2-methoxyestradiol inhibits differentiation and is cytotoxic to osteoclasts

Intracellular Signaling Responses Induced by Radiation within an In Vitro Bone Metastasis Model after Pre-Treatment with an Estrone Analogue

2-Ethyl-3-O-sulfamoyl-estra-1,3,5(10)16-tetraene (ESE-16) is an in silico-designed estradiol analogue which has improved the parent compound’s efficacy in anti-cancer studies. In this proof-of-concept study, the potential radiosensitizing effects of ESE-16 were investigated in an in vitro deconstructed bone metastasis model. Prostate (DU 145) and breast (MDA-MB-231) tumor cells, osteoblastic (MC3T3-E1) and osteoclastic (RAW 264.7) bone cells and human umbilical vein endothelial cells (HUVECs) were representative components of such a lesion. Cells were exposed to a low-dose ESE-16 for 24 hours prior to radiation at non-lethal doses to determine early signaling and molecular responses of this combination treatment. Tartrate-resistant acid phosphatase activity and actin ring formation were investigated in osteoclasts, while cell cycle progression, reactive oxygen species generation and angiogenic protein expression were investigated in HUVECs. Increased cytotoxicity was evident in tumor and endothelial cells while bone cells appeared to be spared. Increased mitotic indices were calculated, and evidence of increased deoxyribonucleic acid damage with retarded repair, together with reduced metastatic signaling was observed in tumor cells. RAW 264.7 macrophages retained their ability to differentiate into osteoclasts. Anti-angiogenic effects were observed in HUVECs, and expression of hypoxia-inducible factor 1-α was decreased. Through preferentially inducing tumor cell death and potentially inhibiting neovascularization whilst preserving bone physiology, this low-dose combination regimen warrants further investigation for its promising therapeutic application in bone metastases management, with the additional potential of limited treatment side effects.

Urinary Biomarkers and Their Potential for the Non-Invasive Detection of Endometrial Cancer

Endometrial cancer is the most common malignancy of the female genital tract and its incidence is rising in parallel with the mounting prevalence of obesity. Early diagnosis has great potential to improve outcomes as treatment can be curative, especially for early stage disease. Current tests and procedures for diagnosis are limited by insufficient accuracy in some and unacceptable levels of invasiveness and discomfort in others. There has, therefore, been a growing interest in the search for sensitive and specific biomarkers for endometrial cancer detection based on non-invasive sampling methodologies. Urine, the prototype non-invasive sample, is attractive for biomarker discovery as it is easily accessible and can be collected repeatedly and in quantity. Identification of urinary biomarkers for endometrial cancer detection relies on the excretion of systemic biomarkers by the kidneys or urinary contamination by biomarkers shed from the uterus. In this review, we present the current standing of the search for endometrial cancer urinary biomarkers based on cytology, genomic, transcriptomic, proteomic, and metabolomic platforms. We summarize the biomarker candidates and highlight the challenges inherent in urinary biomarker discovery. We review the various technologies with promise for biomarker detection and assess these novel approaches for endometrial cancer biomarker research.

2-Methoxyoestradiol impairs mouse embryo implantation via F-spondin

The anti-implantation effects of high oestradiol (E2) concentrations could be mediated by E2 metabolites. Herein, we examined whether 2-methoxyoestradiol (2ME) impairs embryo implantation via its target protein F-spondin. Mice on Day 3 of pregnancy were treated with E2 concomitantly with the cathecol-O-methyl transferase inhibitor OR486 and the number of implanted embryos was recorded 5 days later. The effect of 2ME or 4-methoxyoestradiol (4ME) on embryo implantation was also investigated. Plasma and uterine levels of 2ME were measured 0.5, 1 or 3h after E2 treatment while the mRNA for spondin 1 (Spon1) and F-spondin were determined in the uterus 3, 6, 12 or 24h after 2ME treatment. Finally, the effect of a neutralising F-spondin antibody on the anti-implantation effect of 2ME was explored. OR486 blocked the anti-implantation effect of E2; 2ME, but not 4ME, affected embryo implantation. The 2ME concentration was increased after 0.5 and 1h in plasma and 3h in uterine fluid following E2 treatment. 2ME increased levels of Spon1 at 12 and 24h although F-spondin was increased at 12h. F-spondin antibody blocked the effect of 2ME on embryo implantation. We conclude that 2ME impairs mouse embryo implantation via activation of F-spondin in the uterus.

