Early Life Adverse Environmental Exposures Increase the Risk of Uterine Fibroid Development: Role of Epigenetic Regulation

Thyroid cancer risk in women after hysterectomy: A nationwide cohort study

OBJECTIVES

Hysterectomy is commonly performed for benign uterine pathologies but there is some controversy over whether it is associated with an increased risk of thyroid cancer. This study examines the associations of hysterectomy with ovarian conservation or with bilateral salpingo-oophorectomy and thyroid cancer incidence in Taiwan.

METHODS

We analyzed data from a nationwide health insurance claims database and identified 29,577 women aged ≥30 years who underwent hysterectomy with ovarian conservation or hysterectomy with bilateral salpingo-oophorectomy between 2000 and 2016. Propensity score-matching analyses were performed at ratios of 1:1 for the hysterectomy and no-hysterectomy groups, to reduce selection bias. We monitored thyroid cancer occurrence in both groups until 2017. Cox regression was used to calculate hazard ratios with 95 % confidence intervals and determine thyroid cancer risk in women who underwent hysterectomy.

RESULTS

The study comprised 29,577 patients who underwent any hysterectomy and 29,577 participants who did not. The mean follow-up period was 10.03 ± 4.92 years. Patients who underwent hysterectomy had higher thyroid cancer incidence (4.72 per 10,000 person-years) than those who did not (3.06 per 10,000 person-years) and a greater risk of any thyroid cancer (adjusted hazard ratio = 1.40; 95 % confidence interval = 1.08-1.82). However, there was no association between hysterectomy with bilateral salpingo-oophorectomy and thyroid cancer incidence (p > 0.05).

CONCLUSIONS

Our findings suggest that women who undergo hysterectomy are at a higher risk of developing thyroid cancer than those who do not.

Targeting Bromodomain-Containing Protein 9 in Human Uterine Fibroid Cells

Bromodomain (BRD)-containing proteins are evolutionarily conserved protein-protein interaction modules involved in many biological processes. BRDs selectively recognize and bind to acetylated lysine residues, particularly in histones, and thereby have a crucial role in the regulation of gene expression. BRD protein dysfunction has been linked to many diseases, including tumorigenesis. Previously, we reported the critical role of BRD-containing protein 9 (BRD9) in the pathogenesis of UFs. The present study aimed to extend our previous finding and further understand the role of the BRD9 in UFs. Our studies demonstrated that targeted inhibition of BRD9 with its potent inhibitor TP-472 inhibited the pathogenesis of UF through increased apoptosis and proliferation arrest and decreased extracellular matrix deposition in UF cells. High-throughput transcriptomic analysis further and extensively demonstrated that targeted inhibition of BRD9 by TP-472 impacted the biological pathways, including cell cycle progression, inflammatory response, E2F targets, ECM deposition, and m6A reprogramming. Compared with the previous study, we identified common enriched pathways induced by two BRD9 inhibitors, I-BRD9 and TP-472. Taken together, our studies further revealed the critical role of BRD9 in UF cells. We characterized the link between BRD9 and other vital pathways, as well as the connection between epigenetic and epitranscriptome involved in UF progression. Targeted inhibition of BRD proteins might provide a non-hormonal treatment strategy for this most common benign tumor in women of reproductive age.

Environmental pollutants and exosomes: A new paradigm in environmental health and disease

This study investigates the intricate interplay between environmental pollutants and exosomes, shedding light on a novel paradigm in environmental health and disease. Cellular stress, induced by environmental toxicants or disease, significantly impacts the production and composition of exosomes, crucial mediators of intercellular communication. The heat shock response (HSR) and unfolded protein response (UPR) pathways, activated during cellular stress, profoundly influence exosome generation, cargo sorting, and function, shaping intercellular communication and stress responses. Environmental pollutants, particularly lipophilic ones, directly interact with exosome lipid bilayers, potentially affecting membrane stability, release, and cellular uptake. The study reveals that exposure to environmental contaminants induces significant changes in exosomal proteins, miRNAs, and lipids, impacting cellular function and health. Understanding the impact of environmental pollutants on exosomal cargo holds promise for biomarkers of exposure, enabling non-invasive sample collection and real-time insights into ongoing cellular responses. This research explores the potential of exosomal biomarkers for early detection of health effects, assessing treatment efficacy, and population-wide screening. Overcoming challenges requires advanced isolation techniques, standardized protocols, and machine learning for data analysis. Integration with omics technologies enhances comprehensive molecular analysis, offering a holistic understanding of the complex regulatory network influenced by environmental pollutants. The study underscores the capability of exosomes in circulation as promising biomarkers for assessing environmental exposure and systemic health effects, contributing to advancements in environmental health research and disease prevention.

Racial disparities between measures of area deprivation and financial toxicity, and uterine volume in myomectomy patients

BACKGROUND

At time of myomectomy, a surgical procedure to remove uterine fibroids, Black women tend to have larger uteri than White women. This makes Black patients less likely to undergo a minimally invasive myomectomy which has been shown to have less postoperative pain, less frequent postoperative fever and shorter length of stay compared to abdominal myomectomies. The associations between individual financial toxicity and community area deprivation and uterine volume at the time of myomectomy have not been investigated.

METHODS

We conducted a secondary data analysis of patients with fibroids scheduled for myomectomy using data from a fibroid treatment registry in [location]. We used validated measures of individual-level Financial Toxicity (higher scores = better financial status) and community-level Area Deprivation (ADI, high scores = worse deprivation). To examine associations with log transformed uterine volume, we used linear regression clustered on race (Black vs. White).

RESULTS

Black participants had worse financial toxicity, greater deprivation and larger uterine volumes compared with White participants. A greater Financial Toxicity score (better financial status) was associated with lower uterine volume. For every 10 unit increase in Financial Toxicity, the mean total uterine volume decreased by 9.95% (Confidence Interval [CI]: -9.95%, -3.99%). ADI was also associated with uterine volume. A single unit increase in ADI (worse deprivation) was associated with a 5.13% (CI: 2.02%, 7.25%) increase in mean uterine volume.

CONCLUSION

Disproportionately worse Financial Toxicity and ADI among Black patients is likely due to structural racism - which now must be considered in gynecologic research and practice.

TRIAL REGISTRATION

Not applicable.

