Elevated expression of the retinoic acid-metabolizing enzyme CYP26C1 in primary breast carcinomas.

Retinoic acid (RA)-metabolizing enzyme CYP26A1 has been shown to have increased expression levels in breast cancers and to effectively promote the survival of breast carcinoma cells, implying a potential oncogenic function. However, the expression of CYP26C1, another CYP26 family member, in primary breast carcinoma remains to be clarified. In the present study, we examined the expression of CYP26C1 by immunohistochemistry, using three different types of microarray, and observed strong cytoplasmic staining of CYP26C1 in 73 of the 219 (33.3 %) breast carcinomas. In contrast, CYP26C1 was not expressed in normal ductal and lobular cells in non-neoplastic tissue. Interestingly, increased expression of CYP26C1 was significantly associated with a high Ki-67 labeling index and a grade of tumor. However, CYP26C1 immunoreactivity was not associated with clinicopathological variables, including primary tumor status, lymph node involvement, distant metastasis, and tumor stage. In addition, CYP26C1 positivity was independent of the expression status of the hormone receptors and immunohistochemical surrogates for the intrinsic subtypes of breast cancer. This report is the first to demonstrate elevated expression of CYP26C1 in primary breast carcinomas. Based on the RA-catabolizing activity of CYP26C1, our data suggest that CYP26C1 expression may contribute to neoplasia in the breast.