Aromatase inhibitors in gynecologic cancers

Roles of estrogen receptor α in endometrial carcinoma (Review)

Endometrial carcinoma (EC) is a group of endometrial epithelial malignancies, most of which are adenocarcinomas and occur in perimenopausal and postmenopausal women. It is one of the most common carcinomas of the female reproductive system. It has been shown that the occurrence and development of EC is closely associated with the interaction between estrogen (estradiol, E2) and estrogen receptors (ERs), particularly ERα. As a key nuclear transcription factor, ERα is a carcinogenic factor in EC. Its interactions with upstream and downstream effectors and co-regulators have important implications for the proliferation, metastasis, invasion and inhibition of apoptosis of EC. In the present review, the structure of ERα and the regulation of ERα in multiple dimensions are described. In addition, the classical E2/ERα signaling pathway and the crosstalk between ERα and other EC regulators are elucidated, as well as the therapeutic targeting of ERα, which may provide a new direction for clinical applications of ERα in the future.

Prognostic role of NF-YA splicing isoforms and Lamin A status in low grade endometrial cancer

Although most cases of low grade (G1) endometrial cancer (EC) do not behave aggressively, in rare instances, can progress in a highly aggressive manner. In this study we analyzed formalin-fixed, paraffin-embedded (FFPE) EC tissues to find novel clinical and biological features to help diagnosis and treatment of G1 ECs s in order to better stratify patient risk of recurrence. A retrospective cohort of FFPE specimens from patients with EC (n=87) and benign tissue specimens (NE) from patients who underwent a hysterectomy to treat other benign disease (n = 13) were collected. Total RNA and proteins were extracted and analyzed, respectively, by quantitative PCR and western blotting. NF-YAs is expressed and lamin A is down-modulated in all high grade (G2 and G3) ECs. In G1 ECs, NF-YAs expression is heterogeneous being expressed only in a subset of these tumours. Interestingly, the G1 ECs that express NF-YAs display low levels of lamin A similar to those present in G2 and G3 ECs. Of note, this pattern of NF-YAs and lamin A expression correlates with tumor aggressiveness assessed by comparative analysis with estrogen receptor (ER) status and epithelial-mesenchymal transition (EMT) markers thus suggesting its potential role as biomarker of tumour aggressiveness in G1 EC. In all grade ECs, lamin A is strongly downmodulated, being its expression inversely correlated with tumor aggressiveness and its loss of expression. We identified NF-YAs and lamin A expression levels as novel potential biomarkers useful to identify G1 ECs patients with risk of recurrence.

Dysregulation of Aromatase in Breast, Endometrial, and Ovarian Cancers: An Overview of Therapeutic Strategies

Aromatase is the rate-limiting enzyme in the biosynthesis of estrogens, which play crucial roles on a spectrum of developmental and physiological processes. The biological actions of estrogens are classically mediated by binding to two estrogen receptors (ERs), ERα and ERβ. Encoded by the cytochrome P450, family 19, subfamily A, polypeptide 1 (CYP19A1) gene, aromatase is expressed in a wide variety of tissues, as well as benign and malignant tumors, and is regulated in a pathway- and tissue-specific manner. Overexpression of aromatase, leading to elevated systemic levels of estrogen, is unequivocally linked to the pathogenesis and growth of a number malignancies, including breast, endometrium, and ovarian cancers. Aromatase inhibitors (AIs) are routinely used to treat estrogen-dependent breast cancers in postmenopausal women; however, their roles in endometrial and ovarian cancers remain obscure. While AI therapy is effective in hormone sensitive cancers, they diminish estrogen production throughout the body and, thus, generate undesirable side effects. Despite the effectiveness of AI therapy, resistance to endocrine therapy remains a major concern and is the leading cause of cancer death. Considerable advances, toward mitigating these issues, have evolved in conjunction with a number of histone deacetylase (HDAC) inhibitors for countering an assortment of diseases and cancers, including the aforesaid malignancies. HDACs are a family of enzymes that are frequently dysregulated in human tumors. This chapter will discuss the current understanding of aberrant regulation and expression of aromatase in breast, endometrial, and ovarian cancers, and potential therapeutic strategies for prevention and treatment of these life-threatening diseases.

