Erk1 and Erk2 regulate endothelial cell proliferation and migration during mouse embryonic angiogenesis

Tie-2 Cre-Mediated Deficiency of Extracellular Signal-Regulated Kinase 2 Potentiates Experimental Bronchopulmonary Dysplasia-Associated Pulmonary Hypertension in Neonatal Mice

Bronchopulmonary dysplasia (BPD)-associated pulmonary hypertension (PH) is a significant lung morbidity of infants, and disrupted lung angiogenesis is a hallmark of this disease. We observed that extracellular signal-regulated kinases (ERK) 1/2 support angiogenesis in vitro, and hyperoxia activates ERK1/2 in fetal human pulmonary microvascular endothelial cells (HPMECs) and in neonatal murine lungs; however, their role in experimental BPD and PH is unknown. Therefore, we hypothesized that Tie2 Cre-mediated deficiency of ERK2 in the endothelial cells of neonatal murine lungs would potentiate hyperoxia-induced BPD and PH. We initially determined the role of ERK2 in in vitro angiogenesis using fetal HPMECs. To disrupt endothelial ERK2 signaling in the lungs, we decreased ERK2 expression by breeding ERK2^flox/flox mice with Tie-Cre mice. One-day-old endothelial ERK2-sufficient (eERK2^+/+) or –deficient (eERK2^+/−) mice were exposed to normoxia or hyperoxia (FiO₂ 70%) for 14 d. We then performed lung morphometry, gene and protein expression studies, and echocardiography to determine the extent of inflammation, oxidative stress, and development of lungs and PH. The knockdown of ERK2 in HPMECs decreased in vitro angiogenesis. Hyperoxia increased lung inflammation and oxidative stress, decreased lung angiogenesis and alveolarization, and induced PH in neonatal mice; however, these effects were augmented in the presence of Tie2-Cre mediated endothelial ERK2 deficiency. Therefore, we conclude that endothelial ERK2 signaling is necessary to mitigate hyperoxia-induced experimental BPD and PH in neonatal mice. Our results indicate that endothelial ERK2 is a potential therapeutic target for the management of BPD and PH in infants.

Human peroxidasin 1 promotes angiogenesis through ERK1/2, Akt, and FAK pathways

Aims

The term angiogenesis refers to sprouting of new blood vessels from pre-existing ones. The angiogenic process involves cell migration and tubulogenesis requiring interaction between endothelial cells and the extracellular matrix. Human peroxidasin 1 (hsPxd01) is a multidomain heme peroxidase found embedded in the basement membranes. As it promotes the stabilization of extracellular matrix, we investigated its possible role in angiogenesis both in vitro and in vivo.

Methods and results

We analysed the effects of peroxidasin 1 gene silencing and supplementation by recombinant hsPxd01 in TeloHAEC endothelial cells on cell migration, tubulogenesis in matrigel, and intracellular signal transduction as assessed by kinase phosphorylation and expression of pro-angiogenic genes as measured by qRT-PCR. We further evaluated the angiogenic potential of recombinant peroxidasin in a chicken chorioallantoic membrane model. RNA silencing of endogenous hsPxd01 significantly reduced tube formation and cell migration, whereas supplementation by the recombinant peroxidase promoted tube formation in vitro and stimulated vascularization in vivo through its catalytic activity. Moreover, recombinant hsPxd01 promoted phosphorylation of Extracellular signal-Regulated Kinases (ERK1/2), Protein kinase B (Akt), and Focal Adhesion Kinase (FAK), and induced the expression of pro-angiogenic downstream genes: Platelet Derived Growth Factor Subunit B (PDGFB), endothelial-derived Heparin Binding EGF-like growth factor (HB-EGF), CXCL-1, Hairy-Related Transcription Factor 1 (HEY-1), DNA-binding protein inhibitor (ID-2), Snail Family Zinc Finger 1 (SNAI-1), as well as endogenous hsPxd01. However, peroxidasin silencing significantly reduced Akt and FAK phosphorylation but induced ERK1/2 activation after supplementation by recombinant hsPxd01. While hsPxd01 silencing significantly reduced expression of HEY-1, ID-2, and PDGFB, it did not affect expression of SNAI-1, HB-EGF, and CXCL-1 after supplementation by recombinant hsPxd01.

Conclusion

Our findings suggest a role of enzymatically active peroxidasin 1 as a pro-angiogenic peroxidase and a modulator of ERK1/2, Akt and FAK signalling.

Isoform-Specific Roles of ERK1 and ERK2 in Arteriogenesis

Despite the clinical importance of arteriogenesis, this biological process is poorly understood. ERK1 and ERK2 are key components of a major intracellular signaling pathway activated by vascular endothelial growth (VEGF) and FGF2, growth factors critical to arteriogenesis. To investigate the specific role of each ERK isoform in arteriogenesis, we used mice with a global Erk1 knockout as well as Erk1 and Erk2 floxed mice to delete Erk1 or Erk2 in endothelial cells, macrophages, and smooth muscle cells. We found that ERK1 controls macrophage infiltration following an ischemic event. Loss of ERK1 in endothelial cells and macrophages induced an excessive macrophage infiltration leading to an increased but poorly functional arteriogenesis. Loss of ERK2 in endothelial cells leads to a decreased arteriogenesis due to decreased endothelial cell proliferation and a reduced eNOS expression. These findings show for the first time that isoform-specific roles of ERK1 and ERK2 in the control of arteriogenesis.

Intravitreal AAV2.COMP-Ang1 Attenuates Deep Capillary Plexus Expansion in the Aged Diabetic Mouse Retina

Purpose

We determine whether intravitreal angiopoietin-1 combined with the short coiled-coil domain of cartilage oligomeric matrix protein by adeno-associated viral serotype 2 (AAV2.COMP-Ang1) delivery following the onset of vascular damage could rescue or repair damaged vascular beds and attenuate neuronal atrophy and dysfunction in the retinas of aged diabetic mice.

Methods

AAV2.COMP-Ang1 was bilaterally injected into the vitreous of 6-month-old male Ins2Akita mice. Age-matched controls consisted of uninjected C57BL/6J and Ins2Akita males, and of Ins2Akita males injected with PBS or AAV2.REPORTER (AcGFP or LacZ). Retinal thickness and visual acuity were measured in vivo at baseline and at the 10.5-month endpoint. Ex vivo vascular parameters were measured from retinal flat mounts, and Western blot was used to detect protein expression.

Results

All three Ins2Akita control groups showed significantly increased deep vascular density at 10.5 months compared to uninjected C57BL/6J retinas (as measured by vessel area, length, lacunarity, and number of junctions). In contrast, deep microvascular density of Ins2Akita retinas treated with AAV2.COMP-Ang1 was more similar to uninjected C57BL/6J retinas for all parameters. However, no significant improvement in retinal thinning or diabetic retinopathy-associated visual loss was found in treated diabetic retinas.

Conclusions

Deep retinal microvasculature of diabetic Ins2Akita eyes shows late stage changes consistent with disorganized vascular proliferation. We show that intravitreally injected AAV2.COMP-Ang1 blocks this increase in deep microvascularity, even when administered subsequent to development of the first detectable vascular defects. However, improving vascular normalization did not attenuate neuroretinal degeneration or loss of visual acuity. Therefore, additional interventions are required to address neurodegenerative changes that are already underway.

First insights for targeted therapies in odontogenic myxoma

OBJECTIVE

Odontogenic myxoma (OM) occasionally responds poorly to surgical treatment. The MAPK pathway is constitutively activated in several neoplasms and we aimed to test if the MAPK pathway is activated in OM, in order to pave the way for an alternative therapy for aggressive and recurrent cases.

MATERIALS AND METHODS

The immunoexpression of phosphorylated ERK1/2 (pERK1/2) was assessed in OM. We established a 3D organotypic culture model for the in vitro study and patient-derived xenografts (PDX) in mice for the in vivo study. The MEK inhibitor U0126 was used to inhibit phosphorylation of ERK1/2 in the in vitro and in vivo models.

RESULTS

All OM showed strong pERK1/2 immunoexpression, consistent with MAPK pathway activation. Treatment of the 3D culture with U0126 resulted in a reduced pERK1/2/ERK1/2 ratio. Consistent with the in vitro results, all PDX of animals treated with U0126 showed a decreased volume fold change compared with controls.

