Up-regulation by IGF-I of proliferating cell nuclear antigen and Bcl-2 protein expression in human uterine leiomyoma cells

Current and Emerging Treatment Options for Uterine Fibroids

Uterine fibroids are the most common benign neoplasm of the female reproductive tract in reproductive age women. Their prevalence is age dependent and can be detected in up to 80% of women by the age of 50 years. Patients affected by uterine fibroids may experience a significant physical, emotional, social, and financial toll as well as losses in their quality of life. Unfortunately, curative hysterectomy abolishes future pregnancy potential, while uterine-sparing surgical and radiologic alternatives are variously associated with reduced long-term reproductive function and/or high tumor recurrence rates. Recently, pharmacological treatment against uterine fibroids have been widely considered by patients to limit uterine fibroid-associated symptoms such as heavy menstrual bleeding. This hormonal therapy seemed effective through blocking the stimulatory effects of gonadal steroid hormones on uterine fibroid growth. However, they are contraindicated in women actively pursuing pregnancy and otherwise effective only during use, which is limited because of long-term safety and other concerns. Accordingly, there is an urgent unmet need for safe, durable, and fertility-compatible non-surgical treatment options for uterine fibroids. In this review article, we cover the current pharmacological treatments for uterine fibroids including their comparable efficacy and side effects as well as emerging safe natural compounds with promising anti-uterine fibroid effects.

Androgen Signaling in Uterine Diseases: New Insights and New Targets

Common uterine diseases include endometriosis, uterine fibroids, endometrial polyps, endometrial hyperplasia, endometrial cancer, and endometrial dysfunction causing infertility. Patients with uterine diseases often suffer from abdominal pain, menorrhagia, infertility and other symptoms, which seriously impair their health and disturb their lives. Androgens play important roles in the normal physiological functions of the uterus and pathological progress of uterine diseases. Androgens in women are synthesized in the ovaries and adrenal glands. The action of androgens in the uterus is mainly mediated by its ligand androgen receptor (AR) that regulates transcription of the target genes. However, much less is known about the signaling pathways through which androgen functions in uterine diseases, and contradictory findings have been reported. This review summarizes and discusses the progress of research on androgens and the involvement of AR in uterine diseases. Future studies should focus on developing new therapeutic strategies that precisely target specific AR and their related signaling pathways in uterine diseases.

Wnt/β-catenin signaling pathway in uterine leiomyoma: role in tumor biology and targeting opportunities

Uterine leiomyoma is the most common tumor of the female reproductive system and originates from a single transformed myometrial smooth muscle cell. Despite the immense medical, psychosocial, and financial impact, the exact underlying mechanisms of leiomyoma pathobiology are poorly understood. Alterations of signaling pathways are thought to be instrumental in leiomyoma biology. Wnt/β-catenin pathway appears to be involved in several aspects of the genesis of leiomyomas. For example, Wnt5b is overexpressed in leiomyoma, and the Wnt/β-catenin pathway appears to mediate the role of MED12 mutations, the most common mutations in leiomyoma, in tumorigenesis. Moreover, Wnt/β-catenin pathway plays a paracrine role where estrogen/progesterone treatment of mature myometrial or leiomyoma cells leads to increased expression of Wnt11 and Wnt16, which induces proliferation of leiomyoma stem cells and tumor growth. Constitutive activation of β-catenin leads to myometrial hyperplasia and leiomyoma-like lesions in animal models. Wnt/β-catenin signaling is also closely involved in mechanotransduction and extracellular matrix regulation and relevant alterations in leiomyoma, and crosstalk is noted between Wnt/β-catenin signaling and other pathways known to regulate leiomyoma development and growth such as estrogen, progesterone, TGFβ, PI3K/Akt/mTOR, Ras/Raf/MEK/ERK, IGF, Hippo, and Notch signaling. Finally, evidence suggests that inhibition of the canonical Wnt pathway using β-catenin inhibitors inhibits leiomyoma cell proliferation. Understanding the molecular mechanisms of leiomyoma development is essential for effective treatment. The specific Wnt/β-catenin pathway molecules discussed in this review constitute compelling candidates for therapeutic targeting.

Differences in gynecologic tumor development in Amhr2-Cre mice with KRASG12D or KRASG12V mutations

How different KRAS variants impact tumor initiation and progression in vivo has not been thoroughly examined. We hypothesize that the ability of either KRAS^G12D or KRAS^G12V mutations to initiate tumor formation is context dependent. Amhr2-Cre mice express Cre recombinase in tissues that develop into the fallopian tubes, uterus, and ovaries. We used these mice to conditionally express either the KRAS^G12V/+or KRAS^G12D/+ mutation. Mice with the genotype Amhr2-Cre Pten^(fl/fl) Kras^G12D/+(G12D mice) had abnormal follicle structures and developed low-grade serous ovarian carcinomas with 100% penetrance within 18 weeks. In contrast, mice with the genotype Amhr2-Cre Pten^(fl/fl) Kras^G12V/+ (G12V mice) had normal follicle structures, and about 90% of them developed uterine tumors with diverse histological features resembling those of leiomyoma and leiomyosarcoma. Granulosa cell tumors also developed in G12V mice. Differences in cell-signaling pathways in the uterine tissues of G12D and G12V mice were identified using RNA sequencing and reverse-phase protein array analyses. We found that CTNNB1, IL1A, IL1B, TNF, TGFB1, APP, and IL6 had the higher activity in G12V mice than in G12D mice. These mouse models will be useful for studying the differences in signaling pathways driven by Kras^G12V/+ or Kras^G12D/+ mutations to aid development of targeted therapies for specific KRAS mutant variants. Our leiomyoma model driven by the Kras^G12V/+ mutation will also be useful in deciphering the malignant progression from leiomyoma to leiomyosarcoma.

