Breast cancer epidemiology : summary and future directions

Epidemiologic reviews, 1993

Abstract

The most common cancer in US women and the 2nd leading cause of cancer death is breast cancer.

Between 1980-1987 in the US. age-adjusted incidence rates of breast cancer rose rapidly. They are also rising rapidly in several Asian countries (e.g., in Japan) which have the lowest incidence rates. These rapid increases may mean that environmental factors are responsible.

Incidence rates rise greatly with age until the late 40s. US women at highest risk of breast cancer are Jewish women, urban women, single women, and women living in the northern US. Women at lowest risk include Mormon and Seventh-Day Adventist women, Hispanic and Asian women, rural women, women living in the southern US, and married women.

Factors that have a relative risk greater than 2 are

  • mother and sister with history of breast cancer, especially if diagnoses at an early age;
  • atypical epithelial cells in nipple aspirate fluid;
  • nodular densities on the mammogram;
  • history of cancer in 1 breast;
  • mother or sister with history of breast cancer;
  • biopsy-confirmed benign proliferative breast disease;
  • hyperplastic epithelial cells without atypia in nipple aspirate fluid;
  • and radiation to chest in moderate to high doses.

Ovarian hormones appear to stimulate cell division in the breast, thus elevated levels may be risk factors.

Exogenous hormones may also increase the risk. Women are exposed to these exogenous hormones through

  • estrogen replacement therapy,
  • progestin only pills,
  • oral contraceptives,
  • long-acting injectable contraceptives,
  • and diethylstilbestrol.

Postmenopausal obesity increases the risk while premenopausal obesity decreases the risk. A high fat diet in childhood and adolescence may increase the risk. Alcohol drinking may also increase the risk.

Older, white, and nulliparous women are more likely to have estrogen receptor-positive cancers.

Breast cancer in males tends to share the same risk factors as well as its own unique factors.

Prevention of postmenopausal obesity is the only established primary prevention effort. Screening is the only secondary prevention means.

Sources

DES DIETHYLSTILBESTROL RESOURCES

Increased Breast Cancer risk in DES-Exposed Progeny

Maternal exposure to diethylstilbestrol during pregnancy and increased breast cancer risk in daughters, 2014

Study Summary

The idea that susceptibility to breast cancer is determined not only through inherited germline mutations but also by epigenetic changes induced by alterations in hormonal environment during fetal development is gaining increasing support. Using findings obtained in human and animal studies, this review addresses the mechanisms that may explain why daughters of mothers who took synthetic estrogen diethylstilbestrol (DES) during pregnancy have two times higher breast cancer risk than women who were not exposed to it. The mechanisms likely involve epigenetic alterations, such as increased DNA methylation and modifications in histones and microRNA expression.Further, these alterations may target genes that regulate stem cells and prevent differentiation of their daughter cells. Recent findings in a preclinical model suggest that not only are women exposed to DES in utero at an increased risk of developing breast cancer, but this risk may extend to their daughters and granddaughters as well. It is critical, therefore, to determine if the increased risk is driven by epigenetic alterations in genes that increase susceptibility to breast cancer and if these alterations are reversible.

Abstracts

In this review, findings related to in utero DES exposure and breast cancer are discussed for the purpose of weighing evidence as to whether fetal hormonal environment can impact breast cancer risk in women several decades later. Since causal studies can readily be performed using animal models, findings obtained in DES-exposed mouse and rat offspring also are discussed. Importantly, animal studies were done prior to any epidemiological studies addressing a possible link between maternal DES exposure and breast cancer risk among daughters could be performed. By the 1980s, exposed daughters in the cohorts began to be old enough to develop breast cancer and several human studies have been performed since to determine if maternal exposure to DES during pregnancy increases an offspring’s breast cancer risk.

