Signaling angiogenesis via p42/p44 MAP kinase and hypoxia

Hypoxia Treatment of Adipose Mesenchymal Stem Cells Promotes the Growth of Dermal Papilla Cells via HIF-1α and ERK1/2 Signaling Pathways

Dermal papilla cells (DPCs) cultured in vitro induce hair follicle formation. Using a hypoxic microenvironment to culture adipose mesenchymal stem cells (ADSCs) can promote hair follicle growth. However, the exact molecular mechanisms underlying this process remain unclear. In this study, ADSCs and DPCs from Arbas Cashmere goats were used. A hypoxic microenvironment promoted the proliferation of ADSCs and increased the pluripotency of ADSCs. The growth factors vascular endothelial growth factor (VEGF), basic fibroblast growth factor (bFGF), and platelet-derived growth factor (PDGF) were upregulated in ADSCs in the hypoxia-conditioned medium (Hypo-cm). Hypo-cm also enhanced the ability of DPCs to induce hair follicle formation. Inhibitors of the ERK1/2 signaling pathway caused the expressions of growth factors that increased in hypoxic microenvironments to decrease; moreover, hypoxia-inducible factor-1α (HIF-1α) increased the expression levels of VEGF, bFGF, and PDGF and inhibited the expression of bone morphogenic protein 7 (BMP7). In conclusion, these findings improve the theoretical basis for the development of gene therapy drugs for the treatment of alopecia areata and hair thinning.

Low-Level Laser Therapy Induces Melanoma Tumor Growth by Promoting Angiogenesis

The effects of low-level laser therapy (LLLT) on tumor growth are inconsistent. In this study, we investigated the effects of LLLT on melanoma tumor growth and angiogenesis. C57/BL6 mice were challenged with B16F10 melanoma cells and treated with LLLT for 5 consecutive days; untreated mice were used as controls. Tumor weight, angiogenesis, immunohistochemistry, and protein levels were compared between the treated and untreated mice. In an in vitro experiment, B16F10 cells were treated with LLLT. Proteins were extracted and subjected to Western blot analysis for analyzing signaling pathways. Compared with the findings in the untreated mice, tumor weight substantially increased in the treated mice. Both immunohistochemical and Western blot analyses revealed markedly increased levels of CD31, a biomarker of vascular differentiation, in the LLLT group. In B16F10 cells, LLLT considerably induced the phosphorylation of extracellular signal-regulated kinase (ERK), which, in turn, phosphorylated p38 mitogen-activated protein kinase (MAPK). Furthermore, LLLT induced the expression of vascular endothelial growth factor, but not hypoxia-inducible factor-1α, through the ERK/p38 MAKP signaling pathways. Our findings indicate that LLLT induces melanoma tumor growth by promoting angiogenesis. Therefore, it should be avoided in patients with melanoma.

Annexin A2 promotes angiogenesis after ischemic stroke via annexin A2 receptor - AKT/ERK pathways

Promoting angiogenesis to restore circulation to the ischemic tissue is still an important therapeutic target in stroke. Our group and others previously reported that the Ca²⁺-regulated, phospholipid-and membrane-binding protein-Annexin A2 (ANXA2) functions in cerebrovascular integrity and retinal neoangiogenesis. Here, we hypothesized that ANXA2 may regulate angiogenesis after stroke, ultimately improve neurological outcomes. Compared with wild type (WT) mice, the density of microvessels in brain and the number of new vessels sprouting from aortic ring were significantly increased in Anxa2 knock-in (Anxa2 KI) mice. After focal cerebral ischemia, proliferation of brain endothelial cells in Anxa2 KI mice was significantly elevated at 7 days post-stroke, which further improved behavioral recovery. To assess the pro-angiogenic mechanisms of ANXA2, we used brain endothelial cells cultures to investigate its effects on cell tube-numbers and migration. Recombinant ANXA2 increased tube-numbers and migration of brain endothelial cells either under normal condition or after oxygen glucose deprivation (OGD) injury. Co-immunoprecipitation experiments demonstrated that these protective effects of recombinant ANXA2 were regulated by interaction with ANXA2 receptor (A2R), a protein found in cancer cells that can interact with ANXA2 to promote cell migration and proliferation, and the ability of ANXA2-A2R to activate AKT/ERK pathways. Inhibition of AKT/ERK diminished recombinant ANXA2-induced angiogenesis in vitro. Taken together, our study indicates that ANXA2 might be involved in angiogenesis after ischemic stroke. Further investigation of ANXA2-A2R will provide a new therapeutic target for stroke.

Tocilizumab (TCZ) Decreases Angiogenesis in Rheumatoid Arthritis Through Its Regulatory Effect on miR-146a-5p and EMMPRIN/CD147

Background

Angiogenesis is a major contributor to the development of inflammation during Rheumatoid arthritis (RA), as the vascularization of the pannus provides nutrients and oxygen for the infiltrating immune cells and proliferating synoviocytes. Tocilizumab (TCZ) is an anti-IL-6 receptor antibody that is used in the treatment of RA patients, and has been shown to exert anti-inflammatory effects. However, its effects on angiogenesis are not fully elucidated, and the molecular mechanisms regulating this effect are unknown.

Methods

We evaluated the concentrations of several pro- and anti-angiogenic factors and the expression levels of several microRNA molecules that are associated with RA and angiogenesis in serum samples obtained from 40 RA patients, before and 4 months after the initiation of TCZ treatment. Additionally, we used an in vitro co-culture system of fibroblasts (the HT1080 cell line) and monocytes (the U937 cell line) to explore the mechanisms of TCZ action.

Results

Serum samples from RA patients treated with TCZ exhibited reduced circulating levels of EMMPRIN/CD147, enhanced expression of circulating miR-146a-5p and miR-150-5p, and reduced the angiogenic potential as was manifested by the lower number of tube-like structures that were formed by EaHy926 endothelial cell line. In vitro, the accumulation in the supernatants of the pro-angiogenic factors EMMPRIN, VEGF and MMP-9 was increased by co-culturing the HT1080 fibroblasts and the U937 monocytes, while the accumulation of the anti-angiogenic factor thrombospondin-1 (Tsp-1) and the expression levels of miR-146a-5p were reduced. Transfection of HT1080 cells with the miR-146a-5p mimic, decreased the accumulation of EMMPRIN, VEGF and MMP-9. When we neutralized EMMPRIN with a blocking antibody, the supernatants derived from these co-cultures displayed reduced migration, proliferation and tube formation in the functional assays.

Conclusions

Our findings implicate miR-146a-5p in the regulation of EMMPRIN and propose that TCZ affects angiogenesis through its effects on EMMPRIN and miR-146a-5p.

Diallyl Trisulfide Suppresses High-Glucose-Induced Cardiomyocyte Apoptosis by Targeting Reactive Oxygen Species-Mediated Hypoxia-Inducible Factor-1α/Insulin-like Growth Factor Binding Protein 3 Activation

It has been reported that 80% of diabetic patients die due to cardiovascular diseases. We previously demonstrated that activated hypoxia-inducible factor-1α (HIF-1 α)/insulin-like growth factor binding protein-3 (IGFBP-3) signaling by reactive oxygen species (ROS)-regulated prolyl hydroxylase domain-containing protein (PHD) is involved in high-glucose (HG)-induced cardiac apoptosis. Diallyl trisulfide (DATS), a garlic component, shows the strongest inhibitory effect on diabetic cardiomyopathy. In this study, we investigated whether HIF-1α/IGFBP-3 signaling governs the antiapoptotic effect by DATS on HG-exposed cardiomyocytes. It was observed that significantly increased levels of cell apoptosis and decreased Akt phosphorylation were reversed by DATS in HG-exposed cardiac cells. H₂O₂ and PHD small interfering RNA treatments increased HIF-1α and IGFBP-3 protein levels, which were decreased by DATS treatment. Overexpression of HIF-1α and IGFBP-3 increased HG-induced cell apoptosis, which was suppressed by DATS. The coimmunoprecipitation assay results showed that DATS not only increased the IGF-1 level and reduced IGFBP-3 level but also suppressed their extracellular association for cardiac cells exposed to HG. Experiments using neonatal cardiomyocytes and hearts showed similar results. These findings indicate that the effect of ROS-regulated PHD on the activation of HIF-1α/IGFBP-3 signaling governs the antiapoptotic effect by DATS on HG-exposed cardiomyocytes.

