Are estrogens carcinogenic during development of the testes?

Role of endocrine disruptors in male infertility and impact of COVID-19 on male reproduction

Several epidemiological studies suggest strong association of endocrine disruptors (EDs) with impaired male reproduction. High levels of polychlorinated biphenyls in serum are associated with low sperm count and poor fertility. A high dichloro diphenyl trichloroethane (DDT) concentration results in low serum testosterone (T) and poor semen quality. DDT stimulates estrogen production by acting as estrogen receptor agonist and potent androgen receptor antagonist. Phthalates, another group of EDs, induce seminiferous tubule degeneration with impaired spermatogenesis via disruption of gene expression that regulates cholesterol and lipid homeostasis resulting in low T. Bisphenol A, a strong exogenous estrogen with antiandrogen effect, lowers serum follicle-stimulating hormone, luteinizing hormone, and T, resulting in impaired development of seminiferous tubules and spermatogenesis. Di(2-ethylhexyl) phthalates can exert their antiandrogenic action by directly inhibiting testosterone biosynthesis via cytochrome P-450 dysfunction. Since these EDs are commonly found in plastic bottles, cosmetics, pesticides, some metal food cans, etc., and accumulate in the environment, it is very important to observe caution and avoid their exposure. This updated chapter also reviews the impact of COVID-19-related infection on male reproduction.

Untangling the association between environmental endocrine disruptive chemicals and the etiology of male genitourinary cancers

Endocrine disrupting chemicals disrupt normal physiological function of endogenous hormones, their receptors, and signaling pathways of the endocrine system. Most endocrine disrupting chemicals exhibit estrogen/androgen agonistic and antagonistic activities that impinge upon hormone receptors and related pathways. Humans are exposed to endocrine disrupting chemicals through food, water and air, affecting the synthesis, release, transport, metabolism, binding, function and elimination of naturally occurring hormones. The urogenital organs function as sources of steroid hormones, are targeted end organs, and participate within systemic feedback loops within the endocrine system. The effects of endocrine disruptors can ultimately alter cellular homeostasis leading to a broad range of health effects, including malignancy. Human cancer is characterized by uncontrolled cell proliferation, mechanisms opposing cell-death, development of immortality, induction of angiogenesis, and promotion of invasion/metastasis. While hormonal malignancies of the male genitourinary organs are the second most common types of cancer, the molecular effects of endocrine disrupting chemicals in hormone-driven cancers has yet to be fully explored. In this commentary, we examine the molecular evidence for the involvement of endocrine disrupting chemicals in the genesis and progression of hormone-driven cancers in the prostate, testes, and bladder. We also report on challenges that have to be overcome to drive our understanding of these chemicals and explore the potential avenues of discovery that could ultimately allow the development of tools to prevent cancer in populations where exposure is inevitable.

Prostate cancer stem cells: the role of androgen and estrogen receptors

Prostate cancer is one of the most commonly diagnosed cancers in men, and androgen deprivation therapy still represents the primary treatment for prostate cancer patients. This approach, however, frequently fails and patients develop castration-resistant prostate cancer, which is almost untreatable.

Cancer cells are characterized by a hierarchical organization, and stem/progenitor cells are endowed with tumor-initiating activity. Accumulating evidence indicates that prostate cancer stem cells lack the androgen receptor and are, indeed, resistant to androgen deprivation therapy. In contrast, these cells express classical (α and/or β) and novel (GPR30) estrogen receptors, which may represent new putative targets in prostate cancer treatment.

In the present review, we discuss the still-debated mechanisms, both genomic and non-genomic, by which androgen and estradiol receptors (classical and novel) mediate the hormonal control of prostate cell stemness, transformation, and the continued growth of prostate cancer. Recent preclinical and clinical findings obtained using new androgen receptor antagonists, anti-estrogens, or compounds such as enhancers of androgen receptor degradation and peptides inhibiting non-genomic androgen functions are also presented. These new drugs will likely lead to significant advances in prostate cancer therapy.

Sperm Aneuploidy in Faroese Men with Lifetime Exposure to Dichlorodiphenyldichloroethylene (p,p´-DDE) and Polychlorinated Biphenyl (PCB) Pollutants

BACKGROUND

Although it is known that sperm aneuploidy contributes to early pregnancy losses and congenital abnormalities, the causes are unknown and environmental contaminants are suspected.

