Effects of metformin on mammalian target of rapamycin in a mouse model of endometrial hyperplasia

Metformin for endometrial hyperplasia

BACKGROUND

Endometrial cancer is one of the most common gynaecological cancers in the world. Rates of endometrial cancer are rising, in part because of rising obesity rates. Endometrial hyperplasia is a precancerous condition in women that can lead to endometrial cancer if left untreated. Endometrial hyperplasia occurs more commonly than endometrial cancer. Progesterone tablets that are currently used to treat women with endometrial hyperplasia are associated with adverse effects in up to 84% of women. A levonorgestrel intrauterine device may improve compliance, but it is invasive, is not acceptable to all women, and is associated with irregular vaginal bleeding in 82% of cases. Therefore, an alternative treatment for women with endometrial hyperplasia is needed. Metformin, a drug that is often used to treat people with diabetes, has been shown, in some human studies, to reverse endometrial hyperplasia. However, the effectiveness and safety of metformin for treatment of endometrial hyperplasia remain uncertain. This is an update of a review first published in 2017.

OBJECTIVES

To determine the effectiveness and safety of metformin in treating women with endometrial hyperplasia.

SEARCH METHODS

We searched the Cochrane Gynaecology and Fertility Specialised Register, CENTRAL, MEDLINE, PubMed, Embase, Google Scholar, OpenGrey, LILACS, and two trials registers from inception to 5 September 2022. We searched the bibliographies of all relevant studies, and contacted experts in the field for any additional trials.

SELECTION CRITERIA

We included randomised controlled trials (RCTs) and cross-over trials comparing metformin (used alone or in combination with other medical therapies) versus placebo, no treatment, any conventional medical treatment, or any other active intervention for women with histologically confirmed endometrial hyperplasia of any type.

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed studies for eligibility, extracted data from included studies, assessed the risk of bias in the included studies, and assessed the certainty of the evidence for each outcome. We resolved disagreements by discussion or by deferring to a third review author. When study details were missing, review authors contacted the study authors. The primary outcome of this review was regression of endometrial hyperplasia histology (with or without atypia) towards normal histology.

MAIN RESULTS

We included seven RCTs, in which a total of 387 women took part. In the comparison, Metformin plus megestrol versus megestrol alone, we rated the certainty of the evidence as low for the outcome, regression of endometrial hyperplasia. We rated the quality of the evidence as very low for the rest of the outcomes, in all three comparisons. Although there was a low risk of selection bias, there was a high risk of bias in the blinding of personnel and outcome assessment (performance bias and detection bias) in many studies. This update identified four new RCTs and six ongoing RCTs. Metformin versus megestrol We are uncertain whether metformin increases the regression of endometrial hyperplasia towards normal histology over megestrol (odds ratio (OR) 4.89, 95% confidence interval (CI) 1.56 to 15.32; P = 0.006; 2 RCTs, 83 participants; I² = 7%; very low-certainty evidence). This evidence suggests that if the rate of regression with megestrol is 61%, the rate of regression with metformin would be between 71% and 96%. It is unresolved whether metformin results in different rates of abnormal uterine bleeding or hysterectomy compared to megestrol. No study in this comparison reported progression of hyperplasia to endometrial cancer, recurrence of endometrial hyperplasia, health-related quality of life, or adverse effects during treatment. Metformin plus megestrol versus megestrol monotherapy The combination of metformin and megestrol may enhance the regression of endometrial hyperplasia towards normal histology more than megestrol alone (OR 3.27, 95% CI 1.65 to 6.51; P = 0.0007; 4 RCTs, 258 participants; I² = 0%, low-certainty evidence). This suggests that if the rate of regression with megestrol monotherapy is 54%, the rate of regression with the addition of metformin would be between 66% and 84%. In one study, 3/8 (37.5%) of participants who took metformin had nausea that settled without further treatment. It is unresolved whether the combination of metformin and megestrol results in different rates of recurrence of endometrial hyperplasia, progression of endometrial hyperplasia to endometrial cancer, or hysterectomy compared to megestrol monotherapy. No study in this comparison reported abnormal uterine bleeding, or health-related quality of life. Metformin plus levonorgestrel (intrauterine system) versus levonorgestrel (intrauterine system) monotherapy We are uncertain whether there is a difference between groups in the regression of endometrial hyperplasia towards normal histology (OR 0.29, 95% CI 0.01 to 7.56; 1 RCT, 46 participants; very low-certainty evidence). This evidence suggests that if the rate of regression with levonorgestrel monotherapy is 96%, the rate of regression with the addition of metformin would be between 73% and 100%. It is unresolved whether the combination of metformin and levonorgestrel results in different rates of abnormal uterine bleeding, hysterectomy, or the development of adverse effects during treatment compared to levonorgestrel monotherapy. No study in this comparison reported recurrence of endometrial hyperplasia, progression of hyperplasia to endometrial cancer, or health-related quality of life.

AUTHORS' CONCLUSIONS

Review authors found insufficient evidence to either support or refute the use of metformin, specifically megestrol acetate, given alone or in combination with standard therapy, for the treatment of women with endometrial hyperplasia. Robustly designed and adequately powered randomised controlled trials, yielding long-term outcome data are still needed to address this clinical question.

The Role of mTOR and eIF Signaling in Benign Endometrial Diseases

Adenomyosis, endometriosis, endometritis, and typical endometrial hyperplasia are common non-cancerous diseases of the endometrium that afflict many women with life-impacting consequences. The mammalian target of the rapamycin (mTOR) pathway interacts with estrogen signaling and is known to be dysregulated in endometrial cancer. Based on this knowledge, we attempt to investigate the role of mTOR signaling in benign endometrial diseases while focusing on how the interplay between mTOR and eukaryotic translation initiation factors (eIFs) affects their development. In fact, mTOR overactivity is apparent in adenomyosis, endometriosis, and typical endometrial hyperplasia, where it promotes endometrial cell proliferation and invasiveness. Recent data show aberrant expression of various components of the mTOR pathway in both eutopic and ectopic endometrium of patients with adenomyosis or endometriosis and in hyperplastic endometrium as well. Moreover, studies on endometritis show that derangement of mTOR signaling is linked to the establishment of endometrial dysfunction caused by chronic inflammation. This review shows that inhibition of the mTOR pathway has a promising therapeutic effect in benign endometrial conditions, concluding that mTOR signaling dysregulation plays a critical part in their pathogenesis.

