Discovery of novel methionine adenosyltransferase 2A (MAT2A) allosteric inhibitors by structure-based virtual screening.

Methionine adenosyltransferase 2A (MAT2A) has been indicated as a drug target for oncology indications. Clinical trials with MAT2A inhibitors are currently on-going. Here, a structure-based virtual screening campaign was performed on the commercially available chemical space which yielded two novel MAT2A-inhibitor chemical series. The binding modes of the compounds were confirmed with X-ray crystallography. Both series have acceptable physicochemical properties and show nanomolar activity in the biochemical MAT2A inhibition assay and single-digit micromolar activity in the proliferation assay (MTAP -/- cell line). The identified compounds and the relating structural data could be helpful in related drug discovery projects.

MYO10-filopodia support basement membranes at pre-invasive tumor boundaries.

Ductal carcinoma in situ (DCIS) is a pre-invasive stage of breast cancer. During invasion, the encapsulating DCIS basement membrane (BM) is compromised, and tumor cells invade the surrounding stroma. The mechanisms that regulate functional epithelial BMs in vivo are poorly understood. Myosin-X (MYO10) is a filopodia-inducing protein associated with metastasis and poor clinical outcome in invasive breast cancer (IBC). We identify elevated MYO10 expression in human DCIS and IBC, and this suggests links with disease progression. MYO10 promotes filopodia formation and cell invasion in vitro and cancer-cell dissemination from progressively invasive human DCIS xenografts. However, MYO10-depleted xenografts are more invasive. These lesions exhibit compromised BMs, poorly defined borders, and increased cancer-cell dispersal and EMT-marker-positive cells. In addition, cancer spheroids are dependent on MYO10-filopodia to generate a near-continuous extracellular matrix boundary. Thus, MYO10 is protective in early-stage breast cancer, correlating with tumor-limiting BMs, and pro-invasive at later stages, facilitating cancer-cell dissemination.

Sustainable Production of Novel Oleogels Valorizing Microbial Oil Rich in Carotenoids Derived from Spent Coffee Grounds.

Sustainable food systems that employ renewable resources without competition with the food chain are drivers for the bioeconomy era. This study reports the valorization of microwave-pretreated spent coffee grounds (SCGs) to produce oleogels rich in bioactive compounds. Microbial oil rich in carotenoids (MOC) was produced under batch fermentation of Rhodosporidium toruloides using SCG enzymatic hydrolysates. Candelilla wax (CLW) could structure MOC and sunflower oil at a 3.3-fold lower concentration than that of carnauba wax (CBW). MOC-based oleogels with 10% CBW and 3% CLW showed an elastic-dominant and gel-like structure (tan δ ≪ 1), providing gelation and oil binding capacity (>95%). Dendritic structures of CBW-based oleogels and evenly distributed rod-like crystals of CLW-based ones were observed via polarized light microscopy. MOC-based oleogels exhibited similar Fourier-transform infrared spectroscopy spectra. X-ray diffractograms of oleogels were distinguished by the oil type that presented ß'-type polymorphism. MOC-based oleogels could be applied in confectionary products and spreads as substitutes for trans fatty acids, reformulating fat-containing food products.

Circulating tumor necrosis factor-α levels in non-alcoholic fatty liver disease: A systematic review and a meta-analysis.

BACKGROUND AND AIM: To synthesize data on circulating tumor necrosis factor (TNF)-α levels between patients with histologically confirmed non-alcoholic fatty liver disease (NAFLD) (simple steatosis or non-alcoholic fatty liver [NAFL] and/or non-alcoholic steatohepatitis [NASH]) and controls. METHODS: We performed a systematic search in PubMed, Scopus, and Cochrane Library. Fifty-six studies, published between 2003 and 2019, were finally included, reporting data from 5848 individuals (1634 controls and 4214 NAFLD patients). RESULTS: Higher circulating TNF-α levels were observed in NAFLD patients than controls (standardized mean difference [SMD] 0.84; 95% confidence interval [95% CI] 0.59-1.09), NAFL patients than controls (SMD 0.56; 95% CI 0.27-0.85), NASH patients than controls (SMD 0.93; 95% CI 0.64-1.22), and NASH than NAFL patients (SMD 0.31; 95% CI 0.16-0.46). There were only minimal changes in the comparisons between groups after excluding studies with morbidly obese populations (n = 11), or pediatric/adolescent populations (n = 6), or other than enzyme-linked immunosorbent assay method of TNF-α measurement (n = 8). There was high heterogeneity among studies in all comparisons, which was not essentially affected after sensitivity analyses. The meta-regression analysis revealed that the male ratio was positively associated with TNF-α SMD in the comparison between patients with NASH and NAFL (beta = 0.809; 95% CI 0.052-1.566) and accounted for 36% (P = 0.037) of the heterogeneity in this pair of comparison. TNF-α SMD was not associated with age, body mass index, and alanine aminotransferase in any pair of comparisons. CONCLUSIONS: Circulating TNF-α levels were higher in patients with NAFLD compared with controls. Higher levels of circulating TNF-α were also associated with the severity of NAFLD.

