Daphnetin inhibits TNF‐α and VEGF‐induced angiogenesis through inhibition of the IKKs/IκBα/NF‐κB,Src/FAK/ERK1/2 and Akt signalling pathways

Coumarins, identified as plant secondary metabolites possess diverse biological activities including anti‐angiogenic properties. Daphnetin (DAP), a plant derived dihydroxylated derivative of coumarin has shown significant pharmacological properties such as anticancer, anti‐arthritic and anti‐inflammatory. The present study was performed to investigate the anti‐angiogenic potential of DAP, focusing on the mechanism of action. The in vivo anti‐angiogenic potential of DAP was evaluated by vascular endothelial growth factor (VEGF)‐induced rat aortic ring (RAR) assay and chick chorioallantoic membrane (CAM) assay. For in vitro evaluation, wounding migration, transwell invasion, tube formation and apoptosis assays were performed on VEGF (8 ng/mL)‐induced human umbilical vein endothelial cells (HUVECs). The cellular mechanism of DAP was examined on TNFα (10 ng/mL) and VEGF‐induced HUVECs by extracting the mRNA and protein levels using RT‐qPCR and western blotting. Our data demonstrated that DAP inhibited the in vivo angiogenesis in the RAR and CAM assay. DAP also inhibited the different steps of angiogenesis, such as migration, invasion, and tube formation in HUVECs. DAP inhibited nuclear factor‐κB signalling together including TNF‐α induced IκBα degradation; phosphorylation of IκB kinase (IKKα/β) and translocation of the NF‐κB‐p65 protein. Furthermore, western blotting revealed that DAP significantly down‐regulated the VEGF‐induced signalling such as c‐Src, FAK, ERK1/2 and the related phosphorylation of protein kinase B (Akt) and VEGFR2 expressions. DAP reduced the elevated mRNA expression of iNOS, MMP2 and also, induced apoptosis in VEGF‐stimulated HUVECs by the caspase‐3 dependent pathway. Taken together, this study reveals that DAP may have novel prospective as a new multi‐targeted medication for the anti‐angiogenesis and cancer therapy.     

Scutellaria barbata inhibits angiogenesis through downregulation of HIF‐1 α in lung tumor

Hypoxia, a hallmark of many solid tumors, is associated with angiogenesis and tumor progression. Hypoxia‐inducible factor‐1 (HIF‐1) plays a significant role in tumor angiogenesis. In this study, the authors constructed a selective platform to screen the traditional Chinese medicine as anti‐angiogenic agent. The authors examined the molecular mechanism by which Scutellaria barbata regulates HIF‐1‐dependent expression of vascular endothelial growth factor (VEGF), which is an important angiogenic factor. Hypoxia promotes angiogenesis by increasing VEGF expression and secretion. Herein, the expression of VEGF was decreased by treatment with S. barbata in tumor cells. Meanwhile, S. barbata reduced the migration and proliferation of endothelial cells under hypoxic condition. S. barbata inhibited the expression of HIF‐1α, as well as phosphorylated their upstream signal mediators AKT. S. barbata significantly inhibited the tumor growth in vivo and immunohistochemical studies in the tumors revealed decreased intratumoral microvessel density. These results suggest that the traditional Chinese medicine therapy using S. barbata, which exerts anti‐angiogenic activities, represents a promising strategy for the treatment of tumors. © 2012 Wiley Periodicals, Inc. Environ Toxicol 29: 363–370, 2014.     

99mTc‐anti‐epidermal growth factor receptor nanobody for tumor imaging

Nanobodies are important biomolecules for tumor targeting. In this study, we synthesized and labeled anti‐epidermal growth factor receptor (EGFR) nanobody OA‐cb6 with ^99mTc(CO)₃⁺ and evaluated its characteristics for targeting the EGFR in the A431 human epidermal carcinoma cell line. Nanobody radiolabeling was achieved with high yield and radiochemical purity, and the radioconjugate was stable. Biodistribution results in nude mice exhibited a favorable tumor‐to‐muscle ratio at 4‐hr postinjection, and tumor location was visualized at 4 hr after injection of radiolabeled nanobody. Our result showed that the OA‐cb6‐^99mTc‐tricarbonyl radiolabeled nanobody is a promising radiolabeled biomolecule for tumor imaging in cancers with high EGFR overexpression.     

