Critical role of hypoxia sensor--HIF-1α in VEGF gene activation. Implications for angiogenesis and tissue injury healing

Síndrome de apnea-hipopnea obstructiva del sueño (SAHOS) y su relación con el cáncer

Desde hace algunos años se ha sugerido que los pacientes con síndrome de apnea-hipopnea obstructiva del sueño sin tratamiento tienen una mayor probabilidad de cáncer sólido y de mortalidad por cáncer, sin embargo hay dudas frente al tema. Por esta razón, en este artículo se describen, por un lado, los estudios más importantes al respecto y, por el otro, la fisiopatología propuesta por los investigadores que plantean esta asociación donde la hipoxia, el daño oxidativo del DNA, la disfunción endotelial y la disrupción de la arquitectura del sueño juegan un papel fundamental, además de otras consideraciones interesante.

Andrographolide reduced VEGFA expression in hepatoma cancer cells by inactivating HIF-1α: The involvement of JNK and MTA1/HDCA

Andrographolide (Andro) is the main active compound in medicinal herb Andrographis paniculata Nees (Acanthaceae). Vascular endothelial growth factor A (VEGFA), a key pro-angiogenic factor, contributes greatly to tumor growth. The purpose of this study is to observe the inhibition of Andro on VEGFA expression in hepatoma cancer cells and its engaged mechanism. Andro decreased mRNA and protein expression of VEGFA in hepatoma Hep3B and HepG2 cells. Andro also decreased hypoxia-inducible factor 1-alpha (HIF-1α) protein expression and its subsequent nuclear translocation. Further results showed that Andro induced the polyubiquitination of HIF-1α protein, and proteasome inhibitor MG132 reversed Andro-induced decrease in the expression of HIF-1α protein and VEGFA mRNA and protein. Andro reduced the expression of metastasis-associated protein 1 (MTA1) and histone deacetylase 1 (HDAC1) in hepatoma cancer cells. SP600125, an inhibitor of c-Jun N-terminal kinase (JNK), reversed Andro-induced decrease in the expression of HIF-1α and VEGFA, but not MTA1 and HDAC1. Andro (10 mg/kg) inhibited tumor growth in mice implanted with hepatoma Hep3B cells in vivo, and reduced the expression of CD31, VEGFA and HIF-1α in tumor tissues. In conclusion, Andro inhibited hepatoma tumor growth by reducing HIF-1α expression and its-mediated VEGFA expression via inducing ubiquitination-mediated HIF-1α protein degradation, and JNK and MTA1/HDAC1 may be involved in this process. Natural product Andro has huge potential in hepatoma cancer treatment.

HIF1A overexpression using cell-penetrating DNA-binding protein induces angiogenesis in vitro and in vivo

Hypoxia-inducible factor-1 alpha (HIF1A) is an important transcription factor for angiogenesis. Recent studies have used the protein transduction domain (PTD) to deliver genes, but the PTD has not been used to induce the expression of HIF1A. This study aimed at using a novel PTD (Hph-1-GAL4; ARVRRRGPRR) to overexpress the HIF1A and identify the effects on angiogenesis in vitro and in vivo. Overexpression of HIF1A was induced using Hph-1-GAL4 in human umbilical vein/vascular endothelium cells (HUVEC). The expression levels of genes were analyzed by the quantitative real-time polymerase chain reaction (qPCR) after 2 and 4 days, respectively. An in vitro tube formation was performed using Diff-Quik staining. HIF1A and Hph-1-GAL4 were injected subcutaneously into the ventral area of each 5-week-old mouse. All of the plugs were retrieved after 1 week, and the gene expression levels were evaluated by qPCR. Each Matrigel plug was evaluated using the hemoglobin assay and hematoxylin and eosin (HE) staining. The expression levels of HIF1A and HIF1A target genes were significantly higher in HIF1A-transfected HUVEC than in control HUVEC in vitro. In the in vivo Matrigel plug assay, the amount of hemoglobin was significantly higher in the HIF1A-treatment group than in the PBS-treatment group. Blood vessels were identified in the HIF1A-treatment group. The expression levels of HIF1A, vascular endothelial growth factor (Vegf), and Cd31 were significantly higher in the HIF1A-treatment group than in the PBS-treatment group. These findings suggest that using Hph-1-G4D to overexpress HIF1A might be useful for transferring genes and regenerating tissues.

Angiogenesis is VEGF-independent in the aged striatum of male rats exposed to acute hypoxia

Brain hypoxia is involved in many diseases. The activation of angiogenesis is one of the major adaptive mechanisms to counteract the adverse effects of hypoxia. In a previous work, we have shown that the adult rat striatum promotes angiogenesis in response to hypoxia via upregulation of the most important proangiogenic factor, the vascular endothelial growth factor (VEGF). However, the effects of hypoxia on angiogenesis in the aged striatum remain unknown and constitute our aim. Here we show the upregulation of hypoxia-inducible factor-1α in the striatum of aged (24-25 months old) Wistar rats exposed to acute hypoxia and analysed during a reoxygenation period ranging from 0 h to 5 days. While the mRNA expression of the proangiogenic factors VEGF, transforming growth factor-β1 (TGF-β1), and adrenomedullin dropped at 0 h post-hypoxia compared to normoxic control, no changes were detected at the protein level, showing an impaired response of these proangiogenic factors to hypoxia in the aged striatum. However, the striatal blood vessel network increased at 24 h of reoxygenation, suggesting that mechanisms independent from these proangiogenic factors may be involved in hypoxia-induced angiogenesis in the striatum of aged rats. A thorough understanding of the factors involved in the response to hypoxia is essential to guide the design of therapies for hypoxia-related diseases in the aged brain.

Adiponectin promotes VEGF-A-dependent angiogenesis in human chondrosarcoma through PI3K, Akt, mTOR, and HIF-α pathway

Chondrosarcoma is a type of highly malignant tumor with a potent capacity to invade locally and cause distant metastasis. Adiponectin is a protein hormone secreted predominantly by differentiated adipocytes. On the other hand, angiogenesis is a critical step in tumor growth and metastasis. However, the relationship of adiponectin with vascular endothelial growth factor-A (VEGF-A) expression and angiogenesis in human chondrosarcoma is mostly unknown. In this study we first demonstrated that the expression of adiponectin was correlated with tumor stage of human chondrosarcoma tissues. In addition, we also found that adiponectin increased VEGF-A expression in human chondrosarcoma cells and subsequently induced migration and tube formation in human endothelial progenitor cells (EPCs). Adiponectin promoted VEGF-A expression through adiponectin receptor (AdipoR), phosphoinositide 3 kinase (PI3K), Akt, mammalian target of rapamycin (mTOR), and hypoxia-inducible factor-1α (HIF)-1α signaling cascades. Knockdown of adiponectin decreased VEGF-A expression and also abolished chondrosarcoma conditional medium-mediated tube formation in EPCs in vitro as well as angiogenesis effects in the chick chorioallantoic membrane and Matrigel plug nude mice model in vivo. Therefore, adiponectin is crucial for tumor angiogenesis and growth, which may represent a novel target for anti-angiogenic therapy in human chondrosarcoma.