SORLA regulates endosomal trafficking and oncogenic fitness of HER2.

The human epidermal growth factor receptor 2 (HER2) is an oncogene targeted by several kinase inhibitors and therapeutic antibodies. While the endosomal trafficking of many other receptor tyrosine kinases is known to regulate their oncogenic signalling, the prevailing view on HER2 is that this receptor is predominantly retained on the cell surface. Here, we find that sortilin-related receptor 1 (SORLA; SORL1) co-precipitates with HER2 in cancer cells and regulates HER2 subcellular distribution by promoting recycling of the endosomal receptor back to the plasma membrane. SORLA protein levels in cancer cell lines and bladder cancers correlates with HER2 levels. Depletion of SORLA triggers HER2 targeting to late endosomal/lysosomal compartments and impairs HER2-driven signalling and in vivo tumour growth. SORLA silencing also disrupts normal lysosome function and sensitizes anti-HER2 therapy sensitive and resistant cancer cells to lysosome-targeting cationic amphiphilic drugs. These findings reveal potentially important SORLA-dependent endosomal trafficking-linked vulnerabilities in HER2-driven cancers.

Tensins: Bridging AMP-Activated Protein Kinase with Integrin Activation.

Integrin activation is essential for cell adhesion and for connecting the extracellular matrix to the actin cytoskeleton. Thus, inappropriate integrin activation has been linked to several diseases, including cancer. Recent insights demonstrate that the main fibrillar adhesion component tensin maintains ß1-integrin active in these mature adhesions. Depletion or silencing of AMP-activated protein kinase (AMPK), the energy sensor involved in maintaining the energy balance of the cell, enhances integrin activity by increasing the expression of tensin and thereby promoting cell adhesion, matrix formation, and mechanotransduction. Here, we discuss the role of tensin and AMPK in the regulation of integrin activity and integrin-dependent processes and their implication in diseases such as cancer and tissue fibrosis.

SHANK proteins limit integrin activation by directly interacting with Rap1 and R-Ras.

SHANK3, a synaptic scaffold protein and actin regulator, is widely expressed outside of the central nervous system with predominantly unknown function. Solving the structure of the SHANK3 N-terminal region revealed that the SPN domain is an unexpected Ras-association domain with high affinity for GTP-bound Ras and Rap G-proteins. The role of Rap1 in integrin activation is well established but the mechanisms to antagonize it remain largely unknown. Here, we show that SHANK1 and SHANK3 act as integrin activation inhibitors by sequestering active Rap1 and R-Ras via the SPN domain and thus limiting their bioavailability at the plasma membrane. Consistently, SHANK3 silencing triggers increased plasma membrane Rap1 activity, cell spreading, migration and invasion. Autism-related mutations within the SHANK3 SPN domain (R12C and L68P) disrupt G-protein interaction and fail to counteract integrin activation along the Rap1-RIAM-talin axis in cancer cells and neurons. Altogether, we establish SHANKs as critical regulators of G-protein signalling and integrin-dependent processes.

SHARPIN regulates collagen architecture and ductal outgrowth in the developing mouse mammary gland.