OBJECTIVES

Our goal was to evaluate associations between lifetime exposure to organochlorines, specifically dichlorodiphenyldicholorethylene (p,p´-DDE) and polychlorinated biphenyls (PCBs), and sperm aneuploidy in men from the general population of the Faroe Islands, a population with a known history of organochlorine exposures.

METHODS

Serum and semen samples from men (n = 90) 22-44 years old who participated in Faroe Islands health studies were analyzed for p,p´-DDE and PCBs 118, 138, 153, and 180 and adjusted for total lipids. Cord blood and age-14 serum were available for a subgroup (n = 40) and were also analyzed for p,p´-DDE and PCBs. Sperm fluorescence in situ hybridization (FISH) for chromosomes X, Y, and 18 was used to determine rates of XX18, XY18, YY18, and total disomy. Multivariable adjusted Poisson models were used to estimate the relationship between organochlorine exposure and sperm disomy outcomes.

RESULTS

Adult p,p´-DDE and total PCB serum concentrations were both associated with significantly increased rates of XX18, XY18, and total disomy. Age-14 p,p´-DDE and PCB concentrations were both associated with significantly increased rates of XX, XY, and total disomy in adulthood. Associations between cord blood concentrations of p,p´-DDE and PCBs and sperm disomy in adulthood were not consistently significant.

CONCLUSIONS

Organochlorine exposures measured at age 14 and in adulthood were associated with sperm disomy in this sample of high-exposure men, suggesting that the impacts of persistent pollutants on testicular maturation and function require further investigation.

CITATION

Perry MJ, Young HA, Grandjean P, Halling J, Petersen MS, Martenies SE, Karimi P, Weihe P. 2016. Sperm aneuploidy in Faroese men with lifetime exposure to dichlorodiphenyldichloroethylene (p,p´-DDE) and polychlorinated biphenyl (PCB) pollutants. Environ Health Perspect 124:951-956; http://dx.doi.org/10.1289/ehp.1509779.

Persistently altered epigenetic marks in the mouse uterus after neonatal estrogen exposure

Neonatal exposure to diethylstilbestrol (DES) causes permanent alterations in female reproductive tract gene expression, infertility, and uterine cancer in mice. To determine whether epigenetic mechanisms could explain these phenotypes, we first tested whether DES altered uterine expression of chromatin-modifying proteins. DES treatment significantly reduced expression of methylcytosine dioxygenase TET oncogene family, member 1 (TET1) on postnatal day 5; this decrease was correlated with a subtle decrease in DNA 5-hydroxymethylcytosine in adults. There were also significant reductions in histone methyltransferase enhancer of zeste homolog 2 (EZH2), histone lysine acetyltransferase 2A (KAT2A), and histone deacetylases HDAC1, HDAC2, and HDAC3. Uterine chromatin immunoprecipitation was used to analyze the locus-specific association of modified histones with 2 genes, lactoferrin (Ltf) and sine oculis homeobox 1 (Six1), which are permanently upregulated in adults after neonatal DES treatment. Three histone modifications associated with active transcription, histone H3 lysine 9 acetylation (H3K9ac), H3 lysine 4 trimethylation (H3K4me3), and H4 lysine 5 acetylation (H4K5ac) were enriched at specific Ltf promoter regions after DES treatment, but this enrichment was not maintained in adults. H3K9ac, H4K5ac, and H3K4me3 were enriched at Six1 exon 1 immediately after neonatal DES treatment. As adults, DES-treated mice had greater differences in H4K5ac and H3K4me3 occupancy at Six1 exon 1 and new differences in these histone marks at an upstream region. These findings indicate that neonatal DES exposure temporarily alters expression of multiple chromatin-modifying proteins and persistently alters epigenetic marks in the adult uterus at the Six1 locus, suggesting a mechanism for developmental exposures leading to altered reproductive function and increased cancer risk.

