Beclin-1 expression is a predictor of clinical outcome in patients with esophageal squamous cell carcinoma and correlated to hypoxia-inducible factor (HIF)-1alpha expression.
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ABSTRACT:
SUBMITTER: Chen Y
PROVIDER: S-EPMC2791489 | biostudies-other | 2009 Sep
REPOSITORIES: biostudies-other
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Project description:Hypoxia-inducible factor (HIF) controls an extensive range of adaptive responses to hypoxia. To better understand this transcriptional cascade we performed genome-wide chromatin immunoprecipitation using antibodies to two major HIF-alpha subunits, and correlated the results with genome-wide transcript profiling. Within a tiled promoter array we identified 546 and 143 sequences that bound, respectively, to HIF-1alpha or HIF-2alpha at high stringency. Analysis of these sequences confirmed an identical core binding motif for HIF-1alpha and HIF-2alpha (RCGTG) but demonstrated that binding to this motif was highly selective, with binding enriched at distinct regions both upstream and downstream of the transcriptional start. Comparison of HIF-promoter binding data with bidirectional HIF-dependent changes in transcript expression indicated that whereas a substantial proportion of positive responses (>20% across all significantly regulated genes) are direct, HIF-dependent gene suppression is almost entirely indirect. Comparison of HIF-1alpha- versus HIF-2alpha-binding sites revealed that whereas some loci bound HIF-1alpha in isolation, many bound both isoforms with similar affinity. Despite high-affinity binding to multiple promoters, HIF-2alpha contributed to few, if any, of the transcriptional responses to acute hypoxia at these loci. Given emerging evidence for biologically distinct functions of HIF-1alpha versus HIF-2alpha understanding the mechanisms restricting HIF-2alpha activity will be of interest.
| S-EPMC2719312 | biostudies-literature
Project description:Transcriptional responses to hypoxia are primarily mediated by hypoxia-inducible factor (HIF), a heterodimer of HIF-alpha and the aryl hydrocarbon receptor nuclear translocator subunits. The HIF-1alpha and HIF-2alpha subunits are structurally similar in their DNA binding and dimerization domains but differ in their transactivation domains, implying they may have unique target genes. Previous studies using Hif-1alpha(-/-) embryonic stem and mouse embryonic fibroblast cells show that loss of HIF-1alpha eliminates all oxygen-regulated transcriptional responses analyzed, suggesting that HIF-2alpha is dispensable for hypoxic gene regulation. In contrast, HIF-2alpha has been shown to regulate some hypoxia-inducible genes in transient transfection assays and during embryonic development in the lung and other tissues. To address this discrepancy, and to identify specific HIF-2alpha target genes, we used DNA microarray analysis to evaluate hypoxic gene induction in cells expressing HIF-2alpha but not HIF-1alpha. In addition, we engineered HEK293 cells to express stabilized forms of HIF-1alpha or HIF-2alpha via a tetracycline-regulated promoter. In this first comparative study of HIF-1alpha and HIF-2alpha target genes, we demonstrate that HIF-2alpha does regulate a variety of broadly expressed hypoxia-inducible genes, suggesting that its function is not restricted, as initially thought, to endothelial cell-specific gene expression. Importantly, HIF-1alpha (and not HIF-2alpha) stimulates glycolytic gene expression in both types of cells, clearly showing for the first time that HIF-1alpha and HIF-2alpha have unique targets.