The role of fulvestrant in endometrial cancer

INTRODUCTION

Endometrial cancer is the most common malignancy of the female genital tract in industrialized countries. The traditional treatment of endometrial cancer is based on a surgical approach. In recent years, systemic endocrine therapy has demonstrated good efficacy in recurrent or metastatic setting, delaying progression, ameliorating quality of life and palliating symptoms. Areas covered: Phase I and II studies on selective estrogen receptor down-regulators used for the treatment of endometrial cancer treatment have been reviewed. The pharmacokinetic and pharmacodynamic features of selective receptor down-regulators have been also investigated. Expert opinion: Selective estrogen receptor down-regulators may exhibit clinical efficacy in the treatment of gynecological malignancies due to their pure estrogen receptor antagonist properties. However, up to now data are still limited and some unsolved questions remain. Fulvestrant has poor oral bioavailability and low pharmacodynamic characteristics. Further trials are required to examine new selective estrogen receptor down-regulator agents with better pharmacodynamic and pharmacokinetic profiles.

Imiquimod Induces Apoptosis in Human Endometrial Cancer Cells In vitro and Prevents Tumor Progression In vivo

PURPOSE

The increasing incidence of endometrial cancer (EC), in younger age at diagnosis, calls for new tissue-sparing treatment options. This work aims to evaluate the potential of imiquimod (IQ) in the treatment of low-grade EC.

METHODS

Effects of IQ on the viabilities of Ishikawa and HEC-1A cells were evaluated using MTT assay. The ability of IQ to induce apoptosis was evaluated by testing changes in caspase 3/7 levels and expression of cleaved caspase-3, using luminescence assay and western blot. Apoptosis was confirmed by flow cytometry and the expression of cleaved PARP. Western blot was used to evaluate the effect of IQ on expression levels of Bcl-2, Bcl-xL, and BAX. Finally, the in vivo efficacy of IQ was tested in an EC mouse model.

RESULTS

There was a decrease in EC cell viability following IQ treatment as well as increased caspase 3/7 activities, cleaved caspase-3 expression, and Annexin-V/ 7AAD positive cell population. Western blot results showed the ability of IQ in cleaving PARP, decreasing Bcl-2 and Bcl-xL expressions, but not affecting BAX expression. In vivo study demonstrated IQ's ability to inhibit EC tumor growth and progression without significant toxicity.

CONCLUSIONS

IQ induces apoptosis in low-grade EC cells in vitro, probably through its direct effect on Bcl-2 family protein expression. In, vivo, IQ attenuates EC tumor growth and progression, without an obvious toxicity. Our study provides the first building block for the potential role of IQ in the non-surgical management of low-grades EC and encouraging further investigations.

Effectiveness of aromatase inhibitors in the treatment of advanced endometrial adenocarcinoma

PURPOSE

Type I endometrial cancer is a common tumor of the female genital tract. Since in post-menopausal women aromatase enzyme can stimulate the endometrial tissue neoplastic growth, the use of aromatase inhibitors may have a therapeutic effect, especially in patients not eligible for surgery.

METHODS

A systematic review has been performed, with a very specific scope, i.e., the use of aromatase inhibitors in the treatment of advanced or recurrent endometrial cancer, as a single agent or in combination with others drugs.

RESULTS

On the basis of the 117 records retrieved from the bibliographic search, the rationale for the use of aromatase inhibitors in endometrial cancer therapy is discussed. Six papers fall within the scope of our systematic review and their results are thoroughly analyzed. Moreover, we report our experience on the clinical effectiveness of anastrozole in the post-chemotherapy treatment of a patient affected by advanced-stage endometrial cancer.