Albendazole inhibits HIF-1α-dependent glycolysis and VEGF expression in non-small cell lung cancer cells

Albendazole (ABZ) has an anti-tumor ability and inhibits HIF-1α activity. HIF-1α is associated with glycolysis and vascular endothelial cell growth factor (VEGF) expression, which plays an important role in cancer progression. These clues indicate that ABZ exerts an anti-cancer effect by regulating glycolysis and VEGF expression. The aim of this study is to clarify the effects of ABZ on non-small cell lung cancer (NSCLC) cells and explore the underlying molecular mechanisms. The expression levels of HIF-1α and VEGF were detected using western blot analysis, and the effect of ABZ on glycolysis was evaluated by measuring the relative activities of hexokinase (HK), pyruvate kinase (PK), and lactate dehydrogenase (LDH) and detecting the production of lactate in A549 and H1299 cells. The results showed that ABZ decreased the expression levels of HIF-1α and VEGF and suppressed glycolysis in under hypoxia, but not normoxic condition. Inhibiting HIF-1α also suppressed glycolysis and VEGF expression. Additionally, ABZ inhibited the volume and weight, decreased the relative activities of HK, PK, and LDH, and reduced the levels of HIF-1α and VEGF of A549 xenografts in mouse models. In conclusion, ABZ inhibited growth of NSCLC cells by suppressing HIF-1α-dependent glycolysis and VEGF expression.

Pomolic acid suppresses HIF1α/VEGF-mediated angiogenesis by targeting p38-MAPK and mTOR signaling cascades

BACKGROUND

Pomolic acid (PA), an active triterpenoid from Euscaphis japonica, inhibits the proliferation of a variety of cancer cells, but the molecular mechanisms of the anti-angiogenic potential of PA have not been fully elucidated in breast cancer cells.

HYPOTHESIS/PURPOSE

We investigated the molecular mechanisms underlying the anti-angiogenic effect of PA in epidermal growth factor (EGF)-responsive human breast cancer cells, MCF-7 and MDA-MB-231, and human umbilical vascular endothelial cells (HUVEC).

STUDY DESIGN/METHODS

Effects of PA on EGF-induced HIF1α/VEGF expression in MCF-7, MDA-MB-231 and HUVEC were assayed. As to the mechanisms, EGF-mediated MAPKs, PI3K/Akt, and mTOR signaling pathway were performed. Wound healing and invasion assay, tube formation assay, immunoblot assay, real-time PCR, luciferase gene assay, electrophoretic mobility shift assay and immunofluorescence staining were used for assessment.

RESULTS

PA significantly and selectively suppressed EGF-induced HIF1α/VEGF expression, whereas it did not affect the expression of HIF1β in MCF-7 and MDA-MB-231. Furthermore, PA inhibited EGF-induced angiogenesis in vitro and downregulated HIF1α/VEGF expression in HUVEC. Mechanistically, we found that the inhibitory effects of PA on HIF1α/VEGF expression are associated with inhibition of HIF1α/VEGF expression through an EGF-dependent mechanism. In addition, PA suppressed the EGF-induced phosphorylation of p38-MAPK and mTOR.

CONCLUSION

PA suppresses EGF-induced HIF1α protein translation by inhibiting the p38-MAPK and mTOR kinase signaling pathways and plays a novel anti-angiogenic role.

Estrogen stabilizes hypoxia-inducible factor 1α through G protein-coupled estrogen receptor 1 in eutopic endometrium of endometriosis

OBJECTIVE

To investigate whether G protein-coupled estrogen receptor (GPER, also known as GPR30 and GPER1) stabilizes hypoxia-inducible factor 1α (HIF-1α) in eutopic endometrium (EuEM) of endometriosis.

DESIGN

Immunohistochemical analysis and experimental in vitro study.

SETTING

University hospital.

PATIENT(S)

Patients with or without endometriosis.

INTERVENTION(S)

The EuEM and normal control endometrium (CoEM) were obtained by curettage. Primary cultured endometrial stromal cells (ESCs) were treated with 17β-E₂, G1, or G15.

MAIN OUTCOME MEASURE(S)

The EuEM and CoEM were collected for immunohistochemistry. Western blot, polymerase chain reaction, ELISA, and dual luciferase experiments were used to detect expression of GPER, HIF-1α, vascular endothelial growth factor (VEGF), and matrix metalloproteinase 9 (MMP9) in ESCs. Estradiol and G1 were used as agonists of GPER, G15 as an antagonist. Migration of ESCs and endothelial tube formation of human umbilical vein endothelial cells cultured in medium collected from ESCs were measured.

RESULT(S)

Protein levels of GPER and HIF-1α were higher in EuEM than in CoEM. Protein levels of HIF-1α but not HIF-1α mRNA levels increased concurrently with GPER after E₂ and G1 treatment. Furthermore, expression and activity of VEGF and MMP9 increased under E₂ and G1 stimulation. However, these effects disappeared when GPER was blocked.

CONCLUSION(S)

G protein-coupled estrogen receptor stabilizes HIF-1α and thus promotes HIF-1α-induced VEGF and MMP9 in ESCs, which play critical roles in endometriosis.

Partial Portal Vein Arterialization Attenuates Acute Bile Duct Injury Induced by Hepatic Dearterialization in a Rat Model

Hepatic infarcts or abscesses occur after hepatic artery interruption. We explored the mechanisms of hepatic deprivation-induced acute liver injury and determine whether partial portal vein arterialization attenuated this injury in rats. Male Sprague-Dawley rats underwent either complete hepatic arterial deprivation or partial portal vein arterialization, or both. Hepatic ischemia was evaluated using biochemical analysis, light microscopy, and transmission electron microscopy. Hepatic ATP levels, the expression of hypoxia- and inflammation-associated genes and proteins, and the expression of bile transporter genes were assessed. Complete dearterialization of the liver induced acute liver injury, as evidenced by the histological changes, significantly increased serum biochemical markers, decreased ATP content, increased expression of hypoxia- and inflammation-associated genes and proteins, and decreased expression of bile transporter genes. These detrimental changes were extenuated but not fully reversed by partial portal vein arterialization, which also attenuated ductular reaction and fibrosis in completely dearterialized rat livers. Collectively, complete hepatic deprivation causes severe liver injury, including bile infarcts and biloma formation. Partial portal vein arterialization seems to protect against acute ischemia-hypoxia-induced liver injury.

Meta-Analysis of Microarray-Based Expression Profiles to Identify Differentially Expressed Genes in Intracranial Aneurysms

OBJECTIVE

To gain comprehensive insight into the molecular mechanism of formation and rupture of intracranial aneurysms (IAs).

METHODS

All publicly accessible microarray-based whole-genome gene expression profiles on IAs were retrieved. The significance analysis of microarrays method was applied to identify differentially expressed genes (DEGs). Functional annotation was performed using gene ontology terms and Kyoto Encyclopedia of Genes and Genomes pathway enrichment analyses. Expression of DEGs was examined using quantitative polymerase chain reaction.