TGFβ signaling links early life endocrine-disrupting chemicals exposure to suppression of nucleotide excision repair in rat myometrial stem cells

Environmental exposure to endocrine-disrupting chemicals (EDCs) is linked to the development of uterine fibroids (UFs) in women. UFs, non-cancerous tumors, are thought to originate from abnormal myometrial stem cells (MMSCs). Defective DNA repair capacity may contribute to the emergence of mutations that promote tumor growth. The multifunctional cytokine TGFβ1 is associated with UF progression and DNA damage repair pathways. To investigate the impact of EDC exposure on TGFβ1 and nucleotide excision repair (NER) pathways, we isolated MMSCs from 5-month-old Eker rats exposed neonatally to diethylstilbestrol (DES), an EDC, or to vehicle (VEH). EDC-MMSCs exhibited overactivated TGFβ1 signaling and reduced mRNA and protein levels of NER pathway components compared to VEH-MMSCs. EDC-MMSCs also demonstrated impaired NER capacity. Exposing VEH-MMSCs to TGFβ1 decreased NER capacity while inhibiting TGFβ signaling in EDC-MMSCs restored it. RNA-seq analysis and further validation revealed decreased expression of Uvrag, a tumor suppressor gene involved in DNA damage recognition, in VEH-MMSCs treated with TGFβ1, but increased expression in EDC-MMSCs after TGFβ signaling inhibition. Overall, we demonstrated that the overactivation of the TGFβ pathway links early life exposure to EDCs with impaired NER capacity, which would lead to increased genetic instability, arise of mutations, and fibroid tumorigenesis. We demonstrated that the overactivation of the TGFβ pathway links early life exposure to EDCs with impaired NER capacity, which would lead to increased fibroid incidence.

Developmental reprogramming of myometrial stem cells by endocrine disruptor linking to risk of uterine fibroids

BACKGROUND

The stage, when tissues and organs are growing, is very vulnerable to environmental influences, but it's not clear how exposure during this time causes changes to the epigenome and increases the risk of hormone-related illnesses like uterine fibroids (UFs).

METHODS

Developmental reprogramming of myometrial stem cells (MMSCs), the putative origin from which UFs originate, was investigated in vitro and in the Eker rat model by RNA-seq, ChIP-seq, RRBS, gain/loss of function analysis, and luciferase activity assays.

RESULTS

When exposed to the endocrine-disrupting chemical (EDC) diethylstilbestrol during Eker rat development, MMSCs undergo a reprogramming of their estrogen-responsive transcriptome. The reprogrammed genes in MMSCs are known as estrogen-responsive genes (ERGs) and are activated by mixed lineage leukemia protein-1 (MLL1) and DNA hypo-methylation mechanisms. Additionally, we observed a notable elevation in the expression of ERGs in MMSCs from Eker rats exposed to natural steroids after developmental exposure to EDC, thereby augmenting estrogen activity.

CONCLUSION

Our studies identify epigenetic mechanisms of MLL1/DNA hypo-methylation-mediated MMSC reprogramming. EDC exposure epigenetically targets MMSCs and leads to persistent changes in the expression of a subset of ERGs, imparting a hormonal imprint on the ERGs, resulting in a "hyper-estrogenic" phenotype, and increasing the hormone-dependent risk of UFs.

Epigenetic Modulation of Inflammatory Pathways in Myometrial Stem Cells and Risk of Uterine Fibroids

The period during which tissue and organ development occurs is particularly vulnerable to the influence of environmental exposures. However, the specific mechanisms through which biological pathways are disrupted in response to developmental insults, consequently elevating the risk of hormone-dependent diseases, such as uterine fibroids (UFs), remain poorly understood. Here, we show that developmental exposure to the endocrine-disrupting chemical (EDC), diethylstilbestrol (DES), activates the inflammatory pathways in myometrial stem cells (MMSCs), which are the origin of UFs. Significantly, the secretome of reprogrammed MMSCs enhances the expression of critical inflammation-related genes in differentiated myometrial cells through the paracrine mechanism, which amplifies pro-inflammatory and immune suppression signaling in the myometrium. The expression of reprogrammed inflammatory responsive genes (IRGs) is driven by activated mixed-lineage leukemia protein-1 (MLL1) in MMSCs. The deactivation of MLL reverses the reprogramming of IRG expression. In addition, the inhibition of histone deacetylases (HDACs) also reversed the reprogrammed IRG expression induced by EDC exposure. This work identifies the epigenetic mechanisms of MLL1/HDAC-mediated MMSC reprogramming, and EDC exposure epigenetically targets MMSCs and imparts an IRG expression pattern, which may result in a "hyper-inflammatory phenotype" and an increased hormone-dependent risk of UFs later in life.

TGFβ signaling links early-life endocrine-disrupting chemicals exposure to suppression of nucleotide excision repair in rat myometrial stem cells

Environmental exposure to endocrine-disrupting chemicals (EDCs) is linked to the development of uterine fibroids (UFs) in women. UFs, non-cancerous tumors, are thought to originate from abnormal myometrial stem cells (MMSCs). Defective DNA repair capacity may contribute to the emergence of mutations that promote tumor growth. The multifunctional cytokine TGFβ1 is associated with UF progression and DNA damage repair pathways. To investigate the impact of EDC exposure on TGFβ1 and nucleotide excision repair (NER) pathways, we isolated MMSCs from 5-months old Eker rats exposed neonatally to Diethylstilbestrol (DES), an EDC, or to vehicle (VEH). EDC-MMSCs exhibited overactivated TGFβ1 signaling and reduced mRNA and protein levels of NER pathway components compared to VEH-MMSCs. EDC-MMSCs also demonstrated impaired NER capacity. Exposing VEH-MMSCs to TGFβ1 decreased NER capacity while inhibiting TGFβ signaling in EDC-MMSCs restored it. RNA-seq analysis and further validation revealed decreased expression of Uvrag, a tumor suppressor gene involved in DNA damage recognition, in VEH-MMSCs treated with TGFβ1, but increased expression in EDC-MMSCs after TGFβ signaling inhibition. Overall, we demonstrated that the overactivation of the TGFβ pathway links early-life exposure to EDCs with impaired NER capacity, which would lead to increased genetic instability, arise of mutations, and fibroid tumorigenesis. We demonstrated that the overactivation of the TGFβ pathway links early-life exposure to EDCs with impaired NER capacity, which would lead to increased fibroid incidence.