Human Chorionic Gonadotrophin as a Possible Mediator of Leiomyoma Growth during Pregnancy: Molecular Mechanisms

Uterine fibroids are the most common gynecologic benign tumors. Studies supporting a strong pregnancy-related growth of leiomyomas generally claimed a crucial role of sex steroid hormones. However, sex steroids are unlikely the unique actors involved as estrogen and progesterone achieve a pick serum concentration in the last trimester while leiomyomas show a typical increase during the first trimester. Given the rapid exponential raise in serum human Chorionic Gonadotrophin (hCG) at the beginning of gestation, we conducted a review to assess the potential role of hCG in the striking growth of leiomyomas during initial pregnancy. Fibroid growth during initial pregnancy seems to correlate to the similar increase of serum hCG levels until 12 weeks of gestation. The presence of functional Luteinizing Hormone/human Chorionic Gonadotropin (LH/hCG) receptors was demonstrated on leiomyomas. In vitro treatment of leiomyoma cells with hCG determines an up to 500% increase in cell number after three days. Expression of cyclin E and cyclin-dependent kinase 1 was significantly increased in leiomyoma cells by hCG treatment. Moreover, upon binding to the receptor, hCG stimulates prolactin secretion in leiomyoma cells, promoting cell proliferation via the mitogen-activated protein kinase cascade. Fibroid enlargement during initial pregnancy may be regulated by serum hCG.

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.

Growth factors and pathogenesis

Growth factors are relatively small and stable, secreted or membrane-bound polypeptide ligands, which play an important role in proliferation, differentiation, angiogenesis, survival, inflammation, and tissue repair, or fibrosis. They exert multiple effects through the activation of signal transduction pathways by binding to their receptors on the surface of target cells. A number of studies have demonstrated the central role of growth factors and their signaling pathways in the pathogenesis of uterine leiomyomas. Numerous differentially expressed growth factors have been identified in leiomyoma and myometrial cells. These growth factors can activate multiple signaling pathways (Smad 2/3, ERK 1/2, PI3K, and β-catenin) and regulate major cellular processes, including inflammation, proliferation, angiogenesis, and fibrosis which are linked to uterine leiomyoma development and growth. In this chapter, we discuss the role of growth factors and their signaling pathways in the pathogenesis of uterine leiomyomas.

In Vivo Evidence of the Androgen Receptor in Association With Myometrial Cell Proliferation and Apoptosis

BACKGROUND

The androgen receptor (AR) plays essential roles in female reproductive physiology. In vitro studies have shown that AR exerts 2 distinct but related functions in myometrial cells. The AR is required for myometrial cell cycling ligand independently, thereby controls myometrial cell proliferation. The AR also exerts antiapoptotic functions through myeloid cell leukemia 1 (MCL1) in both ligand-dependent and ligand-independent manners. However, these AR functions have not yet been confirmed in vivo. This study provides in vivo evidence that AR expression is associated with myometrial cell proliferation and apoptosis.

METHODS

Myometrial tissue was collected on day 6 of pregnancy from mice bearing an intact AR (AR+/+) or mice with AR heterozygous (AR-/+) or homozygous (AR-/-) functional knockout. Human uterine leiomyoma and paired myometrial tissue biopsies (n = 14 patients) were collected during hysterectomy. Immunohistochemistry was used to assess the protein expression of AR, MCL1, and Ki-67 index, as well as the functional associations of AR with MCL1 and Ki-67 index.

RESULTS

In AR-/- mice, MCL1 protein levels were reduced ∼50% in both circular and longitudinal myometrial cells when compared with that in AR+/+ and AR-/+ mice. By contrast, Ki-67 index remained unchanged. The AR protein expression and Ki-67 index in leiomyoma were ∼2- to 3-fold higher than that in normal myometrium. Although MCL1 expression was not coordinately increased in leiomyoma, strong positive correlations between AR and MCL1 expression were observed in leiomyoma but not in normal myometrium tissue.

CONCLUSION

These results suggest that AR is an important regulator of myometrial growth in vivo during pregnancy and in leiomyoma.

Changes in proliferating and apoptotic markers of leiomyoma following treatment with a selective progesterone receptor modulator or gonadotropin-releasing hormone agonist

OBJECTIVE

To evaluate changes in proliferating and apoptotic markers of myoma tissue from patients treated with a selective progesterone receptor modulator (SPRM) or GnRH agonist by measuring expression of PDGF-A mRNA, IGF-1 mRNA, bcl-2 mRNA, and PCNA and caspase-3 protein.

STUDY DESIGN

Between December 2013 and July 2014, women with symptomatic leiomyoma were divided into control (no treatment before surgery), SPRM (treatment with ulipristal acetate [SPRM] for 3 months before surgery), and GnRHa (treatment with leuprolide acetate [GnRH agonist] for 3 months before surgery) groups. Tissue specimens were collected from the myoma core and normal myometrium of all patients. The expression of mRNA and protein was assessed by quantitative real-time reverse transcriptase-polymerase chain reaction and Western blot.

