Hypoxia induces a lipogenic cancer cell phenotype via HIF1α-dependent and -independent pathways (original) (raw)
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Cancer Cell Metabolism in Hypoxia: Role of HIF-1 as Key Regulator and Therapeutic Target
International Journal of Molecular Sciences, 2021
In order to meet the high energy demand, a metabolic reprogramming occurs in cancer cells. Its role is crucial in promoting tumor survival. Among the substrates in demand, oxygen is fundamental for bioenergetics. Nevertheless, tumor microenvironment is frequently characterized by low-oxygen conditions. Hypoxia-inducible factor 1 (HIF-1) is a pivotal modulator of the metabolic reprogramming which takes place in hypoxic cancer cells. In the hub of cellular bioenergetics, mitochondria are key players in regulating cellular energy. Therefore, a close crosstalk between mitochondria and HIF-1 underlies the metabolic and functional changes of cancer cells. Noteworthy, HIF-1 represents a promising target for novel cancer therapeutics. In this review, we summarize the molecular mechanisms underlying the interplay between HIF-1 and energetic metabolism, with a focus on mitochondria, of hypoxic cancer cells.
HIF-1-Independent Mechanisms Regulating Metabolic Adaptation in Hypoxic Cancer Cells
Cells, 2021
In solid tumours, cancer cells exist within hypoxic microenvironments, and their metabolic adaptation to this hypoxia is driven by HIF-1 transcription factor, which is overexpressed in a broad range of human cancers. HIF inhibitors are under pre-clinical investigation and clinical trials, but there is evidence that hypoxic cancer cells can adapt metabolically to HIF-1 inhibition, which would provide a potential route for drug resistance. Here, we review accumulating evidence of such adaptions in carbohydrate and creatine metabolism and other HIF-1-independent mechanisms that might allow cancers to survive hypoxia despite anti-HIF-1 therapy. These include pathways in glucose, glutamine, and lipid metabolism; epigenetic mechanisms; post-translational protein modifications; spatial reorganization of enzymes; signalling pathways such as Myc, PI3K-Akt, 2-hyxdroxyglutarate and AMP-activated protein kinase (AMPK); and activation of the HIF-2 pathway. All of these should be investigated in ...
Cell Cycle, 2012
Hypoxia-inducible factor (HIF) 1α and 2α are transcription factors responsible for the cellular response to hypoxia. the functional roles of HIF1α and HIF2α in cancer are distinct and vary among different tumor types. the aim of this study was to evaluate the compartment-specific role(s) of HIF1α and HIF2α in breast cancer. to this end, immortalized human fibroblasts and MDA-MB-231 breast cancer cells carrying constitutively active HIF1α or HIF2α mutants were analyzed with respect to their metabolic function(s) and ability to promote tumor growth in an in vivo setting. We observed that activation of HIF1α, but not HIF2α, in stromal cells promotes a shift toward aerobic glycolysis, with increased L-lactate production and a loss of mitochondrial activity. In a xenograft model, HIF1α-activated fibroblasts promoted the tumor growth of co-injected MDA-MB-231 cells without an increase in angiogenesis. Conversely, HIF2α-activated stromal cells did not favor tumor growth and behaved as the empty vector controls. Similarly, activation of HIF1α, but not HIF2α, in MDA-MB-231 cells promoted a shift toward aerobic glycolysis, with increased glucose uptake and L-lactate production. In contrast, HIF2α activation in cancer cells increased the expression of eGFR, Ras and cyclin D1, which are known markers of tumor growth and cell cycle progression. In a xenograft model, HIF1α activation in MDA-MB-231 cells acted as a tumor suppressor, resulting in an almost 2-fold reduction in tumor mass and volume. Interestingly, HIF2α activation in MDA-MB-231 cells induced a significant ~2-fold-increase in tumor mass and volume. Analysis of mitochondrial activity in these tumor xenografts using CoX (cytochrome C oxidase) staining demonstrated elevated mitochondrial oxidative metabolism (oXpHoS) in HIF2α-tumors. We conclude that the role(s) of HIF1α and HIF2α in tumorigenesis are compartment-specific. HIF1α acts as a tumor promoter in stromal cells but as a tumor suppressor in cancer cells. Conversely, HIF2α is a tumor promoter in cancer cells. Mechanistically, HIF1α-driven aerobic glycolysis in stromal cells supports cancer cell growth via the paracrine production of nutrients (such as L-lactate) that can "feed" cancer cells. However, HIF1α-driven aerobic glycolysis in cancer cells inhibits tumor growth. Finally, HIF2α activation in cancer cells induces the expression of known pro-oncogenic molecules and promotes the mitochondrial activity of cancer cells.
Frontiers in Genetics
Metabolic alterations are one of the hallmarks of cancer, which has recently gained great attention. Increased glucose absorption and lactate secretion in cancer cells are characterized by the Warburg effect, which is caused by the metabolic changes in the tumor tissue. Cancer cells switch from oxidative phosphorylation (OXPHOS) to aerobic glycolysis due to changes in glucose degradation mechanisms, a process known as “metabolic reprogramming”. As a result, proteins involved in mediating the altered metabolic pathways identified in cancer cells pose novel therapeutic targets. Hypoxic tumor microenvironment (HTM) is anticipated to trigger and promote metabolic alterations, oncogene activation, epithelial-mesenchymal transition, and drug resistance, all of which are hallmarks of aggressive cancer behaviour. Angiogenesis, erythropoiesis, glycolysis regulation, glucose transport, acidosis regulators have all been orchestrated through the activation and stability of a transcription facto...