…”The animal studies show that the doses of DES relevant to pregnant women increased later risk of developing mammary tumors. Specifically, female offspring of rat dams exposed to a total of 1.2 μg DES either on gestation week 2 or 3, to 0.6 μg or 4 μg DES on both gestation days 15 and 18 (all via injection), or via diet to 0.1, 1 or 10 ppm DES between gestation days 13 and 21 (week 3) exhibited increased mammary cancer risk. An increase in risk also was seen in rats exposed to a single dose of 0.1, 1 or 10 μg or less of DES at birth.” …

…”Importantly, in utero exposure to DES leads to an increase in terminal end buds (TEBs) numbers. It is thus possible that one of the mechanisms causing an increase in mammary cancer risk in DES offspring is an increase in the number of targets for malignant transformation.”…

…”Several published studies have investigated breast cancer risk in the daughters of DES mothers, the majority of which were cohort studies done in the US. As the women in the cohorts aged, their breast cancer risk grew higher, compared with matched non-exposed controls. The findings clearly indicate that after age 40 years the incidence of breast cancer is at least two-fold higher in the daughters of DES-exposed mothers. Many pregnant women in Europe and Australia also used DES, but the peak exposure occurred 10 to 20 years later than in the US, and this probably explains why a recent study done in Europe found a trend but not a significant increase in breast cancer risk among them. Once the European daughters reach the age when breast cancer is more commonly detected, they too are likely to exhibit a significant increase in breast cancer risk.”…

To summarize, animal and human studies have generated similar findings and indicate that there is a causal link between maternal exposure to DES during pregnancy and increased breast cancer risk among female offspring. According to animal studies, the increase in risk may reflect the presence of a higher number of TEBs in the mammary epithelium in the DES offspring. Baik and colleagues have proposed that the increase in mammary epithelial cells in in utero estrogen-exposed females is caused by a high number of mammary stem cells or an increase in their potential to generate daughter cells. Our unpublished data support this conclusion”

Epigenetic alterations induced by in utero diethylstilbestrol exposure

We and others have observed that the expression of DNA methyltransferases (DNMTs) is persistently altered in estrogen-regulated tissues following estrogenic exposures during early life. In utero exposure to DES is reported to increase the expression of DNMT1 in the epididymis and uterus. We found that DNMT1 expression is increased in the mammary glands of adult rat offspring of dams exposed to ethinyl estradiol during pregnancy. These changes provide a key regulatory layer to influence gene expression in the mammary gland and perhaps breast tumors of individuals exposed to DES or other estrogenic compounds in utero.

The effects of maternal diethylstilbestrol exposure are not limited to the F1 generation?

Some researchers have begun to investigate whether the effects of maternal DES exposure during pregnancy extend to the third generation in humans. Although there is no evidence that DES granddaughters have cervical and ovarian abnormalities similar to DES daughters, there is evidence that they may have more menstrual irregularities and a higher rate of infertility than non-exposed granddaughters. In addition, DES granddaughters may have a slightly higher risk of ovarian cancer. The granddaughters are still too young to assess whether they might also be at an increased risk of developing breast cancer.

Millions of women in the US, Europe and Australia have been exposed to DES in the womb, and consequently exhibit about a two times higher breast cancer risk than unexposed women. The increase in risk may not be limited to the DES-exposed daughters, but could also increase breast cancer risk in granddaughters and great granddaughters. Such outcome would be consistent with the findings we obtained in studies using a synthetic estrogen ethinyl estradiol (EE2). If DES has similar effects to ethinyl estradiol on the transgenerational increase in breast cancer risk, it is urgent to find ways to stop the cycle of inheritance, and also prevent breast cancer in DES-exposed granddaughters and great granddaughters.

To achieve this goal, we need to understand how maternal DES exposure during pregnancy increases a daughter’s breast cancer risk. A plausible model is proposed in the featured image. It is evident from studies done in animal models that in utero DES exposure induces epigenetic changes in reproductive tract tissues and the breast. DES exposure might also have induced epigenetic changes in primordial germ cells and consequently germ cells, and further be detectable in the somatic cells in granddaughters and great granddaughters. We are not aware of any study that has compared epigenetic changes in germ cells and the next generation somatic cells in individuals exposed to DES or other endocrine disruptors in utero. Second, we should investigate whether the transgenerational increase in breast cancer risk can be prevented with drugs that reverse epigenetic modifications. Our preliminary studies in mice suggest that this is achievable in daughters by using the well-tolerated and non-toxic histone deacetylase inhibitor valproic acid and DNMT inhibitor hydralazine. However, whether these compounds also prevent an increase in granddaughters and great granddaughters in experimental models remains to be investigated.