RESULTS

A total of 38 patients were enrolled (control group, n=14; SPRM group, n=13; GnRHa group, n=11). PDGF-A mRNA expression was lower in both the myoma core and normal myometrium tissues of the SPRM compared with the control group, but there was no difference between the control and GnRHa group. There were also no group differences in bcl-2 mRNA or IGF-1 mRNA expression. Both PCNA and caspase-3 protein expression were higher in the leiomyoma tissue of the SPRM compared with the control group, but there was no difference between the control and GnRHa groups in the expression of either protein.

CONCLUSION

Both proliferation and apoptosis were increased in the leiomyoma of patients after SPRM treatment, but there was no change following GnRH agonist treatment, in vivo. However, PDGF-A mRNA was decreased after SPRM treatment, indicating a dual effect of progesterone on the regulation of growth factors. Furthermore, there was an increase in caspase-3 protein, but not bcl-2 mRNA, expression in the SPRM group suggesting that SPRM may exert its effects in pathways other than the bcl-2 apoptotic pathway.

Matrix production and remodeling as therapeutic targets for uterine leiomyoma

Uterine leiomyoma, commonly known as fibroids, is a benign neoplasm of smooth muscle in women. The incidence of clinically symptomatic fibroids in reproductive-age women is approximately 20 %, with nearly 80 % of black women suffering from this condition. Symptoms include severe pain and hemorrhage; fibroids are also a major cause of infertility or sub-fertility in women. Uterine leiomyoma consist of hyperplastic smooth muscle cells and an excess deposition of extracellular matrix, specifically collagen, fibronectin, and sulfated proteoglycans. Extracellular matrix components interact and signal through integrin-β1 on the surface of uterine leiomyoma smooth muscle cells, provide growth factor storage, and act as co-receptors for growth factor-receptor binding. ECM and growth factor signaling through integrin-β1 and growth factor receptors significantly increases cell proliferation and ECM deposition in uterine leiomyoma. Growth factors TGF-β, IGF, PDGF, FGF and EGF are all shown to promote uterine leiomyoma progression and signal through multiple pathways to increase the expression of genes encoding matrix or matrix-modifying proteins. Decreasing integrin expression, reducing growth factor action and inhibiting ECM action on uterine leiomyoma smooth muscle cells are important opportunities to treat uterine leiomyoma without use of the current surgical procedures. Both natural compounds and chemicals are shown to decrease fibrosis and uterine leiomyoma progression, but further analysis is needed to make inroads in treating this common women's health issue.

Inactivation of AKT induces cellular senescence in uterine leiomyoma

Uterine leiomyomas (fibroids) are a major public health problem. Current medical treatments with GnRH analogs do not provide long-term benefit. Thus, permanent shrinkage or inhibition of fibroid growth via medical means remains a challenge. The AKT pathway is a major growth and survival pathway for fibroids. We propose that AKT inhibition results in a transient regulation of specific mechanisms that ultimately drive cells into cellular senescence or cell death. In this study, we investigated specific mechanisms of AKT inhibition that resulted in senescence. We observed that administration of MK-2206, an allosteric AKT inhibitor, increased levels of reactive oxygen species, up-regulated the microRNA miR-182 and several senescence-associated genes (including p16, p53, p21, and β-galactosidase), and drove leiomyoma cells into stress-induced premature senescence (SIPS). Moreover, induction of SIPS was mediated by HMGA2, which colocalized to senescence-associated heterochromatin foci. This study provides a conceivable molecular mechanism of SIPS by AKT inhibition in fibroids.

Uterine fibroids: pathogenesis and interactions with endometrium and endomyometrial junction

Uterine leiomyomas (fibroids or myomas) are benign tumors of uterus and clinically apparent in a large part of reproductive aged women. Clinically, they present with a variety of symptoms: excessive menstrual bleeding, dysmenorrhoea and intermenstrual bleeding, chronic pelvic pain, and pressure symptoms such as a sensation of bloatedness, increased urinary frequency, and bowel disturbance. In addition, they may compromise reproductive functions, possibly contributing to subfertility, early pregnancy loss, and later pregnancy complications. Despite the prevalence of this condition, myoma research is underfunded compared to other nonmalignant diseases. To date, several pathogenetic factors such as genetics, microRNA, steroids, growth factors, cytokines, chemokines, and extracellular matrix components have been implicated in the development and growth of leiomyoma. This paper summarizes the available literature regarding the ultimate relative knowledge on pathogenesis of uterine fibroids and their interactions with endometrium and subendometrial myometrium.

The role of progesterone signaling in the pathogenesis of uterine leiomyoma

Uterine leiomyomas are benign tumors that originate from the myometrium. Evidence points to ovarian steroid hormones, in particular, progesterone as major promoters of leiomyoma development and growth. While progesterone action in leiomyomas involves the classical nuclear receptor effects on gene regulation, there is growing evidence that signaling pathways are directly activated by the progesterone receptor (PR) and that PR can interact with growth factor signaling systems to promote proliferation and survival of leiomyomas. Studies investigating the genomic and non-genomic actions of PR and its role in leiomyoma growth are summarized here. Studies testing various selective progesterone receptor modulators for the treatment of leiomyomas are also highlighted. An increased understanding of the mechanisms associated with progesterone-driven growth of leiomyomas is critical in order to develop more efficient and targeted therapies for this prevalent disease.

