Biomedical subjects

Lorenza Wyder

Publications and source records attributed to Lorenza Wyder.

4 recordsLinked to original sources

PubMed2006

Antagonism of sphingosine-1-phosphate receptors by FTY720 inhibits angiogenesis and tumor vascularization.

FTY720, a potent immunomodulator, becomes phosphorylated in vivo (FTY-P) and interacts with sphingosine-1-phosphate (S1P) receptors. Recent studies showed that FTY-P affects vascular endothelial growth factor (VEGF)-induced vascular permeability, an important aspect of angiogenesis. We show here that FTY720 has antiangiogenic activity, potently abrogating VEGF- and S1P-induced angiogenesis in vivo in growth factor implant and corneal models. FTY720 administration tended to inhibit primary and significantly inhibited metastatic tumor growth in a mouse model of melanoma growth. In combination with a VEGFR tyrosine kinase inhibitor PTK787/ZK222584, FTY720 showed some additional benefit. FTY720 markedly inhibited tumor-associated angiogenesis, and this was accompanied by decreased tumor cell proliferation and increased apoptosis. In transfected HEK293 cells, FTY-P internalized S1P1 receptors, inhibited their recycling to the cell surface, and desensitized S1P receptor function. Both FTY720 and FTY-P apparently failed to impede VEGF-produced increases in mitogen-activated protein kinase activity in human umbilical vascular endothelial cells (HUVEC), and unlike its activity in causing S1PR internalization, FTY-P did not result in a decrease of surface VEGFR2 levels in HUVEC cells. Pretreatment with FTY720 or FTY-P prevented S1P-induced Ca2+ mobilization and migration in vascular endothelial cells. These data show that functional antagonism of vascular S1P receptors by FTY720 potently inhibits angiogenesis; therefore, this may provide a novel therapeutic approach for pathologic conditions with dysregulated angiogenesis.

Animals↗

PubMed2005

The antitumor and antiangiogenic activity of vascular endothelial growth factor receptor inhibition is potentiated by ErbB1 blockade.

PURPOSE: Receptor tyrosine kinases of the ErbB family play important roles in the control of tumor growth. Vascular endothelial growth factor (VEGF) stimulates endothelial cell proliferation, enhances vascular permeability, and plays an important role in tumor vascularization. We evaluated the effects of selective VEGF receptor (VEGFR; PTK787/ZK222584) and ErbB (PKI166 and ZD1839) inhibitors on tumor growth and angiogenesis and asked whether additional therapeutic benefit was conferred by combination treatment. EXPERIMENTAL DESIGN: The antitumor activity of each inhibitor alone or in combination was assessed in human cancer models in immunocompromised mice. ErbB receptor expression and activation of downstream signaling pathway was evaluated in both tumor and endothelial cells. RESULTS: Both ErbB inhibitors significantly enhanced the antitumor activity of PTK787/ZK222584. In vitro, ErbB1 inhibition blocked VEGF release by tumor cells and proliferation of both tumor and endothelial cells. In an in vitro angiogenesis assay, epidermal growth factor (EGF) stimulated the release of VEGF by smooth muscle cells resulting in increased angiogenesis, a response blocked by administration of PTK787/ZK222584. Under basal condition, both ZD1839 and PTK787/ZK222584 blocked sprouting, likely via inhibition of an autocrine ErbB1 loop and VEGFR signaling, respectively, in endothelial cells. In conditions of limiting VEGF, EGF plays an important role in endothelial cell proliferation, survival, and sprouting. CONCLUSION: We have shown that activation of ErbB1 triggers a plethora of effects, including direct effects on tumor and endothelial cells and indirect effects mediated via induction of VEGF release. Simultaneous blockade of ErbB1 and VEGFR pathways results in a cooperative antitumor effect, indicating that this combination may represent a valid therapeutic strategy.

Angiogenesis Inhibitors↗

PubMed2004

Beta3-integrin regulates vascular endothelial growth factor-A-dependent permeability.

OBJECTIVE: Beta3-integrin deficiency has been implicated in increasing levels of Flk-1 expression on endothelial cells and enhancing vascular endothelial growth factor (VEGF)-induced angiogenesis. We determined the role of beta3-integrin in mediating VEGF-A-induced blood vessel permeability through Flk-1. METHODS AND RESULTS: Using the Miles assay, we demonstrated that VEGF-A-induced plasma leakage was enhanced in beta3-null mice when compared with wild-type controls. This was not caused by any changes in blood vessel structure (as detected by light or electron microscopy) or by changes in endothelial cell-cell adhesion proteins (as determined by Western blot analysis, flow cytometry, and immunofluorescence). Circulating levels of VEGF, baseline blood vessel leakage, and leakage in response to an acute inflammatory stimulus were identical in wild-type and beta3-null mice. However, VEGF-A-induced leakage was abolished in beta3-null mice by the inhibition of Flk-1, indicating that the elevated levels of Flk-1 on beta3-null endothelial cells enhance VEGF-A-induced permeability. CONCLUSIONS: beta3-integrin-deficiency increases the sensitivity of endothelial cells to VEGF-A by elevating Flk-1 expression and, as a consequence, enhances VEGF-A-mediated permeability.

Animals↗

PubMed2002

Enhanced pathological angiogenesis in mice lacking beta3 integrin or beta3 and beta5 integrins.

Inhibition of alphavbeta3 or alphavbeta5 integrin function has been reported to suppress neovascularization and tumor growth, suggesting that these integrins are critical modulators of angiogenesis. Here we report that mice lacking beta3 integrins or both beta3 and beta5 integrins not only support tumorigenesis, but have enhanced tumor growth as well. Moreover, the tumors in these integrin-deficient mice display enhanced angiogenesis, strongly suggesting that neither beta3 nor beta5 integrins are essential for neovascularization. We also observed that angiogenic responses to hypoxia and vascular endothelial growth factor (VEGF) are augmented significantly in the absence of beta3 integrins. We found no evidence that the expression or functions of other integrins were altered as a consequence of the beta3 deficiency, but we did observe elevated levels of VEGF receptor-2 (also called Flk-1) in beta3-null endothelial cells. These data indicate that alphavbeta3 and alphavbeta5 integrins are not essential for vascular development or pathological angiogenesis and highlight the need for further evaluation of the mechanisms of action of alphav-integrin antagonists in anti-angiogenic therapeutics.

Animals↗