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Temporal gene expression analysis of mouse Hepa-1c1c7 cells treated with 17beta-estradiol by cDNA microarray. C.J. Fong1,3,4, L.D. Burgoon2,3,4, R Gupta1,4, DG Humes1,4, T.R. Zacharewski1,3,4. 1Department of Biochemistry & Molecular Biology, 2Department of Pharmacology & Toxicology, 3Center for Integrative Toxicology, 4National Food Safety and Toxicology Center, Michigan State University, East Lansing, MI, 48824, USA. cDNA microarrays, containing 6376 clones representing 4858 unique genes, were used to examine temporal changes in gene expression in the mouse Hepa-1c1c7 hepatoma cell line upon treatment with 17beta-estradiol (E2) in a serum free environment. MTT and direct cell count assays indicated that cells were viable, and were harvested at 1, 2, 4, 8, 12, 24, and 48 hours after treatment with 10 nM E2 or DMSO vehicle. Model-based tstatistical analysis identified significant changes in the expression of 213 unique genes representing functions associated with lipid metabolism, glucose metabolism and oxidative stress and the major temporal patterns may be visualized by seven k-means clusters. Upregulation of LDL receptor genes (Vldlr, Sorl1), down-regulation of HDL receptor (Scarb1) and the induction of the cholesterol-ester synthesis gene (Soat1) are observed and all are consistent with the decrease of LDL/HDL ratios elicited by estrogens. Comparisons with an in vivo time course show a good correlation between models for these genes indicating that extrapolations from the in vitro model may be cell-line specific for certain pathways. Estrogenic regulation of the hepatic liver X receptor (LXR), a cholesterol regulator, may be a contributing factor of activating these events. In DMSO treated cells only 95 unique genes exhibited early changes in expression representing functions associated with cell proliferation, solute homeostasis and xenobiotic metabolism which were adequately described by two k-means clusters. Additional characterization of the Hepa-1c1c7 cells also show that serum-free conditions significantly reduce their proliferative rate while changes in basal gene expression increase with increased sub-culturing. Research Supported By R01 ES11271 |