SHARPIN is a widely expressed multifunctional protein implicated in cancer, inflammation, linear ubiquitination and integrin activity inhibition; however, its contribution to epithelial homeostasis remains poorly understood. Here, we examined the role of SHARPIN in mammary gland development, a process strongly regulated by epithelial-stromal interactions. Mice lacking SHARPIN expression in all cells (Sharpincpdm), and mice with a stromal (S100a4-Cre) deletion of Sharpin, have reduced mammary ductal outgrowth during puberty. In contrast, Sharpincpdm mammary epithelial cells transplanted in vivo into wild-type stroma, fully repopulate the mammary gland fat pad, undergo unperturbed ductal outgrowth and terminal differentiation. Thus, SHARPIN is required in mammary gland stroma during development. Accordingly, stroma adjacent to invading mammary ducts of Sharpincpdm mice displayed reduced collagen arrangement and extracellular matrix (ECM) stiffness. Moreover, Sharpincpdm mammary gland stromal fibroblasts demonstrated defects in collagen fibre assembly, collagen contraction and degradation in vitro Together, these data imply that SHARPIN regulates the normal invasive mammary gland branching morphogenesis in an epithelial cell extrinsic manner by controlling the organisation of the stromal ECM.

L-type calcium channels regulate filopodia stability and cancer cell invasion downstream of integrin signalling.

Mounting in vitro, in vivo and clinical evidence suggest an important role for filopodia in driving cancer cell invasion. Using a high-throughput microscopic-based drug screen, we identify FDA-approved calcium channel blockers (CCBs) as potent inhibitors of filopodia formation in cancer cells. Unexpectedly, we discover that L-type calcium channels are functional and frequently expressed in cancer cells suggesting a previously unappreciated role for these channels during tumorigenesis. We further demonstrate that, at filopodia, L-type calcium channels are activated by integrin inside-out signalling, integrin activation and Src. Moreover, L-type calcium channels promote filopodia stability and maturation into talin-rich adhesions through the spatially restricted regulation of calcium entry and subsequent activation of the protease calpain-1. Altogether we uncover a novel and clinically relevant signalling pathway that regulates filopodia formation in cancer cells and propose that cycles of filopodia stabilization, followed by maturation into focal adhesions, directs cancer cell migration and invasion.

Normal stroma suppresses cancer cell proliferation via mechanosensitive regulation of JMJD1a-mediated transcription.

Tissue homeostasis is dependent on the controlled localization of specific cell types and the correct composition of the extracellular stroma. While the role of the cancer stroma in tumour progression has been well characterized, the specific contribution of the matrix itself is unknown. Furthermore, the mechanisms enabling normal-not cancer-stroma to provide tumour-suppressive signals and act as an antitumorigenic barrier are poorly understood. Here we show that extracellular matrix (ECM) generated by normal fibroblasts (NFs) is softer than the CAF matrix, and its physical and structural features regulate cancer cell proliferation. We find that normal ECM triggers downregulation and nuclear exit of the histone demethylase JMJD1a resulting in the epigenetic growth restriction of carcinoma cells. Interestingly, JMJD1a positively regulates transcription of many target genes, including YAP/TAZ (WWTR1), and therefore gene expression in a stiffness-dependent manner. Thus, normal stromal restricts cancer cell proliferation through JMJD1a-dependent modulation of gene expression.

Metabolic control of the cell cycle.

Cell division is a metabolically demanding process, requiring the production of large amounts of energy and biomass. Not surprisingly therefore, a cell's decision to initiate division is co-determined by its metabolic status and the availability of nutrients. Emerging evidence reveals that metabolism is not only undergoing substantial changes during the cell cycle, but it is becoming equally clear that metabolism regulates cell cycle progression. Here, we overview the emerging role of those metabolic pathways that have been best characterized to change during or influence cell cycle progression. We then studied how Notch signaling, a key angiogenic pathway that inhibits endothelial cell (EC) proliferation, controls EC metabolism (glycolysis) during the cell cycle.

Tumor vessel normalization by chloroquine independent of autophagy.

Chloroquine (CQ) has been evaluated as an autophagy blocker for cancer treatment, but it is unknown if it acts solely by inhibiting cancer cell autophagy. We report that CQ reduced tumor growth but improved the tumor milieu. By normalizing tumor vessel structure and function and increasing perfusion, CQ reduced hypoxia, cancer cell invasion, and metastasis, while improving chemotherapy delivery and response. Inhibiting autophagy in cancer cells or endothelial cells (ECs) failed to induce such effects. CQ's vessel normalization activity relied mainly on alterations of endosomal Notch1 trafficking and signaling in ECs and was abrogated by Notch1 deletion in ECs in vivo. Thus, autophagy-independent vessel normalization by CQ restrains tumor invasion and metastasis while improving chemotherapy, supporting the use of CQ for anticancer treatment.

