Steroid profile in patients with breast cancer and in mice treated with mifepristone

Progesterone receptors (PRs) are biomarkers used as prognostic and predictive factors in breast cancer, but they are still not used as therapeutic targets. We have proposed that the ratio between PR isoforms A and B (PRA and PRB) predicts antiprogestin responsiveness. The MIPRA trial confirmed the benefit of 200 mg mifepristone, administered to patients with tumors with a high PRA/PRB ratio, but dose-ranging has not been conducted. The aim of this study was to establish the plasma mifepristone levels of patients from the MIPRA trial, along with the resultant steroid profiles, and compare these with those observed in mifepristone-treated mice using therapeutic schemes able to induce the regression of experimental mammary carcinomas with high PRA/PRB ratios: 6 mg pellets implanted subcutaneously, or daily doses of 12 mg/kg body weight. The plasma levels of mifepristone and other 19 plasma steroids were measured by liquid chromatography-tandem mass spectometry. In mifepristone-treated mice, plasma levels were lower than those registered in mifepristone-treated patients (i.e. day 7 after treatment initiation, pellet-treated mice: 8.4 ± 3.9 ng/mL; mifepristone-treated patients: 300.3 ± 31.7 ng/mL (mean ± s.d.; P < 0.001)). The increase in corticoid related steroids observed in patients was not observed in mifepristone-treated mice. The increase in progesterone levels was the most significant side effect detected in mifepristone-treated mice after 14 or 21 days of treatment, probably due to an ovarian compensatory effect not observed in postmenopausal patients. We conclude that in future clinical trials using mifepristone, the possibility of lowering the standard daily dose of 200 mg should be considered.

Leveraging Antiprogestins in the Treatment of Metastatic Breast Cancer

Although incurable, the prognosis for patients with metastatic breast cancer (MBC) has considerably improved with the approvals of multiple targeted and cytotoxic therapies. For hormone receptor-positive (HR+), ie, estrogen receptor and progesterone receptor positive (ER+/PgR+) and human epidermal growth factor receptor-2 negative (ie, ERBB2 gene nonamplified or HER2-) MBC, current approved treatment options include palliative endocrine therapy (ET), cyclin-dependent kinase (CDK 4/6) inhibitors, mTOR inhibitors, and PI3 kinase inhibitors. Most treatments target ER+ disease regardless of PgR status. Although the presence of PgR is crucial for ER+ cell proliferation in both normal and malignant mammary tissue, currently, there are no approved treatments that specifically target PgR. Recent literature has demonstrated the potential of antiprogestins in the treatment of MBC both in preclinical and clinical studies. Antiprogestins, including selective PgR modulators (SPRMs) that act as PgR antagonists, are a promising class of therapeutics for overcoming endocrine resistance in patients who develop activating estrogen receptor 1 (ESR1) and phosphatidylinositol 3-kinase (PI3K) gene mutations after prior endocrine therapy. Herein, we summarize the role of PgR and antiprogestins in the treatment of MBC. Other aspects on the use of functional imaging, clinical trials incorporating novel antiprogestins, and potential treatment combinations to overcome endocrine resistance will be briefly discussed.

Progesterone receptors in normal breast development and breast cancer

Progesterone receptors (PR) play a pivotal role in many female reproductive tissues such as the uterus, the ovary, and the mammary gland (MG). Moreover, PR play a key role in breast cancer growth and progression. This has led to the development and study of different progestins and antiprogestins, many of which are currently being tested in clinical trials for cancer treatment. Recent reviews have addressed the role of PR in MG development, carcinogenesis, and breast cancer growth. Thus, in this review, in addition to making an overview on PR action in normal and tumor breast, the focus has been put on highlighting the still unresolved topics on hormone treatment involving PR isoforms and breast cancer prognosis.

