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Oncotarget. 2015 May 20;6(14):12196-208.

Hepatitis B virus X protein induces expression of alpha-fetoprotein and activates PI3K/mTOR signaling pathway in liver cells.

Zhu M1,2, Guo J1,3, Li W1,2, Lu Y1,2, Fu S1, Xie X4, Xia H1,2, Dong X1,2, Chen Y1,2, Quan M3, Zheng S1,5, Xie K3, Li M1,2.

Author information

1
Hainan Provincial Key Laboratory of Carcinogenesis and Intervention, Hainan Medical College, Haikou, Hainan 571199, P. R. China.
2
Key Laboratory of Molecular Biology, Hainan Medical College, Haikou, Hainan 571199, P. R. China.
3
Department of Gastroenterology, Hepatology & Nutrition, The University of Texas MD Anderson Cancer Center, Houston, TX 77030, USA.
4
Department of Physiology and Pathophysiology, Hainan Medical College, Haikou, Hainan 571199, P. R. China.
5
Tumor Institute, Affiliated Hospital of Hainan Medical College, Haikou, Hainan 570102, P. R. China.

Abstract

The hepatitis B virus (HBV)-X protein (HBx) induces malignant transformation of liver cells, and elevated expression of alpha-fetoprotein (AFP) is a significant biomarker of hepatocarcinogenesis. However, the role of AFP in HBV-related hepatocarcinogenesis is unclear. In this study, we investigated the regulatory impact of AFP expression on HBx-mediated malignant transformation of human hepatocytes. We found that HBV induced the expression of AFP before that of oncogenes, e.g., Src, Ras and chemokine (C-X-C motif) receptor 4 (CXCR4), and AFP activated protein kinase B (AKT) and mammalian target of rapamycin (mTOR) in HBV-related HCC tissues and in human liver cells transfected with HBx. Cytoplasmic AFP interacted with and inhibited phosphatase and tensin homolog deleted on chromosome 10 (PTEN), activating the phosphatidylinositol 3-kinase (PI3K)/AKT signaling pathway and promoting mTOR-mediated stimulation of the transcription factor hypoxia inducible factor-1α (HIF-1α), and therefore led to the activation of the promoters of Src, CXCR4, and Ras genes. On the contrary, reduced expression of AFP by siRNA resulted in the repression of p-mTOR, pAKT, Src, CXCR4, and Ras in human malignant liver cells. Taken together, for the first time our study indicates that HBx-induced AFP expression critically promote malignant transformation in liver cells through the activation of PI3K/mTOR signaling.

KEYWORDS:

AFP; HBx; PI3K/mTOR signaling; hepatocarcinogenesis; liver cells

PMID:
25682869
PMCID:
PMC4494932
DOI:
10.18632/oncotarget.2906
[Indexed for MEDLINE]
Free PMC Article

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