Protocatechuic Acid Induces Angiogenesis through PI3K‐Akt‐eNOS‐VEGF Signalling Pathway

In this study, we sought to elucidate whether protocatechuic acid contributes to induce angiogenesis as well as its mechanisms. To this end, we examined the role of protocatechuic acid on human brain microvascular endothelial cell line (HBMEC) proliferation, invasion and tube formation in in vitro. For the study of mechanisms involved, the phosphoinositide 3 kinase (PI3K)‐Akt inhibitor LY294002, the endothelial nitric oxide synthase (eNOS) inhibitor L ‐NAME, vascular endothelial growth factor (VEGF), antagonist sFlt‐1 and VEGF receptor blocker SU‐1498 were used. Proliferation of HBMEC was tested by MTT. Scratch adhesion test was used to assess the ability of invasion. A Matrigel tube formation assay was performed to test capillary tube formation ability. PI3K‐Akt‐eNOS‐VEGF pathway activation in HBMEC was tested by Western blot. Our data suggested that protocatechuic acid induces angiogenesis in vitro by increasing proliferation, invasion and tube formation. VEGF expression was increasing by protocatechuic acid and counteracted by VEGF antagonist sFlt‐1, LY294002 and L‐NAME in HBMEC. Tube formation was increased by protocatechuic acid and counteracted by VEGF receptor blocker‐SU1498, LY294002 and L‐NAME. These data suggest that protocatechuic acid may be a candidate therapy for stroke recovery by promoting angiogenesis via a programmed PI3K/Akt/eNOS/VEGF signalling axis.     

Cytoprotective effects of endothelin‐1 on mesenchymal stem cells: an in vitro study

Stem cell‐based therapies is a promising approach for regenerative therapy in various diseases. Some obstacles remain to be solved before clinical application of the cell therapy is realized, including increasing the survival of transplanted stem cells, reducing loss of transplanted cells, and maintaining adequate vascular supply. Recently, stem cell preconditioning with chemical and pharmacological agents has been shown to increase therapeutic efficacy. The present study investigated the effect of endothelin‐1 (ET‐1) on survival, angiogenesis, and migration of mesenchymal stem cells (MSCs), in vitro. MSCs were treated with various concentrations of ET‐1 and the expression of cyclooxygenase‐2 (COX‐2), hypoxia‐inducible factor‐1 (HIF‐1), C‐X‐C chemokine receptor type 4 (CXCR4), C‐C chemokine receptor type 2 (CCR2), vascular endothelial growth factor (VEGF), angiopoietin‐2 (Ang‐2), angiopoietin‐4 (Ang‐4) and matrix metalloproteinase‐2 (MMP‐2) were examined. Caspase 3 activity and prostaglandin E2 (PGE2) were determined by ELISA assay. MSCs migration and tube formation potential were assessed using scratch test and three dimensional vessel formation assay. ET‐1 enhanced the MSCs viability. In ET‐1‐ treated MSCs, expression of COX‐2, HIF‐1, CXCR4, CCR2, VEGF, Ang‐2, Ang‐4 and MMP‐2 were increased compared to control groups. Elevation of all these genes were reversed by celecoxib (50 μmol/L), a selective COX‐2 inhibitor. PGE2 generation, MSCs migration and tube formation were enhanced by ET‐1 conditioning, whereas caspase‐3 activity was reduced in these cells, compared to the control group. The results presented here reveal that preconditioning of MSCs with ET‐1 has strong cytoprotective effects through activation of survival signalling molecules and trophic factors.     

Characterization of a Pyrazolo[4,3‐d]pyrimidine Inhibitor of Cyclin‐Dependent Kinases 2 and 5 and Aurora A With Pro‐Apoptotic and Anti‐Angiogenic Activity In Vitro

Selective inhibitors of kinases that regulate the cell cycle, such as cyclin‐dependent kinases (CDKs) and aurora kinases, could potentially become powerful tools for the treatment of cancer. We prepared and studied a series of 3,5,7‐trisubstituted pyrazolo[4,3‐d]pyrimidines, a new CDK inhibitor scaffold, to assess their CDK2 inhibitory and antiproliferative activities. A new compound, 2i , which preferentially inhibits CDK2, CDK5, and aurora A was identified. Both biochemical and cellular assays indicated that treatment with compound 2i caused the downregulation of cyclins A and B, the dephosphorylation of histone H3 at Ser10, and the induction of mitochondrial apoptosis in the HCT‐116 colon cancer cell line. It also reduced migration as well as tube and lamellipodia formation in human endothelial cells. The kinase inhibitory profile of compound 2i suggests that its anti‐angiogenic activity is linked to CDK5 inhibition. This dual mode of action involving apoptosis induction in cancer cells and the blocking of angiogenesis‐like activity in endothelial cells offers possible therapeutic potential.     

