Biomedical subjects

Li-Ping Lin

Publications and source records attributed to Li-Ping Lin.

At least 19 recordsLinked to original sources

PubMed2007

Design, synthesis, antitumor evaluations and molecular modeling studies of novel 3,5-substituted indolin-2-one derivatives.

AIM: To design and synthesize a novel class of antitumor agents, featuring the 3, 5-substituted indolin-2-one framework. METHODS: Based on enzyme binding features of (Z)-SU5402, introducing a beta-pyrrole group at the 3-position of the indolin- 2-one core, a series of novel 3,5-substituted indolin-2-ones were designed and synthesized. Four human carcinoma cell lines of A-431, A-549, MDA-MB-468, and Autosomal Dominant Polycystic Kidney disease were chosen for the cell proliferation assay. RESULTS: Twenty new compounds (1a-t) with E configuration have been designed, synthesized and bioassayed. Their structural features were determined by nuclear magnetic resonance (NMR) spectra, low- and high-resolution mass spectra, and confirmed by X-ray crystallography. Although the enzyme assay showed a weak inhibition effect against the epidermal growth factor receptor, vascular endothelial growth factor receptor, fibroblast growth factor receptor and platelet-derived growth factor receptor tyrosine kinases, the cell-based antitumor activity was promising. Compounds 1 g and 1 h showed higher inhibitory activity toward the A-549 and MDA-MB-468 cell lines with IC(50 ) of 0.065-9.4 micromol/L. CONCLUSION: This study provides a new template for further development of potent antitumor drugs.

Antineoplastic Agents↗

PubMed2006

Xylogranatins A-D: novel tetranortriterpenoids with an unusual 9,10-seco scaffold from marine mangrove Xylocarpus granatum.

[reaction: see text] Four novel tetranortriterpenoids, xylogranatins A-D (1-4), with an unusual 9,10-seco skeleton were isolated from the seeds of a Chinese marine mangrove Xylocarpus granatum. Their structures were determined by spectroscopic and chemical means. Xylogranatin A (1) featured by a unique 1,9-oxygen bridge was confirmed by single-crystal X-ray diffraction, and xylogranatin D (4) with an unprecedented skeleton of C-30-C-9 linkage was postulated biogenetically from 3 via an alpha-hydroxyl ketone rearrangement and was chemically mimicked.

Animals↗

PubMed2006

Turrapubesins A and B, first examples of halogenated and maleimide-bearing limonoids in nature from Turraea pubescens.

[structure: see text] Two novel tetranortriterpenoids, turrapubesins A (1) and B (2), representing the first examples of halogenated and maleimide-bearing limonoids, were isolated from the twigs and leaves of Turraea pubescens. The structures of 1 and 2 were elucidated by extensive spectroscopic analysis. Their absolute configurations were determined by X-ray crystallography of 1 and by CD analysis of a dihydrogenated derivative of 2. Turrapubesin A (1) exhibited weak cytotoxicity against the P-388 tumor cell line.

Animals↗

PubMed2006

Salvicine functions as novel topoisomerase II poison by binding to ATP pocket.

Salvicine, a structurally modified diterpenoid quinone derived from Salvia prionitis, is a nonintercalative topoisomerase II (topo II) poison. The compound possesses potent in vitro and in vivo antitumor activity with a broad spectrum of anti-multidrug resistance activity and is currently in phase II clinical trials. To elucidate the distinct antitumor properties of salvicine and obtain valuable structural information of salvicine-topo II interactions, we characterized the effects of salvicine on human topo IIalpha (htopo IIalpha), including possible binding sites and molecular interactions. The enzymatic assays disclosed that salvicine mainly inhibits the catalytic activity with weak DNA cleavage action, in contrast to the classic topo II poison etoposide (VP16). Molecular modeling studies predicted that salvicine binds to the ATP pocket in the ATPase domain and superimposes on the phosphate and ribose groups. In a surface plasmon resonance binding assay, salvicine exhibited higher affinity for the ATPase domain of htopo IIalpha than ATP and ADP. Competitive inhibition tests demonstrated that ATP competitively and dose-dependently blocked the interactions between salvicine and ATPase domain of htopo IIalpha. The data illustrate that salvicine shares a common binding site with ATP and functions as an ATP competitor. To our knowledge, this is the first report to identify an ATP-binding pocket as the structural binding motif for a nonintercalative eukaryotic topo II poison. These findings collectively support the potential value of an ATP competitor of htopo IIalpha in tumor chemotherapy.

