Comprehensive analysis of gene expression in rat and human hepatoma cells exposed to the peroxisome proliferator WY14,643.
Peroxisome proliferators (PPs) are an important class of chemicals that act as hepatic tumor promoters in laboratory rodents. The key target for PPs is the nuclear receptor peroxisome proliferator-activated receptor-alpha (PPARalpha) and these chemicals cause cancer by altering the expression of a subset of genes involved in cell growth regulation. The purpose of the present study was to utilize high-density gene expression arrays to examine the genes regulated by the potent PP Wy14,643 (50 microM, 6 h) in both rat (FaO) and human (HepG2) hepatoma cells. Treatment of FaO cells, but not HepG2, revealed the expected fatty acid catabolism genes. However, a larger than expected number of protein kinases, phosphatases, and signaling molecules were also affected exclusively in the FaO cells, including MAPK-phosphatase 1 (MKP-1), Janus-activated kinases 1 and 2 (JAK1 and 2), and glycogen synthetase kinase alpha and beta (GSKalpha and beta). The mRNA accumulation of these genes as well as the protein level for GSK3alpha, JAK1, and JAK2 and MKP-1 activity was corroborated. Due to the importance of MKP-1 in cell signaling, this induction was examined further and was found to be controlled, at least in part, at the level of the gene's promoter. Interestingly, overexpression of MKP-1 in turn affected the constitutive activity of PPARalpha. Taken together, the gene expression arrays revealed an important subset of PP-regulated genes to be kinases and phosphatases. These enzymes not only would affect growth factor signaling and cell cycle control but also could represent feedback control mechanisms and modulate the activity of PPARalpha.
Department of Veterinary Science and Center for Molecular Toxicology and Carcinogenesis, Penn State University, University Park, PA 16802, USA. jpv2@psu.edu
John P
JP
Vanden Heuvel
Dirk
D
Kreder
Benjamin
B
Belda
Daniel B
DB
Hannon
Courtney A
CA
Nugent
Katherine A
KA
Burns
Michael J
MJ
Taylor
D000818:Animals; D006528:Carcinoma, Hepatocellular / Q000201:enzymology / Q000235:genetics*; D004790:Enzyme Induction / Q000187:drug effects / Q000235:genetics; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects*; D017930:Genes, Reporter / Q000235:genetics; D006801:Humans; D020411:Oligonucleotide Array Sequence Analysis; D020025:Peroxisome Proliferators / Q000494:pharmacology*; D010744:Phosphoric Monoester Hydrolases / Q000096:biosynthesis; D011494:Protein Kinases / Q000096:biosynthesis; D011743:Pyrimidines / Q000494:pharmacology*; D012333:RNA, Messenger / Q000032:analysis; D051381:Rats; D018160:Receptors, Cytoplasmic and Nuclear / Q000096:biosynthesis; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction / Q000187:drug effects* / Q000235:genetics; D014157:Transcription Factors / Q000096:biosynthesis; D014407:Tumor Cells, Cultured
D020025:Peroxisome Proliferators; D011743:Pyrimidines; D012333:RNA, Messenger; D018160:Receptors, Cytoplasmic and Nuclear; D014157:Transcription Factors; C006253:pirinixic acid; D011494:Protein Kinases; D010744:Phosphoric Monoester Hydrolases