Frequent epigenetic inactivation of SFRP genes in hepatocellular carcinoma.
BACKGROUND
Activation of the Wnt signaling pathway is frequently observed in hepatocellular carcinoma (HCC), though mutation of three of its components, CTNNB1, AXIN1, and AXIN2, is observed substantially less often.


METHODS
We examined the relationship between Wnt signaling and epigenetic alteration of secreted frizzled-related protein (SFRP) genes in HCC.


RESULTS
We frequently detected the active form of beta-catenin and accumulation of nuclear beta-catenin in liver cancer cell lines. We detected methylation of SFRP family genes in liver cancer cell lines (SFRP1, 9/12, 75%; SFRP2, 7/12, 58%; SFRP4, 3/12, 25%; SFRP5, 7/12, 58%) and primary HCCs (SFRP1, 9/19, 47%; SFRP2, 12/19, 63%; SFRP5, 8/19, 42%), though methylation of SFRP4 was not found in primary HCCs. SFRP methylation also was detected in hepatitis B or C virus-associated chronic hepatitis (SFRP1, 6/37, 16%; SFRP2, 14/37, 38%; SFRP5, 5/37, 14%) and liver cirrhosis (SFRP1, 10/28, 36%; SFRP2, 9/28, 32%; SFRP5, 3/28, 11%), suggesting that methylation of these genes is an early event in liver carcinogenesis. Ectopic expression of SFRPs downregulated T-cell factor/lymphocyte enhancer factor (TCF/LEF) transcriptional activity in liver cancer cells, while overexpression of a beta-catenin mutant and depletion of SFRP1 using siRNA synergistically upregulated TCF/LEF transcriptional activity.


CONCLUSIONS
Our results confirm the frequent methylation and silencing of Wnt antagonist genes in HCC, and suggest that their loss of function contributes to activation of Wnt signaling during hepatocarcinogenesis.
Takagi
Hideyasu
H
First Department of Internal Medicine, Sapporo Medical University, S1, W16, Chuo-Ku, Sapporo 060-8543, Japan.
Sasaki
Shigeru
S
Suzuki
Hiromu
H
Toyota
Minoru
M
Maruyama
Reo
R
Nojima
Masanori
M
Yamamoto
Hiroyuki
H
Omata
Masao
M
Tokino
Takashi
T
Imai
Kohzoh
K
Shinomura
Yasuhisa
Y
D048868:Adaptor Proteins, Signal Transducing; D017209:Apoptosis; D015153:Blotting, Western; D006528:Carcinoma, Hepatocellular / Q000235:genetics* / Q000473:pathology; D045744:Cell Line, Tumor; D004273:DNA, Neoplasm / Q000235:genetics*; D005136:Eye Proteins / Q000096:biosynthesis / Q000235:genetics; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D036341:Intercellular Signaling Peptides and Proteins / Q000096:biosynthesis / Q000235:genetics*; D008113:Liver Neoplasms / Q000235:genetics* / Q000473:pathology; D008565:Membrane Proteins / Q000096:biosynthesis / Q000235:genetics; D008745:Methylation; D008856:Microscopy, Fluorescence; D009154:Mutation; D016133:Polymerase Chain Reaction; D011518:Proto-Oncogene Proteins / Q000096:biosynthesis / Q000235:genetics; D051820:TCF Transcription Factors / Q000235:genetics / Q000378:metabolism; D015533:Transcriptional Activation / Q000235:genetics; D051176:beta Catenin / Q000235:genetics / Q000378:metabolism; D000094742:Secreted Frizzled-Related Proteins
D048868:Adaptor Proteins, Signal Transducing; D004273:DNA, Neoplasm; D005136:Eye Proteins; D036341:Intercellular Signaling Peptides and Proteins; D008565:Membrane Proteins; D011518:Proto-Oncogene Proteins; D051820:TCF Transcription Factors; D051176:beta Catenin; C117636:SFRP1 protein, human; D000094742:Secreted Frizzled-Related Proteins; C109618:SFRP2 protein, human; C118723:SFRP4 protein, human; C118511:SFRP5 protein, human