Low Expression of Stanniocalcin 1 (STC-1) Protein Is Associated With Poor Clinicopathologic Features of Endometrial Cancer

Stanniocalcin-1 (STC-1) is a glycoprotein hormone involved in diverse biological processes, including regulation of calcium phosphate homeostasis, cell proliferation, apoptosis, inflammation, oxidative stress responses, and cancer development. The role of STC-1 in endometrial cancer (EC) is yet to be elucidated. In this study, we investigated the protein expression pattern of STC-1 in a tissue microarray (TMA) cohort of hysterectomy specimens from 832 patients with EC. We then evaluated the prognostic value of STC-1 expression regarding the clinicopathologic features and patients survival over a period of 140 months. Our results revealed that in EC tissue samples, STC-1 is mainly localized in the endometrial epithelium, although some expression was also observed in the stroma. Decreased STC-1 expression was associated with factors relating to a worse prognosis, such as grade 3 endometrioid tumors (p = 0.030), deep myometrial invasion (p = 0.003), lymphovascular space invasion (p = 0.050), and large tumor size (p = 0.001). Moreover, STC-1 expression was decreased in tumors obtained from obese women (p = 0.014) and in women with diabetes mellitus type 2 (DMT2; p = 0.001). Interestingly, the data also showed an association between DNA mismatch repair (MMR) deficiency and weak STC-1 expression, specifically in the endometrial epithelium (p = 0.048). No association was observed between STC-1 expression and disease-specific survival. As STC-1 expression was particularly low in cases with obesity and DMT2 in the TMA cohort, we also evaluated the correlation between metformin use and STC-1 expression in an additional EC cohort that only included women with DMT2 (n = 111). The analysis showed no difference in STC-1 expression in either the epithelium or the stroma in women undergoing metformin therapy compared to metformin non-users. Overall, our data may suggest a favorable role for STC-1 in EC behavior; however, further studies are required to elucidate the detailed mechanism and possible applications to cancer treatment.

Roles of AMP-Activated Protein Kinase (AMPK) in Mammalian Reproduction

Reproduction is an energy demanding function and only take place in case of sufficient available energy status in mammals. Metabolic diseases such as anorexia nervosa are clinically associated with reduced fertility. AMP-activated protein kinase (AMPK), as a major regulator of cellular energy homeostasis, is activated in limited energy reserves to ensure the orderly progress of various physiological activities. In recent years, mounting evidence shows that AMPK is involved in the regulation of reproductive function through multiple mechanisms. AMPK is likely to be a metabolic sensor integrating central and peripheral signals. In this review, we aim to explore the preclinical studies published in the last decade that investigate the role of AMP-activated protein kinase in the reproductive field, and its role as a target for drug therapy of reproductive system-related diseases. We also emphasized the emerging roles of AMPK in transcriptional regulation of reproduction processes and metabolisms, which are tightly related to the energy state and fertility of an organism.

Interventions to improve insulin resistance for the prevention of endometrial cancer

This is a protocol for a Cochrane Review (Intervention). The objectives are as follows:

To determine the safety and effectiveness of interventions to improve insulin resistance for the prevention of atypical endometrial hyperplasia or endometrial cancer, or both.

Neuroprotective role of delta opioid receptors in hypoxic preconditioning

Background/aim

The purpose of the present study was to explore the neuroprotective role of delta opioid receptors (DOR) in the rat cortex in hypoxic preconditioning.

Materials and methods

Rats were randomly divided into 8 groups: control (C), sham (S), hypoxic preconditioning (PC), severe hypoxia (SH), PC + SH, PC + SH + Saline (PS), PC + SH + DPDPE (DPDPE, selective DOR agonist), PC + SH + NT (NT, Naltrindole, selective DOR antagonist). Drugs were administered intracerebroventrically. Twenty four h after the end of 3 consecutive days of PC (10% O2, 2 h/day), the rats were subjected to severe hypoxia (7% O2 for 3 h). Bcl-2 and cyt-c were measured by western blot, and caspase-3 was observed immunohistochemically.

Results

Bcl-2 expressions in the PC group were higher than in control, SH, and PC + SH groups. Even though there were no significant differences between the groups in terms of cyt-c levels, caspase-3 immunoreactivity of cortical neurons and glial cells in the severe hypoxia and NT groups were higher than in the control, sham, and hypoxic preconditioning groups. DPDPE administration diminished caspase-3 immunoreactivity compared with all of the severe hypoxia groups.

Conclusions

These results suggest that cortical cells are resistant to apoptosis via increased expression of Bcl-2 and decreased immunoreactivity of caspase-3 in the cortex, and that DOR is involved in neuroprotection induced by hypoxic preconditioning via the caspase-3 pathway in cortical neurons.

Non-Ionizing Radiation Created by Mobile Phone Progresses Endometrial Hyperplasia: An Experimental Rat Study

BACKGROUND

Non-ionizing radiation is related with many pathologies.

AIM

Determine association between non-ionizing radiation and endometrial hyperplasia.

METHODS

Fifty oopherectomized Wistar albino rats were administered Estradiol hemihydrate (4 mg/kg) to induce hyperplasia, and were exposed to 1800 MHz radiation created by a mobile phone and a signal generator working as base station. This study was carried out with 5 groups in two phases. The study groups were. Control group without any exposure; group receiving estrogen in first phase of the study; group receiving estrogen in both phases; group receiving estrogen in the first phase and exposed to non-ionizing radiation during second phase and group taking estrogen in both phases and exposed to non-ionizing radiation during the second phase. Following both phases, uterine horns were excised and evaluated based on glandular density (GD), epithelial cell height (ECH), and luminal epithelial cell height (LECH).

