Correlation of each of the six transcription factors with each of the antioxidant or DNA repair genes was determined by Pearson's correlation following logarithmic transformation. The transformation was necessary due to the wide biological variation in expression of each gene among the individuals. Significance level was defined as p < 0.01 following Bonferroni adjustment for multiple comparison, specifically comparison of each of six transcription factors to each of the antioxidant or DNA repair genes. Comparison for significant differences between pairs of correlation coefficients was done by Fisher's Z-transformation test [16].