Claudia Gottstein

Soluble Tissue Factor Induces Coagulation on Tumor Endothelial Cells In Vivo if Coadministered With Low-Dose Lipopolysaccharides

Objective—This study was performed to evaluate the mechanisms leading to tumor vessel occlusion by tissue factor–based drugs, which are used in vascular targeting approaches for the treatment of malignant tumors. Methods and Results—The effects of nontargeted soluble tissue factor were evaluated in vitro and in vivo. Tumor-bearing mice were treated with (1) the extracellular portion of tissue factor (soluble tissue factor), (2) low nontoxic doses of lipopolysaccharides, or (3) a combination thereof. The combination treatment showed the best effects and resulted in selective thrombosis of tumor vessels. On the basis of our data from subsequent in vitro analyses, including surface plasmon resonance measurements and endothelial cell based coagulation assays, we propose a model on how soluble tissue factor, although lacking its membrane anchor, can promote selective tumor vessel occlusion. Conclusions—To our knowledge, this is the first report to describe the molecular mechanisms of coagulation induction by untargeted soluble tissue factor in vivo. Combination treatments including soluble tissue factor might represent an alternative vascular targeting approach for the treatment of malignant tumors.

Experimental Treatment of Human Hodgkin's Disease with Ricin A-Chain Immunotoxins

In the present paper we describe the evaluation of ricin A-chain immunotoxins for clinical application in Hodgkins disease. The immunotoxins were constructed by chemically linking deglycosylated ricin-A to monoclonal antibodies (MoAb) recognising lymphocyte activation markers CD25, CD30, or IRac, which are expressed by Hodgkins and Reed-Sternberg (H-RS) cells. The cytotoxic effects of the immunotoxins were investigated in vitro against L540Cy Hodgkin cells and in vivo against Hodgkins tumors in nude mice and disseminated Hodgkins tumors in SCID mice. MoAbs were evaluated for crossreactivity with normal human tissues and staining of sections from Hodgkins disease tissue. Of 32 MoAbs, eight showed little crossreactivity with vital human organs and produced highly active immunotoxins. The most effective immunotoxin, RFT5 gamma l.dgA (CD25), inhibits the growth of H-RS cells at concentrations of 7 x 10(-12) M. RFT5 gamma l.dgA destroys about 60% of solid Hodgkins tumors of 0.5 cm diameter in nude mice and induces complete remissions in 95% of SCID mice with disseminated Hodgkins tumors when administered one day after tumor challenge. This immunotoxin binds to all H-RS cells in more than 90% of patients with Hodgkins disease. Patients with refractory Hodgkins disease are currently being treated in a phase-I/II clinical trial.

Systemic coagulation parameters in mice after treatment with vascular targeting agents

BackgroundVascular targeting of malignant tumors has become a clinically validated new treatment approach with clear patient benefit. However clinical studies have also revealed that some types of vascular targeting agents (VTAs) are prone to coagulation system side effects. It is therefore essential to predetermine coagulation parameters in preclinical studies. As of to date, this has rarely been done, predominantly due to technical issues.The goal of this study was to establish and apply a standardized process, whereby systemic coagulation activation can be routinely measured in mice.ResultsWe have evaluated a number of sampling techniques and coagulation tests regarding their suitability for this purpose. We were able to adapt two assays measuring soluble fibrin, a marker for a prethrombotic status. Thus, soluble fibrin could be measured for the first time in mice. All assays were validated in a positive control model for systemic coagulation activation, i.e. lipopolysaccharide-induced endotoxemia.Based on our results, we selected a panel of coagulation tests, which are both feasable and informative for preclinical testing of VTAs: soluble fibrin, thrombin-antithrombin complexes, free antithrombin III, white blood cell counts and platelet counts. The effect of tumor transplants on coagulation parameters was evaluated using this panel. We then applied this set of assays in treatment studies with a VTA developed in our laboratory to investigate a potential systemic coagulation activation.ConclusionWe have established a standardized panel of assays that can be used to test murine blood samples for coagulation activation in preclinical studies. All tests are feasible to perform in any research laboratory without specialized equipment. In addition, this is the first report to measure soluble fibrin, an early marker of systemic coagulation activation, in mice. The panel was applied on tumor bearing mice and mice treated with a VTA. We suggest its general application for coagulation activation analyses in mice.

Antiangiogenese: ein neuer Ansatz in der Tumortherapie?