The Bone Sparing Effects of 2-Methoxyestradiol Are Mediated via Estrogen Receptor-α in Male Mice

2-Methoxyestradiol (2ME2), a metabolite of 17β-estradiol (E2), exerts bone sparing effects in animal models. We hypothesized that the underlying mechanism is back conversion of 2ME2 to E2, which subsequently acts via estrogen receptor (ER)α. We measured serum E2 levels in orchidectomized wild-type (WT) mice treated with 2ME2 66.6 μg/d or placebo. In placebo-treated animals, E2 was below the detection limit. In 2ME2-treated mice, the serum E2 level was 4.97 ± 0.68 pg/mL. This corresponds to the level found in diesterus in cycling female mice. Next, we investigated bone parameters in orchidectomized WT and ERα knockout mice treated with 2ME2 or placebo for 35 days. 2ME2 (6.66 μg/d) preserved trabecular and cortical bone in WT mice. Trabecular volumetric-bone mineral density was 64 ± 20%, and trabecular bone volume/total volume was 60 ± 20% higher in the metaphyseal region of the femur in the 2ME2 group, compared with placebo (P < .01). Both trabecular number and trabecular thickness were increased (P < .01). Cortical bone mineral content in the diaphyseal region of the femur was 31 ± 3% higher in the 2ME2 group, compared with placebo (P < .001). This was due to larger cortical area (P < .001). Three-point bending showed an increased bone strength in WT 2ME2-treated animals compared with placebo (maximum load [Fmax] +19±5% in the 2ME2 group, P < .05). Importantly, no bone parameter was affected by 2ME2 treatment in ERα knockout mice. In conclusion, 2ME2 treatment of orchidectomized mice results in increased serum E2. ERα mediates the bone sparing effects of 2ME2. The likely mediator of this effect is E2 resulting from back conversion of 2ME2.

2-hydroxyoestradiol and 2-methoxyoestradiol, two endogenous oestradiol metabolites, induce DNA fragmentation in Sertoli cells

Elevated intratesticular levels of hydroxyoestradiols and methoxyoestradiols, two classes of endogenous oestradiol metabolites, have been associated with male infertility. The aim of this study was to explore the effects of 2-hydroxyoestradiol (2OHE₂ ), 4-hydroxyoestradiol (4OHE₂ ), 2-methoxyoestradiol (2ME₂ ) and 4-methoxyoestradiol (4ME₂ ) on Sertoli cell viability. For this, TM4 cells were incubated with different concentrations of these metabolites for 24 h to then evaluate the viability and DNA integrity by MTS and TUNEL assay respectively. The participation of classical oestrogen receptors and the involvement of oxidative stress and apoptotic mechanisms were also evaluated co-incubating TM4 cells with these estradiol metabolites and with the drugs ICI182780, N-acetylcysteine and Z-VAD-FMK respectively. Only high concentrations of 2OHE₂ and 2ME₂ decreased cell viability inducing DNA fragmentation. In addition, ICI182780 did not block the effect of 2OHE₂ and 2ME₂ , while N-Acetylcysteine and Z-VAD-FMK only blocked the effect of 2OHE₂ . Moreover, 2OHE₂ but not 2ME₂ induced PARP and caspase-3 cleavage. Finally, lower 2OHE₂ and 2ME₂ concentrations (0.01-0.1-1.0 μmol l^-1 ) decreased Sertoli cell viability 48 h post-treatment. Our results support the hypothesis that elevated intratesticular 2OHE₂ or 2ME₂ concentrations could be related to male infertility since 2OHE₂ by apoptosis and 2ME₂ by undetermined mechanisms induce DNA fragmentation in Sertoli cells.

An estrogen analogue and promising anticancer agent refrains from inducing morphological damage and reactive oxygen species generation in erythrocytes, fibrin and platelets: a pilot study

Background

2-Methoxyestradiol is known to have antitumour and antiproliferative action in vitro and in vivo. However, when 2-methoxyestradiol is orally administered, it is rapidly oxidized by the enzyme 17β-hydroxysteriod dehydrogenase in the gastrointestinal tract. Therefore, 2-methoxyestradiol never reaches high enough concentrations in the tissue to be able to exert these antitumour properties. This resulted in the in silico-design of 2-methoxyestradiol analogues in collaboration with the Bioinformatics and Computational Biology Unit (UP) and subsequent synthesis by iThemba Pharmaceuticals (Pty) Ltd (Modderfontein, Midrand, South Africa). One such a novelty-designed analogue is 2-ethyl-3-O-sulphamoyl-estra-1, 3, 5(10)16-tetraene (ESE-16).