| S-EPMC309606 | biostudies-literature
Project description:ObjectiveDiabetic impaired angiogenesis is associated with impairment of hypoxia-inducible factor-1alpha (HIF-1alpha) as well as vasculature maturation. We investigated the potential roles and intracellular mechanisms of angiopoietin-1 (Ang-1) gene therapy on myocardial HIF-1alpha stabilization and vascular maturation in db/db mice.Research design and methodsdb/db mice were systemically administrated adenovirus Ang-1 (Ad-CMV-Ang-1). Myocardial HIF-1alpha, vascular endothelial growth factor (VEGF), hemeoxygenase-1 (HO-1), endothelial nitric oxide synthase (eNOS), Akt, and HIF-1alpha-prolyl-4-hydroxylase-2 (PHD)2 expression were measured. Vasculature maturation, capillary and arteriole densities, and cardiac interstitial fibrosis were analyzed in the border zone of infarcted myocardium.ResultsSystemic administration of Ad-CMV-Ang-1 results in overexpression of Ang-1 in db/db mice hearts. Ang-1 gene therapy causes a significant increase in Akt and eNOS expression and HIF-1alpha stabilization. This is accompanied by a significant upregulation of VEGF and HO-1 expression. Intriguingly, Ang-1 gene therapy also leads to a significant inhibition of PHD2 expression. Smooth muscle recruitment and smooth muscle coverage in the neovessels of the border zone of infarcted myocardium are severely impaired in db/db mice compared with wild-type mice. Ang-1 gene therapy rescues these abnormalities, which leads to a dramatic increase in capillary and arteriole densities and a significant reduction of cardiac hypertrophy and interstitial fibrosis at 14 days after ischemia. Taken together, our data show that Ang-1 increases myocardial vascular maturation and angiogenesis together with suppression of PHD2 and the upregulation of HIF-1alpha signaling.ConclusionsNormalization of immature vasculature by Ang-1 gene therapy may represent a novel therapeutic strategy for treatment of the diabetes-associated impairment of myocardial angiogenesis.
| S-EPMC2584141 | biostudies-literature
Project description:Hypoxia-inducible factor-1alpha (HIF-1alpha), a transcription factor, plays a critical role in adaption to hypoxia, which is a major feature of diseases, including cancer. Protein disulfide isomerase (PDI) is up-regulated in numerous cancers and leads to cancer progression. PDI, a member of the TRX superfamily, regulates the transcriptional activities of several transcription factors. To investigate the mechanisms by which PDI affects the function of HIF-1alpha, the overexpression or knockdown of PDI was performed. The overexpression of PDI decreased HIF-1alpha expression in the human hepatocarcinoma cell line, Hep3B, whereas the knockdown of endogenous PDI increased its expression. NH4Cl inhibited the decrease in HIF-1alpha expression by PDI overexpression, suggesting that HIF-1alpha was degraded by the lysosomal pathway. HIF-1alpha is transferred to lysosomal membranes by heat shock cognate 70 kDa protein (HSC70). The knockdown of HSC70 abolished the decrease, and PDI facilitated the interaction between HIF-1alpha and HSC70. HIF-1alpha directly interacted with PDI. PDI exists not only in the endoplasmic reticulum (ER), but also in the cytosol. Hypoxia increased cytosolic PDI. We also investigated changes in the redox state of HIF-1alpha using PEG-maleimide, which binds to thiols synthesized from disulfide bonds by reduction. An up-shift in the HIF-1alpha band by the overexpression of PDI was detected, suggesting that PDI formed disulfide bond in HIF-1alpha. HIF-1alpha oxidized by PDI was not degraded in HSC70-knockdown cells, indicating that the formation of disulfide bond in HIF-1alpha was important for decreases in HIF-1alpha expression. To the best of our knowledge, this is the first study to show the regulation of the expression and redox state of HIF-1alpha by PDI. We also demonstrated that PDI formed disulfide bonds in HIF-1alpha 1-245 aa and decreased its expression. In conclusion, the present results showed that PDI is a novel factor regulating HIF-1alpha through lysosome-dependent degradation by changes in its redox state.
