ABSTRACT
PURPOSE: Vascular endothelial growth factor (VEGF) signal transduction mainly depends on its binding to VEGF receptor 2 (VEGFR-2). VEGF downstream signaling proteins mediate several of its effects in cancer progression, including those on tumor growth, metastasis, and blood vessel formation. The activation of VEGFR-2 signaling is a hallmark of and is considered a therapeutic target for breast cancer. Here, we report a study of the regulation of the VEGFR-2 signaling pathway by a small molecule, isomangiferin. METHODS: A human breast cancer xenograft mouse model was used to investigate the efficacy of isomangiferin in vivo. The inhibitory effect of isomangiferin on breast cancer cells and the underlying mechanism were examined in vitro. RESULTS: Isomangiferin suppressed tumor growth in xenografts. In vitro, isomangiferin treatment inhibited cancer cell proliferation, migration, invasion, and adhesion. The effect of isomangiferin on breast cancer growth was well coordinated with its suppression of angiogenesis. A rat aortic ring assay revealed that isomangiferin significantly inhibited blood vessel formation during VEGF-induced microvessel sprouting. Furthermore, isomangiferin treatment inhibited VEGF-induced proliferation of human umbilical vein endothelial cells and the formation of capillary-like structures. Mechanistically, isomangiferin induced caspase-dependent apoptosis of breast cancer cells. Furthermore, VEGF-induced activation of the VEGFR-2 kinase pathway was down-regulated by isomangiferin. CONCLUSION: Our findings demonstrate that isomangiferin exerts anti-breast cancer effects via the functional inhibition of VEGFR-2. Pharmaceutically targeting VEGFR-2 by isomangiferin could be an effective therapeutic strategy for breast cancer.
Subject(s)
Animals , Humans , Mice , Rats , Angiogenesis Inhibitors , Apoptosis , Blood Vessels , Breast Neoplasms , Cell Proliferation , Heterografts , Human Umbilical Vein Endothelial Cells , In Vitro Techniques , Microvessels , Neoplasm Metastasis , Phosphotransferases , Receptors, Vascular Endothelial Growth Factor , Signal Transduction , Vascular Endothelial Growth Factor A , Vascular Endothelial Growth Factor Receptor-2ABSTRACT
<p><b>OBJECTIVE</b>To investigate the transcriptional regulation of pacemaker channel I(f) mediated by vasoactive peptide endothelin-1 (ET-1) in neonatal rat ventricular myocytes and its mechanism.</p><p><b>METHODS</b>Neonatal rat ventricular myocytes were enzymatically isolated. I(f) current was recorded using the whole-cell patch-clamp technique. The expression of hyperpolarization-activated cyclic nucleotide-gated channel (HCN) isoforms HCN2 and HCN4 were measured by quantitative RT-PCR.</p><p><b>RESULTS</b>ET-1 increased the expression of HCN2 and HCN4 mRNA in a dose- and time-dependent manner. These effects were blocked by specific ETA receptor antagonist BQ-123 but not the ETB receptor antagonist BQ-788. The effects of ET-1 on HCN2 and HCN4 mRNA expression were not affected by the p38 mitogen-activated protein kinase (MAPK) inhibitor (SB-203580).</p><p><b>CONCLUSION</b>These findings indicate that ET-1 stimulates the expression of pacemaker channel I(f) in cardiomyocytes via ETA receptor through a p38 MAPK-independent signaling pathway, which might be linked to the intrinsic arrhythmogenic potential of ET-1.</p>