Growth factors and myometrium: biological effects in uterine fibroid and possible clinical implications

BACKGROUND

Growth factors are proteins secreted by a number of cell types that are capable of modulating cellular growth, proliferation and cellular differentiation. It is well accepted that uterine cellular events such as proliferation and differentiation are regulated by sex steroids and their actions in target tissues are mediated by local production of growth factors acting through paracrine and/or autocrine mechanisms. Myometrial mass is ultimately modified in pregnancy as well as in tumour conditions such as leiomyoma and leiomyosarcoma. Leiomyomas, also known as fibroids, are benign tumours of the uterus, considered to be one of the most frequent causes of infertility in reproductive years in women.

METHODS

For this review, we searched the database MEDLINE and Google Scholar for articles with content related to growth factors acting on myometrium; the findings are hereby reviewed and discussed.

RESULTS

Different growth factors such as epidermal growth factor (EGF), transforming growth factor-α (TGF-α), heparin-binding EGF (HB-EGF), acidic fibroblast growth factor (aFGF), basic fibroblast growth factor (bFGF), vascular endothelial growth factor (VEGF), insulin-like growth factor (IGF), platelet-derived growth factor (PDGF) and TGF-β perform actions in myometrium and in leiomyomas. In addition to these growth factors, activin and myostatin have been recently identified in myometrium and leiomyoma.

CONCLUSIONS

Growth factors play an important role in the mechanisms involved in myometrial patho-physiology.

Lessons learned from the preclinical drug discovery of asoprisnil and ulipristal for non-surgical treatment of uterine leiomyomas

INTRODUCTION

Uterine leiomyoma is the most common benign tumor in women during the reproductive years. Menorrhagia is the common symptom and accounts for the most frequent indication for hysterectomy. Thus, development of a novel drug for non-surgical treatment of uterine leiomyoma is needed for the betterment of women's health.

AREA COVERED

This review introduces a translational research initiated by use of the levonorgestrel-releasing intrauterine system (LNG-IUS) for contraceptive purposes. During follow-up, a patient informed that heavy menstrual bleeding caused by uterine myoma was strikingly reduced after the insertion of device. The patient's unexpected comment led the authors to perform clinical trials of LNG-IUS for the management of menorrhagia in women with uterine myomas and striking reduction in menorrhagia was obtained by the use of LNG-IUS. MRI examination, however, revealed that the volume of myomas decreased in some, but increased in the other instances. This unexpected finding with MRI directed the authors to characterize the effects of progesterone (P4) and progesterone receptor modulators (PRMs) on uterineleiomyoma cell growth in vitro.

EXPERT OPINION

In consistence with the in vitro data obtained, randomized controlled clinical trials of PRMs in patients with uterine leiomyomas at several institutions have demonstrated that oral administration of PRMs (asoprisnil and ulipristal) for 3 months reduced leiomyoma volume, resulting in a significant improvement of the associated symptoms. However, a novel pattern of PRM-associated endometrial changes was recognized in the endometrial pathology, demonstrating unusual epithelial types not seen in the normal menstrual cycle of a premenstrual woman. Thus, follow-up studies to determine whether the novel endometrial changes remain, disappear or progress to something else are needed for the possible long-term use of PRMs for the treatment of uterine leiomyoma.

Risks and benefits of dietary isoflavones for cancer

A high intake of fruits and vegetables is associated with a lower risk of cancer. In this context, considerable attention is paid to Asian populations who consume high amounts of soy and soy-derived isoflavones, and have a lower risk for several cancer types such as breast and prostate cancers than populations in Western countries. Hence, interest focuses on soyfoods, soy products, and soy ingredients such as isoflavones with regard to their possible beneficial effects that were observed in numerous experiments and studies. The outcomes of the studies are not always conclusive, are often contradictory depending on the experimental conditions, and are, therefore, difficult to interpret. Isoflavone research revealed not only beneficial but also adverse effects, for instance, on the reproductive system. This is also the case with tumor-promoting effects on, for example, breast tissue. Isoflavone extracts and supplements are often used for the treatment of menopausal symptoms and for the prevention of age-associated conditions such as cardiovascular diseases and osteoporosis in postmenopausal women. In relation to this, questions about the effectiveness and safety of isoflavones have to be clarified. Moreover, there are concerns about the maternal consumption of isoflavones due to the development of leukemia in infants. In contrast, men may benefit from the intake of isoflavones with regard to reducing the risk of prostate cancer. Therefore, this review examines the risks but also the benefits of isoflavones with regard to various kinds of cancer, which can be derived from animal and human studies as well as from in vitro experiments.

C terminus of Clostridium perfringens enterotoxin downregulates CLDN4 and sensitizes ovarian cancer cells to Taxol and Carboplatin

PURPOSE

We have previously shown that CLDN4 (encoding claudin-4), a cell tight junction (TJ) protein, is highly expressed in human epithelial ovarian carcinomas (EOC) but undetectable in normal ovaries. CLDN4 has been identified as a specific receptor for C terminus of Clostridium perfringens enterotoxin (C-CPE), a nontoxic molecule that may disrupt TJ barrier function and enhance cellular absorption. The purpose of this study was to determine the potential clinical applications of C-CPE and its effects on CLDN4 expression in EOC.

EXPERIMENTAL DESIGN

Using a 3-dimensional culture model and monolayer culture of EOC cells, we examined the effects of C-CPE on CLDN4 expression by quantitative real-time PCR, immunofluorescence, and Western blot. The synergistic effect of C-CPE to clinically relevant chemotherapies (Taxol and Carboplatin) was observed in EOC culture and xenograft mice. Furthermore, we determined through oligonucleotide microarray analysis that the transcript profile alterations dysregulated as a consequence of C-CPE treatment.

