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PPARalpha-dependent activation of cell cycle control and DNA repair genes in hepatic nonparenchymal cells.

ABSTRACT: Peroxisome proliferator-activated receptor-? (PPAR?) mediates the diverse biological effects of peroxisome proliferator (PP) chemicals, including fatty acid catabolism, hepatomegaly, hepatocyte proliferation, and hepatocarcinogenesis in rodents. However, transgenic mice expressing a constitutively active PPAR? in hepatocytes (VP16PPAR?) do not develop hepatocellular carcinomas in spite of hepatocyte proliferation and hepatomegaly; this suggests that activation of genes in nonparenchymal cells may have a critical role in PP-induced carcinogenesis. VP16PPAR? mice exhibited massive peroxisome proliferation and hepatomegaly as well as increased mortality upon Wy-14,643 treatment. Several genes involved in cell cycle or DNA damage repair, such as Chek1, Prkdc, Mcm, and Rad51, were significantly induced to a similar extent between wild-type and VP16PPAR? mice after Wy-14,643 administration. This induction was completely abolished in Ppar?-null mice, suggesting a PPAR?-dependent pathway. These data revealed a DNA damage response signaling network as an early event upon PP treatment and provide novel putative mechanisms for PP-induced hepatocellular carcinoma.

SUBMITTER: Qu A

PROVIDER: S-EPMC2984533 | biostudies-literature | 2010 Dec

REPOSITORIES: biostudies-literature

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PPARalpha-dependent activation of cell cycle control and DNA repair genes in hepatic nonparenchymal cells.

Qu Aijuan A Shah Yatrik M YM Matsubara Tsutomu T Yang Qian Q Gonzalez Frank J FJ

Toxicological sciences : an official journal of the Society of Toxicology 20100902 2

Peroxisome proliferator-activated receptor-α (PPARα) mediates the diverse biological effects of peroxisome proliferator (PP) chemicals, including fatty acid catabolism, hepatomegaly, hepatocyte proliferation, and hepatocarcinogenesis in rodents. However, transgenic mice expressing a constitutively active PPARα in hepatocytes (VP16PPARα) do not develop hepatocellular carcinomas in spite of hepatocyte proliferation and hepatomegaly; this suggests that activation of genes in nonparenchymal cells ma ...[more]

PMID: 20813756

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Project description:The candidate-gene approach in association studies of polygenic diseases has often yielded conflicting results. In this hospital-based case-control study with 696 white patients newly diagnosed with bladder cancer and 629 unaffected white controls, we applied a multigenic approach to examine the associations with bladder cancer risk of a comprehensive panel of 44 selected polymorphisms in two pathways, DNA repair and cell-cycle control, and to evaluate higher-order gene-gene interactions, using classification and regression tree (CART) analysis. Individually, only XPD Asp312Asn, RAG1 Lys820Arg, and a p53 intronic SNP exhibited statistically significant main effects. However, we found a significant gene-dosage effect for increasing numbers of potential high-risk alleles in DNA-repair and cell-cycle pathways separately and combined. For the nucleotide-excision repair pathway, compared with the referent group (fewer than four adverse alleles), individuals with four (odds ratio [OR] = 1.52, 95% CI 1.05-2.20), five to six (OR = 1.81, 95% CI 1.31-2.50), and seven or more adverse alleles (OR = 2.50, 95% CI 1.69-3.70) had increasingly elevated risks of bladder cancer (P for trend <.001). Each additional adverse allele was associated with a 1.21-fold increase in risk (95% CI 1.12-1.29). For the combined analysis of DNA-repair and cell-cycle SNPs, compared with the referent group (<13 adverse alleles), the ORs for individuals with 13-15, 16-17, and >or=18 adverse alleles were 1.22 (95% CI 0.84-1.76), 1.57 (95% CI 1.05-2.35), and 1.77 (95% CI 1.19-2.63), respectively (P for trend = .002). Each additional high-risk allele was associated with a 1.07-fold significant increase in risk. In addition, we found that smoking had a significant multiplicative interaction with SNPs in the combined DNA-repair and cell-cycle-control pathways (P<.01). All genetic effects were evident only in "ever smokers" (persons who had smoked >or=100 cigarettes) and not in "never smokers." A cross-validation statistical method developed in this study confirmed the above observations. CART analysis revealed potential higher-order gene-gene and gene-smoking interactions and categorized a few higher-risk subgroups for bladder cancer. Moreover, subgroups identified with higher cancer risk also exhibited higher levels of induced genetic damage than did subgroups with lower risk. There was a significant trend of higher numbers of bleomycin- and benzo[a]pyrene diol-epoxide (BPDE)-induced chromatid breaks (by mutagen-sensitivity assay) and DNA damage (by comet assay) for individuals in higher-risk subgroups among cases of bladder cancer in smokers. The P for the trend was .0348 for bleomycin-induced chromosome breaks, .0036 for BPDE-induced chromosome breaks, and .0397 for BPDE-induced DNA damage, indicating that these higher-order gene-gene and gene-smoking interactions included SNPs that modulated repair and resulted in diminished DNA-repair capacity. Thus, genotype/phenotype analyses support findings from CART analyses. This is the first comprehensive study to use a multigenic analysis for bladder cancer, and the data suggest that individuals with a higher number of genetic variations in DNA-repair and cell-cycle-control genes are at an increased risk for bladder cancer, confirming the importance of taking a multigenic pathway-based approach to risk assessment.

Dataset Information

PPARalpha-dependent activation of cell cycle control and DNA repair genes in hepatic nonparenchymal cells.

Publications

PPARalpha-dependent activation of cell cycle control and DNA repair genes in hepatic nonparenchymal cells.

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