Role Of Hypoxia-inducible Factor Research Articles

Abstract 1132: Regulation of the glutamine-to-lipid pathway by HIF: Reductive TCA cycle is a metabolic signature of VHL deficiency

Abstract Cancer cells undergo fundamental changes in glucose and glutamine metabolism to support anabolic processes. Acetyl-CoA is a central precursor for lipid synthesis, being generated from glucose-derived citrate in well oxygenated cells. Cells exposed to hypoxia divert glucose to lactate, raising the question of how TCA cycle is maintained to support lipogenesis. We recently showed that, under hypoxia conditions, cancer cells primarily utilize glutamine for lipid synthesis through reductive TCA cycle (redTCA). To investigate the regulation of this metabolic switch, we studied the role of Hypoxia Inducible Factors (HIF1s) in renal cell carcinoma (RCC) cell lines that are deficient in the von Hippel-Lindau (VHL) tumor suppressor gene. These cells exhibit constitutive HIF activity irrespective of oxygen availability. Here, we show that loss-of-VHL engages RCC cells in redTCA even under normoxia conditions in a HIF-dependent manner. Reintroduction of VHL restores the glucose-to-lipid flux. Inactivation of HIF regulatory subunits dramatically attenuates redTCA in RCC cell lines. Inversely, exogenous expression of a VHL-insensitive HIF2α mutant (P564toA) in VHL proficient cell lines is sufficient to stimulate redTCA cycle and lipogenesis from glutamine, under conditions of normoxia. Importantly, loss of VHL rendered RCC cells sensitive to glutamine restriction. VHL-deficient RCC cells grow less than their VHL-replete isogenic counterparts when cultured under conditions of low glutamine availability. Our results elucidate the metabolic control of lipogenesis by the VHL-HIF signaling pathway and highlight novel therapeutic targets for RCC and HIF-overexpressing tumors. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 1132. doi:1538-7445.AM2012-1132

Abstract 3945: HIFs regulate alternative splicing of HIF target genes

Abstract Alternative splicing is the process in which identical pre-mRNA molecules are spliced in different ways, allowing individual gene to express multiple mRNAs or isoforms that encode proteins with diverse and even antagonistic functions. Alternative splicing occurs in over 70% of human genes, is important in normal development and many diseases including cancer. It is well known that most solid-tumors are hypoxic and the hypoxic microenvironment is a driving force for tumor progression and metastasis by hypoxia-inducible-factor (HIF)-mediated transcriptional programs that increase genes involved in tumor growth, angiogenesis, and metastasis. Here, we report a novel finding that transcriptional factor HIF not only activates gene expression, also regulates RNA splicing of its target genes, generating isoforms that favor tumor growth. Using an Exon Microarray we found that approximately 1000 genes are predicted to undergo hypoxia-mediated AS in Hep3B cells, 100 of those genes are hypoxia inducible genes. Using RT-PCR, RT-qPCR and WB we validated that the first 10 HIF target genes, CA9, ANGPTL4, WNK1, PLOD2, ADM, DUOX2, ENO2, P4HA2, EGLN3, and PDK1 undergo hypoxia-mediate AS, as predicted by exon array. Interestingly, AS of these genes is regulated by HIFs, not by hypoxia since: 1) siRNA knockdown of ARNT, HIF1, or HIF2 inhibits hypoxic induction of HIF target genes as well as inhibits hypoxia-mediated splicing changes; and 2) Normoxic HIF activity by deleting VHL, inhibiting PHD, or expressing normoxic-stable HIF protein led to hypoxic splicing patterns of HIF target genes, demonstrating HIF activity is sufficient to induce alternative splicing of HIF target genes. However, AS of HIF target genes cannot be explained by increased transcription of these genes since no splicing changes were observed when these genes were activated by hybrid protein with HIF transactivation domains replaced by VP16, E2F1, or SP1 transactivation domain. Further experiments indicated that the N-terminal transactivation domains (N-TAD) of HIF1α or HIF2α are responsible for splicing changes of these HIF-target genes. In summary, we have uncovered a novel function of HIFs in the regulation of target gene splicing. The discovery of HIF's role in mRNA splicing of its target genes will change the dogma concerning the role of HIF in cancer progression. We propose that HIFs promote cancer progression not only through transcription activation but also through alteration of mRNA splicing of HIF targets. RO1 CA134687 NIH/NCI (Hu) Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 3945. doi:1538-7445.AM2012-3945

