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Identification, Subcellular Localization, and Estrogen Regulation of Peroxidase in 7,12-Dimethylbenz(a)anthracene-induced Rat Mammary Tumors¹

The Ben May Laboratory for Cancer Research [E. R. D.], and the Laboratory for Cellular and Reproductive Biology, Department of Anatomy [W. A. A., Y. K.], Biomedical Center for Population Research, The University of Chicago, Chicago, Illinois 60637

An estrogen-induced, intensely staining peroxidase 3,3'-diaminobenzidine-positive reaction product is found to be characteristic of hormone-dependent, 7,12-dimethylbenz-(a)anthracene-induced mammary tumors of the rat. This product is demonstrated in thick sections of such tumors from intact or estrogen-treated castrate rats but is not seen in tumors that are in regression due to castration or estrogen deprivation. It is, furthermore, absent from tumors whose growth is unaffected by castration. The subcellular localization of this enzyme activity is restricted mainly to the nuclear envelope and cisternae of the granular endoplasmic reticulum in addition to secretory granules. This provides the first evidence for a criterion that would allow differentiation of hormone-dependent and hormone-independent mammary cancer on histological sections and, as such, may have considerable potential as an aid in the classification of human breast cancer.

¹ The research was supported in part by Contract No. 1-CB-23873 from the Breast Cancer Task Force, National Cancer Institute, and in part by Grant M73.109 from the Population Council, Rockefeller Foundation; USPHS Grant HD 07110; and The University of Chicago Cancer Center Grant CA 14599-01.

² Recipient of Research Career Development Award HD 46249 from National Institute for Child Health and Human Development. To whom reprint requests should be addressed, at The Ben May Laboratory for Cancer Research, 950 E. 59th Street, Chicago, Ill. 60637.

³ Postdoctoral fellow supported by the Developmental Biology Training Grant (USPHS 5 to 1-DH00297).

Received 5/13/74. Accepted 10/ 3/74.