Sources

  • Full study (free access) : Maternal exposure to diethylstilbestrol during pregnancy and increased breast cancer risk in daughters, Breast cancer research : BCR, NCBI PubMed PMC4053091, 2014.
  • Featured image : Proposed model to explain an increase in breast cancer risk in daughters, and possibly granddaughters and great granddaughters, of mothers who took diethylstilbestrol during pregnancy. DES, diethylstilbestrol; TDLU, terminal ductal lobular unit; TEB, terminal end bud. PMC4053091/figure/F1.
DES DIETHYLSTILBESTROL RESOURCES

DES Implications for the Third Generation

image of Grandson

The Health Effects of Diethylstilbestrol Revisited

Abstract

“… DES has been associated with increased risk of reproductive tract tumors in third-generation mice, that is, mice whose grandmothers were exposed to DES. These tumors have included uterine adenocarcinomas and sarcomas and benign ovarian tumors in females as well as tumors in the rete testis in males.

By identifying persons with known exposure, as well as their children, potential participants for studies of the long-term effects of DES could also be identified. With appropriate samples and further research, greater knowledge of the health effects of DES on the children and grandchildren of women who took DES could be gained. Persons who may have been exposed to DES may find national websites and organizations (helpful to access current research and health information as it becomes available.”

Sources

  • The health effects of diethylstilbestrol revisited, Journal of obstetric, gynecologic, and neonatal nursing : JOGNN, NCBI PubMed, PMID: 16020417, 2005 Jul-Aug.
DES DIETHYLSTILBESTROL RESOURCES

Increased Risk of Cancer in DES Grandsons and Granddaughters

Offspring of women exposed in utero to diethylstilbestrol (DES): a preliminary report of benign and malignant pathology in the third generation, 2008

Abstract

BACKGROUND
Animal studies suggest that prenatal exposure to the synthetic estrogen diethylstilbestrol (DES) causes epigenetic changes that may be transmitted to the next generation. Specifically, these studies show an elevated incidence of reproductive tumors in the female offspring of prenatally-exposed mice.

METHODS
We assessed cancer and benign pathology diagnoses occurring in the offspring of women whose prenatal exposure to DES (or lack of exposure) was verified by medical record. Our data arose from 2 sources: the mothers’ reports of cancers occurring in 8216 sons and daughters, and pathology-confirmed cancers and benign diagnoses self-reported by a subset of 793 daughters.

RESULTS
Although statistical power is limited, our data are consistent with no overall increase of cancer in the sons or daughters of women exposed in utero to DES. Based on pathology-confirmed diagnoses reported by the daughters, we saw no association between DES and risk of benign breast disease or reproductive tract conditions. Based on 3 cases, the incidence of ovarian cancer was higher than expected in the daughters of women exposed prenatally to DES.

CONCLUSIONS
Our data do not support an overall increase of cancer risk in the sons or daughters of women exposed prenatally to DES, but the number of ovarian cancer cases was greater than expected. While preliminary, this finding supports continued monitoring of these daughters.

Third-Generation Cohort

In 2001, the NCI assembled the third-generation cohort, consisting of the adult daughters (≥18 years of age) of DES-exposed and unexposed second-generation women.37 A review of parity records at all 5 study centers identified 763 exposed and 577 unexposed mothers of 966 exposed and 815 unexposed age-eligible daughters. About half of the mothers, 414 (54%) of the exposed and 297 (52%) of the unexposed, gave permission to contact 515 (53%) exposed and 383 (47%) unexposed daughters. The questionnaires, which queried daughters for hormonal and reproductive information, screening histories, and medical events (including gynecologic biopsies, breast biopsies, and cancer diagnoses), were returned by 793 (88%) of 898 daughters, including 463 (90%) exposed and 330 (86%) unexposed. Pathology reports were obtained to verify self-reported diagnoses and biopsies. A study-related review of histology slides confirmed 1 of 2 reported cases of borderline ovarian cancer. Slides were unavailable for the second case, which involved metastatic disease.

The confirmation of cancers occurring in the subset of adult daughters participating in the third-generation study was excellent. Of the 8 self-reported cancers, 7 (5 exposed, 2 unexposed) were confirmed by pathology; consent was not obtained to confirm a melanoma reported by an unexposed woman. For other conditions, confirmation of benign biopsies was reasonably good, generally exceeding 60%.