Methods

This pilot study aimed to determine the morphological effect and possible generation of reactive oxygen species by ESE-16 on erythrocytes and platelet samples (with and without added thrombin) by means of scanning electron microscopy, transmission electron microscopy and flow cytometry.

Results

Erythrocytes and platelets were exposed to ESE-16 at a concentration of 180nM for 24Â hours. Scanning- and transmission electron microscopy indicated that ESE-16 did not cause changes to erythrocytes, platelets or fibrin networks. Flow cytometry measurements of hydrogen peroxide and superoxide indicated that ESE-16 does not cause an increase in the generation of reactive oxygen species in these blood samples.

Conclusion

Further in vivo research is warranted to determine whether this novel in silico-designed analogue may impact on development of future chemotherapeutic agents and whether it could be considered as an antitumour agent.

2-methoxyestradiol analogue ENMD-1198 reduces breast cancer-induced osteolysis and tumor burden both in vitro and in vivo

It has been estimated that 70% of advanced breast cancer patients will face the complication of bone metastases. Three processes are pivotal during bone metastatic growth of breast cancer, namely, tumor cell proliferation, angiogenesis, and osteolysis. During tumor-induced osteolysis, a number of cytokines and growth factors are released from the degraded bone matrix. These factors stimulate further tumor growth, tumor angiogenesis, and tumor-induced osteolysis. New therapies should target all relevant processes to halt this powerful feedback loop. Here, we characterized the new 2-methoxyestradiol analogue ENMD-1198 and showed that it is cytotoxic to tumor cells. Moreover, ENMD-1198 showed both antiangiogenic and vascular disruptive properties and was capable of protecting the bone against tumor-induced osteolysis. We confirmed the in vitro data with a series of in vivo experiments showing the beneficial effects of ENMD-1198 and ENMD-1198-based combination treatments of metastatic breast cancer in bone both on tumor progression and on survival with long-term ENMD-1198 treatment. We confirmed the in vivo relevance of the ENMD-1198 protective effect on bone both with X-ray radiographs and microcomputed tomography. In addition, we combined ENMD-1198 treatment with low-dose metronomic cyclophosphamide and the bisphosphonate risedronic acid, leading to a mild increase in treatment efficacy.

Role of 2-methoxyestradiol as inhibitor of arthritis and osteoporosis in a model of postmenopausal rheumatoid arthritis

In postmenopausal rheumatoid arthritis, both the inflammatory disease and estrogen deficiency contribute to the development of osteoporosis. As hormone replacement therapy is no longer an option, we hypothesized that 2-methoxyestradiol (2me2) could be beneficial, and asked if such therapy was associated with effects on reproductive organs. Mice were ovariectomized and arthritis was induced, whereafter mice were administered 2me2, estradiol, or placebo. Clinical and histological scores of arthritis, together with bone mineral density were evaluated. Uteri weight, reactive oxygen species (ROS) from spleen cells, and characterization of cells from joints and lymph nodes were analyzed. In addition, in vivo activation of estrogen response elements (ERE) by 2me2 was evaluated. Treatment with 2me2 and estradiol decreased the frequency and severity of arthritis and preserved bone. Joint destruction was reduced, neutrophils diminished and ROS production decreased. The uterine weight increased upon long-term 2me2 exposure, however short-term exposure did not activate ERE in vivo.

In vitro and in vivo evidence for anti-inflammatory properties of 2-methoxyestradiol

