Inhibition of formation of microtubular paracrystals in HeLa-S3 cells by neocarzinostatin.

The effect of an antitumor antibiotic, neocarzinostatin (NCS), on the formation of microtubular paracrystals (PC) induced by vinblastine sulfate, 10 mug/ml, in HeLa-S3 cells was examined by phase-contrast microscopy. The pretreatment of HeLa-S3 cells with NCS, 5 to 50 mug/ml, for 4 hr prevented the PC formation, and there was a dose response of NCS to the degree of inhibition. When the same inhibitory effect on PC formation was examined with other antitumor agents at high doses (50 mug/ml), colchicine was found to be one of the most effective agents, like NCS. Puromycin, antimycin, adriamycin, cytochalasin B, and cycloheximide revealed moderate activity, and the other antibiotics, such as mitomycin C, bleomycin, and rifampicin, did not show any effect at all. NCS was a unique antibiotic that inhibited PC formation among inhibitors of DNA synthesis. It was suggested that NCS affects the microfibrillar-microtubular proteins system in vivo, resulting in the inhibitions of organization of spindle fibers from microtubules at the G2 phase in HeLa cells.