DES Follow-up Study Summary

Studies have shown a slightly increased risk of breast cancer in women who were given Diethylstilbestrol (DES) while they were pregnant. Their daughters, who were exposed to DES prenatally (before they were born), have an elevated risk of reproductive tract conditions, including a rare vaginal cancer. A question now being studied is whether DES health effects can be passed from the prenatally exposed women to their offspring (intergenerational transmission).

Studies in mice suggest that intergenerational transmission of DES health effects may be possible. Recent evidence indicates that prenatal exposure to DES may cause changes in the behavior of genes that influence hormones and the development of the female reproductive tract. These changes in gene behavior may be passed on to the next generation. Evidence for intergenerational transmission comes from mouse studies showing a higher number of reproductive tract tumors in the daughters of prenatally exposed female mice. We used the DES Follow-up Study data to assess whether cancer was more common in the offspring of women who were prenatally exposed to DES. Cancers affecting these offspring (the third generation) were identified using two approaches. First, we asked women participating in the DES Follow-up Study to report cancers diagnosed in their 8,216 third generation sons and daughters. Second, we asked 793 third generation daughters participating in the Third Generation Study to tell us about their cancers. We also asked the third generation daughters to tell us about their reproductive tract and breast biopsies. Next we confirmed the reported biopsies and cancers by checking the medical records of these third generation daughters.

Our results did not show an overall increase of cancer in the sons or in the daughters of prenatally DES-exposed women. However, based on only three cases, the number of ovarian cancers was higher than expected in the daughters of women exposed prenatally to DES. Because of the small number of cases, this result must be considered preliminary. The association may be a chance finding or may be due to the way in which the data were reported or collected. We did not find an association between DES and benign breast disease or reproductive tract conditions, but most of the women are too young for a meaningful assessment of these outcomes. Further follow-up is needed to assess whether prenatal DES exposure can affect the third generation in humans.

Sources

  • Full study (free access) : Offspring of Women Exposed In Utero to Diethylstilbestrol (DES): A Preliminary Report of Benign and Malignant Pathology in the Third Generation, Epidemiology doi: 10.1097/EDE.0b013e318163152a, March 2008.
  • Featured image credit oaks.journals.
  • NCIDES Follow-up Study Published Papers.
DES DIETHYLSTILBESTROL RESOURCES

Birth Defects in the Sons and Daughters of Women who were Exposed in utero to Diethylstilbestrol (DES)

Possible association between the DES mothers exposure and birth defects in DES grandsons, DES granddaughters

2010 Study Abstract

Background
Prenatal exposure to diethylstilbestrol (DES) is associated with adverse health outcomes, including anatomic anomalies of the reproductive tract in women and of the genitourinary tract in men. The mouse model, which replicates many DES-related effects seen in humans, suggests that prenatal DES exposure causes alterations that may affect the next generation of offspring.

Methods
Women participating in a large multi-center study of prenatal DES exposure were asked to report birth defects occurring among 4,029 sons and 3,808 daughters (i.e., the third generation). A subcohort of 793 third generation daughters were also queried for birth defects. We used logistic regression models to generate odds ratios and 95% confidence intervals for the association between prenatal DES exposure in the mother and birth defects in the offspring.

Results
Based on the mothers’ reports, overall birth defects were elevated in the sons (OR = 1.53; 95% CI = 1.04, 2.23) and in the daughters (OR = 2.35; 95% CI = 1.44, 3.82). Most estimates of association were imprecise, but daughters appeared to have an excess of heart conditions (OR = 4.56; 95% CI = 1.27, 16.34.

Conclusions
Our data suggest a possible association between the mother’s prenatal DES exposure and birth defects in their offspring, particularly in daughters. We cannot, however, rule-out the possible influence of reporting bias. In particular, the exposed daughters’ elevated risk of cardiac defects may be due to the underreporting of these conditions by unexposed mothers.

Sources

  • Birth Defects in the Sons and Daughters of Women who were Exposed in utero to Diethylstilbestrol (DES), International journal of andrology, NCBI PubMed PMC2874639, 2010 April.
  • Featured image credit Nathan Dumlao.
DES DIETHYLSTILBESTROL RESOURCES

Examination of multigenerational transmission of environmental associations

Toward an Emerging Paradigm for Understanding Attention-Deficit/Hyperactivity Disorder and Other Neurodevelopmental, Mental, and Behavioral Disorders

2018 Study Abstract

In Association of Exposure to Diethylstilbestrol During Pregnancy With Multigenerational Neurodevelopmental Deficits, Kioumourtzoglou et al use an approach that is as important as it is underused: an examination of multigenerational transmission of environmental associations. That approach may be the most important from an epidemiological perspective. They report that pollutant exposure to grandparents conveys a 30% increase in risk of ADHD in grandchildren. The findings are novel and contribute to this emerging shift in the understanding of mental and behavioral disorders such as ADHD. The size of the association, similar to many other concurrent risk factors for ADHD, is striking.