CONCLUSIONS

The MAPK pathway is activated in OM and its inhibition leads to tumor shrinkage in PDX and cell culture models.

CLINICAL RELEVANCE

Our results offer a pre-clinical frame for OM-targeted therapy. Further work is needed to determine if this initial finding holds clinical promise.

AGS-30, an andrographolide derivative, suppresses tumor angiogenesis and growth in vitro and in vivo

Poor bioavailability and limited efficacy are challenges associated with using andrographolide as a therapeutic agent. We recently synthesized AGS-30, a new andrographolide derivative, in our laboratory. In this study we investigated the potential anti-tumor effect of AGS-30 and the underlying mechanisms, particularly those related to angiogenesis. Results from our in vitro experiments showed that AGS-30 exerted anti-angiogenic effects by inhibiting endothelial cell proliferation, migration, invasion, and tube formation. Phosphorylation and activation of angiogenesis-related signaling molecules (e.g., vascular endothelial growth factor [VEGF] receptor 2, mitogen-activated protein kinase kinase 1/2, extracellular signal-regulated kinase 1/2, mechanistic target of rapamycin [mTOR], protein kinase B [Akt], and p38) were markedly reduced by AGS-30. Meanwhile, AGS-30 potently inhibited cell proliferation and phosphorylation of cell survival-related proteins (e.g., Akt, mTOR, and ERK1/2) and decreased the expression of VEGF in HT-29 colon cancer cells. AGS-30 blocked microvessel sprouting in a rat aortic ring model and blood vessel formation in zebrafish embryos and a mouse Matrigel plug model. Additionally, AGS-30 suppressed tumor growth and angiogenesis in HT-29 colon cancer cell xenografts in nude mice. These effects were not observed when same concentration of andrographolide, the parent compound of AGS-30, was used. Thus, AGS-30 exerted a strong antitumor effect by inhibiting tumor cell growth and angiogenesis and is a candidate compound for the treatment of cancer.

3-O-Acetyloleanolic acid inhibits angiopoietin-1-induced angiogenesis and lymphangiogenesis via suppression of angiopoietin-1/Tie-2 signaling

Tumor angiogenesis and lymphangiogenesis are important processes in tumor progression and metastasis. The inhibitory effects of 3-O-acetyloleanolic acid (3AOA), a pentacyclic triterpenoid compound isolated from Vigna sinensis K., on tumor-induced angiogenesis and lymphangiogenesis in vitro and in vivo were studied. Angiopoietin-1 is an important angiogenic and lymphangiogenic factor secreted from colon carcinoma CT-26 cells under hypoxia conditions. 3AOA inhibited proliferation, migration, and tube formation of angiopoietin-1-treated human umbilical vein endothelial cells (HUVEC) and human lymphatic microvascular endothelial cells (HLMEC). 3AOA reduced angiogenesis and lymphangiogenesis in angiopoietin-1-stimulated Matrigel plugs. Also, 3AOA inhibited tumor growth and tumor-induced angiogenesis and lymphangiogenesis in an angiopoietin-1-induced CT-26 allograft colon carcinoma animal model. 3AOA inhibited activation of the angiopoietin-1 receptor Tie-2 and activation of the downstream signaling factors FAK, AKT, and ERK1/2 that are involved in the angiopoietin-1/Tie-2-signaling pathway. Thus, 3AOA has an inhibitory effect on angiogenesis and lymphangiogenesis induced by angiopoietin-1 both in vitro and in vivo, and the inhibitory effect of 3AOA is probably due to suppression of angiopoietin-1/Tie-2 signaling in HUVEC and HLMEC.

Dual specificity phosphatase 5 regulates perfusion recovery in experimental peripheral artery disease

Peripheral artery disease (PAD) is caused by atherosclerotic occlusions of vessels outside the heart, particularly those of the lower extremities. Angiogenesis is one critical physiological response to vessel occlusion in PAD, but our understanding of the molecular mechanisms involved in angiogenesis is incomplete. Dual specificity phosphatase 5 (DUSP5) has been shown to play a key role in embryonic vascular development, but its role in post-ischemic angiogenesis is not known. We induced hind limb ischemia in mice and found robust upregulation of Dusp5 expression in ischemic hind limbs. Moreover, in vivo knockdown of Dusp5 resulted in impaired perfusion recovery in ischemic limbs and was associated with increased limb necrosis. In vitro studies showed upregulation of DUSP5 in human endothelial cells exposed to ischemia, and knockdown of DUSP5 in these ischemic endothelial cells resulted in impaired endothelial cell proliferation and angiogenesis, but did not alter apoptosis. Finally, we show that these effects of DUSP5 on post-ischemic angiogenesis are a result of DUSP5-dependent decrease in ERK1/2 phosphorylation and p21 protein expression. Thus, we have identified a role of DUSP5 in post-ischemic angiogenesis and implicated a DUSP5-ERK-p21 pathway that may serve as a therapeutic target for the modulation of post-ischemic angiogenesis in PAD.

Narciclasine inhibits angiogenic processes by activation of Rho kinase and by downregulation of the VEGF receptor 2

The process of angiogenesis is involved in several pathological conditions, such as tumor growth or age-related macular degeneration. Although the available anti-angiogenic drugs have improved the therapy of these diseases, major drawbacks, such as unwanted side effects and resistances, still exist. Consequently, the search for new anti-angiogenic substances is still ongoing. Narciclasine, a plant alkaloid from different members of the Amaryllidaceae family, has extensively been characterized as anti-tumor compound. Beyond the field of cancer, the compound has recently been shown to possess anti-inflammatory properties. Surprisingly, potential actions of narciclasine on endothelial cells in the context of angiogenesis have been neglected so far. Thus, we aimed to analyze the effects of narciclasine on angiogenic processes in vitro and in vivo and to elucidate the underlying mechanism. Narciclasine (100-300 nM) effectively inhibited the proliferation, undirected and directed migration, network formation and angiogenic sprouting of human primary endothelial cells. Moreover, narciclasine (1 mg/kg/day) strongly reduced the VEGF-triggered angiogenesis in vivo (Matrigel plug assay in mice). Narciclasine mediated its anti-angiogenic effects in part by a RhoA-independent activation of the Rho kinase ROCK. Most importantly, however, the compound reduced the de novo protein synthesis in endothelial cells by approx. 50% without exhibiting considerable cytotoxic effects. As a consequence, narciclasine diminished the presence of proteins with a short half-life, such as the VEGF receptor 2, which is the basis for its anti-angiogenic effects. Taken together, our study highlights narciclasine as an interesting anti-angiogenic compound that is worth to be further evaluated in preclinical studies.

Competing Fluid Forces Control Endothelial Sprouting in a 3-D Microfluidic Vessel Bifurcation Model

Sprouting angiogenesis-the infiltration and extension of endothelial cells from pre-existing blood vessels-helps orchestrate vascular growth and remodeling. It is now agreed that fluid forces, such as laminar shear stress due to unidirectional flow in straight vessel segments, are important regulators of angiogenesis. However, regulation of angiogenesis by the different flow dynamics that arise due to vessel branching, such as impinging flow stagnation at the base of a bifurcating vessel, are not well understood. Here we used a recently developed 3-D microfluidic model to investigate the role of the flow conditions that occur due to vessel bifurcations on endothelial sprouting. We observed that bifurcating fluid flow located at the vessel bifurcation point suppresses the formation of angiogenic sprouts. Similarly, laminar shear stress at a magnitude of ~3 dyn/cm² applied in the branched vessels downstream of the bifurcation point, inhibited the formation of angiogenic sprouts. In contrast, co-application of ~1 µm/s average transvascular flow across the endothelial monolayer with laminar shear stress induced the formation of angiogenic sprouts. These results suggest that transvascular flow imparts a competing effect against bifurcating fluid flow and laminar shear stress in regulating endothelial sprouting. To our knowledge, these findings are the first report on the stabilizing role of bifurcating fluid flow on endothelial sprouting. These results also demonstrate the importance of local flow dynamics due to branched vessel geometry in determining the location of sprouting angiogenesis.

