Expression profile of arsenic-responsive genes. (Left) Gene symbols, UniGene numbers, and change ratios of expression as revealed by microarray analysis of the 26 highly responsive genes for RT-PCR after hydrogen peroxide treatment or NAC rescue experiment. Three genes, denoted with asterisks, were not changed more than 6-fold; hence, they are omitted from the heat map. u indicates up-regulated; d, down-regulated. (Right) Heat map demonstrating the arsenicinduced changes in expression (at least 6-fold) of 106 down-regulated and 177 up-regulated genes.