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

An antitumor drug, 3-(1-anilinoethylidene)-5-benzylpyrrolidine-2,4-dione (TN-16) inhibited the assembly of porcine brain microtubules in vitro. The assembly induced by taxol was also suppressed by the drug. However, the latter required much higher concentration of TN-16 than the former. 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-sensitive site of tubulin. The affinity of TN-16 to tubulin was almost equal to that of nocodazole.