Tubulin possesses two distinct binding sites for vinblastine; one of high affinity (Ka = 6.2 X 106M” ) occupancy of which prevents polymerization of tubulin and a second, lower affinity site (K, = 8 X 104M”) occupancy of which correlates with the aggregating effects of the alkaloid on tubulin [l]. The recent report [2] that maytansine, a new antitumor agent of plant origin [3,4] , was a potent ...

Data generated in the new National Cancer Institute drug evaluation program, which is based on inhibition of cell growth in 60 human tumor cell lines, were used to compare new compounds with agents of known mechanism of action in terms of their differential cytotoxicity. Two marine natural products, halichondrin B and homohalichondrin B, appeared repeatedly when the data base was probed with kn...

We have characterized the effects of vinblastine on the dynamic instability behavior of individual microtubules in living BS-C-1 cells microinjected with rhodamine-labeled tubulin and have found that at low concentrations (3-64 nM), vinblastine potently suppresses dynamic instability without causing net microtubule depolymerization. Vinblastine suppressed the rates of microtubule growth and sho...

The total synthesis and evaluation of a key systematic series of vinblastines that incorporate the first deep-seated changes to the substituent at C4 are detailed. The synthetic approach features an expanded and redefined scope of a 1,3,4-oxadiazole [4 + 2]/[3 + 2] cycloaddition cascade in which electronically mismatched electron-deficient trisubstituted alkenes and unactivated trisubstituted a...

Both dibutyryl cyclic AMP (DBcAMP) and cholera toxin promote the formation and elongation of processes of cultivated Greene hamster melanoma cells. The formation and maintenance of these processes, which contain many microtubules, are sensitive to colcemid and vinblastine. Tubulin was measured by [3H]colchicine binding and by acrylamide gel electrophoresis. We found that DBcAMP or cholera toxin...

The mode of action of rhizoxin (1a), a new antitumor macrolide, was investigated. Rhizoxin inhibited fusion of the male and the female pronuclei in fertilized sea urchin eggs and inhibited cilia formation in the deciliated sea urchin embryos. In vitro, polymerization of tubulin isolated from porcine brains was completely inhibited at a 1 X 10(-5) M concentration of rhizoxin, and tubulin which h...

(3-(1H-indol-2-yl)phenyl)(3,4,5-trimethoxyphenyl)methanone (I-387) is a novel synthetic compound that inhibits tubulin action and exhibits potent antitumor activity in various preclinical models. I-387 inhibited the in vitro growth of several human cancer cell lines with IC₅₀ values in the range of 15 to 39 nmol/L. Nanomolar concentrations of the compound induced apoptosis and caused phosphoryl...

Vinblastine is a powerful antitumor drug in widespread use in cancer chemotherapy. The mechanism by which vinblastine effects its unusually potent antiproliferative action is by inhibition of mitosis (Jordan et al., 1991), and often has been ascribed to its capacity to depolymerize mitotic spindle microtubules (e.g. Malawista et al., 1968; Wilson and Bryan, 1974). However, in recent studies we ...

The total synthesis and evaluation of a key systematic series of vinblastines that incorporate the first deepseated changes to the substituent at C4 are detailed. The synthetic approach features an expanded and redefined scope of a 1,3,4-oxadiazole [4 + 2]/[3 + 2] cycloaddition cascade in which electronically mismatched electron-deficient trisubstituted alkenes and unactivated trisubstituted al...

Using cell based screening assay, we identified a novel anti-tubulin agent (Z)-5-((5-(4-bromo-3-chlorophenyl)furan-2-yl)methylene)-2-thioxothiazolidin-4-one (BCFMT) that inhibited proliferation of human cervical carcinoma (HeLa) (IC(50), 7.2 ± 1.8 µM), human breast adenocarcinoma (MCF-7) (IC(50), 10.0 ± 0.5 µM), highly metastatic breast adenocarcinoma (MDA-MB-231) (IC(50), 6.0 ± 1 µM), cisplati...