphasizing dysregulation of energy metabolism and lipid metabolism, and offering novel insight into metabolic events in glioma MCTSs.
Hypoxia is defined as the inadequate supply of oxygen to the tissue that can occur due to a multitude of causes and is called by various names such as hypoxemic, anemic, ischemic, diffusional, and cytotoxic hypoxia. Cancer-induced hypoxia is an interplay of ischemic, diffusional, and anemic hypoxia, and plays an important role as a prognosticator of the disease and also as a target for treatment modalities. The major mediator of hypoxia in tumor cells is hypoxia-inducible factor (HIF), which is a heterodimeric protein that is upregulated in hypoxic conditions. The consequences of HIF action are the activation and upregulation of several enzymes, transporters, and factors that modulate the neoplastic cell’s metabolic functions that result in functional responses to the hypoxic stressor, which resists apoptosis/necrosis, in addition to modifying and refashioning the local microenvironment to suit the neoplastic cell’s survival. Metastasis—one of the most feared outcomes of neoplasm—has almost all of its steps upregulated or controlled by hypoxia and HIF. Hypoxia is also responsible for drug resistance to various chemotherapeutic agents by different mechanisms. This makes it harder to treat neoplasms that are susceptible to these drugs. Therefore, treatment modalities acting by blocking HIF, in addition to the standard chemotherapeutics, target the neoplasm from all aspects, making it more comprehensive and more effective.KeywordsHypoxiaHIFCancerTumorChemotherapyTumor metastasisChemo-resistance
Altered metabolism has become an emerging feature of cancer cells impacting their proliferation and metastatic potential in myriad ways. Proliferating heterogeneous tumor cells are surrounded by other resident or infiltrating cells, along with extracellular matrix proteins, and other secretory factors constituting the tumor microenvironment. The diverse cell types of the tumor microenvironment exhibit different molecular signatures that are regulated at their genetic and epigenetic levels. The cancer cells elicit intricate crosstalks with these supporting cells, exchanging essential metabolites which support their anabolic processes and can promote their survival, proliferation, EMT, angiogenesis, metastasis and even therapeutic resistance. In this context, carbohydrate metabolism ensures constant energy supply being a central axis from which other metabolic and biosynthetic pathways including amino acid and lipid metabolism and pentose phosphate pathway are diverged. In contrast to normal cells, increased glycolytic flux is a distinguishing feature of the highly proliferative cancer cells, which supports them to adapt to a hypoxic environment and also protects them from oxidative stress. Such rewired metabolic properties are often a result of epigenetic alterations in the cancer cells, which are mediated by several factors including, DNA, histone and non-histone protein modifications and non-coding RNAs. Conversely, epigenetic landscapes of the cancer cells are also dictated by their diverse metabolomes. Altogether, this metabolic and epigenetic interplay has immense potential for the development of efficient anti-cancer therapeutic strategies. In this book chapter we emphasize upon the significance of reprogrammed carbohydrate metabolism in regulating the tumor microenvironment and cancer progression, with an aim to explore the different metabolic and epigenetic targets for better cancer treatment.
Hypoxia-inducible factor 1 (HIF-1) activates erythropoietin gene transcription in Hep3B cells subjected to hypoxia. HIF-1 activity is also induced by hypoxia in non-erythropoietin-producing cells, suggesting a more general regulatory role. We now report that RNAs encoding the glycolytic enzymes aldolase A (ALDA), phosphoglycerate kinase 1 (PGK1), and pyruvate kinase M were induced by exposure of Hep3B or HeLa cells to inducers of HIF-1 (1% O2, cobalt chloride, or desferrioxamine), whereas cycloheximide blocked induction of glycolytic RNAs and HIF-1 activity. Oligonucleotides from the ALDA, PGK1, enolase 1, lactate dehydrogenase A, and phosphofructokinase L (PFKL) genes, containing sequences similar to the HIF-1 binding site in the erythropoietin enhancer, specifically bound HIF-1 present in crude nuclear extracts or affinity-purified preparations. Sequences from the ALDA, PFKL, and PGK1 genes containing HIF-1 binding sites mediated hypoxia-inducible transcription in transient expression assays. These results support the role of HIF-1 as a mediator of adaptive responses to hypoxia that underlie cellular and systemic oxygen homeostasis.
The mechanisms of compromised mitochondrial function under various pathological conditions, including hypoxia, remain largely unknown. Recent studies have shown that microRNA-210 (miR-210) is induced by hypoxia under the regulation of hypoxia-inducible factor-1α and has an important role in cell survival under hypoxic microenvironment. Hence, we hypothesized that miR-210 has a role in regulating mitochondrial metabolism and investigated miR-210 effects on mitochondrial function in cancer cell lines under normal and hypoxic conditions. Our results demonstrate that miR-210 decreases mitochondrial function and upregulates the glycolysis, thus make cancer cells more sensitive to glycolysis inhibitor. miR-210 can also activate the generation of reactive oxygen species (ROS). ISCU (iron-sulfur cluster scaffold homolog) and COX10 (cytochrome c oxidase assembly protein), two important factors of the mitochondria electron transport chain and the tricarboxylic acid cycle have been identified as potential targets of miR-210. The unique means by which miR-210 regulates mitochondrial function reveals an miRNA-mediated link between microenvironmental stress, oxidative phosphorylation, ROS and iron homeostasis.
