A. Goncalves et al., Caspase-8 activation independent of CD95/CD95-L interaction during paclitaxel-induced apoptosis in human colon cancer cells (HT29-D4), BIOCH PHARM, 60(11), 2000, pp. 1579-1584
Antimicrotubule agent-induced apoptosis was examined in the proliferating h
uman colon cancer cell line HT29-D4. G2/M arrest and subsequent apoptosis w
ere dose-dependent, both observed with 100 nM paclitaxel or docetaxel and 1
0 nM vinorelbine. Bcl-x(1), phosphorylation was observed simultaneously wit
h mitotic block, then caspase-3 cleavage and poly(ADP-ribose) polymerase de
gradation were detected 48 hr later. By using both enzymatic assay and immu
noblot detection of cleaved fragments, we showed that caspase-8, a central
component of the CD95-induced apoptotic pathway, was significantly activate
d during paclitaxel exposure, contemporary to apoptosis occurrence. Caspase
-8 activation and apoptosis were independent of CD95 ligation and evidenced
only for concentrations inducing Bcl-x(L), phosphorylation and a decrease
in mitochondria permeability. Similar results were obtained with docetaxel
and vinca alkaloids. Thus, antimitotic drugs may induce apoptosis via caspa
se-8 activation independently of CD95/CD95-L. Caspase-8 may be a common med
iator of anticancer drug-induced apoptosis that could represent a promising
target for future therapies. (C) 2000 Elsevier Science Inc.