Hypoxia-Inducible Factor (HIF): Fuel for Cancer Progression

Hypoxia is an integral part of the tumor microenvironment, caused primarily due to rapidly multiplying tumor cells and a lack of proper blood supply. Among the major hypoxic pathways, HIF-1 transcription factor activation is one of the widely investigated pathways in the hypoxic tumor microenvironment (TME). HIF-1 is known to activate several adaptive reactions in response to oxygen deficiency in tumor cells. HIF-1 has two subunits, HIF-1β (constitutive) and HIF-1α (inducible). The HIF-1α expression is largely regulated via various cytokines (through PI3K-ACT-mTOR signals), which involves the cascading of several growth factors and oncogenic cascades. These events lead to the loss of cellular tumor suppressant activity through changes in the level of oxygen via oxygen-dependent and oxygen-independent pathways. The significant and crucial role of HIF in cancer progression and its underlying mechanisms have gained much attention lately among the translational researchers in the fields of cancer and biological sciences, which have enabled them to correlate these mechanisms with various other disease modalities. In the present review, we have summarized the key findings related to the role of HIF in the progression of tumors.

Photobiomodulation Therapy to Promote Angiogenesis in Diabetic Mice with Hindlimb Ischemia

Objective: To assess whether photobiomodulation therapy (PBMT) induces angiogenesis in diabetic mice with hindlimb ischemia (HLI). Background: Patients with diabetes mellitus (DM) are at high risk of developing peripheral arterial disease (PAD) in the lower extremities. PBMT has been shown to promote angiogenesis both in vitro and in vivo and could be a treatment for DM patients with PAD. Methods: Femoral artery ligation/excision in mice was performed to induce HLI as an animal model of PAD. PBMT at a dose of 660 nm and 1.91 J/cm² was delivered for 10 min on 5 consecutive days after the HLI surgery. Control mice received HLI only. Mice in the DM group were injected with streptozocin to induce diabetes before HLI surgery. Mice in the laser and DM+ laser groups received both HLI and PBMT, and the latter group had induced DM. After the laser treatment, lower limb blood flow was evaluated by laser Doppler. The capillary density and CD31 were analyzed by immunofluorescence staining, and protein levels of vascular endothelial growth factor (VEGF)-A, hypoxia-inducible factor-1α (HIF-1α), inducible nitric oxide synthase (iNOS), endothelial nitric oxide synthase (eNOS), and extracellular signal-regulated kinases (ERK) were measured by Western blotting of tissue samples. Results: Compared with the control and DM mice, the laser and DM+ laser groups had more than double the capillary density and blood perfusion rate. Levels of CD31 and VEGF-A proteins in groups that received laser were increased by 1.9- to 3.2-fold compared with groups that did not undergo laser treatment. Animals treated with PBMT exhibited significantly increased HIF-1α expression and ERK phosphorylation compared with animals that did not receive this treatment, and the amount of phospho-eNOS and iNOS increased and decreased, respectively. Conclusions: PBMT can induce therapeutic angiogenesis, indicating that low intensity laser could be a novel treatment for PAD patients.

Signaling pathways in intestinal homeostasis and colorectal cancer: KRAS at centre stage

The intestinal epithelium acts as a physical barrier that separates the intestinal microbiota from the host and is critical for preserving intestinal homeostasis. The barrier is formed by tightly linked intestinal epithelial cells (IECs) (i.e. enterocytes, goblet cells, neuroendocrine cells, tuft cells, Paneth cells, and M cells), which constantly self-renew and shed. IECs also communicate with microbiota, coordinate innate and adaptive effector cell functions. In this review, we summarize the signaling pathways contributing to intestinal cell fates and homeostasis functions. We focus especially on intestinal stem cell proliferation, cell junction formation, remodelling, hypoxia, the impact of intestinal microbiota, the immune system, inflammation, and metabolism. Recognizing the critical role of KRAS mutants in colorectal cancer, we highlight the connections of KRAS signaling pathways in coordinating these functions. Furthermore, we review the impact of KRAS colorectal cancer mutants on pathway rewiring associated with disruption and dysfunction of the normal intestinal homeostasis. Given that KRAS is still considered undruggable and the development of treatments that directly target KRAS are unlikely, we discuss the suitability of targeting pathways downstream of KRAS as well as alterations of cell extrinsic/microenvironmental factors as possible targets for modulating signaling pathways in colorectal cancer.

Long non-coding RNA HNF1A-AS1 upregulates OTX1 to enhance angiogenesis in colon cancer via the binding of transcription factor PBX3

Colon cancer shows characteristics of metastasis, which is associated with angiogenesis. Increasing evidence highlights long non-coding RNAs (lncRNAs) as important participants in angiogenesis of cancers, including colon cancer. Hence, this study investigated the role of HNF1A-AS1 in angiogenesis of colon cancer. RT-qPCR and Western blot analysis were applied to detect HNF1A-AS1 and OTX1 expression in colon cancer tissues and cell lines. Then the interactions among HNF1A-AS1, PBX3, OTX1 and ERK/MAPK pathway were evaluated with RNA pull-down, RIP, ChIP and dual-luciferase reporter gene assays. Next, HCT116 and SW620 cells were treated with si-HNF1A-AS1 and/or oe-OTX1 plasmids to assess the effects of HNF1A-AS1 and OTX1 on angiogenesis, which was further evaluated in nude mice injected with SW620 cells transfected with sh-HNF1A-AS1 or sh-OTX1 lentivirus. HNF1A-AS1 and OTX1 were highly expressed in colon cancer. Silencing of HNF1A-AS1 inhibited angiogenesis of colon cancer in vivo and in vitro. HNF1A-AS1 increased the OTX1 expression by binding to transcription factor PBX3 to promote angiogenesis in colon cancer. Further, HNF1A-AS1 upregulated OTX1 to activate the ERK/MAPK pathway. Altogether, our findings identified HNF1A-AS1 as a tumor-promoting RNA in colon cancer, which could serve as a potential therapeutic target for colon cancer treatment.

Effects of structural distinction in neodymium nanoparticle for therapeutic application in aberrant angiogenesis

In the present study we analyzed the effect of structural distinction in neodymium nanostructures for modulating angiogenic process as the strategy for identifying biocompatible Nano therapeutics for biomedical applications. We observed structural dependence of Nd nanoparticles on biocompatibility, the spherical polymorphs showed better biocompatibility when compared with cuboidal and nanorod shaped polymorphs of neodymium. The Nd nanopolymorphs in spherical morphology exhibited least redox modulating effect compared to cuboidal shaped that was higher when compared to Nd nanorods. The efficacy of the Nd Nanopolymorphs to induce biological effect in particular on angiogenic process was observed to be directly related to the polymorphs ability to modulate redox signaling. The redox signaling was observed to be via PKM2-NOX4 signaling pathways. Further the results demonstrated that ROS generated by cuboid and rod shaped nanopolymorphs activated the pro-angiogenic factors namely VE-cadherin, HIF 1α, VEGF and VEGFR-2 to facilitate the angiogenic process. The manuscript highlights the importance of rare earth metal nanoparticles in modulating biological process for therapeutic interventions. The present study opens up a new domain in developing novel biocompatible therapeutics based on rare earth metal nanoparticles for regulating disease pathophysiology.