Differences in telomerase activity between colon and rectal cancer.

BACKGROUND: Colorectal cancer is one of the most common cancers and the third leading cause of cancer death in both sexes. The disease progresses as a multistep process and is associated with genetic alterations. One of the characteristic features of cancer is telomerase activation. We sought to evaluate the differences in telomerase activity between colon cancer and adjacent normal tissue and to correlate the differences in telomerase activity between different locations with clinicopathological factors and survival. METHODS: Matched colon tumour samples and adjacent normal mucosa samples 10 cm away from the tumour were collected during colectomy. We assessed telomerase activity using real time polymerase chain reaction. Several pathological characteristics of tumours, including p53, Ki-67, p21, bcl2 and MLH1 expression were also studied. RESULTS: We collected samples from 49 patients. There was a significantly higher telomerase activity in colon cancer tissue than normal tissue. Adenocarcinomas of the right colon express significantly higher telomerase than left-side cancers. Colon cancers and their adjacent normal tissue had significantly more telomerase and were more positive to MLH1 than rectal cancers. The expression of p53 negatively correlated to telomerase activity and was linked to better patient survival. CONCLUSION: Colon and rectal cancers seem to have different telomerase and MLH1 profiles, and this could be another factor for their different biologic and clinical behaviour and progression. These results support the idea that the large bowel cannot be considered a uniform organ, at least in the biology of cancer.

CONTEXTE: Le cancer colorectal est l'un des cancers les plus répandus; il arrive au troisième rang des décès attribuables au cancer chez les hommes et les femmes. La maladie progresse en plusieurs étapes et est associée à des anomalies génétiques. L'une des principales caractéristiques du cancer est l'activation de la télomérase. Nous avons voulu évaluer les différences d'activité de la télomérase entre les tissus touchés par le cancer du côlon et les tissus adjacents normaux afin d'établir une corrélation entre les différences d'activité de la télomérase selon la localisation d'une part et les facteurs clinicopathologiques et la survie d'autre part. MÉTHODES: Lors de colectomies, nous avons recueilli des échantillons tissulaires jumelés de tumeur du côlon et de muqueuse adjacente normale à 10 cm du foyer tumoral. Nous avons mesuré l'activité de la télomérase à l'aide de la réaction en chaîne de la polymérase en temps réel. Plusieurs caractéristiques pathologiques des tumeurs ont aussi été analysées, y compris l'expression des gènes p53, Ki-67, p21, bcl2 et MLH1. RÉSULTATS: Nous avons recueilli des échantillons auprès de 49 patients. Nous avons noté une activité nettement plus intense de la télomérase dans les tissus touchés par le cancer du côlon que dans les tissus normaux. Les adénocarcinomes du côlon ascendant expriment une activité de la télomérase significativement plus intense que les cancers du côlon descendant. Les cancers du côlon et les tissus adjacents normaux présentaient une activité significativement plus intense de la télomérase et étaient plus souvent positifs à l'égard du MLH1 comparativement aux cancers rectaux. L'expression du p53 a été en corrélation négative avec l'activité de la télomérase et a été associée à une meilleure survie chez les patients. CONCLUSION: Les cancers du côlon et du rectum semblent avoir des profils différents au plan de la télomérase et du gène MLH1. Ce facteur pourrait entre autre expliquer leur comportement et leur progression biologiques et cliniques distincts. Ces résultats appuient l'hypothèse selon laquelle le côlon ne peut être considéré comme un organe uniforme, du moins en ce qui concerne la biologie du cancer.

Effects of octreotide and insulin on colon cancer cellular proliferation and correlation with hTERT activity.

