Large numbers and large quantities of endocrine-disrupting chemicals have been released into the environment since World War II. Many of these chemicals can disturb development of the endocrine system and of the organs that respond to endocrine signals in organisms indirectly exposed during prenatal and/or early postnatal life; effects of exposure during development are permanent and irreversible. The risk to the developing organism can also stem from direct exposure of the offspring after birth or hatching. In addition, transgenerational exposure can result from the exposure of the mother to a chemical at any time throughout her life before producing offspring due to persistence of endocrine-disrupting chemicals in body fat, which is mobilized during egg laying or pregnancy and lactation. Mechanisms underlying the disruption of the development of vital systems, such as the endocrine, reproductive, and immune systems, are discussed with reference to wildlife, laboratory animals, and humans.

Developmental effects of endocrine-disrupting chemicals in wildlife and humans.

International variations in cancer rates have been attributed, at least in part, to differences in dietary intake. Recently, it has been suggested that consumption of soyfoods may contribute to the relatively low rates of breast, colon, and prostate cancers in countries such as China and Japan. Soybeans contain a number of anticarcinogens, and a recent National Cancer Institute workshop recommended that the role of soyfoods in cancer prevention be investigated. In this review, the hypothesis that soy intake reduces cancer risk is considered by examining relevant in vitro, animal, and epidemiological data. Soybeans are a unique dietary source of the isoflavone genistein, which possesses weak estrogenic activity and has been shown to act in animal models as an antiestrogen. Genistein is also a specific inhibitor of protein tyrosine kinases; it also inhibits DNA topoisomerases and other critical enzymes involved in signal transduction. In vitro, genistein suppresses the growth of a wide range of can...

Soy intake and cancer risk: A review of the in vitro and in vivo data

Therapy for advanced prostate cancer centers on suppressing systemic androgens and blocking activation of the androgen receptor (AR). Despite anorchid serum androgen levels, nearly all patients develop castration-resistant disease. We hypothesized that ongoing steroidogenesis within prostate tumors and the maintenance of intratumoral androgens may contribute to castration-resistant growth. Using mass spectrometry and quantitative reverse transcription-PCR, we evaluated androgen levels and transcripts encoding steroidogenic enzymes in benign prostate tissue, untreated primary prostate cancer, metastases from patients with castration-resistant prostate cancer, and xenografts derived from castration-resistant metastases. Testosterone levels within metastases from anorchid men [0.74 ng/g; 95% confidence interval (95% CI), 0.59-0.89] were significantly higher than levels within primary prostate cancers from untreated eugonadal men (0.23 ng/g; 95% CI, 0.03-0.44; P < 0.0001). Compared with primary prostate tumors, castration-resistant metastases displayed alterations in genes encoding steroidogenic enzymes, including up-regulated expression of FASN, CYP17A1, HSD3B1, HSD17B3, CYP19A1, and UGT2B17 and down-regulated expression of SRD5A2 (P < 0.001 for all). Prostate cancer xenografts derived from castration-resistant tumors maintained similar intratumoral androgen levels when passaged in castrate compared with eugonadal animals. Metastatic prostate cancers from anorchid men express transcripts encoding androgen-synthesizing enzymes and maintain intratumoral androgens at concentrations capable of activating AR target genes and maintaining tumor cell survival. We conclude that intracrine steroidogenesis may permit tumors to circumvent low levels of circulating androgens. Maximal therapeutic efficacy in the treatment of castration-resistant prostate cancer will require novel agents capable of inhibiting intracrine steroidogenic pathways within the prostate tumor microenvironment.

https://cancerres.aacrjournals.org/content/canres/68/11/4447.full.pdf

Maintenance of Intratumoral Androgens in Metastatic Prostate Cancer: A Mechanism for Castration-Resistant Tumor Growth

Incidences of breast, colorectal and prostate cancer are high in the Western world compared to countries in Asia. We have postulated that the Western diet compared to the semivegetarian diet in some Asian countries may alter hormone production, metabolism or action at the cellular level by some biochemical mechanisms. Our interest has been focused on two groups of hormone-like diphenolic phyto-oestrogens of dietary origin, the lignans and isoflavonoids abundant in plasma of subjects living in areas with low cancer incidence. The precursors of the biologically active compounds detected in man are found in soybean products, whole-grain cereal food, seeds, and berries. The plant lignan and isoflavonoid glycosides are converted by intestinal bacteria to hormone-like compounds. The weakly oestrogenic diphenols formed influence sex-hormone production, metabolism and biological activity, intracellular enzymes, protein synthesis, growth factor action, malignant cell proliferation, differentiation, cell adhesion and angiogenesis in such a way as to make them strong candidates for a role as natural cancer-protective compounds. Their effect on some of the most important steroid biosynthetic enzymes may result in beneficial modulation of hormone concentrations and action in the cells preventing development of cancer. Owing to their oestrogenic activity they reduce hot flushes and vaginal dryness in postmenopausal women and may to some degree inhibit osteoporosis, but alone they may be insufficient for complete protection. Soy intake prevents oxidation of the low-density lipoproteins in vitro when isolated from soy-treated individuals and affect favourably plasma lipid concentrations. Animal experiments provide evidence suggesting that both lignans and isoflavonoids may prevent the development of cancer as well as atherosclerosis. However, in some of these experiments it has not been possible to separate the phyto-oestrogen effect from the effect of other components in the food. The isoflavonoids and lignans may play a significant inhibitory role in cancer development particularly in the promotional phase of the disease, but recent evidence points also to a role in the initiation stage of carcinogenesis. At present, however, no definite recommendations can be made as to the dietary amounts needed for prevention of disease. This review deals with all the above-mentioned aspects of phyto-oestrogens.