RESULTS

Estrogen increased all parameters during both phases (LECH, GD, and ECH values were 12,2 vs. 16,5 (p = 0.001), 34 vs. 47 (p <0.001), and 201 vs. 376.6 (p = 0.001), respectively during the first phase; LECH, GD and ECH values were 13,2 vs. 20,3 (p <0.001), 35.5 vs. 65,5 (p <0.001), 219.9 vs. 419.6 (p <0.001), respectively, during the second phase).Non-ionizing radiation increased all values without estrogen exposure (LECH, GD and ECH values were 13,2 vs. 17,2 (p = 0,074), 35,5 vs. 59 (p = 0.074), and 219 vs. 318.3 (p <0.001), respectively) or with estrogen exposure (LECH, GD, and ECH, values were 20,3 vs. 22,8 (p = 0,168), 65,5 vs. 77 (p = 0,058), and 419,6 vs. 541,6 (p = 0.004), respectively).

CONCLUSION

Non-ionizing radiation progressed endometrial hyperplasia in an experimental rat model with/without estrogen exposure.

Estrogen Signaling in Endometrial Cancer: a Key Oncogenic Pathway with Several Open Questions

Endometrial cancer is the most common gynecological cancer in the developed world, and it is one of the few cancer types that is becoming more prevalent and leading to more deaths in the USA each year. The majority of endometrial tumors are considered to be hormonally driven, where estrogen signaling through estrogen receptor α (ER) acts as an oncogenic signal. The major risk factors and some treatment options for endometrial cancer patients emphasize a key role for estrogen signaling in the disease. Despite the strong connections between estrogen signaling and endometrial cancer, important molecular aspects of ER function remain poorly understood; however, progress is being made in our understanding of estrogen signaling in endometrial cancer. Here, we discuss the evidence for the importance of estrogen signaling in endometrial cancer, details of the endometrial cancer-specific actions of ER, and open questions surrounding estrogen signaling in endometrial cancer.

The benefits of adding metformin to tamoxifen to protect the endometrium-A randomized placebo-controlled trial

BACKGROUND

We investigated whether metformin prevents tamoxifen-induced endometrial changes and insulin resistance (IR) after a diagnosis of breast cancer.

METHODS

This was a single-centre, randomized, double-blind, placebo-controlled, parallel group trial. Postmenopausal women with hormone receptor-positive breast cancer taking tamoxifen were randomly allocated to metformin 850 mg or identical placebo, twice daily, for 52 weeks. Outcome measures included double endometrial thickness (ET) measured by transvaginal ultrasound, fasting insulin, glucose and IR estimated by the homeostasis model of assessment (HOMA-IR).

RESULTS

A total of 112 women were screened and 102 randomized. Results are presented as median (range). The 101 women who took at least one dose of medication were aged 56 (43-72) years, with 5(0.5-28) years postmenopause, and had taken tamoxifen for 28.9 (0-367.4) weeks. The baseline ET was 2.9 mm (1.4-21.9) for the placebo group (n = 52) and 2.5 mm (1.3-14.8) for the metformin group (n = 50). At 52 weeks, the median ET was statistically significantly lower for the metformin (n = 36) than for the placebo group (n = 45) (2.3 mm (1.4-7.8) vs 3.0 (1.2-11.3); P = 0.05). 13.3% allocated to placebo had an ET greater than 4 mm vs 5.7% for metformin (P = 0.26). There was no endometrial atypia or cancer. Compared with placebo, metformin resulted in significantly greater baseline-adjusted reductions in weight (P < 0.001), waist circumference (0.03) and HOMA-IR (P < 0.001).

CONCLUSIONS

Metformin appears to inhibit tamoxifen-induced endometrial changes and has favourable metabolic effects. Further research into the adjuvant use of metformin after breast cancer and to prevent EH and cancer is warranted.

Effects of Metformin on Cellular Proliferation and Steroid Hormone Receptors in Patient-Derived, Low-Grade Endometrial Cancer Cell Lines

Endometrial cancer (EC) is the most common gynecologic malignancy and is the result of disruption of the balance between estrogen-stimulated growth and progesterone-induced growth modulation. Metformin has been shown to inhibit EC proliferation; however, its role in early-stage EC and its effects on steroid hormone receptors have not been adequately explored. Our aim was to examine the effects of metformin on cellular proliferation in patient-derived, low-grade EC cell lines and to determine whether it directly modulates steroid hormone receptor expression. Two novel EC cell lines were produced (EM2 and 3) from endometrial tumor tissue obtained from women undergoing surgery. Cellular proliferation was determined by the 3-(4,5-dimethylthiazolyl-2)-2, 5-diphenyltetrazolium bromide assay, and in both cell lines, metformin decreased cell proliferation in a dose-dependent (10-200 µmol/L) manner and induced apoptosis as measured by cleaved PARP. Furthermore, metformin abrogated the effects of E2 on cell proliferation. Using quantitative real-time polymerase chain reaction and Western immunoblotting, metformin significantly decreased estrogen receptor (ER) α messenger RNA abundance but did not consistently affect the expression of progesterone receptor. Estrogen receptor α protein levels significantly decreased across all metformin doses tested, which resulted in a significant decrease in the expression of the ER targets genes Keratin-19 and Wnt-1 inducible signaling pathway 2. In addition, metformin increased phosphorylation of AMPK in a dose-dependent manner (10-200 µmol/L) indicating an effect on mammalian target of rapamycin (mTOR) signaling. Our data suggest that metformin therapy represents a potential fertility-sparing option for women with early-stage EC, given its capacity to inhibit EC cell proliferation, ERα expression, and the mTOR cell proliferation pathway.

