Protein phosphatase inhibitor-1 mRNA expression correlates with neoplastic transformation of epithelial liver cells and progression of hepatocellular carcinomas.

Abstract

Protein phosphatase inhibitor-1 plays an important role in the regulation of glycogen metabolism through inhibition of protein phosphatase-1 activity, and it has been implicated in the regulation of cell growth. Using real-time quantitative RT-PCR, we studied the mRNA expression of inhibitor-1 in hepatocellular carcinomas induced in rats by oral administration of N-nitrosomorpholine, and in a non-tumorigenic liver cell line (C1I), that stores glycogen in excess during early passages. In late passages, glycogen is gradually lost concomitant with cell transformation. Our in vitro model included a tumorigenic subline of C1I cells that was obtained by chemically-induced neoplastic transformation using N-methyl-N'-nitro-N-nitrosoguanidine (C1Ict), and does not store glycogen, as well as Morris hepatoma 3924A (MH3924A) cells. We found that in hepatocellular carcinomas, in the late glycogen-poor passages (C1I(late)), and in the tumorigenic subline (C1Ict) of C1I cells, and in MH3924A cells the mRNA expression of inhibitor-1 is significantly increased. This increase in expression varied from 15 to 290-fold of that observed in normal liver. In contrast, in the early glycogen-storing passage of C1I cells (C1I(early)) the level of inhibitor-1 mRNA was found to be slightly less than that of normal liver. Inhibitor-1 mRNA levels correlated with the degree of differentiation of HCCs. These results indicate that the expression of inhibitor-1 mRNA is tightly linked to tumor progression and to the process of liver cell transformation in vitro and is inversely correlated with the glycogen content of the cell.

• Authors: Eiman Aleem, Thomas Flohr, Heinz Walter Thielmann, Peter Bannasch, Doris Mayer
• Journal: International journal of oncology (Int J Oncol) Vol. 24 Issue 4 Pg. 869-77 (Apr 2004) ISSN: 1019-6439 [Print] Greece
• PMID: 15010824 (Publication Type: Comparative Study, Journal Article)

Chemical References

• Carrier Proteins
• Intracellular Signaling Peptides and Proteins
• Liver Glycogen
• Nitrosamines
• RNA, Messenger
• protein phosphatase inhibitor-1
• N-nitrosomorpholine

Topics

• Administration, Oral
• Animals
• Carcinoma, Hepatocellular (genetics, pathology)
• Carrier Proteins (genetics)
• Cell Transformation, Neoplastic
• Disease Progression
• Epithelial Cells (drug effects, pathology)
• Gene Expression Regulation, Neoplastic
• Intracellular Signaling Peptides and Proteins
• Liver Glycogen (metabolism)
• Liver Neoplasms, Experimental (genetics, pathology)
• Male
• Nitrosamines (toxicity)
• RNA, Messenger (metabolism)
• Rats
• Rats, Sprague-Dawley