Emodin inhibits vascular endothelial growth factor-A-induced angiogenesis by blocking receptor-2 (KDR/Flk-1) phosphorylation

6th Saturday, 2012  |   Herb or Compound  |  no comments

Kwak H-J et al International Journal of Cancer. Volume 118, Issue 11, pages 2711–2720, 1 June 2006 DOI: 10.1002/ijc.21641
Emodin (1,3,8-trihydroxy-6-methylanthraquinone), an active component in the root and rhizome of Rheum palmatum, is a tyrosine kinase inhibitor with a number of biological activities, including antitumor effects. Here, we examine the effects of emodin on vascular endothelial growth factor (VEGF)-A-induced angiogenesis, both in vitro and in vivo. In vitro, emodin dose-dependently inhibits proliferation, migration into the denuded area, invasion through a layer of Matrigel and tube formation of human umbilical vein endothelial cells (HUVECs) stimulated with VEGF-A. Emodin also inhibits basic fibroblast growth factor-induced proliferation and migration of HUVECs and VEGF-A-induced tube formation of human dermal microvascular endothelial cells. Specifically, emodin induces the cell cycle arrest of HUVECs in the G0/G1 phase by suppressing cyclin D1 and E expression and retinoblastoma protein phosphorylation, and suppresses Matrigel invasion by inhibiting the basal secretion of matrix metalloproteinase-2 and VEGF-A-stimulated urokinase plasminogen activator receptor expression. Additionally, emodin effectively inhibits phosphorylation of VEGF-A receptor-2 (KDR/Flk-1) and downstream effector molecules, including focal adhesion kinase, extracellular signal-regulated kinase 1/2, p38 mitogen-activated protein kinase, Akt and endothelial nitric oxide synthase. In vivo, emodin strongly suppresses neovessel formation in the chorioallantoic membrane of chick and VEGF-A-induced angiogenesis of the Matrigel plug in mice. Our data collectively demonstrate that emodin effectively inhibits VEGF-A-induced angiogenesis in vitro and in vivo. Moreover, inhibition of phosphorylation of KDR/Flk-1 and downstream effector molecules is a possible underlying mechanism of the anti-angiogenic activity of emodin. Based on these data, we propose that an interaction of emodin with KDR/Flk-1 may be involved in the inhibitory function of emodin toward VEGF-A-induced angiogenesis in vitro and responsible for its potent anti-angiogenic in vivo. © 2006 Wiley-Liss, Inc.
Angiogenesis, the formation of new vessels from preexisting vasculature, is an essential process in a variety of physiological and pathological conditions, including wound healing, embryonic development, chronic inflammation, cancer and metastasis.1, 2, 3, 4, 5 Complex sequential steps are involved in angiogenesis, such as basement membrane degradation by proteases, endothelial cell proliferation and migration, formation of capillary tubes and survival of newly formed blood vessels.6 Angiogenesis is tightly regulated by an intricate balance between stimulators and inhibitors.6 Among these, vascular endothelial growth factor (VEGF)-A, a soluble angiogenic factor produced by many tumors as well as normal cell lines, including vascular smooth muscle cells, lung epithelium and pituitary folliculo-stellate cells, plays a key role in regulating normal and pathologic angiogenesis.7
VEGF-A is a potent mitogen for endothelial cells, and an important mediator of angiogenesis, inducing endothelial cell proliferation, protease expression and migration, as well as subsequent organization of cells to form a capillary tube.8, 9, 10 In particular, a number of studies have shown that VEGF-A is the most important angiogenic factor closely associated with neovascularization in human tumors. Recent reports have disclosed increased VEGF-A mRNA in tumor cell lines. The VEGF-A level is an important prognostic marker of tumor angiogenesis.10, 11 VEGF-A induces angiogenesis via binding to its two receptor tyrosine kinases, KDR/Flk-1 and Flt-1, expressed on endothelial cells. KDR/Flk-1 is required mainly for mitogenic and chemotactic responses, whereas Flt-1 contributes to endothelial cell morphogenesis.12, 13 Recently, the intracellular signaling pathways mediating these effects downstream of KDR/Flk-1 activation have been identified. KDR/Flk-1 induces proliferation through activation of the extracellular signal-regulated kinase (ERK) 1/2 pathway leading to gene transcription14 and endothelial cell survival through phosphatidylinositol 3-kinase activation, resulting in increased lipid phosphatidylinositol (3,4,5)P3 and activation of several important intracellular molecules, such as Akt and the small GTP-binding protein, Rac.15 The Akt pathway additionally triggers endothelial nitric oxide synthase (eNOS) activity16, 17 to generate NO, leading to vascular permeability and cellular migration. Other signal transduction molecules implicated in KDR/Flk-1-dependent cytoskeletal regulation and cell migration include p38 mitogen-activated protein kinase (MAPK) and p125 focal adhesion kinase (FAK).18, 19
Emodin (1,3,8-trihydroxy-6-methylanthraquinone), a tyrosine kinase inhibitor isolated from Rheum palmatum, is an active constituent of Chinese herbs.20 The compound sensitizes HER-2/neu-overexpressing lung cancer cells, has antitumor effects on neuroectodermal and represses transformation and metastasis-associated properties of HER-2/neu-overexprssing breast cancer cells.20, 21, 22 Emodin additionally exerts anti-inflammatory effects on endothelial cells by inhibiting tumor necrosis factor -induced activation of nuclear factor-kappa B in human umbilical vein endothelial cells (HUVECs).23 Given that numerous endogenous factors and pharmacological agents that regulate cancer progression and inflammation additionally affect angiogenesis, it seems quite likely that emodin would also affect angiogenesis. In the present study, we investigated whether emodin has anti-angiogenic activity especially on the VEGF-A-induced angiogenesis, and if so, the critical mechanism of action.
Our data show that emodin significantly inhibits VEGF-A-induced angiogenesis in vitro and in vivo. Emodin effectively blocks VEGF-A-induced proliferation, migration, invasion and tube formation of HUVECs in vitro, and markedly inhibits neo-angiogenesis of chick chorioallantoic membrane (CAM) and mouse Matrigel in vivo. Blockade of VEGF-A-induced tyrosine phosphorylation of KDR/Flk-1 and downstream signaling molecules by emodin may be responsible for its potent anti-angiogenic activity. The results strongly highlight the efficacy of this compound in controlling neovessel formation in diseases induced by angiogenesis.