| S-EPMC7861413 | biostudies-literature
Project description:BACKGROUND: Hypoxia-inducible factor 1 (HIF-1) is a master transcriptional regulator of genes regulating oxygen homeostasis. The HIF-1 protein is composed of two HIF-1alpha and HIF-1beta/aryl hydrocarbon receptor nuclear translocator (ARNT) subunits. The prognostic relevance of HIF-1alpha protein overexpression has been shown in breast cancer. The impact of HIF-1alpha alternative splice variant expression on breast cancer prognosis in terms of metastasis risk is not well known. METHODS: Using real-time quantitative reverse transcription PCR assays, we measured mRNA concentrations of total HIF-1alpha and 4 variants in breast tissue specimens in a series of 29 normal tissues or benign lesions (normal/benign) and 53 primary carcinomas. In breast cancers HIF-1alpha splice variant levels were compared to clinicopathological parameters including tumour microvessel density and metastasis-free survival. RESULTS: HIF-1alpha isoforms containing a three base pairs TAG insertion between exon 1 and exon 2 (designated HIF-1alphaTAG) and HIF-1alpha736 mRNAs were found expressed at higher levels in oestrogen receptor (OR)-negative carcinomas compared to normal/benign tissues (P = 0.009 and P = 0.004 respectively). In breast carcinoma specimens, lymph node status was significantly associated with HIF-1alphaTAG mRNA levels (P = 0.037). Significant statistical association was found between tumour grade and HIF-1alphaTAG (P = 0.048), and total HIF-1alpha (P = 0.048) mRNA levels. HIF-1alphaTAG mRNA levels were also inversely correlated with both oestrogen and progesterone receptor status (P = 0.005 and P = 0.033 respectively). Univariate analysis showed that high HIF-1alphaTAG mRNA levels correlated with shortened metastasis free survival (P = 0.01). CONCLUSIONS: Our results show for the first time that mRNA expression of a HIF-1alphaTAG splice variant reflects a stage of breast cancer progression and is associated with a worse prognosis.See commentary: http://www.biomedcentral.com/1741-7015/8/45.
| S-EPMC2917392 | biostudies-literature
Project description:Hypoxia-inducible factor (HIF) is a heterodimeric transcription factor that is composed of a hypoxia-inducible alpha subunit (HIF-1alpha and HIF-2alpha) and a constitutively expressed beta subunit (HIF-1beta). HIF mediates the adaptation of cells and tissues to low oxygen concentrations. It also plays an important role in tumorigenesis and constitutes an important therapeutic target in anti-tumor therapy. We have screened a number of reported HIF inhibitors for their effects on HIF-transcriptional activity and found that the DNA damage inducing agents camptothecin and mitomycin C produced the most robust effects. Camptothecin is a reported inhibitor of HIF-1alpha translation, while mitomycin C has been reported to induce p53-dependent HIF-1alpha degradation. In this study we demonstrate that the inhibitory effect of mitomycin C on HIF-1alpha protein expression is not dependent on p53 and protein degradation, but also involves HIF-1alpha translational regulation. Initiation of a DNA damage response with the small molecule p53 activator NSC-652287 (RITA) has been reported to inhibit HIF-1alpha protein synthesis by increasing the phosphorylation of eIF2alpha. However, we show here that even when eIF2alpha phosphorylation is prevented, the DNA damage inducing drugs mitomycin C, camptothecin and NSC-652287 still inhibit HIF-1alpha protein synthesis to the same extent. The inhibitory effects of camptothecin on HIF-1alpha expression but not that of mitomycin C and NSC-652287 were dependent on cyclin-dependent kinase activity. In conclusion, specific types of DNA damage can bring about selective inhibition of HIF-1alpha protein synthesis. Further characterization of the involved mechanisms may reveal important novel therapeutic targets.
| S-EPMC2866540 | biostudies-literature
Project description:Hypoxia-inducible factor 1 (HIF-1) is a transcriptional activator composed of HIF-1alpha and HIF-1beta subunits. Several dozen HIF-1 targets are known, including the gene encoding vascular endothelial growth factor (VEGF). Under hypoxic conditions, HIF-1alpha expression increases as a result of decreased ubiquitination and degradation. The tumor suppressors VHL (von Hippel-Lindau protein) and p53 target HIF-1alpha for ubiquitination such that their inactivation in tumor cells increases the half-life of HIF-1alpha. Increased phosphatidylinositol 3-kinase (PI3K) and AKT or decreased PTEN activity in prostate cancer cells also increases HIF-1alpha expression by an undefined mechanism. In breast cancer, increased activity of the HER2 (also known as neu) receptor tyrosine kinase is associated with increased tumor grade, chemotherapy resistance, and decreased patient survival. HER2 has also been implicated as an inducer of VEGF expression. Here we demonstrate that HER2 signaling induced by overexpression in mouse 3T3 cells or heregulin stimulation of human MCF-7 breast cancer cells results in increased HIF-1alpha protein and VEGF mRNA expression that is dependent upon activity of PI3K, AKT (also known as protein kinase B), and the downstream kinase FRAP (FKBP-rapamycin-associated protein). In contrast to other inducers of HIF-1 expression, heregulin stimulation does not affect the half-life of HIF-1alpha but instead stimulates HIF-1alpha synthesis in a rapamycin-dependent manner. The 5'-untranslated region of HIF-1alpha mRNA directs heregulin-inducible expression of a heterologous protein. These data provide a molecular basis for VEGF induction and tumor angiogenesis by heregulin-HER2 signaling and establish a novel mechanism for the regulation of HIF-1alpha expression.