Endothelial ERK1/2 signaling maintains integrity of the quiescent endothelium

The endothelial ERK1/2 pathway plays a crucial role in the maintenance of endothelial homeostasis. Its suppression results in activation of TGFβ signaling, leading to hypertension, renal failure, fibrosis, and sudden death, findings similar to those observed in patients treated with anti-VEGF agents.

To define the role of ERK1/2 signaling in the quiescent endothelium, we induced endothelial Erk2 knockout in adult Erk1^−/− mice. This resulted in a rapid onset of hypertension, a decrease in eNOS expression, and an increase in endothelin-1 plasma levels, with all mice dying within 5 wk. Immunostaining and endothelial fate mapping showed a robust increase in TGFβ signaling leading to widespread endothelial-to-mesenchymal transition (EndMT). Fibrosis affecting the cardiac conduction system was responsible for the universal lethality in these mice. Other findings included renal endotheliosis, loss of fenestrated endothelia in endocrine organs, and hemorrhages. An ensemble computational intelligence strategy, comprising deep learning and probabilistic programing of RNA-seq data, causally linked the loss of ERK1/2 in HUVECs in vitro to activation of TGFβ signaling, EndMT, suppression of eNOS, and induction of endothelin-1 expression. All in silico predictions were verified in vitro and in vivo. In summary, these data establish the key role played by ERK1/2 signaling in the maintenance of vascular normalcy.

High mitogenic stimulation arrests angiogenesis

Appropriate therapeutic modulation of endothelial proliferation and sprouting is essential for the effective inhibition of angiogenesis in cancer or its induction in cardiovascular disease. The current view is that an increase in growth factor concentration, and the resulting mitogenic activity, increases both endothelial proliferation and sprouting. Here, we modulate mitogenic stimuli in different vascular contexts by interfering with the function of the VEGF and Notch signalling pathways at high spatiotemporal resolution in vivo. Contrary to the prevailing view, our results indicate that high mitogenic stimulation induced by VEGF, or Notch inhibition, arrests the proliferation of angiogenic vessels. This is due to the existence of a bell-shaped dose-response to VEGF and MAPK activity that is counteracted by Notch and p21, determining whether endothelial cells sprout, proliferate, or become quiescent. The identified mechanism should be considered to achieve optimal therapeutic modulation of angiogenesis.

High mitogenic stimuli have been suggested to promote endothelial cell proliferation and sprouting during angiogenesis. Here Pontes-Quero et al., by interfering with levels of VEGF and Notch signalling in single endothelial cells in vivo, find that high mitogenic stimuli instead arrest angiogenesis due to a bell-shaped dose-response to VEGF and MAPK activity that is counteracted by Notch and p21.

C3a Receptor Inhibition Protects Brain Endothelial Cells Against Oxygen-glucose Deprivation/Reperfusion

The complement cascade is a central component of innate immunity which plays a critical role in brain inflammation. Complement C3a receptor (C3aR) is a key mediator of post-ischemic cerebral injury, and pharmacological antagonism of the C3a receptor is neuroprotective in stroke. Cerebral ischemia injures brain endothelial cells, causing blood brain barrier (BBB) disruption which further exacerbates ischemic neuronal injury. In this study, we used an in vitro model of ischemia (oxygen glucose deprivation; OGD) to investigate the protective effect of a C3aR antagonist (C3aRA, SB290157) on brain endothelial cells (bEnd.3). Following 24 hours of reperfusion, OGD-induced cell death was assessed by TUNEL and Caspase-3 staining. Western blot and immunocytochemistry were utilized to demonstrate that OGD upregulates inflammatory, oxidative stress and antioxidant markers (ICAM-1, Cox-2, Nox-2 and MnSOD) in endothelial cells and that C3aRA treatment significantly attenuate these markers. We also found that C3aRA administration restored the expression level of the tight junction protein occludin in endothelial cells following OGD. Interestingly, OGD/reperfusion injury increased the phosphorylation of ERK1/2 and C3aR inhibition significantly reduced the activation of ERK suggesting that endothelial C3aR may act via ERK signaling. Furthermore, exogenous C3a administration stimulates these same inflammatory mechanisms both with and without OGD, and C3aRA suppresses these C3a-mediated responses, supporting an antagonist role for C3aRA. Based on these results, we conclude that C3aRA administration attenuates inflammation, oxidative stress, ERK activation, and protects brain endothelial cells following experimental brain ischemia.

Sema4D/PlexinB1 promotes endothelial differentiation of dental pulp stem cells via activation of AKT and ERK1/2 signaling

Inducing of dental pulp stem cells (DPSCs) into endothelial cells (ECs) to prevascularize pulp tissue constructs may offer a novel and viable approach for enhancing pulp regeneration. However, there are numerous challenges in current methods for the acquisition of sufficient translational ECs. It was known that Sema4D/PlexinB1 signaling exerts profound effects on enhancing vascular endothelial growth factor (VEGF) secretion and angiogenesis. Whether Sema4D/PlexinB1 could regulate endothelial differentiation of DPSCs is not yet investigated. In this study, when DPSCs were treated with Sema4D (2 μg/mL), ECs-specific (VEGFR1, VEGFR2, CD31, and vWF), and angiogenic genes and proteins were significantly upregulated. The induced ECs exhibited similar endothelial vessel formation ability to that of human umbilical vein endothelial cells (HUVECs). Furthermore, phosphorylation of AKT increased dramatically within 5 minutes (from 0.93 to 21.8), while p-ERK1/2 was moderately elevated (from 0.94 to 2.65). In summary, our results demonstrated that Sema4D/PlexinB1 signaling induces endothelial differentiation of DPSCs. The interactions of Sema4D, VEGF, ANGPTL4, ANG1, and HIF-1α may play a crucial role in mediating the differentiation process.

Recombinant RGD-disintegrin DisBa-01 blocks integrin αvβ3 and impairs VEGF signaling in endothelial cells

Background

Integrins mediate cell adhesion, migration, and survival by connecting the intracellular machinery with the surrounding extracellular matrix. Previous studies demonstrated the interaction between α_vβ₃ integrin and VEGF type 2 receptor (VEGFR2) in VEGF-induced angiogenesis. DisBa-01, a recombinant His-tag fusion, RGD-disintegrin from Bothrops alternatus snake venom, binds to α_vβ₃ integrin with nanomolar affinity blocking cell adhesion to the extracellular matrix. Here we present in vitro evidence of a direct interference of DisBa-01 with α_vβ₃/VEGFR2 cross-talk and its downstream pathways.

Methods

Human umbilical vein (HUVECs) were cultured in plates coated with fibronectin (FN) or vitronectin (VN) and tested for migration, invasion and proliferation assays in the presence of VEGF, DisBa-01 (1000 nM) or VEGF and DisBa-01 simultaneously. Phosphorylation of α_vβ₃/VEGFR2 receptors and the activation of intracellular signaling pathways were analyzed by western blotting. Morphological alterations were observed and quantified by fluorescence confocal microscopy.

Results

DisBa-01 treatment of endothelial cells inhibited critical steps of VEGF-mediated angiogenesis such as migration, invasion and tubulogenesis. The blockage of α_vβ₃/VEGFR2 cross-talk by this disintegrin decreases protein expression and phosphorylation of VEGFR2 and β₃ integrin subunit, regulates FAK/SrC/Paxillin downstream signals, and inhibits ERK1/2 and PI3K pathways. These events result in actin re-organization and inhibition of HUVEC migration and adhesion. Labelled-DisBa-01 colocalizes with α_vβ₃ integrin and VEGFR2 in treated cells.

Conclusions

Disintegrin inhibition of α_vβ₃ integrin blocks VEGFR2 signalling, even in the presence of VEGF, which impairs the angiogenic mechanism. These results improve our understanding concerning the mechanisms of pharmacological inhibition of angiogenesis.

Electronic supplementary material

The online version of this article (10.1186/s12964-019-0339-1) contains supplementary material, which is available to authorized users.

