An abridged history of sex steroid hormone receptor action.

The field of steroid hormone action is well established, although it is barely more than four decades old. Pivotal experiments in the late 1950s and 1960s showed that hormone-binding components exist within nuclei of target tissues and that steroid hormones act by regulating gene expression, rather than directly influencing enzymatic processes. The understanding that steroid hormone receptors interact with the general transcription machinery and alter chromatin structure came in the 1970s and 1980s, and details of this mechanism continue to be elucidated. In addition, the discovery of rapid cellular responses to steroid hormones has led to the identification of putative membrane-bound steroid receptors that act without affecting gene transcription. As noted in the recent Institute of Medicine report "Exploring the Biological Contributions to Human Health: Does Sex Matter?", the effects of steroid hormones and defects in steroid hormone receptor action have a profound impact on human health and disease. Future research directives include the development of potent, selective steroid receptor modulators, the elucidation of nongenomic steroid hormone effects, and further exploration of hormone-genome interactions.

Women subjects in NIH-funded clinical research literature: lack of progress in both representation and analysis by sex.

The National Institutes of Health (NIH) issued guidelines in 1990 requiring the inclusion of women and minorities in all NIH-sponsored clinical research and revised these guidelines in 1994 to require analysis of clinical trial outcomes by sex of the subjects. To ascertain whether these guidelines are yet reflected in the scientific literature, we performed a survey of research articles published in major medical journals. All original research articles in the New England Journal of Medicine, the Journal of the American Medical Association, the Journal of the National Cancer Institute, and Circulation from the years 1993, 1995, 1997, and 1998 were examined. Articles were assessed for use of human subjects, source of funding, type of study (clinical trial or not), sex-relatedness of the disease or condition, inclusion of women as study subjects, and analysis of outcomes by sex of the subjects. Among NIH-funded, non-sex-specific studies, approximately one fifth of the studies published each year failed to include women as research subjects. This number did not improve significantly over the 5-year period analyzed. Only one quarter to one third of the studies that included women analyzed data by sex of the subjects, with no significant change over the time period studied. Although most clinical trials included women as study subjects, in only a small percentage of the trials were results analyzed by sex of the subjects, with no significant improvement over time. These data clearly show the need for increased awareness and monitoring of recruitment and retention of women in clinical research and for analysis of data by sex of the subjects to be carried out consistently.

A comparison of the effects of castration and 6-methylene progesterone, a 5 alpha-reductase inhibitor, on the rat ventral prostate.

6-Methylene progesterone (6MP) is an irreversible in vitro kcat inhibitor of rat prostate 5 alpha-reductase, the enzyme which converts testosterone (T) to dihydrotestosterone (DHT). Treatment of adult rats with 6MP or diethylstilbestrol (DES) decreased the weight of the ventral prostate (VP) by 45%, while castration reduced it by 86%. Histologically, the 6MP-treated VP were indistinguishable from those of controls, while the VP from DES-treated rats showed fibrous stromal hypertrophy as in castrated rats. The prostatic hydroxyproline content, an index of collagen levels, was enhanced by castration or DES, but was not significantly increased by 6MP. Within 2 days of 6MP treatment, the 5 alpha-reductase activity was reduced by 46% and ornithine decarboxylase (ODC) activity was lowered by 27%. During this time the prostatic acid phosphatase activity increased 42% and remained elevated with continued exposure to 6MP up to 13 days. The castration-induced involution of the VP was accompanied by a reduction in serum T and an increase in serum luteinizing hormone (LH). 6MP had no effect on T and LH serum levels but reduced the DHT content within the VP by 64%. Our results indicate that the structure and secretory acid phosphatase activity of the VP are less sensitive to changes in the ratio of T:DHT than is cell proliferation. Thus, the relative amounts of DHT and T within the VP may prove to be more significant than the absolute amount of either androgen in controlling prostate growth or its attendant neoplasms.

Aromatase activity in microsomes from rat ventral prostate and Dunning R3327H rat prostatic adenocarcinoma.

We have measured aromatase activity in microsomes obtained from rat ventral prostate, using the 3H2O release method as described by Weisz. Production of 3H2O from 1 beta-[3H]androstenedione correlated with estrogen production measured by RIA and by TLC. The assay was optimized for incubation time and protein concentration, and used to determine the aromatase activity of ventral prostate microsomes from rats of varying age. Aromatase activity per mg microsomal protein increased from an average of 4 pmol/mg protein X h in 3-month old rats to 68 pmol/mg protein X h in 8-month old rats. Aromatase activity was also measured in microsomes from the Dunning R3327H rat prostatic adenocarcinoma, and was increased in tumors removed 225 days after implantation compared to tumors removed 141 days after implantation. Tumors removed 225 days after implantation from rats which had been treated with DES for 14 days displayed increased aromatase activity compared to untreated tumors. The presence of aromatase activity in the rat ventral prostate and rat prostatic adenocarcinoma would allow regulation of estrogen levels independent of circulating estrogen. Thus, in situ changes in estrogen production with age may contribute to the development of prostatic disease.

Approaches to prostatic cancer chemotherapy using the Dunning R3327H prostatic adenocarcinoma.

Androgen-responsive cells: To determine if testosterone or dihydrotestosterone is the main trophic hormone of prostatic adenocarcinoma, we have treated Dunning R3327H prostatic adenocarcinoma-bearing rats with 6-methylene progesterone, which blocks conversion of testosterone to dihydrotestosterone. Copenhagen-Fisher rats were treated with steroid (20 mg/Kg daily) immediately following implantation of tumor and thereafter for 117 days. There was a 92% inhibition of growth of tumors and a lesser effect upon prostate and seminal vesicles. Tumor-free body weights remained unchanged. Both treated and untreated tumors had equivalent DNA content on a per weight basis. This result supports the thesis that prostatic adenocarcinoma requires dihydrotestosterone for growth. Androgen-insensitive cells: Advanced prostate cancer does not respond to endocrine therapy but is temporarily controlled by the cytotoxic steroid estramustine. The latter shows significant selective binding to prostatic protein. To develop chemotherapeutic agents that will control androgen-insensitive cells and possess improved selectivity for prostatic protein, we have studied a number of steroids for their ability to displace 3H-labeled estramustine from prostatic cytosolic proteins. Surprisingly, a carbamido substituent at the C17 position was found to confer significant binding affinity for prostatic estramustine-binding protein. Extension of this structural characteristic to the estramustine type of molecule is being studied.

Endocrine dependence of prostatic cancer upon dihydrotestosterone and not upon testosterone.

Growth of the Dunning R3327-H prostatic adenocarcinoma, implanted in the rat, is inhibited by 6-methylene progesterone. This compound is a potent inhibitor of rat prostatic 5-alpha-reductase and in-vivo produced marked involution of the prostate. Thus the tumor requires dihydrotestosterone and not testosterone for growth.