Abstract 5722: Retention of the radiosensitizing effect of gemcitabine and its main metabolite dFdU under reduced oxygen conditions is not influenced by HIF-1 functionality

Abstract Introduction: Regions within solid tumors often experience mild to severe oxygen deprivation, associated with resistance to chemotherapy and irradiation. The aim of this study was to evaluate the radiosensitizing effect of gemcitabine and its main metabolite dFdU under normal versus reduced oxygen conditions and to determine whether hypoxia-inducible factor 1 (HIF-1) is involved in the radiosensitizing mechanism. Materials & methods: The clonogenic assay was performed in three isogenic MDA-MB-231 breast cancer cell lines differing in HIF-1alpha proficiency (24h 0-8 nM gemcitabine or 0-4 microM dFdU, 0-8 Gy irradiation). Validation of the transfection with dominant negative HIF-1alpha was done by western blot and by assessment of HIF-1alpha activity. The relative expression of 84 genes related to the hypoxia signaling pathway was characterized by human hypoxia signaling pathway PCR array. Using radiosensitizing conditions, cells were collected for cell cycle analysis. Results: HIF-1 activity was significantly inhibited after transfection with a dominant negative protein. Furthermore, anoxia-induced VEGF secretion was significantly lower (p<0.05) in MDA-MB-231 cells stably expressing dnHIF (dominant negative HIF-1alpha) than in MDA-MB-231 EV (empty vector) cells. PCR array indicated that hypoxic conditions significantly influenced the expression of HIF-1alpha and ANGPTL4 (angiopoetin-like 4). A clear radiosensitizing effect under normoxic and anoxic conditions was observed for both gemcitabine and dFdU. The radiosensitizing effect was similar under normoxic and anoxic conditions (p=0.48 for gemcitabine, p=0.56 for dFdU) and the dose enhancement factor (DEF) was not significantly influenced by the cell line used. Under anoxia, DEFs for gemcitabine ranged from 1.26 to 1.59, from 1.11 to 1.77, and from 1.34 to 2.04 in MDA-MB-231 wt, EV and dnHIF cells, respectively. Statistical analysis revealed no significant differences in radiobiological parameters between HIF-1 proficient and HIF-1 deficient cells. Cell cycle analysis showed that, in contrast to previous findings in other cell lines, exposure of MDA-MB-231 cells to low oxygen conditions did not induce a significant increase in the percentage of G0/1 cells (p=0.21). Gemcitabine and dFdU caused a block of cells in the S phase of the cell cycle under both normoxic and anoxic conditions. Conclusion: For the first time, radiosensitization by dFdU, the main metabolite of gemcitabine, was demonstrated under low oxygen conditions. As dFdU has a prolonged half-life, the sustained presence of dFdU in the blood might induce radiosensitization despite the short half-life of the parent drug, gemcitabine. This might be highly relevant, especially considering delivery of the drug to hypoxic tumor regions. No major role for HIF-1 in radiosensitization by gemcitabine or dFdU could be shown. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 5722. doi:1538-7445.AM2012-5722

Negative Regulation of the Human Growth Hormone Gene by Insulin in Primary Pituitary Cell Cultures and a Possible Role for Hypoxia Inducible Factor (HIF)

Hyperinsulinemia is a key component of metabolic syndrome, and is associated with decreased growth hormone (GH) levels. There is evidence that the human (h) GH gene (hGH1) is a direct target for insulin. A hybrid reporter gene driven by upstream −496/+1 hGH1 sequences, including a putative insulin‐responsive HIF site, was negatively regulated by insulin in transfected tumor cells. Here, we have started to assess whether HIF is associated with insulin regulation of “endogenous” hGH1. In the absence of primary human pituitary cell cultures, transgenic (TG) mice expressing the intact hGH1 locus in a somatotroph‐specific manner were generated. Primary pituitary cell cultures from these TG mice were treated with or without 1–15 nM insulin. A significant decrease in hGH1 RNA levels was detected with a physiological dose of insulin. Stabilization of HIF protein by exposure to the hypoxia mimetic CoCl2 decreased hGH1 RNA levels significantly, and to the same extent as insulin treatment. The effects of inhibition of HIF synthesis by RNA interference, and HIF DNA binding by echinomycin treatment were also pursued. In both cases, the decrease in hGH1 RNA levels seen with insulin treatment was blocked significantly. These data indicate hGH1 RNA levels are regulated negatively by insulin, and that this effect is dependent on HIF protein/DNA binding.

