Ethnic Variations in Uterine Leiomyoma Biology Are Not Caused By Differences in Myometrial Estrogen Receptor Alpha Levels

Medical treatment of uterine leiomyoma

Uterine leiomyomas (also called myomata or fibroids) are the most common gynecologic tumors in the United States. The prevalence of leiomyomas is at least 3 to 4 times higher among African American women than in white women. Pathologically, uterine leiomyomas are benign tumors that arise in any part of the uterus under the influence of local growth factors and sex hormones, such as estrogen and progesterone. These common tumors cause significant morbidity for women and they are considered to be the most common indication for hysterectomy in the world; they are also associated with a substantial economic impact on health care systems that amounts to approximately $2.2 billion/year in the United States alone. Uterine myomas cause several reproductive problems such as heavy or abnormal uterine bleeding, pelvic pressure, infertility, and several obstetrical complications including miscarriage and preterm labor. Surgery has traditionally been the gold standard for the treatment of uterine leiomyomas and has typically consisted of either hysterectomy or myomectomy. In recent years, a few clinical trials have evaluated the efficacy of orally administered medications for the management of leiomyoma-related symptoms. In the present review, we will discuss these promising medical treatments in further detail.

Ethnic distribution of estrogen receptor-alpha polymorphism is associated with a higher prevalence of uterine leiomyomas in black Americans

OBJECTIVE

To investigate whether polymorphisms in the estrogen receptor alpha (ERalpha) gene are associated with an increased risk of uterine leiomyomas (ULMs).

DESIGN

Genomic DNA was isolated from normal myometrium samples collected at the time of the hysterectomy.

SETTING

Volunteers in an academic research environment.

PATIENT(S)

One hundred ninety-eight women with surgically confirmed ULMs and 229 matched controls with nonfibroid uteri.

INTERVENTION(S)

Hysterectomy samples were collected from volunteers.

MAIN OUTCOME MEASURE(S)

The two PvuII and XbaI intronic polymorphisms in the ERalpha gene using polymerase chain reaction and restriction fragment length polymorphism.

RESULT(S)

The ERalpha PP genotype was associated with a significantly increased risk of ULM in black and white women, but not in Hispanic women. Women with the ERalpha PP genotype were 6.42 times (confidence limits 2.04-20.16) more likely to have ULMs than other genotypes. The ERalpha PP genotype was also significantly associated with larger tumor burden (>400 g). The overall prevalence of the PP genotype was significantly higher in black women (35%) than white (13%) or Hispanic (16%) women. Myometrial cell lines expressing the PP genotype exhibited enhanced proliferative response to estrogen in vitro compared with their pp counterparts.

CONCLUSION(S)

The ERalpha PP genotype is a genetic risk factor for ULM development among surgically treated women. The higher prevalence of this genotype in blacks might explain the increased occurrence of this tumor among black women.

Catechol-O-methyltransferase polymorphism is associated with increased uterine leiomyoma risk in different ethnic groups

OBJECTIVES

Uterine leiomyomas (ULMs) are estrogen-dependent tumors that are more common in African American women. The etiology for such ethnic disparity is currently unknown. Catechol-O-methyltransferase (COMT) is an essential enzyme in estrogen metabolism. In the current study, we investigated the association of the functional COMT Val158Met polymorphism with ULM in different ethnic groups. We also studied the biologic role of COMT in tumor formation in human and rat leiomyoma cell lines and the potential therapeutic utility of COMT inhibitors.

METHODS

The genotype frequencies of the functional COMT Val158Met polymorphism among participants with (186 women) or without (142 women) ULMs were compared, as was the differential ethnic distribution of that polymorphism using polymerase chain reaction (PCR) and restriction-fragment linkage polymorphism. Proliferation, Western blot, and reporter transactivation analyses were applied to myometrial and leiomyoma cells representative of different COMT genotypes.

RESULTS

Women with the high-activity COMT Val/Val genotype are 2.5 times more likely to develop ULMs than women with other genotypes (confidence interval, 1.017 to 6.151; P <.001). The prevalence of this genotype was significantly higher in African American women (47%) compared with white (19%) or Hispanic (30%) women (P = .003). Myometrial cell lines expressing the Val/Val genotype exhibited significantly enhanced responses to estrogen in proliferation and in estrogen-responsive element reporter assays. COMT-specific inhibitors reversed such a response and induced apoptosis. Myometrial specimens from Val/Val women demonstrated distinct estrogen-regulated gene expression that was consistent with enhanced proliferation and decreased apoptosis.

CONCLUSIONS

The high-activity COMT Val/Val genotype is associated with increased risk of ULM. Our results provide a possible explanation for the higher prevalence of ULMs among African American women and offer a potential new target for nonsurgical treatment using COMT inhibitors.

Hormonal regulation of catechol-O-methyl transferase activity in women with uterine leiomyomas

Catechol-O-methyl transferase (COMT) expression is higher in leiomyomas compared with paired normal myometrium. The expression of COMT in leiomyoma cells is hormonally regulated-estrogen down-regulates, whereas P and dexamethasone up-regulate, COMT expression.