Apoliporotein L3 interferes with endothelial tube formation via regulation of ERK1/2, FAK and Akt signaling pathway

BACKGROUND AND AIMS

Endothelial cells are main actors in vascular homeostasis as they regulate vascular pressure and permeability as well as hemostasis and inflammation. Disturbed stimuli delivered to and by endothelial cells correlate with the so-called endothelial dysfunction and disrupt this homeostasis. As constituents of the inner layer of blood vessels, endothelial cells are also involved in angiogenesis. Apolipoprotein Ls (APOL) comprise a family of newly discovered apolipoproteins with yet poorly understood function, and are suggested to be involved in inflammatory processes and cell death mechanisms. Here we investigate the role of APOLs in endothelial cells stimulated with factors known to be involved in atherogenesis and their possible contribution to endothelial dysfunction with an emphasis on inflammation driven-angiogenesis in vitro.

METHODS

Using the CRISPR/Cas9 technique, we analyzed the effect of APOL3 gene knock out in HMEC-1 endothelial cells on cell migration, tubulogenesis, endothelial permeability, intracellular signal transduction as assessed by kinase phosphorylation, and angiogenesis gene expression (measured by qRT-PCR).

RESULTS

Our results indicate that among the family, APOL3 was the only member induced by myeloperoxidase, oxidized LDL, VEGF and FGF treatments. APOL3 invalidation increased endothelial permeability, reduced wound repair and tubule formation in vitro, the latter only in MPO and VEGF-induced conditions. Accordingly, some pro-angiogenic signaling pathways (ERK1/2 and FAK but not Akt) and some pro-angiogenic genes were partially inhibited in APOL3 knock out cells.

CONCLUSIONS

These findings suggest the involvement of APOL3 in angiogenesis in vitro and as a modulator of MAPK and FAK signaling in endothelial cells.

Suppression of angiogenesis and tumor growth by recombinant T4 phages displaying extracellular domain of vascular endothelial growth factor receptor 2

Tumor growth, invasion and metastasis are dependent on angiogenesis. The Vascular endothelial growth factor (VEGF)/VEGF receptor 2 (VEGFR2) signaling pathway plays a pivotal role in tumor angiogenesis and therefore represents a reasonable target for anti-angiogenesis/anti-tumor therapy. In the present study, we generated T4 recombinant phages expressing the extracellular domain of VEGFR2 (T4-VEGFR2) and investigated their anti-angiogenic activity. The T4-VEGFR2 phages were able to bind to VEGF specifically and inhibit VEGF-mediated phosphorylation of VEGFR2 and its downstream kinases such as extracellular signal-regulated kinase (ERK) and p38 mitogen activated protein kinase (MAPK). The in vitro experiments showed that the T4-VEGFR2 phages could inhibit VEGF-stimulated cell proliferation and migration of endothelial cells. Finally, administration of T4-VEGFR2 phages was able to suppress tumor growth and decrease microvascular density in murine models of Lewis lung carcinoma and colon carcinoma, and prolong the survival of tumor bearing mice. In conclusion, this study reveals that the recombinant T4-VEGFR2 phages generated using T4-based phage display system can inhibit VEGF-mediated tumor angiogenesis and the T4 phage display technology can therefore be used for the development of novel anti-cancer strategies.

The "Yin and Yang" of Natural Compounds in Anticancer Therapy of Triple-Negative Breast Cancers

Among the different types of breast cancers, triple-negative breast cancers (TNBCs) are highly aggressive, do not respond to conventional hormonal/human epidermal growth factor receptor 2 (HER2)-targeted interventions due to the lack of the respective receptor targets, have chances of early recurrence, metastasize, tend to be more invasive in nature, and develop drug resistance. The global burden of TNBCs is increasing regardless of the number of cytotoxic drugs being introduced into the market each year as they have only moderate efficacy and/or unforeseen side effects. Therefore, the demand for more efficient therapeutic interventions, with reduced side effects, for the treatment of TNBCs is rising. While some plant metabolites/derivatives actually induce the risk of cancers, many plant-derived active principles have gained attention as efficient anticancer agents against TNBCs, with fewer adverse side effects. Here we discuss the possible oncogenic molecular pathways in TNBCs and how the purified plant-derived natural compounds specifically target and modulate the genes and/or proteins involved in these aberrant pathways to exhibit their anticancer potential. We have linked the anticancer potential of plant-derived natural compounds (luteolin, chalcones, piperine, deguelin, quercetin, rutin, fisetin, curcumin, resveratrol, and others) to their ability to target multiple dysregulated signaling pathways (such as the Wnt/β-catenin, Notch, NF-κB, PI3K/Akt/mammalian target of rapamycin (mTOR), mitogen-activated protein kinase (MAPK) and Hedgehog) leading to suppression of cell growth, proliferation, migration, inflammation, angiogenesis, epithelial-mesenchymal transition (EMT) and metastasis, and activation of apoptosis in TNBCs. Plant-derived compounds in combination with classical chemotherapeutic agents were more efficient in the treatment of TNBCs, possibly with lesser side effects.

Synthesis of novel 1,2-bis-quinolinyl-1,4-naphthoquinones: ERK2 inhibition, cytotoxicity and molecular docking studies

Two novel series of N-2,3-bis(6-substituted-4-hydroxy-2-oxo-1,2-dihydroquinolin-3-yl)naphthalene-1,4-diones 3a-d and substituted N-(methyl/ethyl)bisquinolinone triethyl-ammonium salts 4e,f were successfully synthesized. The synthesized compounds were targeted as new candidates to extracellular signal-regulated kinases 1/2 (ERK1/2) with considerable antineoplastic activity. The synthesis involved the reactions of 2 equivalents of 4-hydroxy-2(1H)-quinolinones 1a-f and one equivalent of 1,4-naphthoquinone (2) in a mixture of ethanol/dimethylformamide (1:1) as a solvent and 0.5 mL Et₃N. In the reaction of 6-methyl-4-hydroxyquinolone 1b with 2, a side product 4b of the second series was obtained. In general, the presence of free NH-quinolone gave a single compound of the first series, whereas reaction of N-methyl/ethyl-quinolones 1e,f with 2 enhanced the formation of compounds of the second series. The structures of the new compounds were proved by different spectroscopic techniques such as IR, NMR (2D-NMR) and mass spectra, elemental analysis, and X-ray crystallography. To further elucidate the mechanism of action of these newly synthesized compounds, compounds 3a, 3b, 4e and 4f were selected to investigate for their MAP Kinases pathway inhibition together with molecular docking using ATP-binding site of ERK2. The results revealed that compounds 3a, 3b and 4f inhibited ETS-1 phosphorylation by ERK2 in a dose dependent manner. Also, compound 4f showed highest potency for ERK2 inhibition with ATP-competitive inhibition mechanism which was confirmed by the formation of three hydrogen bond in the molecular docking studies. The synthesized compounds were then tested for their in vitro anticancer activity against the NCI-60 panel of tumor cell lines. Interestingly, the selected compounds displayed from modest to strong cytotoxic activities. Compound 3b demonstrated broad spectrum anti-tumor activity against the nine tumor sub-panels tested, while compound 3d proved to be lethal to most of the cancer cell lines as shown by their promising GI₅₀ and TGI values in NCI in vitro five dose testing. These results revealed that the synthesized compounds can potentially serve as leads for the development of novel chemotherapeutic agents and structure improvement will be necessary for some derivatives for enhancing their cellular activities and pharmacokinetic profile.

Myeloperoxidase promotes tube formation, triggers ERK1/2 and Akt pathways and is expressed endogenously in endothelial cells

Myeloperoxidase is a member of the mammalian peroxidase family, mainly expressed in the myeloblastic cell lineage. It is considered a major bactericidal agent as it is released in the phagosome where it catalyzes the formation of reactive oxygen species. It is also released in the extracellular spaces including blood where it is absorbed on (lipo)proteins and endothelial cell surface, interfering with endothelial function. We performed RNA sequencing on MPO-treated endothelial cells, analyzed their transcriptome and validated the profile of gene expression by individual qRT-PCR. Some of the induced genes could be grouped in several functional networks, including tubulogenesis, angiogenesis, and blood vessel morphogenesis and development as well as signal transduction pathways associated to these mechanisms. MPO treatment mimicked the effects of VEGF on several signal transduction pathways, such as Akt, ERK or FAK involved in angiogenesis. Accordingly MPO, independently of its enzymatic activity, stimulated tube formation by endothelial cells. RNA interference also pointed at a role of endogenous MPO in tubulogenesis and endothelium wound repair in vitro. These data suggest that MPO, whether from endogenous or exogenous sources, could play a role in angiogenesis and vascular repair in vivo.