2-Methoxyestradiol (2MEO) is an endogenous metabolite of 17β-estradiol that interacts with estrogen receptors and microtubules. It has acute anti-inflammatory activity in animal models that is not attributable to known antiproliferative or antiangiogenic actions. Because macrophages are central to the innate inflammatory response, we examined whether suppression of macrophage activation by 2MEO could account for some of its anti-inflammatory effects. Inflammatory mediator production stimulated by lipopolysaccharide (LPS) and interferon-γ in the J774 murine macrophage cell line or human monocytes was measured after treatment with 2MEO or the anti-inflammatory agent dexamethasone. The effect of these agents on LPS-induced acute lung inflammation in mice was also examined. 2MEO suppressed J774 macrophage interleukin-6 and prostaglandin E₂ production (by 30 and 47%, respectively, at 10 μM) and human monocyte tumor necrosis factor-α production (by 60% at 3 μM). Estradiol had no effect on J774 macrophage activation, nor did the estrogen receptor antagonist 7α-[9-[(4,4,5,5,5-pentafluoropentyl)sulfinyl]nonyl]estra-1,3,5(10)-triene-3,17β-diol (ICI 182,780) prevent the effects of 2MEO. The actions of 2MEO were not mimicked by the microtubule-interfering agents colchicine or paclitaxel. In mice exposed to LPS, bronchoalveolar lavage protein content, a measure of vascular leak and epithelial injury, was reduced to a comparable extent (~54%) by treatment with 2MEO (150 mg · kg⁻¹) or dexamethasone (1 mg · kg⁻¹). In addition, 2MEO reduced LPS-induced interleukin-6 gene expression. Thus, 2MEO modulates macrophage activation in vitro and has high-dose acute anti-inflammatory activity in vivo. These findings are consistent with the acute anti-inflammatory actions of 2MEO being mediated in part by the suppression of macrophage activation.

2-methoxyestradiol-mediated anti-tumor effect increases osteoprotegerin expression in osteosarcoma cells

Osteosarcoma is a bone tumor that frequently develops during adolescence. 2-Methoxyestradiol (2-ME), a naturally occurring metabolite of 17beta-estradiol, induces cell cycle arrest and cell death in human osteosarcoma cells. To investigate whether the osteoprotegrin (OPG) protein plays a role in 2-ME actions, we studied the effect of 2-ME treatment on OPG gene expression in human osteosarcoma cells. 2-ME treatment induced OPG gene promoter activity and mRNA levels. Also, Western blot analysis showed that 2-ME treatment increased OPG protein levels in MG63, KHOS, 143B and LM7 osteosarcoma cells by 3-, 1.9-, 2.8-, and 2.5-fold, respectively, but did not affect OPG expression in normal bone cells. In addition, increases in OPG protein levels were observed in osteosarcoma cell culture media after 3 days of 2-ME treatment. The effect of 2-ME on osteosarcoma cells was ligand-specific as parent estrogen, 17beta-estradiol and a tumorigenic estrogen metabolite, 16alpha-hydroxyestradiol, which do not affect osteosarcoma cell cycle and cell death, had no effect on OPG protein expression. Furthermore, co-treating osteosarcoma cells with OPG protein did not further enhance 2-ME-mediated anti-tumor effects. OPG-released in 2-ME-treated cultures led to an increase in osteoblastic activity and a decrease in osteoclast number, respectively. These findings suggest that OPG is not directly involved in 2-ME-mediated anti-proliferative effects in osteosarcoma cells, but rather participates in anti-resorptive functions of 2-ME in bone tumor environment.

Novel therapy with 2-methoxyestradiol for the treatment of relapsed and plateau phase multiple myeloma

PURPOSE

2-Methoxyestradiol (2ME2) is an endogenous product of estradiol metabolism with antiangiogenic and antineoplastic properties. We report on the first phase II trial of 2ME2 in multiple myeloma.

EXPERIMENTAL DESIGN

2ME2 was administered orally at a dose of 1,000 mg daily. Sixty patients (31 men and 29 women) were treated. After 39 patients were accrued, the dose was increased to 800 mg twice daily for the remaining patients.

RESULTS

Thirty-one patients had relapsed or refractory multiple myeloma, and 29 had plateau phase multiple myeloma. Median age was 60 years (range, 27-84 years). Therapy was well tolerated. Common adverse events included anemia (35%), fatigue (35%), nausea (25%), diarrhea (20%), hot flushes (20%), headache (17%), muscle cramps (15%), and upper respiratory tract infection (15%). Most adverse events were mild (grade 1-2); 12% experienced grade 3-4 adverse events. Median time to progression was 3.8 months, with 5.6 months for plateau phase disease and 2.3 months for relapsed multiple myeloma. Estimated progression-free survival rates for all patients at 1, 2, and 3 years were 24%, 17%, and 11%, respectively. Three patients, all with plateau phase disease, have been on study for over 4 years without progression at 50, 60, and 63 months, respectively. Minor response was noted in 2 patients.

CONCLUSIONS

Although no partial responses have been seen thus far, the minor responses and prolonged stable disease seen with 2ME2 therapy are promising. Plasma levels indicate that the dose of 2ME2 was inadequate. A new formulation with better bioavailability will be tested soon in multiple myeloma.

