The PreS2 activators of the hepatitis B virus: activators of tumour promoter pathways.
Recent Results Cancer Res
; 154: 315-29, 1998.
Article
em En
| MEDLINE
| ID: mdl-10027012
ABSTRACT
In addition to causing acute and chronic hepatitis, hepatitis B virus (HBV) is considered to be a major cliological factor in the development of human hepatocellular carcinoma (HCC). Epidemiological studies have demonstrated an approximately 10-fold increase in the relative risk of HCC among HBV carried compared to noncarriers. Almost all HBV-associated HCCs studied so far harbor chromosomally integrated HBV DNA. Integrated viral DNA can encode two types of transcriptional activators, the HBx protein and the PreS2 activators [the large surface proteins (LHBs) and truncated middle surface proteins (MHBs)]. The activator function of the PreS2 activators is based on the cytoplasmic orientation of the PreS2 domain. The PreS2 domain is PKC-dependent phosphorylated. Moreover, the PreS2 domain binds of PKC alpha/beta and triggers a PKC-dependent activation of the c-Raf-1/MAP2-kinase signal transduction cascade, resulting in an activation of transcription factors such as AP-1 and NF-kB. Furthermore, by activation of this signaling cascade, the PreS2 activators cause an increased proliferation rate of hepatocytes. According to the two-step model of carcinogenesis (initiation/promotion), the PreS2 activators could exert a tumour-promoter-like function by activation of the PKC/c-Raf-1/MAP2-kinase signaling cascade cells harboring critical mutations (initiation) may be positively selected (promotion). Such a multistep process may account for the long latency period in HCC development, but it also leads to the hypothesis that each tumor reflects an individual case.
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Coleções:
01-internacional
Base de dados:
MEDLINE
Assunto principal:
Precursores de Proteínas
/
Transativadores
/
Carcinoma Hepatocelular
/
Antígenos de Superfície da Hepatite B
/
Neoplasias Hepáticas
Tipo de estudo:
Etiology_studies
/
Prognostic_studies
Limite:
Animals
/
Humans
Idioma:
En
Revista:
Recent Results Cancer Res
Ano de publicação:
1998
Tipo de documento:
Article
País de afiliação:
Alemanha