Estrogen action and prostate cancer

Early work on the hormonal basis of prostate cancer focused on the role of androgens, but more recently estrogens have been implicated as potential agents in the development and progression of prostate cancer. In this article, we review the epidemiological, laboratory and clinical evidence that estrogen may play a causative role in human prostate cancer, as well as rodent and grafted in vivo models. We then review recent literature highlighting potential mechanisms by which estrogen may contribute to prostate cancer, including estrogenic imprinting and epigenetic modifications, direct genotoxicity, hyperprolactinemia, inflammation and immunologic changes, and receptor-mediated actions. We discuss the work performed so far separating the actions of the different known estrogen receptors (ERs), ERα and ERβ, as well as G-protein-coupled receptor 30 and their specific roles in prostate disease. Finally, we predict that future work in this field will involve more investigations into epigenetic changes, experiments using new models of hormonal dysregulation in developing human prostate tissue, and continued delineation of the roles of the different ER subtypes, as well as their downstream signaling pathways that may serve as therapeutic targets.

Exposure to endocrine disrupting compounds via the food chain: Is packaging a relevant source?

Contamination of foodstuffs by environmental pollutants (e.g. dioxins, metals) receives much attention. Until recently, food packaging as a source of xenobiotics, especially those with endocrine disrupting properties, has received little awareness despite its ubiquitous use. This article reviews the regulations and use of endocrine disrupting compounds (EDCs) in food packaging and discusses their presence within the context of new toxicology paradigms. I focused on substances known to be legally used in food packaging that have been shown to exhibit endocrine disruptive effects in biological systems. I compiled a list of 50 known or potential EDCs used in food contact materials and examined data of EDCs leaching from packaging into food, with a focus on nonylphenol. I included recent advances in toxicology: mixture effects, the developmental origins of adult disease hypothesis, low-dose effects, and epigenetics. I especially considered the case of bisphenol A. The core hypothesis of this review is that chemicals leaching from packaging into food contribute to human EDCs exposure and might lead to chronic disease in light of the current knowledge. Food contact materials are a major source of food contaminants. Many migrating compounds, possibly with endocrine disruptive properties, remain unidentified. There is a need for information on identity/quantity of chemicals leaching into food, human exposure, and long-term impact on health. Especially EDCs in food packaging are of concern. Even at low concentrations, chronic exposure to EDCs is toxicologically relevant. Concerns increase when humans are exposed to mixtures of similar acting EDCs and/or during sensitive windows of development. In particular, non-intentionally added substances (NIAS) migrating from food contact materials need toxicological characterization; the overall migrate of the finished packaging could be evaluated for biological effects using bioassays. The widespread legal use of EDCs in food packaging requires dedicated assessment and should be updated according to contemporary scientific knowledge.

Neonatal administration of diethylstilbestrol has adverse effects on somatic cells rather than germ cells

Neonatal administration of diethylstilbestrol (DES) to rodents has adverse effects on spermatogenesis. However, not many studies have been conducted to determine which type of cell - germ or somatic - is the major target of DES. In order to clarify this, we tried reciprocal germ cell transplantation--transplantation of germ cells from DES-treated mice into intact mice and germ cells from normal mice into DES-treated mice. The donor germ cells were tagged with the green fluorescent protein (GFP) gene in order to distinguish the exogenous germ cells from the endogenous cells. Moreover, to obtain a large number of spermatogonia from the testes of adult mice, we performed fractionation by centrifugation with Percoll. Consequently, we found that the germ cells collected from DES-treated mice have differentiated into normal sperms in normal seminiferous tubules. However, in the case of the transplantation of normal germ cells into the seminiferous tubules of DES-treated mice, defective spermatogenesis was observed. In conclusion, DES has adverse effects on the somatic cells that are involved in spermatogenesis rather than the germ cells.

Palpation of the Testes in Draftees: Acceptance on the Occasion of Muster and Implication for Health Promotion

OBJECTIVES

Testicular cancer is the most prevalent malignant neoplasm in young men. The key problem in screening for malignant testicular tumors and their main risk factors (undescended testes and testes which descended only after medical treatment) is to reach the target group of "young men".

MATERIALS AND METHODS

In five different military medical centers of German Armed Forces, 1600 young draftees were investigated by a standardized interview at recruitment examination between 2001 and 2003.

RESULTS

Ninety-five percent of respondents reported that they had been palpated at testes during physical examination. The percentage of draftees not palpated at their testes varied between muster centers, but did not depend on the physician's gender. Only two draftees had refused explicitly the palpation of testes. The prevalence of observed pathologic alterations of the testes was 1.69%, including two cases of cryptorchidism, 19 of varicocele, and 6 cases with other benign alterations.

