Microtubules are intrinsically dynamic polymers; and their dynamics play a
crucial role in mitotic spindle assembly, the mitotic checkpoint, and chrom
osome movement. We hypothesized that, in living cells, suppression of micro
tubule dynamics is responsible for the ability of taxol to inhibit mitotic
progression and cell proliferation. Using quantitative fluorescence video m
icroscopy, we examined the effects of taxol (30-100 nM) on the dynamics of
individual microtubules in two living human tumor cell Lines: Caov-3 ovaria
n adenocarcinoma cells and A-498 kidney carcinoma cells. Taxol accumulated
more in Caov-3 cells than in A-498 cells. At equivalent intracellular taxol
concentrations, dynamic instability was inhibited similarly in the two cel
l lines. Microtubule shortening rates were inhibited in Caov-3 cells and in
A-498 cells by 32 and 26%, growing rates were inhibited by 24 and 18%, and
dynamicity was inhibited by 31 and 63%, respectively. All mitotic spindles
were abnormal, and many interphase cells became multinucleate (Caov-3, 30%
; A-498, 58%). Taxol blocked cell cycle progress at the metaphase/anaphase
transition and inhibited cell proliferation. The results indicate that supp
ression of microtubule dynamics by taxol deleteriously affects the ability
of cancer cells to properly assemble a mitotic spindle, pass the metaphase/
anaphase checkpoint, and produce progeny.