Adenosine Triphosphatases↗

PubMed2006

Growth arrest induced by C75, A fatty acid synthase inhibitor, was partially modulated by p38 MAPK but not by p53 in human hepatocellular carcinoma.

C75, a well-known fatty acid synthase (FAS) inhibitor, has been shown to possess potent anti-cancer activity in vitro and in vivo. In this study, we reveal that C75 is a cell cycle arrest inducer and explore the potential mechanisms for this effect in hepatocellular carcinoma (HCC) cell lines with abundant FAS expression: HepG2 and SMMC7721 cells with wt-p53, and Hep3B cells with null p53. The results showed FAS protein expression and basal activity levels were higher in HepG2 cells than in the other two HCC cell lines. Treatment with C75 inhibited FAS activity within 30 min of administration and induced G(2) phase arrest accompanied by p53 overexpression in HepG2 and SMMC7721 cells. By contrast, C75 triggered G(1) phase arrest in Hep3B cells, and RNA interference targeting p53 did not attenuate C75-induced G(2) arrest in HepG2 cells. Similarly, p53 overexpression via p53 plasmid transfection did not affect C75-induced G(1) phase arrest in Hep3B cells. However, we observed a clear correlation between p38 MAPK activation triggered by C75 and the induction of cell cycle arrest in all three HCC cells. Furthermore, treatment with the p38 MAPK inhibitor SB203580 reduced p38 MAPK activity and cell cycle arrest, and also partially restored cyclin A, cyclin B1, cyclin D1 and p21 protein levels. Collectively, it was p38 MAPK but not p53 involved in C75-mediated tumor cell growth arrest in HCC cells.

4-Butyrolactone↗

PubMed2006

Flueggenines A and B, two novel C,C-linked dimeric indolizidine alkaloids from Flueggea virosa.

[structure: see text] Two unprecedented C,C-linked dimeric indolizidine alkaloids, flueggenines A (1) and B (2), as well as their biosynthetic precursor (-)-norsecurinine, were isolated from the roots of Flueggea virosa. Their structures and absolute configurations were elucidated by spectroscopic methods, especially 2D NMR and CD spectral analyses, and supported by their unique biosynthetic pathway as proposed. Both 1 and 2 were tested against two tumor cell lines, and alkaloid 1 showed weak activity against the P-388 cell line.

Alkaloids↗

PubMed2006

Grateloupia longifolia polysaccharide inhibits angiogenesis by downregulating tissue factor expression in HMEC-1 endothelial cells.