Anthraquinone derivative emodin inhibits tumour-associated angiogenesis through inhibition of extracellular signal-regulated kinase 1/2 phosphorylation

6th Saturday, 2012  |   Herb or Compound  |  no comments

Kaneshiro T et al. European Journal of Pharmacology. Volume 553, Issues 1-3, 28 December 2006, Pages 46-53 doi:10.1016/j.ejphar.2006.09.026
An anthraquinone derivative, emodin, suppresses tumor development both in vitro and in vivo. In this study, we examined the anti-angiogenic activity of emodin and its modifying effect on the phosphorylation of extracellular signal-regulated kinase (ERK) 1/2. In cell cultures, emodin inhibited endothelial cell proliferation, migration, and tube formation in a dose-dependent manner. In addition, the mouse dorsal air sac assay revealed the vivo anti-angiogenic potential of emodin. Matrix metalloproteinase-9 (MMP-9) expression, which is critical for the angiogenic process, including migration and tube formation, decreased after exposure to emodin, as determined by polymerase chain reaction with reverse transcription (RT-PCR) and gelatin zymography. Moreover, the phosphorylation of ERK 1/2 decreased after exposure to emodin in a dose-dependent manner. These observations suggest that emodin has the potential to inhibit several angiogenic processes and that these effects may be related to suppression of the phosphorylation of ERK 1/2.

