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Specific Estrogen Binding in Rat Mammary Tumors Induced by 7,12-Dimethylbenz(a)anthracene¹

The University of Rochester Cancer Center and Department of Biochemistry, The University of Rochester School of Medicine and Dentistry, Rochester, New York 14642

Experiments were undertaken with 7,12-dimethylbenz(a)anthracene-induced mammary tumors of the rat to determine whether ovarian-dependent and ovarian-independent tumors could be distinguished on the basis of differences in the estrogen binding capacity of the tumors in vitro and in vivo. Our results confirm reports showing that ovarian-dependent tumors undergo interaction between 17ß-[³H]estradiol and specific estrogen binding components both in vivo and in vitro, as described for other estrogen target tissues. However, our results also demonstrated that certain 7,12-dimethylbenz(a)anthracene-induced tumors, which continued to grow after ovariectomy of the host, contained significant amounts of 17ß-[³H]estradiol bound to cytoplasmic as well as nuclear components. The sedimentation properties of these components were indistinguishable from those of either ovarian-dependent 7,12-dimethylbenz(a)anthracene-induced tumors or rat uterus. The cytoplasmic binding components of both classes of tumors exhibited similar specificities for estrogens. There did not appear to be an absolute correlation between estrogen-binding capacity of a tumor and its growth response to ovariectomy.

¹ This work was supported in part by American Cancer Society Grant IN-18N and USPHS Grants CA-12836 and CA-11198.

² Present address: Department of Biology, Queens College of the City University of New York, Flushing, N.Y. 11367.

Received 8/ 5/74. Accepted 11/ 8/74.