CONCLUSION

In general, aromatase inhibitors seem to have limited clinical benefit in the treatment of advanced and recurrent endometrial cancer, although further clinical trials are necessary to investigate more in depth their role. In our case, we experienced a positive feedback in terms of control of an advanced-stage disease.

The role of reproductive hormones in epithelial ovarian carcinogenesis

Epithelial ovarian cancer comprises ∼85% of all ovarian cancer cases. Despite acceptance regarding the influence of reproductive hormones on ovarian cancer risk and considerable advances in the understanding of epithelial ovarian carcinogenesis on a molecular level, complete understanding of the biologic processes underlying malignant transformation of ovarian surface epithelium is lacking. Various hypotheses have been proposed over the past several decades to explain the etiology of the disease. The role of reproductive hormones in epithelial ovarian carcinogenesis remains a key topic of research. Primary questions in the field of ovarian cancer biology center on its developmental cell of origin, the positive and negative effects of each class of hormones on ovarian cancer initiation and progression, and the role of the immune system in the ovarian cancer microenvironment. The development of the female reproductive tract is dictated by the hormonal milieu during embryogenesis. Intensive research efforts have revealed that ovarian cancer is a heterogenous disease that may develop from multiple extra-ovarian tissues, including both Müllerian (fallopian tubes, endometrium) and non-Müllerian structures (gastrointestinal tissue), contributing to its heterogeneity and distinct histologic subtypes. The mechanism underlying ovarian localization, however, remains unclear. Here, we discuss the role of reproductive hormones in influencing the immune system and tipping the balance against or in favor of developing ovarian cancer. We comment on animal models that are critical for experimentally validating existing hypotheses in key areas of endocrine research and useful for preclinical drug development. Finally, we address emerging therapeutic trends directed against ovarian cancer.

HNRNP G and HTRA2-BETA1 regulate estrogen receptor alpha expression with potential impact on endometrial cancer

Background

Estrogen receptor alpha (ERa/ESR1) expression is regulated by alternative splicing. Its most frequently detectable exon7 skipping isoform (ERaD7) is a dominant negative variant. Elevated expression of ERaD7 was already detected in endometrial cancer (EC), while its potential prognostic significance has not been characterized so far. Exon7 contains potential binding sites for the two functional splicing regulatory opponents, HNRNPG and HTRA2-BETA1 known to trigger opposite effects on EC outcome.

This study served to elucidate the influence of HNRNPG and HTRA2-BETA1 on ERa exon7 splicing regulation and the impact of ERaD7 concentration on type 1 EC outcome.

Methods

Functional in vitro experiments for HNRNPG and HTRA2-BETA1 in regard to the regulatory impact on endogenous and exogenous ERaD7 splicing were performed. Additionally, real-time PCR determined mRNA levels of ERaD7, HNRNPG and HTRA2-BETA1 in 116 type 1 EC patients.

Results

HNRNPG and HTRA2-BETA1 were found to be specific regulators of ERa exon7 splicing. While HTRA2-BETA1 promoted exon7 inclusion, HNRNPG antagonized this effect by inducing exon7 skipping (p = 0.004). ERaD7 was detected in 71 out of 116 type 1 EC specimens. Statistical analyses revealed an inverse correlation between ERaD7 mRNA levels and tumor grading (p = 0.029), FIGO stage (p = 0.033) as well as lymph node metastases (p = 0.032), respectively. Furthermore, higher ERaD7 expression could be correlated to an improved disease-specific survival (p = 0.034).

Conclusions

Our study demonstrates antagonistic regulatory effects of HNRNPG and HTRA2-BETA1 on ERa exon7 splicing with potential impact on type 1 EC clinical outcome due to the consecutively variable expression levels of the ERa isoform D7.

Electronic supplementary material

The online version of this article (doi:10.1186/s12885-015-1088-1) contains supplementary material, which is available to authorized users.

