Effects In Hepatocellular Carcinoma Cells Research Articles

Tissue-specific regulatory elements in the human alcohol dehydrogenase 6 gene.

The human alcohol dehydrogenase gene ADH6 is expressed at the highest levels in fetal and adult liver. We have mapped cis-acting elements that affect its expression. The sequence from bp -34 to -62 (site C) that includes the TATA box was strongly bound by nuclear proteins from liver, hepatoma cells, and fibroblasts. A truncation that removed the upstream part of site C but left the TATA homology intact dramatically reduced transcription; altering 5 bp in this region had much less effect. Part of site C can be bound by C/EBPalpha, but cotransfection with C/EBPalpha or C/EBPbeta did not stimulate transcription. The proximal region did not display tissue specificity, so we cloned the upstream region to search for additional regulatory sequences. The region between -1.6 and -2.3 kb stimulated transcription in hepatoma cells and inhibited it in fibroblasts. We identified two sites in this region that affect transcription independently of their orientation. Site 1 was a negative regulatory element in fibroblasts but had no effect in hepatoma cells. Site 2 was a positive regulatory element in hepatoma cells but had no effect in fibroblasts. This combination of positive and negative regulatory elements can play a significant role in the tissue-specific expression of ADH6.

IL-6 modulates the synthesis of a specific set of acute phase plasma proteins in vivo.

Human rIL-6, produced either in COS cells or Escherichia coli, similarly stimulates the production of acute phase plasma proteins in cultured human and rat hepatoma cells. This anabolic effect in hepatoma cells suggested a potential in vivo role of the cytokine in mediating the hepatic response to inflammation. Injection of IL-6 into adult male rats elicited a cytokine-specific change in the liver expression of acute phase proteins. As predicted from in vitro studies, glucocorticoids were needed to achieve a maximal IL-6 response in vivo. Optimal conditions were found to be two i.p. injections of 35 to 120 micrograms IL-6 and 65 micrograms dexamethasone per kg body weight administered at 12-h intervals. Within 24 h, the plasma concentrations for alpha 2-macroglobulin, fibrinogen, thiostatin, and hemopexin were increased to levels approximating those observed in acute phase animals. These results support the notion that direct interaction of IL-6 with the liver is an essential part in initiating the hepatic acute phase reaction.

Metabolism and antiproliferative effect of the glucocorticoid antagonist RU38486 in cultured liver and hepatoma cells

In an attempt to elucidate the relationship between the antiglucocorticoid effect and the state of differentiation of the target cells, we studied the metabolism of the potent antagonist in cultured liver and hepatoma cells (HTC, FAZA). After incubation of [ 3H]RU38486 with the cells for different periods of time, the native steroid and its metabolites were extracted and analyzed by thin layer chromatography. We observed that RU38486 was not metabolized in the transformed cell lines after a 3 h incubation. In contrast RU38486 was extensively metabolized in cultured liver cells. The observed degration could help explain why RU38486 inhibited tyrosine aminotransferase induction in hepatoma cells at a concentration 100 times lower than that needed in liver cells. Moreover this catabolism concerned specifically the antagonist RU38486 since other steroids tested (dexamethasone, promegestone) underwent a much slower degradation. Indirect experiments suggest that the alterations of the RU38486 molecule might be at least partially related to the cytochrome P-450 which is very active in the hepatocytes. This study was paralleled by testing the effect of the antagonist on the growth of hepatoma cells. RU38486 exerted an antiproliferative effect in absence of serum. On the basis of the low metabolism of RU38486 and of its antiproliferative effect in hepatoma cells, one can emphasize that RU38486 might represent a potential drug for use in cancer therapy.