Targeting progesterone signaling prevents metastatic ovarian cancer

Effective cancer prevention requires the discovery and intervention of a factor critical to cancer development. Here we show that ovarian progesterone is a crucial endogenous factor inducing the development of primary tumors progressing to metastatic ovarian cancer in a mouse model of high-grade serous carcinoma (HGSC), the most common and deadliest ovarian cancer type. Blocking progesterone signaling by the pharmacologic inhibitor mifepristone or by genetic deletion of the progesterone receptor (PR) effectively suppressed HGSC development and its peritoneal metastases. Strikingly, mifepristone treatment profoundly improved mouse survival (∼18 human years). Hence, targeting progesterone/PR signaling could offer an effective chemopreventive strategy, particularly in high-risk populations of women carrying a deleterious mutation in the BRCA gene.

New Selective Progesterone Receptor Modulators and Their Impact on the RANK/RANKL Complex Activity

Breast cancer depends on women’s age. Its chemotherapy and hormone therapy lead to the loss of bone density and disruption of the skeleton. The proteins RANK and RANKL play a pivotal role in the formation of osteoclasts. It is also well established that the same proteins (RANK and RANKL) are the main molecules that play an important role in mammary stem cell biology. Mammary stem cells guarantee differentiation of the epithelial mammary cells, the growth of which is regulated by the progesterone-induced RANKL signaling pathway. The crosstalk between progesterone receptor, stimulated by progesterone and its analogues results in RANKL to RANK binding and activation of cell proliferation and subsequently unlimited expansion of the breast cancer cells. Therefore downstream regulation of this signaling pathway is desirable. To meet this need, a new class of selective estrogen receptor modulators (SPRMs) with anti- and mesoprogestin function were tested as potential anti-RANK agents. To establish the new feature of SPRMs, the impact of tested SPRMs on RANK-RANKL proteins interaction was tested. Furthermore, the cells proliferation upon RANKL stimulation, as well as NFkB and cyclin D1 expression, induced by tested SPRMs were analyzed. Conducted experiments proved NFkB expression inhibition as well as cyclin D1 expression limitation under asoprisnil and ulipristal treatment. The established paracrine anti-proliferative activity of antiprogestins together with competitive interaction with RANK make this class of compounds attractive for further study in order to deliver more evidence of their anti-RANK activity and potential application in the breast cancer therapy together with its accompanied osteoporosis.

Progestin and antiprogestin responsiveness in breast cancer is driven by the PRA/PRB ratio via AIB1 or SMRT recruitment to the CCND1 and MYC promoters

There is emerging interest in understanding the role of progesterone receptors (PRs) in breast cancer. The aim of this study was to investigate the proliferative effect of progestins and antiprogestins depending on the relative expression of the A (PRA) and B (PRB) isoforms of PR. In mifepristone (MFP)-resistant murine carcinomas antiprogestin responsiveness was restored by re-expressing PRA using demethylating agents and histone deacetylase inhibitors. Consistently, in two human breast cancer xenograft models, one manipulated to overexpress PRA or PRB (IBH-6 cells), and the other expressing only PRA (T47D-YA) or PRB (T47D-YB), MFP selectively inhibited the growth of PRA-overexpressing tumors and stimulated IBH-6-PRB xenograft growth. Furthermore, in cells with high or equimolar PRA/PRB ratios, which are stimulated to proliferate in vitro by progestins, and are inhibited by MFP, MPA increased the interaction between PR and the coactivator AIB1, and MFP favored the interaction between PR and the corepressor SMRT. In a PRB-dominant context in which MFP stimulates and MPA inhibits cell proliferation, the opposite interactions were observed. Chromatin immunoprecipitation assays in T47D cells in the presence of MPA or MFP confirmed the interactions between PR and the coregulators at the CCND1 and MYC promoters. SMRT downregulation by siRNA abolished the inhibitory effect of MFP on MYC expression and cell proliferation. Our results indicate that antiprogestins are therapeutic tools that selectively inhibit PRA-overexpressing tumors by increasing the SMRT/AIB1 balance at the CCND1 and MYC promoters.