Although, as the authors note, the dosages of everyday individual environmental pollutants are generally lower (in developed countries at least) than the dosages of diethylstilbestrol they studied, today’s population is exposed to hundreds of poorly studied, neurodevelopmentally or hormonally active compounds, the interactions among which are unknown. Thus, the actual associations today are difficult to quantify.

The limitations in this study should not be overlooked—genetic associations were not able to be examined (so a genotype-environment correlation might partially account for findings), causality could not be evaluated because of the absence of F1 siblings, and ADHD assessment is limited in population studies. Their finding of a first trimester bias in the association, in particular, should be interpreted very cautiously; the incidence of ADHD in the second, third, and first trimester exposures were all higher than the unexposed group, and the statistical power to detect between-trimester associations was low. As the authors appropriately noted, further work on trimester-specific associations will be of interest. Finally, an epigenetic transmission is not the only possibility (because of third-generation oocyte exposure, as the authors noted), although epigenetic transmission by neuroactive chemicals to the third generation is demonstrated in nonhuman animals.

Sources

  • Toward an Emerging Paradigm for Understanding Attention-Deficit/Hyperactivity Disorder and Other Neurodevelopmental, Mental, and Behavioral Disorders, JAMA Pediatrics doi:10.1001/jamapediatrics.2018.0920, July 2018.
  • Featured image credit Jason Leung.
DES DIETHYLSTILBESTROL RESOURCES

Increased breast cancer risk in DES daughters, granddaughters and great granddaughters

The effects of maternal diethylstilbestrol exposure are not limited to the F1 generation

2014 Study Abstract

The idea that susceptibility to breast cancer is determined not only through inherited germline mutations but also by epigenetic changes induced by alterations in hormonal environment during fetal development is gaining increasing support. Using findings obtained in human and animal studies, this review addresses the mechanisms that may explain why daughters of mothers who took synthetic estrogen diethylstilbestrol (DES) during pregnancy have two times higher breast cancer risk than women who were not exposed to it. The mechanisms likely involve epigenetic alterations, such as increased DNA methylation and modifications in histones and microRNA expression. Further, these alterations may target genes that regulate stem cells and prevent differentiation of their daughter cells. Recent findings in a preclinical model suggest that not only are women exposed to DES in utero at an increased risk of developing breast cancer, but this risk may extend to their daughters and granddaughters as well. It is critical, therefore, to determine if the increased risk is driven by epigenetic alterations in genes that increase susceptibility to breast cancer and if these alterations are reversible.

Gene expression can be altered as a consequence of mutations or epigenetic changes. In contrast to gene mutations within the DNA, epigenetic changes involve post-transcriptional modifications; that is, methylation of gene promoter regions, histone modifications, deposition of certain histone variants along specific gene sequences and microRNA (miRNA) expression. Although both changes are heritable, an important distinction between the two is that mutations are not reversible, but epigenetic modifications generally are.

Developing germ cells undergo epigenetic erasure when they, as primordial germ cells, enter into the fetal gonads around embryonic day 10 to 11 (in mice and rats), and then undergo gender-specific reprogramming as germ cells. It is now clear that reprogramming of these cells is susceptible to modifications caused by changes in fetal hormonal environment, such as resulting from an exposure to DES or other endocrine disruptors. Consequently, these exposures can leave a permanent biochemical footprint on the genome of the F1 generation germ cells, and this change may be inherited by the F2 generation germ line and several subsequent generations.

Some researchers have begun to investigate whether the effects of maternal DES exposure during pregnancy extend to the third generation in humans. Although there is no evidence that DES granddaughters have cervical and ovarian abnormalities similar to DES daughters, there is evidence that they may have more menstrual irregularities and a higher rate of infertility than non-exposed granddaughters. In addition, DES granddaughters may have a slightly higher risk of ovarian cancer. The granddaughters are still too young to assess whether they might also be at an increased risk of developing breast cancer.

