Expression Profiles The response of a biological system to treatment is assessed in genomic terms by measuring the treatment-induced changes in gene expression. In DrugMatrix, the first large scale toxicogenomic reference system, this is done currently by quantifying changes in mRNA levels using 10,000 gene microarrays. At Iconix we isolate RNA from both in vivo and in vitro experiments, which are carried out under carefully planned and executed protocols in replicate to ensure the reproducibility and certify that only the highest quality data reaches the reference system.

The gene expression dimension of the current version of DrugMatrix is built predominantly on in vivo rat studies from which triplicate tissue samples are collected for expression measurements in 12 different tissues at multiple time points (up to 5) and at least 2 concentrations - a high dose and a low dose.

Gene expression analysis is also performed from in vitro mammalian cellular studies under equally precise conditions so that in vivo toxicogenomic findings can be readily correlated with in vitro results.