1. The antiangiogenic and antitumor properties of Grateloupia longifolia polysaccharide (GLP), a new type of polysaccharide isolated from the marine alga, were investigated with several in vitro and in vivo models. Possible mechanisms underlying its antiangiogenic activity were also assessed. 2. GLP dose-dependently inhibited proliferation of human microvascular endothelial cells (HMEC-1) and human umbilical vein endothelial cells (HUVEC), with IC50 values of 0.86 and 0.64 mg ml(-1), respectively. In tube formation and cell migration assays using HMEC-1 cells, noncytotoxic doses of GLP significantly inhibited formation of intact tube networks and reduced the number of migratory cells. Inhibition by GLP was VEGF-independent. 3. In the chick chorioallantoic membrane (CAM) assay, GLP (2.5 microg egg(-1)) reduced new vessel formation compared with the vehicle control. GLP (0.1 mg plug(-1)) also reduced the vessel density in Matrigel plugs implanted in mice. 4. The levels of pan and phosphorylated receptors for VEGF, VEGFR-1 (flt-1) and VEGFR-2 (KDR) were not significantly altered by 5 mg ml(-1) GLP treatment of HMEC-1, although tissue factor (TF) showed significant decreases at both mRNA and protein levels following GLP treatment. 5. In mice bearing sarcoma-180 cells, intravenous administration of GLP (200 mg kg(-1)) decreased tumor weight by 52% without obvious toxicity. Vascular density in sections of the tumor was reduced by 64% after GLP treatment. 6. Collectively, these results indicate that GLP has antitumor properties, associated at least, in part, with the antiangiogenesis induced by downregulation of TF.

Angiogenesis Inhibitors↗

PubMed2006

TKI-31 inhibits angiogenesis by combined suppression signaling pathway of VEGFR2 and PDGFRbeta.

Tyrosine kinases have been strongly implicated as therapeutic targets that influence the angiogenic process in growing tumors. In this study, we revealed that TKI-31 is a potent broad spectrum tyrosine kinase inhibitor, which inhibits vascular endothelial growth factor receptor 2 (VEGFR2), platelet-derived growth factor receptor beta (PDGFRbeta) and also inhibits kinases of other class, such as c-Kit and c-Src on molecular base, but showed no activity against vascular endothelial growth factor receptor 1 (VEGFR1) and epidermal growth factor receptor (EGFR). TKI-31 inhibits VEGF-induced phosphorylation of VEGFR2 in endothelial cells as well as PDGF(BB)-induced phosphorylation in fibroblast cells, and leading to the inhibition of down-stream signaling triggered by these receptors such as PI3K/Akt/mTOR, MAPK42/44(ERK) and paxillin. TKI-31 also inhibited VEGF-induced endothelial cells proliferation, migration and their differentiation into capillary-like tube formation. Its anti-angiogenic property was further confirmed by the inhibition of neovascularization on CAM, in vivo. These results collectively highlight the therapeutic potential of this compound for the treatment of solid tumors and other diseases where angiogenesis plays an important role.

Angiogenesis Inhibitors↗

PubMed2006

Pseudolarix acid B, a new tubulin-binding agent, inhibits angiogenesis by interacting with a novel binding site on tubulin.

Tubulin-binding agents have received considerable interest as potential tumor-selective angiogenesis-targeting drugs. Herein, we report that pseudolarix acid B (PAB), isolated from the traditional Chinese medicinal plant Pseudolarix kaempferi Gordon, is a tubulin-binding agent. We further demonstrate that PAB significantly and dose-dependently inhibits proliferation, migration, and tube formation by human microvessel enthothelial cells. It is noteworthy that PAB eliminated newly formed endothelial tubes and microvessels both in vitro and in vivo. In addition, PAB dramatically arrested the cell cycle at G2/M phase. PAB also induced endothelial cell retraction, intercellular gap formation, and promoted actin stress fiber formation in conjunction with disruption of the tubulin and actin cytoskeletons. All of these effects occurred at noncytotoxic concentrations of PAB. We found that these effects of PAB are attributable to depolymerization of tubulin by direct interaction with a distinct binding site on tubulin compared with those of colchicine and vinblastine. Taken together, these findings show that PAB is a candidate antiangiogenic agent for use in cancer therapy, and they provide proof of principle for targeting this novel binding site on tubulin as a new strategy for treating cancer.

Angiogenesis Inhibitors↗

PubMed2006

Alkaloids from Gelsemium elegans.

