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Summary HIF‐2α, encoded by EPAS1, plays a dominant role in regulating erythropoietin (EPO) production, maintaining the dynamic balance of erythropoiesis. Gain‐of‐function mutations in EPAS1 cause erythrocytosis. However, anaemia caused by EPAS1 loss‐of‐function mutations has been confined to only one case report, and the underlying mechanism remains unclear. Herein, the reanalysis of high‐throughput sequencing data from 311 patients with anaemia identified three monoallelic EPAS1 variants from three unrelated families in a paediatric anaemia cohort. The probands showed highly consistent clinical phenotypes with normocytic and normochromic anaemia, reticulocytopenia and relative deficiency of serum EPO, characterised as congenital hypoplastic anaemia. In vitro studies suggested that defects in steady‐state protein abundance, nuclear localisation and binding with co‐activator in EPAS1 variants lead to impaired EPO transcriptional activation. Therefore, loss‐of‐function mutations in EPAS1 can cause erythroid hypoplasia in an EPO‐dependent manner. This study identified a new causative gene for congenital hypoplastic anaemia and clarified the molecular aetiology of loss‐of‐function EPAS1 mutations. [ABSTRACT FROM AUTHOR]

Introduction: Hypoxia‐inducible factor‐2α (HIF‐2α) modulates the hypoxic response pathway in tumors; however, mutations in pathways (including SDHA, SDHB, SDHC, SDHD, FH, and VHL genes) that are suspected to activate HIF‐2α are poorly understood, with limited understanding of the prevalence and clinical prognosis. Methods: This retrospective observational study used a de‐identified nationwide (US‐based) clinico‐genomic database (CGDB) across 15 available tumor types. Results: Among the 9467 adult patients with advanced/metastatic solid tumors included in the analysis, any mutation at the above‐mentioned six genes was observed in 1.8% (95% CI: 1.5–2.1) of patients. The mutation prevalence ranged from 0.05% of SDHD to 0.93% of VHL. When further stratified by tumor type, the prevalence of gene mutation in each tumor type was well below 1%, except for VHL with 44% in renal cell carcinomas (RCC). Excluding RCC, the prevalence of any HIF‐2α gene mutations in the study population was 0.9% (95% CI: 0.8–1.2). The median overall survival (OS) from 1 and 2 L therapy among patients with any HIF‐2α gene mutation was 14.5 (95% CI: 11.5–24.2) and 9.3 (95% CI: 6.0–18.1) months, respectively, compared with 13.4 (95% CI: 12.9–13.9) and 9.8 (95% CI: 9.3–10.4) months among patients without HIF‐2α gene mutations. Discussion and Conclusions: The prevalence of HIF‐2α related gene mutations was generally low (<1%) across the 15 solid tumor types, except for VHL in RCC. No significant association between HIF‐2α gene mutation status and OS was identified among patients evaluated in this study. [ABSTRACT FROM AUTHOR]

We conducted a prospective phase II study on whether extended‐field irradiation (EFI) confers survival benefits depending on hypoxic markers in locally advanced uterine cervical cancer (LAUCC). RNA‐seq was performed to identify immune and hypoxic gene signatures. A total of 288 patients were randomized to either EFI or pelvic radiotherapy (PRT). All patients completed chemoradiotherapy. Overall, significantly higher 5‐year para‐aortic recurrence free survival (PARFS) rate occurred in EFI (97.6%) than in PRT group (87.2%), with marginal tendency to improve disease‐free survival (DFS; 78% vs 70%, P =.066). Subgroup analyses were performed based on carbonic anhydrase 9 (CA9)‐only positive, CA9/hypoxia‐inducible factor (HIF) double positive and CA9 negative. In the CA9‐only positive, EFI successfully increased 5‐year PARFS (100% vs 76.4%, P =.010), resulting in significantly improved long‐term DFS (85.7% vs 54.7%, P =.023) compared to the PRT, while there was no such benefit of EFI in the CA9/HIFs double positive. RNA‐seq analysis identified distinct immunehigh subgroup with negative correlation with hypoxia gene signatures (R = −.37, P <.01), which showed a higher 5‐year DFS than the immunelow (P =.032). Hypoxia‐related genes were upregulated in the CA9/HIFs double positive compared to CA9 negative (P <.05). Only 17.4% of patients in CA9‐negative group showed immunelow signatures, while 40.0% of patients in the double‐positive group exhibited immunelow signatures. In conclusion, EFI improved PARFS significantly in all patients, but therapeutic efficacy of EFI in terms of improved DFS was solely observed in CA9‐only positive LAUCC, and not in CA9/HIFs double‐positive subgroup. RNA‐seq analysis suggested that hypoxia‐induced immunosuppression may be related to treatment resistance in LAUCC. [ABSTRACT FROM AUTHOR]