RESULTS

Six data sets of 3 microarray platforms were qualified and analyzed. Comparing expression profiles between aneurysmal wall and control vessels, 5232 significant DEGs were identified among 3 platforms, and MMP12 was shown to have the largest fold change of upregulation. In all 3 platforms, 46 DEGs were shared, and 1297 DEGs were commonly resolved in at least 2 microarray platforms. Among these 1297 concordant DEGs, the 512 upregulated genes were mainly enriched in inflammatory and immune response processes, whereas the 785 downregulated genes were primarily concentrated in smooth muscle cell contraction and development pathways. Comparison between expression profiles of ruptured and unruptured IAs revealed that a few angiogenic factors, including HIF1A, VEGFA, and ANGPTL4, were upregulated in ruptured aneurysms. Subsequently, the upregulation of MMP12, HIF1A, and VEGFA was partially confirmed using quantitative polymerase chain reaction among independent samples.

CONCLUSIONS

Inflammation, immune response, and loss of contractile vascular smooth muscle cells could potentially contribute to the formation of IAs, whereas the role of angiogenesis and vascular remodeling in IA formation and rupture needs further exploration.

SYP-5, a novel HIF-1 inhibitor, suppresses tumor cells invasion and angiogenesis

Hypoxia-inducible factor-1 (HIF-1) plays an essential role in carcinogenesis. The overexpression of HIF-1 induced by hypoxia is closely associated with metastasis, poor prognosis and high mortality. In this study, a novel HIF-1 inhibitor SYP-5 was first observed by the luciferase reporter assay. Western blots results showed SYP-5 inhibited hypoxia-induced upregulation of HIF-1. Moreover, the proteins of vascular endothelial growth factor (VEGF) and matrix metalloproteinases (MMP)-2 that are targets of HIF-1, were down-regulated by SYP-5. Furthermore, in the tube formation assay, SYP-5 suppressed angiogenesis induced by hypoxia and VEGF in vitro. Additionally, using Transwell and RTCA assays, we found that SYP-5 also retarded the Hep3B and Bcap37 cells migration and invasion induced by hypoxia and FBS. Last, we also detected the upstream pathways related to HIF-1 and found both PI3K/AKT and MAPK/ERK were involved in the SYP-5 mediated invasive inhibition of Bcap37 cells. These results indicates that SYP-5 inhibits tumor cell migration and invasion, as well as tumor angiogenesis, which are mediated by suppressing PI3K/AKT- and MAPK/ERK-dependent HIF-1 pathway. It suggests that SYP-5 might be a potential HIF-1 inhibitor as an anticancer agent.

Hypoxia in Atherogenesis

The anoxemia theory proposes that an imbalance between the demand for and supply of oxygen in the arterial wall is a key factor in the development of atherosclerosis. There is now substantial evidence that there are regions within the atherosclerotic plaque in which profound hypoxia exists; this may fundamentally change the function, metabolism, and responses of many of the cell types found within the developing plaque and whether the plaque will evolve into a stable or unstable phenotype. Hypoxia is characterized in molecular terms by the stabilization of hypoxia-inducible factor (HIF) 1α, a subunit of the heterodimeric nuclear transcriptional factor HIF-1 and a master regulator of oxygen homeostasis. The expression of HIF-1 is localized to perivascular tissues, inflammatory macrophages, and smooth muscle cells adjacent to the necrotic core of atherosclerotic lesions and regulates several genes that are important to vascular function including vascular endothelial growth factor, nitric oxide synthase, endothelin-1, and erythropoietin. This review summarizes the effects of hypoxia on the functions of cells involved in atherogenesis and the evidence for its potential importance from experimental models and clinical studies.

sMEK1 inhibits endothelial cell proliferation by attenuating VEGFR-2-dependent-Akt/eNOS/HIF-1α signaling pathways

The suppressor of MEK null (sMEK1) protein possesses pro-apoptotic activities. In the current study, we reveal that sMEK1 functions as a novel anti-angiogenic factor by suppressing vascular endothelial growth factor (VEGF)-induced cell proliferation, migration, and capillary-like tubular structure in vitro. In addition, sMEK1 inhibited the phosphorylation of the signaling components up- and downstream of Akt, including phospholipase Cγ1 (PLC-γ1), 3-phosphoinositide-dependent protein kinase 1 (PDK1), endothelial nitric oxide synthetase (eNOS), and hypoxia-inducible factor 1 (HIF-1α) during ovarian tumor progression via binding with vascular endothelial growth factor receptor 2 (VEGFR-2). Furthermore, sMEK1 decreased tumor vascularity and inhibited tumor growth in a xenograft human ovarian tumor model. These results supply convincing evidence that sMEK1 controls endothelial cell function and subsequent angiogenesis by suppressing VEGFR-2-mediated PI3K/Akt/eNOS signaling pathway. Taken together, our results clearly suggest that sMEK1 might be a novel anti-angiogenic and anti-tumor agent for use in ovarian tumor.

Erythropoietin and a nonerythropoietic peptide analog promote aortic endothelial cell repair under hypoxic conditions: role of nitric oxide

The cytoprotective effects of erythropoietin (EPO) and an EPO-related nonerythropoietic analog, pyroglutamate helix B surface peptide (pHBSP), were investigated in an in vitro model of bovine aortic endothelial cell injury under normoxic (21% O₂) and hypoxic (1% O₂) conditions. The potential molecular mechanisms of these effects were also explored. Using a model of endothelial injury (the scratch assay), we found that, under hypoxic conditions, EPO and pHBSP enhanced scratch closure by promoting cell migration and proliferation, but did not show any effect under normoxic conditions. Furthermore, EPO protected bovine aortic endothelial cells from staurosporine-induced apoptosis under hypoxic conditions. The priming effect of hypoxia was associated with stabilization of hypoxia inducible factor-1α, EPO receptor upregulation, and decreased Ser-1177 phosphorylation of endothelial nitric oxide synthase (NOS); the effect of hypoxia on the latter was rescued by EPO. Hypoxia was associated with a reduction in nitric oxide (NO) production as assessed by its oxidation products, nitrite and nitrate, consistent with the oxygen requirement for endogenous production of NO by endothelial NOS. However, while EPO did not affect NO formation in normoxia, it markedly increased NO production, in a manner sensitive to NOS inhibition, under hypoxic conditions. These data are consistent with the notion that the tissue-protective actions of EPO-related cytokines in pathophysiological settings associated with poor oxygenation are mediated by NO. These findings may be particularly relevant to atherogenesis and postangioplasty restenosis.

