Modulation of Estrogen Receptor by Insulin and Its Biologic Significance

• It has been proposed that a nonsteroidal hormone such as insulin may directly exert an influence through estrogen receptors and alter the biologic behavior of steroid hormone target tissue. The implication of such a proposal is that diabetes may alter the outcome of estrogen receptor—positive tumors such as breast or endometrial carcinomas. To evaluate the effect of insulin on a receptor-positive tumor, we examined the direct effect of insulin on an estrogen receptor and its subsequent biologic effect on a receptor-positive endometrial carcinoma model in vitro and in vivo. An in vitro experiment demonstrated that when the estrogen receptor—positive cell line was grown in serum-free media with low insulin, there was a loss of intracellular receptors for estrogen. This loss of estrogen receptors was also associated with increased growth rate as reflected by increased thymidine uptake. Similarly, in vivo experiments demonstrated that a diabetic host with a high blood glucose level and a low insulin level exhibited development of growth of a receptor-negative tumor with accelerated growth rate in contrast to growth of a receptor-positive tumor with slower growth rate in a normal host with normal serum insulin and blood glucose levels. Data suggest that insulin may modulate the growth of estrogen receptor—positive tumors through its direct effect on estrogen receptors.

(Arch Surg 1986;121:1322-1325)