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The aims of the study were to meet the demand of new tubulin antagonists with fewer side effects by characterizing the antiangiogenic properties of the experimental compound spongistatin 1, and to elucidate nonmitotic mechanisms by which tubulin antagonists inhibit angiogenesis. Although tubulin-inhibiting drugs and their antiangiogenic properties have been investigated for a long time, surprisingly little is known about their underlying mechanisms of action. Antiangiogenic effects of spongistatin 1 were investigated in endothelial cells in vitro , including functional cell-based assays, live-cell imaging, and a kinome array, and in the mouse cornea pocket assay in vivo. Spongistatin 1 inhibited angiogenesis at nanomolar concentrations (IC 50 : cytotoxicity>50 nM, proliferation 100 pM, migration 1.0 nM, tube formation 1.0 nM, chemotaxis 1.0 nM, aortic ring sprouting 500 pM, neovascularization in vivo 10 µg/kg). Further, a kinome array and validating data showed that spongistatin 1 inhibits the phosphorylation activity of protein kinase C (PKC ), an essential kinase in angiogenesis, and its translocation to the membrane. Thus, we conclude that PKC might be an important target for the antiangiogenic effects of tubulin antagonism. In addition, the data from the kinase array suggest that different tubulin antagonists might have individual intracellular actions.—Rothmeier, A. S., Ischenko, I., Joore, J., Garczarczyk, D., Fürst, R., Bruns, C. J., Vollmar, A. M., Zahler, S. Investigation of the marine compound spongistatin 1 links the inhibition of PKC translocation to nonmitotic effects of tubulin antagonism in angiogenesis.