CONCLUSIONS

The simple and effective examination of testes should not be restricted to draftees, but promoted by compulsory health insurance funds, offered and performed routinely by all physicians who have access to the target group of "young men".

Disrupted sex differentiation and feminization of man and domestic animals

Genital malformations constitute the most common birth defects in man and domestic animals and occur frequently in males since the participation of many genes is required for sex differentiation to proceed in the male direction. The precise dose, timing, and coordination needed for their expression add to the proneness of various stages in male sex differentiation to external influences. The emerging insight, through the identification of genes involved in the sex differentiation cascade, is that over 85% of sex anomalies in human and domestic animal populations are not attributable to chromosome aberrations or to mutations in a known gene. Since a majority of severely malformed individuals are incapable of reproduction, the high rates of these defects have to be results either of new mutations or of collaboration of environmental factors with genes. Increase in specific malformations in domestic animals often indicates increased concentration of liability genes brought together in the conceptus by inbreeding. However, in human populations where inbreeding is not the norm such increases may reflect environment-induced new mutations or interaction of environmental agents with hormone-sensitive genes. This review summarizes the information currently available on the genetics of major events in male sex differentiation and briefly discusses the collaborative role that environment may play in disrupting different components of this process.

Progression of the Dose-Related Effects of Estrogenic Endocrine Disruptors, an Important Factor in Declining Fertility, Differs between the Hypothalamo-Pituitary Axis and Reproductive Organs of Male Mice

For the purpose of investigation of working mechanisms in endocrine disruptors, we evaluated the dose-related effects of fetal and/or neonatal exposure to an estrogenic compound on the male reproductive organs in adult mice, particularly with respect to gene expression of steroidogenic acute regulatory protein (StAR). The pregnant ICR mice were given subcutaneous injections of 10 micro g/day/animal of diethylstilbestrol (DES) to subject the fetal mice to in utero exposure (IUE). Subsequently, the newborn male mice were subjected to neonatal exposure (NE) by treatment with vehicle or 0.1-10 micro g/day/animal of DES. Fertility rates of each group were as follows: control, 100%; IUE only, 60%; IUE+NE 0.1 micro g, 25%; IUE+NE 1 micro g, 0%; IUE+NE 10 micro g, 0%. In general histology, germ cell layers in the seminiferous tubules were thinned in the group of IUE+NE 10 micro g. Hypoplasia of the Leydig cells, in which the staining intensity of eosin was diminished, was also observed in the groups of IUE+NE 0.1-10 micro g. The androgen receptor (AR) and estrogen receptor alpha (ERalpha) immunoexpression in the Leydig cells of IUE+NE 1-10 micro g was slightly lower than that in the controls. Long-term dysfunction of the hypothalamo-pituitary-testicular axis, including sustained hypoproduction of gonadotropin and testosterone, and altered expressions of steroid hormone receptors and StAR genes were observed. The hypothalamo-pituitary control of gonadotropin secretion may be affected by the smaller doses of estrogenic agents than the reproductive organs. Furthermore, the fertility rate in the male mice exposed to this estrogenic agent was closely correlated with the testosterone levels, and even more so with the rate-limiting factor of steroidogenesis, StAR. This finding suggests that endocrine disruptors have an important pronounced effect on StAR gene expression.

Risk of Testicular Germ Cell Cancer in Relation to Variation in Maternal and Offspring Cytochrome P450 Genes Involved in Catechol Estrogen Metabolism

