Jens Gille

Endothelial P-Selectin as a Target of Heparin Action in Experimental Melanoma Lung Metastasis

Spontaneous and experimental metastasis can be effectively inhibited by the widely used anticoagulant heparin in different tumor models. At the cellular level, many of the antimetastatic effects of heparin in vivo are due to its action on P-selectin-mediated binding. Whereas previous attention has focused on P-selectin-dependent tumor-cell-platelet interactions in blood-borne metastasis, we sought to address the potential contribution of endothelial P-selectin expression to adhesive events between the microvasculature and melanoma cells in vivo. Transplantation of bone marrow from P-selectin-deficient into wild-type mice conveyed inhibition of ex-perimental melanoma metastasis. However, the extent to which bone marrow-conferred lack of platelet P-selectin expression attenuated melanoma lung metastasis was significantly less than that seen in P-selectin-deficient mice, suggesting that endothelial P-selectin expression may additionally contribute to formation of hematogenous metastases. This assumption was supported by our intravital microscopy studies, in which a significant proportion of melanoma cells were capable of directly interacting with postcapillary venules of the murine ear in a P-selectin-dependent manner. Heparin not only inhibits P-selectin-mediated melanoma cell rolling but also attenuates melanoma metastasis formation in vivo, further supporting the concept that endothelial P-selectin expression may represent an additional target of heparin action in experimental melanoma lung metastasis.

Increased Sp1 phosphorylation as a mechanism of hepatocyte growth factor (HGF/SF)-induced vascular endothelial growth factor (VEGF/VPF) transcription

Hepatocyte growth factor (HGF/SF)-induced expression of vascular endothelial growth factor (VEGF/VPF) has been implicated in paracrine amplification of angiogenesis, contributing to angiogenic responses during inflammation, wound healing, collateral formation and tumor growth. We have shown previously that HGF/SF-mediated VEGF/VPF expression by keratinocytes is primarily dependent on transcriptional activation, and we mapped the HGF/SF-responsive element to a GC-rich region between bp -88 and -65. Sp1-like factors bind to this element constitutively; however the VEGF/VPF promoter is transactivated by HGF/SF in the absence of induced binding activity. In experimental approaches to clarify molecular mechanisms of Sp1-dependent VEGF/VPF gene transcription, neither HGF/SF-dependent changes in nuclear expression nor in relative DNA binding activity of Sp family members to the indicated element were observed. Thus, HGF/SF was hypothesized to induce VEGF/VPF gene transcription via increased transactivation activity of Sp1 owing to biochemical modification. In immunoprecipitation studies, HGF/SF was found to increase the amount of serine-phosphorylated Sp1, revealing a likely mechanism of HGF/SF-induced VEGF/VPF expression, as phosphorylation may enhance the transcriptional activity of Sp1. The contribution of different signaling molecules to HGF/SF-induced VEGF/VPF transcription was demonstrated by the use of chemical inhibition, of expression of kinase-deficient signaling proteins, and by the use of antisense oligonucleotides. Herein, we provide evidence that PI 3-kinase, MEK1/2 and PKC-ζ play a significant role in HGF/SF-induced VEGF/VPF promoter activation. Together, our results elucidate a critical pathway of paracrine amplification of angiogenesis, suggesting that HGF/SF-induced Sp1 phosphorylation may activate VEGF/VPF promoter activity that requires the contribution of distinct signaling molecules.

PPARα Activators Inhibit Vascular Endothelial Growth Factor Receptor-2 Expression by Repressing Sp1-Dependent DNA Binding and Transactivation

