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The aim of the present work is to investigate whether microtubule-affecting drugs including vincristine, vinblastine, vindesine and vinorelbine are able to produce an anti-angiogenic effect at non-cytotoxic doses in the same way of taxol. The cytotoxic effects were determined by means of the colorimetric MTT assay, and the anti-angiogenic effects on HUVEC cells growing on Matrigel and forming capillary networks. Sixteen additional drugs (camptothecin, SN38, topothecan, adriamycin, daunomycin, etoposide, bleomycin, melphalan, mitomycin C, TNP-470, cisplatin, carboplatin, 5-fluorouracil, methotrexate, suramin and batimastat) were used as control in order to test the specificity of the microtubule-affecting drug effects. We also investigated by means of videomicroscopy whether microtubule-affecting drugs could produce anti-migratory effects at non-cytotoxic doses on tumor cells. Finally, we used computer-assisted fluorescence microscopy to characterize the influence of microtubule-affecting drugs on the polymerization/depolymerization dynamics of the actin cytoskeleton in tumor cells. Our results show that taxol, vincristine and vindesine behave similarly in their ability to reduce the capillary network formation by HUVEC cells cultured on Matrigel. These anti-angiogenic effects appear at non-cytotoxic concentrations. In contrast, vinblastine and vinorelbine produce apparent anti-angiogenic effects by direct cytotoxicity. Microtubule-affecting agents are also able to significantly reduce the level of migration of tumor cells at non-cytotoxic concentrations, some of these effects may occur via modifications to the actin cytoskeleton organization. Several types of microtubule-affecting agents could be used as anti-angiogenic agents by administering them at non-cytotoxic concentrations, and some microtubule-affecting agents abandoned in pharmacological assays could turn out to be potent anti-migratory drugs acting on tumor cells, though without being too cytotoxic.

The development of angiogenesis within a tumor brings on a sequence of extremely complex molecular events. We have developed a methodology which enables a wide set of biological parameters to be quantitatively determined in the field of anti-angiogenesis pharmacology. This methodology which includes a video cell tracking device, is unique because it offers the possibility of evaluating the specific influence of a given compound with potential anti-angiogenic properties on cell cycle kinetics, cell death, global cell line growth, and cell motility. We chose TNP-470, a synthetic analogue of fumagilin, to test our methodology on HUVEC cell lines taken from various human umbilical cord veins. The experiments carried out with TNP-470 did not confirm all the data reported in the literature. Our results show that i) TNP-470 could be considered as a cytotoxic agent; ii) this compound had an apparently marginal cytostatic effect; and iii) it did not increase the apoptosis level. Our methodology also revealed that the HUVEC cell lines are very heterogeneous in terms of different biological parameters. This highlights the problem of the reproductibility of the result.