The incidence of testicular germ cell carcinoma (TGCC) is highest among men ages 20 to 44 years. Exposure to relatively high circulating maternal estrogen levels during pregnancy has long been suspected as being a risk factor for TGCC. Catechol (hydroxylated) estrogens have carcinogenic potential, thought to arise from reactive catechol intermediates with enhanced capability of forming mutation-inducing DNA adducts. Polymorphisms in maternal or offspring genes encoding estrogen-metabolizing enzymes may influence prenatal catechol estrogen levels and could therefore be biomarkers of TGCC risk. We conducted a population-based, case-parent triad study to evaluate TGCC risk in relation to maternal and/or offspring polymorphisms in CYP1A2, CYP1B1, CYP3A4, and CYP3A5. We identified 18- to 44-year-old men diagnosed with invasive TGCC from 1999 to 2004 through a population-based cancer registry in Washington State and recruited cases and their parents (110 case-parent triads, 50 case-parent dyads). Maternal or offspring carriage of CYP1A2 -163A was associated with reduced risk of TGCC [maternal heterozygote relative risk (RR), 0.6; 95% confidence interval (95% CI), 0.2-1.7; offspring heterozygote RR, 0.7; 95% CI, 0.3-1.5)]. Maternal CYP1B1 (48)Gly homozygosity was associated with a 2.7-fold increased risk of TGCC (95% CI, 0.9-7.9), with little evidence that Leu(432)Val or Asn(453)Ser genotypes were related to risk. Men were also at increased risk of TGCC if they carried the CYP3A4 -392G (RR, 7.0; 95% CI, 1.6-31) or CYP3A5 6986G (RR, 2.4; 95% CI, 1.1-5.6) alleles. These results support the hypothesis that maternal and/or offspring catechol estrogen activity may influence sons' risk of TGCC.

Assessing Maternal Genetic Associations

BACKGROUND

In utero exposures, including maternal phenotypes, are potential risk factors for both early-onset and adult-onset diseases. Two alternative study designs use maternal genotypes at polymorphic loci as biomarkers of an offspring's in utero exposure: (1) a traditional case-control study with logistic regression analysis, in which cases, controls, and mothers of both types of subjects are genotyped; and (2) a case-parent triad study with log-linear analysis, in which cases and both parents are genotyped.

METHODS

We used computer simulations to compare the operating characteristics of the log-linear approach to case-parent triad data and the case-control approach for assessing relative risks (RRs) associated with maternal genotypes.

RESULTS

For high-risk allele frequencies (chromosomal prevalence; f) between 0.20 and 0.75, both methods allowed for valid, unbiased estimates of maternal RRs. The case-parent triad approach, however, had 43% greater power, on average, than the case-control approach with an equal number of genotypes, and 13% greater power with an equal number of cases. For example, under dominant inheritance, to detect 2-fold maternal RRs with 200 (or 150) cases when allele prevalence is between 0.15 and 0.40, the case-parent triad and equal-genotype case-control designs had, on average, 87% and 62% power, respectively. As f approached 0 or 1, the power of both methods decreased sharply.

DISCUSSION

The greater efficiency of case-parent triads may be due to the inclusion of paternal genotype information, which allows for independent tests of disease association with maternal or offspring genotypes. These results highlight one potential advantage of case-parent triad data in assessing maternal genetics as risk factors for offspring disease. We discuss these findings and other considerations between the 2 methodological approaches.

Effect of in utero-administered coumestrol, equol, and organic selenium on biomarkers for phase 2 enzyme capacity and redox status

The aim of the present study was to investigate the effect of in utero administration of coumestrol, equol, and selenium-enriched yeast on selected hepatic phase 2 enzymes, plasma hormone levels, and markers for redox status in plasma and red blood cells (RBCs). The test compounds were administered via the diet to pregnant Sprague-Dawley rats throughout gestation. Within 24 h following delivery dams and offspring were sacrificed, and blood, liver, and reproductive organs were sampled. Coumestrol, equol, and selenium-enriched yeast did not significantly affect hepatic glutathione S-transferase (GST), quinone reductase (QR), or RBC glutathione peroxidase (GPx) in the offspring, whereas significant increases in GST, QR, and GPx activities in dams were observed following administration of selenium-enriched yeast. The level of 17beta-estradiol in offspring from coumestrol-exposed dams was significantly increased compared with the control. The present results indicate that selenium-enriched yeast, coumestrol, and equol affect selected hepatic phase 2 enzymes and GPx in RBC in dams, whereas the offspring in general were refractive to the employed treatments. Further studies are warranted to investigate whether the observed in utero effects imposed by the selected plant compounds confer permanent alterations on the health status of the animal resulting in an altered resistance to cancer.

Diethylstilbestrol (DES) update: recommendations for the identification and management of DES-exposed individuals

Diethylstilbestrol (DES) was etiologically linked to clear cell adenocarcinoma of the vagina in 1971. This article reviews on-going research and emerging information relevant to DES-related health risks, thereby enabling women's health care providers to maintain an evidence-based practice for their DES-exposed patients. To accomplish these goals, the Center for Disease Control and Prevention (CDC) has initiated a national education campaign. This article describes the reasons for this new initiative, the target audiences, the DES historical framework (including major studies and findings), and populations that are affected. Clinical steps for the identification and management of the DES-exposed individual and resultant implications for midwifery and women's health practices are reviewed.