We have identified a 50-nucleotide enhancer from the human erythropoietin gene 3'-flanking sequence which can mediate a sevenfold transcriptional induction in response to hypoxia when cloned 3' to a simian virus 40 promoter-chloramphenicol acetyltransferase reporter gene and transiently expressed in Hep3B cells. Nucleotides (nt) 1 to 33 of this sequence mediate sevenfold induction of reporter gene expression when present in two tandem copies compared with threefold induction when present in a single copy, suggesting that nt 34 to 50 bind a factor which amplifies the induction signal. DNase I footprinting demonstrated binding of a constitutive nuclear factor to nt 26 to 48. Mutagenesis studies revealed that nt 4 to 12 and 19 to 23 are essential for induction, as substitutions at either site eliminated hypoxia-induced expression. Electrophoretic mobility shift assays identified a nuclear factor which bound to a probe spanning nt 1 to 18 but not to a probe containing a mutation which eliminated enhancer function. Factor binding was induced by hypoxia, and its induction was sensitive to cycloheximide treatment. We have thus defined a functionally tripartite, 50-nt hypoxia-inducible enhancer which binds several nuclear factors, one of which is induced by hypoxia via de novo protein synthesis.
There is considerable interest in identifying nontoxic differentiation inducers for the treatment of various malignant and nonmalignant blood disorders, including inborn beta-chain hemoglobinopathies. Using the human leukemic K562 cell line as a model, we explored the efficacy of phenylacetate, an amino acid derivative with a low toxicity index when administered to humans. Treatment of K562 cultures with pharmacologically attainable concentrations of phenylacetate resulted in erythroid differentiation, evident by the reduced growth rate and increased hemoglobin production. The effect was time- and dose- dependent, further augmented by glutamine starvation (phenylacetate is known to deplete circulating glutamine in vivo), and reversible upon cessation of treatment. Molecular analysis showed that phenylacetate induced gamma globin gene expression with subsequent accumulation of the fetal form of hemoglobin (HbF). Interestingly, the addition of phenylacetate to antitumor agents of clinical interest, eg, hydroxyurea and 5-azacytidine, caused superinduction of HbF biosynthesis. The results suggest that phenylacetate, used alone or in combination with other drugs, might offer a safe and effective new approach to treatment of some hematopoietic neoplasms and severe hemoglobinopathies.
Abstract
We determined the contribution from host hepatic and extrahepatic tissues to newly synthesized fatty acids (FA) in the Ehrlich ascites tumor (EAT). We administered 3H2O (subcutaneously) and [14C]glucose (in a test meal) and measured the appearance of radioactivity in plasma triglyceride fatty acids (TGFA) and free fatty acids (FFA) and in tumor total lipid fatty acids (TLFA). Using [14 C]FFA, we selectively labeled epididymal fat TGFA to estimate the FA transport rate from intraperitoneal adipose tissue directly to the tumor. Contributions of four major pathways to newly synthesized FA in EAT were determined by multicompartmental analysis. De novo FA synthesis by EAT accounted for more than 93% of the TLFA radioactivity found in the tumor. Contributions from liver TGFA via plasma TGFA (less than 0.5%), adipose tissue TGFA via plasma FFA (less than 6%), and adipose tissue TGFA via direct intraperitoneal transport of FFA (less than 1%) accounted for less than 7% of all TLFA radioactivity measured in the EAT. Thus the present study establishes that practically all labeled esterified FA in the EAT is derived from de novo synthesis by tumor cells.
Hypoxia plays critical roles in the pathobiology of heart disease, cancer, stroke, and chronic lung disease, which are responsible for 60% of deaths in the United States. This review summarizes advances in our un derstanding of how cells sense and respond to changes in oxygen availability and the physiologic or pathologic consequences of these responses in the context of chronic diseases. The role of hypoxia in inflammatory disorders was recently reviewed in the Journal 1 and is therefore not discussed here. M e ch a nis m s of Signa l T r a nsduc t ion i n H y p ox i a Humans have evolved complex circulatory, respiratory, and neuroendocrine systems to ensure that oxygen levels are precisely maintained, since an excess or deficiency may result in the death of cells, tissue, or the organism. As discussed below, oxygen homeostasis represents an organizing principle for understanding evolution, devel opment, physiology, and disease. Historically, oxygen sensing was thought to be limited to specialized cells, such as the glomus cells of the carotid body, which depo larize within milliseconds in response to hypoxemia by means of incompletely understood mechanisms. 2 We now recognize that all nucleated cells in the body sense and respond to hypoxia. Under conditions of reduced oxygen availability, hypoxia-inducible factor 1 (HIF-1) regulates the expression of genes that mediate adaptive responses. 3-6 In hypoxic cells, the transcription of several hundred messenger RNAs (mRNAs) is increased, and the expression of an equal number of mRNAs is decreased. The changes are dependent on HIF-1 in both cases, but HIF-1 binding is detected only at genes with increased expression. HIF-1 decreases mRNA expression indirectly by regulating transcriptional repressors and microRNAs. 3-6 HIF-1 was first identified in human cells as a regulator of erythropoietin, the hor