Anti-angiogenic effects of Siegesbeckia glabrescens are mediated by suppression of the Akt and p70S6K-dependent signaling pathways.

Siegesbeckia glabrescens (SG) Makino (Compositae) has been used as a traditional medicine for the treatment of allergic and inflammatory diseases. In the present study, we report the effects and molecular mechanism of an ethanolic extract of SG on cell proliferation, migration and tube formation in vascular endothelial growth factor-A (VEGF-A)-treated human umbilical vein endothelial cells. SG treatment inhibited VEGF-A-stimulated endothelial cell proliferation through downregulation of cyclin D and upregulation of cyclin-dependent kinase inhibitors such as p27Kip1 and p21WAF1/Cip1.

Regulatory effects of Siegesbeckia glabrescens on non-small cell lung cancer cell proliferation and invasion.

Siegesbeckia glabrescens (SG) Makino (Compositae) has been used as a traditional medicine for the treatment of allergic and inflammatory diseases. In the present study, we examined the effects and molecular mechanism of the ethanol extract of SG on cell proliferation and invasion in p53 wild-type A549 and p53-deficient H1299 non-small cell lung cancer (NSCLC) cells. SG treatment markedly inhibited the proliferation and invasion in both cell lines, independently of p53 expression.

The in vitro antitumor activity of Siegesbeckia glabrescens against ovarian cancer through suppression of receptor tyrosine kinase expression and the signaling pathways.

Siegesbeckia glabrescens (SG) Makino (Compositae) has been used as a traditional medicine for the treatment of a variety of diseases such as allergy, inflammation, acute hepatitis and hypertension. The primary aim of this study was to determine whether the ethanol extract of SG has antitumor activity against ovarian cancer and to identify molecular mechanisms and targets involved in the regulation of cell growth and progression. We demonstrate that SG treatment inhibits proliferation, adhesion, migration and invasion of SKOV-3 human ovarian cancer cells.

Inhibitory effects of sepiapterin on vascular endothelial growth factor-A-induced proliferation and adhesion in human umbilical vein endothelial cells.

Tetrahydrobiopterin (BH(4)) has been known to be an essential cofactor for the activities of nitric oxide (NO) synthase and aromatic amino acid hydroxylases, which are involved in physiological and pathological processes. In the present study, we report that sepiapterin, the more stable form of BH4 precursor, modulates vascular endothelial growth factor-A (VEGF-A)-induced cell proliferation and adhesion in human umbilical vein endothelial cells (HUVECs). The antiproliferative activity of sepiapterin in VEGF-A-treated HUVECs is associated with inhibition of the expression of cyclin-dependent kinases (Cdks) such as Cdk4 and Cdk2.

Sepiapterin inhibits cell proliferation and migration of ovarian cancer cells via down-regulation of p70S6K-dependent VEGFR-2 expression.

Tetrahydrobiopterin (BH4) is known to be an essential cofactor for the aromatic amino acid hydroxylases, which are involved in the production of neurotransmitters, and for nitric oxide (NO) synthase. In the present study, we report that sepiapterin, the more stable form of the BH4 precursor, modulates ovarian cancer cell proliferation and migration by NO-dependent and -independent mechanisms. Sepiapterin induction of cell proliferation and migration in SKOV-3 cells is accompanied by ERK, Akt and p70S6K activation.

Indirect oxidation of 6-tetrahydrobiopterin by tyrosinase.

6-Tetrahydrobiopterin is known to bind to an allosteric site of tyrosinase to directly inhibit the enzyme. However, simultaneous measurements of ultraviolet-visible absorption spectra and oxygen consumption led us to conclude that the inhibition was due to oxidation of 6-tetrahydrobiopterin by dopaquinone. Immediately after addition of 6-tetrahydrobiopterin, tyrosinase stopped producing dopachrome from either tyrosine or dopa.