Differential expression of estrogen receptors alpha and beta in the reproductive tracts of adult male dogs and cats

Expression of estrogen receptors (ERs) in the reproductive tracts of adult male dogs and cats has not been reported. In the present study, ERalpha and ERbeta were localized by immunohistochemistry using ER-specific antibodies. ERalpha was found in interstitial cells and peritubular myoid cells in the dog testis, but only in interstitial cells of the cat. In rete testis of the dog, epithelial cells were positive for ERalpha staining, but in the cat, rete testis epithelium was only weakly positive. In efferent ductules of the dog, both ciliated and nonciliated cells stained intensely positive. In the cat, ciliated epithelial cells were less stained than nonciliated epithelial cells. Epithelial cells in dog epididymis and vas deferens were negative for ERalpha. In the cat, except for the initial region of caput epididymis, ERalpha staining was positive in the epithelial cells of epididymis and vas deferens. Multiple cell types of dog and cat testes stained positive for ERbeta. In rete testis and efferent ductules, epithelial cells were weakly positive for ERbeta. Most epithelial cells of the epididymis and vas deferens exhibited a strong positive staining in both species. In addition, double staining was used to demonstrate colocalization of both ERalpha and ERbeta in efferent ductules of both species. The specificity of antibodies was demonstrated by Western blot analysis. This study reveals a differential localization of ERalpha and ERbeta in male dog and cat reproductive tracts, demonstrating more intensive expression of ERbeta than ERalpha. However, as in other species, the efferent ductules remained the region of highest concentration of ERalpha.

Changes in serum PBB and PCB levels over time among women of varying ages at exposure

The identification of host factors that are predictors of changes in serum polyhalogenated biphenyl contaminants over time has been a difficult challenge in epidemiologic studies of exposed individuals. Of particular concern are age at exposure, reproductive and lactational histories, and changes in body mass index. Using both cross-sectional and longitudinal approaches, this study examined factors related to high initial serum PBB and PCB levels and changes in these levels over time among women of varying ages at exposure (n=1772; age range<1 to 45 years). In 1973, PBB exposure occurred through consumption of farm products contaminated with PBB added to cattle feed. Exposures to PCBs began in 1941 through PCB-contaminated silo sealant deteriorating into animal feed. The Michigan Department of Public Health began enrolling participants in 1977 and has continued to follow them through annual updates. At enrollment, questionnaires were administered to obtain demographic, lifestyle, and anthropometric measurements, medical/reproductive and occupational histories, and contaminated food consumption patterns. Blood samples were collected for PBB and PCB analysis at enrollment for all participants; additional serum tests were done on a subset of the population during follow-up. Median serum levels at enrollment were 2.0 ppb PBB and 5.0 ppb PCB. A decline in serum PBB level over an interval that ranged from 1 to 146 months (median=31) was observed for 44.6% of the women (median=1.0 ppb), while 12.2% showed an increase (median=1.0 ppb). PCB levels declined in 50.3% of the women (median=3.0 ppb) while 12.2% increased (median=2.0 ppb). Relative to women whose contaminant levels were stable, higher initial serum level was a predictor of decline for both PBB and PCB (OR=1.66, 95% CI 1.52-1.82; OR=3.26, 95% CI 2.58-4.12, respectively); a yearly increase in interval between tests was related to declining PCBs (OR=1.65, 95% CI 1.46-1.87). In addition, age< or =10 years at exposure (OR=1.72, 95% CI 1.03-2.86) and residence on a quarantined farm (OR=1.40, 95- CI 1.03-1.90) were predictors of a decrease in PBBs. Factors related to an increase in PBB levels were age< or =10 years at exposure (OR=0.30, 95% CI 0.10-0.96) and initial PBB level (OR=1.24, 95% CI 1.15-1.33); and for PCBs, high initial level (OR=1.34, 95% CI 1.17-1.53) and body mass index (OR=1.07, 95% CI 1.01-1.13). One or more live births during the interval between tests were not related to changing levels of either contaminant; breastfeeding data were not available for examination. Early age at exposure appears to be an important predictor of changes in serum PBB levels over time.