Reversible Inactivation of HIF-1 Prolyl Hydroxylases Allows Cell Metabolism to Control Basal HIF-1
Journal of Biological Chemistry, 2005
Continuous hydroxylation of the HIF-1 transcription factor ␣ subunit by oxygen and 2-oxoglutarate-dependent dioxygenases promotes decay of this protein and thus prevents the transcriptional activation of many genes involved in energy metabolism, angiogenesis, cell survival, and matrix modification. Hypoxia blocks HIF-1␣ hydroxylation and thus activates HIF-1␣-mediated gene expression. Several nonhypoxic stimuli can also activate HIF-1, although the mechanisms involved are not well known. Here we show that the glucose metabolites pyruvate and oxaloacetate inactivate HIF-1␣ decay in a manner selectively reversible by ascorbate, cysteine, histidine, and ferrous iron but not by 2-oxoglutarate or oxygen. Pyruvate and oxaloacetate bind to the 2-oxoglutarate site of HIF-1␣ prolyl hydroxylases, but their effects on HIF-1 are not mimicked by other Krebs cycle intermediates, including succinate and fumarate. We show that inactivation of HIF-1 hydroxylation by glucose-derived 2-oxoacids underlies the prominent basal HIF-1 activity commonly seen in many highly glycolytic cancer cells. Since HIF-1 itself promotes glycolytic metabolism, enhancement of HIF-1 by glucose metabolites may constitute a novel feed-forward signaling mechanism involved in malignant progression.
Molecular Cancer Research, 2019
Hypoxia-inducible factor 1a is a key regulator of the hypoxia response in normal and cancer tissues. It is well recognized to regulate glycolysis and is a target for therapy. However, how tumor cells adapt to grow in the absence of HIF1a is poorly understood and an important concept to understand for developing targeted therapies is the flexibility of the metabolic response to hypoxia via alternative pathways. We analyzed pathways that allow cells to survive hypoxic stress in the absence of HIF1a, using the HCT116 colon cancer cell line with deleted HIF1a versus control. Spheroids were used to provide a 3D model of metabolic gradients. We conducted a metabolomic, transcriptomic, and proteomic analysis and integrated the results. These showed surprisingly that in three-dimensional growth, a key regulatory step of glycolysis is Aldolase A rather than phosphofructokinase. Furthermore, glucose uptake could be maintained in hypoxia through upregulation of GLUT14, not previously recognized in this role. Finally, there was a marked adaptation and change of phosphocreatine energy pathways, which made the cells susceptible to inhibition of creatine metabolism in hypoxic conditions. Overall, our studies show a complex adaptation to hypoxia that can bypass HIF1a, but it is targetable and it provides new insight into the key metabolic pathways involved in cancer growth. Implications: Under hypoxia and HIF1 blockade, cancer cells adapt their energy metabolism via upregulation of the GLUT14 glucose transporter and creatine metabolism providing new avenues for drug targeting.
Drug discovery today, 2018
Hypoxia-inducible factor-1α (HIF-1α) shifts the metabolism of glucose from highly efficient oxidative phosphorylation to less efficient glycolysis. Pyruvic acid thus accumulated is oxidized to lactic acid which is pumped out in the tumor microenvironment. Protons generated from the pentose phosphate pathway (PPP) and upon hydrolysis of ATP further enhance the acidity in the tumor microenvironment. The resultant pH in the tumor microenvironment activates an endoplasmic reticulum protein: sterol regulatory element binding protein-1c (SREBP-1c), which once activated enhances proliferation of the tumor cell. Prolyl hydroxylase 2 (PHD2) is a negative regulator of HIF-1α and causes degradation of HIF-1α in the presence of oxygen. Chemical activation of PHD2 can downregulate HIF-1α and thus restore all its effects. The present review is an attempt to describe PHD2 as the target to combat cancer hypoxia and consequential cellular and metabolic alterations.
The role of hypoxia inducible factor-1 in cell metabolism - a possible target in cancer therapy
Expert Opinion on Therapeutic Targets, 2006
In many cancer types, intratumoural hypoxia is linked to increased expression and activity of the transcription factor hypoxia-inducible factor (HIF-1α), which is associated with poor patient prognosis. This increased the interest in HIF-1α as a cancer drug target. Further, HIF-1α has also a central role in the adaptive cellular programme responding to hypoxia in normal tissues. Many of the HIF-1α-regulated genes encode enzymes of metabolic pathways. Therefore, studying the link and the feedback mechanisms between metabolism and HIF-1α is of major importance to find new and specific therapeutic strategies.
Reactivating HIF prolyl hydroxylases under hypoxia results in metabolic catastrophe and cell death
Oncogene, 2009
Cells exposed to low-oxygen conditions (hypoxia) alter their metabolism to survive. This response, although vital during development and high-altitude survival, is now known to be a major factor in the selection of cells with a transformed metabolic phenotype during tumorigenesis. It is thought that hypoxia-selected cells have increased invasive capacity and resistance to both chemo-and radiotherapies, and therefore represent an attractive target for antitumor therapy. Hypoxia inducible factors (HIFs) are responsible for the majority of gene expression changes under hypoxia, and are themselves controlled by the oxygen-sensing HIF prolyl hydroxylases (PHDs). It was previously shown that mutations in succinate dehydrogenase lead to the inactivation PHDs under normoxic conditions, which can be overcome by treatment with a-ketoglutarate derivatives. Given that solid tumors contain large regions of hypoxia, the reactivation of PHDs in these conditions could induce metabolic catastrophe and therefore prove an effective antitumor therapy. In this report we demonstrate that derivatized a-ketoglutarate can be used as a strategy for maintaining PHD activity under hypoxia. By increasing intracellular a-ketoglutarate and activating PHDs we trigger PHD-dependent reversal of HIF1 activation, and PHD-dependent hypoxic cell death. We also show that derivatized a-ketoglutarate can permeate multiple layers of cells, reducing HIF1a levels and its target genes in vivo.