Potent ameliorating effect of Hypoxia-inducible factor 1α (HIF-1α) antagonist YC-1 on combined allergic rhinitis and asthma syndrome (CARAS) in Rats

Recent studies have implicated that Hypoxia-inducible factor 1α (HIF-1α) plays an integral role in the pathogenesis of allergic rhinitis and asthma. In the present study, we showed that HIF-1α antagonist YC-1, 3-(5-hydroxymethyl-2-furyl)-1-benzylindazole, elicited a potent allergy-ameliorating effect in a rat model of ovalbumin (OVA)-sensitized combined allergic rhinitis and asthma syndrome (CARAS). We revealed that YC-1 administration markedly impaired the total number and percentage of eosinophil in bronchoalveolar lavage fluid (BAL Fluid) of the rats, suggesting that YC-1 might attenuate lung and nasal mucosal inflammation in OVA-sensitized rats. Moreover, histological examination found that OVA-induced pathological alterations were evidently attenuated following YC-1 administration. In addition, immunohistochemistrial analysis indicated that YC-1 treatment decreased the expression of HIF-1α in rat lungs and nasal mucosa. Notably, Nuclear factor kappa B (NF-κB) p65 and Peroxisome proliferator-activated receptor α (PPARα), two important regulators of inflammatory responses, were also significantly down-regulated following YC-1 administration. Real-time PCR analysis confirmed that YC-1 impaired the expression of HIF-1α, NF-κB and PPARα in CARAS model. These findings together indicated that YC-1 exerted remarkable anti-allergic effects through the modulation of inflammatory pathways, implying that YC-1 may potentially serve as a novel anti-CARAS medicine in clinical patients.

Hypoxia enhances angiogenesis in an adipose-derived stromal cell/endothelial cell co-culture 3D gel model

OBJECTIVES

This study aimed to investigate the influence of hypoxia on angiogenesis in a 3D gel, with co-culturing adipose-derived stromal cells (ASCs) and endothelial cells (ECs).

MATERIALS AND METHODS

ASCs from green fluorescent protein-labeled mice and ECs from red fluorescent protein-labeled mice were co-cultured in 3D collagen gels at 1:1 ratio, in normal and hypoxic oxygen conditions, and morphology of angiogenesis was observed using confocal laser scanning microscopy. To discover changes in growth factors between monoculture ASCs and ECs, transwell co-cultures of ASCs and ECs were applied. Semi-quantitative PCR was performed to explore mRNA expression of growth factors.

RESULTS

Enhanced angiogenesis was observed in 3D gels implanted with 1:1 mixture of ASCs and ECs after 7 days hypoxia. Genes including VEGFA/B, EGF-1, HIF-1a, IGF-1, PDGF, TGF-β1 and BMP-2/4 in ECs, both monoculture and co-culture, were significantly enhanced after being cultured under hypoxia. In comparison, genes VEGFA/B, EGF-1, HIF-1a, TGF-β1 and BMP-2 in ASCs increased. In all, factors VEGFA/B, EGF-1, HIF-1a, TGF-β1 and BMP-2 increased in both ASCs and ECs after being cultured in hypoxia no matter whether as monoculture or co-culture.

CONCLUSIONS

Co-culture of ASCs and ECs at 1:1 ratio in a 3D gel under hypoxia promoted angiogenesis. Those growth factors which were increased in both ASCs and ECs, indicate that VEGFA/B, EGF-1, HIF-1a, TGF-β1 and BMP-2 might be responsible for enhancement in angiogenesis triggered by hypoxia.

A key role of PGC-1α transcriptional coactivator in production of VEGF by a novel angiogenic agent COA-Cl in cultured human fibroblasts

We previously demonstrated a potent angiogenic effect of a newly developed adenosine-like agent namedCOA-Cl.COA-Cl exerted tube forming activity in human umbilical vein endothelial cells in the presence of normal human dermal fibroblasts (NHDF). We therefore explored whether and howCOA-Cl modulates gene expression and protein secretion ofVEGF, a master regulator of angiogenesis, inNHDFRT-PCRandELISArevealed thatCOA-Cl upregulatedVEGF mRNAexpression and protein secretion inNHDFHIF1α(hypoxia-inducible factor 1α), a transcription factor, andPGC-1α(peroxisome proliferator-activated receptor-γcoactivator-1α), a transcriptional coactivator, are known to positively regulate theVEGFgene. Immunoblot andRT-PCRanalyses revealed thatCOA-Cl markedly upregulated the expression ofPGC-1αprotein andmRNACOA-Cl had no effect on the expression ofHIF1αprotein andmRNAin both hypoxia and normoxia. SilencingPGC-1αgene, but notHIF1αgene, by small interferingRNAattenuated the ability ofCOA-Cl to promoteVEGFsecretion. When an N-terminal fragment ofPGC-1αwas cotransfected with its partner transcription factorERRα(estrogen-related receptor-α) inCOS-7 cells,COA-Cl upregulated the expression of the endogenousVEGF mRNA However,COA-Cl had no effect on the expression ofVEGF, whenHIF1αwas transfected.COA-Cl inducesVEGFgene expression and protein secretion in fibroblasts. The transcriptional coactivatorPGC-1α, in concert withERRα, plays a key role in theCOA-Cl-inducedVEGFproduction.COA-Cl-induced activation ofPGC-1α-ERRα-VEGFpathway has a potential as a novel means for therapeutic angiogenesis.

Nanofibrous spongy microspheres for the delivery of hypoxia-primed human dental pulp stem cells to regenerate vascularized dental pulp

Dental pulp infection and necrosis are widespread diseases. Conventional endodontic treatments result in a devitalized and weakened tooth. In this work, we synthesized novel star-shaped polymer to self-assemble into unique nanofibrous spongy microspheres (NF-SMS), which were used to carry human dental pulp stem cells (hDPSCs) into the pulp cavity to regenerate living dental pulp tissues. It was found that NF-SMS significantly enhanced hDPSCs attachment, proliferation, odontogenic differentiation and angiogenesis, as compared to control cell carriers. Additionally, NF-SMS promoted vascular endothelial growth factor (VEGF) expression of hDPSCs in a 3D hypoxic culture. Hypoxia-primed hDPSCs/NF-SMS complexes were injected into the cleaned pulp cavities of rabbit molars for subcutaneous implantation in mice. After 4 weeks, the hypoxia group significantly enhanced angiogenesis inside the pulp chamber and promoted the formation of ondontoblast-like cells lining along the dentin-pulp interface, as compared to the control groups (hDPSCs alone group, NF-SMS alone group, and hDPSCs/NF-SMS group pre-cultured under normoxic conditions). Furthermore, in an in situ dental pulp repair model in rats, hypoxia-primed hDPSCs/NF-SMS were injected to fully fill the pulp cavity and regenerate pulp-like tissues with a rich vasculature and a histological structure similar to the native pulp.

STATEMENT OF SIGNIFICANCE

Vascularization is key to the regeneration of many vital tissues. However, it is challenging to create a suitable microenvironment for stem cells to regenerate vascularized tissue structure. This manuscript reports a novel star-shaped block copolymer that self-assembles into unique nanofibrous spongy microspheres, which as an injectable scaffold recapitulate the cell-cell and cell-matrix interactions in development. Using a clinically-relevant surgical procedure and a hypoxic treatment, the nanofibrous spongy microspheres were used to deliver stem cells and successfully regenerate dental pulp with a rich vasculature and a complex histologic structure similar to that of the native dental pulp. The novel microspheres can likely be used to regenerate many other vascularized tissues.

