Admixture mapping of uterine fibroid size and number in African American women

Racial disparity in uterine leiomyoma: new insights of genetic and environmental burden in myometrial cells

Uterine leiomyoma (LM), also known as uterine fibroids, are common gynecological tumors and can reach a prevalence of 70% among women by the age of 50 years. Notably, the LM burden is much higher in Black women with earlier onset, a greater tumor number, size, and severity compared to White women. Published knowledge shows that there are genetic, environmental, and lifestyle-based risk factors associated with racial disparity for LM. Significant strides have been made on genomic, epigenomic, and transcriptomic data levels in Black and White women to elucidate the underlying pathomolecular reasons of racial disparity in LM development. However, racial disparity of LM remains a major area of concern in gynecological research. This review highlights risk factors of LM and their role in different races. Furthermore, we discuss the genetics and uterine myometrial microenvironment in LM development. Comparative findings revealed that a major racial difference in the disease is linked to myometrial oxidative burden and altered ROS pathways which is relevant to the oxidized guanine in genomic DNA and MED12 mutations that drive the LM genesis. Considering the burden and morbidity of LM, we anticipate that this review on genetic risk and myometrial microenvironment will strengthen understanding and propel the growth of research to address the racial disparity of LM burden.

EVALUATING THE RELATIONSHIPS BETWEEN GENETIC ANCESTRY AND THE CLINICAL PHENOME

There is a desire in research to move away from the concept of race as a clinical factor because it is a societal construct used as an imprecise proxy for geographic ancestry. In this study, we leverage the biobank from Vanderbilt University Medical Center, BioVU, to investigate relationships between genetic ancestry proportion and the clinical phenome. For all samples in BioVU, we calculated six ancestry proportions based on 1000 Genomes references: eastern African (EAFR), western African (WAFR), northern European (NEUR), southern European (SEUR), eastern Asian (EAS), and southern Asian (SAS). From PheWAS, we found phecode categories significantly enriched neoplasms for EAFR, WAFR, and SEUR, and pregnancy complication in SEUR, NEUR, SAS, and EAS (p < 0.003). We then selected phenotypes hypertension (HTN) and atrial fibrillation (AFib) to further investigate the relationships between these phenotypes and EAFR, WAFR, SEUR, and NEUR using logistic regression modeling and non-linear restricted cubic spline modeling (RCS). For EAS and SAS, we chose renal failure (RF) for further modeling. The relationships between HTN and AFib and the ancestries EAFR, WAFR, and SEUR were best fit by the linear model (beta p < 1x10-4 for all) while the relationships with NEUR were best fit with RCS (HTN ANOVA p = 0.001, AFib ANOVA p < 1x10-4). For RF, the relationship with SAS was best fit with a linear model (beta p < 1x10-4) while RCS model was a better fit for EAS (ANOVA p < 1x10-4). In this study, we identify relationships between genetic ancestry and phenotypes that are best fit with non-linear modeling techniques. The assumption of linearity for regression modeling is integral for proper fitting of a model and there is no knowing a priori to modeling if the relationship is truly linear.

Uterine leiomyomata and keloids fibrosis origins: a mini-review of fibroproliferative diseases

Diseases such as uterine leiomyomata (fibroids and benign tumors of the uterus) and keloids (raised scars) may share common etiology. Fibroids and keloids can co-occur in individuals, and both are highly heritable, suggesting they may share common genetic risk factors. Fibroproliferative diseases are common and characterized by scarring and overgrowth of connective tissue, impacting multiple organ systems. These conditions both have racial disparities in prevalence, with the highest prevalence observed among individuals of African ancestry. Several fibroproliferative diseases are more severe and common in populations of sub-Saharan Africa. This mini-review aims to provide a broad overview of the current knowledge of the evolutionary origins and causes of fibroproliferative diseases. We also discuss current hypotheses proposing that the increased prevalence of these diseases in African-derived populations is due to the selection for profibrotic alleles that are protective against helminth infections and provide examples from knowledge of uterine fibroid and keloid research.

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.

