Laboratory variability does not preclude identification of biological functions impacted by hydroxyurea.

Area of Science:

• Genomics
• Toxicology
• Molecular Biology

Background:

• Genomics applications in risk assessment are advancing.
• Inter-laboratory variability can impact gene expression analysis.
• Standardized methods are crucial for reliable toxicogenomic data.

Purpose of the Study:

• To investigate the influence of inter-laboratory variability on gene expression analysis in a toxicogenomics context.
• To identify biologically relevant gene expression changes in mouse lymphoma cells treated with hydroxyurea (HU).
• To evaluate the impact of merging data from multiple studies on statistical sensitivity.

Main Methods:

• Gene expression profiling of mouse lymphoma L5178Y cells treated with HU.
• Three independent studies from two different laboratories were analyzed.
• Cells were harvested at 4 hours post-treatment and after a 20-hour recovery period.
• Cytotoxicity and genotoxicity assays were performed.

Main Results:

• Gene expression responses differed significantly between 4 hr and 24 hr time points.
• A consistent dose-response pattern was observed across studies.
• At 4 hr, 173 dose-responsive genes related to cell cycle and DNA repair were identified.
• At 24 hr, 434 dose-responsive genes involved in lymphocyte activity and apoptosis were identified.
• Merging studies increased the number of significantly modulated genes detected.

Conclusions:

• Despite inter-laboratory variability, combining toxicogenomic datasets enhances statistical power.
• Hydroxyurea (HU) treatment induces distinct gene expression profiles related to cell cycle and apoptosis.
• The identified genes provide valuable insights into HU's biological mechanisms relevant to risk assessment.