Restoration of insulin-like growth factor binding protein-related protein 1 has a tumor-suppressive activity through induction of apoptosis in human prostate cancer.
Insulin-like growth factor binding protein-related protein 1 (IGFBP-rP1), a member of the IGFBP super family, is down-regulated at the mRNA level in several solid cancers. We hypothesize that IGFBP-rP1 has a tumor-suppressive effect on prostate cancer growth and its inactivation is through CpG hypermethylation. We tested this hypothesis through expression analysis of IGFBP-rP1, transfection studies, growth analysis, and CpG methylation in prostate cancer cells and tissues. In situ hybridization revealed IGFBP-rP1 mRNA expression was detected in the stroma and epithelium of benign prostatic hyperplasia tissues but was either weak or lost in prostate cancer tissues. The mRNA expression for IGFBP-rP1 was lacking in DU145, LNCaP, ND-1, and PC-3 prostate cancer cell lines, and after demethylation (5-aza-dC treatment), the expression was restored suggesting that methylation inactivated IGFBP-rP1 expression in prostate cancer cells. We further tested whether transfection of IGFBP-rP1 can modulate prostate cancer cells growth. We transfected PC-3 cell lines with IGFBP-rP1 cDNA (PC-3-rP1) and Northern blotting confirmed mRNA transcript of IGFBP-rP1 in these PC-3-rP1 clones. A 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay showed growth rate was significantly lower in PC-3-rP1 cells than in the nontransfected control. In addition, the medium obtained from PC-3-rP1 cells reduced the growth rate in both PC-3-rP1 and control PC-3 cells. A soft agar colony-forming assay revealed that colony formation was markedly decreased in PC-3-rP1 cells. The number of apoptotic cells and caspase-3 expression were increased in the PC-3-rP1 cells as compared with control PC-3 cells. This is the first study that suggests inactivation of IGFBP-rP1 is through CpG methylation, and tumor-suppressive activity of IGFBP-rP1 is through induction of apoptosis in an IGF-I independent manner in prostate cancer.
Mutaguchi
Kazuaki
K
Department of Urology, Graduate School of Biomedical Sciences, Hiroshima University, 1-2-3 Kasumi, Minami-ku, Hiroshima 734-8551, Japan.
Yasumoto
Hiroaki
H
Mita
Kouji
K
Matsubara
Akio
A
Shiina
Hiroaki
H
Igawa
Mikio
M
Dahiya
Rajvir
R
Usui
Tsuguru
T
D000964:Antimetabolites, Antineoplastic / Q000494:pharmacology; D017209:Apoptosis / Q000502:physiology*; D001374:Azacitidine / Q000031:analogs & derivatives* / Q000494:pharmacology; D053148:Caspase 3; D020169:Caspases / Q000096:biosynthesis / Q000235:genetics; D002455:Cell Division / Q000187:drug effects / Q000502:physiology; D045744:Cell Line, Tumor; D017077:Culture Media, Conditioned; D018076:DNA, Complementary / Q000235:genetics; D000077209:Decitabine; D006801:Humans; D018969:Insulin-Like Growth Factor Binding Proteins / Q000096:biosynthesis / Q000235:genetics / Q000502:physiology*; D007334:Insulin-Like Growth Factor I / Q000494:pharmacology; D008297:Male; D011471:Prostatic Neoplasms / Q000235:genetics / Q000378:metabolism / Q000473:pathology*; D012333:RNA, Messenger / Q000096:biosynthesis / Q000235:genetics; D014162:Transfection
D000964:Antimetabolites, Antineoplastic; D017077:Culture Media, Conditioned; D018076:DNA, Complementary; D018969:Insulin-Like Growth Factor Binding Proteins; D012333:RNA, Messenger; C102529:insulin-like growth factor binding protein-related protein 1; D007334:Insulin-Like Growth Factor I; D000077209:Decitabine; C505407:CASP3 protein, human; D053148:Caspase 3; D020169:Caspases; D001374:Azacitidine