Sophocarpine Inhibits Tumorgenesis of Colorectal Cancer via Downregulation of MEK/ERK/VEGF Pathway

Colorectal cancer (CRC) is one of the most common malignant tumors and the third leading cause of cancer-related deaths in the world. It was reported that sophocarpine could attenuate the progression of CRC in mice. However, the mechanisms by which sophocarpine regulate the proliferation and migration in CRC remain unclear. Thus, this study aimed to investigate anti-tumor mechanisms of sophocarpine in CRC cells. CCK-8 assay, wound healing assay and transwell migration were used to detect cell proliferation and migration, respectively. In addition, Western blotting and enzyme-linked immunosorbent assay (ELISA) were used to further detect protein expressions and cytokines in vitro. The results revealed that sophocarpine significantly inhibited proliferation in HCT116 and SW620 cells, respectively. Meanwhile, sophocarpine inhibited CRC cells migration via downregulation of the levels of N-cadherin, matrix metalloproteinase (MMP)-9, phosphorylated extracellular signal-regulated kinase (p-ERK), p-mitogen-activated protein kinase kinase (MEK), vascular endothelial growth factor (VEGF)-A, VEGF-C and VEGF-D. Moreover, overexpression of MEK reversed the anti-migration effects of sophocarpine on CRC cells via upregulation of VEGF-A/C/D. Our findings indicated that sophocarpine could inhibit CRC cells migration via downregulation of MEK/ERK/VEGF pathway. Thus, sophocarpine may act as a potential agent for the treatment of CRC.

Fabrication of plumbagin on silver nanoframework for tunable redox modulation: Implications for therapeutic angiogenesis

The redox state of the endothelial cells plays a key role in the regulation of the angiogenic process. The modulation of the redox state of endothelial cells (ECs) could be a viable target to alter angiogenic response. In the present work, we synthesized a redox modulator by caging 5-hydroxy 2-methyl 1, 4-napthoquinone (Plumbagin) on silver nano framework (PCSN) for tunable reactive oxygen species (ROS) inductive property and tested its role in ECs during angiogenic response in physiological and stimulated conditions. In physiological conditions, the redox modulators induced the angiogenic response by establishing ECs cell-cell contact in tube formation model, chorio allontoic membrane, and aortic ring model. The molecular mechanism of angiogenic response was induced by vascular endothelial growth factor receptor 2 (VEGFR2)/p42-mitogen-activated protein kinase signaling pathway. Under stimulation, by mimicking tumor angiogenic conditions it induced cytotoxicity by generation of excessive ROS and inhibited the angiogenic response by the loss of spatiotemporal regulation of matrix metalloproteases, which prevents the tubular network formation in ECs and poly-ADP ribose modification of VEGF. The mechanism of opposing effects of PCSN was due to modulation of PKM2 enzyme activity, which increased the EC sensitivity to ROS and inhibited EC survival in stimulated condition. In normal conditions, the endogenous reactive states of NOX4 enzyme helped the EC survival. The results indicated that a threshold ROS level exists in ECs that promote angiogenesis and any significant enhancement in its level by redox modulator inhibits angiogenesis. The study provides the cues for the development of redox-based therapeutic molecules to cure the disease-associated aberrant angiogenesis.

Apatinib affect VEGF-mediated cell proliferation, migration, invasion via blocking VEGFR2/RAF/MEK/ERK and PI3K/AKT pathways in cholangiocarcinoma cell

BACKGROUND

Cholangiocarcinoma (CCA) is a form of cancer that easily aggress to contiguous structures. Vascular endothelial growth factor (VEGF) and VEGF receptor 2 (VEGFR2) are increased in majority species of cancers and suppress tumor progression by blocking VEGF/VEGFR2. Apatinib is a highly selective VEGFR2 antagonist which has inhibitive effect on antiapoptotic and cell growth in CCA. While, the effect of apatinib cell migration and invasion in CCA is still unknown.

METHODS

CCA cell lines QBC939 and TFK-1 were transfected with siKDR to establish the KDR function loss cell model, and recombined human VEGF (rhVEGF) protein was added into the culture medium to enhance the VEGF expression. RT-qPCR and western bloting were used to detect the mRNA and protein expression levels of VEGFR2 to investigate whether it was effectively repressed or activated with rhVEGF or apatinib treatment. Then, MTT, wound healing assay, and transwell matrix assay were applied to measure the effect of apatinib and rhVEGF on cell viability, migration and invasion, respectively.

RESULTS

The mRNA and protein expressions of VEGFR2 were significantly reduced with KDR RNAi in both QBC939 and TFK-1 cells, and rhVEGF treatment increased these expression levels (p < 0.05). Apatinib dramatically suppressed VEGF-mediated cell migration and invasion at the concentration of 100 nM treatment and significantly decreased the expression of metastasis-associated protein such as Slug, snail and MMP9. Moreover, all of these inhibiting effects of apatinib depended on the VEGFR2 existence. In addition, VEGFR2/RAF/MEK/ERK and PI3K/AKT signal pathways were enhanced by the introduction of rhVEGF, but were dramatically suppressed after the apatinib treatment.

CONCLUSION

Apatinib inhibit VEGF-mediated cell migration and invasion in CCA cell lines via inhibiting the VEGFR2/RAF/MEK/ERK and PI3K/AKT pathways. It will be a potentially effective targeted drug for CCA.

Cinnamaldehyde accelerates wound healing by promoting angiogenesis via up-regulation of PI3K and MAPK signaling pathways

The bark of Cinnamomum cassia (C. cassia) has been used for the management of coronary heart disease (CHD) and diabetes mellitus. C. cassia may target the vasculature, as it stimulates angiogenesis, promotes blood circulation and wound healing. However, the active components and working mechanisms of C. cassia are not fully elucidated. The Shexiang Baoxin pill (SBP), which consists of seven medicinal materials, including C. cassia etc., is widely used as a traditional Chinese patent medicine for the treatment of CHD. Here, 22 single effective components of SBP were evaluated against the human umbilical vein endothelial cells (HUVECs). We demonstrated that in HUVECs, cinnamaldehyde (CA) stimulated proliferation, migration, and tube formation. CA also activated the phosphatidylinositol 3-kinase (PI3K) and mitogen-activated protein kinase (MAPK) pathways. Furthermore, the secretion of vascular endothelial growth factor (VEGF) from HUVECs was increased by CA. In vivo, CA partially restored intersegmental vessels in zebrafish pretreated with PTK787, which is a selective inhibitor for vascular endothelial growth factor receptor (VEGFR). CA also showed pro-angiogenic efficacy in the Matrigel plug assay. Additionally, CA attenuated wound sizes in a cutaneous wound model, and elevated VEGF protein and CD31-positive vascular density at the margin of these wounds. These results illustrate that CA accelerates wound healing by inducing angiogenesis in the wound area. The potential mechanism involves activation of the PI3K/AKT and MAPK signaling pathways. Such a small non-peptide molecule may have clinical applications for promoting therapeutic angiogenesis in chronic diabetic wounds and myocardial infarction.

Cardiac glycosides suppress the maintenance of stemness and malignancy via inhibiting HIF-1α in human glioma stem cells

Tissue hypoxia contributes to solid tumor pathogenesis by activating a series of adaptive programs. We previously showed that hypoxia promotes the preferential expansion and maintenance of CD133 positive human glioma stem cells (GSC) in a hypoxia inducible factor 1 alpha (HIF-1α)-dependent mechanism. Here, we examined the activity of digitoxin (DT), a cardiac glycoside and a putative inhibitor of HIF-1α, on human GSC in vitro and in vivo. During hypoxic conditions (1% O₂), we observed the effect of DT on the intracellular level of HIF-1α and the extracellular level of vascular endothelial growth factor (VEGF) in human GSC. We found that DT at clinically achievable concentrations, suppressed HIF-1α accumulation during hypoxic conditions in human GSC and established glioma cell lines. DT treatment also significantly attenuated hypoxia-induced expression of VEGF, a downstream target of HIF-1α. Exposure to DT also reduced hypoxia-induced activation of the extracellular signal-regulated kinase 1/2 (ERK1/2) signaling pathway. Furthermore, DT potently inhibited neurosphere formation, and decreased CD133 expression even at concentrations that were not overtly cytotoxic. Lastly, treatment with DT reduced GSC engraftment in an in vivo xenograft model of glioblastoma. Intraperitoneal injections of DT significantly inhibited the growth of established glioblastoma xenografts, and suppressed expression of HIF-1α and carbonic anhydrase (CA9), a surrogate marker of hypoxia. Taken together, these results suggest that DT at clinically achievable concentration functions as an inhibitor of HIF-1α, worthy of further investigations in the therapy of glioblastoma.