Three new alkaloids, gelsebanine (1), 14alpha-hydroxyelegansamine (2), and 14alpha-hydroxygelsamydine (3), and a new extraction artifact , gelsebamine (4), together with 12 known alkaloids, were isolated from the stems and leaves of Gelsemium elegans. The structures of 1-4 were determined by spectroscopic methods, especially 2D NMR techniques. Compounds 1-4 were evaluated for cytotoxic activity against four tumor cell lines, and gelsebamine (4) selectively inhibited the A-549 human lung adenocarcinoma cell line.

Antineoplastic Agents, Phytogenic↗

PubMed2005

In vitro pharmacological characterization of TKI-28, a broad-spectrum tyrosine kinase inhibitor with anti-tumor and anti-angiogenic effects.

Tyrosine kinases are used as important biomarkers in many tumor types. Preclinical and clinical anti-tumor studies have shown that broadly acting tyrosine kinase inhibitors may be more useful than specific inhibitors, since the former might overcome redundancies and crosstalk in tumor cell growth signaling pathways. Here, we aim to identify a novel potent tyrosine kinase inhibitor. Computer modeling of the pyrido-pyrimidine class compound, TKI-28(6-(2,6-dichlorophenyl)-8-methyl-2-phenylamino-8H-pyrido[2,3-d]pyrimidine-7-one), predicted that the compound would dock well in the ATP pocket of the ErbB-2 tyrosine kinase, yielding a high binding affinity for ErbB receptors. Biochemical studies revealed that TKI-28 potently inhibited the activities of tyrosine kinases such as ErbB-2, EGFR, KDR, PDGFRbeta, c-kit and c-Src, but had little effect on Flt-1 in cell-free system. TKI-28 also efficiently blocked autophosphorylation of the listed receptor tyrosine kinases, and subsequently downregulated phosphorylation of many downstream signaling proteins at the cellular level. TKI-28 exhibited a more potent anti-proliferative activity against EGF- and neuregulin-stimulated SK-OV-3 cells versus serum-stimulated cells, accompanied by apparent induction of apoptosis. Finally, TKI-28 was found to possess anti-angiogenic effects, characterized by inhibition of cell proliferation driven by EGF, VEGF and PDGF, as well as decreased cell migration and tube formation in HMECs. These results collectively highlight the pharmacological characteristics of TKI-28 as a broad-spectrum tyrosine kinase inhibitor, suggesting that it has great potential as an anti-cancer and anti-angiogenesis agent.

Animals↗

PubMed2005

Synthesis and antitumor evaluation of novel 5-substituted-4-hydroxy-8-nitroquinazolines as EGFR signaling-targeted inhibitors.

The synthesis and biological activity of a series of novel 5-substituted-4-hydroxy-8-nitroquinazolines that may function as inhibitors of EGFR- and/or ErbB-2-related oncogenic signaling are described. These compounds were prepared by S(N)Ar reaction of 5-chloro-4-hydroxy-8-nitroquinazoline with alkyl or aryl amines, or alkyl alcohol as nucleophiles. Although the enzyme assay showed a weak inhibition effect against both EGFR and ErbB-2 tyrosine kinases, the cell-based antitumor activity turned out promising. Compounds having 5-anilino substituent exhibit high potency with 5-(4-methoxy)anilino-4-hydroxy-8-nitroquinazoline (1h) being the best dual EGFR/ErbB-2 inhibitors, which effectively inhibited the growth of both EGFR (MDA-MB-468, IC(50)<0.01microM) and ErbB-2 (SK-BR-3, IC(50)=13microM) overexpressing human tumor cell lines in vitro. More interestingly, the variation of the substituent(s) at the 3- and/or 4-position of the 5-anilino portion was found to modulate the selectivity and potency dramatically. However, compounds having an alkylamino or alkyloxy group at the 5-position of 4-hydroxy-8-nitroquinazolines are essentially inactive. These results are consistent with molecular modeling observations. This study was the first attempt to identify new structural types of dual EGFR/ErbB-2-related signaling inhibitors by incorporation of the anilino group at the 5-position of 4-hydroxy-8-nitroquinazolines' core structure, providing promising new templates for further development of potent inhibitors targeting both EGFR and ErbB-2 tyrosine kinases.