Preclinical evaluation of holmium‐166 labeled anti‐VEGF‐A(Bevacizumab)

Radiolabeled antiangiogenic monoclonal antibodies are potential agents for targeted therapy in specific types of malignancies. In this study, ¹⁶⁶Ho‐DOTA‐Bevacizumab was used in biodistribution studies using single‐photon emission computed tomography (SPECT) to acquire dosimetric aspects of the radiolabeled antibody in mice. The liver toxicity of the radiolabeled antibody was also determined using serum glutamic pyruvic transaminase, serum glutamic oxaloacetic transaminase and alkaline phosphatase assay 2–7 days post‐injection. The SPECT biodistribution demonstrated a similar pattern as the other radiolabeled anti‐ vascular endothelial growth factor A (VEGF‐A) immunoconjugates.¹⁶⁶Ho‐DOTA‐Bevacizumab was revealed as a potential compound for therapy/imaging of VEGF‐A expression in oncology. Copyright © 2013 John Wiley & Sons, Ltd.     

Using microdialysis to analyse the passage of monovalent nanobodies through the blood-brain barrier

BACKGROUND AND PURPOSE

Nanobodies are promising antigen-binding moieties for molecular imaging and therapeutic purposes because of their favourable pharmacological and pharmacokinetic properties. However, the capability of monovalent nanobodies to reach targets in the CNS remains to be demonstrated.

EXPERIMENTAL APPROACH

We have assessed the blood–brain barrier permeability of Nb_An33, a nanobody against the Trypanosoma brucei brucei variant-specific surface glycoprotein (VSG). This analysis was performed in healthy rats and in rats that were in the encephalitic stage of African trypanosomiasis using intracerebral microdialysis, single photon emission computed tomography (SPECT) or a combination of both methodologies. This enabled the quantification of unlabelled and ^99mTc-labelled nanobodies using, respectively, a sensitive VSG-based nanobody-detection elisa, radioactivity measurement in collected microdialysates and SPECT image analysis.

KEY RESULTS

The combined read-out methodologies showed that Nb_An33 was detected in the brain of healthy rats following i.v. injection, inflammation-induced damage to the blood–brain barrier, as in the late encephalitic stage of trypanosomiasis, significantly increased the efficiency of passage of the nanobody through this barrier. Complementing SPECT analyses with intracerebral microdialysis improved analysis of brain disposition. There is clear value in assessing penetration of the blood–brain barrier by monovalent nanobodies in models of CNS inflammation. Our data also suggest that rapid clearance from blood might hamper efficient targeting of specific nanobodies to the CNS.

CONCLUSIONS AND IMPLICATIONS

Nanobodies can enter the brain parenchyma from the systemic circulation, especially in pathological conditions where the blood–brain barrier integrity is compromised.     

Novel vascular endothelial growth factor blocker improves cellular viability and reduces hypobaric hypoxia‐induced vascular leakage and oedema in rat brain

Vascular endothelial growth factor (VEGF) is an important cerebral angiogenic and permeability factor under hypoxia. There is a need to find effective molecules that may ameliorate hypoxia‐induced cerebral oedema. In silico identification of novel candidate molecules that block VEGF‐A site were identified and validated with a Ramachandran plot. The active site residues of VEGF‐A were detected by Pocketfinder, CASTp, and DogSiteScorer. Based on in silico data, three VEGF‐A blocker (VAB) candidate molecules (VAB1, VAB2, and VAB3) were checked for improvement in cellular viability and regulation of VEGF levels in N2a cells under hypoxia (0.5% O₂). Additionally, the best candidate molecule's efficacy was assessed in male Sprague‐Dawley rats for its ameliorative effect on cerebral oedema and vascular leakage under hypobaric hypoxia 7260 m. All experimental results were compared with the commercially available VEGF blocker sunitinib. Vascular endothelial growth factor‐A blocker 1 was found most effective in increasing cellular viability and maintaining normal VEGF levels under hypoxia (0.5% oxygen) in N2a cells. Vascular endothelial growth factor‐A blocker 1 effectively restored VEGF levels, decreased cerebral oedema, and reduced vascular leakage under hypobaric hypoxia when compared to sunitinib‐treated rats. Vascular endothelial growth factor‐A blocker 1 may be a promising candidate molecule for ameliorating hypobaric hypoxia‐induced vasogenic oedema by regulating VEGF levels.     

