Inhibition of microtubule assembly in vitro by a synthetic antitumor drug, TN-16.

A synthetic antitumor drug, 3-(1-anilinoethylidene)-5-benzylpyrrolidine-2,4-dione (TN-16), inhibited the assembly of porcine brain microtubules in vitro. The taxol-dependent assembly was also inhibited by the drug. However, the latter required much higher concentration of TN-16. Binding studies by means of the fluorometric method and the spun-column procedure indicate that the inhibition was caused by the reversible binding of the drug to the colchicine-binding site on tubulin. The affinity of TN-16 to tubulin was almost equal to that of nocodazole.