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Identification of distinct and common gene expression changes after oxidative stress and gamma and ultraviolet
Alexandra N Heinloth1, Rodney E Shackelford, Cynthia L Innes
1Growth Control and Cancer Group, National Institute of Environmental Health Sciences, National Institutes of Health, Research Triangle Park, North Carolina 27709, USA.
Abstract:
The human genome is exposed to many different kinds of DNA-damaging agents. While most damage is detected and repaired through complex damage recognition and repair machineries, some damage has the potential to escape these mechanisms. Unrepaired DNA damage can give rise to alterations and mutations in the genome in an individual cell, which can result in malignant transformation, especially when critical genes are deregulated. In this study, we investigated gene expression changes in response to oxidative stress, gamma (gamma) radiation, and ultraviolet (UV) radiation and their potential implications in cancer development. Doses were selected for each of the three treatments, based on their ability to cause a similar G(1) checkpoint induction and slow down in early S-phase progression, as reflected by a comparable reduction in cyclin E-associated kinase activity of at least 75% in logarithmically growing human dermal diploid fibroblasts. To investigate gene expression changes, logarithmically growing dermal diploid fibroblasts were exposed to either gamma radiation (5 Gy), oxidative stress (75 microM of tert-butyl hydroperoxide (t-butyl-OOH)), or UV radiation (UVC) (7.5 J/m(2)) and RNA was harvested 6 h after treatment. Gene expression was analyzed using the NIEHS Human ToxChip 2.0 with approximately 1901 cDNA clones representing known genes and expressed sequence tags (ESTs). We were able to identify common and distinct responses in dermal diploid fibroblasts to the three different stimuli used. Within our analysis, gene expression profiles in response to gamma radiation and oxidative stress appeared to be more similar than profiles expressed after UV radiation. Interestingly, equivalent cyclin E-associated kinase activity reduction with all the three treatments was associated with greater transcriptional changes after UV radiation than after gamma radiation and oxidative stress. While samples treated with UV radiation displayed modulations of their mitogen activated protein kinase (MAPK) pathway, gamma radiation had its major influence on cell-cycle progression in S-phase and mitosis. In addition, cell cultures from different individuals displayed significant differences in their gene expression responses to DNA damage.
Insights
Human skin cells show distinct gene expression changes when exposed to oxidative stress, gamma radiation, or UV radiation. These responses, while varying, offer insights into DNA damage and potential cancer development pathways.
Area of Science:
- Genomics
- Molecular Biology
- Cancer Research
Background:
- The human genome is constantly exposed to DNA-damaging agents.
- Unrepaired DNA damage can lead to mutations and malignant transformation.
- Understanding cellular responses to different DNA-damaging agents is crucial for cancer research.
Purpose of the Study:
- To investigate gene expression changes in human dermal diploid fibroblasts in response to oxidative stress, gamma radiation, and UV radiation.
- To identify common and distinct cellular responses to these DNA-damaging agents.
- To explore the implications of these gene expression changes in cancer development.
Main Methods:
- Human dermal diploid fibroblasts were exposed to gamma radiation (5 Gy), oxidative stress (75 microM tert-butyl hydroperoxide), or UV radiation (7.5 J/m(2) UVC).
- Dose selection ensured comparable G(1) checkpoint induction and S-phase progression slowdown.
- Gene expression analysis was performed 6 hours post-treatment using the NIEHS Human ToxChip 2.0 array (~1901 genes/ESTs).
Main Results:
- Distinct and common gene expression profiles were identified across the three stimuli.
- Gamma radiation and oxidative stress induced more similar gene expression profiles compared to UV radiation.
- UV radiation treatment resulted in greater transcriptional changes than gamma radiation or oxidative stress, despite similar cell-cycle effects.
- UV radiation modulated the mitogen-activated protein kinase (MAPK) pathway, while gamma radiation primarily affected S-phase and mitosis.
- Significant inter-individual differences in gene expression responses to DNA damage were observed.
Conclusions:
- Different DNA-damaging agents elicit unique as well as shared transcriptional responses in human fibroblasts.
- UV radiation appears to induce more profound transcriptional alterations than gamma radiation or oxidative stress at equivalent cell-cycle impact levels.
- Individual genetic variations influence cellular responses to DNA damage, a factor relevant to cancer susceptibility and progression.