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A study of temporal transcriptional changes induced by a low concentration BPDE in cultured human cells

ABSTRACT: The environmental carcinogen, (±)-anti-benzo[a]pyrene-7,8-diol-9,10-epoxide (BPDE), causes bulky-adduct DNA damages, triggers certain signaling pathways, and elicits gene expression changes. Here, we focused on the temporal gene expression changes induced by a low concentration (0.05 µM) BPDE in human amnion epithelial FL cells. Differential gene expression profiles at 1, 10 and 22 h post BPDE treatment were obtained using Affymetrix HG-U133 Plus 2.0 oligonucleotide microarrays. A cohort of gene expression changes related to cell cycle progression, cell growth or apoptosis, stress response, and post-transcriptional regulation was validated with quantitative real-time RT-PCR. The alteration of several cell cycle-related genes was correlated and possibly contributed to the cell cycle arrest phenotype. Paradoxical transcriptional regulations regarding cell growth or apoptosis emerged in response to BPDE treatment, which indicated that cell fate was determined by integrated signals. The temporal transcriptional changes would be of help to clarify the molecular mechanism of cellular response to BPDE. Keywords: time course

ORGANISM(S): Homo sapiens

PROVIDER: GSE10979 | GEO | 2009/01/01

SECONDARY ACCESSION(S): PRJNA107177

REPOSITORIES: GEO

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Project description:BACKGROUND: Benzo[a]pyrene (BaP) is a widespread environmental genotoxic carcinogen that damages DNA by forming adducts. This damage along with activation of the aryl hydrocarbon receptor (AHR) induces complex transcriptional responses in cells. To investigate whether human cells are more susceptible to BaP in a particular phase of the cell cycle, synchronised breast carcinoma MCF-7 cells were exposed to BaP. Cell cycle progression was analysed by flow cytometry, DNA adduct formation was assessed by 32P-postlabeling analysis, microarrays of 44K human genome-wide oligos and RT-PCR were used to detect gene expression (mRNA) changes and Western blotting was performed to determine the expression of some proteins, including cytochrome P450 (CYP) 1A1 and CYP1B1, which are involved in BaP metabolism. RESULTS: Following BaP exposure, cells evaded G1 arrest and accumulated in S-phase. Higher levels of DNA damage occurred in S- and G2/M- compared with G0/G1-enriched cultures. Genes that were found to have altered expression included those involved in xenobiotic metabolism, apoptosis, cell cycle regulation and DNA repair. Gene ontology and pathway analysis showed the involvement of various signalling pathways in response to BaP exposure, such as the Catenin/Wnt pathway in G1, the ERK pathway in G1 and S, the Nrf2 pathway in S and G2/M and the Akt pathway in G2/M. An important finding was that higher levels of DNA damage in S- and G2/M-enriched cultures correlated with higher levels of CYP1A1 and CYP1B1 mRNA and proteins. Moreover, exposure of synchronised MCF-7 cells to BaP-7,8-diol-9,10-epoxide (BPDE), the ultimate carcinogenic metabolite of BaP, did not result in significant changes in DNA adduct levels at different phases of the cell cycle. CONCLUSIONS: This study characterised the complex gene response to BaP in MCF-7 cells and revealed a strong correlation between the varying efficiency of BaP metabolism and DNA damage in different phases of the cell cycle. Our results suggest that growth kinetics within a target-cell population may be important determinants of susceptibility and response to a genotoxic agent.

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A study of temporal transcriptional changes induced by a low concentration BPDE in cultured human cells

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