2-Methoxyestradiol suppresses osteolytic breast cancer tumor progression in vivo

2-Methoxyestradiol (2ME(2)), a physiologic metabolite of 17beta-estradiol (estrogen), has emerged as a promising cancer therapy because of its potent growth-inhibitory and proapoptotic effects on both endothelial and tumor cells. 2ME(2) also suppresses osteoclast differentiation and induces apoptosis of mature osteoclasts, and has been shown to effectively repress bone loss in an animal model of postmenopausal osteoporosis. Given these observations, we have examined whether 2ME(2) could effectively target metastasis to bone, osteolytic tumors, and soft tissue tumors. A 4T1 murine metastatic breast cancer cell line was generated that stably expressed Far Red fluorescence protein (4T1/Red) to visualize tumor development and metastasis to bone. In an intervention study, 4T1/Red cells were injected into bone marrow of the left femur and the mammary pad. In the latter study, 2ME(2) (10, 25, and 50 mg/kg/d) treatment began on the same day as surgery and was continued for the 16-day duration of study. Tumor cell growth and metastasis to bone were monitored and bone volume was determined by micro-computed tomography. 2ME(2) inhibited tumor growth in soft tissue, metastasis to bone, osteolysis, and tumor growth in bone, with maximum effects at 50 mg/kg/d. Furthermore, tumor-induced osteolysis was significantly reduced in mice receiving 2ME(2). In vitro, 2ME(2) repressed osteoclast number by inducing apoptosis of osteoclast precursors as well as mature osteoclasts. Our data support the conclusion that 2ME(2) could be an important new therapy in the arsenal to fight metastatic breast cancer.

The complex role of estrogens in inflammation

There is still an unresolved paradox with respect to the immunomodulating role of estrogens. On one side, we recognize inhibition of bone resorption and suppression of inflammation in several animal models of chronic inflammatory diseases. On the other hand, we realize the immunosupportive role of estrogens in trauma/sepsis and the proinflammatory effects in some chronic autoimmune diseases in humans. This review examines possible causes for this paradox. This review delineates how the effects of estrogens are dependent on criteria such as: 1) the immune stimulus (foreign antigens or autoantigens) and subsequent antigen-specific immune responses (e.g., T cell inhibited by estrogens vs. activation of B cell); 2) the cell types involved during different phases of the disease; 3) the target organ with its specific microenvironment; 4) timing of 17beta-estradiol administration in relation to the disease course (and the reproductive status of a woman); 5) the concentration of estrogens; 6) the variability in expression of estrogen receptor alpha and beta depending on the microenvironment and the cell type; and 7) intracellular metabolism of estrogens leading to important biologically active metabolites with quite different anti- and proinflammatory function. Also mentioned are systemic supersystems such as the hypothalamic-pituitary-adrenal axis, the sensory nervous system, and the sympathetic nervous system and how they are influenced by estrogens. This review reinforces the concept that estrogens have antiinflammatory but also proinflammatory roles depending on above-mentioned criteria. It also explains that a uniform concept as to the action of estrogens cannot be found for all inflammatory diseases due to the enormous variable responses of immune and repair systems.

Influence of 2-methoxyestradiol on cell morphology and Cdc2 Kinase activity in WHCO3 esophageal carcinoma cells

The influence of 1 x 10(-6) M exogenous 2-methoxyestradiol (2ME) was investigated on nuclear and cytoplasmic morphology, as well as Cdc (cell division cycle) 2 kinase activity in WHCO3 esophageal carcinoma cells. Mitotic indices after 18 h of 2ME exposure revealed an increase in metaphase cells (9.0%) when compared to the vehicle-treated cells (0.9%). 2ME-treated cells showed apoptotic cells at 5.6% after 18 h of exposure to dimethyl sulphoxide, compared to 0.9% in vehicle-treated cells. Increased morphological characteristics of apoptosis were observed in 2ME-treated cells after 21.5 h of exposure. Twelve percent of cells were in apoptosis when compared to the 1.6% of vehicle-treated cells. Furthermore, 42.4% of cells were arrested in metaphase after 21.5 h of 2ME exposure compared to 2.9% of vehicle-control cells present in metaphase. Cdc2 kinase activity was statistically significantly increased (1.7-fold) (P < 0.005) after 18 h of 2ME exposure when compared to vehicle-treated controls. Although the mechanism of 2ME's action on esophageal carcinoma cells is not yet elucidated, the present study revealed that 2ME caused metaphase arrest, as well as an increase in Cdc2 kinase activity that culminated in the induction of apoptosis in these cells.