Use of aromatase inhibitors as first- and second-line medical therapy in patients with endometrial adenocarcinoma: a retrospective study

OBJECTIVES

The primary objective of this study was to examine the role of aromatase inhibitors (AIs) as first- or second-line medical treatment in women with endometrial adenocarcinoma who were not candidates for surgical management. The secondary objective was to examine the role of AIs in adjuvant and palliative treatment.

METHODS

Thirty women with endometrial adenocarcinoma who were treated with aromatase inhibitors between 2000 and 2010 at the Tom Baker Cancer Centre in Calgary, Alberta were assessed in a retrospective analysis. Disease response was based on response evaluation criteria in solid tumours. Kruskal-Wallis test was used to compare non-parametric variables and Fisher exact test was used to compare the health variables.

RESULTS

Seventeen patients received AIs as first- or second-line medical treatment, five received adjuvant therapy, and eight received palliative treatment. The median age of patients in the first or second line medical treatment group was significantly greater than that of patients in the adjuvant or palliative group (P = 0.042). There was no significant difference in median weight or body mass index. The subjective clinical response rate with medical treatment was 70%. In the first- or second-line medical treatment group, only seven patients had available response data. Our study showed stable disease in 5/7 (71%), partial response in 1/7 (14%), and progression in 1/7 (14%) patients.

CONCLUSION

This retrospective clinical series examining use of an aromatase inhibitor as first- or second-line medical therapy in women with endometrial carcinoma showed that AIs are a potential treatment for patients who have a contraindication to surgery and who either have failed or cannot use megestrol therapy.

Hormone response in ovarian cancer: time to reconsider as a clinical target?

Ovarian cancer is the sixth most common cancer worldwide among women in developed countries and the most lethal of all gynecologic malignancies. There is a critical need for the introduction of targeted therapies to improve outcome. Epidemiological evidence suggests a critical role for steroid hormones in ovarian tumorigenesis. There is also increasing evidence from in vitro studies that estrogen, progestin, and androgen regulate proliferation and invasion of epithelial ovarian cancer cells. Limited clinical trials have shown modest response rates; however, they have consistently identified a small subset of patients that respond very well to endocrine therapy with few side effects. We propose that it is timely to perform additional well-designed trials that should include biomarkers of response.

Hormone response in ovarian cancer: time to reconsider as a clinical target?

Ovarian cancer is the sixth most common cancer worldwide among women in developed countries and the most lethal of all gynecologic malignancies. There is a critical need for the introduction of targeted therapies to improve outcome. Epidemiological evidence suggests a critical role for steroid hormones in ovarian tumorigenesis. There is also increasing evidence from in vitro studies that estrogen, progestin, and androgen regulate proliferation and invasion of epithelial ovarian cancer cells. Limited clinical trials have shown modest response rates; however, they have consistently identified a small subset of patients that respond very well to endocrine therapy with few side effects. We propose that it is timely to perform additional well-designed trials that should include biomarkers of response.

Hormonal therapy for recurrent low-grade serous carcinoma of the ovary or peritoneum

OBJECTIVE

To determine whether hormonal therapies have efficacy in patients with recurrent low-grade serous carcinoma of the ovary or peritoneum.

METHODS

We searched departmental databases for patients with histologically-confirmed, evaluable, recurrent low-grade serous ovarian or peritoneal carcinoma who received hormonal therapy at our institution between 1989 and 2009. We retrospectively reviewed patients' medical records for demographic, disease, hormonal therapy, and estrogen receptor and progesterone receptor expression data. We used the Response Evaluation Criteria in Solid Tumors version 1.1 to determine patients' responses to hormonal therapy. Because patients could have received more than one evaluable hormonal therapy regimen, we chose to define the outcome metric as "patient-regimens." Median time to disease progression (TTP) and overall survival (OS) were also calculated. Regression analysis was also performed.