Molecular Regulation of Sprouting Angiogenesis

The term angiogenesis arose in the 18th century. Several studies over the next 100 years laid the groundwork for initial studies performed by the Folkman laboratory, which were at first met with some opposition. Once overcome, the angiogenesis field has flourished due to studies on tumor angiogenesis and various developmental models that can be genetically manipulated, including mice and zebrafish. In addition, new discoveries have been aided by the ability to isolate primary endothelial cells, which has allowed dissection of various steps within angiogenesis. This review will summarize the molecular events that control angiogenesis downstream of biochemical factors such as growth factors, cytokines, chemokines, hypoxia-inducible factors (HIFs), and lipids. These and other stimuli have been linked to regulation of junctional molecules and cell surface receptors. In addition, the contribution of cytoskeletal elements and regulatory proteins has revealed an intricate role for mobilization of actin, microtubules, and intermediate filaments in response to cues that activate the endothelium. Activating stimuli also affect various focal adhesion proteins, scaffold proteins, intracellular kinases, and second messengers. Finally, metalloproteinases, which facilitate matrix degradation and the formation of new blood vessels, are discussed, along with our knowledge of crosstalk between the various subclasses of these molecules throughout the text. Compr Physiol 8:153-235, 2018.

Long non-coding RNA MALAT1 promotes gastric cancer tumorigenicity and metastasis by regulating vasculogenic mimicry and angiogenesis

MALAT1 is an oncogenic long non-coding RNA that has been found to promote the proliferation of many malignant cell types and non-malignant human umbilical vein endothelial cells (HUVECs). However, the functions of MALAT1 in vasculogenic mimicry (VM) and angiogenesis and the potential mechanisms responsible have not yet been investigated in any malignancy. Here, in situ hybridization and CD31/periodic acid-Schiff double staining of 150 gastric cancer (GC) clinical specimens revealed that MALAT1 expression was tightly associated with densities of VM and endothelial vessels. MALAT1 knockdown markedly reduced GC cell migration, invasion, tumorigenicity, metastasis, and VM, while restricting HUVEC angiogenesis and increasing vascular permeability. Moreover, MALAT1 was found to regulate expression of VE-cadherin, β-catenin, MMPs 2 and 9, MT1-MMP, p-ERK, p-FAK, and p-paxillin, which have been established as classical markers of VM and angiogenesis and components of associated signaling pathways. Consistent with this, the p-ERK inhibitors U0126 and PD98059 both effectively blocked GC cell VM. In conclusion, MALAT1 can promote tumorigenicity and metastasis in GC by facilitating VM and angiogenesis via the VE-cadherin/β-catenin complex and ERK/MMP and FAK/paxillin signaling pathways.

A novel synthetic small molecule YF-452 inhibits tumor growth through antiangiogenesis by suppressing VEGF receptor 2 signaling

Tumor angiogenesis is characterized by abnormal vessel morphology, endowing tumor with highly hypoxia and unresponsive toward treatment. To date, mounting angiogenic factors have been discovered as therapeutic targets in antiangiogenic drug development. Among them, vascular endothelial growth factor receptor 2 (VEGFR2) inhibitors exerts potent antiangiogenic activity in tumor therapy. Therefore, it may provide a valid strategy for cancer treatment through targeting the tumor angiogenesis via VEGFR2 pathway. In this study, we established a high-profile compounds library and certificated a novel compound named N-(N-pyrrolidylacetyl)-9-(4-bromobenzyl)-1,3,4,9-tetrahydro-β-carboline (YF-452), which remarkably inhibited the migration, invasion and tube-like structure formation of human umbilical vein endothelial cells (HUVECs) with little toxicity invitro. Rat thoracic aorta ring assay indicated that YF-452 significantly blocked the formation of microvascular exvivo. In addition, YF-452 inhibited angiogenesis in chick chorioallantoic membrane (CAM) and mouse corneal micropocket assays. Moreover, YF-452 remarkably suppressed tumor growth in xenografts mice model. Furthermore, investigation of molecular mechanism revealed that YF-452 inhibited VEGF-induced phosphorylation of VEGFR2 kinase and the downstream protein kinases including extracellular signal regulated kinase (ERK), focal adhesion kinase (FAK) and Src. These results indicate that YF-452 inhibits angiogenesis and may be a potential antiangiogenic drug candidate for cancer therapy.

Inhibition of 5-lipoxygenase suppresses vascular endothelial growth factor-induced angiogenesis in endothelial cells

5-Lipoxygenase (5-LOX) is an enzyme that converts arachidonic acid from the cell membrane into leukotriene, a signal lipid mediator. 5-LOX deficiency markedly attenuates the formation of aneurysms in knockout mice. In addition, Zileuton, a clinical drug targeting 5-LOX, is used for treatment of asthma. However, it is unclear whether 5-LOX inhibition results in anti-angiogenic effects for applications in cancer therapy. To explore the roles of 5-LOX in angiogenesis and its potential as a therapeutic target in cancer, the effects of a newly synthesized 5-LOX inhibitor, F3, on in vitro and in vivo angiogenesis were investigated. The results showed that 5-LOX inhibition by F3 suppressed in vitro vascular endothelial growth factor (VEGF)-induced tube formation and chemo-invasion of endothelial cells (ECs). 5-LOX inhibition also decreased VEGF-induced extracellular signal-regulated kinase (ERK) phosphorylation in ECs. Notably, 5-LOX knockdown phenocopied the anti-angiogenic activity of the 5-LOX inhibitor F3 in a concentration-dependent manner. F3 did not affect the activities of VEGF receptor 2 or AKT. In vivo, the compound significantly inhibited the formation of the chorioallantoic membrane at nontoxic doses. These results demonstrated that 5-LOX played an important role in angiogenesis and that its inhibitor F3 could be a new anti-angiogenic agent targeting VEGF signaling.

Miniaturizing VEGF: Peptides mimicking the discontinuous VEGF receptor-binding site modulate the angiogenic response

The angiogenic properties of VEGF are mediated through the binding of VEGF to its receptor VEGFR2. The VEGF/VEGFR interface is constituted by a discontinuous binding region distributed on both VEGF monomers. We attempted to reproduce this discontinuous binding site by covalently linking into a single molecular entity two VEGF segments involved in receptor recognition. We designed and synthesized by chemical ligation a set of peptides differing in length and flexibility of the molecular linker joining the two VEGF segments. The biological activity of the peptides was characterized in vitro and in vivo showing a VEGF-like activity. The most biologically active mini-VEGF was further analyzed by NMR to determine the atomic details of its interaction with the receptor.

Angiotensin-(1-7) Decreases Cell Growth and Angiogenesis of Human Nasopharyngeal Carcinoma Xenografts

Angiotensin-(1-7) [Ang-(1-7)] is an endogenous, heptapeptide hormone acting through the Mas receptor (MasR), with antiproliferative and antiangiogenic properties. Recent studies have shown that Ang-(1-7) has an antiproliferative action on lung adenocarcinoma cells and prostate cancer cells. In this study, we report that MasR levels were significantly upregulated in nasopharyngeal carcinoma (NPC) specimens and NPC cell lines. Viral vector-mediated expression of Ang-(1-7) dramatically suppressed NPC cell proliferation and migration in vitro. These effects were completely blocked by the specific Ang-(1-7) receptor antagonist A-779, suggesting that they are mediated by the Ang-(1-7) receptor Mas. In this study, Ang-(1-7) not only caused a significant reduction in the growth of human nasopharyngeal xenografts, but also markedly decreased vessel density, suggesting that the heptapeptide inhibits angiogenesis to reduce tumor size. Mechanistic investigations revealed that Ang-(1-7) inhibited the expression of the proangiogenic factors VEGF and PlGF. Taken together, the data suggest that upregulation of MasR could be used as a diagnostic marker of NPC and Ang-(1-7) may be a novel therapeutic agent for nasopharyngeal cancer therapy because it exerts significant antiangiogenic activity.

The Practicability of a Novel Prognostic Index (PI) Model and Comparison with Nottingham Prognostic Index (NPI) in Stage I-III Breast Cancer Patients Undergoing Surgical Treatment

Background

Previous studies have indicated the prognostic value of various laboratory parameters in cancer patients. This study was to establish a prognostic index (PI) model for breast cancer patients based on the potential prognostic factors.

