Immunohistochemical localization of cytochrome P450CYP1B1 in breast cancerwith monoclonal antibodies specific for CYP1B1

Cytochrome P450 CYP1B1 is a recently identified member of the CYP1 P450 fam ily. We have shown that this P450 displays increased expression in several types of human cancer, indicating that CYP1B1 is a potential tumor biomarke r. In this study we developed monoclonal antibodies (MAbs) to CYP1B1 that a re effective on formalin-fixed, paraffin-embedded tissue sections and inves tigated the presence of CYP1B1 in a series of primary breast cancers. The M Abs were generated using a synthetic peptide coupled to carrier protein as the immunogen. The MAbs specifically recognized CYP1B1 and did not recogniz e either CYP1A1 or CYP1A2, related CYP1 forms. The MAbs were tested by immu nohistochemistry and were found to be effective on formalin-fixed, paraffin -embedded tissue sections. The majority of breast cancers showed positive i mmunoreactivity for CYP1B1, and in each case CYP1B1 was specifically locali zed to tumor cells. The presence of CYP1B1 in breast cancer cells is likely to contribute to their metabolism of estradiol because CYP1B1 is a specifi c estradiol hydroxylase.