61 Hypoxia-Inducible Factor 1 (HIF-1) Transcription is a “Signalling Driver” for Allergic Inflammation, Host Innate Immune Defence and Leukaemia Progression

BackgroundHypoxia-inducible factor 1 is a transcription complex that plays a pivotal role in cellular adaptation to low oxygen availability, which occurs during allergic responses, host immune defence and leukaemia progression. We investigated the role of HIF-1 in cellular adaptation to stress associated with different types of pathological reactions of immune cells. We studied IgE-dependent responses of human mast cells and basophils, Toll-like receptor (TLR)-mediated innate immune reactions of human myeloid cells and stem cell factor (SCF)-mediated responses of hematopoietic cells of myeloid lineage.MethodsLAD2 human mast cells1, primary human basophils, and THP-1 human myeloid cells were used for investigations of FcεRI, TLR ligand and SCF-induced responses. Quantitative real-time PCR, Western blot analysis, ELISA, fluorometry, luminometry and fluorescence microscopy were employed to run the assays.ResultsWe observed that HIF-1 activation is differentially regulated in the cases of pro-allergic, TLR-dependent and SCF-induced cellular responses. While PI3K/mTOR and MAP kinase pathways were the major contributors to HIF-1 activation during allergic/SCF-dependent responses, TLR-mediated processes occurred mostly via redox-dependent mechanisms. Experiments with HIF-1α (the inducible subunit regulating HIF-1 transactivation) knockdown cells demonstrated that HIF-1 plays a crucial role in the expression of the primary angiogenic cytokine VEGF and controls intracellular energy metabolism by regulating glycolytic metabolic activity.ConclusionsThe HIF-1 transcription complex supports not only the survival of immune cells (mast cells, basophils, myeloid cells) in pathological environments but also determines their abilities to generate pro-allergic, pro-inflammatory as well as pro-angiogenic cytokines over sustained periods.

Hypoxia-Inducible Factor Activation in Myeloid Cells Contributes to the Development of Liver Fibrosis in Cholestatic Mice

Macrophages play an integral role in the development of liver fibrosis by releasing mediators, such as platelet-derived growth factor-B (PDGF-B) and transforming growth factor-β1, which stimulate hepatic stellate cell proliferation, chemotaxis, and collagen production. However, the mechanism by which chronic liver injury stimulates macrophages to release these mediators is not completely understood. We tested the hypothesis that chronic liver injury activates hypoxia-inducible factor (HIF) transcription factors in macrophages that regulate the production of mediators that promote fibrosis. To test this hypothesis, Cre/lox technology was used to generate myeloid cell-specific HIF-1α or HIF-1β knockout mice. When these mice were subjected to bile duct ligation (BDL), levels of α-smooth muscle actin and type I collagen in the liver were reduced compared with those of mice with normal levels of HIFs. The deficiency of HIFs in macrophages did not affect liver injury or inflammation after BDL but reduced PDGF-B mRNA and protein, suggesting that HIF activation in macrophages may promote fibrosis by regulating the production of PDGF-B. Consistent with a role for HIFs in liver fibrosis in cholestatic liver disease, nuclear HIF-1α protein was present in macrophages, hepatocytes, and fibroblasts in the livers from patients with primary biliary cirrhosis and primary sclerosing cholangitis. These studies demonstrate that HIFs are important regulators of profibrotic mediator production by macrophages during the development of liver fibrosis and suggest that HIFs may be a novel therapeutic target for the treatment of chronic liver disease in patients.