Millions of women in the US, Europe and Australia have been exposed to DES in the womb, and consequently exhibit about a two times higher breast cancer risk than unexposed women. The increase in risk may not be limited to the DES-exposed daughters, but could also increase breast cancer risk in granddaughters and great granddaughters. Such outcome would be consistent with the findings we obtained in studies using a synthetic estrogen ethinyl estradiol (EE2). If DES has similar effects to ethinyl estradiol on the transgenerational increase in breast cancer risk, it is urgent to find ways to stop the cycle of inheritance, and also prevent breast cancer in DES-exposed granddaughters and great granddaughters.

To achieve this goal, we need to understand how maternal DES exposure during pregnancy increases a daughter’s breast cancer risk. A plausible model is proposed in feature image. It is evident from studies done in animal models that in utero DES exposure induces epigenetic changes in reproductive tract tissues and the breast. DES exposure might also have induced epigenetic changes in primordial germ cells and consequently germ cells, and further be detectable in the somatic cells in granddaughters and great granddaughters. We are not aware of any study that has compared epigenetic changes in germ cells and the next generation somatic cells in individuals exposed to DES or other endocrine disruptors in utero. Second, we should investigate whether the transgenerational increase in breast cancer risk can be prevented with drugs that reverse epigenetic modifications. Our preliminary studies in mice suggest that this is achievable in daughters by using the well-tolerated and non-toxic histone deacetylase inhibitor valproic acid and DNMT inhibitor hydralazine. However, whether these compounds also prevent an increase in granddaughters and great granddaughters in experimental models remains to be investigated.

In summary, women exposed to DES in utero are destined to be at an increased risk of developing breast cancer, and this risk may extend to their daughters and granddaughters as well. It is of critical importance to determine if the increased risk is driven by epigenetic alterations in genes that increase susceptibility to breast cancer and if these alterations are reversible.

Sources

  • Maternal exposure to diethylstilbestrol during pregnancy and increased breast cancer risk in daughters, Breast Cancer Research, NCBI PubMed PMC4053091, 2014 Apr 30.
  • Proposed model to explain an increase in breast cancer risk in daughters, and possibly granddaughters and great granddaughters, of mothers who took diethylstilbestrol during pregnancy : featured image credit PMC4053091/figure/F1.
DES DIETHYLSTILBESTROL RESOURCES

Effects of DES in a Third Generation

Exposure to Diethylstilbestrol during Sensitive Life Stages: A legacy of heritable health effects

2013 Selected Abstracts

Walker and Haven predicted that “if the high intensity of DES multigenerational carcinogenicity seen in mice is applicable to the human population, this is a health problem of major proportions.” They go on to say that it “could take over 50 years” to detect the effects in future generations, due to the length of time required for diseases such as cancer to manifest. It is predicted that cross-generational responses to DES exposure are possible due to epigenetic changes in the DNA and that the “germ cell pool could have become massively contaminated”. For example, early exposure to EDCs, like DES, is thought to reprogram mouse female reproductive tract development and affect how the reproductive tract responds to endogenous estrogens later in life. They suggest that “environmental estrogens may be more potent than previously suspected, due to synergistic action from concurrent exposures.”

The studies on the cohort of men (grandsons) and women (granddaughters) whose mothers were exposed prenatally to DES (grandchildren had no direct exposure) are limited as they are just beginning to reach the age when relevant health problems can be studied. Studies that have been performed contain preliminary data, as the power is low. Therefore, the main sources of information for third generation effects are rodent studies. In general, multi-generational mouse studies have shown an increased susceptibility to tumor formation in the third generation which suggests that DES grandchildren are also at an increased risk for cancer.

Granddaughters

Currently there are no human studies that definitively show any adverse effects of DES for the third generation of females. A small cohort study of 28 DES granddaughters found no abnormalities in the lower genital tract and no cases of CCA. These results led authors to conclude that third generation effects were unlikely even after they acknowledged that the number of participants was too small and the women were too young for the findings to have any real significance.

