Raloxifene, a mixed estrogen agonist/antagonist, induces apoptosis in androgen-independent human prostate cancer cell lines.
Raloxifene, a selective estrogen receptor (ER) modulator, is a mixed estrogen agonist/antagonist that has been shown to prevent osteoporosis and breast cancer in women. Because the prostate contains high levels of ER-beta, the present study investigated the effect of raloxifene in three well-characterized, androgen-independent human prostate cancer cell lines: (a) PC3; (b) PC3M; and (c) DU145. Reverse transcriptase-PCR and Western blot analysis for ER-alpha and ER-beta demonstrated that all three cell lines express ER-beta, whereas only PC3 and PC3M cells were positive for ER-alpha. After the treatment with raloxifene, a dramatic increase in cell death was observed in a dose-dependent manner in the three prostate cancer cell lines (10(-9) to 10(-6) M range). Because the three prostate cancer cell lines demonstrated similar morphological changes after the raloxifene treatment, PC3 (ER-alpha/ER-beta+) and DU145 (ER-beta+ only) cells were selected to further characterize the raloxifene-induced cell death. Using the nucleus-specific stain 4',6-diamidino-2-phenylindole, nuclear fragmentation was observed in a time-dependent manner in both cell lines after exposure to 10(-6) M raloxifene. Using the terminal deoxynucleotidyl transferase-mediated nick end labeling apoptotic assay, it was demonstrated that the nuclear fragmentation was caused by apoptosis. To investigate the possibility that caspase activation is involved in raloxifene-induced apoptosis, cells were treated with the pan-caspase inhibitor ZVAD. The results demonstrated that the dramatic change in cellular morphology after treatment with raloxifene was no longer observed when cells were pretreated with ZVAD. Immunoblot demonstrated activation of caspases 8 and 9 in PC3 and DU145 cells, respectively. Taken together, these results demonstrate that the mixed estrogen agonist/antagonist, raloxifene, induces apoptosis in androgen-independent human prostate cancer cell lines.
Kim
Isaac Yi
IY
Laboratory of Cell Regulation and Carcinogenesis, National Cancer Institute/NIH, Building 41, Room C629, 9000 Rockville Pike, Bethesda, MD 20892, USA.
Kim
Byung-Chul
BC
Seong
Do Hwan
DH
Lee
Dug Keun
DK
Seo
Jeong-Meen
JM
Hong
Young Jin
YJ
Kim
Heung-Tae
HT
Morton
Ronald A
RA
Kim
Seong-Jin
SJ
D017209:Apoptosis / Q000187:drug effects*; D006801:Humans; D008297:Male; D009376:Neoplasms, Hormone-Dependent / Q000188:drug therapy / Q000473:pathology; D011471:Prostatic Neoplasms / Q000188:drug therapy* / Q000473:pathology; D020849:Raloxifene Hydrochloride / Q000494:pharmacology*; D020845:Selective Estrogen Receptor Modulators / Q000494:pharmacology*; D014407:Tumor Cells, Cultured
D020845:Selective Estrogen Receptor Modulators; D020849:Raloxifene Hydrochloride