Phyto-oestrogens and Western Diseases

The Analysis of Variance.

J.M. Orth: Cell biology of testicular development in the fetus and neonate P.N. Goodfellow et al: Molecular genetics of the human and mouse Y-chromosome J.R. McCarrey: Development of the germ cell C.E. Chubb: Genetic control of spermatogenesis and steroidogenesis P.K. Donahoe: Mullerian inhibiting substance C. Desjardins: Design and function of the microcirculation L.L. Ewing: Leydig cell: structure/function B.R. Zirkin: Regulation of spermatogenesis in the adult mammal: gonadotropins and androgens C.W. Bardin, G.L. Gunsalus & C.Y. Cheng: The cell biology of the sertoli cell D.M. Robertson, G.P. Risbridger & D.M. de Kretser: Inhibin and inhibin-related proteins B.T. Hinton & T.T. Turner: The seminiferous tubular microenvironment M.L. Meistrich & M.E.A.B. van Beek: Spermatogonial stem cells H. Stern: The process of meiosis Y. Clermont, R. Oko & L. Hermo: Cell biology of mammalian spermiogenesis W.W. Wright: Cellular interactions in the seminiferous epithelium N. Hecht: Gene expression during male germ cell development D.J. Wolgemuth et al: Patterns of expression and potential functions of cellular oncogenes and heat shock protein genes during germ cell development D.G. Myles: Sperm cell surface proteins of testicular origin: expression and localization in the testis and beyond K.S.K. Tung: Regulation of autoimmune disease.

Cell and molecular biology of the testis

The objective of this study was to determine whether postnatal increases in rat Leydig cell number result from differentiation of precursor cells, division of existing Leydig cells, or both. Our approach was 1) to examine changes in the absolute number of Leydig cells and potential precursor cells (macrophages, pericytes, and mesenchymal, endothelial, and myoid cells) per testis on day 19 of gestation (day -2) and days 7, 14, 21, 28, and 56 postpartum; 2) to examine the frequency with which mesenchymal and Leydig cells divide during prenatal and postnatal development; and 3) to identify and examine the fate of the progeny of Leydig and mesenchymal cell divisions during prenatal and postnatal development. Stereological methods were used to show that mesenchymal cells comprised 44% of the total interstitial cell population and Leydig cells 16% on day -2, whereas by day 56 postpartum the relationship had reversed; mesenchymal cells comprised 3% and Leydig cells 49%. These results suggested a precursor-product relationship between mesenchymal and Leydig cells because no such reciprocal relationship was observed between Leydig cells and macrophages, pericytes, endothelial, or myoid cells. Autoradiographic analysis of [3H]thymidine incorporation into mesenchymal and Leydig cells was consistent with this interpretation. In a series of pulse-chase experiments, the percentage of labeled mesenchymal and Leydig cells was measured after a single injection of [3H]thymidine on days 2, 14, 28, and 56 postpartum, each followed by sampling at timed intervals (between 1 h and 14 days) thereafter. Starting on day 14, the percentage of labeled Leydig cells was approximately 1% immediately after injection of [3H]thymidine and increased significantly to approximately 6% by 6 days after injection. No such increase was observed when rats were similarly injected starting on days 2, 28, and 56 postpartum. The rise in Leydig cell labeling between days 14 and 28 postpartum did not result in a decline in the number of silver grains over labeled Leydig cell nuclei, indicating that the increase in the percentage of labeled cells was not caused by Leydig cell division. These observations led us to conclude that the increase in Leydig cell labeling from days 14 to 28 was the result of recruitment from a compartment of labeled mesenchymal cells. In contrast, our analysis indicated that from day 28 postpartum and thereafter until the mature number of Leydig cells is attained, Leydig cells are generated by division of morphologically recognizable Leydig cells.

Kinetic studies on the development of the adult population of Leydig cells in testes of the pubertal rat.