WISP-1 a novel angiogenic regulator of the CCN family promotes oral squamous cell carcinoma angiogenesis through VEGF-A expression

Oral squamous cell carcinoma (OSCC), which accounts for nearly 90% of head and neck cancers, is characterized by poor prognosis and a low survival rate. VEGF-A is the most established angiogenic factor involved in the angiogenic-regulated tumor progression. WISP-1/CCN4 is an extracellular matrix-related protein that belongs to the Cyr61, CTGF, Nov (CCN) family and regulates many biological functions, such as angiogenesis. Previous studies indicated the role of WISP-1 in tumor progression. However, the angiogenic property of WISP-1 in the cancer microenvironment has never been discussed. Here, we provide novel insights regarding the role of WISP-1 in the angiogenesis through promoting VEGF-A expression. In this study, the correlation of WISP-1 and VEGF-A was confirmed by IHC staining of specimens from patients with OSCC. In vitro results indicated that WISP-1 induced VEGF-A expression via the integrin αvβ3/FAK/c-Src pathway, which transactivates the EGFR/ERK/HIF1-α signaling pathway in OSCC. This pathway in turn induces the recruitment of endothelial progenitor cells and triggers the neovascularization in the tumor microenvironment. Our in vivo data revealed that tumor-secreted WISP-1 promoted the angiogenesis through VRGF expression and increased angiogenesis-related tumor growth. Our study offers new information that highlights WISP-1 as a potential novel therapeutic target for OSCC.

Vascularization strategies for tissue engineers

All tissue-engineered substitutes (with the exception of cornea and cartilage) require a vascular network to provide the nutrient and oxygen supply needed for their survival in vivo. Unfortunately the process of vascular ingrowth into an engineered tissue can take weeks to occur naturally and during this time the tissues become starved of essential nutrients, leading to tissue death. This review initially gives a brief overview of the processes and factors involved in the formation of new vasculature. It then summarizes the different approaches that are being applied or developed to overcome the issue of slow neovascularization in a range of tissue-engineered substitutes. Some potential future strategies are then discussed.

The cartilage extracellular matrix as a transient developmental scaffold for growth plate maturation

The cartilage growth plate is a specialized developmental tissue containing characteristic zonal arrangements of chondrocytes. The proliferative and differentiative states of chondrocytes are tightly regulated at all stages including the initial limb bud and rudiment cartilage stages of development, the establishment of the primary and secondary ossification centers, development of the growth plates and laying down of bone. A multitude of spatio-temporal signals, including transcription factors, growth factors, morphogens and hormones, control chondrocyte maturation and terminal chondrocyte differentiation/hypertrophy, cell death/differentiation, calcification and vascular invasion of the growth plate and bone formation during morphogenetic transition of the growth plate. This involves hierarchical, integrated signaling from growth and factors, transcription factors, mechanosensory cues and proteases in the extracellular matrix to regulate these developmental processes to facilitate progressive changes in the growth plate culminating in bone formation and endochondral ossification. This review provides an overview of selected components which have particularly important roles in growth plate biology including collagens, proteoglycans, glycosaminoglycans, growth factors, proteases and enzymes.

Peptidyl Prolyl Isomerase PIN1 Directly Binds to and Stabilizes Hypoxia-Inducible Factor-1α

Peptidyl prolyl isomerase (PIN1) regulates the functional activity of a subset of phosphoproteins through binding to phosphorylated Ser/Thr-Pro motifs and subsequently isomerization of the phosphorylated bonds. Interestingly, PIN1 is overexpressed in many types of malignancies including breast, prostate, lung and colon cancers. However, its oncogenic functions have not been fully elucidated. Here, we report that PIN1 directly interacts with hypoxia-inducible factor (HIF)-1α in human colon cancer (HCT116) cells. PIN1 binding to HIF-1α occurred in a phosphorylation-dependent manner. We also found that PIN1 interacted with HIF-1α at both exogenous and endogenous levels. Notably, PIN1 binding stabilized the HIF-1α protein, given that their levels were significantly increased under hypoxic conditions. The stabilization of HIF-1α resulted in increased transcriptional activity, consequently upregulating expression of vascular endothelial growth factor, a major contributor to angiogenesis. Silencing of PIN1 or pharmacologic inhibition of its activity abrogated the angiogenesis. By utilizing a bioluminescence imaging technique, we were able to demonstrate that PIN1 inhibition dramatically reduced the tumor volume in a subcutaneous mouse xenograft model and angiogenesis as well as hypoxia-induced transcriptional activity of HIF-1α. These results suggest that PIN1 interacting with HIF-1α is a potential cancer chemopreventive and therapeutic target.

Angiogenic factors and inflammation in steroid-refractory acute graft-vs-host disease

Steroid-refractory acute graft-vs-host disease (aGVHD) remains a frequent and often fatal complication of allogeneic hematopoietic cell transplantation. Recent evidence suggests that angiogenic factors-growth factors that contribute to blood vessel development-may be involved in tissue healing and restitution after inflammatory insults such as aGVHD. However, some angiogenic factors may also be involved in inflammation and worsen clinical outcomes. In this review, we summarize the data relevant to angiogenic factors that may contribute to healing after aGVHD (epidermal growth factor and vascular endothelial growth factor A) and angiogenic factors that may promote inflammation after aGVHD (placental growth factor and follistatin). It is currently unknown whether changes in these factors are a cause or a consequence of aGVHD. Mechanistic studies in the coming years will clarify their roles and identify new pathways for improving outcomes in steroid-refractory aGVHD.

CXCL16 induces angiogenesis in autocrine signaling pathway involving hypoxia-inducible factor 1α in human umbilical vein endothelial cells

Chemokine (C-X-C motif) ligand 16 (CXCL16) is a new angiogenic factor inducing angiogenesis via extracellular signal-regulated kinases pathway. To further understand the molecular mechanism underlying CXCL16‑induced angiogenesis, we explored involvement of other relevant pathways in CXCL16-induced angiogenesis. In the present study, we investigated the mechanisms underlying CXCL16-induced angiogenesis in human umbilical vein endothelial cells (HUVECs). CXCL16 promoted HUVEC proliferation, tube formation and migration. Enzyme-linked immunosorbent assay revealed that CXCL16 induced vascular endothelial growth factor secretion from HUVECs. Western blot analysis showed that CXCL16 increased the level of hypoxia‑inducible factor 1α, p-extracellular signal-regulated kinases (ERK), p-p38 and p-Akt dose- and time-dependently. ERK-, p38- and Akt-selective inhibitors significantly suppressed HUVEC proliferation, migration, tube formation and hypoxia-inducible factor 1α (HIF-1α) expression induced by CXCL16. Furthermore, CXCL16 peptides induced CXCL16 secretion via ERK, p38 and Akt pathways, which was suppressed by HIF-1α-selective inhibitor PX12. Our data suggest that CXCL16 induces angiogenesis in autocrine manner via ERK, Akt, p38 pathways and HIF-1α modulation.