A View on Uterine Leiomyoma Genesis through the Prism of Genetic, Epigenetic and Cellular Heterogeneity

Uterine leiomyomas (ULs), frequent benign tumours of the female reproductive tract, are associated with a range of symptoms and significant morbidity. Despite extensive research, there is no consensus on essential points of UL initiation and development. The main reason for this is a pronounced inter- and intratumoral heterogeneity resulting from diverse and complicated mechanisms underlying UL pathobiology. In this review, we comprehensively analyse risk and protective factors for UL development, UL cellular composition, hormonal and paracrine signalling, epigenetic regulation and genetic abnormalities. We conclude the need to carefully update the concept of UL genesis in light of the current data. Staying within the framework of the existing hypotheses, we introduce a possible timeline for UL development and the associated key events—from potential prerequisites to the beginning of UL formation and the onset of driver and passenger changes.

Comprehensive Review of Uterine Fibroids: Developmental Origin, Pathogenesis, and Treatment

Uterine fibroids are benign monoclonal neoplasms of the myometrium, representing the most common tumors in women worldwide. To date, no long-term or noninvasive treatment option exists for hormone-dependent uterine fibroids, due to the limited knowledge about the molecular mechanisms underlying the initiation and development of uterine fibroids. This paper comprehensively summarizes the recent research advances on uterine fibroids, focusing on risk factors, development origin, pathogenetic mechanisms, and treatment options. Additionally, we describe the current treatment interventions for uterine fibroids. Finally, future perspectives on uterine fibroids studies are summarized. Deeper mechanistic insights into tumor etiology and the complexity of uterine fibroids can contribute to the progress of newer targeted therapies.

Cytogenomic Profile of Uterine Leiomyoma: In Vivo vs. In Vitro Comparison

We performed a comparative cytogenomic analysis of cultured and uncultured uterine leiomyoma (UL) samples. The experimental approach included karyotyping, aCGH, verification of the detected chromosomal abnormalities by metaphase and interphase FISH, MED12 mutation analysis and telomere measurement by Q-FISH. An abnormal karyotype was detected in 12 out of 32 cultured UL samples. In five karyotypically abnormal ULs, MED12 mutations were found. The chromosomal abnormalities in ULs were present mostly by complex rearrangements, including chromothripsis. In both karyotypically normal and abnormal ULs, telomeres were ~40% shorter than in the corresponding myometrium, being possibly prerequisite to chromosomal rearrangements. The uncultured samples of six karyotypically abnormal ULs were checked for the detected chromosomal abnormalities through interphase FISH with individually designed DNA probe sets. All chromosomal abnormalities detected in cultured ULs were found in corresponding uncultured samples. In all tumors, clonal spectra were present by the karyotypically abnormal cell clone/clones which coexisted with karyotypically normal ones, suggesting that chromosomal abnormalities acted as drivers, rather than triggers, of the neoplastic process. In vitro propagation did not cause any changes in the spectrum of the cell clones, but altered their ratio compared to uncultured sample. The alterations were unique for every UL. Compared to its uncultured counterpart, the frequency of chromosomally abnormal cells in the cultured sample was higher in some ULs and lower in others. To summarize, ULs are characterized by both inter- and intratumor genetic heterogeneity. Regardless of its MED12 status, a tumor may be comprised of clones with and without chromosomal abnormalities. In contrast to the clonal spectrum, which is unique and constant for each UL, the clonal frequency demonstrates up or down shifts under in vitro conditions, most probably determined by the unequal ability of cells with different genetic aberrations to exist outside the body.

Extracellular vesicle interactions with the external and internal exposome in mediating carcinogenesis

The influence of environmental factors on an individual, from conception onwards, is defined as the exposome. It can be categorized into the external exposome, which includes external factors such as air pollution, chemical contaminants, and diet, and the internal exposome, which is unique to an individual, and involves age, physiology, and their genetic profile. The effect of external exposures on the internal exposome, or genetic profile, can be determined through omics analyses. However, this is often compromised due to low sample quantity and cost. Therefore, identification of other factors that can provide an insight into the cellular profile of an individual, provides an exciting avenue, and an emerging field is that of extracellular vesicles (EVs). Recently, our understanding of how cells can communicate with each other has shifted to recognise the role of EVs. EVs are secreted by all living cells, and have been identified in all biological fluids studied so far. They transport bioactive molecules (e.g., proteins, miRNAs, and DNA), and their release can be regulated by the cellular microenvironment. Analysis of EVs in respond to environmental factors might provide novel insights into the role of tumour EVs in carcinogenesis. Not only will EVs give some insight into the tumour cells themselves but they will also provide a better understanding of how cells communicate with one another, contributing to cancer progression. Moreover, characterising the content and functions of tumour-derived EVs has the potential to overcome the current challenges to improve cancer patient outcomes. For example, the identification of EVs targets for therapeutic interventions and tumour EVs biomarkers could facilitate the development of early screening for several cancers. The aim of this review, thus, is to discuss the overall role of EVs in response to the various external and internal signals in cancer. We will specifically highlight the biogenesis, secretion, and content of EVs in response to oncogenic transformation and metabolic regulators in cancer.

Spatial Transcriptomics analysis of uterine gene expression in enhancer of Zeste homolog 2 (Ezh2) conditional knockout mice

Histone proteins undergo various modifications that alter chromatin structure, including addition of methyl groups. Enhancer of homolog 2 (EZH2), is a histone methyltransferase that methylates lysine residue 27, and thereby, suppresses gene expression. EZH2 plays integral role in the uterus and other reproductive organs. We have previously shown that conditional deletion of uterine EZH2 results in increased proliferation of luminal and glandular epithelial cells, and RNAseq analyses reveal several uterine transcriptomic changes in Ezh2 conditional (c) knockout (KO) mice that can affect estrogen signaling pathways. To pinpoint the origin of such gene expression changes, we used the recently developed spatial transcriptomics (ST) method with the hypotheses that Ezh2cKO mice would predominantly demonstrate changes in epithelial cells and/or ablation of this gene would disrupt normal epithelial/stromal gene expression patterns. Uteri were collected from ovariectomized adult WT and Ezh2cKO mice and analyzed by ST. Asb4, Cxcl14, Dio2, and Igfbp5 were increased, Sult1d1, Mt3, and Lcn2 were reduced in Ezh2cKO uterine epithelium vs. WT epithelium. For Ezh2cKO uterine stroma, differentially expressed key hub genes included Cald1, Fbln1, Myh11, Acta2, and Tagln. Conditional loss of uterine Ezh2 also appears to shift the balance of gene expression profiles in epithelial vs. stromal tissue toward uterine epithelial cell and gland development and proliferation, consistent with uterine gland hyperplasia in these mice. Current findings provide further insight into how EZH2 may selectively affect uterine epithelial and stromal compartments. Additionally, these transcriptome data might provide the mechanistic understanding and valuable biomarkers for human endometrial disorders with epigenetic underpinnings.