Background and Purpose: Pathological angiogenesis is a major cause of irreversible blindness in individuals with neovascular age-related macular degeneration (nAMD). Macrophages and microglia (MΦ) contribute to aberrant ocular angiogenesis. However, the role of glucose metabolism of MΦ in nAMD is still undefined. Here, we have investigated the involvement of glycolysis, driven by the kinase/phosphatase PFKFB3, in the development of choroidal neovascularization (CNV).Experimental Approach: CNV was induced in mice with laser photocoagulation. Choroid/retinal pigment epithelium (RPE) complexes and MΦ were isolated for analysis by qRT-PCR, western blot, flow cytometry, immunostaining, metabolic measurements and angiogenesis assays.Key Results: MΦ accumulated within the CNV of murine nAMD models and expressed high levels of glycolysis-related enzymes and M1/M2 polarization markers. This phenotype of hyper-glycolytic and activated MΦ was replicated in bone marrow-derived macrophages stimulated by necrotic RPE in vitro. Myeloid cell-specific knockout of PFKFB3, a key glycolytic activator, attenuated pathological neovascularization in laser-induced CNV, which was associated with decreased expression of MΦ polarization markers and pro-angiogenic factors, along with decreased sprouting of vessels in choroid/RPE complexes. Mechanistically, necrotic RPE increased PFKFB3-driven glycolysis in macrophages, leading to activation of HIF-1α/HIF-2α and NF-κB, and subsequent induction of M1/M2 markers and pro-angiogenic cytokines, finally promoting macrophage reprogramming towards an angiogenic phenotype to facilitate development of CNV. The PFKFB3 inhibitor AZ67 also inhibited activation of HIF-1α/HIF-2α and NF-κB signalling and almost completely prevented laser-induced CNV in mice.Conclusions and Implications: Modulation of PFKFB3-mediated macrophage glycolysis and activation is a promising strategy for the treatment of nAMD. [ABSTRACT FROM AUTHOR]

Excessive cardiac fibrosis and inflammation aberrantly contribute to the progressive pathogenesis of arrhythmogenic cardiomyopathy (ACM). Whether sodium‐glucose cotransporter‐2 inhibitor (SGLT2i), as a new hypoglycemic drug, benefits ACM remains unclear. Cardiomyocyte‐specific Dsg2 exon‐11 knockout and wild‐type (WT) littermate mice were used as the animal model of ACM and controls, respectively. Mice were administered by gavage with either SGLT2i dapagliflozin (DAPA, 1 mg/kg/day) or vehicle alone for 8 weeks. HL‐1 cells were treated with DAPA to identify the molecular mechanism in vitro. All mice presented normal glucose homeostasis. DAPA not only significantly ameliorated cardiac dysfunction, adverse remodeling, and ventricular dilation in ACM but also attenuated ACM‐associated cardiac fibrofatty replacement, as demonstrated by the echocardiography and histopathological examination. The protein expressions of HIF‐2α and HIF‐1α were decreased and increased respectively in cardiac tissue of ACM, which were compromised after DAPA treatment. Additionally, NF‐κB P65 and IκB phosphorylation, as well as fibrosis indicators (including TGF‐β, α‐SMA, Collagen I, and Collagen III) were increased in ACM. However, these trends were markedly suppressed by DAPA treatment. Consistent with these results in vitro, DAPA alleviated the IκB phosphorylation and NF‐κB p65 transcriptional activity in DSG2‐knockdown HL‐1 cells. Interestingly, the elective HIF‐2α inhibitor PT2399 almost completely blunted the DAPA‐mediated downregulation of indicators concerning cardiac fibrosis and inflammation. SGLT2i attenuated the ACM‐associated cardiac dysfunction and adverse remodeling in a glucose‐independent manner by suppressing cardiac fibrosis and inflammation via reverting the HIF‐2α signaling pathway, suggesting that SGLT2i is a novel and available therapy for ACM. [ABSTRACT FROM AUTHOR]

The cellular adaptive response to hypoxia relies on the expression of hypoxia‐inducible factors (HIFs), HIF‐1 and HIF‐2. HIFs regulate global gene expression changes during hypoxia that are necessary for restoring oxygen homeostasis and promoting cell survival. In the early stages of hypoxia, HIF‐1 is elevated, whereas at the later stages, HIF‐2 becomes the predominant form. What governs the transition between the two HIFs (the HIF switch) and the role of miRNAs in this regulation are not completely clear. Genome‐wide expression studies on the miRNA content of RNA‐induced silencing complexes (RISC) in HUVECs exposed to hypoxia compared to the global miRNA‐Seq analysis revealed very specific differences between these two populations. We analyzed the miRNA and mRNA composition of RISC at 2 h (mainly HIF‐1 driven), 8 h (HIF‐1 and HIF‐2 elevated), and 16 h (mainly HIF‐2 driven) in a gene ontology context. This allowed for determining the direct impact of the miRNAs in modulating the cellular signaling pathways involved in the hypoxic adaptive response. Our results indicate that the miRNA‐mRNA RISC components control the adaptive responses, and this does not always rely on the miRNA transcriptional elevations during hypoxia. Furthermore, we demonstrate that the hypoxic levels of the vast majority of HIF‐1‐dependent miRNAs (including miR‐210‐3p) are also HIF‐2 dependent and that HIF‐2 governs the expression of 11 specific miRNAs. In summary, the switch from HIF‐1 to HIF‐2 during hypoxia provides an important level of miRNA‐driven control in the adaptive pathways in endothelial cells. [ABSTRACT FROM AUTHOR]

