Further studies on aberrant gene expression associated with arsenic-induced malignant transformation in rat liver TRL1215 cells.
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.
Liu
Jie
J
Inorganic Carcinogenesis Section, Laboratory of Comparative Carcinogenesis, NCI at NIEHS, Mail Drop F-09, Research Triangle Park, NC 27709, USA. Liu6@niehs.nih.gov
Benbrahim-Tallaa
Lamia
L
Qian
Xun
X
Yu
Limei
L
Xie
Yaxiong
Y
Boos
Jennifer
J
Qu
Wei
W
Waalkes
Michael P
MP
D000818:Animals; D001151:Arsenic / Q000633:toxicity*; D018053:Arsenites / Q000633:toxicity; D001374:Azacitidine / Q000031:analogs & derivatives / Q000633:toxicity; D015153:Blotting, Western; D002273:Carcinogens; D002453:Cell Cycle / Q000187:drug effects / Q000235:genetics; D002460:Cell Line; D002471:Cell Transformation, Neoplastic / Q000187:drug effects*; D004273:DNA, Neoplasm / Q000378:metabolism; D003640:Dealkylation; D000077209:Decitabine; D015870:Gene Expression / Q000187:drug effects; D018507:Gene Expression Regulation, Developmental / Q000187:drug effects; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects*; D006128:Growth / Q000235:genetics; D036341:Intercellular Signaling Peptides and Proteins / Q000096:biosynthesis / Q000235:genetics; D008113:Liver Neoplasms / Q000139:chemically induced* / Q000235:genetics*; D051381:Rats; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013312:Stress, Physiological / Q000235:genetics
D018053:Arsenites; D002273:Carcinogens; D004273:DNA, Neoplasm; D036341:Intercellular Signaling Peptides and Proteins; D000077209:Decitabine; D001374:Azacitidine; C015001:arsenite; D001151:Arsenic