Multigenerational rodent studies, as a primary source for information on the effects of DES exposure, disagree with those preliminary findings in humans. Although severe effects of DES were apparent in the first round of CD-1 mouse offspring (second generation), the third generation did not exhibit the same subfertility, regardless of exposure timing or dose. However, these studies have found an increased susceptibility to tumor formation in the third generation. Aged third generation female mice had increased risks for uterine cancers, benign ovarian tumors, and lymphomas. One study found cervical adenocarcinomas, which are not generally seen in untreated mice, in third generation females similar to those induced by direct prenatal DES exposure. In the same study, third generation female mice had increases in ovarian, uterine, and mammary tumors with the total number of reproductive tumors being statistically significant from the control mice.

Grandsons

The early reports of DES grandsons show an increase in hypospadias in this population. Hypospadias occurred twenty times more frequently in the DES grandsons’ cohort, which suggests that their mothers (DES daughters) may have had a disturbed hormonal balance during their reproductive life that interfered with the genital development of the male fetus. The prevalence of hypospadias was found to be >3% in DES grandsons but the risk of the defect is still low. Mouse studies in the third generation DES-exposed male population have found an increased susceptibility for reproductive tumor formation, specifically in the testes, prostate, and seminal vesicles. No effect on reproductive capacity or other deformities was seen in DES grandsons.

Sources

  • Full study (free access) : Exposure to Diethylstilbestrol during Sensitive Life Stages: A legacy of heritable health effects, Birth defects research. Part C, Embryo today : reviews, NCBI PubMed PMC3817964, 2013 Nov 5.
  • Featured image credit Oskars Sylwan.
DES DIETHYLSTILBESTROL RESOURCES

Epigenetics and transgenerational effects of DES

EDC-2: The Endocrine Society’s Second Scientific Statement on Endocrine-Disrupting Chemicals

Selected Abstracts

Prenatal exposure to DES caused hypermethylation of the Hoxa10 gene in the uterus of mice and was linked to uterine hyperplasia and neoplasia later in life. Beyond the effects of prenatal exposure to DES on the daughters exposed in utero are suggestions that this leads to transgenerational effects of the chemical on the reproductive system, although whether this is linked to DNA methylation changes in humans is unknown.

DES caused histone deacetylation in the promoter region of the cytochrome P450 side chain cleavage (P450scc) gene.

Neonatal DES exposure also caused the differential expression of 900 genes in one or both layers of the uterus. Specifically, DES altered multiple factors in the PPARγ pathway that regulate adipogenesis and lipid metabolism, and it perturbed glucose homeostasis, suggesting that DES affects energy metabolism in the uterus. In the mouse uterus, DES altered the expression of chromatin-modifying proteins and Wnt signaling pathway members, caused epigenetic changes in the sine oculis homeobox 1 gene, and decreased the expression of angiogenic factors. DES also altered the expression of genes commonly involved in metabolism or endometrial cancer in mice, and it activated nongenomic signaling in uterine myometrial cells and increased the incidence of cystic glands in rats.

Studies in mice showed that DES induced vaginal adenosis by down-regulating RUNX1, which inhibits the BMP4/activin A-regulated vaginal cell fate decision; induced epithelial cell proliferation and inhibited stromal cell proliferation; and caused persistent down-regulation of basic-helix-loop-helix transcription factor expression (Hes1, Hey1, Heyl) in the vagina, leading to estrogen-independent epithelial cell proliferation. Neonatal exposure to DES caused persistent changes in expression of IGF-1 and its downstream signaling factors in mouse vaginas. It also up-regulated Wnt4, a factor correlated with the stratification of epithelial cells, in mouse vaginas. Interestingly, the simultaneous administration of vitamin D attenuated the ability of DES to cause hyperplasia of the vagina in neonatal mice.

In mice treated prenatally with DES there was a significant increase in enhancer of Zeste homolog 2 (EZH2) protein and EZH2 activity (measured by increased mammary histone H3 trimethylation)—a histone methyltransferase that may be linked to breast cancer risk and epigenetic regulation of tumorigenesis, as well as an increase in adult mammary gland EZH2.

EDC exposures to pregnant animals have been shown to cause multigenerational or transgenerational effects on a number of disease endpoints, particularly reproduction, neurobehavior, and adiposity. This work needs much more follow-up to better determine the underlying mechanisms, which are likely to include epigenetic molecular programming changes. Moreover, research is needed in human populations. Some work has been conducted in grandchildren of DES-exposed women who took this estrogenic pharmaceutical during pregnancy. The consequences on the offspring (F1 generation) are well-studied, and research is beginning to be published on the grandchildren (F2 generation). For environmental chemicals, several ongoing projects need continued funding.