Antineoplastic Agents↗

PubMed2005

Antimetastatic effect of salvicine on human breast cancer MDA-MB-435 orthotopic xenograft is closely related to Rho-dependent pathway.

PURPOSE: Salvicine is a novel DNA topoisomerase II inhibitor with potent anticancer activity. In present study, the effect of salvicine against metastasis is evaluated using human breast carcinoma orthotopic metastasis model and its mechanism is further investigated both in animal and cellular levels. EXPERIMENTAL DESIGN: The MDA-MB-435 orthotopic xenograft model was applied to detect the antimetastatic effect of salvicine. Potential target candidates were detected and analyzed by microarray technology. Candidates were verified and explored by reverse transcription-PCR and Western blot. Salvicine activities on stress fiber formation, invasion, and membrane translocation were further investigated by immunofluorescence, invasion, and ultracentrifugal assays. RESULTS: Salvicine significantly reduced the lung metastatic foci of MDA-MB-435 orthotopic xenograft, without affecting primary tumor growth obviously. A comparison of gene expression profiles of primary tumors and lung metastatic focus between salvicine-treated and untreated groups using the CLOTECH Atlas human Cancer 1.2 cDNA microarray revealed that genes involved in tumor metastasis, particularly those closely related to cell adhesion and motility, were obviously down-regulated, including fibronectin, integrin alpha3, integrin beta3, integrin beta5, FAK, paxillin, and RhoC. Furthermore, salvicine significantly down-regulated RhoC at both mRNA and protein levels, greatly inhibited stress fiber formation and invasiveness of MDA-MB-435 cells, and markedly blocked translocation of both RhoA and RhoC from cytosol to membrane. CONCLUSION: The unique antimetastatic action of salvicine, particularly its specific modulation of cell motility in vivo and in vitro, is closely related to Rho-dependent signaling pathway.

Animals↗

PubMed2005

Antiangiogenic activity of 11,11'-dideoxyverticillin, a natural product isolated from the fungus Shiraia bambusicola.

The fungus Shiraia bambusicola yields the phytochemical 11,11'-dideoxyverticillin, which has been shown to possess potent anticancer activity both in vitro and in vivo. In this study, we reveal that 11,11'-dideoxyverticillin has anti-angiogenic activities and explore the potential mechanisms for this effect. Treatment with 11,11'-dideoxyverticillin inhibited the proliferation of human umbilical vein endothelial cells (HUVECs) with IC(50) values of 0.17+/-0.05muM for VEGF-stimulated cells and 0.39+/-0.08muM for serum-stimulated cells. 11,11'-Dideoxyverticillin also antagonized the antiapoptotic effects of VEGF on serum-deprived HUVECs, inhibited VEGF-induced HUVEC migration in vitro, and blocked serum-induced HUVEC tube formation. Moreover, 11,11'-dideoxyverticillin completely blocked VEGF-induced microvessel sprouting from Matrigel-embedded rat aortic rings and vessel growth in Matrigel plugs in mice. In addition, 11,11'-dideoxyverticillin decreased VEGF secretion by MDA-MB-468 breast cancer cells, and significantly suppressed VEGF-induced tyrosine phosphorylation of Flt-1 and KDR/Flk-1. This inhibition of receptor phosphorylation was correlated with a marked decrease in VEGF-triggered pERK activation and a dramatic increase in pP38 MAPK, but no apparent change in pAkt. Together, these findings strongly suggest that 11,11'-dideoxyverticillin is a structurally novel angiogenesis inhibitor.

Angiogenesis Inhibitors↗

PubMed2005

Expression and purification of the catalytic domain of human vascular endothelial growth factor receptor 2 for inhibitor screening.

