Epigenetic inactivation of Wnt inhibitory factor-1 plays an important role in bladder cancer through aberrant canonical Wnt/beta-catenin signaling pathway.
OBJECTIVE
Aberrant activation of the Wingless-type (Wnt) pathway plays a significant role in the pathogenesis of several human cancers. Wnt inhibitory factor-1 (Wif-1) was identified as one of the secreted antagonists that can bind Wnt protein. We hypothesize that Wif-1 plays an important role in bladder cancer pathogenesis.


METHODS
To test this hypothesis, epigenetic and genetic pathways involved in the Wif-1 gene modulation and expression of Wnt/beta-catenin-related genes were analyzed in 4 bladder tumor cell lines and 54 bladder tumor and matched normal bladder mucosa.


RESULTS
Wif-1 mRNA expression was significantly enhanced after 5-aza-2'-deoxycytidine treatment in bladder tumor cell lines. Wif-1 promoter methylation level was significantly higher and Wif-1 mRNA expression was significantly lower in bladder tumor samples than in bladder mucosa samples. In the total bladder tumor and bladder mucosa samples, an inverse correlation was found between promoter methylation and Wif-1 mRNA transcript levels. However, loss-of-heterozygosity at chromosome 12q14.3 close to the Wif-1 gene loci was a rare event (3.7%). Nuclear accumulation of beta-catenin was significantly more frequent in bladder tumor than in bladder mucosa and inversely correlated with Wif-1 expression. In addition, known targets of the canonical Wnt/beta-catenin signaling pathway, such as c-myc and cyclin D1, were up-regulated in bladder tumor compared with bladder mucosa, and this up-regulation was associated with reduced Wif-1 expression at both mRNA and protein levels. Furthermore, transfection of Wif-1 small interfering RNA into bladder tumor cells expressing Wif-1 mRNA transcripts had increased levels of c-myc and cyclin D1 and accelerated cell growth.


CONCLUSIONS
This is the first report showing that CpG hypermethylation of the Wif-1 promoter is a frequent event in bladder tumor and may contribute to pathogenesis of bladder cancer through aberrant canonical Wnt/beta-catenin signaling pathway. The present study elucidates novel pathways that are involved in the pathogenesis of bladder cancer.
Urakami
Shinji
S
Department of Urology 112F, Veterans Affairs Medical Center, and University of California at San Francisco, 4150 Clement Street, San Francisco, CA 94121, USA.
Shiina
Hiroaki
H
Enokida
Hideki
H
Kawakami
Toshifumi
T
Tokizane
Takashi
T
Ogishima
Tatsuya
T
Tanaka
Yuichiro
Y
Li
Long-Cheng
LC
Ribeiro-Filho
Leopoldo A
LA
Terashima
Masaharu
M
Kikuno
Nobuyuki
N
Adachi
Hiroyuki
H
Yoneda
Tatsuaki
T
Kishi
Hirofumi
H
Shigeno
Kazushi
K
Konety
Badrinath R
BR
Igawa
Mikio
M
Dahiya
Rajvir
R
D048868:Adaptor Proteins, Signal Transducing; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000964:Antimetabolites, Antineoplastic / Q000494:pharmacology; D001374:Azacitidine / Q000031:analogs & derivatives / Q000494:pharmacology; D001483:Base Sequence; D002295:Carcinoma, Transitional Cell / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D002352:Carrier Proteins / Q000037:antagonists & inhibitors / Q000235:genetics* / Q000378:metabolism; D045744:Cell Line, Tumor; D019938:Cyclin D1 / Q000235:genetics / Q000378:metabolism; D015254:DNA Modification Methylases / Q000037:antagonists & inhibitors; D000077209:Decitabine; D044127:Epigenesis, Genetic / Q000502:physiology*; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D008875:Middle Aged; D008969:Molecular Sequence Data; D016271:Proto-Oncogene Proteins c-myc / Q000235:genetics / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D034741:RNA, Small Interfering / Q000494:pharmacology; D012097:Repressor Proteins / Q000037:antagonists & inhibitors / Q000235:genetics* / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction; D001749:Urinary Bladder Neoplasms / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D051153:Wnt Proteins / Q000378:metabolism*; D051176:beta Catenin / Q000378:metabolism*
D048868:Adaptor Proteins, Signal Transducing; D000964:Antimetabolites, Antineoplastic; D002352:Carrier Proteins; D016271:Proto-Oncogene Proteins c-myc; D012333:RNA, Messenger; D034741:RNA, Small Interfering; D012097:Repressor Proteins; C485569:WIF1 protein, human; D051153:Wnt Proteins; D051176:beta Catenin; D019938:Cyclin D1; D000077209:Decitabine; D015254:DNA Modification Methylases; D001374:Azacitidine