HIF‐2α selective inhibitor showed successful efficacy in sensitive clear cell renal cell carcinoma (ccRCC) presenting higher levels of HIF‐2α compared to resistant tumors with low level of HIF‐2α (negative HIF‐2α ccRCC). Currently, negative HIF‐2α ccRCC lacks truly effective therapeutic agents to improve the outcomes. Bromodomain‐containing protein 9 (BRD9) plays a critical role in human hepatocellular carcinoma, squamous cell lung cancer, acute myeloid leukemia, and so on. However, expression and biological role of BRD9 in negative HIF‐2α ccRCC is poorly understood. Clinically, we demonstrated that expression of BRD9 in negative HIF‐2α ccRCC tissues was higher than that in positive HIF‐2α ccRCC. Moreover, high BRD9 expression was correlated with unfavorable clinicopathological features and predicted the poor overall survival of negative HIF‐2α ccRCC patients. Functionally, BRD9 knockout resulted in reduced proliferation, migration and invasion of negative HIF‐2α ccRCC cells (Caki‐2). In addition, BRD9 was related to the TIIC infiltration level in negative HIF‐2α ccRCC tissues. Mechanistically, Gene set enrichment analysis (GSEA) showed that BRD9 was closely related to Notch signaling pathway. BRD9 knockout resulted in reduced mRNA level of Hes1 and Notch1 in negative HIF‐2α ccRCC in vitro. The overexpression of NICD (Notch intracellular domain) enhanced malignant behaviors of Caki‐2 cells with BRD9 knockout. And Notch inhibition led to attenuation of cell growth and reduced migration and invasion in Caki‐2 cells. Overall, our results identified that BRD9 promotes the proliferation, migration and invasion of negative HIF‐2α ccRCC cells by targeting Notch signaling pathway and serve as a promising biomarker for negative HIF‐2α ccRCC. [ABSTRACT FROM AUTHOR]

Hypoxic environment is essential for chondrocyte maturation and longitudinal bone growth. Although hypoxia‐inducible factor 1 alpha (Hif‐1α) has been known as a key player for chondrocyte survival and function, the function of Hif‐2α in cartilage is mechanistically and clinically relevant but remains unknown. Here we demonstrated that Hif‐2α was a novel inhibitor of chondrocyte maturation through downregulation of Runx2 stability. Mechanistically, Hif‐2α binding to Runx2 inhibited chondrocyte maturation by Runx2 degradation through disrupting Runx2/Cbfβ complex formation. The Hif‐2α‐mediated‐Runx2 degradation could be rescued by Cbfβ transfection due to the increase of Runx2/Cbfβ complex formation. Consistently, mesenchymal cells derived from Hif‐2α heterozygous mice were more rapidly differentiated into hypertrophic chondrocytes than those of wild‐type mice in a micromass culture system. Collectively, these findings demonstrate that Hif‐2α is a novel inhibitor for chondrocyte maturation by disrupting Runx2/Cbfβ complex formation and consequential regulatory activity. [ABSTRACT FROM AUTHOR]

SHANK‐associated RH domain interacting protein (SHARPIN) plays an important role in carcinogenesis, as well as inflammation and immunity. Our study explored the effects and underlying mechanisms of SHARPIN in clear cell renal cell carcinoma (ccRCC). By analyzing The Cancer Genome Atlas database, we found that upregulated SHARPIN in patients with ccRCC led to a poor prognosis. Semiquantitative immunohistochemical analysis of clinical samples was carried out and the results suggested the positive association between SHARPIN and hypoxia‐induced factor‐2α (HIF‐2α). Von Hippel‐Lindau protein (pVHL) is a tumor suppressor that contributes to degrading HIF‐2α. Mechanically, SHARPIN promoted the ubiquitination and proteasomal degradation of pVHL, resulting in the sustained activation of HIF‐2α. The α and β domains of pVHL and ubiquitin‐like domain of SHARPIN are required for the interaction. The knockdown of SHARPIN effectively inhibited acquired sorafenib resistance in ccRCC cell lines and tumor growth in xenograft models. In conclusion, our work reveals a novel posttranslational regulation of SHARPIN on pVHL, indicating that SHARPIN could be a potential target for ccRCC treatment. [ABSTRACT FROM AUTHOR]