Mitochondrial Aldehyde Dehydrogenase 2 Regulates Revascularization in Chronic Ischemia: Potential Impact on the Development of Coronary Collateral Circulation

OBJECTIVE

Revascularization is an essential process to compensate for cardiac underperfusion and, therefore, preserves cardiac function in the face of chronic ischemic injury. Recent evidence suggested a vital role of aldehyde dehydrogenase 2 (ALDH2) in cardiac protection after ischemia. This study was designed to determine whether ALDH2 regulates chronic ischemia-induced angiogenesis and to explore the underlying mechanism involved. Moreover, the clinical impact of the ALDH2 mutant allele on the development of coronary collateral circulation (CCC) was evaluated.

APPROACH AND RESULTS

Mice limb ischemia was performed. Compared with wild-type, ALDH2 deletion significantly reduced perfusion recovery, small artery and capillary density, and increased muscle atrophy in this ischemic model. In vitro, ALDH2-knockdown reduced proliferation, migration and hypoxia triggered endothelial tube formation of endothelial cells, the effects of which were restored by ALDH2 transfection. Further examination revealed that ALDH2 regulated angiogenesis possibly through hypoxia-inducible factor-1α/vascular endothelial growth factor pathways. To further discern the role of ALDH2 deficiency in the function of bone marrow stem/progenitor cells, cross bone marrow transplantation was performed between wild-type and ALDH2-knockout mice. However, there was no significant improvement for wild-type bone marrow transplantation into knockout mice. ALDH2 genotyping was screened in 139 patients with chronic total occlusion recruited to Zhongshan Hospital (2011.10-2014.4). Patients with poor CCC (Rentrop 0-1; n=51) exhibited a higher frequency of the AA genotype than those with enriched CCC (Rentrop 2-3; n=88; 11.76% versus 1.14%; P=0 0.01). However, the AA group displayed less enriched CCC frequency in Logistic regression model when compared with the GG group (odds ratio=0.08; 95% confidence interval, 0.009-0.701; P=0 0.026). Furthermore, serum vascular endothelial growth factor level tended to be lower in patients with ALDH2 mutation.

CONCLUSIONS

This study demonstrated that ALDH2 possesses an intrinsic capacity to regulate angiogenesis via hypoxia-inducible factor-1α and vascular endothelial growth factor. Patients with ALDH2-deficient genotype displayed a higher risk of developing poor CCC. Therapeutic individualization based on ALDH2 allele distribution may thus improve the therapeutic benefit, especially in the East Asian decedents.

12-Deoxyphorbol 13-palmitate inhibits the expression of VEGF and HIF-1α in MCF-7 cells by blocking the PI3K/Akt/mTOR signaling pathway

Vascular endothelial growth factor (VEGF) is an essential component for angiogenesis, and hypoxia-inducible factor-1α (HIF-1α), which controls the switch of glycolytic and oxidative metabolism, activates the transcription of VEGF. 12-Deoxyphorbol 13-palmitate (DP) is a compound isolated from the roots of Euphorbia fischeriana, and has been revealed to possess anticancer activity. In the present study, we found that DP is an effective inhibitor of VEGF and HIF-1α in MCF-7 cells. DP markedly reduced cell viability as determined by MTT assay. ELISA, western blotting and RT-qPCR assays indicated that DP significantly decreased the protein and mRNA expression of VEGF and the protein expression of HIF-1α, while HIF-1α mRNA remained unchanged. In addition, the entrance of HIF-1α into the nucleus was blocked after DP treatment as detected by immunofluorescence analysis. In a further study, we proved that the effects mentioned above were associated with constitutive interference of the phosphatidylinositol 3-kinase (PI3K)/Akt/mammalian target of rapamycin (mTOR) pathway. DP effectively inhibited the phosphorylation of PI3K and its downstream factors p-Akt and p-mTOR, oppositely enhanced the expression of TSC1 (hamartin) and TSC2 (tuberin), which could be reversed by the co-treatment with the PI3K inhibitor wortmannin. Moreover, the addition of wortmanin further downregulated the protein levels of VEGF and HIF-1α. The results revealed that DP inhibited the expression of VEGF and HIF-1α through the PI3K/Akt/mTOR signaling pathway, confirming that DP may be a potential therapeutic candidate for breast cancer.

Basic fibroblast growth factor induces VEGF expression in chondrosarcoma cells and subsequently promotes endothelial progenitor cell-primed angiogenesis

Chondrosarcoma, a common malignant tumour, develops in bone. Effective adjuvant therapy remains inadequate for treatment, meaning poor prognosis. It is imperative to explore novel remedies. Angiogenesis is a rate-limiting step in progression that explains neovessel formation for blood supply in the tumour microenvironment. Numerous studies indicate that EPCs (endothelial progenitor cells) promote angiogenesis and contribute to tumour growth. bFGF (basic fibroblast growth factor), a secreted cytokine, regulates biological activity, including angiogenesis, and correlates with tumorigenesis. However, the role of bFGF in angiogenesis-related tumour progression by recruiting EPCs in human chondrosarcoma is rarely discussed. In the present study, we found that bFGF induced VEGF (vascular endothelial growth factor) expression via the FGFR1 (fibroblast growth factor receptor 1)/c-Src/p38/NF-κB (nuclear factor κB) signalling pathway in chondrosarcoma cells, thereby triggering angiogenesis of endothelial progenitor cells. Our in vivo data revealed that tumour-secreted bFGF promotes angiogenesis in both mouse plug and chick CAM (chorioallantoic membrane) assays. Xenograft mouse model data, due to bFGF-regulated angiogenesis, showed the bFGF regulates angiogenesis-linked tumour growth. Finally, bFGF was highly expressed in chondrosarcoma patients compared with normal cartilage, positively correlating with VEGF expression and tumour stage. The present study reveals a novel therapeutic target for chondrosarcoma progression.

Stimulation of osteogenesis and angiogenesis of hBMSCs by delivering Si ions and functional drug from mesoporous silica nanospheres

Multifunctional bioactive materials with the ability to stimulate osteogenesis and angiogenesis of stem cells play an important role in the regeneration of bone defects. However, how to develop such biomaterials remains a significant challenge. In this study, we prepared mesoporous silica nanospheres (MSNs) with uniform sphere size (∼90 nm) and mesopores (∼2.7 nm), which could release silicon ions (Si) to stimulate the osteogenic differentiation of human bone marrow stromal cells (hBMSCs) via activating their ALP activity, bone-related gene and protein (OCN, RUNX2 and OPN) expression. Hypoxia-inducing therapeutic drug, dimethyloxaloylglycine (DMOG), was effectively loaded in the mesopores of MSNs (D-MSNs). The sustained release of DMOG from D-MSNs could stabilize HIF-1α and further stimulated the angiogenic differentiation of hBMSCs as indicated by the enhanced VEGF secretion and protein expression. Our study revealed that D-MSNs could combine the stimulatory effect on both osteogenic and angiogenic activity of hBMSCs. The potential mechanism of D-MSN-stimulated osteogenesis and angiogenesis was further elucidated by the supplementation of cell culture medium with pure Si ions and DMOG. Considering the easy handling characteristics of nanospheres, the prepared D-MSNs may be applied in the forms of injectable spheres for minimally invasive surgery, or MSNs/polymer composite scaffolds for bone defect repair. The concept of delivering both stimulatory ions and functional drugs may offer a new strategy to construct a multifunctional biomaterial system for bone tissue regeneration.