Vascular endothelial growth factor (VEGF), an endothelial cell-specific mitogen, can act in tumor-induced angiogenesis by binding to specific receptors on the surface of endothelial cells. One such receptor, VEGFR-2/KDR, plays a key role in VEGF-induced angiogenesis. Here, we expressed the catalytic domain of VEGFR-2 as a soluble active kinase using Bac-to-Bac expression system, and investigated correlations between VEGFR-2 activity and enzyme concentration, ATP concentration, substrate concentration and divalent cation type. We used these data to establish a convenient, effective and non-radioactive ELISA screening technique for the identification and evaluation of potential inhibitors for VEGFR-2 kinase. We screened 200 RTK target-based compounds and identified one (TKI-31) that potently inhibited VEGFR-2 kinase activity (IC50=0.596 microM). Treatment of NIH3T3/KDR cells with TKI-31 blocked VEGF-induced phosphorylation of KDR in a dose-dependent manner. Moreover, TKI-31 dose-dependently suppressed HUVEC tube formation. Thus, we herein report a novel, efficient method for identifying VEGFR-2 kinase inhibitors and introduce one, TKI-31, that may prove to be a useful new angiogenesis inhibitor.

Animals↗

PubMed2005

11,11'-dideoxy-verticillin: a natural compound possessing growth factor receptor tyrosine kinase-inhibitory effect with anti-tumor activity.

11,11'-dideoxy-verticillin, a compound of the novel epidithiodioxopiprazine structural class, is isolated from the traditional Chinese medicinal herb Shiraia bambusicola. The present study demonstrated for the first time that 11,11'-dideoxy-verticillin has potent tyrosine kinase-inhibitory and anti-tumor activities. In the cell-free ELISA tyrosine kinase assay, 11,11'-dideoxy-verticillin significantly inhibited the activities of epidermal growth factor receptor (EGFR), vascular endothelial growth factor receptor-1/fms-like tyrosine kinase-1 (VEGFR-1/Flt-1) and human epidermal growth factor receptor-2 (HER2/ErbB-2), with relative specificity on EGFR and VEGFR-1 with IC50s of 0.136+/-0.109 and 1.645+/-0.885 nM, respectively. Exposure of 11,11'-dideoxy-verticillin for 1 h to EGFR-overexpressed MDA-MB-468 human breast carcinoma cells and HER2-overexpressed SK-OV-3 human ovarian adenocarcinoma cells resulted in obvious inhibition of EGF-induced phosphorylation of EGFR and HER2. In addition, 11,11'-dideoxy-verticillin also inhibited the EGF-induced phosphorylation of Erk1/2, but had no effect on the phosphorylation of AKT in both tumor cell lines. Moreover, 11,11'-dideoxy-verticillin has potent anti-tumor activity. In vitro cytotoxicity assay showed that 11,11'-dideoxy-verticillin potently inhibited the proliferation of four human breast tumor cell lines with an average IC50 value of 0.2 microM. In vivo, 11,11'-dideoxy-verticillin exhibited remarkable efficacy against mice sarcoma 180 and hepatoma 22 after daily i.p. administration of 0.5 or 0.75 mg/kg with inhibition rates ranging from 45.0 to 72.4%. Treated with 11,11'-dideoxy-verticillin at 0.5-2.0 microM for 36 h, MB-MB-468 cells exhibited significant apoptotic morphological changes. At low concentrations (0.0625-0.5 microM) for 24 h, 11,11'-dideoxy-verticillin induced a dose-dependent accumulation of MDA-MB-468 cells in the G2/M phase of the cell cycle. These results indicate that 11,11'-dideoxy-verticillin is a naturally derived growth factor receptor tyrosine kinase inhibitor with potent anti-tumor activity.

Animals↗

PubMed2004

Pseudolaric acid B inhibits angiogenesis and reduces hypoxia-inducible factor 1alpha by promoting proteasome-mediated degradation.