Background and Aim: The role of hypoxia‐inducible factor‐1α (HIF‐1α) and hypoxia‐inducible factor‐2α (HIF‐2α) has been implicated in the clinical prognosis of hepatocellular carcinoma (HCC), but the results remain controversial. We aim to investigate the association of HIF‐1α and HIF‐2α overexpression with the prognosis and clinicopathological features of HCC. Methods: A systematic search was conducted in PubMed, Embase, Scopus, Web of Science, and Cochrane Library until June 20, 2020. Meta‐analysis was conducted to generate combined HRs with 95% confidence intervals (CI) for overall survival (OS) and disease‐free survival (DFS). Odds ratios (ORs) with 95% CI were also derived by fixed or random effect model. Results: Twenty‐two studies involving 3238 patients were included. Combined data suggested that overexpression of HIF‐1α in HCC was not only correlated with poorer OS [HR = 1.75 (95% CI: 1.53–2.00)] and DFS [HR = 1.64 (95% CI: 1.34–2.00)] but was also positively associated with vascular invasion [OR = 1.83 (95% CI: 1.36–2.48)], tumor size [OR = 1.36 (95% CI: 1.12–1.66)], and tumor number [1.74 (95% CI: 1.34–2.25)]. In contrast, HIF‐2α overexpression was not associated with the prognosis and clinicopathological features of HCC. Conclusion: Our data provided compelling evidence of a worse prognosis of HCC in HIF‐1α overexpression patients but not HIF‐2α overexpression ones. [ABSTRACT FROM AUTHOR]

Background: The neural crest is a transient embryonic stem cell population. Hypoxia inducible factor (HIF)‐2α is associated with neural crest stem cell appearance and aggressiveness in tumors. However, little is known about its role in normal neural crest development. Results: Here, we show that HIF‐2α is expressed in trunk neural crest cells of human, murine, and avian embryos. Knockdown as well as overexpression of HIF‐2α in vivo causes developmental delays, induces proliferation, and self‐renewal capacity of neural crest cells while decreasing the proportion of neural crest cells that migrate ventrally to sympathoadrenal sites. Reflecting the in vivo phenotype, transcriptome changes after loss of HIF‐2α reveal enrichment of genes associated with cancer, invasion, epithelial‐to‐mesenchymal transition, and growth arrest. Conclusions: Taken together, these results suggest that expression levels of HIF‐2α must be strictly controlled during normal trunk neural crest development and that dysregulated levels affects several important features connected to stemness, migration, and development. [ABSTRACT FROM AUTHOR]

Oxidative stress and hypoxia are two opposite microenvironments involved in HCC metastasis. Thioredoxin (TXN) and hypoxia‐inducible factor 2α (HIF‐2α) are typical proteins involved in these two different microenvironments, respectively. How these two factors interact to influence the fate on tumor cells remains unknown. Hypoxia facilitated HCC cells withstood oxidative stress and eventually promoted HCC cells metastasis, in which TXN and HIF‐2α were mostly involved. Upregulation of TXN/HIF‐2α correlated with poor HCC prognosis and promoted HCC metastasis both in vitro and in vivo. Epithelial‐mesenchymal transition (EMT) process was involved in TXN/HIF‐2α‐enhanced invasiveness of HCC cells. Additionally, the stability and activity of HIF‐2α were precisely regulated by TXN via SUMOylation and acetylation, which contributed to HCC metastasis. Our data revealed that the redox protein TXN and HIF‐2α are both associated with HCC metastasis, and the fine regulation of TXN on HIF‐2α contributes essentially during the process of metastasis. Our study provides new insight into the interaction mechanism between hypoxia and oxidative stress and implies potential therapeutic benefits by targeting both TXN and HIF‐2α in the treatment of HCC metastasis. [ABSTRACT FROM AUTHOR]

Although Hif‐2α is a master regulator of catabolic factor expression in osteoarthritis development, Hif‐2α inhibitors remain undeveloped. The aim of this study was to determine whether Cirsium japonicum var. maackii (CJM) extract and one of its constituents, apigenin, could attenuate the Hif‐2α‐induced cartilage destruction implicated in osteoarthritis progression. In vitro and in vivo studies demonstrated that CJM reduced the IL‐1β‐, IL‐6, IL‐17‐ and TNF‐α‐induced up‐regulation of MMP3, MMP13, ADAMTS4, ADAMTS5 and COX‐2 and blocked osteoarthritis development in a destabilization of the medial meniscus mouse model. Activation of Hif‐2α, which directly up‐regulates MMP3, MMP13, ADAMTS4, IL‐6 and COX‐2 expression, is inhibited by CJM extract. Although cirsimarin, cirsimaritin and apigenin are components of CJM and can reduce inflammation, only apigenin effectively reduced Hif‐2α expression and inhibited Hif‐2α‐induced MMP3, MMP13, ADAMTS4, IL‐6 and COX‐2 expression in articular chondrocytes. IL‐1β induction of JNK phosphorylation and IκB degradation, representing a critical pathway for Hif‐2α expression, was completely blocked by apigenin in a concentration‐dependent manner. Collectively, these effects indicate that CJM and one of its most potent constituents, apigenin, can lead to the development of therapeutic agents for blocking osteoarthritis development as novel Hif‐2α inhibitors. [ABSTRACT FROM AUTHOR]