Hyperoxia Disrupts Extracellular Signal-Regulated Kinases 1/2-Induced Angiogenesis in the Developing Lungs

Hyperoxia contributes to the pathogenesis of bronchopulmonary dysplasia (BPD), a chronic lung disease of infants that is characterized by interrupted alveologenesis. Disrupted angiogenesis inhibits alveologenesis, but the mechanisms of disrupted angiogenesis in the developing lungs are poorly understood. In pre-clinical BPD models, hyperoxia increases the expression of extracellular signal-regulated kinases (ERK) 1/2; however, its effects on the lung endothelial ERK1/2 signaling are unclear. Further, whether ERK1/2 activation promotes lung angiogenesis in infants is unknown. Hence, we tested the following hypotheses: (1) hyperoxia exposure will increase lung endothelial ERK1/2 signaling in neonatal C57BL/6J (WT) mice and in fetal human pulmonary artery endothelial cells (HPAECs); (2) ERK1/2 inhibition will disrupt angiogenesis in vitro by repressing cell cycle progression. In mice, hyperoxia exposure transiently increased lung endothelial ERK1/2 activation at one week of life, before inhibiting it at two weeks of life. Interestingly, hyperoxia-mediated decrease in ERK1/2 activation in mice was associated with decreased angiogenesis and increased endothelial cell apoptosis. Hyperoxia also transiently activated ERK1/2 in HPAECs. ERK1/2 inhibition disrupted angiogenesis in vitro, and these effects were associated with altered levels of proteins that modulate cell cycle progression. Collectively, these findings support our hypotheses, emphasizing that the ERK1/2 pathway is a potential therapeutic target for BPD infants with decreased lung vascularization.

The cellular chloride channels CLIC1 and CLIC4 contribute to virus-mediated cell motility

Ion channels regulate many aspects of cell physiology, including cell proliferation, motility, and migration, and aberrant expression and activity of ion channels is associated with various stages of tumor development, with K⁺ and Cl⁻ channels now being considered the most active during tumorigenesis. Accordingly, emerging in vitro and preclinical studies have revealed that pharmacological manipulation of ion channel activity offers protection against several cancers. Merkel cell polyomavirus (MCPyV) is a major cause of Merkel cell carcinoma (MCC), primarily because of the expression of two early regulatory proteins termed small and large tumor antigens (ST and LT, respectively). Several molecular mechanisms have been attributed to MCPyV-mediated cancer formation but, thus far, no studies have investigated any potential link to cellular ion channels. Here we demonstrate that Cl⁻ channel modulation can reduce MCPyV ST-induced cell motility and invasiveness. Proteomic analysis revealed that MCPyV ST up-regulates two Cl⁻ channels, CLIC1 and CLIC4, which when silenced, inhibit MCPyV ST-induced motility and invasiveness, implicating their function as critical to MCPyV-induced metastatic processes. Consistent with these data, we confirmed that CLIC1 and CLIC4 are up-regulated in primary MCPyV-positive MCC patient samples. We therefore, for the first time, implicate cellular ion channels as a key host cell factor contributing to virus-mediated cellular transformation. Given the intense interest in ion channel modulating drugs for human disease. This highlights CLIC1 and CLIC4 activity as potential targets for MCPyV-induced MCC.

VEGFR2 is activated by high-density lipoproteins and plays a key role in the proangiogenic action of HDL in ischemia

High-density lipoproteins augment hypoxia-induced angiogenesis by inducing the key angiogenic vascular endothelial growth factor A (VEGFA) and total protein levels of its receptor 2 (VEGFR2). The activation/phosphorylation of VEGFR2 is critical for mediating downstream, angiogenic signaling events. This study aimed to determine whether reconstituted high-density lipoprotein (rHDL) activates VEGFR2 phosphorylation and the downstream signaling events and the importance of VEGFR2 in the proangiogenic effects of rHDL in hypoxia. In vitro, rHDL increased VEGFR2 activation and enhanced phosphorylation of downstream, angiogenic signaling proteins ERK1/2 and p38 MAPK in hypoxia. Incubation with a VEGFR2-neutralizing antibody attenuated rHDL-induced phosphorylation of VEGFR2, ERK1/2, p38 MAPK, and tubule formation. In a murine model of ischemia-driven neovascularization, rHDL infusions enhanced blood perfusion and augmented capillary and arteriolar density. Infusion of a VEGFR2-neutralizing antibody ablated those proangiogenic effects of rHDL. Circulating Sca1⁺/CXCR4⁺ angiogenic progenitor cell levels, important for neovascularization in response to ischemia, were higher in rHDL-infused mice 3 d after ischemic induction, but that did not occur in mice that also received the VEGFR2-neutralizing antibody. In summary, VEGFR2 has a key role in the proangiogenic effects of rHDL in hypoxia/ischemia. These findings have therapeutic implications for angiogenic diseases associated with an impaired response to tissue ischemia.-Cannizzo, C. M., Adonopulos, A. A., Solly, E. L., Ridiandries, A., Vanags, L. Z., Mulangala, J., Yuen, S. C. G., Tsatralis, T., Henriquez, R., Robertson, S., Nicholls, S. J., Di Bartolo, B. A., Ng, M. K. C., Lam, Y. T., Bursill, C. A., Tan, J. T. M. VEGFR2 is activated by high-density lipoproteins and plays a key role in the proangiogenic action of HDL in ischemia.

Secretogranin III promotes angiogenesis through MEK/ERK signaling pathway

Secretogranin III (Scg3) was recently discovered as the first highly diabetic retinopathy-associated angiogenic factor, and its neutralizing antibody alleviated the disease with high efficacy in diabetic mice. Investigation of its molecular mechanisms will facilitate the translation of this novel therapy. Scg3 was reported to induce the phosphorylation of mitogen-activated protein kinase kinase (MEK)/extracellular signal-regulated kinase (ERK). Here we characterized the importance of MEK/ERK activation to Scg3 angiogenic activity. Our results showed that MEK inhibitor PD98059 blocked Scg3-induced proliferation of human umbilical vein endothelial cells (HUVECs). This finding was corroborated by PD98059 inhibition of HUVEC migration and tube formation. Furthermore, ERK inhibitor SCH772984 also suppressed Scg3-induced proliferation and migration of HUVECs. Taken together, these findings suggest that MEK-ERK pathway plays an important role in Scg3-induced angiogenesis.

Deciphering the link between PI3K and PAK: An opportunity to target key pathways in pancreatic cancer?

The development of personalised therapies has ushered in a new and exciting era of cancer treatment for a variety of solid malignancies. Yet pancreatic ductal adenocarcinoma (PDAC) has failed to benefit from this paradigm shift, remaining notoriously refractory to targeted therapies. Chemotherapy is the cornerstone of management but can offer only modest survival benefits of a few months with 5-year survival rates rarely exceeding 3%. Despite these disappointing statistics, significant strides have been made towards understanding the complex biology of pancreatic cancer, with deep genomic sequencing identifying novel genetic aberrations and key signalling pathways. The PI3K-PDK1-AKT pathway has received great attention due to its prominence in carcinogenesis. However, efforts to target several components of this network have resulted in only a handful of drugs demonstrating any survival benefit in solid tumors; despite promising pre-clinical results. p-21 activated kinase 4 (PAK4) is a gene that is recurrently amplified or overexpressed in PDAC and both PAK4 and related family member PAK1, have been linked to aberrant RAS activity, a common feature in pancreatic cancer. As regulators of PI3K, PAKs have been highlighted as a potential prognostic marker and therapeutic target. In this review, we discuss the biology of pancreatic cancer and the close interaction between PAKs and the PI3K pathway. We also suggest proposals for future research that may see the development of effective targeted therapies that could finally improve outcomes for this disease.

