Paclitaxel induces apoptosis through activation of nuclear protein kinase C-δ and subsequent activation of Golgi associated Cdk1 in human hormone refractory prostate cancer.
OBJECTIVE
Emerging evidence shows that the translocation of apoptosis related factors on cellular organelles, such as mitochondria, endoplasmic reticulum, Golgi apparatus and nucleus, has a crucial role in the apoptotic process. We characterized the effect of paclitaxel (Sigma®) on Golgi involved apoptosis in human hormone refractory prostate cancer.


METHODS
FACScan™ flow cytometric analysis was used to determine cell cycle distribution and the subG1 (apoptosis) population. Protein expression and localization were detected by Western blot, confocal microscopic examination and the sucrose gradient separation technique.


RESULTS
Paclitaxel induced Golgi apparatus disassembly and interaction between Golgi complexes and mitochondria. Discontinuous sucrose gradient fractionation was used to determine and collect Golgi containing fractions. Data revealed that paclitaxel induced an increase of Cdk1 activity and DR5 expression on the Golgi complex that was associated with increased cleavage of caspase-8, a DR5 downstream factor, and caspase-3 into catalytically active fragments. Data were validated by confocal immunofluorescence microscopy. Golgi associated effects were inhibited by the Cdk1 inhibitor roscovitine (Sigma), suggesting a critical role for Golgi-Cdk1. Also, paclitaxel caused an increase of nuclear but not of Golgi associated PKC-δ activity. The selective PKC-δ inhibitor rottlerin (Sigma) completely inhibited the increase of Golgi-Cdk1 activity, suggesting that nuclear PKC-δ served as an upstream regulator of Golgi-Cdk1.


CONCLUSIONS
Data suggest that paclitaxel induces nuclear translocation and activation of PKC-δ, which in turn causes Golgi-Cdk1 activation, leading to Golgi associated DR5 up-regulation, and caspase-8 and 3 activation. Golgi mediated signaling cascades facilitate mitochondria involved apoptotic pathways and at least partly explain the anticancer activity of paclitaxel action.
School of Pharmacy, National Taiwan University, Taipei, Taiwan, Republic of China.
Pin-Hsuan
PH
Lu
Chia-Chun
CC
Yu
Po-Cheng
PC
Chiang
Yi-Cheng
YC
Chen
Yunn-Fang
YF
Ho
Fan-Lu
FL
Kung
Jih-Hwa
JH
Guh
D000972:Antineoplastic Agents, Phytogenic / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects*; D016203:CDC2 Protein Kinase / Q000502:physiology*; D006056:Golgi Apparatus / Q000201:enzymology; D006801:Humans; D008297:Male; D017239:Paclitaxel / Q000494:pharmacology*; D011471:Prostatic Neoplasms / Q000188:drug therapy / Q000201:enzymology*; D051745:Protein Kinase C-delta / Q000187:drug effects* / Q000502:physiology*; D014407:Tumor Cells, Cultured
D000972:Antineoplastic Agents, Phytogenic; D051745:Protein Kinase C-delta; D016203:CDC2 Protein Kinase; D017239:Paclitaxel