Raloxifene, a selective estrogen receptor modulator, induces apoptosis in androgen-responsive human prostate cancer cell line LNCaP through an androgen-independent pathway.
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 a high level of ER-beta, the present study investigated the effect of raloxifene in the androgen-sensitive human prostate cancer cell line LNCaP. Previously, it has been demonstrated that LNCaP cells express ER-beta but not ER-alpha and that tamoxifene induces apoptosis in these cells. After treatment with raloxifene, a dramatic increase in cell death occurred in a dose-dependent manner (10(-9) to 10(-6) M range). Using the terminal deoxynucleotidyl transferase-mediated nick end labeling apoptotic assay, we demonstrated that the nuclear fragmentation was due to apoptosis. The dramatic change in cellular morphology after treatment with raloxifene was no longer observed when cells were pretreated with a pan-caspase inhibitor, Z-VAD-FMK, and a specific caspase-9 inhibitor, Z-LEHD-FMK. Furthermore, immunoblot demonstrated an activation of caspase-9 in LNCaP cells. Because LNCaP cells contain a mutated androgen receptor that allows cellular proliferation in the presence of antiandrogens, prostate-specific antigen assay and transfection with a reporter construct containing luciferase gene under the control of androgen response element (pARE) were carried out. The results demonstrated that raloxifene does not significantly alter androgen receptor activity in LNCaP cells. Taken together, these results demonstrate that raloxifene, a selective ER modulator, induces apoptosis in the androgen-sensitive human prostate cancer cell line LNCaP through an androgen-independent pathway.
Kim
Isaac Yi
IY
Laboratory of Cell Regulation and Carcinogenesis, National Cancer Institute, Bethesda, Maryland 20892, USA.
Seong
Do Hwan
DH
Kim
Byung-Chul
BC
Lee
Dug Keun
DK
Remaley
Alan T
AT
Leach
Fredrick
F
Morton
Ronald A
RA
Kim
Seong-Jin
SJ
D000728:Androgens / Q000502:physiology*; D017209:Apoptosis / Q000187:drug effects* / Q000502:physiology; D004305:Dose-Response Relationship, Drug; 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*; D011944:Receptors, Androgen / Q000502:physiology; D020845:Selective Estrogen Receptor Modulators / Q000494:pharmacology*; D014407:Tumor Cells, Cultured
D000728:Androgens; D011944:Receptors, Androgen; D020845:Selective Estrogen Receptor Modulators; D020849:Raloxifene Hydrochloride