CpG methylation at promoter site -140 inactivates TGFbeta2 receptor gene in prostate cancer.
BACKGROUND
The action of transforming growth factor beta (TGF-beta) is mediated through type 1 (TbetaRI) and type 2 (TbetaRII) receptors. Prostate cancer cells are often resistant to TGF-beta signaling due to loss of TbetaRII expression. The authors of the current study hypothesized that CpG methylation of the TbetaRII promoter at the Sp1 binding site -140 mediates this loss of TbetaRII expression in prostate cancer.


METHODS
Sixty-seven prostate cancer (PC) samples, 8 benign prostatic hyperplasia (BPH) samples, and 4 prostate cancer cell lines (DUPro, LNCaP, ND-1 and PC-3) were analyzed for 1) TbetaRII mRNA expression by semiquantitative RT-PCR, 2) TbetaRII protein expression by immunohistochemistry, and 3) TGFbetaRII promoter methylation at CpG site -140 by methylation specific PCR and bisulfite DNA sequencing. Prostate cancer cell lines were treated with the demethylating agent 5aza2'deoxycytidine to determine if TbetaRII gene expression could be increased by blocking promoter methylation.


RESULTS
mRNA and protein expression of TbetaRII was lower in the PC samples than in the BPH samples. CpG methylation at site -140 was higher in PC than in BPH (P < 0.01). Promoter methylation was inversely correlated with TbetaRII mRNA expression in the PC and BPH samples (P < 0.0001). PC3, ND1, and DUPro TbetaRII mRNA expression increased following treatment of cells with 5-aza-2'-deoxycytidine.


CONCLUSIONS
CpG methylation of the TbetaRII promoter at CPG site -140 leads to functional loss of the TbetaRII gene in prostate cancer. Treatment with 5-aza-2' deoxycytidine can restore gene expression. The current study results report the first association between prostate cancer and loss of the TGF- beta signaling pathway by TbetaRII DNA promoter methylation.
Zhao
Hong
H
Department of Urology, Veterans Affairs Medical Center and University of California San Francisco, San Francisco, California 94121, USA.
Shiina
Hiroaki
H
Greene
Kirsten L
KL
Li
Long-Cheng
LC
Tanaka
Yuichiro
Y
Kishi
Hirofumi
H
Igawa
Mikio
M
Kane
Christopher J
CJ
Carroll
Peter
P
Dahiya
Rajvir
R
D001374:Azacitidine / Q000031:analogs & derivatives* / Q000494:pharmacology; D018899:CpG Islands; D019175:DNA Methylation; D000077209:Decitabine; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D007150:Immunohistochemistry; D008297:Male; D011401:Promoter Regions, Genetic; D011471:Prostatic Neoplasms / Q000235:genetics*; D017346:Protein Serine-Threonine Kinases; D012333:RNA, Messenger / Q000378:metabolism; D000077294:Receptor, Transforming Growth Factor-beta Type II; D018125:Receptors, Transforming Growth Factor beta / Q000235:genetics* / Q000378:metabolism*; D014407:Tumor Cells, Cultured
D012333:RNA, Messenger; D018125:Receptors, Transforming Growth Factor beta; D000077209:Decitabine; D017346:Protein Serine-Threonine Kinases; D000077294:Receptor, Transforming Growth Factor-beta Type II; D001374:Azacitidine