Anti‐angiogenic potential of scopoletin is associated with the inhibition of ERK1/2 activation

Angiogenesis plays an important role in many diseases, such as cancer, rheumatoid arthritis, and diabetic retinopathy. Specific inhibitors of angiogenesis are therefore expected to be potential candidate therapeutics for these disorders. Recently, several naturally occurring coumarins and synthetic analogues have proved to hinder new vessel formation. The present study was undertaken to investigate the effects of scopoletin, a phenolic coumarin compound with various biological activities on endothelial cell activation and resultant angiogenesis. Scopoletin had no cytotoxic effect on endothelial cells at the concentrations tested but suppressed the endothelial cell migration and disrupted rat tail collagen tube formation at concentrations of 62.5, 125, 250, and 500 µM, whereas it only moderately inhibited the proliferation and adhesion of endothelial cells. Notably, scopoletin (500 µM) selectively downregulated serum‐induced ERK1/2 phosphorylation, without affecting endothelial cell p38 MAPK or JNK phosphorylation. These findings demonstrate that scopoletin has anti‐angiogenic properties that are manifest mainly through inhibiting migration and tube formation of endothelial cells via downregulating ERK1/2 activation. Scopoletin may potentially be useful for the treatment of angiogenesis‐mediated diseases and could serve as a structural basis for screening for more potent synthetic analogues. Drug Dev Res 2009. © 2009 Wiley‐Liss, Inc.     

Synthesis and characterization of scVEGF‐PEG‐[68Ga]NOTA and scVEGF‐PEG‐[68Ga]DOTA PET tracers

Vascular endothelial growth factor (VEGF) signaling via vascular endothelial growth factor receptor 2 (VEGFR‐2) on tumor endothelial cells is a critical driver of tumor angiogenesis. Novel anti‐angiogenic drugs target VEGF/VEGFR‐2 signaling and induce changes in VEGFR‐2 prevalence. To monitor VEGFR‐2 prevalence in the course of treatment, we are evaluating ⁶⁸Ga positron emission tomography imaging agents based on macrocyclic chelators, site‐specifically conjugated via polyethylene glycol (PEG) linkers to engineered VEGFR‐2 ligand, single‐chain (sc) VEGF. The ⁶⁸Ga‐labeling was performed at room temperature with NOTA (2,2′,2′′‐(1,4,7‐triazonane‐1,4,7‐triyl) triacetic acid) conjugates or at 90 °C by using either conventional or microwave heating with NOTA and DOTA (2,2′,2′′,2′′′‐(1,4,7,10‐tetraazacyclododecane‐1,4,7,10‐tetrayl) tetraacetic acid) conjugates. The fastest (~2 min) and the highest incorporation (>90%) of ⁶⁸Ga into conjugate that resulted in the highest specific radioactivity (~400 MBq/nmol) was obtained with microwave heating of the conjugates. The bioactivity of the NOTA‐ and DOTA‐containing tracers was validated in 3‐D tissue culture model of 293/KDR cells engineered to express high levels of VEGFR‐2. The NOTA‐containing tracer also displayed a rapid accumulation (~ 20 s after intravenous injection) to steady‐state level in xenograft tumor models. A combination of high specific radioactivity and maintenance of functional activity suggests that scVEGF‐PEG‐[⁶⁸ Ga]NOTA and scVEGF‐PEG‐[⁶⁸ Ga]DOTA might be promising tracers for monitoring VEGFR‐2 prevalence and should be further explored. Copyright © 2011 John Wiley & Sons, Ltd.     