On the Pro-Metastatic Stress Response to Cancer Therapies: Evidence for a Positive Co-Operation between TIMP-1, HIF-1α, and miR-210

In contrast to expectations in the past that tumor starvation or unselective inhibition of proteolytic activity would cure cancer, there is accumulating evidence that microenvironmental stress, such as hypoxia or broad-spectrum inhibition of metalloproteinases can promote metastasis. In fact, malignant tumor cells, due to their genetic and epigenetic instability, are predisposed to react to stress by adaptation and, if the stress persists, by escape and formation of metastasis. Recent recognition of the concepts of dynamic evolution as well as population and systems biology is extremely helpful to understand the disappointments of clinical trials with new drugs and may lead to paradigm-shifts in therapy strategies. This must be complemented by an increased understanding of molecular mechanism involved in stress response. Here, we review new roles of Hypoxia-inducible factor-1 (HIF-1), one transcription factor regulating stress response-related gene expression: HIF-1 is crucial for invasion and metastasis, independent from its pro-survival function. In addition, HIF-1 mediates pro-metastatic microenvironmental changes of the proteolytic balance as triggered by high systemic levels of tissue inhibitor of metalloproteinases-1 (TIMP-1), typical for many aggressive cancers, and regulates the metabolic switch to glycolysis, notably via activation of the microRNA miR-210. There is preliminary evidence that TIMP-1 also induces miR-210. Such positive-regulatory co-operation of HIF-1α, miR-210, and TIMP-1, all described to correlate with bad prognosis of cancer patients, opens new perspectives of gaining insight into molecular mechanisms of metastasis-inducing evasion of tumor cells from stress.

Hypoxia-inducible factor-1 (HIF-1) promotes LDL and VLDL uptake through inducing VLDLR under hypoxia

Metabolism under hypoxia is significantly different from that under normoxia. It has been well elucidated that HIF-1 (hypoxia-inducible factor-1) plays a central role in regulating glucose metabolism under hypoxia; however, the role of HIF-1 in lipid metabolism has not yet been well addressed. In the present study we demonstrate that HIF-1 promotes LDL (low-density lipoprotein) and VLDL (very-LDL) uptake through regulation of VLDLR (VLDL receptor) gene expression under hypoxia. Increased VLDLR mRNA and protein levels were observed under hypoxic or DFO (deferoxamine mesylate salt) treatment in MCF7, HepG2 and HeLa cells. Using dual-luciferase reporter and ChIP (chromatin immunoprecipitation) assays we confirmed a functional HRE (hypoxia-response element) which is localized at +405 in exon 1 of the VLDLR gene. Knockdown of HIF1A (the α subunit of HIF-1) and VLDLR, but not HIF2A (the α subunit of HIF-2), attenuated hypoxia-induced lipid accumulation through affecting LDL and VLDL uptake. Additionally we also observed a correlation between HIF-1 activity and VLDLR expression in hepatocellular carcinoma specimens. The results of the present study suggest that HIF-1-mediated VLDLR induction influences intracellular lipid accumulation through regulating LDL and VLDL uptake under hypoxia.

Predictive Immunohistochemical Biomarkers in the Context of Neoadjuvant Therapy for Breast Cancer

The adoption of personalized medicine has led to the search for prognostic and predictive markers that can be applied to individual patients to give optimal information for their clinical management. We have used samples from randomized clinical trials of hormonal and chemotherapy to identify relevant markers of sensitivity and resistance using a neoadjuvant approach by linking expression of a panel of proteins involved in growth factor receptor signaling, angiogenesis, estrogen receptor signaling, and hypoxia to individual patient response. We evaluated samples from randomized clinical trials of epirubicin with or without tamoxifen, and letrozole with or without metronomic cyclophosphamide, to study chemotherapy, hormonal therapy, and antiangiogenic effects. We present a proof of principle of this approach in identifying several key pathways that are associated with clinical and pathological response. Thus, we have shown that the hypoxia-inducible factor (HIF) pathway, mitogen activated protein kinase, and phosphorylated estrogen receptor-α can identify patients who are likely to respond to hormonal therapy and that HIF signaling is also a marker of resistance for anthracycline-based chemotherapy. To redress the role of HIF, we then evaluated samples from a randomized control trial of an anthracycline chemotherapy with and without erythropoietin. These studies demonstrate that the approach of using primary systemic therapy in breast can identify markers of response and potentially targets for rationale design of new therapies.

