Hypoxia-induced activation of hif-1 role of hif-1alpha-hsp90 interaction

Abstract Hypoxia-Inducible Factor HIF -1 is a dimeric protein complex that plays an integral role in the body's response to low oxygen concentrations, or hypoxia. Oxygen Metabolism in Mammals Oxygen is required by the cells of most organisms to produce adequate amounts of ATP necessary for metabolic activities. Open in a separate window. Figure 1. Transcriptional Regulation Controls Angiogenesis in Hypoxia One important HIF-1 function is to promote angiogenesis; HIF-1 directs migration of mature endothelial cells toward a hypoxic environment [ 2 , 5 ].

Cancer, Inflammation, and Hypoxia Environments surrounding metastasizing tumor masses are often hypoxic. Tumor Proliferation Due to its role in hypoxia, HIF-1 plays a critical part in tumor proliferation [ 18 ]. Figure 2. Small Molecule Inhibitors Several small molecules, such as dimethyloxalylglycine, a prolyl hydroxylase inhibitor, activate HIF Therapeutic Targets in the HIF-1 Pathway: Cancer With a clearer understanding of the HIF-1 pathway, efforts are directed at manipulation of this complex genetic process in order to ultimately increase or decrease cellular HIF-1 levels.

Conclusions As more is learned about functions, target genes, and activation pathways of HIF-1, novel treatments of diseases such as cancer and ischemia can be developed. Acknowledgments Dr. References Semenza GL. HIF mediator of physiological and pathophysiological responses to hypoxia. J Appl Physiol. Regulation of human placental development by oxygen tension. Hypoxic microenvironment within an embryo induces apoptosis and is essential for proper morphological development.

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D Normoxic and hypoxic lactate production. Lactate expression values were normalized against normoxic lactate production rate of MCF-7 cells. Under hypoxia, all cells displayed significant increases in all transcripts except EPO. The data from these experiments imply that GLUT-1 expression might be inducible under hypoxia in MDA-mb, but the results were not significant. All cell lines appeared to have relatively similar EPO and CA9 transcript levels under normoxia and hypoxia.

Figure 1 C illustrates that 2dG trapping in MDA-mb cells was not significantly different between normoxia and hypoxia. In MDA-mb cells, there was a modest 1. These results were consistent with those reported earlier using a nonradioactive assay for glucose consumption [ 26 ].

Therefore, lactate production levels were also measured under normoxic and hypoxic conditions to determine if glycolysis was similarly affected. MDA-mb cells produced lactate at similar levels under both normoxia and hypoxia, approximately five times the rate of MCF-7 cells under normoxia. MCF-7 cells, the lowest-expressing line under normoxia, significantly increased lactate production when exposed to hypoxia approximately 2.

Metastatic cell line MDA-mb demonstrated levels of lactate production three times the levels observed in MCF-7 cells under normoxia. These cells produced a small, but significant, increase 1. These data are consistent with similar experiments performed previously [ 11 ]. D Normoxic and hypoxic lactate expression.

In both cell lines, lactate production rates correlated to the glucose consumption results Figure 3 D in that RCC4 cells demonstrated higher normoxic lactate production than the vH-L transfectants and did not upregulate lactate production when grown under hypoxia, whereas a lactic acid increase was observed in the vH-L transfectants.

In this same study, angiogenesis was unaffected, underscoring the functional relationship between HIF-1 activity and glycolysis. These cell lines are aggressively metastatic. Nonetheless, within single cancers i. Upregulation of these angiogenic factors may play a part in morphogenesis of chaotic vasculature, which is a hallmark of solid tumors [ 30 ].

The high normoxic expression of VEGF and other growth factors may be responsible for the correlation between microvessel density and tumor aggressiveness [ 31 ]. The data in this study indicate that elevated HIF-1 activity is sufficient, but not necessary, for the Warburg effect.

Other mechanisms resulting in glycolytic induction are possible. The variable mechanisms used to enhance glycolysis, combined with the almost uniform observation of high FdG uptake in metastatic cancers, strongly suggest that elevated glycolysis is not merely an epiphenomenon of underlying molecular alterations, but is instead a key phenotype in cancer progression [ 4,39 ].