Methods

A retrospective study of 1661 breast cancer patients who underwent surgical treatment between January 2002 and December 2008 at Sun Yat-sen University Cancer Center was conducted. Multivariate analysis (Cox regression model) was performed to determine the independent prognostic factors and a prognostic index (PI) model was devised based on these factors. Survival analyses were used to estimate the prognostic value of PI, and the discriminatory ability of PI was compared with Nottingham Prognostic Index (NPI) by evaluating the area under the receiver operating characteristics curves (AUC).

Results

The mean survival time of all participants was 123.6 months. The preoperative globulin >30.0g/L, triglyceride >1.10mmol/L and fibrinogen >2.83g/L were identified as risk factors for shorter cancer-specific survival. The novel prognostic index model was established and enrolled patients were classified as low- (1168 patients, 70.3%), moderate- (410 patients, 24.7%) and high-risk groups (83 patients, 5.0%), respectively. Compared with the low-risk group, higher risks of poor clinical outcome were indicated in the moderate-risk group [Hazard ratio (HR): 1.513, 95% confidence interval (CI): 1.169–1.959, p = 0.002] and high-risk group (HR: 2.481, 95%CI: 1.653–3.724, p< 0.001).

Conclusions

The prognostic index based on three laboratory parameters was a novel and practicable prognostic tool. It may serve as complement to help predict postoperative survival in breast cancer patients.

Biochanin A inhibits endothelial cell functions and proangiogenic pathways: implications in glioma therapy

Malignant gliomas, such as glioblastoma multiforme, are highly vascularized tumors of the central nervous system. A rich network of angiogenic vessels supporting glioma growth is an important therapeutic target in glioma therapy. In the past few years, small molecules have gained interest as multitargeting therapies for cancer. Biochanin A is a small, natural dietary isoflavone known for its anticancer potential. Previously, we have found that biochanin A inhibits invasion in human glioblastoma cells. In this study, we elucidated the antiangiogenic mechanisms of biochanin A using rat brain tumor (C6) and murine brain endothelial (bEnd.3) cells and an ex-vivo chick chorioallantoic membrane model. Biochanin A inhibited endothelial cell functions such as cell viability, migration, and invasion, as analyzed using MTT, scratch wound, and gelatin zymography assays. Activation of proangiogenic proteins (ERK/AKT/mTOR) was inhibited. Biochanin A also inhibited chemical hypoxia-inducible factor-1α and vascular endothelial growth factor in C6 cells. Results of chick chorioallantoic membrane assay showed that biochanin A inhibited blood vessel formation ex vivo. As these results suggest that biochanin A directly targets different facets of angiogenesis in vitro and ex vivo, this study provides a rationale for future preclinical evaluation of its efficacy against angiogenic gliomas.

Disruptive environmental chemicals and cellular mechanisms that confer resistance to cell death

Cell death is a process of dying within biological cells that are ceasing to function. This process is essential in regulating organism development, tissue homeostasis, and to eliminate cells in the body that are irreparably damaged. In general, dysfunction in normal cellular death is tightly linked to cancer progression. Specifically, the up-regulation of pro-survival factors, including oncogenic factors and antiapoptotic signaling pathways, and the down-regulation of pro-apoptotic factors, including tumor suppressive factors, confers resistance to cell death in tumor cells, which supports the emergence of a fully immortalized cellular phenotype. This review considers the potential relevance of ubiquitous environmental chemical exposures that have been shown to disrupt key pathways and mechanisms associated with this sort of dysfunction. Specifically, bisphenol A, chlorothalonil, dibutyl phthalate, dichlorvos, lindane, linuron, methoxychlor and oxyfluorfen are discussed as prototypical chemical disruptors; as their effects relate to resistance to cell death, as constituents within environmental mixtures and as potential contributors to environmental carcinogenesis.

Angiotensin-(1-7) Suppresses Hepatocellular Carcinoma Growth and Angiogenesis via Complex Interactions of Angiotensin II Type 1 Receptor, Angiotensin II Type 2 Receptor and Mas Receptor

We recently confirmed that angiotensin II (Ang II) type 1 receptor (AT1R) was overexpressed in hepatocellular carcinoma tissue using a murine hepatoma model. Angiotensin(Ang)-(1-7) has been found beneficial in ameliorating lung cancer and prostate cancer. Which receptor of Ang-(1-7) is activated to mediate its effects is much speculated. This study was designed to investigate the effects of Ang-(1-7) on hepatocellular carcinoma, as well as the probable mechanisms. H22 hepatoma-bearing mice were randomly divided into five groups for treatment: mock group, low-dose Ang-(1-7), high-dose Ang-(1-7), high-dose Ang-(1-7) + A779 and high-dose Ang-(1-7) + PD123319. Ang-(1-7) treatment inhibited tumor growth time- and dose-dependently by arresting tumor proliferation and promoting tumor apoptosis as well as inhibiting tumor angiogenesis. The effects of Ang-(1-7) on tumor proliferation and apoptosis were reversed by coadministration with A779 or PD123319, whereas the effects on tumor angiogenesis were completely reversed by A779 but not by PD123319. Moreover, Ang-(1-7) downregulated AT1R mRNA, upregulated mRNA levels of Ang II type 2 receptor (AT2R) and Mas receptor (MasR) and p38-MAPK phosphorylation and suppressed H22 cell-endothelial cell communication. Thus, Ang-(1-7) administration suppresses hepatocellular carcinoma via complex interactions of AT1R, AT2R and MasR and may provide a novel and promising approach for the treatment of hepatocellular carcinoma.

Hair-growth stimulation by conditioned medium from vitamin D3-activated preadipocytes in C57BL/6 mice

AIMS

Recently, immature adipocyte lineage cells have been suggested as a potential hair-growth stimulator. Diverse studies have been attempted to find methods for the preconditioning of immature adipocyte lineage cells. The present study investigates the effect of conditioned medium (CM) from vitamin D3 (Vd3) pre-activated preadipocytes on hair-growth ability.

MAIN METHODS

To test the effect of CM from Vd3 pre-activated preadipocytes on hair-growth efficiency in mice, we compared the differences in hair regenerated after injecting CM from mouse preadipocytes pre-activated with or without Vd3. Next, to determine the regulating factors, the VEGF level was measured by ELISA and angiogenesis level was evaluated by IHC. Finally, the signaling mechanism was investigated by inhibitor kinase assay and western blotting.

KEY FINDINGS

The CM from Vd3 pre-activated preadipocyte injection markedly promoted the ability of hair regeneration in mice. The VEGF levels were increased by Vd3 treatment in vitro and the CM from Vd3 pre-activated preadipocytes significantly increased the angiogenesis in vivo, suggesting the involvement of angiognensis in the hair regeneration induced by CM from pre-activated preadipocytes. In signaling study, Vd3-enhanced VEGF production was reduced by an ERK1/2 inhibitor and the level of ERK1/2 phosphorylation was increased by treatment with Vd3.

SIGNIFICANCE

This has been the first report on CM from Vd3 pre-activated preadipocyte displaying stimulatory effects on hair growth via the enhancement of angiogenesis in a hairless-induced C57BL/6 mice.

A novel compound T7 (N-{4'-[(1E)-N-hydroxyethanimidoyl]-3',5,6-trimethoxybiphenyl-3-yl}-N'-[4-(3-morpholin-4-ylpropoxy)phenyl]urea) screened by tissue angiogenesis model and its activity evaluation on anti-angiogenesis

A tissue model for angiogenesis that imitated new blood vessels formation in vivo had been established in the previous study. Here, it was used to screen and evaluate a series of synthesized compounds and the results indicated that compound T7 (N-{4'-[(1E)-N-hydroxyethanimidoyl]-3',5,6-trimethoxybiphenyl-3-yl}-N'-[4-(3-morpholin-4-ylpropoxy)phenyl]urea) could effectively inhibit the blood vessels formation. Then the anti-angiogenic potential of T7 and its related molecular mechanisms against lung carcinoma in vitro and in vivo were investigated. Treatment with T7 significantly inhibited human umbilical vein endothelial cells and A549 cells proliferation and migration. T7 reduced human umbilical vein endothelial cells tube formation as well. Western blotting analysis of cell signaling molecules indicated that T7 reduced phosphorylation of KDR and its downstream signaling players AKT and ERK1/2 activation in endothelial cells and A549 cells. Moreover, T7 inhibited tumor growth in A549 xenografted model of athymic mice and reduced CD34 expression levels in tumor-bearing mice by immunohistochemistry. In sum, our findings showed that T7 was a candidate of tumor angiogenesis inhibitors, and it functioned by interrupting the autophosphorylation of KDR, AKT and ERK1/2.