Extracellular ATP has been shown to play an important role in invasion and the epithelial‐mesenchymal transition (EMT) process in breast cancer; however, the mechanism is unclear. Here, by using a cDNA microarray, we demonstrated that extracellular ATP could stimulate hypoxia‐inducible factor (HIF) signaling and upregulate hypoxia‐inducible factor 1/2α (HIF‐1/2α) expression. After knocking down HIF‐1/2α using siRNA, we found that ATP‐driven invasion and EMT were significantly attenuated via HIF2A‐siRNA in breast cancer cells. By using ChIP assays, we revealed that the biological function of extracellular ATP in invasion and EMT process depended on HIF‐2α direct targets, among which lysyl oxidase‐like 2 (LOXL2) and matrix metalloproteinase‐9 (MMP‐9) mediated ATP‐driven invasion, and E‐cadherin and Snail mediated ATP‐driven EMT, respectively. In addition, using silver staining and mass spectrometry, we found that phosphoglycerate kinase 1 (PGK1) could interact with HIF‐2α and mediate ATP‐driven HIF‐2α upregulation. Furthermore, we demonstrated that expressions of HIF‐2α and its target proteins could be regulated via ATP by AKT‐PGK1 pathway. Using a Balb/c mice model, we illustrated the function of HIF‐2α in promoting tumor growth and metastasis in vivo. Moreover, by exploring online databases, we found that molecules involved in ATP‐HIF‐2α signaling were highly expressed in human breast carcinoma tissues and were associated with poor prognosis. Altogether, these findings suggest that extracellular ATP could promote breast carcinoma invasion and EMT via HIF‐2α signaling, which may be a potential target for future anti–metastasis therapy. [ABSTRACT FROM AUTHOR]

An imbalance of branched‐chain amino acids (BCAAs) in the brain may result in neuropathological conditions, such as autism spectrum disorders. The L‐type amino acid transporter 1 (LAT1), encoded by the solute carrier transporter 7a5 (Slc7a5) gene, is critical for maintaining normal levels of BCAAs in the brain. However, our understanding of the mechanisms that regulate the expression of LAT1/Slc7a5 in neurons is currently limited. Here, we demonstrate that hypoxic conditions result in upregulated expression of Slc7a5 in differentiated neuronal cells (Neuro2A cells induced to differentiate using all‐trans retinoic acid). Mechanistically, hypoxia‐induced expression of Slc7a5 is markedly reduced by short hairpin RNA (shRNA)‐mediated knockdown of hypoxia‐inducible factor 2α (HIF‐2α), but not by shRNA targeting HIF‐1α, in differentiated neuronal cells. Moreover, hypoxia increased the binding of HIF‐2α to the proximal promoter of Slc7a5 in differentiated neuronal cells. These results indicate that hypoxia directly enhances the recruitment of HIF‐2α to the proximal promoter of Slc7a5, resulting in its upregulated expression in differentiated neuronal cells. These findings indicate that Slc7a5 may be a novel gene responsive to hypoxia in a HIF‐2α‐dependent manner in differentiated neuronal cells. The expression of solute carrier transporter 7a5 (Slc7a5) is upregulated by hypoxia through hypoxia‐inducible factor 2α (HIF‐2α) but not by HIF‐1α in differentiated neuronal cells. Hypoxia directly enhances the recruitment of HIF‐2α to the proximal promoter of Slc7a5, resulting in its upregulated expression in differentiated neuronal cells. [ABSTRACT FROM AUTHOR]

Hypoxia-inducible factor-2α ( HIF-2α) plays an important role in increasing cancer progression and distant metastasis in a variety of tumour types. We aimed to investigate its biological function and clinical significance in human pancreatic ductal adenocarcinoma ( PDAC). A total of 283 paired PDAC tissues and adjacent normal tissues were collected from patients who underwent surgery or biopsy at Sun Yat-sen Memorial Hospital between February 2004 and October 2016. In this study, we noted that HIF-2α expression was significantly up-regulated in PDAC, positively associated with disease stage, lymph-node metastasis and patient survival, and identified as an independent prognostic factor of PDAC patients. We demonstrated that HIF-2α silencing could reduce proliferation, migration and invasion of PDAC cells in vitro. The similar effect on growth was demonstrated in vivo. Furthermore, we noted that knock-down of HIF-2α significantly decreased the expression of glutamate oxaloacetate transaminase 1 ( GOT1). Importantly, we confirmed that the PI3K/ mTORC2 pathway promoted GOT1 expression by targeting HIF-2α. Our study validated HIF-2α was an important factor in PDAC progression and poor prognosis and may promote non-canonical glutamine metabolism via activation of PI3K/ mTORC2 pathway. Targeting HIF-2α represents a novel prognostic biomarker and therapeutic target for patients with PDAC. [ABSTRACT FROM AUTHOR]