PURPOSE: Pseudolaric acid B (PAB), the naturally occurring diterpenoid isolated from the root bark of Pseudolarix kaempferi Gordon tree (Pinaceae), possesses potent antifungal and pregnancy-terminating effects that may be tightly associated with angiogenesis. This study was to examine its angiogenic inhibition, impact on vascular endothelial growth factor (VEGF) secretion from tumor cells and the possible mechanism of action. EXPERIMENTAL DESIGN: Angiogenesis inhibition was assessed by the human umbilical vascular endothelial cell proliferation, migration, and tube-formation assays, as well as the chorioallantoic membrane assay. ELISA, reverse transcription-PCR, and Western blotting analyses were performed to examine VEGF protein secretion, mRNA expression, and the possible mechanism in hypoxic MDA-MB-468 cells. RESULTS: PAB displayed potent in vitro antiangiogenic activity shown by inhibiting VEGF-stimulated proliferation and migration and fetal bovine serum-stimulated tube formation of human umbilical vascular endothelial cells in a concentration-dependent manner. Moreover, PAB (10 nmol per egg) significantly suppressed in vivo angiogenesis in the chorioallantoic membrane assay. On the other hand, PAB abrogated hypoxia-induced VEGF secretion from MDA-MB-468 cells via reducing HIF-1alpha protein. Additional analyses using LY294002 and U0126 indicated that the increase in hypoxia-inducible factor 1 (HIF-1)alpha protein level was highly dependent on phosphatidylinositol 3'-kinase and p42/p44 mitogen-activated protein kinase activities in hypoxic MDA-MB-468 cells. However, PAB treatment did not affect the active (phosphorylated) forms of Akt and Erk. Interestingly, the selective proteasome inhibitor MG-132 completely reversed the reduction of HIF-1alpha protein in the PAB-treated MDA-MB-468 cells. CONCLUSIONS: PAB displays the dual antiangiogenic activities of directly inhibiting endothelial cells and abrogating paracrine stimulation of VEGF from tumor cells due to reducing HIF-1alpha protein by promoting its proteasome-mediated degradation in MDA-MB-468 cells, which has potential clinical relevance.

Animals↗

PubMed2004

Pseudolarix acid B inhibits angiogenesis by antagonizing the vascular endothelial growth factor-mediated anti-apoptotic effect.

Angiogenesis is controlled by a number of growth factors, including vascular endothelial growth factor (VEGF). In this study, pseudolarix acid B, isolated from the traditional Chinese medicinal plant Pseudolarix kaempferi and originally identified as an early pregnancy-terminating agent, was evaluated for its potential as an angiogenesis inhibitor, using in vitro and in vivo models. After exposure to pseudolarix acid B 0.625-5 microM for 72 h, the proliferation of human umbilical vein endothelial cells was significantly inhibited. Pseudolarix acid B 0.313-2.5 microM for 24 h potently blocked the VEGF-induced tube formation of human umbilical vein endothelial cells in a dose-dependent manner. Matrigel plug assays disclosed that pseudolarix acid B reduced angiogenesis induced by VEGF in vivo. In addition, pseudolarix acid B antagonized VEGF-mediated anti-apoptotic effects on serum-deprived human umbilical vein endothelial cells and increased apoptosis of endothelial cells induced by VEGF in Matrigel plug assays. Moreover, pseudolarix acid B significantly inhibited VEGF-induced tyrosine phosphorylation of kinase insert domain-containing receptor/fetal liver kinase-1 (KDR/flk-1), in correlation with a marked decrease in the phosphorylation of Akt and extracellular signal-regulated kinases (ERK). These findings collectively suggest that pseudolarix acid B possesses anti-angiogenic activity. One of the main anti-angiogenesis mechanisms of pseudolarix acid B may involve antagonism of the VEGF-mediated anti-apoptosis effect via inhibition of KDR/flk-1, ERK1/2, and Akt phosphorylation in endothelial cells.

Angiogenesis Inhibitors↗