Abstract— Peroxisome proliferator–activated receptors (PPARs) are ligand-activated transcription factors, originally implicated in the regulation of lipid and glucose homeostasis. In addition, natural and synthetic PPAR activators may control inflammatory processes by inhibition of distinct proinflammatory genes. As signaling via the vascular endothelial growth factor receptor-2 (VEGFR2) pathway is critical for angiogenic responses during chronic inflammation, we explored whether known antiinflammatory effects of PPAR ligands are mediated in part through diminished VEGFR2 expression. In this study, PPAR&agr; agonists are found to inhibit endothelial VEGFR2 expression, whereas predominant PPAR&ggr; ligands remained without discernible effects. Time- and concentration-dependent inhibition is demonstrated both at the level of protein and mRNA VEGFR2 expression. Inhibitory effects of PPAR&agr; agonists on transcriptional activity of the VEGFR2 promoter are conveyed by an element located between base pairs −60 and −37 that contains two adjacent consensus Sp1 transcription factor binding sites. Constitutive Sp1-containing complex formation to this sequence is decreased by PPAR&agr; treatment, indicating that VEGFR2 gene expression is inhibited by repressing Sp1 site-dependent DNA binding and transactivation. Our coimmunoprecipitation experiments revealed enhanced protein interactions between PPAR&agr; and Sp1 on PPAR&agr; activation, thus constituting a probable mechanism by which PPAR&agr; activators decrease Sp-dependent binding activity to the VEGFR2 promoter. Hence, molecular mechanisms by which PPARs modulate the rate of gene transcription may include direct interactions between specific transcription factors and PPARs that ultimately result in reduced DNA binding to their respective response elements.

The ability of different forms of heparins to suppress P-selectin function in vitro correlates to their inhibitory capacity on bloodborne metastasis in vivo

Ample evidence suggests that many of the in vivo anti-metastatic effects by heparins reflect their actions on P-selectin-mediated binding. We hypothesized that the ability of widely used heparins and derivatives to interfere with P-selectin-dependent tumour cell interactions under flow in vitro could be used to identify anticoagulants with advanced inhibitory functions on experimental blood-borne metastasis in vivo. To test this assumption, the impact of unfractionated heparin, the low-molecular-weight heparins (LMWH) nadroparin and enoxaparin, and the synthetic pentasaccharide fondaparinux on P-selectin-dependent tumour interactions in vitro and metastasis formation in vivo were evaluated. Our data revealed that these commonly used anticoagulants widely differ in their potential to interfere with P-selectinmediated cell binding. Importantly, the superior inhibitory capacity on P-selectin function of unfractionated heparin and LMWH nadroparin as opposed to LMWH enoxaparin and synthetic heparin pentasaccharide fondaparinux strongly correlated to the inhibitory potency of each in inhibiting experimental lung metastasis in vivo. Hence, P-selectin inhibition may constitute a valuable feature to identify anticoagulants that are suitable for anticancer therapy.

Fluid shear stress‐induced transcriptional activation of the vascular endothelial growth factor receptor‐2 gene requires Sp1‐dependent DNA binding

Hemodynamic forces play a fundamental role in the regulation of endothelial cell survival. As signaling via the vascular endothelial growth factor (VEGF) receptor‐2 pathway has been previously demonstrated to impact endothelial cell survival, we hypothesized that laminar shear stress may facilitate survival in part by inducing VEGF receptor‐2 expression. This study shows a time‐ and dose‐dependent upregulation of endothelial VEGF receptor‐2 expression by fluid shear stress in microvascular and large‐vessel derived endothelial cells. A functional analysis of the 5′‐regulatory region of the VEGF receptor‐2 promoter localized the shear stress‐response element to a sequence between bp −60 and −37 that encompasses two adjacent consensus Sp1 transcription factor binding sites. Constitutive and shear stress‐inducible Sp1‐dependent complexes are bound to this element, indicating that fluid shear stress‐induced transcriptional activation of the VEGF receptor‐2 gene requires Sp1‐dependent DNA binding. Together, these results suggest that biomechanical stimulation may lead to endothelial cell survival by upregulating VEGF receptor‐2 expression.

Suppression of VEGFR2 expression in human endothelial cells by dimethylfumarate treatment: evidence for anti-angiogenic action.

The association between angiogenesis and chronic inflammatory diseases, such as psoriasis, seems to be an important phenomenon implicated in the pathogenesis of these medical conditions. Recent studies provide evidence that dimethylfumarate (DMF) has a profound anti-inflammatory as well as anti-tumorigenic action, although the effect of DMF on angiogenesis is unknown. Signaling via the vascular endothelial growth factor receptor-2 (VEGFR2) pathway is critical for angiogenic responses. Therefore, we explored whether the known anti-inflammatory and anti-tumorigenic properties of DMF might be mediated in part by anti-angiogenic effects through the reduction in VEGFR2 expression. In this study, DMF was found to inhibit endothelial VEGFR2 expression; time- and concentration-dependent inhibition was demonstrated both at the level of protein and mRNA expression. This blockade was coincident with the inhibition of the formation of capillary-like structures. The DMF-dependent inhibition of VEGFR2 transcription was found to be mediated by an element located between base pairs -60 and -37, which contains two adjacent, consensus Sp1 transcription factor-binding sites, and the constitutive formation of complexes containing Sp1 at this site is decreased by DMF treatment. Inhibition of VEGFR-2 is shown to be one critical aspect in DMF-mediated anti-angiogenic effects.