A-kinase anchoring protein 13 interacts with the vitamin D receptor to alter vitamin D-dependent gene activation in uterine leiomyoma cells

OBJECTIVE

To determine if A-kinase anchoring protein 13 (AKAP13) interacts with the vitamin D receptor (VDR) to alter vitamin D-dependent signaling in fibroid cells. Uterine leiomyomas (fibroids) are characterized by a fibrotic extracellular matrix and are associated with vitamin D deficiency. Treatment with vitamin D (1,25-dihydroxyvitamin D₃) reduces fibroid growth and extracellular matrix gene expression. A-kinase anchoring protein 13 is overexpressed in fibroids and interacts with nuclear hormone receptors, but it is not known whether AKAP13 may interact with the VDR to affect vitamin D signaling in fibroids.

DESIGN

Laboratory studies.

SETTING

Translational science laboratory.

INTERVENTION(S)

Human immortalized fibroid or myometrial cells were treated with 1,25-hydroxyvitamin D₃ (1,25(OH)₂D₃) and transfected using expression constructs for AKAP13 or AKAP13 mutants, RhoQL, C3 transferase, or small interfering ribonucleic acids (RNAs).

MAIN OUTCOME MEASURE(S)

Messenger ribonucleic acid (mRNA) levels of AKAP13, fibromodulin, and versican as measured by quantitative real-time polymerase chain reaction. Glutathione S-transferase-binding assays. Vitamin D-dependent gene activation as measured by luciferase assays.

RESULT(S)

1,25(OH)₂D₃ resulted in a significant reduction in mRNA levels encoding AKAP13, versican, and fibromodulin. Small interfering RNA silencing of AKAP13 decreased both fibromodulin and versican mRNA levels. Glutathione S-transferase-binding assays revealed that AKAP13 bound to the VDR through its nuclear receptor interacting region. Cotransfection of AKAP13 and VDR significantly reduced vitamin D-dependent gene activation. RhoA pathway inhibition partially relieved repression of vitamin D-dependent gene activation by AKAP13.

CONCLUSION(S)

These data suggest that AKAP13 inhibited the vitamin D receptor activation by a mechanism that required, at least in part, RhoA activation.

Emerging Roles of Long Non-coding RNAs in Uterine Leiomyoma Pathogenesis: a Review

Uterine leiomyoma (UL), as the most prevalent type of women's health disorders, is a benign tumor that originates from the smooth muscle cell layer of the uterus. A great number of associated complications are observed including infertility, miscarriage, bleeding, pain, dysmenorrhea, menorrhagia, and dyspareunia. Although the etiology of UL is largely undefined, environmental and genetic factors are witnessed to engage in the UL development. As long non-coding RNAs (lncRNAs) are involved in various types of cellular functions, in recent years, a great deal of attention has been drawn to them and their possible roles in UL pathogenesis. Moreover, they have illustrated their potential to be promising candidates for UL treatment. In this review paper, firstly, an overview of UL pathogenesis is presented. Then, the regulation of lncRNAs in UL and their possible mechanisms in cancer development are reviewed. Eventually, therapeutic approaches targeting lncRNAs in various cancers and UL are explored.

The influence of phenolic environmental estrogen on the transcriptome of uterine leiomyoma cells: A whole transcriptome profiling-based analysis

OBJECTIVE

The study aimed to recognize potential molecular targets and signal pathways whereby phenolic environmental estrogen promotes the proliferation of uterine leiomyoma cells.

METHODS

Primary cultured cell lines of uterine leiomyoma were treated with 0.1% DMSO, 10.0μmol/L Bisphenol A (BPA), and 32.0μmol/L Nonylphenol (NP) for 48 h before RNA-seq was performed. Those genes affected by BPA and NP were identified. Then, Gene Ontology (GO) enrichment, Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment, and Protein-protein Interaction (PPI) analysis were performed. Quantitative real-time polymerase chain reaction (q-PCR) and western blot were used to verify the differentially expressed gene and protein.

RESULTS

Compared to with the control group, 739 differentially expressed genes were identified in both the BPA group and the NP group. GO enrichment analysis showed that the most enriched GO terms were connective tissue development and G1/S transition of mitotic cell cycle, and extracellular matrix. The results of KEGG enrichment analysis showed that differentially expressed mRNA were enriched mainly in three primary pathways, including environmental information processing, human diseases, and cellular processes. The cell cycle, PI3K-Akt signaling pathway are significantly enriched. The q-PCR and western blot verified the cell cycle associated genes and proteins were upregulated in both BPA group and NP group. Both BPA and NP activated the PI3K-AKT signaling pathway.

CONCLUSION

Phenolic environmental estrogens may promote the proliferation and cell cycle progression of uterine leiomyoma cells through rapid non-genomic ER signaling, which leads to disordered cell cycle regulation and accelerates the transition of the cell cycle from G0/G1 phase to S phase. In addition, as an external stimulant, phenolic estrogen promotes the upregulation of inflammatory factors in uterine leiomyomas.

Uterine Fibroids and Diet

Uterine myomas or fibroids are the most common benign female tumors of the reproductive organs, associated with significant morbidity and quality of life impairment. Several epidemiological risk factors for their occurrence have been identified so far, including nutrition and dietary habits. In this investigation, authors reviewed, as a narrative review, the data about diet and uterine myoma development in order to homogenize the current data. A PubMed search was conducted for the years 1990–2020, using a combination of keywords of interest for the selected topic. The authors searched the databases, selecting the randomized clinical studies, the observational studies, and the basic (experimental), clinical, and epidemiological researches. Once they collected the articles, they analyzed them according to the number of citations of each article, starting from the most cited to the least cited articles. Subsequently, authors collected the data of each article and inserted them in the various research paragraphs, summarizing the data collected. In this way, they crossed the available data regarding the association between nutrition habits and dietary components and myoma onset and growth. Many nutrients and dietary habits are associated with myoma development risk. These factors include low intakes of fruit, vegetables, and vitamin D, as well as pollutants in food. Despite the available data on the influence of some foods on the development of fibroids, further research is mandatory to understand all the nutrition risk factors which contribute to myoma growth and how exactly these risk factors influence myoma pathogenesis.