Hypoxia, stem cells and bone tumor

Normal oxygen level is critical for niches that together with other components of the niche play vital role in regulating stem or tumor cells behavior. Hypoxia plays an important role in normal development and disease progression, including the growth of solid tumors. The hypoxia inducible factors (HIFs) are the key mediators of the cellular response to hypoxia. In this review, we focused on the role of HIFs on bone tumor formation. Further, we also emphasized how hypoxia, stem cells, and its niches regulate the bone tumorigenesis.

Into Thin Air: New Insights Into the Role of Hypoxia-Inducible Factor in Cancer and Ischemic Diseases

Into Thin Air: New Insights Into the Role of Hypoxia-Inducible Factor in Cancer and Ischemic Diseases

Role of Hypoxia-Inducible Factor α in Response to Hypoxia and Heat Shock in the Pacific Oyster Crassostrea gigas

The Pacific oyster Crassostrea gigas inhabits the intertidal zone and shows tolerance to stress conditions such as hypoxia and heat shock. Although some information is available about the genes expressed in response to hypoxia, little is known about the molecular mechanism of the regulation of their expression in mollusks, including the Pacific oyster. Hypoxia-inducible factor 1α (HIF-1α) is a master regulator of hypoxia-responsive transcription. In this study, we cloned HIF-α from the oyster and investigated its response to unique stress conditions, including air exposure, for the first time in mollusks. The cDNA of oyster Hif-α is 3,182bp long, of which 2,094bp encodes a protein of 698 amino acid residues. Northern and Western blot analysis showed that expression of oyster HIF-α mRNA and protein were induced by air exposure, and that expression was induced periodically during air exposure. In addition, induction of Hif-α mRNA increased by a maximum 8.0-fold by heat shock. Under heat shock at 35°C (lethal temperature for the oyster), however, it was induced later than at 30°C. After recovery from hypoxia and/or heat shock, Hif-α mRNA also upregulated. These data suggest that the oyster has a strategy to induce Hif-α mRNA in order to survive hypoxia and heat shock, and that HIF signaling is necessary for recovery from stress.

A HIF-1 Target, ATIA, Protects Cells from Apoptosis by Modulating the Mitochondrial Thioredoxin, TRX2

The regulation of apoptosis is critical for controlling tissue homeostasis and preventing tumor formation and growth. Reactive oxygen species (ROS) generation plays a key role in such regulation. Here, we describe a HIF-1 target, Vasn/ATIA (anti-TNFα-induced apoptosis), which protects cells against TNFα- and hypoxia-induced apoptosis. Through the generation of ATIA knockout mice, we show that ATIA protects cells from apoptosis through regulating the function of the mitochondrial antioxidant, thioredoxin-2, and ROS generation. ATIA is highly expressed in human glioblastoma, and ATIA knockdown in glioblastoma cells renders them sensitive to hypoxia-induced apoptosis. Therefore, ATIA is not only a HIF-1 target that regulates mitochondrial redox pathways but also a potentially diagnostic marker and therapeutic target in human glioblastoma.

Abstract 991: Regulation of glucose metabolism by HIF in pancreatic cancer

Abstract Pancreatic cancer is the fourth leading cause of cancer related deaths with a five-year survival rate of 5.5%. It is characterized by extremely aggressive tumor growth rate and high incidence of metastasis. Like other cancers, pancreatic cancer displays alterations in cellular metabolism, which holds significant promise for better management/cure of the disease. One of the most common and profound biochemical phenotypes of animal and human cancer cells is their ability to metabolize glucose at high rates, even under aerobic conditions. Several oncogenes and tumor suppressors have been implicated in altering tumor cell metabolism in order to facilitate tumor growth and metastasis. The objective of this study was to characterize the role of hypoxia inducible factors (HIF) in glucose metabolism in pancreatic cancer cell lines under normoxic and hypoxic conditions. We screened a panel of pancreatic cancer cell lines for glucose uptake under normoxic and hypoxic conditions. Although the effect of hypoxia on glucose uptake was variable in different pancreatic cancer cell lines, it correlated well with the expression levels of HIF-1alpha and HIF-2alpha. Furthermore, dual knockdown of HIF-1alpha and HIF-2alpha had similar negative effect on growth rate under hypoxic conditions, as did the treatment with glycolysis inhibitor 3-BrPA. These studies suggest that HIF factors regulate growth in pancreatic cancer by regulating glycolysis. Hence, combining strategies to target metabolism along with the strategies to target signal transduction might synergistically aid in diminishing cancer cell growth and invasiveness. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 991. doi:10.1158/1538-7445.AM2011-991