National Center for Biotechnology Information , U. Journal List Neoplasia v. Author information Article notes Copyright and License information Disclaimer. Address all correspondence to: Robert J. E-mail: ude. All rights reserved.

This article has been cited by other articles in PMC. Abstract Metastatic tumors generally exhibit aerobic glycolysis the Warburg effect. Keywords: Warburg effect, hypoxia-inducible factor, glucose consumption, lactate, glycolysis. Introduction Warburg [ 1 ] first established a correlation between aggressive tumor phenotypes and elevated glycolysis when he observed that many tumors produce excessive levels of lactic acid even in the presence of oxygen.

Table 1 Primer Sequences. Open in a separate window. Figure 1. Figure 2. Figure 3. References 1. Warburg O. On the origin of cancer cells. Czernin J, Phelps ME. Positron emission tomography scanning: current and future applications. Annu Rev Med. The transcrip- cytoplasmic form associated with the chaperone protein heat tion factor hypoxia-inducible factor-1KK HIF-1K K , involved in the shock protein 90 Hsp90 [8].

Hsp90 chaperone is among HIF-1 activation by hypoxia. As chaperone, Hsp90 prevents the aggregation of un- chimeric protein expressed in COS-7 cells interacts with Hsp90 folded proteins generated by heat shock [12], oxidative [13] or in normoxia but not in hypoxia. Among these factors are zinc nucleus. These results indicate that Hsp90 is a major as Sim and Ahr [6]. In ad- Heat shock protein 90 dition, Gradin et al.

Introduction This work was aimed to elucidate the role of this chaperone in the regulation of HIF-1K translocation and of HIF-1 tran- In response to a reduced oxygen level, activation of hy- scriptional activity. We observed that Hsp90 is associated with poxia-inducible factor-1 HIF-1 regulates the transcription HIF-1K in normoxia and is necessary to obtain an activable of several genes such as erythropoietin, vascular endothelial form of HIF-1 by hypoxia in COS-7 and human microvascu- growth factor, inducible nitric oxide synthase, T [1].

All these lar endothelial HMEC-1 cells. HIF-1 is a heterodimeric 2. Normoxia and hypoxia incubations were performed in CO2 -independent medium by the proteasome pathway [4,5]. ARNT is a common factor already known as Ah receptor 2. Fax: 32 81 72 41 HRE downstream from the luciferase gene [21], for which the ex- E-mail: emmanuel.

All rights reserved. Minet et al. Immunoprecipitation and Western blot analysis Observations were performed using a confocal microscope Leica, Total cell extracts were prepared from COS-7 cells grown in 25 cm2 Hamburg, Germany. Twenty-four hours post-transfection, the cells were incubated for 2 h and 30 min in normoxia or in hypoxia. The lysate was collected in micro-centrifuge tubes and incubated on ice for 30 min.

An aliquot of 50 Wl of this supernatant was boiled and kept frozen supernatant 1. Hsp90 antibodies H antibodies provided by Prof. The super- natant was boiled and kept frozen supernatant 2. Anti- mouse horseradish peroxidase-conjugated secondary antibodies Amersham Pharmacia, Uppsala, Sweden were used for detection by chemiluminescence.

Hsp90 antibodies were added with Sephar- ose-protA beads and the mix was incubated overnight. Then, the gel was dried and the immunoprecipitated product was detected by Fig. Hsp dependent activation of HIF A Schematic repre- autoradiography. Northern blot analysis heterologous SV40 promoter. Five sham. The probe used is bp long and hybridizes on the third hours after transfection, the cells were incubated for 20 h either in exon of the human Hsp Both probes were labelled cal hypoxia.

Then, the cells were lysed for luciferase assays. Results 3. Hsp90 is necessary for HIF-1 activity Several works were aimed to understand the role of Hsp90 in the regulation of transcription factor activity glucocorti- coid receptor, Ahr.

In yeast expressing a regulatable level of Hsp90, the Ahr signaling pathway is disrupted when the ex- Fig. All these tated with Hsp