Recent advances in structure of progestins and their binding to progesterone receptors

The role of progesterone in women's cancers as well as the knowledge of the progesterone receptor (PR) structure has prompted the design of different therapies. The aim of this review is to describe the basic structure of PR agonists and antagonists as well as the recent treatments for illness associated with the progesterone receptor. The rational design for potent and effective drugs for the treatment of female cancer must consider the structural changes of the androgen and progestogen skeleton which are an indicator of their activity as progestins or antiprogestins. The presence of a hydroxyl group at C-17 in the progesterone skeleton brings about a loss of progestational activity whereas acetylation induces a progestational effect. The incorporation of an ethynyl functional group to the testosterone framework results in a loss of androgenic activity with a concomitant enhancement of the progestational effect. On the other hand, an ester function at C-3 of dehydroepiandrosterone skeleton induces partial antagonism to the PR.

Vaginal mifepristone for the treatment of symptomatic uterine leiomyomata: an open-label study

OBJECTIVE

To evaluate the efficacy and safety of 3 months of vaginal mifepristone treatment on leiomyoma volume and related symptoms.

DESIGN

Prospective, open-label, two tertiary centers, phase II clinical trial.

SETTING

Two tertiary medical centers in Israel.

PATIENT(S)

Thirty-three enrolled women, ages 30-53 years, diagnosed with symptomatic uterine fibroids.

INTERVENTION(S)

Patients received 10 mg mifepristone vaginally daily for 3 months.

MAIN OUTCOME MEASURE(S)

Reduction in uterine leiomyoma volume. Improvement in symptoms related to uterine fibroids was assessed with the use of the "Uterine Fibroid Symptoms Quality of Life Questionnaire" (UFS-QoL). The number of bleeding days, safety, and tolerability were secondary measures.

RESULT(S)

Mifepristone treatment significantly reduced leiomyoma volume from 135.3 ± 22.9 cc at enrollment to 101.2 ± 22.4 cc after 3 months of treatment. The UFS-QoL Score significantly decreased from 20.7 ± 0.7 at enrollment to 14.0 ± 0.8 after 3 months of treatment. The number of bleeding days significantly decreased by 3.5 days. Endometrial biopsies showed no evidence of endometrial hyperplasia or cellular atypia. There were no major side effects during the course of the study, and treatment was well tolerated.

CONCLUSION(S)

Vaginal mifepristone may offer an effective treatment option for women with symptomatic uterine leiomyoma and can improve the patients' quality of life.

CLINICAL TRIAL REGISTRATION NUMBER

NCT00881140.

Mifepristone versus placebo to treat uterine myoma: a double-blind, randomized clinical trial

Objective

To evaluate the efficacy, safety, and quality of life of 5 mg mifepristone per day compared with a placebo in treating uterine fibroids.

Design

Randomized, double-blind clinical study.

Location

Eusebio Hernández Gynecology and Obstetrics Teaching Hospital, Havana, Cuba.

Subjects

One hundred twenty-four subjects with symptomatic uterine fibroids.

Treatment

One daily capsule of 5 mg mifepristone or a mifepristone placebo over 3 months.

Variables in evaluating safety

Changes in fibroid and uterine volumes, changes in symptom prevalence and intensity, and changes in quality of life.

Results

Three months into treatment, fibroid volume was reduced by 28.5% in the mifepristone group with an increase of 1.8% in the placebo group (P = 0.031). There were significant differences between the groups with respect to pelvic pain prevalence (P = 0.006), pelvic pressure (P = 0.027), rectal pain (P = 0.013), hypermenorrhea (P < 0.001), and metrorrhagia (P = 0.002) at the end of treatment. Amenorrhea was 93.1% and 4.3% in the mifepristone and placebo groups, respectively (P < 0.001). Treatment side effects were significantly greater in the mifepristone group. Estradiol levels did not differ significantly between the placebo and mifepristone groups at the end of treatment. Improvement in quality of life was significantly greater in the categories of “symptoms” (P = 0.004) and “activity” (P = 0.045) in the mifepristone group.