RESULTS

We identified 64 patients with recurrent low-grade serous carcinoma of the ovary or peritoneum. Patients' median TTP and median OS were 7.4 and 78.2 months, respectively. Patients received 89 separate hormonal patient-regimens, which produced an overall response rate of 9% (6 complete responses and 2 partial responses). Sixty-one percent of the patient-regimens resulted in a progression-free survival duration of at least 6 months. Patient-regimens involving ER+/PR+ disease produced a longer median TTP (8.9 months) than patient-regimens involving ER+/PR- disease did (6.2 months; p=0.053). This difference approached but did not reach statistical significance.

CONCLUSIONS

Hormonal therapies have moderate anti-tumor activity in patients with recurrent low-grade serous carcinoma of the ovary or peritoneum. Further study to determine whether ER/PR expression status is a predictive biomarker for this rare cancer subtype is warranted.

Intracranial meningiomas in patients with uterine sarcoma treated with long-term megestrol acetate therapy

OBJECTIVE

To report a series of four patients with uterine sarcoma, including one with müllerian adenosarcoma (MA) and three with low-grade endometrial stromal sarcoma (LGESS), who developed intracranial meningiomas while receiving the progesterone agonist megestrol acetate.

METHODS

The hospital records, imaging studies, and pathology slides of four patients who were treated for uterine sarcomas and subsequently developed intracranial meningiomas were reviewed.

RESULTS

All patients underwent surgery for their gynecologic cancers and received maintenance therapy with long-term hormonal suppression with megestrol acetate. Each of the four patients later developed neurologic symptoms secondary to intracranial meningiomas. Three patients had more than one meningioma. Histopathologic examination of all excised tumors showed strong immunoreactivity for progesterone receptors (PRs).

CONCLUSIONS

Patients with uterine sarcoma subtypes LGESS and MA may be predisposed to develop meningiomas, particularly in the setting of long-term treatment with megestrol acetate. Alternatively, preexisting, clinically silent meningiomas in these patients may have progressed to the point of clinical symptoms in the presence of the progesterone agonist megestrol acetate. Without previous imaging studies showing the presence or absence of meningioma before initiation of megestrol acetate treatment, there is no way to draw definitive conclusions regarding this possibility. Clinical and neuroradiologic surveillance for meningiomas should be strongly considered in patients with these uterine sarcoma subtypes, particularly in patients undergoing long-term suppressive therapy with megestrol acetate.

Recurrent ovarian cancer: when and how to treat

Notwithstanding continuing efforts to improve the primary treatment for ovarian cancer, most patients will ultimately develop recurrent disease. The benefits of detection and early systemic treatment of recurrence are now in doubt following the presentation of the MRC/EORTC CA125 surveillance trial. The impact of secondary cytoreductive surgery on survival requires more investigation. The role of antiangiogenic and other biological agents such as PARP inhibitors is becoming increasingly important for patients as an addition or alternative to the more conventional cytotoxic therapies available. Uncertainties and choices abound both in the treatment of recurrent ovarian cancer and the timing of such interventions. This article not only explores how to treat these patients but also the controversial issue of when to treat. Educating and involving the patient in decisions about their treatment options is of paramount importance.

The microRNA-200 family is upregulated in endometrial carcinoma

Background

MicroRNAs (miRNAs, miRs) are small non-coding RNAs that negatively regulate gene expression at the post-transcriptional level. MicroRNAs are dysregulated in cancer and may play essential roles in tumorigenesis. Additionally, miRNAs have been shown to have prognostic and diagnostic value in certain types of cancer. The objective of this study was to identify dysregulated miRNAs in endometrioid endometrial adenocarcinoma (EEC) and the precursor lesion, complex atypical hyperplasia (CAH).

Methodology

We compared the expression profiles of 723 human miRNAs from 14 cases of EEC, 10 cases of CAH, and 10 normal proliferative endometria controls using Agilent Human miRNA arrays following RNA extraction from formalin-fixed paraffin-embedded (FFPE) tissues. The expression of 4 dysregulated miRNAs was validated using real time reverse transcription-PCR.