Induction of apoptosis by metformin and progesterone in estrogen-induced endometrial hyperplasia in rats: involvement of the bcl-2 family proteins

This study compared the antiproliferative effects of metformin and progesterone, via examination of the Bcl-2/Bax-caspase apoptotic pathway in estrogen-induced endometrial hyperplasia (EH) in 40 rats. Two rats died after bilateral oophorectomy, and 1 week after surgery, the remaining 38 were randomly divided into three groups: the first (control, n = 12) received 4 mg/kg 17β estradiol hemihydrate (E); the second (n = 13) received 4 mg/kg 17β estradiol hemihydrate and 50 mg/kg metformin (E + M); and the third (n = 13) received 4 mg/kg 17β estradiol hemihydrate and 1 mg/day medroxiprogesterone acetate (E + MPA). Histological markers and Bcl-2, Bax and caspase 9 expression were analyzed. Luminal epithelial thickness, density of gland and epithelial height was significantly higher in group E than in groups E + M and E + MPA. Histopathologic parameters were similar between the E + M and E + MPA groups. Bcl-2/Bax ratio was significantly decreased in the E + M and E + MPA groups and caspase 9 expression levels were significantly increased in the E + M and E + MPA groups, compared with the control group. In addition, Bcl-2/Bax ratio and caspase 9 expression were similar between the E + M and E + MPA groups. The data indicate that metformin reduces estrogen-induced EH in rats, via activation of the caspase-dependent mitochondrial apoptotic pathway, to the same degree as progesterone.

Metformin for endometrial hyperplasia

BACKGROUND

Endometrial cancer is one of the most common gynaecological cancers in the world. Rates of endometrial cancer are rising, in part because of rising obesity rates. Endometrial hyperplasia is a precancerous condition in women that can lead to endometrial cancer if left untreated. Endometrial hyperplasia occurs more commonly than endometrial cancer. Progesterone tablets currently used to treat women with endometrial hyperplasia are associated with adverse effects in up to 84% of women. The levonorgestrel intrauterine device (Mirena Coil, Bayer HealthCare Pharmaceuticals, Inc., Whippany, NJ, USA) may improve compliance, but it is invasive, is not acceptable to all women, and is associated with irregular vaginal bleeding in 82% of cases. Therefore, an alternative treatment for women with endometrial hyperplasia is needed. Metformin, a drug that is often used to treat people with diabetes, has been shown in some human studies to reverse endometrial hyperplasia. However, the effectiveness and safety of metformin for treatment of endometrial hyperplasia remain uncertain.

OBJECTIVES

To determine the effectiveness and safety of metformin in treating women with endometrial hyperplasia.

SEARCH METHODS

We searched the Cochrane Gynaecology and Fertility Specialised Register, the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE, Embase, the Cumulative Index to Nursing and Allied Health Literature (CINAHL), PubMed, Google Scholar, OpenGrey, Latin American Caribbean Health Sciences Literature (LILACS), and two trials registers from inception to 10 January 2017. We searched the bibliographies of all included studies and reviews on this topic. We also handsearched the conference abstracts of the European Society of Human Reproduction and Embryology (ESHRE) 2015 and the American Society for Reproductive Medicine (ASRM) 2015.

SELECTION CRITERIA

We included randomised controlled trials (RCTs) and cross-over trials comparing metformin (used alone or in combination with other medical therapies) versus placebo or no treatment, any conventional medical treatment, or any other active intervention for women with histologically confirmed endometrial hyperplasia of any type.

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed studies for eligibility, extracted data from included studies, and assessed the risk of bias of included studies. We resolved disagreements by discussion or by deferment to a third review author. When study details were missing, review authors contacted study authors. The primary outcome of this review was regression of endometrial hyperplasia histology (with or without atypia) towards normal histology. Secondary outcome measures included recurrence of endometrial hyperplasia, progression of endometrial hyperplasia to endometrial cancer, hysterectomy rate, abnormal uterine bleeding, health-related quality of life, and adverse effects during treatment.

MAIN RESULTS

We included three RCTs in which a total of 77 women took part. We rated the quality of the evidence as very low for all outcomes owing to very serious risk of bias (associated with poor reporting, attrition, and limitations in study design) and imprecision.We performed a meta-analysis of two trials with 59 participants. When metformin was compared with megestrol acetate in women with endometrial hyperplasia, we found insufficient evidence to determine whether there were differences between groups for the following outcomes: regression of endometrial hyperplasia histology towards normal histology (odds ratio (OR) 3.34, 95% confidence interval (CI) 0.97 to 11.57, two RCTs, n = 59, very low-quality evidence), hysterectomy rates (OR 0.91, 95% CI 0.05 to 15.52, two RCTs, n = 59, very low-quality evidence), and rates of abnormal uterine bleeding (OR 0.91, 95% CI 0.05 to 15.52, two RCTs, n = 44 , very low-quality evidence). We found no data for recurrence of endometrial hyperplasia or health-related quality of life. Both studies (n = 59) provided data on progression of endometrial hyperplasia to endometrial cancer as well as one (n = 16) reporting some adverse effects in the metformin arm, notably nausea, thrombosis, lactic acidosis, abnormal liver and renal function among others.Another trial including 16 participants compared metformin plus megestrol acetate versus megestrol acetate alone in women with endometrial hyperplasia. We found insufficient evidence to determine whether there were differences between groups for the following outcomes: regression of endometrial hyperplasia histology towards normal histology (OR 9.00, 95% CI 0.94 to 86.52, one RCT, n = 16, very low-quality evidence), recurrence of endometrial hyperplasia among women who achieve regression (OR not estimable, no events recorded, one RCT, n = 8, very low-quality evidence), progression of endometrial hyperplasia to endometrial cancer (OR not estimable, no events recorded, one RCT, n = 13, very low-quality evidence), or hysterectomy rates (OR 0.29, 95% CI 0.01 to 8.37, one RCT, n = 16, very low-quality evidence). Investigators provided no data on abnormal uterine bleeding or health-related quality of life. In terms of adverse effects, three of eight participants (37.5%) in the metformin plus megestrol acetate study arm reported nausea.

AUTHORS' CONCLUSIONS

At present, evidence is insufficient to support or refute the use of metformin alone or in combination with standard therapy - specifically, megestrol acetate - versus megestrol acetate alone, for treatment of endometrial hyperplasia. Robustly designed and adequately powered randomised controlled trials yielding long-term outcome data are needed to address this clinical question.

