stilbenes and Hemangioendothelioma

The mechanism of tumor cell killing by OXI4503 was investigated by studying vascular functional and morphological changes post drug administration. SCID mice bearing MHEC5-T hemangioendothelioma were given a single dose of OXI4503 at 100 mg/kg. Tumor blood flow, measured by microsphere fluorescence, was reduced by 50% at 1 hr, and reached a maximum level 6-24 hr post drug treatment. Tumor vascular permeability, measured by Evan's blue and hemoglobin, increased significantly from 3 hr and peaked at 18 hr. The elevated tumor vessel permeability was accompanied by an increase in vascular endothelial growth factor (VEGF) from 1 hr post drug treatment. Immunohistochemical staining for CD31 and laminin showed that tumor blood vessels were affected as early as 3 hr but more prominent from 6 hr. From 12 hr, the vessel structure was completely destroyed. Histopathological and double immunohistochemical staining showed morphological change and induction of apoptosis in endothelial cells at 1-3 hr, followed by tumor cell necrosis from 6-72 hr. There were no statistically significant changes of Evan's blue and hemoglobin contents in liver tissue over the time course. These results suggest that OXI4503 selectively targets tumor blood vessels, and induces blood flow shutdown while it enhances tumor blood vessel permeability. The early induction of endothelial cell apoptosis leads to functional changes of tumor blood vessels and finally to the collapse of tumor vasculature, resulting in massive tumor cell necrosis. The time course of the tumor vascular response observed with OXI4503 treatment supports this drug for development as a stand alone therapy, and also lends support for the use of the drug in combination with other cancer therapies.

Topics: Animals; Apoptosis; Diphosphates; Endothelial Cells; Female; Fluorescence; Hemangioendothelioma; Immunohistochemistry; Male; Mice; Mice, SCID; Necrosis; Permeability; Regional Blood Flow; Stilbenes; Vascular Endothelial Growth Factor A

Anti-vascular treatment by targeting proliferating endothelial cells has become a promising option in anti-neoplastic therapy. Combretastatin A-4 prodrug (CA-4PD) has been identified as a selective inhibitor of endothelial cell proliferation, acting by the interruption of microtubule assembly. In this study, the effect of CA-4PD on proliferating endothelial cells derived from a primary tumor of the vascular endothelium was investigated in vitro and in vivo. In vitro, CA-4PD was an effective inhibitor of endothelial cell proliferation in a time- and dose-dependent manner, displaying a certain selectivity toward endothelial cells in comparison to proliferating fibroblasts. Analysis of DNA profiles by FACS revealed an increasing proportion of cells arrested in the G(2) cell-cycle phase with correlation to the duration of drug exposure. A decrease in cell viability correlated with duration of drug exposure, whereas FACS analysis, DNA fragmentation assay, and DNA gel electrophoresis failed to demonstrate that DNA fragmentation was indicative of apoptosis up to 48 hr of continued drug exposure. In vivo, CA-4PD induced excessive regressive alterations in experimentally allotransplanted hemangioendotheliomas within 24 hr after singular i. p. injection of 100 mg CA-4PD/kg body weight. This represented less than one-tenth of the maximum tolerated dose. In conclusion, our findings characterize CA-4PD as a potent inhibitor of malignant endothelial cell proliferation in vitro, effecting arrest of proliferating cells in the G(2) cell-cycle phase with subsequent cell death on a pathway different from apoptosis. in vivo, CA-4PD induces extensive intratumoral cell loss within 24 hr following systemic administration, suggesting a synergistic effect of direct cell killing and the induction of vascular shutdown.

Topics: Animals; Antineoplastic Agents, Phytogenic; Cell Division; Cell Survival; DNA Fragmentation; DNA, Neoplasm; Drug Screening Assays, Antitumor; Female; Flow Cytometry; Hemangioendothelioma; Mice; Mice, SCID; Stilbenes; Tumor Cells, Cultured