CLEC14a-HSP70-1A interaction regulates HSP70-1A-induced angiogenesis

CLEC14a (C-type lectin domain family 14 member) is a tumor endothelial cell marker protein that is known to play an important role in tumor angiogenesis, but the basic molecular mechanisms underlying this function have not yet been clearly elucidated. In this study, using various proteomic tools, we isolated a 70-kDa protein that interacts with the C-type lectin-like domain of CLEC14a (CLEC14a-CTLD) and identified it as heat shock protein 70-1A (HSP70-1A). Co-immunoprecipitation showed that HSP70-1A and CLEC14a interact on endothelial cells. In vitro binding analyses identified that HSP70-1A specifically associates with the region between amino acids 43 and 69 of CLEC14a-CTLD. Competitive blocking experiments indicated that this interacting region of CLEC14a-CTLD significantly inhibits HSP70-1A-induced extracellular signal-regulated kinase (ERK) phosphorylation and endothelial tube formation by directly inhibiting CLEC14a-CTLD-mediated endothelial cell-cell contacts. Our data suggest that the specific interaction of HSP70-1A with CLEC14a may play a critical role in HSP70-1A-induced angiogenesis and that the HSP70-1A-interacting region of CLEC14a-CTLD may be a useful tool for inhibiting HSP70-1A-induced angiogenesis.

miR-132 promotes retinal neovascularization under anoxia and reoxygenation conditions through up-regulating Egr1, ERK2, MMP2, VEGFA and VEGFC expression

Retinal neovascularization (RNV) is a prominent pathological angiogenesis, which causes detrimental outcomes in visual functions. Previous literature represents that miR-132 induces angiogenesis in tumor development and ischemic diseases. Considering the important role in angiogenesis, we hypothesized that miR-132 might be involved in RNV. In this study, human retinal microvascular endothelial cells were maintained in hypoxia for indicated time, followed by further incubation in normoxic conditions to establish hypoxia/reoxygenation (H/R) models in vitro. mRNA microarray analysis was undertaken to detect alterations in gene profiles in the cells. qRT-PCR and Western blotting were performed to evaluate expression of genes that are closely associated to neovascularization. Results showed that miR-132 expression was increased under hypoxic conditions. Reoxygenation for a limited time (6 h) failed to restore miR-132 expression to basal level. Interference of miR-132 expression via its inhibitor suppressed the cell proliferation under H/R conditions, increasing the apoptosis rate. mRNA microarray analysis revealed that miR-132 is involved in the regulation of vasculature development, blood vessel morphogenesis, and proliferation and migration of microvascular endothelial cells through regulating genes such as early growth response gene 1 (Egr1), extracellular signal-regulated kinase (ERK), metal matrix proteinase (MMP2), vascular endothelial growth factor (VEGF)-A and VEGF-C. qRT-PCR and Western blotting further demonstrated that miR-132 up-regulated their gene and protein expression under H/R conditions. In summary, miR-132 was involved in the development of RNV under H/R conditions, at least partly, through up-regulating Egr1, ERK2, MMP2, VEGFA and VEGFC expression. This finding facilitates the understanding of pathogenic mechanisms of RNV.

Engineered microenvironments for synergistic VEGF - Integrin signalling during vascularization

We have engineered polymer-based microenvironments that promote vasculogenesis both in vitro and in vivo through synergistic integrin-growth factor receptor signalling. Poly(ethyl acrylate) (PEA) triggers spontaneous organization of fibronectin (FN) into nanonetworks which provide availability of critical binding domains. Importantly, the growth factor binding (FNIII_12-14) and integrin binding (FNIII_9-10) regions are simultaneously available on FN fibrils assembled on PEA. This material platform promotes synergistic integrin/VEGF signalling which is highly effective for vascularization events in vitro with low concentrations of VEGF. VEGF specifically binds to FN fibrils on PEA compared to control polymers (poly(methyl acrylate), PMA) where FN remains in a globular conformation and integrin/GF binding domains are not simultaneously available. The vasculogenic response of human endothelial cells seeded on these synergistic interfaces (VEGF bound to FN assembled on PEA) was significantly improved compared to soluble administration of VEGF at higher doses. Early onset of VEGF signalling (PLCγ1 phosphorylation) and both integrin and VEGF signalling (ERK1/2 phosphorylation) were increased only when VEGF was bound to FN nanonetworks on PEA, while soluble VEGF did not influence early signalling. Experiments with mutant FN molecules with impaired integrin binding site (FN-RGE) confirmed the role of the integrin binding site of FN on the vasculogenic response via combined integrin/VEGF signalling. In vivo experiments using 3D scaffolds coated with FN and VEGF implanted in the murine fat pad demonstrated pro-vascularization signalling by enhanced formation of new tissue inside scaffold pores. PEA-driven organization of FN promotes efficient presentation of VEGF to promote vascularization in regenerative medicine applications.

Deciphering the RAS/ERK pathway in vivo

The RAS/ERK pathway has been intensely studied for about three decades, not least because of its role in human pathologies. ERK activation is observed in the majority of human cancers; in about one-third of them, it is driven by mutational activation of pathway components. The pathway is arguably one of the best targets for molecule-based pharmacological intervention, and several small-molecule inhibitors are in clinical use. Genetically engineered mouse models have greatly contributed to our understanding of signaling pathways in development, tissue homeostasis, and disease. In the specific case of the RAS/ERK pathway, they have revealed unique biological roles of structurally and functionally similar proteins, new kinase-independent effectors, and unsuspected relationships with other cascades. This short review summarizes the contribution of mouse models to our current understanding of the pathway.

MET/ERK2 pathway regulates the motility of human alveolar rhabdomyosarcoma cells

In alveolar rhabdomyosarcoma (ARMS) that is a highly malignant pediatric soft tissue tumor, MET, a receptor of hepatocyte growth factor (HGF), was reported to be downstream of the PAX3-FOXO1 fusion gene specific to ARMS, and a key mediator of metastatic behavior in RMS. So far, no studies have investigated the downstream signaling pathways of MET in ARMS, even though HGF and MET have been suggested to be deeply involved in the invasiveness of ARMS. In this study, we demonstrated the functions of MET signaling in ARMS in vitro by using three human ARMS cell lines and three human embryonal rhabdomyosarcoma (ERMS) cell lines. MET mRNA levels and MET protein expression in ARMS cell lines was higher than those in ERMS cell lines as detected by real-time quantitative PCR and western blotting, respectively. Based on cell growth and cell cycle analyses it was found that HGF stimulation did not enhance the proliferation of ERMS or ARMS cell lines. HGF-stimulated cell motility of ARMS cell lines was inhibited by U0126 (ERK1/2 inhibitor) but was only partially inhibited by PD98059 (ERK1 inhibitor) or rapamycin (mTOR inhibitor) as observed in wound-healing and migration assays. Western blotting revealed that ERK1/2 was dephosphorylated by U0126 to a higher extent than by PD98059 in the ARMS cells. HGF-stimulated cell motility of Rh30 cell line was inhibited not by ERK1 siRNA, but by ERK2 siRNA. Our data thus suggest that HGF/MET signaling promotes motility of ARMS cells mainly through ERK2 signaling. A specific inhibitor of ERK2 phosphorylation could therefore be a specific anticancer agent against invasiveness and metastasis in ARMS.

Vegfa signals through ERK to promote angiogenesis, but not artery differentiation

Vascular endothelial growth factor a (Vegfa) is essential for blood vessel formation and can induce activation of numerous signaling effectors in endothelial cells. However, it is unclear how and where these function in developmental contexts during vascular morphogenesis. To address this issue, we have visualized activation of presumptive Vegfa effectors at single-cell resolution in zebrafish blood vessels. From these studies, we find that phosphorylation of the serine/threonine kinase ERK (pERK) preferentially occurs in endothelial cells undergoing angiogenesis, but not in committed arterial endothelial cells. pERK in endothelial cells was ectopically induced by Vegfa and lost in Vegfa signaling mutants. Both chemical and endothelial autonomous inhibition of ERK prevented endothelial sprouting, but did not prevent initial artery differentiation. Timed chemical inhibition during angiogenesis caused a loss of genes implicated in coordinating tip/stalk cell behaviors, including flt4 and, at later stages, dll4 ERK inhibition also blocked excessive angiogenesis and ectopic flt4 expression in Notch-deficient blood vessels. Together, these studies implicate ERK as a specific effector of Vegfa signaling in the induction of angiogenic genes during sprouting.