Metastasis is a serious risk that may occur during the treatment of hepatocellular carcinoma ( HCC), preventing many patients from being surgical candidates and contributing to poor prognosis. Hypoxia has been proved an important factor of metastasis through the epithelial-mesenchymal transition ( EMT) pathway. Acetyl-CoA synthase 2 ( ACSS2) provides an acetyl group for the acetylation of hypoxia-inducible factor ( HIF)-2α, and this epigenetic modification affects the activity of HIF-2α and the subsequent EMT process. Here, we showed that ACSS2 expression was negatively correlated with HCC malignancy. Knockdown of ACSS2 increased the invasion and migration ability of HCC cells and promoted EMT without increasing the total protein level of HIF-2α, even in hypoxic conditions. The immunoprecipitation assay revealed downregulated acetylation levels of HIF-2α after ACSS2 knockdown in hypoxic conditions, which resulted in enhanced HIF-2α activity. Finally, decreased expression of ACSS2 was found to be related to advanced stage and poor overall survival and disease-free survival rates in a cohort of patients with HCC. In conclusion, ACSS2 plays an important role in the acetylation process of HIF-2α, which effectively modifies the activity of HIF-2α under hypoxic conditions and greatly impacts on the prognosis of patients with HCC. [ABSTRACT FROM AUTHOR]

Mitochondrial dysfunction plays an important role in obesity-induced cardiac impairment. SIRT3 is a mitochondrial protein associated with increased human life span and metabolism. This study investigated the functional role of SIRT3 in obesity-induced cardiac dysfunction. Wild-type ( WT) and SIRT3 knockout ( KO) mice were fed a normal diet ( ND) or high-fat diet ( HFD) for 16 weeks. Body weight, fasting glucose levels, reactive oxygen species ( ROS) levels, myocardial capillary density, cardiac function and expression of hypoxia-inducible factor ( HIF)-1α/-2α were assessed. HFD resulted in a significant reduction in SIRT3 expression in the heart. Both HFD and SIRT3 KO mice showed increased ROS formation, impaired HIF signalling and reduced capillary density in the heart. HFD induced cardiac hypertrophy and impaired cardiac function. SIRT3 KO mice fed HFD showed greater ROS production and a further reduction in cardiac function compared to SIRT3 KO mice on ND. Thus, the adverse effects of HFD on cardiac function were not attributable to SIRT3 loss alone. However, HFD did not further reduce capillary density in SIRT3 KO hearts, implicating SIRT3 loss in HFD-induced capillary rarefaction. Our study demonstrates the importance of SIRT3 in preserving heart function and capillary density in the setting of obesity. Thus, SIRT3 may be a potential therapeutic target for obesity-induced heart failure. [ABSTRACT FROM AUTHOR]

ABSTRACT We investigated the feasibility of the intra-articular injection of resveratrol for preventing the progression of existing cartilage degeneration in a mouse model of osteoarthritis (OA). The effects of resveratrol on the expression of silent information regulator 2 type 1 (SIRT1), hypoxia-inducible factor-2α (HIF-2α) and catabolic factors in OA cartilage was explored. OA was induced in the mouse knee via destabilization of the medial meniscus (DMM). Resveratrol was injected weekly into the operated knee beginning 4 weeks after surgery. The OA phenotype was evaluated via histological and immunohistochemical analyses at 8 weeks after DMM. Western blot analysis was performed to identify whether resveratrol modulated the interleukin (IL)-1β-induced expression of HIF-2α in human chondrocytes. Histologically, resveratrol treatment preserved the structural homeostasis of the articular cartilage and the subchondral bone. Following resveratrol injection, the expression of collagen type II was retained, but the expression of inducible nitric oxide synthase and matrix metalloproteinase-13 was reduced in OA cartilage. Moreover, the administration of resveratrol significantly induced the activation of SIRT1 and the inhibition of HIF-2α expression in mouse OA cartilage and in IL-1β-treated human chondrocytes. These findings indicate that the intra-articular injection of resveratrol significantly prevents the destruction of OA cartilage by activating SIRT1 and thereby suppressing the expression of HIF-2α and catabolic factors. © 2015 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 33:1061-1070, 2015. [ABSTRACT FROM AUTHOR]

Glioblastoma multiforme (GBM) is the deadliest form of primary brain cancer. Several reports have indicated aberrant levels of βIII-tubulin (βIII-t) in human GBM. βIII-t overexpression was linked to increasing malignancy in glial tumors and described to determine the onset of resistance to chemotherapy. Furthermore, a linkage was suggested between the induction of βIII-t expression and hypoxia, a hallmark of GBM. We investigated the role of hypoxia-inducible factor (HIF)-1α and HIF-2α in the regulation of the βIII-t gene ( TUBB3) in GBM cells cultured in either normoxia or hypoxia. We report for the first time that HIF-2α, but not HIF-1α, is involved in hypoxia-induced βIII-t expression in GBM cells. By gene-reporter experiments and site-directed mutagenesis, we found that two overlapping hypoxia response elements located in the 3′ UTR of the gene were involved in the activation of TUBB3. This occurred through an enhanced binding of HIF-2α to the 3′ region, as revealed by an electrophoretic mobility shift assay. Conversely, the promoter of TUBB3 was shown to be inactive. In addition, we observed that HIF-1α exhibits a repressive effect on βIII-t expression in cells cultured in normoxia. These results show that both HIF-α isoforms have opposing effects on βIII-t expression in GBM cells. Finally, we observed that hypoxia-induced βIII-t expression is well correlated with the kinetics of HIF-2α protein stabilization. The evidence for a direct linkage between HIF-2α and increased expression of βIII-t by hypoxia suggests that an anti-HIF-2α strategy (i.e. by downregulating βIII-t) could be of potential interest for improving the treatment of GBM. [ABSTRACT FROM AUTHOR]