Eupolyphaga sinensis Walker demonstrates angiogenic activity and inhibits A549 cell growth by targeting the KDR signaling pathway

Eupolyphaga sinensis Walker has been reported to have anticoagulation, antithrombotic, liver protective and antitumor effects. In the present study, the inhibitory effects on proliferation of A549 human non‑small cell lung cancer cells and the underlying mechanisms were examined. Firstly, three solvents, 70% ethanol, distilled water and 95% ethanol, were used to extract Eupolyphaga sinensis Walker. The MTT assay results demonstrated that the 70% ethanol extract more potently reduced the growth of A549 cells and it was therefore adopted in the subsequent experiments. Eupolyphaga sinensis Walker 70% ethanol extract significantly inhibited A549 cell migration in a time‑ and dose‑dependent manner and inhibited human umbilical vein endothelial cell proliferation, migration and tube formation. Furthermore, Eupolyphaga sinensis Walker 70% ethanol extract effectively inhibited blood vessel formation in the established tissue model for angiogenesis. In addition, Eupolyphaga sinensis Walker 70% ethanol extract was demonstrated to inhibit the autophosphorylation of KDR, and downregulate the subsequent activation of AKT and extracellular signal regulated kinase (ERK)1/2 in A549 cells. In conclusion, these findings demonstrated that the antitumor mechanism of Eupolyphaga sinensis Walker 70% ethanol extract was through inhibiting angiogenesis. It functioned by interrupting the autophosphorylation of KDR and subsequently, AKT and ERK1/2.

Eupolyphaga sinensis walker displays inhibition on hepatocellular carcinoma through regulating cell growth and metastasis signaling

Tumor growth and metastasis are responsible for most cancer patients' deaths. Here, we report that eupolyphaga sinensis walker has an essential role in resisting hepatocellular carcinoma growth and metastasis. Compared with proliferation, colony formation, transwell assay and transplantable tumor in nude mouse in vitro and vivo, eupolyphaga sinensis walker extract (ESWE) showed good inhibition on the SMMC-7721 cell growth and metastasis. Using genome-wide microarray analysis, we found the down-regulated growth and metastasis factors, and selected down-regulated genes were confirmed by real-time PCR. Knockdown of a checkpoint PKCβ by siRNA significantly attenuated tumor inhibition and metastasis effects of ESWE. Moreover, our results indicate ESWE inhibits HCC growth by not only downregulating the signaling of PKCβ, Akt, m-TOR, Erk1/2, MEK-2, Raf and JNK-1, but also increasing cyclin D1 protein levels and decreasing amount of cyclin E, cyclin B1 and cdc2 of the cycle proteins. At the same time, ESWE reduced MMP2, MMP9 and CXCR4, PLG, NFκB and P53 activities. Overall, our studies demonstrate that ESWE is a key factor in growth and metastasis signaling inhibitor targeting the PKC, AKT, MAPK signaling and related metastasis signaling, having potential in cancer therapy.

Capillary Network-Like Organization of Endothelial Cells in PEGDA Scaffolds Encoded with Angiogenic Signals via Triple Helical Hybridization

Survival of tissue engineered constructs after implantation depends on proper vascularization. The differentiation of endothelial cells into mature microvasculature requires dynamic interactions between cells, scaffold, and growth factors, which are difficult to recapitulate in artificial systems. Previously, photocrosslinked poly(ethylene glycol) diacrylate (PEGDA) hydrogels displaying collagen mimetic peptides (CMPs), dubbed PEGDA‐CMP, that can be further conjugated with bioactive molecules via CMP‐CMP triple helix hybridization were reported. Here, it is shown that a bifunctional peptide featuring pro‐angiogenic domain mimicking vascular endothelial growth factor (VEGF) and a collagen mimetic domain that can fold into a triple helix conformation can hybridize with CMP side chains of the PEGDA‐CMP hydrogel, which results in presentation of insoluble VEGF‐like signals to endothelial cells. Presentation of VEGF‐like signals on the surface of micropatterned scaffolds in this way transforms cells from a quiescent state to elongated and aligned phenotype suggesting that this system could be used to engineer organized microvasculature. It is also shown that the pro‐angiogenic peptide, when applied topically in combination with modified dextran/PEGDA hydrogels, can enhance neovascularization of burn wounds in mice demonstrating the potential clinical use of CMP‐mediated matrix‐bound bioactive molecules for dermal injuries.

Hypoxia sustains glioblastoma radioresistance through ERKs/DNA-PKcs/HIF-1α functional interplay

The molecular mechanisms by which glioblastoma multiforme (GBM) refracts and becomes resistant to radiotherapy treatment remains largely unknown. This radioresistance is partly due to the presence of hypoxic regions, which are frequently found in GBM tumors. We investigated the radiosensitizing effects of MEK/ERK inhibition on GBM cell lines under hypoxic conditions. Four human GBM cell lines, T98G, U87MG, U138MG and U251MG were treated with the MEK/ERK inhibitor U0126, the HIF-1α inhibitor FM19G11 or γ-irradiation either alone or in combination under hypoxic conditions. Immunoblot analysis of specific proteins was performed in order to define their anti‑oncogenic or radiosensitizing roles in the different experimental conditions. MEK/ERK inhibition by U0126 reverted the transformed phenotype and significantly enhanced the radiosensitivity of T98G, U87MG, U138MG cells but not of the U251MG cell line under hypoxic conditions. U0126 and ERK silencing by siRNA reduced the levels of DNA protein kinase catalytic subunit (DNA-PKcs), Ku70 and K80 proteins and clearly reduced HIF-1α activity and protein expression. Furthermore, DNA-PKcs siRNA-mediated silencing counteracted HIF-1α activity and downregulated protein expression suggesting that ERKs, DNA-PKcs and HIF-1α cooperate in radioprotection of GBM cells. Of note, HIF-1α inhibition under hypoxic conditions drastically radiosensitized all cell lines used. MEK/ERK signal transduction pathway, through the sustained expression of DNA-PKcs, positively regulates HIF-1α protein expression and activity, preserving GBM radioresistance in hypoxic condition.

Brucine suppresses colon cancer cells growth via mediating KDR signalling pathway

Angiogenesis plays an important role in colon cancer development. This study aimed to demonstrate the effect of brucine on tumour angiogenesis and its mechanism of action. The anti-angiogenic effect was evaluated on the chicken chorioallantoic membrane (CAM) model and tube formation. The mechanism was demonstrated through detecting mRNA and protein expressions of VEGFR2 (KDR), PKCα, PLCγ and Raf1 by reverse transcription-polymerase chain reaction (RT-PCR) and Western blot (WB), as well as expressions of VEGF and PKCβ and mTOR by ELISA and WB. The results showed that brucine significantly reduced angiogenesis of CAM and tube formation, inhibited the VEGF secretion and mTOR expression in LoVo cell and down-regulated the mRNA and phosphorylation protein expressions of KDR, PKCα, PLCγ and Raf1. In addition, the effects of brucine on KDR kinase activity, viability of LoVo cell and gene knockdown cell were detected with the Lance™ assay, WST-1 assay and instantaneous siRNA. Compared to that of normal LoVo cells, the inhibition on proliferation of knockdown cells by brucine decreased significantly. These results suggest that brucine could inhibit angiogenesis and be a useful therapeutic candidate for colon cancer intervention.

