Investigation of extrinsic and intrinsic apoptosis pathways of new clerodane diterpenoids in human prostate cancer PC-3 cells.
In our continuing search to discover bioactive compounds from natural products, we isolated six new clerodane diterpenes, caseamembrins A to F, from Casearia membranacea and examined their antiproliferative activities in human hormone-resistant prostate cancer PC-3 cells. All of these compounds displayed effective antiproliferative activity using sulforhodamine B assays and induced cell apoptosis by a terminal deoxynucleotidyl transferase (TdT) dUTP nick-end labeling (TUNEL)-reaction technique. The data demonstrated that caseamembrin C was the most effective compound among these clerodane diterpenoids. Caseamembrin C induced down-regulation of Bcl-2 and Bcl-xL expression, while up-regulation of proapoptotic protein Mcl-1S (short chain), suggesting that these Bcl-2 family member proteins may play a role on arbitrating the apoptotic cell death. Caseamembrin C also induced the up-regulation of Fas ligand (FasL) expression, cleavage and activation of caspase-8 and caspase-9, Bid cleavage and activation of executor caspase-3. However, z-IETD-FMK (Z-Ile-Glu-Thr-Asp-fluoromethyl ketone, a selective caspase-8 inhibitor) almost completely inhibited caseamembrin C-induced Bid cleavage without any modification of caspase-9 activation, indicating that the extrinsic pathway of FasL/caspase-8/Bid cascade only played a minor role in the apoptotic signaling. Taken together, it is suggested that caseamembrin C-induced apoptosis is predominantly through the activation of intrinsic apoptosis pathways by causing the down-regulation of Bcl-2 and Bcl-xL expression, up-regulation of Mcl-1S protein and activation of caspase-9 and caspase-3.
Huang
Dong-Ming
DM
Pharmacological Institute, College of Medicine, National Taiwan University, No. 1, Jen-Ai Road, Sect. 1, Taipei, Taiwan.
Shen
Ya-Ching
YC
Wu
Chi
C
Huang
Yao-Ting
YT
Kung
Fan-Lu
FL
Teng
Che-Ming
CM
Guh
Jih-Hwa
JH
D017209:Apoptosis / Q000187:drug effects*; D015153:Blotting, Western; D061945:Caspase Inhibitors; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D004396:Coloring Agents; D004224:Diterpenes / Q000494:pharmacology*; D045785:Diterpenes, Clerodane / Q000494:pharmacology*; D004789:Enzyme Activation / Q000187:drug effects; D053222:Fas Ligand Protein; D019254:Genes, bcl-2 / Q000235:genetics; D006801:Humans; D020287:In Situ Nick-End Labeling; D008297:Male; D008562:Membrane Glycoproteins / Q000096:biosynthesis; D064549:Myeloid Cell Leukemia Sequence 1 Protein; D009363:Neoplasm Proteins / Q000096:biosynthesis / Q000235:genetics; D011471:Prostatic Neoplasms / Q000188:drug therapy* / Q000473:pathology; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000096:biosynthesis / Q000235:genetics; D012235:Rhodamines; D015398:Signal Transduction / Q000187:drug effects*; D013778:Tetrazolium Salts; D013844:Thiazoles
D061945:Caspase Inhibitors; D004396:Coloring Agents; D004224:Diterpenes; D045785:Diterpenes, Clerodane; C505661:FASLG protein, human; D053222:Fas Ligand Protein; D008562:Membrane Glycoproteins; D064549:Myeloid Cell Leukemia Sequence 1 Protein; D009363:Neoplasm Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D012235:Rhodamines; D013778:Tetrazolium Salts; D013844:Thiazoles; C022027:lissamine rhodamine B; C022616:thiazolyl blue