Tamoxifen induces endometrial and vaginal cancer in rats in the absence of endometrial hyperplasia

Tamoxifen was administered orally to neonatal rats on days 2-5 after birth and the subsequent effects on the uterus were characterized, morphometrically, over the following 12 months. Tamoxifen inhibited development of the uterus and glands in the endometrium, indicating a classical oestrogen antagonist action. Between 24 and 35 months after tamoxifen treatment there was a significant increase in the incidence (26%) of uterine adenocarcinomas and a 9% incidence of squamous cell carcinomas of the vagina/cervix in the absence of any oestrogen agonist effect in the uterus. This demonstrates that an oestrogen agonist effect is not an absolute requirement for the carcinogenic effect of tamoxifen in the reproductive tract of the rat. The unopposed oestrogen agonist effect of tamoxifen on the endometrium may not be the only factor involved in the development of endometrial cancers. It is possible that tamoxifen causes these tumours via a genotoxic mechanism similar to that seen in rat liver. However, using (32)P-post-labelling we failed to find evidence of tamoxifen-induced DNA adducts in the uterus. Tamoxifen may affect hormonal imprinting of oestrogen receptor responses in stem cells of the uterus, causing reproductive tract cancers to arise at a later time, in the same way as has been proposed for diethylstilbestrol. If these rodent data extrapolate to humans, then women who are taking tamoxifen as a chemopreventative may have an increased risk of vaginal/cervical cancer, as well as endometrial cancer.

Germ cell cancer

The publication of the proceedings of Fourth Workshop on Carcinoma in situ was an impressive leap in our understanding of the interaction between prenatal and postpubertal factors in the development of germ cell cancer as well as increased insight into the molecular events that are involved in the development of these tumors. From this work, physicians are increasingly accepting that estrogen-mediated prenatal priming of germ cells generates a predisposition to postpubertal cyclin D2-driven initiation of full mitotic cell cycle replication of a tetraploid p53-expressing meiotically arrested pachytene spermatocyte that is under increased gonadotrophin drive because of testicular atrophy inducing events. From this new knowledge, new markers, eg, FGF4, CD30, and OCT-4, of embryonal carcinoma cells are identifying alternative ways of identifying poor risk tumors and leading to renewed interest in study of histopathology of these tumors. With greater attention to late events and increasing confirmation that chemotherapy is better than radiation even in seminoma and that seminoma is more chemosensitive than nonseminoma, a renewed clinical need exists for improved pathologic definition to reduce unnecessary usage of chemotherapy and maximize its benefits. With the failure of vinblastine, ifosfamide, and cisplatin to show any benefit over BEP (bleomycin, etoposide, and cisplatin) in the Southwest Oncology Group trial, re-examination of approaches to treatment of poor risk disease is emphasized as the priority for future trials.

Detection of oestrogenic chemicals by assaying the expression level of oestrogen regulated genes

The oestrogen receptor belongs to the superfamily of nuclear receptors. Classically, nuclear receptors are thought to reside either in the nucleus or in the cytoplasm where they interact with their ligand which induces a conformational change that exposes the DNA binding domain. This is followed by dimerisation and binding of their corresponding response elements. By interacting with the transcriptional apparatus they then either activate or repress the transcription of target genes. However, this is a highly simplified view, since the activated oestrogen receptor interacts with other signal transduction pathways and its intrinsic transcriptional activity is highly influenced by phosphorylation and by its interaction with other proteins. This is clearly observed when the oestrogenicity of antioestrogens is tested since some compounds activate the receptor in yeast, but not in mammalian cells. However, when specific kinases are activated antioestrogens can also function as oestrogens in mammalian cells. Moreover, components of the MAP kinase and perhaps the cAMP and other pathways are activated before the receptor even enters the nucleus. Thus, when analysing the effects of oestrogenic compounds, it is important to assay both their potency as activators of transcription as the effects caused by interactions with other signal transduction pathways. This may be possible by combining assay methods, such as direct in vitro measurement of interaction between a potential oestrogenic chemical and the receptor or the yeast E-screen, with methods that are based on mammalian cells or whole animals. An alternative is to assay gene expression directly by methods such as differential display, where the expression of both genes known to be regulated directly by the receptor and genes regulated by other pathways can be monitored. Thereby it may be possible to assign different responses to the activation of distinct pathways.