Plant proteolytic enzyme papain abrogates angiogenic activation of human umbilical vein endothelial cells (HUVEC) in vitro

BACKGROUND

Vascular endothelial growth factor (VEGF) is a key regulator of physiologic and pathogenic angiogenesis in diseases such as cancer and diabetic retinopathy. It is known that cysteine proteases from plants, like bromelain and papain are capable to suppress inflammatory activation. Recent studies have demonstrated that they may interfere with angiogenesis related pathways as well. The aim of this study was to investigate the anti-angiogenic effects of papain on human umbilical vein endothelial cells (HUVEC) in vitro.

METHODS

Cell viability after prolonged treatment with papain was investigated by life cell staining and lactate dehydrogenase release assay. Angiogenic activation was assessed by ELISA against phosphorylated proteins AKT, MEK1/2, ERK1/2, SAPK/JNK and p38-MAPK. Growth inhibition was determined by means of an MTT-assay and cell migration by means of a scratch assay. Capability to form a capillary network was investigated using a tube formation assay.

RESULTS

Papain did not induce proteolysis or cell detachment of HUVEC in a concentration range between 0 and 25 μg/mL. Four hours treatment with 10 μg/mL papain resulted in a reduced susceptibility of endothelial cells to activation by VEGF as determined by phosphorylation levels of Akt, MEK1/2, SAPK/JNK. Papain exerted a distinct inhibitory effect on cell growth, cell migration and tube formation with inhibition of tube formation detectable at concentrations as low as 1 μg/mL. Bromelain and ficin displayed similar effects with regard to cell growth and tube formation.

CONCLUSION

Papain showed a strong anti-angiogenic effect in VEGF activated HUVEC. This effect may be due to interference with AKT, MEK1/2 and SAPK/JNK phosphorylation. Two other plant derived cysteine proteases displayed similar inhibition of HUVEC cell growth and tube formation. These findings indicate that plant proteolytic enzymes may have potential as preventive and therapeutic agents against angiogenesis related human diseases.

Hypoxia-inducible factor signaling in pheochromocytoma: turning the rudder in the right direction

Many solid tumors, including pheochromocytoma (PHEO) and paraganglioma (PGL), are characterized by a (pseudo)hypoxic signature. (Pseudo)hypoxia has been shown to promote both tumor progression and resistance to therapy. The major mediators of the transcriptional hypoxic response are hypoxia-inducible factors (HIFs). High levels of HIFs lead to transcription of hypoxia-responsive genes, which are involved in tumorigenesis. PHEOs and PGLs are catecholamine-producing tumors arising from sympathetic- or parasympathetic-derived chromaffin tissue. In recent years, substantial progress has been made in understanding the metabolic disturbances present in PHEO and PGL, especially because of the identification of some disease-susceptibility genes. To date, fifteen PHEO and PGL susceptibility genes have been identified. Based on the main transcription signatures of the mutated genes, PHEOs and PGLs have been divided into two clusters, pseudohypoxic cluster 1 and cluster 2, rich in kinase receptor signaling and protein translation pathways. Although these two clusters seem to show distinct signaling pathways, recent data suggest that both clusters are interconnected by HIF signaling as the important driver in their tumorigenesis, and mutations in most PHEO and PGL susceptibility genes seem to affect HIF-α regulation and its downstream signaling pathways. HIF signaling appears to play an important role in the development and growth of PHEOs and PGLs, which could suggest new therapeutic approaches for the treatment of these tumors.

Hypoxia-inducible factor-1 (HIF-1): a potential target for intervention in ocular neovascular diseases

Constant oxygen supply is essential for proper tissue development, homeostasis and function of all eukaryotic organisms. Cellular response to reduced oxygen levels is mediated by the transcriptional regulator hypoxia-inducible factor-1 (HIF-1). It is a heterodimeric complex protein consisting of an oxygen dependent subunit (HIF-1α) and a constitutively expressed nuclear subunit (HIF-1β). In normoxic conditions, de novo synthesized cytoplasmic HIF-1α is degraded by 26S proteasome. Under hypoxic conditions, HIF-1α is stabilized, binds with HIF-1β and activates transcription of various target genes. These genes play a key role in regulating angiogenesis, cell survival, proliferation, chemotherapy, radiation resistance, invasion, metastasis, genetic instability, immortalization, immune evasion, metabolism and stem cell maintenance. This review highlights the importance of hypoxia signaling in development and progression of various vision threatening pathologies such as diabetic retinopathy, retinopathy of prematurity, age-related macular degeneration and glaucoma. Further, various inhibitors of HIF-1 pathway that may have a viable potential in the treatment of oxygen-dependent ocular diseases are also discussed.

Norcantharidin inhibits tumor angiogenesis via blocking VEGFR2/MEK/ERK signaling pathways

Norcantharidin (NCTD), the demethylated form of Cantharidin, a reagent isolated from blister beetles, has been shown to be an anti-tumor agent capable of inhibiting proliferation as well as inducing apoptosis in many cancer cell lines. However, little is known about the effect of NCTD in tumor angiogenesis. In this study, we demonstrated that NCTD inhibited vascular endothelial growth factor (VEGF)-induced cell proliferation, migration, invasion, and capillary tube formation of primary human umbilical vein endothelial cells (HUVECs) in a dose-dependent manner. Furthermore, we showed NCTD inhibited tumor growth and angiogenesis of colon cancer cells (LOVO) in vivo. We then mechanistically described that NCTD specifically abrogated the phosphorylation/activation of vascular endothelial growth factor receptor-2 (VEGFR2)/MEK/ERK pathway kinases, with little effect on the phosphorylation of p38 MAPK and Akt, and on Cox-2 expression. In summary, our results indicate that NCTD is a potential inhibitor of tumor angiogenesis by blocking VEGFR2/MEK/ERK signaling.

Angiotensin-(1-7) reduces proliferation and angiogenesis of human prostate cancer xenografts with a decrease in angiogenic factors and an increase in sFlt-1

BACKGROUND

Prostate cancer is the most frequently diagnosed malignancy and the second-leading cause of cancer death in men. The purpose of this study was to determine the anti-proliferative and anti-angiogenic efficacy of angiotensin-(1-7) [Ang-(1-7)], an endogenous peptide hormone, in human prostate cancer xenografts.

METHODS

Human LNCaP prostate cancer cells were injected into the flank of athymic mice and tumors were treated with Ang-(1-7) for 54 days. Tumor growth and angiogenesis were determined by immunohistochemistry and western blot hybridization.

RESULTS

Ang-(1-7) markedly reduced the volume and wet weight of LNCaP xenograft tumors. Histological analysis of tumor sections from saline-treated mice showed increased Ki67 immunoreactivity and enhanced phosphorylation of the MAP kinases ERK1/2 compared to tumors from Ang-(1-7)-treated mice, suggesting that the heptapeptide reduces cell proliferation. Intratumoral vessel density was decreased in Ang-(1-7)-treated mice with an associated reduction in vascular endothelial growth factor (VEGF) and placental growth factor (PlGF), suggesting that the heptapeptide attenuates vascularization by reducing angiogenic factors. Ang-(1-7) administration markedly increased the soluble fraction of VEGF receptor 1 (sFlt-1), with a concomitant reduction in VEGF receptors 1 and 2. sFlt-1 serves as a decoy receptor that traps VEGF and PlGF, making the ligands unavailable to membrane-bound VEGF receptors and preventing activation of pro-angiogenic signaling.

CONCLUSIONS

The decrease in PlGF and VEGF coupled with the increase in sFlt-1 suggests that Ang-(1-7) may serve as a novel anti-angiogenic therapy for prostate cancer. Further, the pleiotropic mechanisms of action by Ang-(1-7) may limit angiogenic resistance that occurs with VEGF inhibitors or receptor blockers.