Role of metformin in inhibiting estrogen-induced proliferation and regulating ERα and ERβ expression in human endometrial cancer cells

Diabetes mellitus (DM) is an important factor that contributes to the development of type I endometrial cancer (EC). Previous studies have demonstrated that metformin decreases mortality and risk of neoplasms in patients with DM. Since estrogen and estrogen receptor (ER) expression has been associated with the development of EC, the present study aimed to investigate the effects of metformin on cell proliferation and ER expression in EC cell lines that are sensitive to estrogen. The viability and proliferation of Ishikawa and HEC-1-A cells were measured following treatment with metformin and/or a 5' AMP-activated protein kinase (AMPK) inhibitor (compound C) with or without treatment with estradiol (E2). In addition, the levels of ERα, ERβ, AMPK, ribosomal protein S6 kinase β-1 (p70S6K), myc proto-oncogene protein (c-myc) and proto-oncogene c-fos (c-fos) were measured following treatment. Metformin significantly decreased E2-stimulated cell proliferation; an effect that was rescued in the presence of compound C. Metformin treatment markedly increased the phosphorylation of AMPK while decreasing p70S6K phosphorylation, indicating that metformin exerts its effects through stimulation of AMPK and subsequent inhibition of the mammalian target of rapamycin (mTOR) signaling pathway. In addition, metformin significantly inhibited ERα expression while increasing ERβ expression, whereas treatment with compound C reversed these effects. Reverse transcription-quantitative polymerase chain reaction analysis demonstrated that c-fos and c-myc expression were attenuated by metformin, an effect that was rescued in the presence of compound C. Therefore, metformin regulates the expression of ERs, and inhibits estrogen-mediated proliferation of human EC cells through the activation of AMPK and subsequent inhibition of the mTOR signaling pathway.

Prospects of metformin in the treatment of endometriosis

According to recent year studies, the classical biguanide metformin has antiproliferative, proapoptotic and anti-inflammatory effects in addition to the main hypoglycemic effect. There are clinical and experimental studies these effects in the therapy of oncological and benign hyperplastic diseases. There is no data about the clinical efficacy of metformin in the therapy of endometriosis in the domestic literature, and there were a few studies in foreign sources. There was a decrease in the severity of the pain syndrome and an increase of pregnancy rate in two clinical studies with small samples. However, future studies are needed to investigate the mechanisms of the target drug effect and to develop effective regimens for the treatment of endometriosis.

Therapeutic options for management of endometrial hyperplasia

Endometrial hyperplasia (EH) comprises a spectrum of changes in the endometrium ranging from a slightly disordered pattern that exaggerates the alterations seen in the late proliferative phase of the menstrual cycle to irregular, hyperchromatic lesions that are similar to endometrioid adenocarcinoma. Generally, EH is caused by continuous exposure of estrogen unopposed by progesterone, polycystic ovary syndrome, tamoxifen, or hormone replacement therapy. Since it can progress, or often occur coincidentally with endometrial carcinoma, EH is of clinical importance, and the reversion of hyperplasia to normal endometrium represents the key conservative treatment for prevention of the development of adenocarcinoma. Presently, cyclic progestin or hysterectomy constitutes the major treatment option for EH without or with atypia, respectively. However, clinical trials of hormonal therapies and definitive standard treatments remain to be established for the management of EH. Moreover, therapeutic options for EH patients who wish to preserve fertility are challenging and require nonsurgical management. Therefore, future studies should focus on evaluation of new treatment strategies and novel compounds that could simultaneously target pathways involved in the pathogenesis of estradiol-induced EH. Novel therapeutic agents precisely targeting the inhibition of estrogen receptor, growth factor receptors, and signal transduction pathways are likely to constitute an optimal approach for treatment of EH.

Metformin for cancer and aging prevention: is it a time to make the long story short?

During the last decade, the burst of interest is observed to antidiabetic biguanide metformin as candidate drug for cancer chemoprevention. The analysis of the available data have shown that the efficacy of cancer preventive effect of metformin (MF) and another biguanides, buformin (BF) and phenformin (PF), has been studied in relation to total tumor incidence and to 17 target organs, in 21 various strains of mice, 4 strains of rats and 1 strain of hamsters (inbred, outbred, transgenic, mutant), spontaneous (non- exposed to any carcinogenic agent) or induced by 16 chemical carcinogens of different classes (polycycIic aromatic hydrocarbons, nitroso compounds, estrogen, etc.), direct or indirect (need metabolic transformation into proximal carcinogen), by total body X-rays and γ- irradiation, viruses, genetic modifications or special high fat diet, using one stage and two-stage protocols of carcinogenesis, 5 routes of the administration of antidiabetic biguanides (oral gavage, intraperitoneal or subcutaneous injections, with drinking water or with diet) in a wide ranks of doses and treatment regimens. In the majority of cases (86%) the treatment with biguanides leads to inhibition of carcinogenesis. In 14% of the cases inhibitory effect of the drugs was not observed. Very important that there was no any case of stimulation of carcinogenesis by antidiabetic biguanides. It was conclude that there is sufficient experimental evidence of anti-carcinogenic effect of antidiabetic biguanides.

Polycystic ovary syndrome: chemical pharmacotherapy

INTRODUCTION

Polycystic ovary syndrome (PCOS) is the most common reproductive endocrine disease among women of childbearing age. The clinical features are heterogeneous and vary in intensity. Hirsutism, menstrual disorders and infertility are the most frequent conditions observed; however, long-term complications (dyslipidemia, hypertension, cardiovascular disease, type 2 diabetes mellitus, endometrial cancer) are also often described. Each disorder may be managed by tailored strategies, employing sequential or combined pharmacological and/or non-pharmacological treatment.

AREAS COVERED

The authors review the drugs used for PCOS management and discuss new approaches. A systematic MEDLINE search regarding the randomized controlled trials, retrospective and observational studies about medical treatments of PCOS, the Cochrane library for reviews and also search for registered trials on ClinicalTrials.gov is performed.

EXPERT OPINION

A uniform treatment for PCOS patients does not exist. Clinicians should perform an accurate evaluation of patients' characteristics, identifying the phenotypic target and, subsequently, the best-tailored treatment to manage one or more clinical issues. Lifestyle intervention should always be the first recommended approach unless other issues indicate that drug or hormonal interventions are superior.