Abstract 2661: The role of HIF-1 protein on the radiosensitizing effect of difluorodeoxyuridine, the main metabolite of gemcitabine, under normoxic and anoxic conditions

Abstract It is known that gemcitabine and difluorodeoxyuridine (dFdU) have radiosensitizing properties. It has become evident that solid tumors often contain hypoxic regions and that this is one of the causes of resistance or decreased sensitivity to cancer therapy. In hypoxic conditions, the transcription factor, hypoxia-inducible factor-1 (HIF-1), is upregulated. HIF-1 is responsible for the cellular and adaptive responses of tumors to survive in hypoxic conditions. Recently, it has been demonstrated that gemcitabine retains its radiosensitizing potential under hypoxia. In the present study, the radiosensitizing potential of dFdU under anoxic conditions is investigated as well as the role of HIF-1 protein. In order to explore the role of HIF-1, human tumor cell lines included in this study were MDA-MB-231 (breast adenocarcinoma cell line, wt HIF-1), MDA-MB-231 DN-HIF (transfected with dominant-negative HIF-1α) and MDA-MB-231 EV (empty vector transfected control). Anoxic conditions (<0.1% O2,) were achieved in a Bactron IV anaerobic chamber. To analyze the radiosensitizing effect of dFdU, the clonogenic assay was performed. Cells were exposed to normoxic or anoxic conditions and were simultaneously treated with 0, 2 or 4 microM dFdU for 24h immediately before irradiation (0-8 Gy, room temperature, linear accelerator). Immediately following radiation, anoxic cells were reoxygenated and cells were washed with drug-free medium. Using radiosensitizing conditions, cells were collected for cell cycle analysis by flow cytometry. A clear concentration-dependent radiosensitizing effect of dFdU was observed under both normoxic and anoxic conditions (dose enhancement factor (DEF) under normoxia: 1.74-3.38; under anoxia: 2.08-3.81). Combination index (CI) analysis showed a synergistic to additive interaction between dFdU and radiation under normoxia (CI 0.651 ± 0.175), yet an additive interaction under anoxia (CI 0.784 ± 0.120). Statistical analysis using two-way ANOVA revealed that cell survival was significantly influenced by the concentration of dFdU, the dose of radiation, the oxygen tension and the cell line. Post hoc analysis indicated no significant difference between the three cell lines for DEF, ID50, mean inactivation dose and survival fraction at 2 Gy, suggesting that the functionality of HIF-1 protein has no impact on the radiosensitizing effect of dFdU. Considering the cell cycle distribution after treatment with dFdU, 24h treatment with 2 or 4 microM dFdU established a significant S-phase block in both normoxic and anoxic MDA-MB-231 wt and DN-HIF cells. In conclusion, this study showed that dFdU has a clear concentration-dependent radiosensitizing effect in MDA-MB-231 breast cancer cells under normoxic as well as anoxic conditions. No major role for functional HIF-1 protein in radiosensitization by dFdU could be demonstrated. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 2661. doi:10.1158/1538-7445.AM2011-2661

Abstract 447: A mechanism of hypoxia-induced immune escape in cancer cells

Abstract We previously showed that hypoxia induces resistance to natural killer (NK) cell-mediated lysis in tumor cells through a mechanism that involves the shedding of NK cell-activating ligands (MICA) from the cell surface. Furthermore, we were able to block this hypoxia-induced shedding of MICA, as well as resistance to NK cell-mediated lysis, by activating NO signaling in the cancer cells. The objective of the present study was to fully elucidate this mechanism of hypoxia-induced immune escape. We used siRNA knock-down to determine the role of hypoxia-inducible factor-1 (HIF-1), a transcriptional activator of hypoxia-inducible genes, and ADAM10, a metalloproteinase known to be involved in the shedding of MICA, in the hypoxia-induced immune escape in DU145 prostate cancer cells and MDA-MB-231 breast cancer cells. Our findings revealed that in vitro exposure to hypoxia increases ADAM10 expression in a HIF-1-dependent manner, and that knock-down of ADAM10 abolishes the hypoxia-induced MICA release and resistance to NK cell-mediated lysis. Treatment of the tumor cells with low concentrations of nitroglycerin inhibited the hypoxia-induced accumulation of HIF-1α, ADAM10 up-regulation, the shedding of the NK-activating ligands, and resistance to NK cell-mediated lysis. More importantly, continuous transdermal administration of nitroglycerin (1.8 µg/h) to nude mice attenuated the growth of transplanted human DU145 prostate tumors; however, this effect of nitroglycerin was lost in mice made deficient in NK cells by treatment with anti-asialo GM1 antibody. This latter finding indicates that nitroglycerin attenuates tumor growth by sensitizing tumor cells to innate immunity. These findings are important because they indicate that nitric oxide mimetics could potentially be used as immunosensitizers in the treatment and/or prevention of cancer. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 447. doi:10.1158/1538-7445.AM2011-447