Zusammenfassung□ HintergrundIntensive Forschungen und zahlreiche Neuerungen auf dem Gebiet konventioneller antineoplastischer Substanzen in den vergangenen Jahren konnten die Gesamtsterblichkeit durch metastasierte solid Tumoren nur gering oder gar nicht vermindern. In den letzten Jahren setzte sich die Ansicht durch, daß Angiogenese eine notwendige Voraussetzung für das Wachstum solider Tumoren ist. Inhibitoren der Tumorangiogenese sind daher eine neue Klasse antineoplastischer Substanzen, die aufgrund ihres neuartigen Wirkmechanismus zumindest theoretisch eine wirkungsvolle Ergänzung zu den konventionellen Zytostatika darstellt.□ Substanzen und klinische StudienEs werden Inhibitoren der Tumorangiogenese vorgestellt, die bereits in klinischen Studien getestet werden und deren Ergebnisse bis Dezember 1998 veröffentlicht wurden. Größtenteils handelt es sich dabei um klinische Phase-I-oder Phase-II-Studien. Die Ergebnisse werden in bezug auf Toxizität und Ansprechen untersucht und miteinander verglichen. Auch einige Substanzen mit hohem therapeutischen Potential, die sich noch in der präklinischen Testung befinden, werden vorgestellt.□ ErgebnisseViele der untersuchten Angiogeneseinhibitoren zeigten eine Antitumorwirksamkeit in Phase-I-oder-II-Studien. Meist handelte es sich um Krankheitsstabilisierungen, seltener um partielle Remissionen. In wenigen Fällen wurden komplette Remissionen gesehen. Die Toxizitäten der verschiedenen Substanzen unterscheiden sich deutlich sowohl in der Art als auch in der Stärke der Nebenwirkungen.□ SchlußfolgerungEinige antiangiogene Substanzen scheinen vielversprechend für einen Einsatz in der Therapie solider Tumoren zu sein; eine weitergehende Beurteilung kann jedoch erst anhand der Ergebnisse der bereits begonnenen Phase-III-Studien erfolgen.Abstract□ BackgroundThe overall mortality due to metastatic cancer has not or only minimally been reduced in spite of intensive research and many innovations in the field of conventional antineoplastic therapy in the past decade. In the last years it has become a fact that tumor growth is angiogenesis-dependent. Therefore, inhibitors of angiogenesis are a new class of antineoplastic substances with a novel mechanism of action that might be a powerful complement to conventional cytostatic therapy.□ Substances and Clinical TrialsInhibitors of tumor-angiogenesis which have entered clinical trials, with their results published until December 1998 are discussed here. Most results originate from phase-I or phase-II clinical trials. They are discussed and compared in respect to toxicity and response. Also some substances with high therapeutic potential which are still in preclinical testing are discussed.□ ResultsMany of the investigated angiogenesis inhibitors demonstrated anti-tumor effects in phase-I or phase-II clinical trials. The commonest manifestation was stable disease, followed by partial remissions. In a few cases, complete remissions were observed. The toxicities of these substances differ both in type and degree of side effects.□ ConclusionSome antiangiogenic drugs appear to be promising candidates for a clinical use in the therapy of solid tumors. Further conclusions can only be drawn after evaluation of the results of ongoing phase-III clinical trials.BACKGROUND The overall mortality due to metastatic cancer has not or only minimally been reduced in spite of intensive research and many innovations in the field of conventional antineoplastic therapy in the past decade. In the last years it has become a fact that tumor growth is angiogenesis-dependent. Therefore, inhibitors of angiogenesis are a new class of antineoplastic substances with a novel mechanism of action that might be a powerful complement to conventional cytostatic therapy. SUBSTANCES AND CLINICAL TRIALS: Inhibitors of tumor-angiogenesis which have entered clinical trials, with their results published until December 1998 are discussed here. Most results originate from phase-I or phase-II clinical trials. They are discussed and compared in respect to toxicity and response. Also some substances with high therapeutic potential which are still in preclinical testing are discussed. RESULTS Many of the investigated angiogenesis inhibitors demonstrated anti-tumor effects in phase-I or phase-II clinical trials. The commonest manifestation was stable disease, followed by partial remissions. In a few cases, complete remissions were observed. The toxicities of these substances differ both in type and degree of side effects. CONCLUSION Some antiangiogenic drugs appear to be promising candidates for a clinical use in the therapy of solid tumors. Further conclusions can only be drawn after evaluation of the results of ongoing phase-III clinical trials.