Identification of RSK and TTK as Modulators of Blood Vessel Morphogenesis Using an Embryonic Stem Cell-Based Vascular Differentiation Assay

Blood vessels are formed through vasculogenesis, followed by remodeling of the endothelial network through angiogenesis. Many events that occur during embryonic vascular development are recapitulated during adult neoangiogenesis, which is critical to tumor growth and metastasis. Current antiangiogenic tumor therapies, based largely on targeting the vascular endothelial growth factor pathway, show limited clinical benefits, thus necessitating the discovery of alternative targets. Here we report the development of a robust embryonic stem cell-based vascular differentiation assay amenable to small-molecule screens to identify novel modulators of angiogenesis. In this context, RSK and TTK were identified as angiogenic modulators. Inhibition of these pathways inhibited angiogenesis in embryoid bodies and human umbilical vein endothelial cells. Furthermore, inhibition of RSK and TTK reduced tumor growth, vascular density, and improved survival in an in vivo Lewis lung carcinoma mouse model. Our study suggests that RSK and TTK are potential targets for antiangiogenic therapy, and provides an assay system for further pathway screens.

•

Development of ESC-based vascular differentiation assay amenable to drug screening

•

Screening a kinase library identified RSK and TTK as angiogenic modulators

•

RSK and TTK inhibition disrupted angiogenesis in vitro

•

RSK and TTK inhibition inhibited Lewis lung tumor growth and angiogenesis in vivo

New Natural Pigment Fraction Isolated from Saw Palmetto: Potential for Adjuvant Therapy of Hepatocellular Carcinoma

For the first time, we discovered a small proportion of aqueous fraction from Saw Palmetto apart from the fatty acid-rich fraction exhibited pharmacological activity. Therefore, this study aims to explore the anti-tumor potential of red pigmented aqueous fraction of Saw Palmetto, NYG on human hepatocellular carcinoma and its possible targets. Subcutaneous xenograft and orthotopic implantation models of HCC were used to evaluate the tumor inhibitory effect of NYG. Human hepatocellular carcinoma (HCC) cell lines and human umbilical vein endothelial cells (HUVEC) were used as in vitro model. The mRNA expression was conducted by qPCR. Protein expression was monitored by immunoblotting and immunohistochemistry. Cell migration and blood vessel formation were determined by chamber assay and tube formation assay, respectively. Significant tumor inhibition of NYG in dose-dependent manner was observed on subcutaneous xenograft and orthotopic HCC model. NYG has no direct action on cell viability or VEGF secretion of HCC cells. However, NYG reduced in vitro migration and vessel formation activities of HUVEC cells, as well as in vivo intratumoral neovascularization. NYG attenuated extracellular signal-regulated kinases (ERK) activation in endothelial cells, which may be associated with the suppression of migration and tube formation of HUVEC. NYG suppressed tumor expansion of HCC via inhibiting neovascularization, and may be potential adjuvant treatment for HCC.

Endothelial Mitogen-Activated Protein Kinase Kinase Kinase Kinase 4 Is Critical for Lymphatic Vascular Development and Function

The molecular mechanisms underlying lymphatic vascular development and function are not well understood. Recent studies have suggested a role for endothelial cell (EC) mitogen-activated protein kinase kinase kinase kinase 4 (Map4k4) in developmental angiogenesis and atherosclerosis. Here, we show that constitutive loss of EC Map4k4 in mice causes postnatal lethality due to chylothorax, suggesting that Map4k4 is required for normal lymphatic vascular function. Mice constitutively lacking EC Map4k4 displayed dilated lymphatic capillaries, insufficient lymphatic valves, and impaired lymphatic flow; furthermore, primary ECs derived from these animals displayed enhanced proliferation compared with controls. Yeast 2-hybrid analyses identified the Ras GTPase-activating protein Rasa1, a known regulator of lymphatic development and lymphatic endothelial cell fate, as a direct interacting partner for Map4k4. Map4k4 silencing in ECs enhanced basal Ras and extracellular signal-regulated kinase (Erk) activities, and primary ECs lacking Map4k4 displayed enhanced lymphatic EC marker expression. Taken together, these results reveal that EC Map4k4 is critical for lymphatic vascular development by regulating EC quiescence and lymphatic EC fate.

ERK1 and ERK2 Map Kinases: Specific Roles or Functional Redundancy?

The MAP kinase signaling cascade Ras/Raf/MEK/ERK has been involved in a large variety of cellular and physiological processes that are crucial for life. Many pathological situations have been associated to this pathway. More than one isoform has been described at each level of the cascade. In this review we devoted our attention to ERK1 and ERK2, which are the effector kinases of the pathway. Whether ERK1 and ERK2 specify functional differences or are in contrast functionally redundant, constitutes an ongoing debate despite the huge amount of studies performed to date. In this review we compiled data on ERK1 vs. ERK2 gene structures, protein sequences, expression levels, structural and molecular mechanisms of activation and substrate recognition. We have also attempted to perform a rigorous analysis of studies regarding the individual roles of ERK1 and ERK2 by the means of morpholinos, siRNA, and shRNA silencing as well as gene disruption or gene replacement in mice. Finally, we comment on a recent study of gene and protein evolution of ERK isoforms as a distinct approach to address the same question. Our review permits the evaluation of the relevance of published studies in the field especially when measurements of global ERK activation are taken into account. Our analysis favors the hypothesis of ERK1 and ERK2 exhibiting functional redundancy and points to the concept of the global ERK quantity, and not isoform specificity, as being the essential determinant to achieve ERK function.

Coptis japonica Makino extract suppresses angiogenesis through regulation of cell cycle-related proteins

Angiogenesis, neovascularization from pre-existing vessels, is a key step in tumor growth and metastasis, and anti-angiogenic agents that can interfere with these essential steps of cancer development are a promising strategy for human cancer treatment. In this study, we characterized the anti-angiogenic effects of Coptis japonica Makino extract (CJME) and its mechanism of action. CJME significantly inhibited the proliferation, migration, and invasion of vascular endothelial growth factor (VEGF)-stimulated HUVECs. Furthermore, CJME suppressed VEGF-induced tube formation in vitro and VEGF-induced microvessel sprouting ex vivo. According to our study, CJME blocked VEGF-induced cell cycle transition in G1. CJME decreased expression of cell cycle-regulated proteins, including Cyclin D, Cyclin E, Cdk2, and Cdk4 in response to VEGF. Taken together, the results of our study indicate that CJME suppresses VEGF-induced angiogenic events such as proliferation, migration, and tube formation via cell cycle arrest in G1.

Potential role of p21 Activated Kinase 1 (PAK1) in the invasion and motility of oral cancer cells

BACKGROUND

Oral cancer malignancy consists of uncontrolled division of cells primarily in and around the floor of the oral cavity, gingiva, oropharynx, lower lip and base of the tongue. According to GLOBOCAN 2012 report, oral cancer is one of the most common cancers among males and females in India. Even though significant advancements have been made in the field of oral cancer treatment modalities, the overall prognosis for the patients has not improved in the past few decades and hence, this demands a new thrust for the identification of novel therapeutic targets in oral cancer. p21 Activated Kinases (PAKs) are potential therapeutic targets that are involved in numerous physiological functions. PAKs are serine-threonine kinases and they serve as important regulators of cytoskeletal dynamics and cell motility, transcription through MAP kinase cascades, death and survival signalling, and cell-cycle progression. Although PAKs are known to play crucial roles in cancer progression, the role and clinical significance of PAKs in oral cancer remains poorly understood.

RESULTS

Our results suggest that PAK1 is over-expressed in oral cancer cell lines. Stimulation of Oral Squamous Cell Carcinoma (OSCC) cells with serum growth factors leads to PAK1 re-localization and might cause a profound cytoskeletal remodelling. PAK1 was also found to be involved in the invasion, migration and cytoskeletal remodelling of OSCC cells.

CONCLUSIONS

Our study revealed that PAK1 may play a crucial role in the progression of OSCC. Studying the role of PAK1 and its substrates is likely to enhance our understanding of oral carcinogenesis and potential therapeutic value of PAKs in oral cancer.