Uterine Weight as a Modifier of Black/White Racial Disparities in Minimally Invasive Hysterectomy Among Veterans with Fibroids in the Veterans Health Administration

Introduction

Uterine fibroids are the most common indication for hysterectomy. Minimally invasive hysterectomy (MIH) confers lower risk of complications and shorter recovery than open surgical procedures; however, it is more challenging to perform with larger fibroids. There are racialized differences in fibroid size and MIH rates. We examined the role of uterine size in black-white differences in MIH among Veterans in the Department of Veterans Affairs (VA).

Methods

Using VA clinical and administrative data, we conducted a cross-sectional study among black and white Veterans with fibroids who underwent hysterectomy between 2012 and 2014. We abstracted postoperative uterine weight from pathology reports as a proxy for uterine size. We used a generalized linear model to estimate the association between race and MIH and tested an interaction between race and postoperative uterine weight (≤250 g vs. >250 g). We estimated adjusted marginal effects for racial differences in MIH by postoperative uterine weight.

Results

The sample included 732 Veterans (60% black, 40% white). Postoperative uterine weight modified the association of race and MIH (p for interaction=0.05). Black Veterans with postoperative uterine weight ≤250 g had a nearly 12-percentage point decrease in MIH compared to white Veterans (95% CI -23.1 to -0.5), with no difference by race among those with postoperative uterine weight >250 g.

Discussion

The racial disparity among Veterans with small fibroids who should be candidates for MIH underscores the role of other determinants beyond uterine size. To eliminate disparities in MIH, research focused on experiences of black Veterans, including pathways to treatment and provider-patient interactions, is needed.

Perceptions of Ethnoracial Factors in the Management and Treatment of Uterine Fibroids

BACKGROUND

Uterine fibroids are non-cancerous neoplasms of the uterus. Women of color, including non-Hispanic Black/African American women and Hispanic/Latinas, have a higher uterine fibroid prevalence, incidence, and disease burden compared to non-Hispanic White women. Therefore, understanding ethnoracial factors in the diagnosis and treatment of uterine fibroids in women of color is critical. This study provides insight on the ethnoracial factors and cultural barriers experienced by women of color in the management and treatment of uterine fibroids.

METHODS

Women were recruited via The Fibroid Foundation, a nonprofit that provides uterine fibroid support and education. Women who were interested completed an online screening survey. Eligible participants were interviewed via phone. Transcribed audio recordings were qualitatively analyzed using the principles of grounded theory.

RESULTS

Forty-seven women of reproductive age who were diagnosed with uterine fibroids and received U.S.-based care participated in a semi-structured interview exploring experiences with uterine fibroid diagnosis and management. Twenty-eight women self-identified as Black, Latina, or other ethnicity. Women of color reported fibroid symptoms that significantly disrupted their work and home life. Women of color also reported perceptions that their race/ethnicity impacted their uterine fibroid treatment, including negative interpersonal provider-patient interactions. These perceptions engendered feelings of skepticism towards the medical system based on historical injustices and/or their own negative experiences and led some to go without longitudinal care.

CONCLUSION

Cultural and familial factors have significant impact on uterine fibroid diagnosis and management. Greater attention to culturally sensitive care and potential bias reduction in the treatment of uterine fibroids should be a priority.

The Impact of Uterine Fibroids on Fertility: How the Uncertainty Widens the Gap in Reproductive Outcomes in Black Women

Uterine fibroids (UFs) are the most common pelvic tumor in women. While the decreased quality of life and significant morbidity has been implicated with UFs, several important questions regarding the effect of UFs on reproductive outcomes remain unanswered. Furthermore, there is a disproportionate impact of UFs in Black women, in whom these tumors are known to be more common and more severe. The racial difference in UF burden is heightened during prime reproductive years, during which Black women undergo surgical intervention at an astoundingly increased rate compared to other races. Despite this, Black women are underrepresented in UF and treatment outcome research, and thus the uncertainty of the impact of UFs and UF treatment on fertility and pregnancy outcomes in this population is less defined. The purpose of this review article is to discuss recent findings in the literature regarding the impact of uterine UFs on reproductive outcomes with a primary focus on the implications for Black women. Additionally, we briefly discuss the importance of increased UF research funding and investigation and propose actionable items to help increase the representation of Black women in UF research.

