Taxol, a potent inhibitor of human HeLa and mouse fibroblast cell replication, was found to block cells in the G2 and M phases of the cell cycle and stabilize cytoplasmic microtubules. Transmission electron microscopy and indirect immunofluorescence microscopy revealed that taxol-treated cells contained microtubules, including bundles that radiated from a common site. These microtubules remained stable even when cells were shifted to cold conditions (4°C) or treated with steganacin, an antimitotic agent. Taxol also inhibited the migration behavior of fibroblast cells but did not affect their ability to produce mobile surface projections like lamellipodia and filopodia. The study suggests that taxol's mechanism of action may involve its ability to stabilize microtubules, which could be a key factor in its antitumor activity.Taxol, a potent inhibitor of human HeLa and mouse fibroblast cell replication, was found to block cells in the G2 and M phases of the cell cycle and stabilize cytoplasmic microtubules. Transmission electron microscopy and indirect immunofluorescence microscopy revealed that taxol-treated cells contained microtubules, including bundles that radiated from a common site. These microtubules remained stable even when cells were shifted to cold conditions (4°C) or treated with steganacin, an antimitotic agent. Taxol also inhibited the migration behavior of fibroblast cells but did not affect their ability to produce mobile surface projections like lamellipodia and filopodia. The study suggests that taxol's mechanism of action may involve its ability to stabilize microtubules, which could be a key factor in its antitumor activity.