Adult anesthetized male rats were submitted to in vivo micropuncture of the seminiferous and epididymal tubules and reproductive tract vasculature to obtain fluids for analysis of testosterone, 5α-dihydrotestosterone, and androgenbinding protein (ABP). Androgen and ABP concentrations were determined by RIA. The highest concentrations of testosterone (73.14 ± 5.12 ng/ml) were in testicular interstitial fluid. A significant downhill concentration gradient exists between testosterone concentrations in testicular interstitial fluid and seminiferous tubule fluid (50.24 ± 2.26 ng/ml); another significant decrease occurs between seminiferous tubule fluid and rete testis fluid (17.85 ± 2.11 ng/ml). 5α-Dihydrotestosterone concentrations were highest in intraluminal caput epididymidal fluids (58.73 ± 6.48 ng/ml) as were ABP concentrations (33.30 ± 2.40 μleq/μl). Intraluminal sperm concentrations were also determined, and from these data, fluid reabsorption by the efferent ducts and epididymal tubules were calculate...

On the Androgen Microenvironment of Maturing Spermatozoa

Depriving rats of luteinizing hormone (LH) causes Leydig cells to lose smooth endoplasmic reticulum and diminishes their P450 C17-hydroxylase/C17,20-lyase activity (Wing et al., 1984). LH administration to hypophysectomized rats prevents these changes in Leydig cell structure and function (Ewing and Zirkin, 1983). We adopted a multistep procedure of rat Leydig cell isolation to study the trophic effects of LH on steroidogenesis in the Leydig cell. Our method employs vascular perfusion, enzymatic dissociation, centrifugal elutriation, and Percoll gradient centrifugation. The purified Leydig cell fraction obtained after Percoll density-gradient centrifugation contains 95% well-preserved 3 beta-hydroxysteroid dehydrogenase (3 beta-HSD)-staining cells with ultrastructural characteristics of Leydig cells. These Leydig cells produced 248 and 29 ng of testosterone/10(6) Leydig cells when incubated for 3 h with and without a maximally stimulating concentration of ovine LH. Purified Leydig cells obtained from control rats and rats treated with testosterone-estradiol (T-E) implants for 4 days to inhibit LH production were incubated with a saturating concentration (2 microns) of pregnenolone. Leydig cells from control and T-E-implanted rats produced 537 and 200 ng of testosterone/10(6) Leydig cells X 3 h, respectively, suggesting a defect in the steroidogenic reactions converting pregnenolone to testosterone in Leydig cells from T-E-implanted rats. By using rabbit antibodies to the P450 C17-hydroxylase/C17,20-lyase pig microsomal enzyme, immunoblots of one-dimensional sodium dodecyl sulfate polyacrylamide gels of Leydig cell microsomal protein from control and 4- and 12-day T-E implanted rats revealed a continued loss of enzyme as the period of LH withdrawal continues. These results show that Leydig cells from animals deprived of LH had diminished capacity to convert pregnenolone to testosterone and reduced P450 C17-hydroxylase/C17,20-lyase content.

Effect of luteinizing hormone deprivation in situ on steroidogenesis of rat Leydig cells purified by a multistep procedure.

The studies described herein were designed to examine whether there is a threshold concentration of testosterone (T) within the seminiferous tubules that is required to maintain spermatogenesis in the rat, or alternatively, whether there is a dose-response relationship between the intratesticular T concentration and the maintenance of spermatogenesis. T was administered to intact adult male rats via sustained release polydimethylsiloxane capsules in order to experimentally clamp T at well defined concentrations within the seminiferous tubules. Implantation of T-filled capsules of increasing sizes resulted in linear increases in T concentrations in serum, interstitial fluid, and seminiferous tubule fluid (STF). We examined the effect of step decreases in intratesticular T concentration on the numbers of advanced spermatogenic cells maintained by the testis over a 2-month period. Quantitatively complete spermatogenesis was maintained despite an 80% reduction in the STF T concentration (to approximately 13 ng/ml) from control values. The ability of the testis to maintain complete spermatogenesis was extremely sensitive to further decreases in STF T concentration. Thus, reduction of the STF T concentration from approximately 13 to 9 ng/ml resulted in a reduction in the number of advanced spermatids that were maintained in the testis by approximately 100 x 10(6). Reduction of the STF T concentration to approximately 4 ng/ml resulted in a further reduction in the number of advanced spermatids per testis by 100 x 10(6). Taken together, these data support the contention that there is far more T present within the seminiferous tubules of intact rat testes than is required to maintain quantitatively normal spermatogenesis and reveal for the first time that there is a dose-response relationship between the STF T concentration and the quantitative maintenance of advanced spermatogenic cells in the rat testis.

Larry L. Ewing

Papers

Cell and molecular biology of the testis

Kinetic studies on the development of the adult population of Leydig cells in testes of the pubertal rat.

On the Androgen Microenvironment of Maturing Spermatozoa

Effect of luteinizing hormone deprivation in situ on steroidogenesis of rat Leydig cells purified by a multistep procedure.

Maintenance of advanced spermatogenic cells in the adult rat testis: quantitative relationship to testosterone concentration within the testis.