Background Cardiovascular patients suffer from reduced blood flow leading to ischaemia and impaired tissue metabolism. Unfortunately, an increasing group of elderly patients cannot be treated with current revascularization methods. Thus, new treatment strategies are urgently needed. Hypoxia-inducible factors ( HIFs) upregulate the expression of angiogenic mediators together with genes involved in energy metabolism and recovery of ischaemic tissues. Especially, HIF-2α is a novel factor, and only limited information is available about its therapeutic potential. Methods Gene transfers with adenoviral HIF-1α and HIF-2α were performed into the mouse heart and rabbit ischaemic hindlimbs. Angiogenesis was evaluated by histology. Left ventricle function was analysed with echocardiography. Perfusion in rabbit skeletal muscles and energy recovery after electrical stimulation-induced exercise were measured with ultrasound and 31 P-magnetic resonance spectroscopy (31 P- MRS), respectively. Results HIF-1α and HIF-2α gene transfers increased capillary size up to fivefold in myocardium and ischaemic skeletal muscles. Perfusion in skeletal muscles was increased by fourfold without oedema. Especially, Ad HIF-1α enhanced the recovery of ischaemic muscles from electrical stimulation-induced energy depletion. Special characteristic of HIF-2α gene transfer was a strong capillary growth in muscle connective tissue and that HIF-2α gene transfer maintained left ventricle function. Conclusions We conclude that both Ad HIF-1α and Ad HIF-2α gene transfers induced beneficial angiogenesis in vivo. Transient moderate increases in angiogenesis improved energy recovery after exercise in ischaemic muscles. This study shows for the first time that a moderate increase in angiogenesis is enough to improve tissue energy metabolism, which is potentially a very useful feature for cardiovascular gene therapy. [ABSTRACT FROM AUTHOR]

Abstract: Prox1 encodes a homeobox transcription factor critical to organ development, but its regulation is poorly understood. Here, we show that Prox1 expression is induced by hypoxia, and controlled by a hypoxia-response element (HRE) at the Prox1 promoter/regulatory region and HIF-1α/HIF-2α. EMSA and ChIP assays demonstrated the direct interaction of the HRE with HIF-1α or HIF-2α. Overexpression of HIF-1α or HIF-2α increased activation of the Prox1 promoter, whereas knockdown of HIF-1α or HIF-2α inhibited the activation. These data reveal a novel molecular mechanism for regulation of Prox1 expression in response to hypoxia and provide new insights into Prox1-controlled processes such as lymphangiogenesis. [Copyright &y& Elsevier]

Osteoarthritis (OA) is a common disease with a genetic component for its etiology. Recently, a genetic association of a single nucleotide polymorphism (SNP), rs17039192 in HIF-2α with knee OA has been reported in a Japanese population; however, controversy exits for its replication and a role of HIF-2α in OA. This study aimed to evaluate the association of the SNP by a large-scale replication study. A total of 8,457 subjects (3,129 OA cases and 5,328 controls) from seven independent cohorts from six countries (Japan, China, Taiwan, Korea, Greece, and Australia) were recruited and genotyped. The association of rs17039192 with knee OA was evaluated by meta-analyses. The association of the HIF-2α SNP was not replicated in any of the populations. Contrary to the previous report, the odds ratios (ORs) of the risk allele frequency were all less than 1. A combined analysis for the seven populations also showed no replication of the association (OR = 0.91, 95% confidence interval = 0.81-1.03). Our large-scale meta-analysis showed that the association of rs17039192 in HIF-2α with knee OA is negative. The significance of HIF-2α in human OA (idiopathic OA as a common disease) should be further evaluated carefully. © 2012 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 30:1244-1248, 2012 [ABSTRACT FROM AUTHOR]

Abstract: The hypoxia-inducible factors HIF-1 and HIF-2 are primarily regulated via stabilization of their respective α-subunits under hypoxic conditions. Previously, compensatory upregulation of one HIF-α-subunit upon depletion of the other α-subunit was described, yet the underlying mechanism remained elusive. Here we provide evidence that enhanced HIF-1α protein expression in HIF-2α knockdown (k/d) cells neither results from elevated HIF-1α mRNA expression, nor from increased HIF-1α protein stability. Instead, we identify enhanced HIF-1α translation as molecular mechanism. Moreover, we found elevated levels of the RNA-binding protein HuR and provide evidence that HuR is critical for the compensatory HIF-1α regulation in HIF-2α k/d cells. [Copyright &y& Elsevier]