RESULTS

C-CPE treatment decreased protein expression and relocated CLDN4 from cell-cell contact regions to the cytoplasm. Particularly, C-CPE sensitized EOC cells to chemotherapeutic administration at low dosages and significantly inhibited tumor growth in a nontoxic manner. Furthermore, we provided genome-wide molecular evidence that C-CPE treatment is involved in the stimulation of the ubiquitin-proteasome pathway and the inhibition of cell metabolism in EOC cells.

CONCLUSIONS

The addition of C-CPE can enhance the effectiveness of Taxol or Carboplatin and significantly inhibited EOC cell growth in a CLDN4-dependent manner, suggesting that C-CPE may have promising therapeutic potential for EOC.

Translational research with progesterone receptor modulator motivated by the use of levonorgestrel-releasing intrauterine system

The use of levonorgestrel-releasing intrauterine system (LNG-IUS) is effective for management of menorrhagic women with uterine myomas because of reduction in menorrhagia. However, the size of myomas during use of LNG-IUS increased in some but decreased in other instances. This prompted us to characterize the effects of progesterone (P4) on cultured leiomyoma cell growth. Treatment with P4 resulted in increase in epidermal growth factor (EGF) expression in cultured leiomyoma cells, whereas treatment with E2 augmented EGF-R expression in those cells. This indicates that P4 and E2 act in combination to stimulate myoma growth through induction of EGF/EGF-R expression. Bcl-2 expression in leiomyoma cells was up-regulated by P4. Furthermore, P4 augmented proliferating cell nuclear antigen expression in cultured leiomyoma cells but not in cultured normal myometrial cells. This fact let us to examine the effects of progesterone receptor modulator (PRM) on leiomyoma cell proliferation and apoptosis in comparison with normal myometrial cells. Our studies revealed that CDB-2914 inhibits the proliferation, stimulates apoptosis of cultured leiomyoma cells, and inhibits the expression of angiogenic factors (vascular endothelial growth factor and adrenomedullin) and their receptors in cultured leiomyoma cells, without affecting those in cultured normal myometrial cells. We then evaluated the effects of CDB-2914 on extracellular matrix (ECM) components in cultured leiomyoma cells. CDB-2914 increased ECM metalloproteinase inducer, matrix metalloproteinase (MMP)-1, MMP-8 contents and decreased tissue inhibitors of MMP (TIMP)-1, TIMP-2 contents as well as type I and type III collagen contents in cultured leiomyoma cells, without comparable effects on cultured normal myometrial cells. These findings demonstrate that PRM not only inhibits the proliferation and stimulates apoptosis of cultured leiomyoma cells but also suppresses collagen synthesis in a cell-type specific manner. This is meaningful for understanding the molecular mechanism of the usefulness of PRM in the treatment of uterine fibroids.

Expression of insulin-like growth factors (IGFs) and IGF signaling: molecular complexity in uterine leiomyomas

OBJECTIVE

To study whether dysregulation of insulin-like growth factors (IGFs) and IGF signaling are common molecular changes in symptomatic leiomyomas (fibroids) and whether IGFs are associated with large fibroids.

DESIGN

Examination of IGFs and IGF pathway genes in a large cohort of fibroids at transcriptional and translational levels. Mechanisms leading to alterations of IGFs and related genes were also analyzed.

SETTING

University clinical research laboratory.

PATIENT(S)

Hysterectomies for symptomatic fibroids were collected: 180 cases from paraffin-embedded tissues and 50 cases from fresh-frozen tissues.

INTERVENTION(S)

Tissue microarray and immunohistochemistry, DNA methylation analysis, reverse-transcriptase polymerase chain reaction, and Western blot.

MAIN OUTCOME MEASUREMENT(S)

Transcription and translation analyses of IGF-1/2, p-AKT, p-S6K, and TSC1/2 in fibroids and matched myometrium.

RESULT(S)

Insulin-like growth factors and downstream effectors were dysregulated in approximately one third of fibroids. All except for IGF-2 seemed to be abnormally regulated at translation levels. Up-regulation of IGF-2 messenger RNAs was contributed by all four alternating slicing promoters. There was a positive correlation of IGF-1 and p-AKT over-expression with fibroid size. Insulin-like growth factor 1 but not IGF-2 levels directly correlated with activation of p-AKT and p-S6K.

CONCLUSION(S)

Altered expressions of IGFs and their related downstream proteins were found in one third of fibroids. Large fibroids show high levels of IGF-1 and p-AKT activity compared with small ones.

Expression of insulin-like growth factor-1 and proliferating cell nuclear antigen in human pulp cells of teeth with complete and incomplete root development

AIM

To quantify the expression of insulin-like growth factor-1 (IGF-1) and proliferating cell nuclear antigen (PCNA) in human pulp cells of teeth with complete or incomplete root development, to support the specific role of IGF-1 in cell proliferation during tooth development and pulp reparative processes.

METHODOLOGY

Twenty six pulp samples were obtained from freshly extracted human third molars, equally divided in two groups according to root development stage (complete or incomplete root development). All samples were processed and immunostained to determine the expression of IGF-1 and PCNA in pulp cells. Sections were observed with a light microscope at 80x and morphometric analyses were performed to calculate the area of PCNA and IGF-1 immunostaining using digital image software. Mann-Whitney's test was used to determine statistically significant differences between groups (P < 0.05) for each peptide and the co-expression of both.