Anti-angiogenic activity of Herba Epimedii on zebrafish embryos in vivo and HUVECs in vitro

Herba Epimedii, an herb commonly used in East Asian medicine, is commonly used for treatment of impotence, osteoporosis and many inflammatory conditions in traditional Chinese medicine. Recent studies revealed that Herba Epimedii also has anti-tumor or anti-cancer activities, which may possibly be mediated through anti-angiogenesis. This study aims to examine and confirm the anti-angiogenic activity in the herb using both in vivo and in vitro approaches. The 95% ethanol extract and four subsequent fractions (n-hexane, ethyl acetate (EA), n-butanol and aqueous fractions) of Herba Epimedii were tested on the zebrafish model by the quantitative assay for endogenous alkaline phosphatase; then, the active fraction was further tested on Tg(fli1a:EGFP)y1 zebrafish embryos and human umbilical vein endothelial cells (HUVECs) for the anti-angiogenic effects. In addition, the action mechanism of Herba Epimedii was further investigated on wild-type zebrafish embryos and HUVECs. The EA fraction showed anti-angiogenic effects in both in vivo and in vitro models. Further experiments demonstrated that it might affect angiogenesis by acting on multiple molecular targets in zebrafish embryos and ERK signaling pathway in HUVECs. In conclusion, Herba Epimedii can inhibit angiogenesis, which may be the mechanism for its anti-inflammatory, anti-tumor and anti-cancer actions.

A novel angiogenesis inhibitor impairs lovo cell survival via targeting against human VEGFR and its signaling pathway of phosphorylation

Colorectal cancer represents the fourth commonest malignancy, and constitutes a major cause of significant morbidity and mortality among other diseases. However, the chemical therapy is still under development. Angiogenesis plays an important role in colon cancer development. We developed HMQ18–22 (a novel analog of taspine) with the aim to target angiogenesis. We found that HMQ18–22 significantly reduced angiogenesis of chicken chorioallantoic membrane (CAM) and mouse colon tissue, and inhibited cell migration and tube formation as well. Then, we verified the interaction between HMQ18–22 and VEGFR2 by AlphaScreen P-VEGFR assay, screened the targets on angiogenesis by VEGF Phospho Antibody Array, validated the target by western blot and RNAi in lovo cells. We found HMQ18–22 could decrease phosphorylation of VEGFR2(Tyr¹²¹⁴), VEGFR1(Tyr¹³³³), Akt(Tyr³²⁶), protein kinase Cα (PKCα) (Tyr⁶⁵⁷) and phospholipase-Cγ-1 (PLCγ-1) (Tyr⁷⁷¹). Most importantly, HMQ18–22 inhibited proliferation of lovo cell and tumor growth in a human colon tumor xenografted model of athymic mice. Compared with normal lovo cells proliferation, the inhibition on proliferation of knockdown cells (VEGFR2, VEGFR1, Akt, PKCα and PLCγ-1) by HMQ18–22 decreased. These results suggested that HMQ18–22 is a novel angiogenesis inhibitor and can be a useful therapeutic candidate for colon cancer intervention.

The role of CX₃CL1/CX₃CR1 in pulmonary angiogenesis and intravascular monocyte accumulation in rat experimental hepatopulmonary syndrome

BACKGROUND & AIMS

Hepatopulmonary syndrome (HPS), classically attributed to intrapulmonary vascular dilatation, occurs in 15-30% of cirrhotics and causes hypoxemia and increases mortality. In experimental HPS after common bile duct ligation (CBDL), monocytes adhere in the lung vasculature and produce vascular endothelial growth factor (VEGF)-A and angiogenesis ensues and contribute to abnormal gas exchange. However, the mechanisms for these events are unknown. The chemokine fractalkine (CX(3)CL1) can directly mediate monocyte adhesion and activate VEGF-A and angiogenesis via its receptor CX(3)CR1 on monocytes and endothelium during inflammatory angiogenesis. We explored whether pulmonary CX(3)CL1/CX(3)CR1 alterations occur after CBDL and influence pulmonary angiogenesis and HPS.

METHODS

Pulmonary CX(3)CL1/CX(3)CR1 expression and localization, CX(3)CL1 signaling pathway activation, monocyte accumulation, and development of angiogenesis and HPS were assessed in 2- and 4-week CBDL animals. The effects of a neutralizing antibody to CX(3)CR1 (anti-CX(3)CR1 Ab) on HPS after CBDL were evaluated.

RESULTS

Circulating CX(3)CL1 levels and lung expression of CX(3)CL1 and CX(3)CR1 in intravascular monocytes and microvascular endothelium increased in 2- and 4-week CBDL animals as HPS developed. These events were accompanied by pulmonary angiogenesis, monocyte accumulation, activation of CX(3)CL1 mediated signaling pathways (Akt, ERK) and increased VEGF-A expression and signaling. Anti-CX(3)CR1 Ab treatment reduced monocyte accumulation, decreased lung angiogenesis and improved HPS. These events were accompanied by inhibition of CX(3)CL1 signaling pathways and a reduction in VEGF-A expression and signaling.

CONCLUSIONS

Circulating CX(3)CL1 levels and pulmonary CX(3)CL1/CX(3)CR1 expression and signaling increase after CBDL and contribute to pulmonary intravascular monocyte accumulation, angiogenesis and development of experimental HPS.

Indirubin derivative E804 inhibits angiogenesis

Background

It has previously been shown that indirubin derivative E804 (IDR-E804) blocks signal transducer and activator of transcription-3 signaling in human breast and prostate cancer cells and inhibits Src kinase activity. To further establish its role in angiogenesis, we tested its potential using human umbilical vein endothelial cells (HUVECs) and analyzed the effects of IDR-E804 on cellular and molecular events related to angiogenesis.

Methods

The anti-angiogenic effects of IDR-E804 were examined by assessing the proliferation, migration and capillary tube formation of HUVECs were induced by vascular endothelial growth factor (VEGF) with or without various concentrations of IDR-E804. The inhibitory effect of IDR-E804 angiogenesis and tumor growth in vivo was also investigated in Balb/c mice subcutaneously transplanted with CT-26 colon cancer cells.

Results

IDR-E804 significantly decreased proliferation, migration and tube formation of vascular endothelial growth factor VEGF-treated HUVECs. These effects were accompanied by decreased phosphorylation of VEGF receptor (VEGFR)-2, AKT and extracellular signal regulated kinase in VEGF-treated HUVECs. Intratumor injections of IDR-E804 inhibited the growth of subcutaneously inoculated CT-26 allografts in syngenic mice. Immunohistochemistry revealed a decreased CD31 microvessel density index and Ki-67 proliferative index, but an increased apoptosis index in IDR-E804-treated tumors.

Conclusions

These data revealed that IDR-E804 is an inhibitor of angiogenesis and also provide evidence for the efficacy of IDR-E804 for anti-tumor therapies.

Neuroprotective effect of ligustilide against ischaemia-reperfusion injury via up-regulation of erythropoietin and down-regulation of RTP801

BACKGROUND AND PURPOSE

Ligustilide, the main lipophilic component of Danggui, has been reported to protect the brain against ischaemic injury. However, the mechanisms are unknown. Here, we investigated the roles of erythropoietin (EPO) and the stress-induced protein RTP801 in neuroprotection provided by ligustilide against ischaemia-reperfusion (I/R) damage to the brain.

EXPERIMENTAL APPROACH

The efficacy of ligustilide against I/R damage was assessed by neurological deficit, infarct volume and cell viability, using the middle cerebral artery occlusion model in rats in vivo and rat cultured neurons in vitro. EPO and RTP801 were analysed by Western blot. Over-expression of RTP801 was achieved by transfection of an expression plasmid.

KEY RESULTS

Ligustilide decreased the neurological deficit score, infarct volume and RTP801 expression and increased EPO transcription in I/R rats, and increased cell viability and EPO and decreased LDH release and RTP801 in I/R neurons. Also, ligustilide increased ERK phosphorylation (p-ERK). The positive effects of ligustilide on p-ERK, cell viability and EPO were blocked by PD98059, but not LY294002 and SB203580. In addition, transfection of SH-SY5Y cells with RTP801 plasmid increased RTP801 and LDH release, while ligustilide inhibited the effects of transfection on RTP801 expression and also increased cell viability.

CONCLUSION AND IMPLICATIONS

Ligustilide exerts neuroprotective effects against I/R injury by promoting EPO transcription via an ERK signalling pathway and inhibiting RTP801 expression, This compound could be developed into a therapeutic agent to prevent and treat ischaemic disorders.