Peptide hormone somatostatin and its receptors have a wide range of physiological functions and play a role in the treatment of numerous human diseases, including colorectal cancer. Octreotide, a synthetic somatostatin-analog peptide, inhibits growth of colonic cancer cells primarily by binding to G-protein coupled receptors and elicits cellular responses through second-messenger systems. Insulin also initiates mitogenic signals in certain cell types. The objective of the present study was to explore the effects of octreotide with or without insulin treatment, on Caco-2 and HT-29 human colon-cancer cell proliferation and to correlate their effects with the activation of telomerase reverse transcriptase (hTERT). The involvement of protein tyrosine phosphatases in the regulation of the anti-proliferative effect of octreotide was also evaluated. Sodium orthovanadate was used to reverse the anti- proliferative effect of octreotide. Telomerase activity was determined for each time point under octreotide and/or insulin treatment. Elevated expression of sst1, sst2 and sst5 was confirmed in both cell lines by RT-PCR. Immunocytochemistry detected sst1, sst2A, sst2B, sst3, sst4 and sst5 protein expression in the membranes of both cell lines. Octreotide inhibited the proliferation of Caco-2 and HT-29 cells in a time and dose-dependent manner. Insulin exerted proliferative effects in Caco-2 cells and octreotide reversed its effect in both cell lines. Sodium orthovanadate suppressed the anti-proliferative effect of octreotide both in Caco-2 and HT-29 cells. Telomerase activity was significantly reduced when Caco-2 cells were exposed to octreotide, under serum-free cultured medium. On the other hand, telomerase attenuation after octreotide treatment could not counteract the actions of insulin on both cells. Our data indicate that the use of octreotide could provide a possible therapeutic approach to the management of certain patients who suffer from colon cancer.

Partial and transient reduction of glycolysis by PFKFB3 blockade reduces pathological angiogenesis.

Strategies targeting pathological angiogenesis have focused primarily on blocking vascular endothelial growth factor (VEGF), but resistance and insufficient efficacy limit their success, mandating alternative antiangiogenic strategies. We recently provided genetic evidence that the glycolytic activator phosphofructokinase-2/fructose-2,6-bisphosphatase 3 (PFKFB3) promotes vessel formation but did not explore the antiangiogenic therapeutic potential of PFKFB3 blockade. Here, we show that blockade of PFKFB3 by the small molecule 3-(3-pyridinyl)-1-(4-pyridinyl)-2-propen-1-one (3PO) reduced vessel sprouting in endothelial cell (EC) spheroids, zebrafish embryos, and the postnatal mouse retina by inhibiting EC proliferation and migration. 3PO also suppressed vascular hyperbranching induced by inhibition of Notch or VEGF receptor 1 (VEGFR1) and amplified the antiangiogenic effect of VEGF blockade. Although 3PO reduced glycolysis only partially and transiently in vivo, this sufficed to decrease pathological neovascularization in ocular and inflammatory models. These insights may offer therapeutic antiangiogenic opportunities.

Role of PFKFB3-driven glycolysis in vessel sprouting.

Vessel sprouting by migrating tip and proliferating stalk endothelial cells (ECs) is controlled by genetic signals (such as Notch), but it is unknown whether metabolism also regulates this process. Here, we show that ECs relied on glycolysis rather than on oxidative phosphorylation for ATP production and that loss of the glycolytic activator PFKFB3 in ECs impaired vessel formation. Mechanistically, PFKFB3 not only regulated EC proliferation but also controlled the formation of filopodia/lamellipodia and directional migration, in part by compartmentalizing with F-actin in motile protrusions. Mosaic in vitro and in vivo sprouting assays further revealed that PFKFB3 overexpression overruled the pro-stalk activity of Notch, whereas PFKFB3 deficiency impaired tip cell formation upon Notch blockade, implying that glycolysis regulates vessel branching.

Inhibition of tumor angiogenesis and growth by a small-molecule multi-FGF receptor blocker with allosteric properties.

Receptor tyrosine kinases (RTK) are targets for anticancer drug development. To date, only RTK inhibitors that block orthosteric binding of ligands and substrates have been developed. Here, we report the pharmacologic characterization of the chemical SSR128129E (SSR), which inhibits fibroblast growth factor receptor (FGFR) signaling by binding to the extracellular FGFR domain without affecting orthosteric FGF binding. SSR exhibits allosteric properties, including probe dependence, signaling bias, and ceiling effects. Inhibition by SSR is highly conserved throughout the animal kingdom. Oral delivery of SSR inhibits arthritis and tumors that are relatively refractory to anti-vascular endothelial growth factor receptor-2 antibodies. Thus, orally-active extracellularly acting small-molecule modulators of RTKs with allosteric properties can be developed and may offer opportunities to improve anticancer treatment.

Increased serum activin-A differentiates alcoholic from cirrhosis of other aetiologies.