RESULTS

Expression of IGF-1 and PCNA was observed in all human pulp samples with a statistically significant higher expression in cells of pulps having complete root development (P = 0.0009).

CONCLUSION

Insulin-like growth factor-1 and PCNA are expressed in human pulp cells, with a significant greater expression in pulp cells of teeth having complete root development.

Human uterine smooth muscle and leiomyoma cells differ in their rapid 17beta-estradiol signaling: implications for proliferation

Uterine leiomyomas, benign uterine smooth muscle tumors that affect 30% of reproductive-aged women, are a significant health concern. The initiation event for these tumors is unclear, but 17beta-estradiol (E2) is an established promoter of leiomyoma growth. E2 not only alters transcription of E2-regulated genes but also can rapidly activate signaling pathways. The aim of our study is to investigate the role of rapid E2-activated cytoplasmic signaling events in the promotion of leiomyomas. Western blot analysis revealed that E2 rapidly increases levels of phosphorylated protein kinase C alpha (PKC alpha) in both immortalized uterine smooth muscle (UtSM) and leiomyoma (UtLM) cell lines, but increases levels of phosphorylated ERK1/2 only in UtLM cells. Our studies demonstrate a paradoxical effect of molecular and pharmacological inhibition of PKC alpha on ERK1/2 activation and cellular proliferation in UtLM and UtSM cells. PKC alpha inhibition decreases levels of phosphorylated ERK1/2 and proliferation in UtLM cells but raises these levels in UtSM cells. cAMP-PKA signaling is rapidly activated only in UtSM cells with E2 and inhibits ERK1/2 activation and proliferation. We therefore propose a model whereby E2's rapid activation of PKC alpha and cAMP-PKA signaling plays a central role in the maintenance of a low proliferative index in normal uterine smooth muscle via its inhibition of the MAPK cascade and these pathways are altered in leiomyomas to promote MAPK activation and proliferation. These studies demonstrate that rapid E2-signaling pathways contribute to the promotion of leiomyomas.

A low concentration of genistein induces estrogen receptor-alpha and insulin-like growth factor-I receptor interactions and proliferation in uterine leiomyoma cells

BACKGROUND

Previously, we found that genistein at low concentrations stimulates the growth of human uterine leiomyoma (LM) cells, but not uterine smooth muscle (myometrial) cells (SMC). The aim of this study was to understand the molecular mechanism whereby genistein causes hyperproliferation of LM cells.

METHODS

The effects of genistein at 1 microg/ml on LM cells and SMC were evaluated using estrogen response element gene reporter, real-time RT-PCR, western blot, immunoprecipitation and cell proliferation assays.

RESULTS

Elevated estrogen receptor (ER) transactivation, increased mRNA expression of early estrogen-responsive genes, progesterone receptor and insulin-like growth factor-I (IGF-I), and decreased protein levels of ER-alpha (ER alpha) were found in genistein-treated LM cells, but not SMC. Additionally, extracellular regulated kinase (ERK), Src homology/collagen (Shc) and ER alpha were transiently activated, and interactions between ER alpha and IGF-I receptor (IGF-IR) were rapidly induced by genistein in LM cells. Using ER antagonist ICI 182,780 and MAPK/ERK kinase (MEK) inhibitor PD98059, we found that these early events were inhibited and the proliferative effect of genistein on LM cells was abrogated.

CONCLUSIONS

ER alpha is involved in the transient activation of ERK/mitogen activated protein kinase (MAPK) by genistein via its early association with IGF-IR, leading to hyper-responsiveness of LM cells and confirming that ER signaling is enhanced by activation of ERK/MAPK in LM cells.

Comparative effects of SPRM asoprisnil (J867) on proliferation, apoptosis, and the expression of growth factors in cultured uterine leiomyoma cells and normal myometrial cells

Progesterone plays a pivotal role in controlling uterine leiomyoma growth. The authors review studies they conducted to evaluate the comparative effects of asoprisnil on proliferation, apoptosis, and growth factor expression in cultured leiomyoma and normal myometrial cells. Treatment with asoprisnil decreased the proliferating cell nuclear antigen-positive rate and the number of viable cells and increased the terminal deoxynucleotidyl transferase-mediated 2'-deoxyuridine 5'-triphosphate nick end labeling- positive rate in cultured leiomyoma cells in a dose-dependent manner ( P < .05). Similarly, asoprisnil decreased Bcl-2 expression and increased cleaved caspase-3 and cleaved poly(adenosine 5'-diphosphate-ribose) polymerase in leiomyoma cells but not in normal myometrial cells. Similarly, asoprisnil decreased epidermal growth factor (EGF), insulin-like growth factor-I (IGF-I), and transforming growth factor (TGF) beta mRNA and protein expression, as well as EGF receptor, IGF-IR alpha, and TGF RII protein expression in leiomyoma cells but not in cultured normal myometrial cells. These results suggest that asoprisnil selectively inhibits proliferation by downregulating the growth factors and their receptor expression and induces apoptosis in leiomyoma cells without affecting proliferation and apoptosis in normal myometrial cells.