Sodium thiosulphate as a promising therapeutic option to treat calciphylaxis

A 35-year-old haemodialysis-dependent woman with chronic renal failure developed large, very painful necrotic ulcers and necrosis on the thighs, buttocks and the abdomen with signs of fast progression. The skin biopsy specimens showed a broad necrosis of the epidermis and thrombosed dermal vessels with focal calcium deposits within the wall. In addi tion, laboratory findings presented an increased product of serum calcium and phosphate concentrations. Thus, we diagnosed calciphylaxis on the basis of clinical, biochemical and histopathological criteria. We initiated a therapy in which our patient was treated with intravenous sodium thiosulphate 3 times weekly. Already after 2 weeks of treatment, no new lesions were detectable and there was a dramatic pain relief. In the following 4 weeks, a successive decline of the ulcers and the healing of individual tissue defects could be seen. Four months after the start of the therapy, the patient underwent successful renal transplantation. Thus, the intravenous therapy of calciphylaxis with sodium thiosulphate might be a new effective alternative in the treatment of this life-threatening disease.

Antiangiogenic cancer therapies get their act together: current developments and future prospects of growth factor‐ and growth factor receptor‐targeted approaches

Abstract:  Targeting the vascular endothelial growth factor (VEGF) in combination with standard chemotherapy has recently proved successful in the treatment of different types of advanced cancer. The achievements of combinatorial anti‐VEGF monoclonal antibody bevacizumab (BEV) renewed the confidence in targeted antiangiogenic approaches to constitute a complementary therapeutic modality in addition to surgery, radiotherapy and chemotherapy. While several second‐generation multitargeted tyrosine kinase inhibitors show promise in defined tumor entities, these novel antiangiogenic compounds have yet to meet or exceed the efficacy of combinatorial BEV therapy in ongoing clinical trials. Current developments of targeted antiangiogenic agents include their use in the adjuvant setting and the combination of different antiangiogenesis inhibitors to take a more comprehensive approach in blocking tumor angiogenesis. The identification of surrogate markers that can monitor the activity and efficacy of antiangiogenic drugs in patients belongs to the most critical challenges to exploit the full potential of antiangiogenic therapies. The opportunities and obstacles in further development of growth factor‐ and growth factor receptor‐targeted antiangiogenic approaches for advanced cancer, including malignant melanoma, will be discussed herein with particular reference to selected ongoing clinical trials.

Metronomic low‐dose chemotherapy as antiangiogenic therapeutic strategy for cancer

New blood vessel formation is essential for the growth and metastasis of many cancers. As a result, antitumor activities of various angiogenesis inhibitors have been intensely explored in various tumors. Recent preclinical studies suggest that certain conventional cytotoxic agents can function as antiangiogenic drugs when administered at comparatively low doses on a continuous or very frequent schedule. Such antiangiogenic ‘metronomic’ scheduling of chemotherapy without extended rest periods has been shown to exert significant therapeutic antitumor efficacy with very limited toxicity in different tumor models. Combining metronomic low‐dose chemotherapy regimens with specific angiogenesis inhibitors further increases efficacy. Based on the promising preclinical studies, it is anticipated that metronomic chemotherapy in combination with angiogenesis inhibitors will prove effective in clinical trials in terms of survival prolongation. While considerable progress may derive from larger randomized clinical studies, only joint efforts between basic and clinical research will ultimately advance the new paradigm of long‐term metronomic antiangiogenic chemotherapy, which carries the prospect of turning cancer into a more controllable chronic disease at minimal toxicity.

Intralesional Methotrexate as Effective Treatment in Solitary Giant Keratoacanthoma of the Lower Lip

When size and location of a keratoacanthoma along with patient-related factors argue against surgical treatment, intralesional methotrexate shows to be an effective, easy and inexpensive alternative. The case report presented validates this treatment modality.