Current Insights into the Role of HIF-1 in Cutaneous Wound Healing

Hypoxia Inducible Factor-1 (HIF-1) is considered the major coordinator of the cellular adaptive response to hypoxia. Over recent years, its activity in the context of wound healing has been the object of increasing investigation. On the molecular level, HIF-1 transcriptional target products have been shown to regulate the process of endothelial cell survival, migration and proliferation (VEGF, ANGPT-1, ANGPT-2, ANGPT-4, FGF-2, PlGF, PDGF-B, RGC-32), vascular smooth muscle cell migration and proliferation (FGF-2, EGF, PDGF, thrombospondin) and mobilization of Circulating Angiogenic Cells to the periphery (SFD-1/CXCR4). Studies on the effect of HIF-1 on the expression and activity of extracellular cell matrix modifying enzymes, such as MMPs and prolidase, have been conducted in the context of tumor angiogenesis and metastasis, and have resulted in controversial findings. A growing body of evidence suggests that HIF-1 also affects reepithelialization of the wound bed, through increasing keratinocyte migration, but decreasing their proliferation. Diminished HIF-1 levels and activity have been documented in conditions of impaired wound healing, such as wound healing in aged and in diabetic mice. The increasing number of studies on the role of HIF-1 in wound healing, apart from answering certain questions, has also raised an equal number, if not more. Clarifying the topics that still remain unclear could introduce a new era of HIF-1 targeted management of a wide range of problematic wounds.

Role of hypoxia inducible factor 1 in vascularization and vascular remodeling

种植义齿技术是建立在骨整合理论的基础上,所谓骨整合即种植体表面与骨之间的直接结合,在自体骨上已达到理想的效果[1].随着生物医学、材料学、仿生学的发展,组织工程骨得到了迅速的发展,并以其优异的性能克服了自体和异体骨组织移植的缺点,有望在人体硬组织缺损修复中得到广泛应用[2]。

The relationship of HIF2 and the progression of PTEN-deficient mouse prostate tumors.

30 Background: The hypoxia-inducible factor (HIF) transcription factor has already cemented its oncogenic role in the development of renal cell carcinoma (RCC). However, its role in the tumorigenesis of other solid tumors remains unspecificed. Our studies focus on a novel link between HIF and prostate carcinogenesis. Methods: Using both in vitro cell culture studies as well as in vivo studies (orthotopic xenograft and genetically engineered mouse models) we investigate the role of HIF in prostate cancer cell proliferation, invasion, and progression. Results: Both HIF1 and HIF2 appear to be necessary for the proliferation and invasion of prostate cancer cell lines in vitro. Preliminary analysis of a PTEN deficient mouse model of prostate cancer suggests that expression of a stabilized form of HIF2 promotes the development of a larger prostate tumor burden and a more aggressive histology (high grade prostate intraepithelial neoplasia [PIN] at earlier stages). Moreover, PTEN-deficient prostate tumors producing HIF2 are more proliferative and vascular and express increased levels of genes associated with epithelial to mesenchymal transition (EMT). Conclusions: There has been much interest in the role of angiogenesis and hypoxia in prostate cancer progression. Our preliminary data suggest that HIF2 is able to promote PTEN-deficient prostate cancer progression in mice by increasing proliferation, angiogenesis, and EMT. No significant financial relationships to disclose.

Systemic Sclerosis 2011

Systemic Sclerosis 2011