Non-hormonal mediators of uterine fibroid growth

PURPOSE OF REVIEW

Uterine fibroids are the most common benign neoplasms of the female reproductive tract and one of the major public health concerns. Although most women with uterine fibroids are asymptomatic, over 30% of them will present with varying symptoms. This review focuses on the role of non-hormonal mediators and pathways in uterine fibroid biology. Furthermore, it provides data regarding the most recent findings in the field of compounds, which use those non-hormonal pathways in the medical therapy of uterine fibroids.

RECENT FINDINGS

Complex signaling pathway alterations are crucial for uterine fibroid development. The topic of the pathophysiology of uterine fibroids focuses mostly on steroids and other hormones. However, other very important pathways exist, and some of them are independent of hormones. Some of the most important pathways, which are non-hormonal, but in some cases still hormone-depended, include growth factors, cytokines and inflammation, Smad proteins, wingless type/β-catenin and others.

SUMMARY

Much more is known about hormonal than about non-hormonal signaling in uterine fibroids. Growth factors, early life exposure and inflammation are key factors in uterine fibroid biology. Numerous agents depend on those pathways and may find their place in the current and future therapy of uterine fibroids.

Role of DNA damage and repair mechanisms in uterine fibroid/leiomyomas: a review

There has been a significant annual increase in the number of cases of uterine leiomyomas or fibroids (UF) among women of all races and ages across the world. A fortune is usually spent by the healthcare sector for fibroid-related treatments and management. Molecular studies have established the higher mutational heterogeneity in UF as compared to normal myometrial cells. The contribution of DNA damage and defects in repair responses further increases the mutational burden on the cells. This in turn leads to genetic instability, associated with cancer risk and other adverse reproductive health outcomes. Such and many more growing bodies of literature have highlighted the genetic/molecular, biochemical and clinical aspects of UF; none the less there appear to be a lacuna bridging the bench to bed gap in addressing and preventing this disease. Presented here is an exhaustive review of not only the molecular mechanisms underlying the predisposition to the disease but also possible strategies to effectively diagnose, prevent, manage, and treat this disease.

The Roles of the Histone Protein Modifier EZH2 in the Uterus and Placenta

Epigenetic modifications regulate normal physiological, as well as pathological processes in various organs, including the uterus and placenta. Both organs undergo dramatic and rapid restructuring that depends upon precise orchestration of events. Epigenetic changes that alter transcription and translation of gene-sets regulate such responses. Histone modifications alter the chromatin structure, thereby affecting transcription factor access to gene promoter regions. Binding of histones to DNA is regulated by addition or removal of subunit methyl and other groups, which can inhibit or stimulate transcription. Enhancer of zeste homolog 2 (EZH2) is the catalytic subunit of polycomb repressive complex 2 (PRC2) that catalyzes tri-methylation of histone H3 at Lys 27 (H3K27me3) and subsequently suppresses transcription of genes bound by such histones. Uterine EZH2 expression exerts a critical role in development and function of this organ with deletion of this gene resulting in uterine hyperplasia and expression of cancer-associated transcripts. Elucidating the roles of EZH2 in uterus and placenta is essential as EZH2 dysregulation is associated with several uterine and placental pathologies. Herein, we discuss EZH2 functions in uterus and placenta, emphasizing its physiological and pathological importance.

Vitamin D3 Ameliorates DNA Damage Caused by Developmental Exposure to Endocrine Disruptors in the Uterine Myometrial Stem Cells of Eker Rats

Early-life exposure of the myometrium to endocrine-disrupting chemicals (EDCs) has been shown to increase the risk of uterine fibroid (UF) prevalence in adulthood. Vitamin D3 (VitD3) is an unique, natural compound that may reduce the risk of developing UFs. However, little is known about the role and molecular mechanism of VitD3 on exposed myometrial stem cells (MMSCs). We investigated the role and molecular mechanism underlying VitD3 action on DNA damage response (DDR) defects in rat MMSCs due to developmental exposure to diethylstilbestrol (DES), with the additional goal of understanding how VitD3 decreases the incidence of UFs later in life. Female newborn Eker rats were exposed to DES or a vehicle early in life; they were then sacrificed at 5 months of age (pro-fibroid stage) and subjected to myometrial Stro1+/CD44+ stem cell isolation. Several techniques were performed to determine the effect of VitD3 treatment on the DNA repair pathway in DES-exposed MMSCs (DES-MMSCs). Results showed that there was a significantly reduced expression of RAD50 and MRE11, key DNA repair proteins in DES-exposed myometrial tissues, compared to vehicle (VEH)-exposed tissues (p < 0.01). VitD3 treatment significantly decreased the DNA damage levels in DES-MMSCs. Concomitantly, the levels of key DNA damage repair members, including the MRN complex, increased in DES-MMSCs following treatment with VitD3 (p < 0.01). VitD3 acts on DNA repair via the MRN complex/ATM axis, restores the DNA repair signaling network, and enhances DDR. This study demonstrates, for the first time, that VitD3 treatment attenuated the DNA damage load in MMSCs exposed to DES and classic DNA damage inducers. Moreover, VitD3 targets primed MMSCs, suggesting a novel therapeutic approach for the prevention of UF development.

The Evolving Role of Natural Compounds in the Medical Treatment of Uterine Fibroids

Uterine fibroids (UFs) remain a significant health issue for many women, with a disproportionate impact on women of color, likely due to both genetic and environmental factors. The prevalence of UFs is estimated to be approximately 70% depending on population. UF-derived clinical symptoms include pelvic pain, excessive uterine bleeding, gastrointestinal and voiding problems, as well as impaired fertility. Nowadays numerous methods of UF treatment are available-from conservative treatment to invasive surgeries. Selecting an appropriate treatment option should be individualized and adjusted to the patient's expectations as much as possible. So far, the mainstay of treatment is surgery, but their negative impact of future fertility is clear. On the other hand, emerging new pharmaceutical options have significant adverse effects like liver function impairment, hot flashes, bone density loss, endometrial changes, and inability to attempt conception during treatment. Several natural compounds are found to help treat UFs and relieve their symptoms. In this review we summarize all the current available data about natural compounds that may be beneficial for patients with UFs, especially those who want to preserve their future fertility or have treatment while actively pursuing conception. Vitamin D, epigallocatechin gallate, berberine, curcumin, and others are being used as alternative UF treatments. Moreover, we propose the concept of using combined therapies of natural compounds on their own or combined with hormonal agents to manage UFs. There is a strong need for more human clinical trials involving these compounds before promoting widespread usage.