Hypoxia-inducible MiR-182 promotes angiogenesis by targeting RASA1 in hepatocellular carcinoma

BACKGROUND

Hypoxia is a common feature of solid tumors, including HCC. And hypoxia has been reported to play an important role in HCC progression. However, the potential mechanism of miRNAs in hypoxia mediating HCC progression still remains unclear.

METHODS

The HCC cells were cultured in the atmosphere of 1 % oxygen to induce hypoxia. The microRNA microarray was employed to search for the hypoxia-inducible miRNAs. RT-PCR, western blot and immunohistochemistry were used to detect the RNA and protein levels. HUVEC were applied to explore the angiogenesis level.

RESULTS

We found that miR-182 was upregulated in the hypoxia-based microarray. We then revealed that miR-182 was also significantly increased in the HCC tissues compared to the corresponding normal tissues. In vitro capilliary tube formation assays showed that the miR-182 promoted angiogenesis. RASA1 was demonstrated as the direct target of miR-182. In addition, the suppression of RASA1 phenocopied the pro-angiogenesis effects of miR-182. Besides, RASA1 was also decreased in the hypoxia HCC cells while the inhibition of miR-182 partially restored the level of RASA1.

CONCLUSIONS

Our data showed that hypoxia regulated the expression of miR-182 and RASA1 to promote HCC angiogenesis.

Cell-permeable mitochondrial ubiquinol-cytochrome c reductase binding protein induces angiogenesis in vitro and in vivo

Ubiquinol-cytochrome c reductase binding protein (UQCRB), a component of the mitochondrial complex III, has been recently implicated in angiogenesis. Targeting mitochondria to balance vascular homeostasis has been widely recognized. However, the effect of UQCRB replenishment by direct delivery remains unknown. To explore the biological function of UQCRB in angiogenesis, a novel protein transduction domain (PTD)-conjugated UQCRB fusion protein was generated. PTD-UQCRB localized to mitochondria as does endogenous UQCRB. Treatment with PTD-UQCRB generated mitochondrial reactive oxygen species (mROS) without cytotoxicity, following hypoxia inducible factor-1α (HIF-1α) stabilization and downstream vascular endothelial growth factor (VEGF) expression. Accordingly, PTD-UQCRB induced angiogenesis in vitro and PTD-UQCRB pro-angiogenic activity was further validated in matrigel plug assay and in cutaneous wound-healing mouse models in vivo. Together, these results demonstrate that UQCRB plays a role in angiogenesis and the developed cell-permeable PTD-UQCRB can be utilized as a pro-angiogenic agent.

Superpulsed (Ga-As, 904 nm) low-level laser therapy (LLLT) attenuates inflammatory response and enhances healing of burn wounds

Low-level laser therapy (LLLT) using superpulsed near-infrared light can penetrate deeper in the injured tissue and could allow non-pharmacological treatment for chronic wound healing. This study investigated the effects of superpulsed laser (Ga-As 904 nm, 200 ns pulse width; 100 Hz; 0.7 mW mean output power; 0.4 mW/cm(2) average irradiance; 0.2 J/cm(2) total fluence) on the healing of burn wounds in rats, and further explored the probable associated mechanisms of action. Irradiated group exhibited enhanced DNA, total protein, hydroxyproline and hexosamine contents compared to the control and silver sulfadiazine (reference care) treated groups. LLLT exhibited decreased TNF-α level and NF-kB, and up-regulated protein levels of VEGF, FGFR-1, HSP-60, HSP-90, HIF-1α and matrix metalloproteinases-2 and 9 compared to the controls. In conclusion, LLLT using superpulsed 904 nm laser reduced the inflammatory response and was able to enhance cellular proliferation, collagen deposition and wound contraction in the repair process of burn wounds. Photomicrographs showing no, absence inflammation and faster wound contraction in LLLT superpulsed (904 nm) laser treated burn wounds as compared to the non-irradiated control and silver sulfadiazine (SSD) ointment (reference care) treated wounds.

The effect of osteoimmunomodulation on the osteogenic effects of cobalt incorporated β-tricalcium phosphate

Osteoblast lineage cells are direct effectors of osteogenesis and are, therefore, commonly used to evaluate the in vitro osteogenic capacity of bone substitute materials. This method has served its purposes when testing novel bone biomaterials; however, inconsistent results between in vitro and in vivo studies suggest the mechanisms that govern a material's capacity to mediate osteogenesis are not well understood. The emerging field of osteoimmunology and immunomodulation has informed a paradigm shift in our view of bone biomaterials-from one of an inert to an osteoimmunomodulatory material-highlighting the importance of immune cells in materials-mediated osteogenesis. Neglecting the importance of the immune response during this process is a major shortcoming of the current evaluation protocol. In this study we evaluated a potential angiogenic bone substitute material cobalt incorporated with β-tricalcium phosphate (CCP), comparing the traditional "one cell type" approach with a "multiple cell types" approach to assess osteogenesis, the latter including the use of immune cells. We found that CCP extract by itself was sufficient to enhance osteogenic differentiation of bone marrow stem cells (BMSCs), whereas this effect was cancelled out when macrophages were involved. In response to CCP, the macrophage phenotype switched to the M1 extreme, releasing pro-inflammatory cytokines and bone catabolic factors. When the CCP materials were implanted into a rat femur condyle defect model, there was a significant increase of inflammatory markers and bone destruction, coupled with fibrous encapsulation rather than new bone formation. These findings demonstrated that the inclusion of immune cells (macrophages) in the in vitro assessment matched the in vivo tissue response, and that this method provides a more accurate indication of the essential role of immune cells when assessing materials-stimulated osteogenesis in vitro.

Ubiquitin-specific peptidase 22 inhibits colon cancer cell invasion by suppressing the signal transducer and activator of transcription 3/matrix metalloproteinase 9 pathway

Colon cancer is associated with increased cell migration and invasion. In the present study, the role of ubiquitin-specific peptidase 22 (USP22) in signal transducer and activator of transcription 3 (STAT3)-mediated colon cancer cell invasion was investigated. The messenger RNA levels of STAT3 target genes were measured by reverse transcription-quantitative polymerase chain reaction, following USP22 knockdown by RNA interference in SW480 colon cancer cells. The matrix metalloproteinase 9 (MMP9) proteolytic activity and invasion potential of SW480 cells were measured by zymography and Transwell assay, respectively, following combined USP22 and STAT3 short interfering (si)RNA treatment or STAT3 siRNA treatment alone. Similarly, a cell counting kit-8 assay was used to detect the proliferation potential of SW480 cells. The protein expression levels of USP22, STAT3 and MMP9 were detected by immunohistochemistry in colon cancer tissue microarrays (TMAs) and the correlation between USP22, STAT3 and MMP9 was analyzed. USP22/STAT3 co-depletion partly rescued the MMP9 proteolytic activity and invasion of SW480 cells, compared with that of STAT3 depletion alone. However, the proliferation of USP22/STAT3si-SW480 cells was decreased compared with that of STAT3si-SW480 cells. USP22 expression was positively correlated with STAT3 and MMP9 expression in colon cancer TMAs. In conclusion, USP22 attenuated the invasion capacity of colon cancer cells by inhibiting the STAT3/MMP9 signaling pathway.