New biological investigations on 3‐bromophenyl 6‐acetoxymethyl‐2‐oxo‐2H‐1‐benzopyran‐3‐carboxylate as anti‐angiogenic agent

The development of blood vessels inside tumors is required to provide the nutrients and oxygen needed for tumor growth and to allow the spread of cancer cells at a distance to form metastasis. Angiogenesis is also implicated in ocular diseases like age‐related macular degeneration. The present work describes the potential anti‐angiogenic properties of a coumarinic derivative, 3‐bromophenyl 6‐acetoxymethyl‐2‐oxo‐2H‐1‐benzopyran‐3‐carboxylate (IK9), previously described as a potent inhibitor of HT 1080 fibrosarcoma cell invasion in vitro and tumor growth in vivo. In vivo, ex vivo, and in vitro models were used to delineate the anti‐angiogenic properties of IK9. The anti‐angiogenic effect of IK9 was demonstrated in vivo in a choroidal neovascularization mice model and additionally ex vivo in a rat aortic ring assay where it was more active than the known matrix metalloproteinase inhibitor Ro 28‐2653. IK9 did not affect apoptosis, proliferation, or endothelial cell invasiveness in vitro. These findings suggest a complex mechanism of action of the compound via direct or indirect effects on endothelial cell properties. This study identifies IK9 as a new potent inhibitor of angiogenesis and suggests its potential use as a therapeutic agent. Drug Dev Res 71, 2010. © 2010 Wiley‐Liss, Inc.     

Preclinical pharmacokinetic and pharmacodynamic evaluation of thiazolidinone PG15: an anti‐inflammatory candidate

Objectives Novel 5‐benzilidene thiazolidinones have been synthesized and exhibited anti‐inflammatory activity. In this work one of the compounds of the thiazolidinone chemical series, (5Z,E)‐3‐[2‐(4‐chlorophenyl)‐2‐oxoethyl]‐5‐(1H‐indol‐3‐ ylmethylene)‐thiazolidine‐2,4‐dione (PG15) was investigated aiming to determine the drug's anti‐inflammatory potential in pre‐clinical studies. Methods Methods used included the in‐vitro inhibition of cyclooxygenase‐1 and ‐2, in‐vivo evaluation of anti‐inflammatory activity by air pouch and peritonitis models and the pharmacokinetic profile after intravenous (3 mg/kg) and oral (3 and 6 mg/kg) dosing to rats. Key findings A two‐compartment model with a fast distribution and an elimination half‐life of 5.9 ± 3.8 h described the PG15 plasma profile after intravenous dosing. PG15 showed an erratic and rapid absorption following oral administration with peak concentrations between 0.5 and 1 h. PG15 0.1 μM inhibited more than 30% and 13% of purified cyclooxygenase‐1 and ‐2 activity in vitro, respectively. A lack of dose dependency was observed for the anti‐inflammatory effect in the dose range investigated (0.8–50 mg/kg), with a maximum of 67.2 ± 4.6% inhibition of leucocyte migration in the carrageenan‐induced air pouch model obtained with the 3 mg/kg dose, similar to that observed for indometacin 10 mg/kg. Conclusions The erratic absorption of PG15 observed after oral dosing could explain the lack of anti‐inflammatory dose dependency.     

ASC,a Bioactive Steroidal Saponin from Ophitopogin japonicas,Inhibits Angiogenesis through Interruption of Src Tyrosine Kinase‐dependent Matrix Metalloproteinase Pathway

As angiogenesis is an important target for antitumour drugs, the agents that inhibit angiogenesis may help reduce the use of chemotherapy by blocking tumour blood supply. In this study, we investigated a potent angiogenesis inhibitor, ASC, a steroidal saponin compound, which has been purified from Ophitopogin japonicus (L.f) Ker.‐Gawl. Our observations showed that ASC significantly suppressed human umbilical vein endothelial cell (HUVECs) growth both in vitro and in vivo. This may be resulted from the G2/M cell cycle arrest effects of ASC. Moreover, ASC inhibited HUVECs invasion and tube formation processes, which were associated with endothelial cells remodelling. A mechanism study indicated that ASC down‐regulated the expression of Src tyrosine kinase, further leading to the blockage of Akt‐dependent matrix metalloproteinases (mainly for MMP‐9) signalling pathway, which was functionally associated with angiogenic blood vessels. Finally, ASC significantly inhibited angiogenesis and MMPs/VEGF expression in the subcutaneously injected matrigel in C57/BL mice. These findings suggest that ASC might be a potential drug candidate in anti‐angiogenesis and anticancer therapies.     

