Modulation of cell proliferation and polyamine metabolism in rat liver cell cultures by the iron chelator O-trensox.

The antiproliferative effects of the iron chelator O-trensox and the ornithine-decarboxylase (ODC) inhibitor alpha-difluoromethylornithine (DFMO) were characterized in the rat hepatoma cell line FAO, the rat liver epithelial cell line (RLEC) and the primary rat hepatocyte cultures stimulated by EGF. We observed that O-trensox and DFMO decreased cell viabilty and DNA replication in the three culture models. The cytostatic effect of O-trensox was correlated to a cytotoxicity, higher than for DFMO, and to a cell cycle arrest in G0/G1 or S phases. Moreover, O-trensox and DFMO decreased the intracellular concentration of spermidine in the three models without changing significantly the spermine level. We concluded that iron, but also polyamine depletion, decrease cell growth. However, the drop in cell proliferation obtained with O-trensox was stronger compared to DFMO effect. Altogether, our data provide insights that, in the three rat liver cell culture models, the cytostatic effect of the iron chelator O-trensox may be the addition of two mechanisms: iron and polyamine depletion.

The new orally active iron chelator ICL670A exhibits a higher antiproliferative effect in human hepatocyte cultures than O-trensox.

By comparing the antiproliferative effect of the iron chelators ICL670A and O-trensox in the human hepatoma cell line HUH7 and human hepatocyte cultures, we have shown that ICL670A decreased cell viability, inhibited DNA replication and induced DNA fragmentation more efficiently than O-trensox. O-trensox and ICL670A induced a cell cycle blockade in G0-G1 and S phases respectively. In parallel, ICL670A inhibited polyamine biosynthesis by decreasing ornithine decarboxylase and spermidine/spermine N(1)-acetyltransferase activities. O-trensox increased polyamine biosynthesis and particularly putrescine level by stimulating spermidine-spermine N(1)-acetyltransferase activity which could activate the polyamine retro-conversion pathway. Moreover, the two chelators exhibit some cytotoxic effect in the two culture models; ICL670A was more cytotoxic than O-trensox and higher concentrations of the two chelators were necessary to induce a cytotoxicity in primary cultures versus hepatoma cells. These results suggested that ICL670A has the most efficient antitumoral effect, blocks cell proliferation by a pathway different of O-trensox and may constitute a potential drug for anticancer therapy.

Iron mobilization, cytoprotection, and inhibition of cell proliferation in normal and transformed rat hepatocyte cultures by the hydroxypyridinone CP411, compared to CP20: a biological and physicochemical study.

The present study analyzes the iron mobilization, the cytoprotective, and the antiproliferative effects of the lipophilic hydroxypyridinone CP411, in comparison with the hydrophilic chelator CP20 or deferiprone used in the treatment of iron overload. Primary rat hepatocyte cultures and the rat hepatoma cell line Fao were used. Chelator cell uptake was evaluated by mass spectrometry in the two models. This method was also used to investigate the stability of the chelators in an acellular system as well as their scavenging and chelating effects against the hydroxyl radical generated by the Fenton reaction. The iron mobilization and the cytoprotective effects of the chelators were evaluated in primary cultures by measuring respectively 55Fe and lactate dehydrogenase release in the culture medium. The antiproliferative effect of the chelators was studied using the Fao cell line and measuring DNA synthesis by thymidine incorporation and DNA content by flow cytometry. We observed that CP411 entered the hepatocytes and the Fao cells respectively 4 and 13 times more than CP20. CP411 was 2.5 times more effective than CP20 to mobilize iron from preloaded hepatocytes. Pretreatment of the hepatocytes with CP20 or CP411 decreased the toxic effect of iron and CP411 was 1.6 times more effective than CP20. A dose-dependent decrease of DNA synthesis, correlated to an accumulation of cells in S phase, was observed in the Fao cell line in the presence of CP411, while CP20 was without effect. CP411 effect was inhibited by addition of iron simultaneously with the chelator, the addition of Zn or Cu was without effect. The inhibitory effect of CP411 was reversible since, 24hr after removal of the chelator, DNA replication reached the control level. The results show that CP411 is more efficient to protect the hepatocyte from the toxic effect of iron load and to inhibit tumor cell proliferation. Its higher efficiency may result from its better cell uptake since equimolar solutions of the two chelators in an acellular system exhibit the same ability to inhibit the Fenton reaction.