Metformin and gynecologic cancers

IMPORTANCE

The obese population in the United States is reaching epic proportions, and obesity is linked to an increased risk for several cancers including gynecologic cancers. Obesity is not only a risk factor but also a marker of poor prognosis. It is crucial to develop novel treatment strategies to target this population. Metformin is a biguanide drug, typically used for diabetes treatment, currently being studied to evaluate its role in the treatment and prevention of gynecologic cancers.

OBJECTIVE

The aim of this study was to review the underlying biologic mechanisms of metformin's antitumorigenic effects. We assessed the epidemiologic and preclinical data that support the use of metformin in patients with endometrial and ovarian cancer. Finally, we reviewed current clinical trials that incorporate metformin as a prevention or treatment strategy for gynecologic cancers.

EVIDENCE ACQUISITION

A thorough search of PubMed for all current literature was performed. All preclinical, clinical, and epidemiologic reviews were evaluated across all cancers, with a focus on gynecologic cancer.

RESULTS

The preclinical, epidemiologic, and clinical data evaluated in this review are strongly supportive of the use of metformin for the prevention and treatment of gynecologic cancer. On the basis of these data, centers are currently enrolling for clinical trials using metformin in patients diagnosed with gynecologic malignancies.

CONCLUSIONS AND RELEVANCE

The data supporting the use of metformin in the prevention and treatment of cancers are building, including that of endometrial and ovarian cancer. The association between obesity, insulin resistance, as well as increased risk and poor outcomes in endometrial and ovarian cancer patients makes metformin an attractive agent for the prevention and treatment of these diseases.

An estrogen-induced endometrial hyperplasia mouse model recapitulating human disease progression and genetic aberrations

Endometrial hyperplasia (EH) is a condition originating from uterine endometrial glands undergoing disordered proliferation including the risk to progress to endometrial adenocarcinoma. In recent years, a steady increase in EH cases among younger women of reproductive age accentuates the demand of therapeutic alternatives, which emphasizes that an improved disease model for therapeutic agents evaluation is concurrently desired. Here, a new hormone-induced EH mouse model was developed using a subcutaneous estradiol (E2)-sustained releasing pellet, which elevates the serum E2 level in mice, closely mimicking the effect known as estrogen dominance with underlying, pathological E2 levels in patients. The onset and progression of EH generated within this model recapitulate a clinically relevant, pathological transformation, beginning with disordered proliferation developing to simple EH, advancing to atypical EH, and then progressing to precancerous stages, all following a chronologic manner. Although a general increase in nuclear progesterone receptor (PR) expression occurred after E2 expression, a total loss in PR was noted in some endometrial glands as disease advanced to simple EH. Furthermore, estrogen receptor (ER) expression in the nucleus of endometrial cells was reduced in disordered proliferation and increased when EH progressed to atypical EH and precancerous stages. This EH model also resembles other pathological patterns found in human disease such as leukocytic infiltration, genetic aberrations in β-catenin, and joint phosphatase and tensin homolog/paired box gene 2 (PTEN/PAX2) silencing. In summary, this new and comprehensively characterized EH model is cost-effective, easily reproducible, and may serve as a tool for preclinical testing of therapeutic agents and facilitate further investigation of EH.

Do metformin a real anticarcinogen? A critical reappraisal of experimental data

Evidence has emerged that antidiabetic biguanides [phenformin (PF), buformin (BF) and metformin (MF)] are promising candidates for prevention of cancer. It was shown that antidiabetic biguanides postpone spontaneous carcinogenesis as well as inhibit carcinogenesis induced by chemical, radiation and biological factors (virus, transgene, genetic modifications, special diet, etc.) in a number of organs and tissues in various strains of mice and rats. The present review focused on some details of experiments such as design of studies, dose and route of administration of biguanide, and age of animals at start of treatment etc. Conclusion may be done that there are rather sufficient evidence of cancer-preventive activity of antidiabetic biguanides in experimental animals.

Direct effects of metformin in the endometrium: a hypothetical mechanism for the treatment of women with PCOS and endometrial carcinoma

Although a number of in vitro studies have demonstrated the antiproliferative, anti-invasive, and antimetastatic effects of metformin in multiple cancer cell types, its cellular and molecular mechanisms of anti-cancer action in the endometrium of women with polycystic ovary syndrome (PCOS) have not yet been fully elucidated. Organic cation transporters (OCTs) and multidrug and toxin extrusion proteins (MATEs) are known to be involved in metformin uptake and excretion in cells. In this article, we discuss the novel therapeutic possibilities for early-stage endometrial carcinoma (EC) in women with PCOS focusing on metformin, which might have a direct effect in the endometrium through the OCTs and MATEs. We then review the molecular mechanism(s) of the action of metformin in the endometrium and highlight possible mechanistic insights into the inhibition of cell proliferation and tumor growth and, ultimately, the reversal of early-stage EC into normal endometria in women with PCOS.

Metformin enhances tamoxifen-mediated tumor growth inhibition in ER-positive breast carcinoma

BACKGROUND

Tamoxifen, an endocrine therapy drug used to treat breast cancer, is designed to interrupt estrogen signaling by blocking the estrogen receptor (ER). However, many ER-positive patients are low reactive or resistant to tamoxifen. Metformin is a widely used anti-diabetic drug with noteworthy anti-cancer effects. We investigated whether metformin has the additive effects with tamoxifen in ER-positive breast cancer therapy.

METHODS

The efficacy of metformin alone and in combination with tamoxifen against ER-positive breast cancer was analyzed by cell survival, DNA replication activity, plate colony formation, soft-agar, flow cytometry, immunohistochemistry, and nude mice model assays. The involved signaling pathways were detected by western blot assay.

RESULTS

When metformin was combined with tamoxifen, the concentration of tamoxifen required for growth inhibition was substantially reduced. Moreover, metformin enhanced tamoxifen-mediated inhibition of proliferation, DNA replication activity, colony formation, soft-agar colony formation, and induction of apoptosis in ER-positive breast cancer cells. In addition, these tamoxifen-induced effects that were enhanced by metformin may be involved in the bax/bcl-2 apoptotic pathway and the AMPK/mTOR/p70S6 growth pathway. Finally, two-drug combination therapy significantly inhibited tumor growth in vivo.