Results

Forty-three miRNAs were dysregulated in EEC and CAH compared to normal controls (p<0.05). The entire miR-200 family (miR-200a/b/c, miR-141, and miR-429) was up-regulated in cases of EEC.

Conclusions

This information contributes to the candidate miRNA expression profile that has been generated for EEC and shows that certain miRNAs are dysregulated in the precursor lesion, CAH. These miRNAs in particular may play important roles in tumorigenesis. Examination of miRNAs that are consistently dysregulated in various studies of EEC, like the miR-200 family, will aid in the understanding of the role that miRNAs play in tumorigenesis in this tumour type.

Endometrial/ioid Stromal Tumors and Related Neoplasms of the Female Genital Tract

Endometrial/ioid stromal tumors comprise a spectrum of mesenchymal neoplasms, ranging from benign to low-grade malignancy to undifferentiated sarcomas, which occur predominantly in the uterus but may rarely originate at extrauterine sites, most commonly in the ovary. These tumors and their morphologic variants are important to recognize as they often cause diagnostic difficulties. This review focuses on the diagnostic criteria and differential diagnosis, including the role of immunohistochemistry.

Hormone therapy for epithelial ovarian cancer

PURPOSE OF REVIEW

Hormonal therapy has been used erratically to treat epithelial ovarian cancer since the mid 1960s; however, there has been little progress until recently in our understanding of which patients might benefit from treatment. Some clarity in the field is now beginning to emerge from recent studies, which have started to define biomarkers within epithelial ovarian cancers that link with hormonal response and thereby indicate which cohort of patients might be amenable to hormonal treatment.

RECENT FINDINGS

Oestrogen-deprivation therapy in the form of the aromatase inhibitor letrozole has demonstrated activity in three clinical studies. As only a minority of patients will benefit from hormonal approaches, recent efforts have focussed on the use of molecular markers to help identify which subgroup of patients might respond to treatment. Parallel laboratory studies using primary cancer material for which endocrine response is known and model-based findings have identified components of oestrogen signalling pathways that may help predict outcome.

SUMMARY

Use of the antioestrogen letrozole in ovarian cancer has consistently demonstrated a significant level of activity and the larger clinical studies have linked response with oestrogen receptor alpha expression and other biomarkers.

Increased PADI4 expression in blood and tissues of patients with malignant tumors

Background

Peptidylarginine deiminase type 4 (PAD4/PADI4) post-translationally converts peptidylarginine to citrulline. Recent studies suggest that PADI4 represses expression of p53-regulated genes via citrullination of histones at gene promoters.

Methods

Expression of PADI4 was investigated in various tumors and non-tumor tissues (n = 1673) as well as in A549, SKOV3 and U937 tumor cell lines by immunohistochemistry, real-time PCR, and western blot. Levels of PADI4 and citrullinated antithrombin (cAT) were investigated in the blood of patients with various tumors by ELISA (n = 1121).

Results

Immunohistochemistry detected significant PADI4 expression in various malignancies including breast carcinomas, lung adenocarcinomas, hepatocellular carcinomas, esophageal squamous cancer cells, colorectal adenocarcinomas, renal cancer cells, ovarian adenocarcinomas, endometrial carcinomas, uterine adenocarcinomas, bladder carcinomas, chondromas, as well as other metastatic carcinomas. However, PADI4 expression was not observed in benign leiomyomas of stomach, uterine myomas, endometrial hyperplasias, cervical polyps, teratomas, hydatidiform moles, trophoblastic cell hyperplasias, hyroid adenomas, hemangiomas, lymph hyperplasias, schwannomas, neurofibromas, lipomas, and cavernous hemangiomas of the liver. Additionally, PADI4 expression was not detected in non-tumor tissues including cholecystitis, cervicitis and synovitis of osteoarthritis, except in certain acutely inflamed tissues such as in gastritis and appendicitis. Quantitative PCR and western blot analysis showed higher PADI4 expression in gastric adenocarcinomas, lung adenocarcinomas, hepatocellular carcinomas, esophageal squamous cell cancers and breast cancers (n = 5 for each disease) than in the surrounding healthy tissues. Furthermore, western blot analysis detected PADI4 expression in cultured tumor cell lines. ELISA detected increased PADI4 and cAT levels in the blood of patients with various malignant tumors compared to those in patients with chronic inflammation and benign tumors. This was consistent with immunohistochemical results. Additionally, PADI4 and cAT levels were significantly associated with higher levels of known tumor markers.