Epigenomic and enhancer dysregulation in uterine leiomyomas

BACKGROUND

Uterine leiomyomas, also known as uterine fibroids or myomas, are the most common benign gynecological tumors and are found in women of reproductive and postmenopausal age. There is an exceptionally high prevalence of this tumor in women by the age of 50 years. Black women are particularly affected, with an increased incidence, earlier age of onset, larger and faster growing fibroids and greater severity of symptoms as compared to White women. Although advances in identifying genetic and environmental factors to delineate these fibroids have already been made, only recently has the role of epigenomics in the pathogenesis of this disease been considered.

OBJECTIVE AND RATIONALE

Over recent years, studies have identified multiple epigenomic aberrations that may contribute to leiomyoma development and growth. This review will focus on the most recent discoveries in three categories of epigenomic changes found in uterine fibroids, namely aberrant DNA methylation, histone tail modifications and histone variant exchange, and their translation into altered target gene architecture and transcriptional outcome. The findings demonstrating how the altered 3D shape of the enhancer can regulate gene expression from millions of base pairs away will be discussed. Additionally, translational implications of these discoveries and potential roadblocks in leiomyoma treatment will be addressed.

SEARCH METHODS

A comprehensive PubMed search was performed to identify published articles containing keywords relevant to the focus of the review, such as: uterine leiomyoma, uterine fibroids, epigenetic alterations, epigenomics, stem cells, chromatin modifications, extracellular matrix [ECM] organization, DNA methylation, enhancer, histone post-translational modifications and dysregulated gene expression. Articles until September 2021 were explored and evaluated to identify relevant updates in the field. Most of the articles focused on in the discussion were published between 2015 and 2021, although some key discoveries made before 2015 were included for background information and foundational purposes. We apologize to the authors whose work was not included because of space restrictions or inadvertent omission.

OUTCOMES

Chemical alterations to the DNA structure and of nucleosomal histones, without changing the underlying DNA sequence, have now been implicated in the phenotypic manifestation of uterine leiomyomas. Genome-wide DNA methylation analysis has revealed subsets of either suppressed or overexpressed genes accompanied by aberrant promoter methylation. Furthermore, differential promoter access resulting from altered 3D chromatin structure and histone modifications plays a role in regulating transcription of key genes thought to be involved in leiomyoma etiology. The dysregulated genes function in tumor suppression, apoptosis, angiogenesis, ECM formation, a variety of cancer-related signaling pathways and stem cell differentiation. Aberrant DNA methylation or histone modification is also observed in altering enhancer architecture, which leads to changes in enhancer-promoter contact strength, producing novel explanations for the overexpression of high mobility group AT-hook 2 and gene dysregulation found in mediator complex subunit 12 mutant fibroids. While many molecular mechanisms and epigenomic features have been investigated, the basis for the racial disparity observed among those in the Black population remains unclear.

WIDER IMPLICATIONS

A comprehensive understanding of the exact pathogenesis of uterine leiomyoma is lacking and requires attention as it can provide clues for prevention and viable non-surgical treatment. These findings will widen our knowledge of the role epigenomics plays in the mechanisms related to uterine leiomyoma development and highlight novel approaches for the prevention and identification of epigenome targets for long-term non-invasive treatment options of this significantly common disease.

Evidence that geographic variation in genetic ancestry associates with uterine fibroids

Uterine fibroids disproportionately impact Black women. Evidence suggests Black women have earlier onset and higher cumulative risk. This risk disparity may be due an imbalance of risk alleles in one parental geographic ancestry subgroup relative to others. We investigated ancestry proportions for the 1000 Genomes phase 3 populations clustered into 6 geographic groups for association with fibroid traits in Black women (n=583 cases, 797 controls) and White women (n=1,195 cases, 1,164 controls). Global ancestry proportions were estimated using ADMIXTURE. Dichotomous (fibroids status and multiple fibroid status) and continuous outcomes (volume and largest dimension) were modeled for association with ancestry proportions using logistic and linear regression adjusting for age. Effect estimates are reported per 10% increase in genetically inferred ancestry proportion. Among AAs, West African (WAFR) ancestry was associated with fibroid risk, East African ancestry was associated with risk of multiple fibroids, Northern European (NEUR) ancestry was protective for multiple fibroids, Southern European ancestry was protective for fibroids and multiple fibroids, and South Asian (SAS) ancestry was positively associated with volume and largest dimension. In EAs, NEUR ancestry was protective for fibroids, SAS ancestry was associated with fibroid risk, and WAFR ancestry was positively associated with volume and largest dimension. These results suggest that a proportion of fibroid risk and fibroid trait racial disparities are due to genetic differences between geographic groups. Further investigation at the local ancestry and single variant levels may yield novel insights about disease architecture and genetic mechanisms underlying ethnic disparities in fibroid risk.

