Further studies on aberrant gene expression associated with arsenic-induced malignant transformation in rat liver TRL1215 cells.

Abstract

Chronic arsenic exposure of rat liver epithelial TRL1215 cells induced malignant transformation in a concentration-dependent manner. To further define the molecular events of these arsenic-transformed cells (termed CAsE cells), gene expressions associated with arsenic carcinogenesis or influenced by methylation were examined. Real-time RT-PCR showed that at carcinogenic concentrations (500 nM, and to a less extent 250 nM of arsenite), the expressions of alpha-fetoprotein (AFP), Wilm's tumor protein-1 (WT-1), c-jun, c-myc, H-ras, c-met and hepatocyte growth factor, heme oxygenase-1, superoxide dismutase-1, glutathione-S-transferase-pi and metallothionein-1 (MT) were increased between 3 to 12-fold, while expressions of insulin-like growth factor II (IGF-II) and fibroblast growth factor receptor (FGFR1) were essentially abolished. These changes were not significant at the non-carcinogenic concentration (125 nM), except for IGF-II. The positive cell-cycle regulators cyclin D1 and PCNA were overexpressed in CAsE cells, while the negative regulators p21 and p16 were suppressed. Western-blot confirmed increases in AFP, WT-1, cyclin D1 and decreases in p16 and p21 protein in CAsE cells. The CAsE cells over-expressed MT but the demethylating agent 5-aza-deoxycytidine (5-aza-dC, 2.5 microM, 72 h) stimulated further MT expression. 5-Aza-deoxycytidine restored the loss of expression of p21 in CAsE cells to control levels, but did not restore the expression of p16, IGF-II, or FGFR1, indicating the loss of expression of these genes is due to factors other than DNA methylation changes. Overall, an intricate variety of gene expression changes occur in arsenic-induced malignant transformation of liver cells including oncogene activation and alterations in expression of genes critical to growth regulation.

• Authors: Jie Liu, Lamia Benbrahim-Tallaa, Xun Qian, Limei Yu, Yaxiong Xie, Jennifer Boos, Wei Qu, Michael P Waalkes
• Journal: Toxicology and applied pharmacology (Toxicol Appl Pharmacol) Vol. 216 Issue 3 Pg. 407-15 (Nov 01 2006) ISSN: 0041-008X [Print] United States
• PMID: 16876216 (Publication Type: Journal Article, Research Support, N.I.H., Intramural)

Chemical References

• Arsenites
• Carcinogens
• DNA, Neoplasm
• Intercellular Signaling Peptides and Proteins
• Decitabine
• Azacitidine
• arsenite
• Arsenic

Topics

• Animals
• Arsenic (toxicity)
• Arsenites (toxicity)
• Azacitidine (analogs & derivatives, toxicity)
• Blotting, Western
• Carcinogens
• Cell Cycle (drug effects, genetics)
• Cell Line
• Cell Transformation, Neoplastic (drug effects)
• DNA, Neoplasm (metabolism)
• Dealkylation
• Decitabine
• Gene Expression (drug effects)
• Gene Expression Regulation, Developmental (drug effects)
• Gene Expression Regulation, Neoplastic (drug effects)
• Growth (genetics)
• Intercellular Signaling Peptides and Proteins (biosynthesis, genetics)
• Liver Neoplasms (chemically induced, genetics)
• Rats
• Reverse Transcriptase Polymerase Chain Reaction
• Stress, Physiological (genetics)