Environmental toxin exposure in polycystic ovary syndrome women and possible ovarian neoplastic repercussion

Purpose: Over the last two decades, increasing attention has been paid to environmental toxins and their effects on the female reproductive system. Endocrine disrupting chemicals (EDCs) are exogenous substances or mixtures that can mimic the action of steroid hormones and interfere with their metabolism. Advanced glycation end products (AGEs) are proinflammatory molecules that can interact with cell surface receptors and mediate the triggering of proinflammatory pathways and oxidative stress. The purpose of this review is to explore the effects of environmental toxin exposure in the pathogenesis of both polycystic ovary syndrome (PCOS) and OC (ovarian cancer), considered separately, and also to evaluate possible neoplastic ovarian repercussion after exposure in patients diagnosed with PCOS.Materials and methods: We searched PubMed for articles published in the English language with the use of the following MeSH search terms: "polycystic ovary syndrome" and "ovarian cancer" combined with "endocrine disruptors". Titles and abstracts were examined and full articles that met the selection criteria were retrieved. A manual search of review articles and cross-references completed the search.Results: Extensive data from different studies collected in recent years concerning the effects of EDC/AGE exposure have confirmed their role in the pathophysiology of both PCOS and OC. They favor PCOS/OC development through different mechanisms that finally lead to hormonal and metabolic disruption and epigenetic modifications.Conclusions: Environmental toxin exposure in PCOS women could favor neoplastic transformation by exacerbating and potentiating some PCOS features. Further research, although difficult, is needed in order to prevent further diffusion of these substances in the environment, or at least to provide adequate information to the population considered at risk.

Mice lacking uterine enhancer of zeste homolog 2 have transcriptomic changes associated with uterine epithelial proliferation

Enhancer of zeste homolog 2 (EZH2) is a histone methyltransferase that suppresses gene expression. Previously, we developed a conditional null model where EZH2 is knocked out in uterus. Deletion of uterine EZH2 increased proliferation of luminal and glandular epithelial cells. Herein, we used RNA-Seq in wild-type (WT) and EZH2 conditional knockout (Ezh2cKO) uteri to obtain mechanistic insights into the gene expression changes that underpin the pathogenesis observed in these mice. Ovariectomized adult Ezh2cKO mice were treated with vehicle (V) or 17β-estradiol (E2; 1 ng/g). Uteri were collected at postnatal day (PND) 75 for RNA-Seq or immunostaining for epithelial proliferation. Weighted gene coexpression network analysis was used to link uterine gene expression patterns and epithelial proliferation. In V-treated mice, 88 transcripts were differentially expressed (DEG) in Ezh2cKO mice, and Bmp5, Crabp2, Lgr5, and Sprr2f were upregulated. E2 treatment resulted in 40 DEG with Krt5, Krt15, Olig3, Crabp1, and Serpinb7 upregulated in Ezh2cKO compared with control mice. Transcript analysis relative to proliferation rates revealed two module eigengenes correlated with epithelial proliferation in WT V vs. Ezh2cKO V and WT E2 vs. Ezh2cKO E2 mice, with a positive relationship in the former and inverse in the latter. Notably, the ESR1, Wnt, and Hippo signaling pathways were among those functionally enriched in Ezh2cKO females. Current results reveal unique gene expression patterns in Ezh2cKO uterus and provide insight into how loss of this critical epigenetic regulator assumingly contributes to uterine abnormalities.

Endocrine disruptor exposure during development increases incidence of uterine fibroids by altering DNA repair in myometrial stem cells

Despite the major negative impact uterine fibroids (UFs) have on female reproductive health, little is known about early events that initiate development of these tumors. Somatic fibroid-causing mutations in mediator complex subunit 12 (MED12), the most frequent genetic alterations in UFs (up to 85% of tumors), are implicated in transforming normal myometrial stem cells (MSCs) into tumor-forming cells, though the underlying mechanism(s) leading to these mutations remains unknown. It is well accepted that defective DNA repair increases the risk of acquiring tumor-driving mutations, though defects in DNA repair have not been explored in UF tumorigenesis. In the Eker rat UF model, a germline mutation in the Tsc2 tumor suppressor gene predisposes to UFs, which arise due to "second hits" in the normal allele of this gene. Risk for developing these tumors is significantly increased by early-life exposure to endocrine-disrupting chemicals (EDCs), suggesting increased UF penetrance is modulated by early drivers for these tumors. We analyzed DNA repair capacity using analyses of related gene and protein expression and DNA repair function in MSCs from adult rats exposed during uterine development to the model EDC diethylstilbestrol. Adult MSCs isolated from developmentally exposed rats demonstrated decreased DNA end-joining ability, higher levels of DNA damage, and impaired ability to repair DNA double-strand breaks relative to MSCs from age-matched, vehicle-exposed rats. These data suggest that early-life developmental EDC exposure alters these MSCs' ability to repair and reverse DNA damage, providing a driver for acquisition of mutations that may promote the development of these tumors in adult life.

Uterine polyps, adenomyosis, leiomyomas, and endometrial receptivity

Endometrial polyps, adenomyosis, and leiomyomas are commonly encountered abnormalities frequently found in both fertile women and those with infertility. The clinician is frequently challenged to determine which of these entities, when found, is likely to impair fertility, and which are "innocent bystanders" unrelated to the problem at hand. Although removing an endometrial polyp may be seen as a relatively benign and safe intervention, myomectomy, and in particular adenomyomectomy, can be substantive surgical procedures, associated with their own potential for disrupting fertility. One of the mechanisms thought to be involved when these entities are contributing to infertility is an adverse impact on endometrial receptivity. Indeed polyps, adenomyosis, and leiomyomas have all been associated with an increased likelihood of abnormal endometrial molecular expressions thought to impair implantation and early embryo development. This review is designed to examine the relationship of these common entities to endometrial receptivity and to identify evidence gaps that should be considered when strategizing research initiatives. It is apparent that we have the tools necessary to fill these gaps, but it will be necessary to approach the issue in a strategic and coordinated fashion. It is likely that we will have to recognize the limitations of imaging alone and look to the evidence-based addition of molecular analysis to provide the individualized phenotyping of disease necessary for patient-specific treatment decisions.

Relation between hysterectomy, oophorectomy and the risk of incident differentiated thyroid cancer: The E3N cohort

BACKGROUND

Thyroid cancers are threefold more frequent in women than in men. A role of reproductive or hormonal factors has been suggested but with contradictory results. We investigated potential associations between history of hysterectomy, with or without oophorectomy, and history of benign gynaecological disease (uterine fibroids, endometriosis) and the incidence of differentiated thyroid cancer, in a large French prospective cohort.

