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Inherent growth advantage of (pre)malignant hepatocytes associated with nuclear translocation of pro-transforming growth factor alpha.

ABSTRACT: The pro-peptide of transforming growth factor alpha (proTGFalpha) was recently found in hepatocyte nuclei preparing for DNA replication, which suggests a role of nuclear proTGFalpha for mitogenic signalling. This study investigates whether the nuclear occurrence of the pro-peptide is involved in the altered growth regulation of (pre)malignant hepatocytes. In human hepatocarcinogenesis, the incidence of proTGFalpha-positive and replicating nuclei gradually increased from normal liver, to dysplastic nodules, to hepatocellular carcinoma. ProTGFalpha-positive nuclei almost always were in DNA synthesis. Also, in rat hepatocarcinogenesis, proTGFalpha-positive nuclei occurred in (pre)malignant hepatocytes at significantly higher incidences than in unaltered hepatocytes. For functional studies unaltered (GSTp(-)) and premalignant (GSTp(+)) rat hepatocytes were isolated by collagenase perfusion and cultivated. Again, DNA synthesis occurred almost exclusively in proTGFalpha-positive nuclei. GSTp(+) hepatocytes showed an approximately 3-fold higher frequency of proTGFalpha-positive nuclei and DNA replication than GSTp(-) cells. Treatment of cultures with the mitogen cyproterone acetate (CPA) elevated the incidence of proTGFalpha-positive nuclei and DNA synthesis in parallel. Conversely, transforming growth factor beta1 (TGFbeta1) lowered both. These effects of CPA and TGFbeta1 were significantly more pronounced in GSTp(+) than in GSTp(-) hepatocytes. In conclusion, nuclear translocation of proTGFalpha increases in the course of hepatocarcinogenesis and appears to be involved in the inherent growth advantage of (pre)malignant hepatocytes.

SUBMITTER: Schausberger E

PROVIDER: S-EPMC2409777 | biostudies-other | 2004 Nov

REPOSITORIES: biostudies-other

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