Effect of weikangning decoction on expression of cyclin E, CDK2, and p27

6th Saturday, 2012  |   Herb or Compound  |  no comments

Kan FJ, Li QM, Zhong W, Liang WW. Zhong Yao Cai. 2006 Apr;29(4):341-5.
To observe the effect of containing drugs serum of weikanguing decoction (WKN) on expression of Cyclin E, CDK2 (Cyclin dependant kinase 2, CDK2) and p27 in gastric cancer cell line MGC-803.
METHODS:
Total of 120 male Wistar rats were divided into control group, high dose group, medium dose group and low dose group fed with natural saline, 20,10, and 5 g/kg of WKN, respectively. The experimental animals were finally killed for the preparation of drug-containing serum. The gastric cancer cell MGC-803 was cultured with the drug-containing serum drawn from the rats in different groups. The expression of Cyclin E, CDK2 and p27 was detected with immunohistochemistry method-SABC. The expression of mRNA of Cyclin E, CDK2 and p27 were detected with RT-PCR.
RESULTS:
In high, medium and low dose groups, the gray scales of cyclin E, CDK2 and the OPDTI values of p27 increased significantly, but the gray scales of p27 and the OPDTI values of cyclin E, CDK2 decreased remarkble, compared with that in control group.
CONCLUSION:
The decoction of WKN can decrease the expression of Cyclin E, CDK2, increases the expression of p27. This effect may be involved in mechanism of gastric cancer cell growth inhibition induced by WKN.

Anti-proliferation effect of serum containing WEI KANG NING on gastric cancer MGC-803 cells and its mechanism

6th Saturday, 2012  |   Stomach Cancer  |  no comments

Feng CX et al. Zhong Yao Cai. 2006 May;29(5):456-8.
OBJECTIVE:
To investigate the anti-proliferation effect of WEI KANG NING on gastric cancer.
METHODS:
MGC-803 cells were cultured in different concentrations of serum containing WEI KANG NING. The inhibitory ratio of the cells was measured by MTT assay. Apoptosis was observed by Hoechst 33258 fluorescence staining.
RESULTS:
Each concentration of serum containing WEI KANG NING could inhibit cells proliferation. Among them, both high and medium concentration could inhibit longer. Moreover, high concentration could induce cells apoptosis.
CONCLUSION:
WEI KANG NING serum has anti-proliferation effect on MGC-803 cells and the effect may be related to cell apoptosis induced by WEI KANG NING.

Effect of Weikangning on gastric cancer cell growth and expression of vascular endothelial growth factor and its receptors KDR and Flt-1

6th Saturday, 2012  |   Stomach Cancer  |  no comments

Li Q-M et al. World J Gastroenterol 2005;11(7):938-942
Abstract
AIM: To observe the effect of Chinese traditional herbal decoction Weikang-ning (WKN) on cell growth and expression of VEGF and its receptors KDR and Flt-1 in gastric cancer cell line MGC-803.
RESULTS: The proportion of cells in G0-G1 phase was (65.40±0.41)%, (56.92±0.62)%, (55.89±0.69)% in high, medium and low dose groups respectively vs (41.35±0.55)% in control group (P<0.01), while the cells in G2-S and S phases were (11.62±0.62)% and (22.99±0.69)%, (17.08±0.80)% and (26.00±0.71)%, (19.37±0.57)% and (24.74±0.64)% in high, medium and low dose groups, respectively, vs (23.65±0.56)% and (35.00±0.60)% in control group (P<0.01). The expression of mRNA of VEGF and its receptors was significantly decreased, the area of electrophoresis bands (AREA), the absorptivity of mean optical density (A) and the product of AREA and A were significantly lower in WKN-administered groups than that in control group (P<0.01).
CONCLUSION: The decoction of WKN suppresses the growth of gastric cancer cell MGC-803 and decreases the expression of mRNA of both VEGF and its receptors KDR and Flt-1.