Effects of levonorgestrel-releasing IUS and progesterone receptor modulator PRM CDB-2914 on uterine leiomyomas

We have found that the use of levonorgestrel-releasing IUS results in a remarkable decrease in endometrial proliferation and a remarkable increase in apoptosis in the endometrium; therefore, it is effective for long-term management of menorrhagic women with uterine myomas because of the striking reduction in menorrhagia. This prompted us to characterize the effects of progesterone (P(4)) and progesterone receptor modulator (PRM) CDB2914 on uterine myoma growth. In vitro studies with cultured uterine leiomyoma cells and normal myometrial cells revealed that P(4) stimulated the proliferative activity in leiomyoma cells, but not in normal myometrial cells. P(4) increased EGF expression, whereas E(2) augmented EGF-R expression in leiomyoma cells, indicating that P(4) and E(2) act in combination to stimulate leiomyoma cell growth. P(4) also increased Bcl-2 expression and decreased TNF-alpha expression in those cells. Unlike the EGF expression, IGF-I expression in leiomyoma cells was inhibited by P(4). These results suggest that P(4) has dual actions on leiomyoma growth: one is to stimulate the growth through up-regulating EGF and Bcl-2 expression, and the other is to inhibit the growth through down-regulating IGF-I expression in the cells. By contrast, CDB2914 inhibited proliferation and stimulated apoptosis of leiomyoma cells without affecting normal myometrial cells. Furthermore, CDB2914 inhibited vascular endothelial growth factor and adrenomedullin expression in leiomyoma cells, but not in normal myometrial cells. The cell type-specific action of CDB2914 on leiomyoma cells, without affecting the surrounding normal myometrial cells, is meaningful for understanding the usefulness of CDB2914 in the medical treatment of uterine myomas.

A novel selective progesterone receptor modulator asoprisnil (J867) down-regulates the expression of EGF, IGF-I, TGFβ3 and their receptors in cultured uterine leiomyoma cells

BACKGROUND

This study was conducted to evaluate the effects of a novel selective progesterone receptor modulator (SPRM) asoprisnil on the expression of growth factors and their receptors and on growth factor-induced proliferation of cultured uterine leiomyoma and matching myometrial cells.

METHODS

The expression of epidermal growth factor (EGF), insulin-like growth factor-I (IGF-I) and transforming growth factor (TGFbeta3) was assessed by immunocytochemistry and semi-quantitative RT-PCR. The expression of phosphorylated EGF receptor (p-EGFR), IGF-I receptor alpha subunit (IGF-IRalpha) and phosphorylated TGFbeta receptor type II (p-TGFbeta RII) was assessed by Western blot analysis. Cell proliferation was assessed by 3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium assay.

RESULTS

Treatment with 10(-7) M asoprisnil decreased EGF, IGF-I and TGFbeta3 mRNA and protein expression as well as p-EGFR, IGF-IRalpha and p-TGFbeta RII protein expression in leiomyoma cells cultured for 72 h. EGF (100 ng/ml), IGF-I (100 ng/ml) and TGFbeta3 (10 ng/ml) increased the number of viable leiomyoma cells cultured for 72 h, whereas the concomitant treatment with 10(-7) M asoprisnil antagonized the growth factor-induced increase in leiomyoma cell proliferation. In cultured myometrial cells, however, asoprisnil affected neither the growth factor and their receptor expression nor the cell proliferation.

CONCLUSION

Asoprisnil inhibits the expression of EGF, IGF-I, TGFbeta3 and their receptors in cultured leiomyoma cells without affecting their expressions in myometrial cells.

Expression profile of the tumorigenic factors associated with tumor size and sex steroid hormone status in uterine leiomyomata

OBJECTIVE

To use tissue microarray in combination with dendrogram cluster analysis to characterize some potential tumorigenic factors in association with tumor size and sex steroid hormone status in uterine leiomyomata.

DESIGN

Expression analysis of 21 selected potential tumorigenic factors in 60 patients with uterine leiomyomata.

SETTING

University clinical research laboratory.

PATIENT(S)

Hysterectomy specimens from 60 patients with uterine leiomyomata of different ages and tumor sizes.

INTERVENTION(S)

Tissue cores from normal myometrium and leiomyomata were examined by immunohistochemistry.

MAIN OUTCOME MEASURE(S)

Semiquantitative immunointensity was scored and analyzed by net gain and loss between normal myometrium and leiomyomata and integrated into dendrogram cluster tree view.

RESULT(S)

We found that upregulation of estrogen and progesterone receptors was reverse associated with tumor size. Upregulation of some factors (HMGA2, sex steroid receptor cofactors, proteins in insulin pathway, and CD24) were identified in a group of patients in their later forties, were associated with large fibroids, and were weakly affected by the SSH status (illustrated by endometrial phases and menopause). Downregulation of tuberin and glucocorticoid receptor was mostly isolated in a second group of women at their late reproductive age.

CONCLUSION(S)

Analyses of the sex steroid hormone receptors and the nonsex steroid hormone factors in leiomyomata and the matched myometrium showed different expression patterns in different tumor sizes and patients' ages. A group of patients in their late forties with the larger leiomyomata contributes largely by upregulation of nonsex steroid hormone factors. Adenomyosis is a protective factor preventing large leiomyomata.

Antiproliferative and proapoptotic effects of raloxifene on uterine leiomyomas in postmenopausal women

OBJECTIVE

To study the cell effects of raloxifene on uterine and leiomyoma tissue in postmenopausal women.

DESIGN

Prospective, randomized, double-blind, placebo-controlled study.

SETTING

Department of Obstetrics and Gynecology, University "Magna Graecia" of Catanzaro, Italy.

PATIENT(S)

Forty postmenopausal women affected by uterine leiomyomas and selected for hysterectomy.

INTERVENTION(S)

Treatment for three cycles of 28 days with raloxifene at a dose of 180 mg/day orally (raloxifene group) or placebo tablets (3 tablets/day orally) (placebo group).

