Caspase-dependent apoptosis induction by guggulsterone, a constituent of Ayurvedic medicinal plant Commiphora mukul, in PC-3 human prostate cancer cells is mediated by Bax and Bak.
The present study was undertaken to gain insights into the molecular mechanism of cell death (apoptosis) by guggulsterone, a constituent of Ayurvedic medicinal plant Commiphora mukul, using PC-3 human prostate cancer cells as a model. The viability of PC-3 cells, but not a normal prostate epithelial cell line (PrEC), was reduced significantly on treatment with guggulsterone in a concentration-dependent manner. Guggulsterone-mediated suppression of PC-3 cell proliferation was not due to perturbation in cell cycle progression but caused by apoptosis induction characterized by appearance of subdiploid cells and cytoplasmic histone-associated DNA fragmentation. Guggulsterone-induced apoptosis was associated with induction of multidomain proapoptotic Bcl-2 family members Bax and Bak. Interestingly, the expression of antiapoptotic proteins Bcl-2 and Bcl-xL was initially increased in guggulsterone-treated PC-3 cells but declined markedly following a 16- to 24-hour treatment with guggulsterone. Ectopic expression of Bcl-2 in PC-3 cells failed to confer significant protection against guggulsterone-induced cell death. On the other hand, SV40 immortalized mouse embryonic fibroblasts derived from Bax-Bak double knockout mice were significantly more resistant to guggulsterone-induced cell killing compared with wild-type cells. Guggulsterone treatment resulted in cleavage (activation) of caspase-9, caspase-8, and caspase-3, and guggulsterone-induced cell death was significantly attenuated in the presence of general caspase inhibitor as well as specific inhibitors of caspase-9 and caspase-8. In conclusion, the present study indicates that caspase-dependent apoptosis by guggulsterone is mediated in part by Bax and Bak.
Singh
Shivendra V
SV
Department of Pharmacology and University of Pittsburgh Cancer Institute, University of Pittsburgh School of Medicine, 2.32A Hillman Cancer Center Research Pavilion, 5117 Centre Avenue, Pittsburgh, Pennsylvania 15213, USA. singhs@upmc.edu
Zeng
Yan
Y
Xiao
Dong
D
Vogel
Victor G
VG
Nelson
Joel B
JB
Dhir
Rajiv
R
Tripathi
Yamini B
YB
D000818:Animals; D000970:Antineoplastic Agents / Q000494:pharmacology; D017209:Apoptosis; D053148:Caspase 3; D053181:Caspase 8; D053453:Caspase 9; D020169:Caspases / Q000378:metabolism*; D002453:Cell Cycle; D016923:Cell Death; D045744:Cell Line, Tumor; D002478:Cells, Cultured; D029744:Commiphora / Q000378:metabolism; D003593:Cytoplasm / Q000378:metabolism; D053938:DNA Fragmentation; D004789:Enzyme Activation; D005347:Fibroblasts / Q000378:metabolism; D006657:Histones / Q000737:chemistry; D006801:Humans; D015151:Immunoblotting; D008297:Male; D051379:Mice; D018345:Mice, Knockout; D008956:Models, Chemical; D010946:Plants, Medicinal / Q000378:metabolism; D011282:Pregnenediones / Q000494:pharmacology*; D011471:Prostatic Neoplasms / Q000188:drug therapy* / Q000473:pathology*; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D013997:Time Factors; D050998:bcl-2 Homologous Antagonist-Killer Protein / Q000378:metabolism / Q000502:physiology*; D051028:bcl-2-Associated X Protein / Q000378:metabolism / Q000502:physiology*
D000970:Antineoplastic Agents; D006657:Histones; D011282:Pregnenediones; D050998:bcl-2 Homologous Antagonist-Killer Protein; D051028:bcl-2-Associated X Protein; C023617:pregna-4,17-diene-3,16-dione; C505407:CASP3 protein, human; C505530:CASP8 protein, human; C506433:CASP9 protein, human; C505409:Casp3 protein, mouse; C505526:Casp8 protein, mouse; C506434:Casp9 protein, mouse; D053148:Caspase 3; D053181:Caspase 8; D053453:Caspase 9; D020169:Caspases