Stimulation of B7-H1 in hepatocarcinoma cells by hepatitis B virus X antigen.
The cross-talk between the hepatitis B virus X protein (HBx) and B7-H1 in hepatocarcinoma (HCC) is unclear. This study analyzed the potential relationships between HBx and B7-H1 in hepatocarcinogenesis. One of human HCC cell lines, HepG2 cells, was transfected to stably express HBx protein (HBx(+)-HepG2). The transcription of B7-H1 mRNA was increased significantly in these cells compared to cells transfected with control vector (HBx(-)-HepG2), as confirmed by a comparative genome-wide microarray analysis (Capitalbio) and real time quantitative PCR (qPCR). Flow cytometry and western-blot further demonstrated that B7-H1 protein synthesis was enhanced in HBx(+)-HepG2 cells. Site-directed mutagenesis of promoter constructs revealed that the transcription factor (NF)-κB binding site between 128 and 137 bp upstream of B7-H1 gene transcriptional start site is primarily responsible for HBx-mediated B7-H1 expression. Co-culture experiments with HBx(+)-HepG2/T cells showed that the number of apoptotic T cells increased profoundly, and this effect could be partially prevented when a neutralizing mAb against B7-H1 was added to the culture, demonstrating that B7-H1 signaling can promote T cell apoptosis. Our results suggest that the expression of B7-H1 in hepatocarcimona cells can be initiated by HBx antigen, thus inducing T cell apoptosis and finally potentially facilitates the genesis of HCC.
Wu
Shengxi
S
Institute of Immunology, PLA, The Third Military Medical University, Chongqing 400038, PR China.
Yang
Chengying
C
Guo
Sheng
S
Fei
Lei
L
Luo
Na
N
Fu
Xiaolan
X
Chen
Yongwen
Y
Wu
Yuzhang
Y
D019138:Antibodies, Blocking / Q000494:pharmacology; D015703:Antigens, CD / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D017209:Apoptosis / Q000187:drug effects / Q000276:immunology; D060890:B7-H1 Antigen; D006528:Carcinoma, Hepatocellular / Q000276:immunology* / Q000473:pathology / Q000821:virology*; D018920:Coculture Techniques; D056945:Hep G2 Cells; D006515:Hepatitis B virus / Q000276:immunology*; D006801:Humans; D046228:Microarray Analysis; D016328:NF-kappa B / Q000378:metabolism; D011401:Promoter Regions, Genetic / Q000276:immunology; D011485:Protein Binding / Q000235:genetics / Q000276:immunology; D013601:T-Lymphocytes / Q000187:drug effects / Q000276:immunology / Q000378:metabolism* / Q000473:pathology; D015533:Transcriptional Activation / Q000235:genetics / Q000276:immunology; D014760:Viral Fusion Proteins / Q000235:genetics / Q000276:immunology / Q000378:metabolism*
D019138:Antibodies, Blocking; D015703:Antigens, CD; D060890:B7-H1 Antigen; C423236:CD274 protein, human; D016328:NF-kappa B; D014760:Viral Fusion Proteins; C063377:X antigen, viral infections