MAIN OUTCOME MEASURE(S)

Uterine and leiomyoma dimensions were measured in each subject at entry and before surgery. On leiomyomas and homologous myometrium the proliferating cell nuclear antigen (PCNA)-positive cells/total cells (PCNA/TC) and the Bcl-2-positive cells/Bax-positive cells (Bcl-2/Bax) ratios (%), as proliferation and apoptotic indexes, respectively, were measured.

RESULT(S)

After treatment, uterine and leiomyoma sizes were significantly changed in comparison with baseline and the placebo group. PCNA/TC and Bcl-2/Bax ratios were significantly higher in leiomyomas than in homologous myometrium. A significant difference was detected in PCNA/TC between the myometrium of the raloxifene and control groups, whereas no difference was observed in the Bcl-2/Bax ratio. A significant difference in PCNA/TC and Bcl-2/Bax ratios was detected in leiomyoma tissue between the raloxifene group and controls.

CONCLUSION(S)

In postmenopausal women, raloxifene administration reduces uterine leiomyomas by exerting a cell antiproliferative and proapoptotic action.

Growth dynamics of human leiomyoma cells and inhibitory effects of the peroxisome proliferator-activated receptor-γ ligand, pioglitazone

Uterine leiomyomas (fibroids) are the most frequent tumour of the female reproductive tract and are the primary cause of hysterectomies in women worldwide. Effective treatment options are few. In a search for alternative treatments, we have established primary cultures of human leiomyoma cells and adjacent myometrial tissues, and documented their growth dynamics in response to estradiol (E2) and pioglitazone (PIO), a peroxisome proliferation-activated receptor-gamma (PPARgamma) ligand, currently in clinical use for type II diabetes mellitus. Human uterine primary cell cultures display morphology and desmin content consistent with their smooth muscle origin. Surprisingly, leiomyoma cells exhibited slower proliferation patterns relative to matched myometrial cells, both in the absence and presence of E2, suggesting that tumour genesis may not be because of increased growth potential but could be related to suppression of growth-inhibiting factors in vivo. PIO significantly inhibited the cell proliferation of both myometrial and leiomyoma cells in a dose-dependent manner. Our results suggest the possibility of using PPARgamma ligands, such as PIO, as therapeutic agents for the conservative management of uterine fibroids.

Expression profile of tuberin and some potential tumorigenic factors in 60 patients with uterine leiomyomata

Human uterine leiomyomata are the most common tumors in women of reproductive age. The pathogenesis of leiomyomata remains unknown. An animal model of Eker rats with deleted tuberous sclerosis complex gene 2 (tuberin) shows increased incidence of leiomyomata. The role of tuberin in human leiomyomata is unknown. In this study, we designed a tissue microarray with tissue cores of leiomyomata and the matched myometrium from 60 hysterectomy specimens. We examined the expression of tuberin and tuberous sclerosis complex gene 1 product hamartin, proteins of the insulin-signaling pathway, steroid receptors and some of their cofactors, and human mobility group gene A2 by immunohistochemistry. We found that nearly half of the cases displayed either reduction or loss of tuberin in leiomyomata compared with matched normal myometrium. No change of hamartin was noted. Furthermore, a significant reduction of glucocorticoid receptor was found in leiomyomata with reduced tuberin. The proteins insulin like growth factor 1, insulin-like growth factor receptor beta, AKT kinase, and phosphatidylinositol 3-kinase were upregulated. Nearly half of leiomyomata show upregulation of human mobility group gene A2, along with the steroid receptor cofactors. Our findings suggest that there are two broad groups of uterine leiomyomata. One group is associated with an alteration of tuberin and glucocorticoid receptor. The other group is associated with upregulation of human mobility group gene A2 and steroid receptor cofactors.

Effects of progesterone on growth factor expression in human uterine leiomyoma

It is now evident that the use of levonorgestrel-releasing intrauterine system (LNg-IUS) is effective for long-term management of menorrhagic women with uterine myomas because of a striking reduction in menorrhagia. This prompted us to characterize the effects of progesterone (P4) on the growth and apoptosis of uterine leiomyoma cells. On the other hand, we have recently noted that epidermal growth factor (EGF) and IGF-I play a crucial role in prompting uterine leiomyoma growth through stimulating the proliferative potential and inhibiting apoptosis of cultured human leiomyoma cells. In the present review, attention was paid to evaluate the effects of P4 on the expression of growth factors (EGF, IGF-I) and apoptosis-related factors (TNFalpha, Bcl-2 protein) in cultured uterine leiomyoma cells. Treatment with P4 augmented EGF and Bcl-2 protein expression, but inhibited IGF-I and TNFalpha expression in cultured leiomyoma cells. It is known that TNFalpha induces apoptosis in a variety of cell types and Bcl-2 protein is an apoptosis-inhibiting gene product. Thus, the results obtained suggest that P4 has dual actions on uterine leiomyoma growth: one is to stimulate leiomyoma cell growth and survival through up-regulating EGF and Bcl-2 protein expression as well as down-regulating TNFalpha expression in those cells, and the other is to inhibit leiomyoma cell growth through down-regulating IGF-I expression in those cells. This may explain why the size of uterine myomas during use of LNg-IUS increases in some but decreases in other instances. This may also explain why the size of uterine myomas during pregnancy does not increase despite the overwhelming increase in circulating concentrations of sex steroid hormones.