Molecular mechanisms of (-)-gossypol-induced apoptosis in human prostate cancer cells.
BACKGROUND
Gossypol, a natural compound present in cottonseeds, displays antiproliferative and pro-apoptotic effects against various cancer cells. The (-)-gossypol enantiomer is a more potent inhibitor of cancer cell growth. Here, the molecular mechanisms of apoptosis induced by (-)-gossypol were studied in human prostate cancer cells.


METHODS
After the prostate cancer cell DU-145 had been treated with (-)-gossypol, the trypan blue exclusion assay and DNA fragment end-labeling assay were used to stain the dead cells and to detect DNA laddering, respectively. The effects of (-)-gossypol on the expression of apoptotic-regulated gene markers in both death receptor- and mitochondria-mediated apoptotic pathways, such as the Bcl-2 family and caspase, etc., were detected by RT-PCR and Western blot analysis. To further investigate the apoptotic pathways induced by (-)-gossypol, different caspase inhibitors were used to block caspase activities and cell viability was detected by the CellTiter 96 AQueous assay in DU-145 cells.


RESULTS
At a 5-10 microM dose-level, (-)-gossypol significantly enhanced apoptosis measured by DNA fragmentation. (-)-Gossypol caused apoptosis in DU-145 cells through the down-regulation of Bcl-2 and Bcl-xL and the up-regulation of Bax at the mRNA and protein levels. (-)-Gossypol also activated caspases-3, -8 and -9 and increased PARP [poly (ADP-ribose) polymerase] cleavage. Furthermore, (-)-gossypol-induced apoptosis might be due to an increase in CAD (caspase-activated deoxyribonuclease) proteins and a decrease in ICAD (inhibitor of CAD) proteins. By using caspase inhibitors, (-)-gossypol caused apoptosis via the caspase-dependent pathways.


CONCLUSIONS
Our results indicated that the apoptotic processes caused by (-)-gossypol are mediated by the regulation of the Bcl-2 and caspase families in human prostate cancer cells. Our data also suggested that (-)-gossypol may have chemotheraputic benefits for prostate cancer patients.
Huang
Yi-Wen
YW
Laboratory of Reproductive and Molecular Endocrinology, College of Veterinary Medicine and The Ohio State University, Columbus, OH 43210, USA.
Wang
Li-Shu
LS
Chang
Hsiang-Lin
HL
Ye
Weiping
W
Dowd
Michael K
MK
Wan
Peter J
PJ
Lin
Young C
YC
D017209:Apoptosis / Q000187:drug effects* / Q000502:physiology; D020169:Caspases / Q000378:metabolism; D045744:Cell Line, Tumor; D004789:Enzyme Activation / Q000187:drug effects; D006072:Gossypol / Q000494:pharmacology*; D006801:Humans; D008297:Male; D011065:Poly(ADP-ribose) Polymerases / Q000378:metabolism; D011471:Prostatic Neoplasms / Q000188:drug therapy* / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000096:biosynthesis / Q000235:genetics; D012333:RNA, Messenger / Q000096:biosynthesis
D019253:Proto-Oncogene Proteins c-bcl-2; D012333:RNA, Messenger; D011065:Poly(ADP-ribose) Polymerases; D020169:Caspases; D006072:Gossypol