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Hepatitis B virus X protein is essential for the activation of Wnt/β‐catenin signaling in hepatoma cells
Author(s) -
Cha ManYoung,
Kim ChangMyeong,
Park YoungMin,
Ryu WangShick
Publication year - 2004
Publication title -
hepatology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.488
H-Index - 361
eISSN - 1527-3350
pISSN - 0270-9139
DOI - 10.1002/hep.20245
Subject(s) - wnt signaling pathway , hbx , ectopic expression , catenin , beta catenin , cancer research , microbiology and biotechnology , hepatitis b virus , biology , signal transduction , carcinogenesis , lrp6 , chemistry , cell culture , virology , virus , cancer , genetics
Abstract Wnt/β‐catenin signaling contributes to diverse cellular functions, such as Drosophila wing development and colon carcinogenesis. Recently, stabilizing mutations of β‐catenin, a hallmark of Wnt signaling, were documented in significant numbers of primary hepatocellular carcinomas (HCC). However, whether the β‐catenin mutation leads to the activation of Wnt/β‐catenin signaling in hepatoma cells has not been established. We found that Wnt/β‐catenin signaling could be activated by ectopic expression of Wnt‐1 in some hepatoma cells, such as Hep3B and PLC/PRF/5 cells, but not in others, such as Huh7 and Chang cells. Importantly, we noted that the former were derived from hepatitis B virus (HBV)‐infected livers, whereas the latter were derived from HBV‐negative livers. It was then speculated that HBx, a viral regulatory protein of HBV, is involved in activating Wnt/β‐catenin signaling in hepatoma cells. In agreement with this notion, ectopic expression of HBx along with Wnt‐1 activated Wnt/β‐catenin signaling in Huh7 cells by stabilizing cytoplasmic β‐catenin. Further, we showed that such stabilization of β‐catenin by HBx was achieved by suppressing glycogen synthase kinase 3 activity via the activation of Src kinase. In conclusion , the data suggest that Wnt‐1 is necessary but insufficient to activate Wnt/β‐catenin signaling in hepatoma cells and the enhanced stabilization of β‐catenin by HBx, in addition to Wnt‐1, is essential for the activation of Wnt/β‐catenin signaling in hepatoma cells. (H EPATOLOGY 2004;39:1683–1693.)