Associations between Race/Ethnicity, Uterine Fibroids, and Minimally Invasive Hysterectomy in the VA Healthcare System

BACKGROUND

In the general population, Black and Latina women are less likely to undergo minimally invasive hysterectomy than White women, which may be related to racial/ethnic variation in fibroid prevalence and characteristics. Whether similar differences exist in the Department of Veterans Affairs Healthcare System (VA) is unknown.

METHODS

Using VA clinical and administrative data, we identified all women veterans undergoing hysterectomy for benign indications in fiscal years 2012-2014. We identified hysterectomy route (laparoscopic with/without robot-assist, vaginal, abdominal) by International Classification of Diseases, 9th edition, codes. We used multinomial logistic regression to estimate associations of race/ethnicity with hysterectomy route and tested whether associations varied by fibroid diagnosis using an interaction term. Models adjusted for age, income, body mass index, gynecologic diagnoses, medical comorbidities, whether procedure was performed or paid for by VA, geographic region, and fiscal year.

RESULTS

Among 2,744 identified hysterectomies, 53% were abdominal, 29% laparoscopic, and 18% vaginal. In multinomial models, racial/ethnic differences were present among veterans with but not without fibroid diagnoses (p value for interaction < .001). Among veterans with fibroids, Black veterans were less likely than White veterans to have minimally invasive hysterectomy (laparoscopic vs. abdominal relative risk ratio [RRR], 0.52; 95% CI, 0.38-0.72; vaginal vs. abdominal RRR, 0.58; 95% CI, 0.43-0.73). Latina veterans were as likely as White veterans to have laparoscopic as abdominal hysterectomy (RRR, 1.34; 95% CI, 0.87-2.07) and less likely to have vaginal than abdominal hysterectomy (RRR, 0.32; 95% CI, 0.15-0.69).

CONCLUSIONS

Receipt of minimally invasive hysterectomy among women veterans with fibroids varied by race/ethnicity. Further investigation of the underlying mechanisms and potential interventions to increase minimally invasive hysterectomy among minority women veterans is needed.

Transethnic and race-stratified genome-wide association study of fibroid characteristics in African American and European American women

OBJECTIVE

To identify, through genome-wide association studies, genetic loci that associate with differences in fibroid size and number in a population of African American and European American women.

DESIGN

Cross-sectional study.

SETTING

Not applicable.

PATIENT(S)

Using BioVU, a clinical population from the Vanderbilt University Medical Center, and the Coronary Artery Risk Development in Young Adults cohort, a prospective cohort, we identified 1520 women (609 African American and 911 European American) with documented fibroid characteristics.

INTERVENTION(S)

None.

MAIN OUTCOME MEASURE(S)

Outcome measurements include volume of largest fibroid, largest fibroid dimension, and number of fibroids (single vs. multiple).

RESULT(S)

In race-stratified analyses we achieved genome-wide significance at a variant located between MAT2B and TENM2 (rs57542984, β = 0.13; 95% confidence interval 0.09, 0.17) for analyses of largest fibroid dimension in African Americans. The strongest signal for transethnic analyses was at a variant on 1q31.1 located between PLA2G4A and BRINP3 (rs6605005, β = 0.24; 95% confidence interval 0.15, 0.33) for fibroid volume. Results from MetaXcan identified an association between predicted expression of the gene ER degradation enhancing alpha-mannosidase like protein 2 (EDEM2) in the thyroid and number of fibroids (Z score = -4.51).

CONCLUSION(S)

This study identified many novel associations between genetic loci and fibroid size and number in both race-stratified and transethnic analyses. Future studies are necessary to further validate our study findings and to better understand the mechanisms underlying these associations.