METHODS

A total of 89 340 women from the E3N cohort were followed up between 1990 and 2012. Gynaecological diseases treated by surgery were self-reported. Thyroid cancers were validated by histological reports. Time-dependent covariates included smoking status, BMI and history of benign thyroid disease. Cox proportional hazard models with age as timescale were used to estimate Hazard Ratios (HR) and 95% confidence intervals (CI).

RESULTS

A total of 412 cases of thyroid cancer were diagnosed during follow-up. A history of hysterectomy was associated with an increased risk of differentiated thyroid cancer (adjusted HR=2.05; 95%CI: 1.65-2.55). The association was not altered after further adjustment for reproductive factors. Endometriosis, uterine polyps, ovarian cysts and oophorectomy without hysterectomy were not associated with the risk of thyroid cancer. A history of fibroids was also significantly related to the risk of thyroid cancer over the follow-up period (adjusted HR=1.91; 95%CI: 1.50-2.44) and the increased risk persisted after adjustment for history of hysterectomy.

CONCLUSIONS

Women who had either a history of fibroids or hysterectomy had an increased risk of differentiated thyroid cancer. These findings suggest shared biological mechanisms between fibroids and thyroid cancer, which deserve to be further dissected.

The emerging spectrum of early life exposure-related inflammation and epigenetic therapy

Early life exposure to a variety of insults during sensitive windows of development can reprogram normal physiological responses and alter disease susceptibility later in life. During this process, Inflammation triggered by a variety of adverse exposures plays an important role in the initiation and development of many types of diseases including tumorigenesis. This review article summaries the current knowledge about the role and mechanism of inflammation in development of diseases. In addition, epigenome alteration related to inflammation and treatment options using epigenetic modifiers are highlighted and discussed.

Expanding upon the Human Myometrial Stem Cell Hypothesis and the Role of Race, Hormones, Age, and Parity in a Profibroid Environment

Uterine fibroids (UFs) are clonal, hormonally regulated, benign smooth-muscle myometrial tumors that severely affect female reproductive health, although their unknown etiology limits effective care. UFs occur fourfold more commonly in African American women than in Caucasian women, and African American women generally have earlier disease onset and greater UF tumor burden, although the mechanism of this ethnic disparity has not been identified. Recent findings have linked cancer (ie, tumor) risk to increased tissue-specific stem cell division and self-renewal and suggest that somatic mutations in myometrial stem cells (MyoSCs) convert them into tumor-initiating cells, leading to UF. Specifically, preliminary results in paraffin-embedded myometrial tissues have shown increased STRO-1⁺/CD44⁺ MyoSCs in African American versus Caucasian women. Using specific methods of flow cytometry and automated quantitative pathology imaging, a large cohort of myometrial samples were investigated to determine how the STRO-1⁺/CD44⁺ MyoSCs change with regard to a patient's race, age, parity, fibroid and hormone statuses, and the location of UFs within the uterus. We confirmed that the STRO-1⁺/CD44⁺ MyoSC population is expanded in African American women, is correlated with parity and fibroid number, and fluctuates with cyclic menstrual cycle hormone changes and age. Our data suggest that an expanded MyoSC population increases the formation of tumor-initiating cells, ultimately contributing to increased UF prevalence and burden in African American women.

Exosomes in Toxicology: Relevance to Chemical Exposure and Pathogenesis of Environmentally Linked Diseases

Chronic exposure to environmental toxins has been known to initiate or aggravate various neurological disorders, carcinomas and other adverse health effects. Uptake by naïve cells of pathogenic factors such as danger-associated molecules, mRNAs, miRNAs or aggregated proteins leads to disruption in cellular homeostasis further resulting in inflammation and disease propagation. Although early research tended to focus solely on exosomal removal of unwanted cellular contents, more recent reports indicate that these nano-vesicles play an active role in intercellular signaling. Not only is the exosomal cargo cell type-specific, but it also differs between healthy and dying cells. Moreover, following exosome uptake by naïve cells, the contents from these vesicles can alter the fate of recipient cells. Since exosomes can traverse long distances, they can influence distantly located cells and tissues. This review briefly explores the role played by environmental toxins in stimulating exosome release in the context of progressive neurodegenerative diseases such as Alzheimer's, Parkinson's, and Huntington's, as well as certain cancers such as lung, liver, ovarian, and tracheal carcinomas.

Selective progesterone receptor modulators for fertility preservation in women with symptomatic uterine fibroids

Uterine fibroids (UFs, AKA leiomyoma) are the most important benign neoplastic threat to women's health, with costs up to hundreds of billions of health care dollars worldwide. Uterine fibroids caused morbidities exert a tremendous health toll, impacting the quality of life of women of all ethnicities, especially women of color. Clinical presentations include heavy vaginal bleeding, pelvic pain, bulk symptoms, subfertility, and obstetric complications. Current management strategies heavily lean toward surgical procedures; nonetheless, the choice of treatment is generally subject to patient's age and her desire to preserve future fertility. Women with UF who desire to maintain future fertility potential face a dilemma because of the limited treatment choices that are currently available to help them achieve that goal. Recently, ulipristal acetate the first of the promising family of oral selective progesterone receptor modulators has been approved for UF treatment in Europe, Canada, and several other countries and is under review for possible approval in the USA. In this review article, we discuss recent advances in the management options against UF with a bend toward oral effective long-term treatment alternatives who are particularly suited for those seeking to preserve their future fertility potential. We also explore the transformative concept of primary and secondary UF prevention using these new anti-UF agents. We envision a remarkable shift in the management of UF in future years from surgical/invasive treatment to orally administrated options; clearly, this potential shift will require additional intense clinical research.

Silencing of MED27 inhibits adrenal cortical carcinogenesis by targeting the Wnt/β-catenin signaling pathway and the epithelial-mesenchymal transition process

This study aimed to explore the effect of MED27 on the expression of epithelial-mesenchymal transition (EMT)-related proteins and β-catenin in adrenal cortical carcinoma (ACC). The functional mechanism of MED27 on ACC processes was also explored. The expression of MED27 was assessed by quantitative real-time polymerase chain reaction (qRT-PCR). siRNA was utilized to knockdown the expression of MED27. CCK8 assays were performed to evaluate SW-13 cell proliferation. Transwell assays were performed to assess the invasion ability, and wound healing assays were utilized to detect migration. A tumor xenograft mouse model was established to investigate the impact of silencing MED27 on tumor growth and metastasis. MED27 was highly expressed in ACC tissues and cells. Down-regulation of MED27 induced ACC cell apoptosis, and significantly attenuated ACC cell proliferation, invasion and metastasis in vivo and in vitro. MED27 knockdown regulated the expression of EMT-related proteins and Wnt/β-catenin signaling pathway-related proteins. Our study investigated the function and mechanism of MED27 and validated that MED27 plays a negative role in ACC occurrence and progression and could be utilized as a new therapeutic target in ACC prevention and treatment.