Radiolabeled nanobodies as theranostic tools in targeted radionuclide therapy of cancer

Introduction: The integration of diagnostic testing for the presence of a molecular target is of interest to predict successful targeted radionuclide therapy (TRNT). This so-called ‘theranostic’ approach aims to improve personalized treatment based on the molecular characteristics of cancer cells. Moreover, it offers new insights in predicting adverse effects and provides appropriate tools to monitor therapy responses. Recent findings using nanobodies emphasize their potential as theranostic tools in cancer treatment. Nanobodies are recombinant, small antigen-binding fragments that are derived from camelid heavy-chain-only antibodies.

Areas covered: We review the current status of theranostic approaches in TRNT, with a focus on antibodies, peptides, scaffold proteins and emerging nanobodies. In recent years, nanobodies have been evaluated intensively for molecular imaging. In addition, novel data on TRNT using radiolabeled nanobodies for carcinomas and multiple myeloma highlight their promising opportunities in cancer treatment.

Expert opinion: We trust that radiolabeled nanobodies will have a future potential as theranostic tools in cancer therapy, both for diagnosis as well as for TRNT.     

Borrelidin has limited anti‐cancer effects in bcl‐2 overexpressing breast cancer and leukemia cells and reveals toxicity in non‐malignant breast epithelial cells

Clinically effective anti‐cancer drugs have to tread a narrow line between selective cytotoxicity on tumor cells and tolerable adverse effects against healthy tissues. This causes the failure of many potential cancer drugs in advanced clinical trials, hence signifying the importance of a comprehensive initial estimate of the cytotoxicity of prospective anti‐cancer drugs in preclinical studies. In this study, the cytotoxicity of borrelidin, a macrolide antibiotic with a high cytotoxic selectivity for proliferating endothelial cells and leukemia cells, was tested on malignant and non‐malignant breast cells. Highly metastatic breast cancer cell lines (MDA‐MB‐231 and MDA‐MB‐435) showed promising results and exhibited good sensitivity to borrelidin at low nanomolar concentrations, but borrelidin was cytotoxic to a non‐malignant breast epithelial cell line (MCF10A) as well. Furthermore, although a high sensitivity of endothelial cells (human umbilical vein endothelial cells; HUVEC) and individual leukemia cell lines (Jurkat and IM9) to borrelidin was confirmed in this study, another leukemia cell line (HL60) and an immortalized endothelial cell line (EA.hy926) displayed a significantly decreased sensitivity. Reduced sensitivity to borrelidin was associated with elevated bcl‐2 expression in these cell lines. In conclusion, the results presented show that borrelidin displays high and selective cytotoxicity against subgroups of cancer cells and endothelial cells, but, owing to its non‐specific toxicity to non‐malignant cells, its clinical application might be restricted because of likely adverse effects and limited efficacy in bcl2‐overexpressing cancer cells. Copyright © 2013 John Wiley & Sons, Ltd.     

Methyl tert butyl ether is anti‐angiogenic in both in vitro and in vivo mammalian model systems

Methyl‐tertiary butyl ether (MTBE), a well known gasoline oxygenate, and US Food and Drug Administration approved gallstone treatment, has been previously shown to specifically target teleost embryonic angiogenesis. The studies reported here were to determine whether similar vascular disrupting effects occur in higher vertebrate models. Rat brain endothelial cells were isolated and allowed to form microcapillary‐like tubes on Matrigel. MTBE (0.34–34.0 mm ) exposure resulted in a dose‐dependent reduction of tube formation, with the LOAEL at 0.34 mm , while MTBE's primary metabolite, tertiary butyl alcohol had no effect on tube formation. HUVECs, a primary cell line representing macrovascular cells, were able to form tubes on Matrigel in the presence of MTBE (1.25–80 mm ), but the tubes were narrower than those formed in the absence of MTBE. In a mouse Matrigel plug implantation assay, 34.0 mm MTBE completely inhibited vessel invasion into plugs containing endothelial cell growth supplement (ECGS) compared with control plugs with ECGS alone. When timed‐pregnant Fisher 344 rats were gavaged with MTBE (500–1500 mg kg^?1) from day 6 of organogenesis through 10 days post‐parturition, no organ toxicity or histological changes in pup vasculature were observed. Results of the in vitro cell culture studies show that MTBE is anti‐angiogenic at mm concentrations and has potential use as an anti‐angiogenic treatment for solid tumors with minimal toxicity. Copyright © 2012 John Wiley & Sons, Ltd.