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Hormone Binding by Human Mammary Carcinoma¹

Department of Physiology, University of Manitoba, Winnipeg, Canada R3K OW3

The specific binding of labeled porcine insulin, human prolactin, and human growth hormone was studied in 63 human breast tumors and 15 nonmalignant breast tissues. Most (90%) of the tumors demonstrated significant binding of insulin, as did 80% of nonmalignant tissues. Autoradiographic studies indicated that insulin bound dominantly to tumor cells, rather than to fat and fibrous tissue contained within tumors. Specific binding of prolactin and growth hormone of greater than 1% was seen in 20 and 12% of tumors, respectively, and one tumor studied in detail showed a small amount of saturable, high-affinity prolactin binding. The affinity of binding of insulin and prolactin to tumor was similar to that seen in target tissues in subprimate species (K_d = 4 x 10^–10 M), but the prolactin-binding capacity in the one tumor studied in detail was very low (10 fmoles/mg membrane protein), compared with prolactin-responsive experimental mammary carcinoma.

¹ Supported by the Medical Research Council of Canada, and in part by NIH Child Health and Human Development Grant R01 HD07843.

² Medical Research Council of Canada Research Fellow. To whom reprint requests should be addressed at the Department of Endocrinology, Auckland Hospital, Auckland 1, New Zealand.

Received 11/23/76. Accepted 3/23/77.