Conclusion

Our results suggest that PADI4 expression is increased in the blood and tissues of many malignant tumors, a finding useful for further understanding of tumorigenesis.

Estrogen and its receptors in cancer

The involvement of estrogen and its receptors in the development of cancer has been known for years. However, the exact mechanism responsible is far from clear. The estrogen-mediated carcinogenic process is complicated by recent findings, which reveal that estrogens have multiple functions in cells, which can be either adverse or beneficial, and that the effects of estrogen may be cell-type or organ dependent. The estrogenic effect may be also greatly influenced by the state of two estrogen receptors, ERalpha and ERbeta. This review will discuss the role and function of estrogens and its receptors in cancers of three categories: (1) Breast cancer and gynecologic cancers, (2) Cancers of endocrine organs, (3) Lung cancer and cancers of digestive system. We will also review some novel treatments aiming to interfere with relevant pathways mediated by estrogens and its receptors.

ESR1 amplification in endometrial carcinomas: hope or hyperbole?

The ESR1 gene maps 6q25 and encodes for oestrogen receptor alpha, which has been shown to play a pivotal role in the development of breast and endometrial cancer. It has recently been reported that oestrogen receptor alpha expression may be driven in some cases by ESR1 gene amplification and that this phenomenon may be an early event in breast and endometrial carcinogenesis. Although copy number gains of 6q have been reported by several groups, their prevalence, association with oestrogen receptor alpha expression, and clinical implications have been a matter of controversy. Here we discuss the key issues regarding the methods employed in the identification of ESR1 amplification, and briefly review the current literature and recent controversies on the subject of ESR1 amplification in endometrial and breast cancers.

The use of steroid sulfatase inhibitors as a novel therapeutic strategy against hormone-dependent endometrial cancer

The past few years have seen an increase in the reported incidence of endometrial carcinoma, one of the most frequently diagnosed malignancies of the female genital tract. Estrogen production is vital for the mitogenesis of endometrial tumors. Inhibition of steroid sulfatase (STS), an enzyme responsible for the synthesis of steroids with estrogenic properties, may represent a novel therapeutic target for this type of cancer. This study investigates the effects of STX64 (also known as 667Coumate and BN83495) and STX213, two potent STS inhibitors, on hormone-dependent endometrial cancer cell growth in vivo. When tested in intact mice with endometrial cancer xenografts, STX64 had limited effect on tumor growth. In contrast, the microtubule disruptor STX140 reduced tumor growth by 55%. In a hormone-dependent endometrial xenograft model in ovariectomized mice, both STX64 and STX213 given orally, daily at 1 mg/kg significantly inhibited tumor growth by 48 and 67%, respectively. However, when given orally at 1 mg/kg once weekly, only STX213 still inhibited tumor proliferation. At a higher dose of STX64 (10 mg/kg, orally, daily), a greater tumor growth inhibition of 59% was observed. Liver and tumor STS activity was completely inhibited in all daily treatment groups. Plasma estradiol (E2) levels were also significantly decreased. A significant correlation was observed between plasma E2 concentrations and STS activity, indicating the importance of circulating E2 on tumor growth. This novel study demonstrates for the first time that STS inhibitors are potent inhibitors of endometrial cancer growth in nude mice.