CONCLUSION

The present work shows that metformin and tamoxifen additively inhibited the growth and augmented the apoptosis of ER-positive breast cancer cells. It provides leads for future research on this drug combination for the treatment of ER-positive breast cancer.

The key role of growth hormone-insulin-IGF-1 signaling in aging and cancer

Studies in mammals have led to the suggestion that hyperglycemia and hyperinsulinemia are important factors in aging. GH/Insulin/insulin-like growth factor-1 (IGF-1) signaling molecules that have been linked to longevity include daf-2 and InR and their homologues in mammals, and inactivation of the corresponding genes increases lifespan in nematodes, fruit flies and mice. The life-prolonging effects of caloric restriction are likely related to decreasing IGF-1 levels. Evidence has emerged that antidiabetic drugs are promising candidates for both lifespan extension and prevention of cancer. Thus, antidiabetic drugs postpone spontaneous carcinogenesis in mice and rats, as well as chemical and radiation carcinogenesis in mice, rats and hamsters. Furthermore, metformin seems to decrease the risk for cancer in diabetic patients.

Crude bark extract of Dysozylum alliarium induces alteration in histological structures and VEGF-C expression in uterus during days 4-7 of gestation in albino rat

PURPOSE

Crude bark extract (CBE) of Dysoxylum alliarium was tested in vivo for its effects on rat uterus during estrus and day 4-7 of gestation. The purpose is to study the effects of CBE on embryo implantation and VEGF-C expression during peri-implantation period to find out possible role of VEGF-C and embryo implantation.

METHODS

Threshold was determined by multiple-dose administration of CBE. CBE prepared in methanol was orally administered in a dose of 500 mg/kg/day to female rats during day 1-7 of gestation. Routine H&E histology of uteri was studied during estrus phase and days 4-7 of gestation. The vascular endothelial growth factor (VEGF-C) was studied immunohistochemically and via western blot using VEGF-C antibody.

RESULTS

The crude bark extract induced the structural aberration of uterine histology in cyclic stage and during peri-implantation. Cellular degeneration of embryo and supporting maternal tissue caused loss of embryo minimizing the litter size. Expression of VEGF-C was drastically reduced in the CBE treated females' uteri than that of the controls.

CONCLUSIONS

CBE contains potential compounds capable of fertility control as post-coital contraceptive. Effects of CBE on embryo and foetal-maternal interface either mediated through reduced VEGF-C expression or vice versa.

Comparison of antiproliferative effects of metformine and progesterone on estrogen-induced endometrial hyperplasia in rats

Metformin has been shown to inhibit the growth of endometriotic implants, and reverse endometrial hyperplasia when combined with oral contraceptive in a case report. The aim of this study is to compare the antiproliferative effects of medroxyprogesterone acetate (MPA), and metformin in oopherectomized rat endometrium. Forty oopherectomized Wistar-Albino rats were used, and assigned to receive saline, 17 β Estradiol hemihydrate (4 mg/kg), 17 β Estradiol hemihydrate (4 mg/kg) and metformin (50 mg/kg), 17 β Estradiol hemihydrate (4 mg/kg) and MPA (1 mg/day) for 14 days. Histological markers of uterotrophy, including endometrial height, luminal ephitelial cell height and density of endometrial glands on hysterectomy speciments were quantified for each specimen. Rats treated with estradiol had significantly increased in endometrial height, endomerial luminal epithelial height and endometrial gland densitiy than the other groups. Metformin and MPA acetate significantly reduced all parameters indicating endometrial hyperplasia, and uterotrophy with respect to the control group. Antiproliferative effects of metformin, and MPA was found to be comparable for all three parameters. In conclusion, metformin attenuates estrogen-induced endometrial hyperplasia in ooferectomized rats to the same degree as progesterone.

Targeting the mTOR/4E-BP pathway in endometrial cancer

Endometrial cancer is the most common gynecologic malignancy. Although it is highly treatable in the early stages of disease, therapies for advanced and recurrent disease are rarely curative. A molecular and genetic understanding of endometrial cancer involves the mTOR signaling pathway, an emerging target for treatment of type I disease (the most common presentation). Endometrial cancers show a significant reliance on the mTOR pathway for survival, and studies to date have revealed a clinical advantage in targeting this pathway. Less well developed in the study of endometrial cancer is an understanding of mTOR signaling to its major downstream effector, translational control. Given the poor rate of success for treatment of late-stage endometrial cancer, increasing attention is being directed to the development of new therapeutic approaches, including targeting the mTOR pathway. Here, we discuss the potential benefit of targeting mTOR combined with existing chemotherapies by monitoring its impact on translational regulatory pathways and key translation targets in endometrial cancer. We also highlight laboratory and clinical research findings that will provide new avenues for future research and clinical development.

The effects of metformin and letrozole on endometrium and ovary in a rat model

OBJECTIVE

The effects of metformin and letrozole on endometrium and ovarian reserve were studied in a rat model.

METHODS

Forty female Wistar albino mature rats at 8 weeks, weighing 180-260 g, were used for the study. These rats were randomly divided into four groups. Control group, eight rats, was given no medication by oral gavage. The rats in low-dose metformin group, 10 rats, were given 100 mg/kg/day of oral metformin. The rats in high-dose metformin group, 10 rats, were given 200 mg/kg/day of oral metformin. The rats in letrozole, 10 rats, were given 0.1 mg/kg/day of oral letrozole.

RESULTS

There was statistically significant difference in the endometrial thickness between the treatment groups and control group. The primordial follicle count was comparable in all treatment groups compared with control. Finally, there was no significant difference in total follicle count between the treatment groups and control.

CONCLUSIONS

This study showed that both metformin and letrozole had similar effects on endometrium and ovary in the rat model. Additionally, metformin had a little effect on endometrium than letrozole. Although metformin and letrozole might have tendency to enhance the total follicle count in the rat model, they had comparable effects on ovarian follicles and did not change the ovarian reserve compared with control.

