Antiangiogenic agents targeting different angiogenic pathways have opposite effects on tumor hypoxia in R-18 human melanoma xenografts.

BACKGROUND: Studies comparing the effect of antiangiogenic agents targeting different angiogenic pathways are sparse. The purpose of this study was to compare the effect of properdistatin and sunitinib treatment in a preclinical model of malignant melanoma. Properdistatin is a small peptide derived from the thrombospondin-1 domain of the plasma protein properdin, and sunitinib is a tyrosine kinase inhibitor targeting several receptors including the vascular endothelial growth factor receptors. METHODS: R-18 human melanoma xenografts growing in dorsal window chambers were treated with properdistatin, sunitinib, or vehicle. Parameters describing the morphology of tumor vasculature were assessed from high-resolution transillumination images, and BST (blood supply time; the time needed for arterial blood to flow from the main supplying artery to downstream microvessels) was assessed from first-pass imaging movies recorded after a bolus of fluorescence-labeled dextran had been administered intravenously. Tumor hypoxia was assessed from immunohistochemical preparations of the imaged tissue by using pimonidazole as a hypoxia marker. RESULTS: Properdistatin treatment selectively removed small-diameter vessels and reduced BST, whereas sunitinib treatment reduced the density of small- and large-diameter vessel similarly and did not change BST. These observations imply that properdistatin treatment reduced geometric resistance to blood flow and improved vascular function, whereas sunitinib treatment did not affect vascular function. Accordingly, sunitinib-treated tumors showed higher hypoxic fractions than properdistatin-treated tumors. CONCLUSIONS: Properdistatin and sunitinib both inhibited angiogenesis, but had distinctly different effects on vascular morphology, vascular function, and extent of hypoxia in R-18 human melanoma xenografts.

Spatholobi Caulis extracts promote angiogenesis in HUVECs in vitro and in zebrafish embryos in vivo via up-regulation of VEGFRs.

ETHNOPHARMACOLOGICAL RELEVANCE: Spatholobi Caulis is a traditional blood-activating and stasis-dispelling herb medicine, which has been used to treat diseases related to blood stasis syndrome (BSS) by inhibiting platelet aggregation, stimulate hematopoiesis, etc. It has been demonstrated that pro-angiogenesis could improve BSS. However, the pro-angiogenic activity of Spatholobi Caulis was not well elucidated AIM OF STUDY: To determine the potential pro-angiogenic activity of Spatholobi Caulis and elucidate its underlying mechanism. The active fractions of Spatholobi Caulis were further screened. MATERIAL AND METHODS: Gelatin precipitation and reversed-phase liquid chromatography (RPLC) were used to purify the methanol extracts of Spatholobi Caulis, respectively. The RPLC was also used to prepare fractions. Total flavonoids of purified methanol extracts of Spatholobi Caulis (PSC) were determined using ultraviolet spectrophotometry. The morphological observation of subintestinal vessel plexus (SIVs) and tyrosine kinase inhibitor II (VRI)-induced intersegmental blood vessels (ISVs) loss in transgenic zebrafish Tg(fli-1a: EGFP)y1 were selected to evaluate the pro-angiogenic activity of PSC in vivo. Cell proliferation by MTT assay and cell migration assay were used to evaluate the pro-angiogenesis effect of PSC in human umbilical vein endothelial cells (HUVECs) in vitro. Both zebrafish and HUVECs were used in screening active fractions of PSC. The mechanism of PSC promoting angiogenesis were studied by real-time PCR in zebrafish and western blotting in HUVECs. RESULTS: Co-treatment PSC dramatically rescued VRI-induced ISVs loss in zebrafish embryos in a dose-dependent manner and 80% of the defective vascular recovered at the concentration of 30µg/ml compared with VRI-only group. PSC also concentration-dependently increased average sprouting number and diameter of SIVs in zebrafish embryo. Real-time PCR assay proved that PSC significantly restored the down regulation of VEGFRs including Flt-1, Kdr and Kdrl induced by VRI in zebrafish (P<0.001). Furthermore, PSC not only promoted proliferation and migration of normal HUVECs but also ameliorated VRI-induced HUVECs cytotoxicity. Western blotting assay showed that co-treatment of PSC increased the expression of VEGFRs and phosphorylation of MAPKs which decreased by VRI treatment. In addition, quality evaluation experiments showed that the content of total flavonoids of PSC reached 56.36% and the main pro-angiogenic fractions of PSC were F3, F4 and F5 both in zebrafish and HUVECs. CONCLUSIONS: Our data demonstrated that PSC presented pro-angiogenic activity both in zebrafish and HUVECs, and principal pro-angiogenic active components were likely flavonoids. Thus, the current study provided evidence for the clinical usage of Spatholobi Caulis in promoting blood circulation and removing stasis in traditional Chinese medicine (TCM).

Targeted therapy in renal cell carcinoma.

PURPOSE OF REVIEW: A better understanding of renal cell carcinoma biology has led to a new era of targeted therapy in the management of metastatic renal cell carcinoma. RECENT FINDINGS: New phase II and phase III clinical data on both Food and Drug Administration approved and investigational targeted agents are now available, widening the choice of therapies in the treatment of metastatic renal cell carcinoma. SUMMARY: We provide a review of the data to facilitate effective evidence-based clinical practice and also aim to give a perspective for future clinical and translational research in renal cell carcinoma.

In vitro antiangiogenic activity of selective somatostatin subtype-1 receptor agonists.

BACKGROUND: Endothelial cells of human blood vessels (arteries and veins) show high levels of somatostatin subtype-1 receptor (sst(1)). The aim of the present study is to investigate the inhibitory effects of novel somatostatin analogs, highly selective for human sst(1), on in vitro angiogenesis and their modulation of vascular endothelial growth factor (VEGF) and vascular endothelial growth factor receptor-2 (VEGFR-2) expression. MATERIALS AND METHODS: Somatostatin analogs BIM-23745 and BIM-23926 were tested for their ability to prevent proliferation and migration of human endothelial HMEC-1 cells, to modulate VEGF and VEGFR-2 expression and to inhibit sprouting of microvessels from cultured human placental vessel explants in fibrin matrix for 28 days. RESULTS: The somatostatin sst(1 )receptor-selective agonists, BIM-23745 and BIM-23926 showed a suppression of endothelial proliferation (e.g. 10(-6) M BIM-23475, 40.0 +/- 2.1% vs. 100% of controls; 10(-7) M BIM-23926, 55.3 +/- 3.3% vs. 100% of controls), migration (e.g. 10(-7) M BIM-23475, 35.0 +/- 1.56% vs. 100% of controls; 10(-7) M BIM-23926, 53.7 +/- 1.77% vs. 100% of controls) and microvessel sprouting (e.g. 10(-8) M BIM-23475, 42.8 +/- 5.6% vs. 100% of controls; 10(-7) M BIM-23926, 17.2 +/- 11.8% vs. 100% of controls). A small but significant percentage of cells exposed to BIM-23745 and BIM-23926 for 24 h and for 72 h presented typical apoptotic morphology. Moreover, both the analogs significantly inhibit VEGF and VEGFR-2 gene expression in endothelial cells grown for 144 h in a fibrin matrix and the VEGF secretion in conditioned media. CONCLUSIONS: The inhibition of endothelial activities suggests potential therapeutic utility for administration of somatostatin sst(1 )receptor-selective agonists in the proliferative diseases involving angiogenesis.