The uterine fibroid/myoma tumour: analysis of the global research architecture using density-equalizing mapping

Uterine fibroids can severely impact a woman's quality of life, result in significant morbidity and are a leading indication for hysterectomy. Many aspects of the disease remain largely obscure. Despite these knowledge gaps, no detailed maps of the global fibroid research architecture have yet been generated. This study used the NewQIS approach to assess worldwide research productivity, encompassing numerous aspects of the scientific output, quality and socioeconomic features. Regression analysis indicated an increase in fibroid research activity in the investigated time periods. Global research output was dominated by leading Western countries, with the USA at the forefront, but also by East Asian countries. Socioeconomic benchmarking revealed that Taiwan had the highest fibroid research activity per GDP, with a calculated average of 279.46 fibroid-related publications per 1000 billion USD GDP. Finland was the most active country with respect to research activity per population size. Subject area analyses revealed major differences in research focuses, for example 'Radiology, Nuclear Medicine and Medical Imaging' was assigned to 29.92% of South Korean and to only 10.38% of US-American publications. In conclusion, this analysis of global fibroid research activity illustrates a multitude of important features ranging from quantitative and semi-qualitative fibroid research aspects to socioeconomic benchmarking.

Literature Review on the Role of Uterine Fibroids in Endometrial Function

Uterine fibroids are benign uterine smooth muscle tumors that are present in up to 8 out of 10 women by the age of 50. Many of these women experience symptoms such as heavy and irregular menstrual bleeding, early pregnancy loss, and infertility. Traditionally believed to be inert masses, fibroids are now known to influence endometrial function at the molecular level. We present a comprehensive review of published studies on the effect of uterine fibroids on endometrial function. Our goal was to explore the current knowledge about how uterine fibroids interact with the endometrium and how these interactions influence clinical symptoms. Our review shows that submucosal fibroids produce a blunted decidualization response with decreased release of cytokines critical for implantation such as leukocyte inhibitory factor and cell adhesion molecules. Furthermore, fibroids alter the expression of genes relevant for implantation, such as bone morphogenetic protein receptor type II, glycodelin, among others. With regard to heavy menstrual bleeding, fibroids significantly alter the production of vasoconstrictors in the endometrium, leading to increased menstrual blood loss. Fibroids also increase the production of angiogenic factors such as basic fibroblast growth factor and reduce the production of coagulation factors resulting in heavy menses. Understanding the crosstalk between uterine fibroids and the endometrium will provide key insights into implantation and menstrual biology and drive the development of new and innovative therapeutic options for the management of symptoms in women with uterine fibroids.

Investigation of diethylstilbestrol residue level in human urine samples by a specific monoclonal antibody

Diethylstilbestrol (DES) is used as a kind of animal feed additive and affects people's health through the food chain. The purpose of this study is to detect the residue level of DES in 576 human urine samples directly. DES-BSA was used to immunize Balb/c mice. The monoclonal antibody was produced by hybridoma that was screened through cell fusion techniques. Finally, we developed the indirect competitive ELISA method to analyze 576 human urine samples from Zhejiang Province, China. The IC₅₀ of this method was 3.33 ng/mL. The LOD and LOQ were 0.16 and 0.54 ng/mL. Linear range of the standard curve was from LOD to 12.50 ng/mL. There was no cross-reactivity with two kinds of estrogens and two structural analogs with DES. Five hundred seventy-six urine samples were analyzed by the indirect competitive ELISA method, and the detection rate was 98.78%. The mean concentration and geometric mean were 4.70 and 3.50 ng/mL. The indirect competitive ELISA method based on monoclonal antibody was sensitive and reliable for the detection of DES in human urine samples. The results warned us to pay more attention to human health and food safety.

Developmental Exposure to Endocrine Disruptors Expands Murine Myometrial Stem Cell Compartment as a Prerequisite to Leiomyoma Tumorigenesis

Despite the high prevalence and major negative impact of uterine fibroids (UFs) on women's health, their pathogenesis remains largely unknown. While tumor-initiating cells have been previously isolated from UFs, the cell of origin for these tumors in normal myometrium has not been identified. We isolated cells with Stro1/CD44 surface markers from normal myometrium expressing stem cell markers Oct-4/c-kit/nanog that exhibited the properties of myometrial stem/progenitor-like cells (MSCs). Using a murine model for UFs, we showed that the cervix was a hypoxic "niche" and primary site (96%) for fibroid development in these animals. The pool size of these MSCs also responded to environmental cues, contracting with age and expanding in response to developmental environmental exposures that promote fibroid development. Translating these findings to women, the number of MSCs in unaffected human myometrium correlated with risk for developing UFs. Caucasian (CC) women with fibroids had increased numbers of MSCs relative to CC women without fibroids, and African-American (AA) women at highest risk for these tumors had the highest number of MSCs: AA-with fibroids > CC-with fibroids > AA-without fibroids > CC-without fibroids. These data identify Stro1⁺ /CD44⁺ MSCs as MSC/progenitor cell for UFs, and a target for ethnic and environmental factors that increase UF risk. Stem Cells 2017;35:666-678.

Endocrine-disrupting chemicals and uterine fibroids

Uterine fibroids are the most frequent gynecologic tumor, affecting 70% to 80% of women over their lifetime. Although these tumors are benign, they can cause significant morbidity and may require invasive treatments such as myomectomy and hysterectomy. Many risk factors for these tumors have been identified, including environmental exposures to endocrine-disrupting chemicals (EDCs) such as genistein and diethylstilbestrol. Uterine development may be a particularly sensitive window to environmental exposures, as some perinatal EDC exposures have been shown to increase tumorigenesis in both rodent models and human epidemiologic studies. The mechanisms by which EDC exposures may increase tumorigenesis are still being elucidated, but epigenetic reprogramming of the developing uterus is an emerging hypothesis. Given the remarkably high incidence of uterine fibroids and their significant impact on women's health, understanding more about how prenatal exposures to EDCs (and other environmental agents) may increase fibroid risk could be key to developing prevention and treatment strategies in the future.