Xiaoli Zhang

Acetyl-11-Keto-β-Boswellic Acid Inhibits Prostate Tumor Growth by Suppressing Vascular Endothelial Growth Factor Receptor 2-Mediated Angiogenesis

The role of angiogenesis in tumor growth and metastasis is well established. Identification of a small molecule that blocks tumor angiogenesis and is safe and affordable has been a challenge in drug development. In this study, we showed that acetyl-11-keto-beta-boswellic acid (AKBA), an active component from an Ayurvedic medicinal plant (Boswellia serrata), could strongly inhibit tumor angiogenesis. AKBA suppressed tumor growth in the human prostate tumor xenograft mice treated daily (10 mg/kg AKBA) after solid tumors reached approximately 100 mm(3) (n = 5). The inhibitory effect of AKBA on tumor growth was well correlated with suppression of angiogenesis. When examined for the molecular mechanism, we found that AKBA significantly inhibited blood vessel formation in the Matrigel plug assay in mice and effectively suppressed vascular endothelial growth factor (VEGF)-induced microvessel sprouting in rat aortic ring assay ex vivo. Furthermore, AKBA inhibited VEGF-induced cell proliferation, chemotactic motility, and the formation of capillary-like structures from primary cultured human umbilical vascular endothelial cells in a dose-dependent manner. Western blot analysis and in vitro kinase assay revealed that AKBA suppressed VEGF-induced phosphorylation of VEGF receptor 2 (VEGFR2) kinase (KDR/Flk-1) with IC(50) of 1.68 micromol/L. Specifically, AKBA suppressed the downstream protein kinases of VEGFR2, including Src family kinase, focal adhesion kinase, extracellular signal-related kinase, AKT, mammalian target of rapamycin, and ribosomal protein S6 kinase. Our findings suggest that AKBA potently inhibits human prostate tumor growth through inhibition of angiogenesis induced by VEGFR2 signaling pathways.

Cucurbitacin E, a tetracyclic triterpenes compound from Chinese medicine, inhibits tumor angiogenesis through VEGFR2-mediated Jak2-STAT3 signaling pathway.

Cucurbitacin E (CuE, α-elaterin), a tetracyclic triterpenes compound from folk traditional Chinese medicine plants, has been shown to inhibit cancer cell growth, inflammatory response and bilirubin-albumin binding. However, the effects of CuE on tumor angiogenesis and its potential molecular mechanism are still unknown. Here, we demonstrated that CuE significantly inhibited human umbilical vascular endothelial cell (HUVEC) proliferation, migration and tubulogenesis in vitro and blocked angiogenesis in chick embryo chorioallantoic membrane assay and mouse corneal angiogenesis model in vivo. Furthermore, we found that CuE remarkably induced HUVEC apoptosis, inhibited tumor angiogenesis and suppressed human prostate tumor growth in xenograft tumor model. Finally, we showed that CuE blocked vascular endothelial growth factor receptor (VEGFR) 2-mediated Janus kinase (Jak) 2-signal transducer and activator of transcription (STAT) 3 signaling pathway in endothelial cells and suppressed the downstream protein kinases, such as extracellular signal-regulated kinase and p38 mitogen-activated protein kinases. Therefore, our studies provided the first evidence that CuE inhibited tumor angiogenesis by inhibiting VEGFR2-mediated Jak-STAT3 and mitogen-activated protein kinases signaling pathways and CuE is a potential candidate in angiogenesis-related disease therapy.

Indirubin inhibits tumor growth by antitumor angiogenesis via blocking VEGFR2‐mediated JAK/STAT3 signaling in endothelial cell

Tumor angiogenesis is one of the hallmarks of the development in malignant neoplasias and metastasis. Many angiogenesis inhibitors are small molecules from natural products. Indirubin, the active component of a traditional Chinese herbal medicine, Banlangen, has been shown to exhibit antitumor and anti‐inflammation effects. But its roles in tumor angiogenesis, the key step involved in tumor growth and metastasis, and the involved molecular mechanism is unknown. Here, we identified that indirubin inhibited prostate tumor growth through inhibiting tumor angiogenesis. Using chick chorioallantoic membrane (CAM) assay and mouse corneal model, we found that indirubin inhibited angiogenesis in vivo. We also showed the inhibition activity of indirubin in endothelial cell migration, tube formation and cell survival in vitro. Furthermore, indirubin suppressed vascular endothelial growth factor receptor 2‐mediated Janus kinase (JAK)/STAT3 signaling pathway but had little effects on the activity of extracellular signal‐regulated kinase (ERK) and p38 mitogen‐activated protein kinase in endothelial cell. Our study provided the first evidence for antitumor angiogenesis activity of indirubin and the related molecular mechanism. Our investigations suggested that indirubin was a potential drug candidate for angiogenesis related diseases.