KLF5 inhibits angiogenesis in PTEN-deficient prostate cancer by attenuating AKT activation and subsequent HIF1α accumulation

Background

KLF5 is a basic transcriptional factor that regulates multiple physiopathological processes. Our recent study showed that deletion of Klf5 in mouse prostate promotes tumorigenesis initiated by the deletion of Pten. While molecular characterization of Klf5-null tumors suggested that angiogenesis was partially responsible for tumor promotion, the precise function and mechanism of KLF5 deletion in prostate tumor angiogenesis remain unclear.

Results

Applying histological staining to Pten-null mouse prostates, we observed that deletion of Klf5 significantly increased the number of microvessels, accompanied by the upregulation of multiple angiogenesis-related genes based on microarray analysis with MetaCore software. In human umbilical vein endothelial cells (HuVECs), tube formation and migration, both of which are indicators of angiogenic activities, were decreased by conditioned media from PC-3 and DU 145 human prostate cancer cells with KLF5 overexpression, but increased by media from cells with KLF5 knockdown. HIF1α, a key angiogenesis inducer, was upregulated by KLF5 loss at the protein but not the mRNA level in both mouse tissues and human cell lines, as determined by immunohistochemical staining, real-time RT-PCR and Western blotting. Consistently, KLF5 loss also upregulated VEGF and PDGF, two pro-angiogenic mediators of HIF1α function, as analyzed by immunohistochemical staining in mouse tissues and ELISA in conditioned media. Mechanistically, AKT activity, which caused the accumulation of HIF1α, was increased by KLF5 knockout or knockdown but decreased by KLF5 overexpression. PI3K/AKT inhibitors consistently abolished the effects of KLF5 knockdown on angiogenic activity, HIF1α accumulation, and VEGF and PDGF expression.

Conclusion

KLF5 loss enhances tumor angiogenesis by attenuating PI3K/AKT signaling and subsequent accumulation of HIF1α in PTEN deficient prostate tumors.

Electronic supplementary material

The online version of this article (doi:10.1186/s12943-015-0365-6) contains supplementary material, which is available to authorized users.

The Rb-E2F transcriptional regulatory pathway in tumor angiogenesis and metastasis

The retinoblastoma tumor suppressor protein Rb plays a major role in regulating G1/S transition and is a critical regulator of cell proliferation. Rb protein exerts its growth regulatory properties mainly by physically interacting with the transcriptionally active members of the E2F transcription factor family, especially E2Fs 1, 2, and 3. Given its critical role in regulating cell proliferation, it is not surprising that Rb is inactivated in almost all tumors, either through the mutation of Rb gene itself or through the mutations of its upstream regulators including K-Ras and INK4. Recent studies have revealed a significant role for Rb and its downstream effectors, especially E2Fs, in regulating various aspects of tumor progression, angiogenesis, and metastasis. Thus, components of the Rb-E2F pathway have been shown to regulate the expression of genes involved in angiogenesis, including VEGF and VEGFR, genes involved in epithelial-mesenchymal transition including E-cadherin and ZEB proteins, and genes involved in invasion and migration like matrix metalloproteinases. Rb has also been shown to play a major role in the functioning of normal and cancer stem cells; further, Rb and E2F appear to play a regulatory role in the energy metabolism of cancer cells. These findings raise the possibility that mutational events that initiate tumorigenesis by inducing uncontrolled cell proliferation might also contribute to the progression and metastasis of cancers through the mediation of the Rb-E2F transcriptional regulatory pathway. This review highlights these recent studies on tumor promoting functions of the Rb-E2F pathway.

Hypoxia and P. gingivalis synergistically induce HIF-1 and NF-κB activation in PDL cells and periodontal diseases

Periodontitis is characterized by deep periodontal pockets favoring the proliferation of anaerobic bacteria like Porphyromonas gingivalis (P. gingivalis), a periodontal pathogen frequently observed in patients suffering from periodontal inflammation. Therefore, the aim of the present study was to investigate the signaling pathways activated by lipopolysaccharide (LPS) of P. gingivalis (LPS-PG) and hypoxia in periodontal ligament (PDL) cells. The relevant transcription factors nuclear factor-kappa B (NF-κB) and hypoxia inducible factor-1 (HIF-1) were determined. In addition, we analyzed the expression of interleukin- (IL-) 1β, matrix metalloproteinase-1 (MMP-1), and vascular endothelial growth factor (VEGF) in PDL cells on mRNA and protein level. This was accomplished by immunohistochemistry of healthy and inflamed periodontal tissues. We detected time-dependent additive effects of LPS-PG and hypoxia on NF-κB and HIF-1α activation in PDL cells followed by an upregulation of IL-1β, MMP-1, and VEGF expression. Immunohistochemistry performed on tissue samples of gingivitis and periodontitis displayed an increase of NF-κB, HIF-1, and VEGF immunoreactivity in accordance with disease progression validating the importance of the in vitro results. To conclude, the present study underlines the significance of NF-κB and HIF-1α and their target genes VEGF, IL-1β, and MMP-1 in P. gingivalis and hypoxia induced periodontal inflammatory processes.

The CCL2 chemokine is a negative regulator of autophagy and necrosis in luminal B breast cancer cells

Luminal A and B breast cancers are the most prevalent forms of breast cancer diagnosed in women. Compared to luminal A breast cancer patients, patients with luminal B breast cancers experience increased disease recurrence and lower overall survival. The mechanisms that regulate the luminal B subtype remain poorly understood. The chemokine CCL2 is overexpressed in breast cancer, correlating with poor patient prognosis. The purpose of this study was to determine the role of CCL2 expression in luminal B breast cancer cells. Breast tissues, MMTV-PyVmT and MMTV-Neu transgenic mammary tumors forming luminal B-like lesions, were immunostained for CCL2 expression. To determine the role of CCL2 in breast cancer cells, CCL2 gene expression was silenced in mammary tumor tissues and cells using TAT cell-penetrating peptides non-covalently cross linked to siRNAs (Ca-TAT/siRNA). CCL2 expression was examined by ELISA and flow cytometry. Cell growth and survival were analyzed by flow cytometry, immunocytochemistry, and fluorescence microscopy. CCL2 expression was significantly increased in luminal B breast tumors, MMTV- PyVmT and MMTV-Neu mammary tumors, compared or normal breast tissue or luminal A breast tumors. Ca-TAT delivery of CCL2 siRNAs significantly reduced CCL2 expression in PyVmT mammary tumors, and decreased cell proliferation and survival. CCL2 gene silencing in PyVmT carcinoma cells or BT474 luminal B breast cancer cells decreased cell growth and viability associated with increased necrosis and autophagy. CCL2 expression is overexpressed in luminal B breast cancer cells and is important for regulating cell growth and survival by inhibiting necrosis and autophagy.