BACKGROUND: Activin-A is a molecule of the TGF superfamily, implicated in liver fibrosis, regeneration and stem cell differentiation. However, data on activins in liver diseases are few. We therefore studied serum levels of activin-A in chronic liver diseases. To identify the origin of activin-A, levels in the hepatic vein were also estimated. MATERIALS AND METHODS: Nineteen controls and 162 patients participated in the study: 39 with hepatocellular carcinoma (HCC: 19 viral associated and 20 alcohol associated), 18 with chronic hepatitis C (CHC), 47 with primary biliary cirrhosis (26 PBC stage I-II and 21 stage IV), 22 with alcoholic cirrhosis (AC, hepatic vein blood available in 16), 20 with HCV cirrhosis (hepatic vein blood available in 18) and 16 patients with alcoholic fatty liver with mild to moderate fibrosis but no cirrhosis. RESULTS: Activin-A levels were significantly increased (P < 0·001) in serum of patients with AC (median 673 pg/mL, range 449-3279), compared with either controls (149 pg/mL, 91-193) or patients with viral cirrhosis (189 pg/mL, 81-480), CHC (142 pg/mL, 65-559) PBC stage I-II (100 pg/mL, 59-597) and PBC stage IV (104 pg/mL, 81-579). Only patients with AC-associated HCC had significantly increased levels of activin-A (2403 pg/mL, 1561-7220 pg/mL). Activin-A serum levels could accurately discriminate AC from cirrhosis of other aetiologies and noncirrhotic alcoholic fatty liver with fibrosis. CONCLUSIONS: Increased serum levels of activin-A only in patients with alcohol-related cirrhosis or HCC suggest a possible role of this molecule in the pathophysiology of AC. Further research is warranted to elucidate its role during the profibrotic process and its possible clinical applications.

TNF receptors in Kupffer cells.

INTRODUCTION: Somatostatin is a mediator of immune functions and has been used as an antineoplastic agent in animal models and human neoplasias. We have demonstrated that Octreotide inhibits only LPS induced secretion of proinflammatory cytokines including TNFa by Kupffer cells (KC). We, therefore, tested the hypothesis that somatostatin modulates the expression of tumor necrosis factor alpha (TNF?) receptors and apoptosis of KC. METHODS: Rat KC were isolated by centrifugal elutriation. TNFR1 and TNFR2 expression was studied by RT-PCR, quantitative PCR, Western Blot and immunofluorescence before and after Octreotide pre-incubation. Apoptosis was assessed by quantitative measurement of cytoplasmic histone-associated DNA fragments. TNFa mRNA expression was assessed by semiquantitative PCR and TNFa was measured in cell supernatants by ELISA. RESULTS: TNFR1 and TNFR2 mRNA are constitutively expressed in KC. Octreotide incubation increased both receptors expression with a peak at 6?h and return to basal levels at 24?h. TNFR1 was mostly influenced. However, only increase in TNFR2 protein was identified, whereas a band at 90 kD was present instead of a band at 55 kD as expected for TNFR1. TNF? mRNA expression was inhibited by Octreotide and a significant inhibition was observed at 48?h. TNF had no effect on KC apoptosis, whereas Octreotide significantly increased their apoptosis, and this effect was not influenced by co-incubation with TNFa. CONCLUSION: TNFR1 and TNFR2 are constitutively expressed in KC and their expression is strongly increased by somatostatin. Moreover, somatostatin increases KC apoptosis. These findings may in part explain the antineoplasmatic effect of somatostatin.

From vessel sprouting to normalization: role of the prolyl hydroxylase domain protein/hypoxia-inducible factor oxygen-sensing machinery.

The accepted model of vessel branching distinguishes several endothelial cell fates. At the forefront of a vessel sprout, "tip cells" guide the sprouting vessel toward an angiogenic stimulus. Behind the tip, "stalk cells" proliferate to elongate the vessel branch and create a lumen. In mature vessels, endothelial cells acquire a streamlined shape to optimally conduct blood flow. For this purpose, endothelial cells switch to the "phalanx" cell fate, which is characterized by quiescent and nonproliferating cells aligned in a tight cobblestonelike layer. Vessel maturation also requires the recruitment of mural cells (ie, smooth muscle cells and pericytes). These cell fates are often altered in pathological conditions, most prominently during the formation of tumor vasculature. Given the essential role of hypoxia as the driving force for initiating angiogenesis, it is not surprising that the hypoxia-sensing machinery controls key steps in physiological and pathological angiogenesis.