The cytochrome P450 family of enzymes play central roles in the oxidative metabolism of a wide range of xenobiotics, including chemicals, sterols, fatty acids and anticancer drugs.  Human CYP genes encode fifty-seven P450 proteins with numerous homolog variants in different tissues. They are highly differentially expressed in response to a variety of environmental chemicals and pharmaceuticals. 
Signosis has developed a plate-based array for profiling 20+ P450-regulated genes. By using this assay, researchers are able to compare gene expression in up to three samples on a single microtiter plate.