PT - JOURNAL ARTICLE AU - Iyer, Sudha AU - Chaplin, Dai J. AU - Rosenthal, Dean S. AU - Boulares, A. Hamid AU - Li, Lu-Yuan AU - Smulson, Mark E. TI - Induction of Apoptosis in Proliferating Human Endothelial Cells by the Tumor-specific Antiangiogenesis Agent Combretastatin A-4 DP - 1998 Oct 15 TA - Cancer Research PG - 4510--4514 VI - 58 IP - 20 4099 - http://cancerres.aacrjournals.org/content/58/20/4510.short 4100 - http://cancerres.aacrjournals.org/content/58/20/4510.full SO - Cancer Res1998 Oct 15; 58 AB - The antiangiogenic, tubulin-binding drug combretastatin A-4 exhibits a selective toxicity for proliferating endothelial cells in vitro and induces vascular shutdown in tumor models in vivo. The mechanism of combretastatin A-4 cytotoxicity has now been investigated with cultured proliferating human umbilical vein endothelial cells by examining various markers of apoptosis. Incubation of cells with 0.1 mm combretastatin A-4 induced the conversion (first detected after 6 h) of the CPP32 proenzyme to active caspase-3, a cysteine protease that plays an important role in apoptosis in many cell types; the drug also increased caspase-3 activity. Another early event observed was the binding of annexin V to 50% of the cells 8 h after drug treatment. Internucleosomal DNA fragmentation, another hallmark of apoptosis, was detected in cells incubated with 0.1 mm combretastatin A-4 for 24 h. Staining with Hoechst 33258 revealed that about 75% of cells exhibited a nuclear morphology characteristic of apoptosis after incubation with drug for 24 h. Incubation of cells for up to 8 h with combretastatin A-4 did not induce the release of lactate dehydrogenase or increase the uptake of propidium iodide, both indicators of membrane integrity. These results indicate that the selective cytotoxic effect of combretastatin A-4 is mediated by the induction of apoptosis rather than by necrosis and may provide an enhanced clinical strategy in cancer chemotherapy with this new agent. ©1998 American Association for Cancer Research.