Conclusion

The 5 mg dosage of mifepristone presented significantly superior efficacy compared to the placebo.

Safety and effectiveness of different dosage of mifepristone for the treatment of uterine fibroids: a double-blind randomized clinical trial

Objectives

The aim of this study was to evaluate the safety and improvement in quality of life using 10 mg and 5 mg daily doses of mifepristone for the treatment of uterine fibroids.

Design

The research was a randomized double-blind clinical study undertaken at the Eusebio Hernández Hospital in Havana, Cuba.

Subjects and methods

Seventy subjects with symptomatic uterine fibroids took one daily capsule of 10 mg or 5 mg mifepristone orally for 9 months. One to three endometrial biopsies were performed. In evaluating safety, the variables studied were endometrial changes associated with mifepristone, elevation of hepatic transaminases, side effects of mifepristone, and instances and duration of irregular bleeding.

Results

There were 30/49 (61.2%) and 13/24 (54.2%) diagnoses of endometrial changes associated with mifepristone in the 10 mg and 5 mg groups, respectively (P = 0.282). At every evaluation visit the average endometrial thickness was significantly greater in the 10 mg group than in the 5 mg group (P = 0.013, P = 0.002, and P = 0.013, respectively). Only five subjects had slight elevations in their hepatic transaminases after 9 months’ treatment. Sixteen of 35 (45.7%) and eight of 33 (24.2%) subjects had the occasional hot flush in the 10 mg and 5 mg groups, respectively (P = 0.032). In total, there were 12.9 ± 4.6 (n = 21) and 9.1 ± 3.9 (n = 18) days of irregular bleeding in the 10 mg and 5 mg groups, respectively (P = 0.009).

Conclusion

According to the study findings, a 5 mg daily dose over 9 months has a relatively better safety profile than the 10 mg dose.

Mifepristone 2.5 mg versus 5 mg daily in the treatment of leiomyoma before surgery

OBJECTIVES

To evaluate the efficacy and safety of 2.5 mg and 5 mg mifepristone during 3 months for the treatment of uterine fibroids before surgery.

DESIGN

Multicenter randomized clinical trial.

LOCATIONS

Eusebio Hernández Hospital, Havana, Cuba and the Alemán Hospital, Managua, Nicaragua.

SUBJECTS

Included in the study were 146 women with symptomatic uterine fibroids.

TREATMENT

GROUP I: half a tablet of 5 mg (2.5 mg) mifepristone taken orally every 24 hours, and Group II: one tablet of 5 mg mifepristone taken orally every 24 hours over a period of 3 months in both groups. Two endometrial biopsies were performed. VARIABLES TO EVALUATE EFFICACY: Increase in average hemoglobin, changes in fibroid and uterine volume, and symptomatic improvement.

RESULTS

The average hemoglobin at the end of treatment was 0.6 g/dL greater in the 5 mg mifepristone group (P = 0.033). In both groups there were similar reductions in fibroid volumes. Clinical improvement was more significant in the 5 mg group.

CONCLUSION

The dose to be used should be 5 mg.

Progesterone receptors--animal models and cell signalling in breast cancer. Diverse activation pathways for the progesterone receptor: possible implications for breast biology and cancer

Progesterone and estradiol, and their nuclear receptors, play essential roles in the physiology of the reproductive tract, the mammary gland and the nervous system. Estrogens have traditionally been considered associated with an increased risk of breast cancer. There is, however, compelling evidence that progesterone plays an important role in breast cell proliferation and cancer. Herein, we review the possible role of progestins and the progesterone receptor-associated signaling pathways in the development of breast cancer, as well as the therapeutic possibilities arising from our growing knowledge of the activation of the progesterone receptor by other proliferative mechanisms.