Sources

  • Full study (free access) : EDC-2: The Endocrine Society’s Second Scientific Statement on Endocrine-Disrupting Chemicals, NCBI PubMed PMC4702494, 2015 Nov 6.
  • Featured image credit Craig Whitehead.
DES DIETHYLSTILBESTROL RESOURCES

Association of Exposure to Diethylstilbestrol During Pregnancy With Multigenerational Neurodevelopmental Deficits

DES adverse impact on fetal germ cells, impairing neurodevelopment of offspring

Abstracts

We conducted a large-scale cohort analysis to assess the association between use of diethylstilbestrol during pregnancy and third-generation ADHD. The observed associations were robust to covariate adjustment and sensitivity analyses. Despite animal evidence of adverse multigenerational consequences—including neurodevelopmental disorders—of EDC exposure, to date only a few studies have explored the potential multigenerational implications of EDC exposure in humans. These studies have only considered diethylstilbestrol exposure, and none has studied neurodevelopmental outcomes. Some studies have reported increased risk of hypospadias in grandsons of women exposed to diethylstilbestro during pregnancy. Titus-Ernstoff et al found delayed menstrual regularization, higher odds of irregular menstrual periods, and fewer live births among women whose grandmothers used diethylstilbestrol during pregnancy. Birth defects have also been found in grandchildren of women who used diethylstilbestrol when pregnant.

2018 Study Key Points

Question
Is exposure to diethylstilbestrol during pregnancy associated with adverse multigenerational neurodevelopmental outcomes?

Findings
A cohort study of 47 450 women in the Nurses’ Health Study II found significantly elevated odds for attention-deficit/hyperactivity disorder in the grandchildren (third generation) of users of diethylstilbestrol, a potent endocrine disruptor.

Meaning
Exposure to endocrine disruptors during pregnancy may be associated with multigenerational neurodevelopmental deficits.

IMPORTANCE

Animal evidence suggests that endocrine disruptors affect germline cells and neurodevelopment. However, to date, the third-generation neurodevelopmental outcomes in humans have not been examined.

OBJECTIVE

To explore the potential consequences of exposure to diethylstilbestrol or DES across generations—specifically, third-generation neurodevelopment.

DESIGN, SETTING, AND PARTICIPANTS

This cohort study uses self-reported health information, such as exposure to diethylstilbestrol during pregnancy and attention-deficit/hyperactivity disorder (ADHD) diagnosis, from 47 540 participants enrolled in the ongoing Nurses’ Health Study II. The 3 generations analyzed in this study were the participants (F1 generation), their mothers (F0 generation), and their live-born children (F2 generation). MAIN OUTCOMES AND MEASURES Participant- and mother-reported exposure to diethylstilbestrol during pregnancy and physician-diagnosed child ADHD.

RESULTS

The total number of women included in this study was 47 540. Of the 47 540 F0 mothers, 861 (1.8%) used diethylstilbestrol and 46 679 (98.2%) did not while pregnant with the F1 participants. Use of diethylstylbestrol by F0 mothers was associated with an increased risk of ADHD among the F2 generation: 7.7% vs 5.2%, adjusted odds ratio (OR), 1.36 (95% CI, 1.10-1.67) and an OR of 1.63 (95% CI, 1.18-2.25) if diethylstilbestrol was taken during the first trimester of pregnancy. No effect modification was observed by the F2 children’s sex.

CONCLUSIONS AND RELEVANCE

This study provides evidence that diethylstilbestrol exposure is associated with multigenerational neurodevelopmental deficits. The doses and potency level of environmental endocrine disruptors to which humans are exposed are lower than those of diethylstilbestrol, but the prevalence of such exposure and the possibility of cumulative action are potentially high and thus warrant consideration.

Sources

  • Full study (free access) : Association of Exposure to Diethylstilbestrol During Pregnancy With Multigenerational Neurodevelopmental Deficits, JAMA Pediatrics doi:10.1001/jamapediatrics.2018.0727, May 21, 2018.
  • Featured image by Andre Hunter.
DES DIETHYLSTILBESTROL RESOURCES