Abstract: Accumulating evidence suggests that hypoxia-inducible factor-2 (HIF-2) is important for the cellular response to hypoxia. However, it is not clear how HIF-2 is regulated under hypoxic conditions. We investigated kinetic changes in redox status and HIF-2α accumulation in hypoxic SH-SY5Y cells. Our results demonstrated that hypoxia caused a reducing environment and increased HIF-2α protein levels. Experiments with redox modulations (N-acetylcysteine and l-buthionine sulfoximine) confirmed that a reducing environment induced HIF-2α accumulation while an oxidizing environment decreased it. In addition, experiments with SOD mimic, catalase, and exogenous H2O2 provided evidence that the presence of H2O2 down-regulated the amount of HIF-2α protein. This study offers novel evidence supporting redox status regulation of HIF-2α accumulation under hypoxic conditions. [Copyright &y& Elsevier]

Aims : The cellular response to hypoxia includes the hypoxia inducible factor (HIF)-induced transcription of genes involved in diverse processes such as glycolysis, angiogenesis and the growth of experimental tumours. Regulation of the level of hypoxia inducible factors 1α and 2α (HIF-1α and HIF-2α) is a primary determinant of HIF activity. Recent biochemical and candidate gene approach studies have led to the discovery of three HIF-regulatory prolyl hydroxylases, PHD-1, -2 and -3 and an asparaginyl hydroxylase, also known as FIH (factor inhibiting HIF). In this study, we raised and characterized monoclonal antibodies against PHD-1, PHD-2, PHD-3 and FIH. Methods and results : Immunohistochemistry of normal tissues with these monoclonal antibodies demonstrated a wide distribution in epithelial cells, stromal cells and leucocytes, with cytoplasmic staining predominating over nuclear staining. A preliminary study of tumours showed variable staining in tumour, stromal and inflammatory cells. While all tumour types showed some positive staining with each antibody, the overall pattern suggested a slight decrease in the amount of staining seen with PHD-1, -2 and -3 and an increase in FIH staining in neoplasia compared with corresponding normal tissues. Conclusions : These monoclonal antibodies will allow further larger scale studies to determine the significance of PHD and FIH expression in neoplasia. [ABSTRACT FROM AUTHOR]

Hypoxia-inducible factor-2α (HIF-2α) plays an important role in increasing cancer progression and distant metastasis in a variety of tumour types. We aimed to investigate its biological function and clinical significance in human pancreatic ductal adenocarcinoma (PDAC). A total of 283 paired PDAC tissues and adjacent normal tissues were collected from patients who underwent surgery or biopsy at Sun Yat-sen Memorial Hospital between February 2004 and October 2016. In this study, we noted that HIF-2α expression was significantly up-regulated in PDAC, positively associated with disease stage, lymph-node metastasis and patient survival, and identified as an independent prognostic factor of PDAC patients. We demonstrated that HIF-2α silencing could reduce proliferation, migration and invasion of PDAC cells in vitro. The similar effect on growth was demonstrated in vivo. Furthermore, we noted that knock-down of HIF-2α significantly decreased the expression of glutamate oxaloacetate transaminase 1 (GOT1). Importantly, we confirmed that the PI3K/mTORC2 pathway promoted GOT1 expression by targeting HIF-2α. Our study validated HIF-2α was an important factor in PDAC progression and poor prognosis and may promote non-canonical glutamine metabolism via activation of PI3K/mTORC2 pathway. Targeting HIF-2α represents a novel prognostic biomarker and therapeutic target for patients with PDAC., (© 2017 The Authors. Journal of Cellular and Molecular Medicine published by John Wiley & Sons Ltd and Foundation for Cellular and Molecular Medicine.)

Please cite this paper as: Gourvas V, Sifakis S, Dalpa E, Soulitzis N, Koukoura O, Spandidos D. Reduced placental prolyl hydroxylase 3 mRNA expression in pregnancies affected by fetal growth restriction. BJOG 2010;117:1635-1642. To investigate the role of the hypoxia-inducible factor (HIF) pathway in fetal growth restriction (FGR). A case-control study. Research laboratory and gynaecology clinic. Twenty placentas from normal pregnancies and 20 from FGR pregnancies. RNA extraction, cDNA synthesis, quantitative real-time polymerase chain reaction (qRT-PCR) assay, statistical analysis. mRNA expression of HIF-1α, HIF-2α and HIF-β (ARNT), along with prolyl hydroxylase domain 3 (PHD3), which leads to proteasomal degradation of HIF-α subunits. No statistically significant differences in the transcription levels of ARNT and HIF-2α were found between FGR and normal placentas. By contrast, PHD3 and HIF-1α mRNA were downregulated in FGR placentas. PHD3 mRNA expression was associated with gestational age at delivery ( P = 0.008), birthweight centile ( P = 0.029) and abnormal umbilical artery (UA) Doppler measurements ( P = 0.034). As PHD3 regulates the HIF-mediated hypoxic response in FGR, we deduce that fetal adaptation to hypoxia ranges from impaired to adequate, as observed by the gradient of PHD3 downregulation in relation to the severity of FGR. [ABSTRACT FROM AUTHOR]