Melanoma-derived IL-1 converts vascular endothelium to a proinflammatory and procoagulatory phenotype via NFκB activation.

Spreading of melanoma is associated with efficient extravasation of circulating tumor cells from the vascular system into distant target organs. This process is accompanied and supported by proinflammatory and procoagulatory conditions. In this study, we analysed the ability of human melanoma cell lines to activate endothelial cells (ECs) in vitro. Some melanoma cells, that is, MV3, were shown to trigger an prompt calcium-flux-dependent, procoagulatory endothelial response that was accompanied by luminal release of ultra-large von Willebrand factor (ULVWF) fibres that were immobilized to the endothelial surface layer. In contrast to MV3-derived supernatant, prolonged treatment of ECs with WM9-derived supernatant mediated a pronounced activation of nuclear factor kappa B (NFκB). NFκB activation in ECs was dependent on both IL-1α and IL-1ß secreted from melanoma cells. Melanoma-derived IL-1 mediated an upregulation of proinflammatory cytokines IL-6 and IL-8, the intercellular adhesion molecule-1 (ICAM-1), the vascular cell adhesion molecule-1 (VCAM-1) and the procoagulatory tissue factor (TF) in ECs. Our data show that melanoma cells activate ECs either directly and within seconds or by an IL-1-mediated NFκB activation. Both pathways of EC activation convert the regular repressive function of ECs on inflammation and coagulation to a proinflammatory and procoagulatory surface that supports tumor progression.

Highly invasive melanoma cells activate the vascular endothelium via an MMP-2/integrin αvß5-induced secretion of VEGF-A.

Tumor cell extravasation is a critical step in the metastatic cascade and requires interaction between the tumor cell and the endothelium. Although cancer progression depends on a complex network of mechanisms, including inflammation and coagulation, the involvement of tumor-induced endothelium activation and the subsequent release of procoagulatory factors in this process are not well understood. Using tissue sections from patients with malignant melanoma, immunofluorescence studies for the presence of von Willebrand factor (VWF) clearly demonstrated endothelium activation and the formation of ultra-large VWF fibers in these patients. In vitro analyses revealed that supernatants from highly invasive melanoma cells induced an acute endothelium activation measured by VWF, P-selectin, and angiopoietin-2 release. Proteome profiling identified vascular endothelial growth factor A (VEGF-A) as the main mediator of endothelium activation. Inhibition and knock-down of VEGF-A in melanoma cells led to a rigorous decrease in VWF exocytosis. Selective small-interfering RNA to matrix metalloproteinase-2 (MMP-2) inhibited endothelium activation, and this effect correlated with reduced VEGF-A content in the supernatants of melanoma cells. Further experiments showed that active MMP-2 regulates VEGF-A in melanoma cells on a transcriptional level via an integrin αvß5/phosphoinositide-3-kinase-dependent pathway. In conclusion, these results indicate an important role of VEGF-A in acute endothelium activation and provide clear evidence that MMP-2 plays a pivotal role in the autocrine regulation of VEGF-A expression in melanoma cells.

Cytotoxicity of silica nanoparticles through exocytosis of von Willebrand factor and necrotic cell death in primary human endothelial cells.

Nanoparticle-induced endothelial cell (EC) dysfunction, due to the induction of inflammation and/or the activation of the coagulation system, is associated with pulmonary and ischemic cardiovascular diseases. Although it is contigent on several mechanisms, involving formation of reactive oxygen species and inflammatory cytokines such as interleukin (IL)-6 and 8, the involvement of the coagulation system is not well understood. The results of toxicity assays using the tetrazolium reduction (MTT) and lactate dehydrogenase (LDH) release showed that silica NP-induced cytotoxicity depends on the size and the dose of applied NP. Moreover, propidium iodide (PI) stainings and caspase 3/7 assays identified increased necrosis in ECs. Exposing human umbilical vein endothelial cells (HUVECs) to SiO(2) NP with diameters of 304 nm and 310 nm led to significant increase of Weibel-Palade body (WPB) exocytosis, associated with the release of von Willebrand factor (VWF) and the formation of ultralarge fibers (ULVWF). High resolution microscopy techniques revealed that internalization and perinuclear localization of perylene-labeled NP with a size of 310 nm affect not only viability, but also cell migration and proliferation. In conclusion, our data indicate that NP-induced activation and dysfunction of ECs is reflected by release of VWF and necrotic cell death.

The mechanism of melanoma-associated thrombin activity and von Willebrand factor release from endothelial cells.

Activation of the coagulation system in malignancy enables tumor spreading and is thus associated with poor prognosis for the patient. In this study, we analyzed the in vitro mechanisms by which two human metastatic melanoma cell lines, MV3 and WM9, transform the vascular endothelium into a prothrombotic activated state. We show that both melanoma cell lines activate prothrombin due to tissue factor (TF) expression by showing that thrombin generation was blocked with a TF-neutralizing antibody and TF-siRNA. In addition, using the cysteine protease inhibitor E-64, we excluded the formerly described cancer procoagulant (CP) as a major factor contributing to thrombin generation. Furthermore, we describe a direct thrombin-independent response of endothelial cells (ECs) to MV3-derived supernatant as measured by rapid release of VWF. We also show that two clinically approved LMWHs, tinzaparin and enoxaparin, are effective inhibitors of thrombin generation and thrombin activity in plasma. Furthermore, our data indicate a protective effect of heparins on EC activation as shown by reduced VWF release in response to MV3 supernatant. These promising effects of heparins on the melanoma-induced thrombotic conditions justify further clinical investigations in the field of oncology.