| S-EPMC87062 | biostudies-literature
Project description:Mitochondrial transport is critical for maintenance of normal neuronal function. Here, we identify a novel mitochondria protein, hypoxia up-regulated mitochondrial movement regulator (HUMMR), which is expressed in neurons and is markedly induced by hypoxia-inducible factor 1 alpha (HIF-1alpha). Interestingly, HUMMR interacts with Miro-1 and Miro-2, mitochondrial proteins that are critical for mediating mitochondrial transport. Interestingly, knockdown of HUMMR or HIF-1 function in neurons exposed to hypoxia markedly reduces mitochondrial content in axons. Because mitochondrial transport and distribution are inextricably linked, the impact of reduced HUMMR function on the direction of mitochondrial transport was also explored. Loss of HUMMR function in hypoxia diminished the percentage of motile mitochondria moving in the anterograde direction and enhanced the percentage moving in the retrograde direction. Thus, HUMMR, a novel mitochondrial protein induced by HIF-1 and hypoxia, biases mitochondria transport in the anterograde direction. These findings have broad implications for maintenance of neuronal viability and function during physiological and pathological states.
| S-EPMC2711615 | biostudies-literature
Project description:The hypoxic response in humans is regulated by the hypoxia-inducible transcription factor system; inhibition of hypoxia-inducible factor (HIF) activity has potential for the treatment of cancer. Chetomin, a member of the epidithiodiketopiperazine (ETP) family of natural products, inhibits the interaction between HIF-alpha and the transcriptional coactivator p300. Structure-activity studies employing both natural and synthetic ETP derivatives reveal that only the structurally unique ETP core is required and sufficient to block the interaction of HIF-1alpha and p300. In support of both cell-based and animal work showing that the cytotoxic effect of ETPs is reduced by the addition of Zn(2+) through an unknown mechanism, our mechanistic studies reveal that ETPs react with p300, causing zinc ion ejection. Cell studies with both natural and synthetic ETPs demonstrated a decrease in vascular endothelial growth factor and antiproliferative effects that were abrogated by zinc supplementation. The results have implications for the design of selective ETPs and for the interaction of ETPs with other zinc ion-binding protein targets involved in gene expression.
| S-EPMC2785371 | biostudies-literature
Project description:Hypoxia-inducible factor-1 (HIF-1) is a known cancer progression factor, promoting growth, spread, and metastasis. However, in selected contexts, HIF-1 is a tumor suppressor coordinating hypoxic cell cycle suppression and apoptosis. Prior studies focused on HIF-1 function in established malignancy; however, little is known about its role during the entire process of carcinogenesis from neoplasia induction to malignancy. Here, we tested HIF-1 gain of function during multistage murine skin chemical carcinogenesis in K14-HIF-1alpha(Pro402A564G) (K14-HIF-1alphaDPM) transgenic mice. Transgenic papillomas appeared earlier and were more numerous (6 +/- 3 transgenic versus 2 +/- 1.5 nontransgenic papillomas per mouse), yet they were more differentiated, their proliferation was lower, and their malignant conversion was profoundly inhibited (7% in transgenic versus 40% in nontransgenic mice). Moreover, transgenic cancers maintained squamous differentiation whereas epithelial-mesenchymal transformation was frequent in nontransgenic malignancies. Transgenic basal keratinocytes up-regulated the HIF-1 target N-myc downstream regulated gene-1, a known tumor suppressor gene in human malignancy, and its expression was maintained in transgenic papillomas and cancer. We also discovered a novel HIF-1 target gene, selenium binding protein-1 (Selenbp1), a gene of unknown function whose expression is lost in human cancer. Thus, HIF-1 can function as a tumor suppressor through transactivation of genes that are themselves targets for negative selection in human cancers.
| S-EPMC2756430 | biostudies-literature