Cytochrome P450s are a multigene family of constitutive and inducible enzymes that have a central role in the oxidative metabolic activation and detoxification

Cytochrome P450 CYP1B1 is a recently cloned dioxin-inducible form of the cytochrome P450 family of xenobiotic metabolizing en zymes. An antibody raised against a peptide specific for CYP1B1 was found to recognize CYP1B1 expressed in human lymphoblastoid cells but not to recognize other forms of cytochrome P450, particularly CYP1A1 and CYP1A2. Using this antibody, the cellular distribution and localization of CYP1B1 were Investigated by immunohistochemis try in a range of malignant tumors and corresponding normal tissues. CYP1B1 was found to be expressed at a high frequency in a wide range of human cancers of different histogenetic types, Including cancers of the breast, colon, lung, esophagus, skin, lymph node, brain, and testis. There was no detectable immunostaining for CYP1B1 in normal tis sues. These results provide the basis for the development of novel methods of cancer diagnosis based on the identification of CYP1BI in tumor cells and the development of anticancer drugs that are selec tively activated in tumors by CYP1B1.