Exploring long-term protection of normal human fibroblasts and epithelial cells from chemotherapy in cell culture

Killing of proliferating normal cells limits chemotherapy of cancer. Several strategies to selectively protect normal cells were previously suggested. Here we further explored the protection of normal cells from cell cycle-specific chemotherapeutic agents such as mitotic inhibitors (MI). We focused on a long-term cell recovery (rather than on a short-term cell survival) after a 3-day exposure to MI (paclitaxel and nocodazole). In three normal human cell types (RPE, NKE, WI-38t cells) but not in cancer cells with mutant p53, pre-treatment with nutlin-3a, a non-genotoxic inducer of wt p53, caused G1 and/or G2 arrest, thus preventing lethal mitotic arrest caused by MI and allowing normal cells to recover after removal of MI. Rapamycin, an inhibitor of the nutrient-sensing mTOR pathway, potentiated the protective effect of nutlin-3a in normal cells. Also, a combination of rapamycin and metformin, an anti-diabetic drug, induced G1 and G2 arrest selectively in normal cells and thereby protected them from MI. A combination of metformin and rapamycin also protected normal cells in low glucose conditions, whereas in contrast it was cytotoxic for cancer cells. Based on these data and the analysis of the literature, we suggest that a rational combination of metformin and rapamycin can potentiate chemotherapy with mitotic inhibitors against cancer, while protecting normal cells, thus further increasing the therapeutic window.

Biguanide metformin acts on tau phosphorylation via mTOR/protein phosphatase 2A (PP2A) signaling

Hyperphosphorylated tau plays an important role in the formation of neurofibrillary tangles in brains of patients with Alzheimer's disease (AD) and related tauopathies and is a crucial factor in the pathogenesis of these disorders. Though diverse kinases have been implicated in tau phosphorylation, protein phosphatase 2A (PP2A) seems to be the major tau phosphatase. Using murine primary neurons from wild-type and human tau transgenic mice, we show that the antidiabetic drug metformin induces PP2A activity and reduces tau phosphorylation at PP2A-dependent epitopes in vitro and in vivo. This tau dephosphorylating potency can be blocked entirely by the PP2A inhibitors okadaic acid and fostriecin, confirming that PP2A is an important mediator of the observed effects. Surprisingly, metformin effects on PP2A activity and tau phosphorylation seem to be independent of AMPK activation, because in our experiments (i) metformin induces PP2A activity before and at lower levels than AMPK activity and (ii) the AMPK activator AICAR does not influence the phosphorylation of tau at the sites analyzed. Affinity chromatography and immunoprecipitation experiments together with PP2A activity assays indicate that metformin interferes with the association of the catalytic subunit of PP2A (PP2Ac) to the so-called MID1-α4 protein complex, which regulates the degradation of PP2Ac and thereby influences PP2A activity. In summary, our data suggest a potential beneficial role of biguanides such as metformin in the prophylaxis and/or therapy of AD.

Metformin for aging and cancer prevention

Studies in mammals have led to the suggestion that hyperglycemia and hyperinsulinemia are important factors in aging. Insulin/insulin-like growth factor 1 (IGF-1) signaling molecules that have been linked to longevity include daf-2 and InR and their homologues in mammals, and inactivation of the corresponding genes increases life span in nematodes, fruit flies and mice. It is possible that the life-prolonging effect of caloric restriction is due to decreasing IGF-1 levels. Evidence has emerged that antidiabetic drugs are promising candidates for both life span extension and prevention of cancer. Thus, antidiabetic drugs postpone spontaneous carcinogenesis in mice and rats, as well as chemical and radiation carcinogenesis in mice, rats and hamsters. Furthermore metformin seems to decrease cancer risk in diabetic patients.

Isolated and combined action of tamoxifen and metformin in wild-type, tamoxifen-resistant, and estrogen-deprived MCF-7 cells

Resistance to tamoxifen (TAM) and aromatase inhibitors represents a major drawback to the treatment of hormone-dependent breast cancer, and strategies to overcome this problem are urgently needed. The anti-diabetic biguanide metformin (MF) exerts pleiotropic effects which could enhance the effectiveness of available hormonal therapies. This study modeled several aspects of hormonal therapy in women and examined the effectiveness of MF under those conditions. For cell growth evaluation, wild-type (wt), TAM-resistant (TAM-R), and long-term estradiol-deprived (LTED) MCF-7 cells, as a model of aromatase inhibitor resistance, were grown in the presence or absence of TAM or MF for 5 days. For immunoblot analysis and aromatase activity measurements, these cells were grown for 48 h. Wild-type and LTED cells were equally sensitive to the growth inhibitory effects of TAM and MF, while TAM-R cells were less sensitive to TAM than to MF. Partial additive effects on cell number of TAM combined with MF were greatest (if compared with isolated TAM action) in TAM-R and LTED cells. In contrast to the decrease in PCNA values in TAM-resistant cells treated with the TAM and MF combination, no other changes were found in the levels of this proliferation marker. These findings suggested a major component of apoptosis in the growth inhibitory effect. This was confirmed with Western blot analysis of PARP and caspase 7 as well as with apoptosis ELISA assay. MF also altered signaling pathways. AMP-kinase was stimulated by MF approximately equally in MCF-7, TAM-R, and LTED cells, while inhibition by biguanide of p-S6K as a downstream target of mTOR was strongest in TAM-R cells. Under the influence of MF, expression of ER-α was decreased in wt MCF-7 cells suggesting possible involvement of this compound in estrogen signaling. Metformin interacts additively with TAM to reduce neoplastic cells growth. The cellular context (including loss of sensitivity to TAM and estrogen deprivation) is of importance in influencing breast cancer responses to MF and to a combination of MF and TAM.

The LKB1-AMPK pathway: metabolism and growth control in tumour suppression

In the past decade, studies of the human tumour suppressor LKB1 have uncovered a novel signalling pathway that links cell metabolism to growth control and cell polarity. LKB1 encodes a serine-threonine kinase that directly phosphorylates and activates AMPK, a central metabolic sensor. AMPK regulates lipid, cholesterol and glucose metabolism in specialized metabolic tissues, such as liver, muscle and adipose tissue. This function has made AMPK a key therapeutic target in patients with diabetes. The connection of AMPK with several tumour suppressors suggests that therapeutic manipulation of this pathway using established diabetes drugs warrants further investigation in patients with cancer.