A new role for cofilin in retinal neovascularization

Pak1 plays an important role in several cellular processes, including cell migration, but its role in pathological angiogenesis is not known. Here, we have determined its role in pathological retinal angiogenesis using an oxygen-induced retinopathy (OIR) model. VEGFA induced phosphorylation of Pak1 and its effector cofilin in a manner that was dependent on time as well as p38MAPKβ (also known as MAPK11) in human retinal microvascular endothelial cells (HRMVECs). Depletion of the levels of any of these molecules inhibited VEGFA-induced HRMVEC F-actin stress fiber formation, migration, proliferation, sprouting and tube formation. In accordance with these observations, hypoxia induced Pak1 and cofilin phosphorylation with p38MAPKβ being downstream to Pak1 and upstream to cofilin in mouse retina. Furthermore, Pak1 deficiency abolished hypoxia-induced p38MAPKβ and cofilin phosphorylation and abrogated retinal endothelial cell proliferation, tip cell formation and neovascularization. In addition, small interfering RNA (siRNA)-mediated downregulation of p38MAPKβ or cofilin levels in the wild-type mouse retina also diminished endothelial cell proliferation, tip cell formation and neovascularization. Taken together, these observations suggest that, although the p38MAPKβ-Pak1-cofilin axis is required for HRMVEC migration, proliferation, sprouting and tubulogenesis, Pak1-p38MAPKβ-cofilin signaling is also essential for hypoxia-induced mouse retinal endothelial cell proliferation, tip cell formation and neovascularization.

Heat shock protein 70-1A is a novel angiogenic regulator

Heat shock protein 70-1A (HSP70-1A) is a stress-inducible protein that provides an essential intracellular molecular chaperone function; however, the mechanism of HSP70-1A in angiogenesis has not been clarified. Herein, HSP70-1A gene silencing implicated this protein in angiogenesis. Additionally, recombinant human HSP70-1A (rhHSP70-1A) was able to stimulate human umbilical vein endothelial cell (HUVEC) migration and tube formation in vitro and microvessel formation in vivo similarly to recombinant human vascular endothelial growth factor (rhVEGF). Furthermore, rhHSP70-1A was tightly bound to the surface of HUVECs and participated in extracellular signal-related kinase (ERK)-dependent angiogenesis. Together, these results implicate HSP70-1A as a novel angiogenic regulator.

p21-Activated Kinase 2 Regulates Endothelial Development and Function through the Bmk1/Erk5 Pathway

p21-activated kinases (Paks) have been shown to regulate cytoskeleton rearrangements, cell proliferation, attachment, and migration in a variety of cellular contexts, including endothelial cells. However, the role of endothelial Pak in embryo development has not been reported, and currently, there is no consensus on the endothelial function of individual Pak isoforms, in particular p21-activated kinase 2 (Pak2), the main Pak isoform expressed in endothelial cells. In this work, we employ genetic and molecular studies that show that Pak2, but not Pak1, is a critical mediator of development and maintenance of endothelial cell function. Endothelial depletion of Pak2 leads to early embryo lethality due to flawed blood vessel formation in the embryo body and yolk sac. In adult endothelial cells, Pak2 depletion leads to severe apoptosis and acute angiogenesis defects, and in adult mice, endothelial Pak2 deletion leads to increased vascular permeability. Furthermore, ubiquitous Pak2 deletion is lethal in adult mice. We show that many of these defects are mediated through a newly unveiled Pak2/Bmk1 pathway. Our results demonstrate that endothelial Pak2 is essential during embryogenesis and also for adult blood vessel maintenance, and they also pinpoint the Bmk1/Erk5 pathway as a critical mediator of endothelial Pak2 signaling.

Arf6 regulates tumour angiogenesis and growth through HGF-induced endothelial β1 integrin recycling

Anti-angiogenic drugs targeting vascular endothelial cell growth factor receptor have provided modest clinical benefit, in part, owing to the actions of additional angiogenic factors that stimulate tumour neoangiogenesis in parallel. To overcome this redundancy, approaches targeting these other signalling pathways are required. Here we show, using endothelial cell-targeted mice, that the small GTPase Arf6 is required for hepatocyte growth factor (HGF)-induced tumour neoangiogenesis and growth. Arf6 deletion from endothelial cells abolishes HGF-stimulated β1 integrin recycling. Pharmacological inhibition of the Arf6 guanine nucleotide exchange factor (GEF) Grp1 efficiently suppresses tumour vascularization and growth. Grp1 as well as other Arf6 GEFs, such as GEP100, EFA6B and EFA6D, regulates HGF-stimulated β1 integrin recycling. These findings provide insight into the mechanism of HGF-induced tumour angiogenesis and offer the possibility that targeting the HGF-activated Arf6 signalling pathway may synergize with existing anti-angiogenic drugs to improve clinical outcomes.

RhoC maintains vascular homeostasis by regulating VEGF-induced signaling in endothelial cells

Vasculogenesis and angiogenesis are controlled by vascular endothelial growth factor A (VEGF-A). Dysregulation of these physiological processes contributes to the pathologies of heart disease, cancer and stroke. Rho GTPase proteins play an integral role in VEGF-mediated formation and maintenance of blood vessels. The regulatory functions of RhoA and RhoB in vasculogenesis and angiogenesis are well defined, whereas the purpose of RhoC remains poorly understood. Here, we describe how RhoC promotes vascular homeostasis by modulating endothelial cell migration, proliferation and permeability. RhoC stimulates proliferation of human umbilical vein endothelial cells (HUVECs) by stabilizing nuclear β-catenin, which promotes transcription of cyclin D1 and subsequently drives cell cycle progression. RhoC negatively regulates endothelial cell migration through MAPKs and downstream MLC2 signaling, and decreases vascular permeability through downregulation of the phospholipase Cγ (PLCγ)-Ca(2+)-eNOS cascade in HUVECs. Using a VEGF-inducible zebrafish (Danio rerio) model, we observed significantly increased vascular permeability in RhoC morpholino (MO)-injected zebrafish compared with control MO-injected zebrafish. Taken together, our findings suggest that RhoC is a key regulator of vascular homeostasis in endothelial cells.

Tripeptidyl Peptidase II Mediates Levels of Nuclear Phosphorylated ERK1 and ERK2

Tripeptidyl peptidase II (TPP2) is a serine peptidase involved in various biological processes, including antigen processing, cell growth, DNA repair, and neuropeptide mediated signaling. The underlying mechanisms of how a peptidase can influence this multitude of processes still remain unknown. We identified rapid proteomic changes in neuroblastoma cells following selective TPP2 inhibition using the known reversible inhibitor butabindide, as well as a new, more potent, and irreversible peptide phosphonate inhibitor. Our data show that TPP2 inhibition indirectly but rapidly decreases the levels of active, di-phosphorylated extracellular signal-regulated kinase 1 (ERK1) and ERK2 in the nucleus, thereby down-regulating signal transduction downstream of growth factors and mitogenic stimuli. We conclude that TPP2 mediates many important cellular functions by controlling ERK1 and ERK2 phosphorylation. For instance, we show that TPP2 inhibition of neurons in the hippocampus leads to an excessive strengthening of synapses, indicating that TPP2 activity is crucial for normal brain function.

The effects of kisspeptin-10 on migration and proliferation of endothelial cell

BACKGROUND

Migration, expansion and survival of endothelial cells that are an important cellular component of blood vessels plays an important role in the induction of tumor growth. Kisspeptins (kp), peptides that bind to coupled-G protein receptor (GPR54), inhibit each step of metastatic cascade include invasion, migration and homing, angiogenesis, survival and proliferation. In this study we investigated effects of kisspeptin-10, the most potent member of kisspeptin family, on Migration and proliferation of endothelial cells that are necessary for angiogenesis and tumor metastasis.

MATERIALS AND METHODS

We compared migration of Human Umbilical Vein Endothelial Cells (HUVECs) were treated with 10-100 or 500 nM kp-10 for 24 hours and no treated cells using an in vitro trans membrane migration assay and HUVEC proliferation of treated endothelial cells with 10-100 or 500 nM kp-10 for 48 hours and no treated cells was measured by MTT Cell Proliferation Assay Kit. Analysis of data was performed using the Kruskal-Wallis test followed by the Mann-Whitney test.

RESULTS

Migration and proliferation of endothelial cells were increased at lower concentration of kp-10 specially at 100 nM while higher concentration reduced both migration and proliferation.

CONCLUSION

Our data showed that different concentrations of kp-10 have distinct effects on migration and proliferation of endothelial cells.