Signaling network of paclitaxel-induced apoptosis in the LNCaP prostate cancer cell line.
OBJECTIVE
To attempt to identify the relationship of the key regulator molecules in paclitaxel-induced apoptosis using two metastatic cell lines: the human prostate carcinoma LNCaP line and the cervical carcinoma HeLa cell line.


METHODS
Both LNCaP and HeLa cells were continuously exposed to clinically achievable concentrations of paclitaxel and observed for activation of programmed cell death as measured by cytotoxic dose-response curves, poly(adenosine diphosphate-ribose) polymerase cleavage, bcl-2 phosphorylation, and the activation of caspase-7 (interleukin-1 beta converting enzyme (ICE)-LAP3).


RESULTS
Initially, we asked whether paclitaxel-induced bcl-2 phosphorylation is triggered by the spindle assembly checkpoint via an active cdc2 kinase-dependent pathway and whether phosphorylation of endogenous bcl-2 is the signal that activates cell death machinery. Paclitaxel-induced G2/M cell cycle arrest correlated with cdc2 kinase activity and bcl-2 phosphorylation. Olomoucin, a specific inhibitor of cyclin-dependent kinases, inhibited bcl-2 phosphorylation. On the basis of these studies, we then investigated whether bcl-2 was phosphorylated in a cell cycle-dependent fashion. Analysis of synchronized HeLa cells demonstrated that endogenous bcl-2 is phosphorylated in a G2/M cell cycle-dependent manner without apoptosis.


CONCLUSIONS
Our results indicate that the events associated with paclitaxel-induced cytotoxicity are connected to each other and represent the signaling network of paclitaxel-induced mitotic arrest and cell death. In addition, we confirmed that the death-decision of paclitaxel-induced apoptosis is not mediated by bcl-2 phosphorylation and believe that this decision may be mediated by the activated spindle assembly checkpoint.
Panvichian
R
R
Department of Internal Medicine, Comprehensive Cancer Center, University of Michigan, Ann Arbor, USA.
Orth
K
K
Pilat
M J
MJ
Day
M L
ML
Day
K C
KC
Yee
C
C
Kamradt
J M
JM
Pienta
K J
KJ
D000972:Antineoplastic Agents, Phytogenic / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects*; D020169:Caspases / Q000502:physiology; D018797:Cell Cycle Proteins / Q000378:metabolism; D019926:Cyclin B / Q000378:metabolism; D056744:Cyclin B1; D004305:Dose-Response Relationship, Drug; D006367:HeLa Cells; D006801:Humans; D008297:Male; D017239:Paclitaxel / Q000494:pharmacology*; D011471:Prostatic Neoplasms / Q000473:pathology*; D014407:Tumor Cells, Cultured
D000972:Antineoplastic Agents, Phytogenic; C534699:CCNB1 protein, human; D018797:Cell Cycle Proteins; D019926:Cyclin B; D056744:Cyclin B1; D020169:Caspases; D017239:Paclitaxel