Phase I trial of 2-methoxyestradiol NanoCrystal dispersion in advanced solid malignancies

2-Methoxyestradiol ameliorates doxorubicin-induced cardiotoxicity by regulating the expression of GLUT4 and CPT-1B in female rats

The clinical usage of doxorubicin (DOX) is hampered due to cardiomyopathy. Studies reveal that estrogen (E2) modulates DOX-induced cardiotoxicity. Yet, the exact mechanism is unclear. The objective of the current study is to evaluate the influence of E2 and more specifically its metabolite 2-methoxyestradiol (2ME) on cardiac remodeling and the reprogramming of cardiac metabolism in rats subjected to DOX cardiotoxicity. Seventy-two female rats were divided into groups. Cardiotoxicity was induced by administering DOX (2.5 mg/kg three times weekly for 2 weeks). In some groups, the effect of endogenous E2 was abolished by ovariectomy (OVX) or by using the estrogen receptor (ER) blocker Fulvestrant (FULV). The effect of administering exogenous E2 or 2ME in the OVX group was studied. Furthermore, the influence of entacapone (COMT inhibitor) on induced cardiotoxicity was investigated. The evaluated cardiac parameters included ECG, histopathology, cardiac-related enzymes (creatine kinase isoenzyme-MB (CK-MB) and lactate dehydrogenase (LDH)), and lipid profile markers (total cholesterol (TC), triglyceride (TG), and high-density lipoprotein (HDL)). The expression levels of key metabolic enzymes (glucose transporter-4 (GLUT4) and carnitine palmitoyltransferase-1B (CPT-1B)) were assessed. Our results displayed that co-treatment of E2 and/or 2ME with DOX significantly reduced DOX-induced cardiomyopathy and enhanced the metabolism of the heart through the maintenance of GLUT4 and CPT-1B enzymes. On the other hand, co-treatment of DOX with OVX, entacapone, or FULV increased the toxic effect of DOX by further reducing these important metabolic enzymes. E2 and 2ME abrogate DOX-induced cardiomyopathy partly through modulation of GLUT 4 and CPT-1B enzymes.

Effect of 2-methoxyestradiol on mammary tumor initiation and progression

BACKGROUND

The anti-cancer agent 2-methoxyestradiol (2-ME) has been shown to have anti-proliferative and anti-angiogenic properties. Previously, the effect of 2-ME on early- and late-stage breast cancer (BC) was investigated in vivo using a transgenic mouse model (FVB/N-Tg(MMTV-PyVT)) of spontaneous mammary carcinoma. Anti-tumor effects were observed in late-stage BC with no effect on early-stage BC. Given the contrasting results obtained from the different BC stages, we have now investigated the effect of 2-ME when administered before the appearance of palpable tumors.

METHODS

Each mouse received 100 mg/kg 2-ME on day 30 after birth, twice per week for 28 days, while control mice received vehicle only. Animals were terminated on day 59. Lung and mammary tissue were obtained for immunohistochemical analysis of CD163 and CD3 expression, and histological examination was performed to analyze tumor necrosis. Additionally, blood samples were collected to measure plasma cytokine levels.

RESULTS

2-ME increased tumor mass when compared to the untreated animals (p = .0139). The pro-tumorigenic activity of 2-ME was accompanied by lower CD3+ T-cell numbers in the tumor microenvironment (TME) and high levels of the pro-inflammatory cytokine interleukin (IL)-1β. Conversely, 2-ME-treatment resulted in fewer CD163+ cells detectable in the TME, increased levels of tumor necrosis, increased IL-10 plasma levels, and low IL-6 and IL-27 plasma levels.

CONCLUSION

Taken together, these findings suggest that 2-ME promotes early-stage BC development.

Protective Effects of 2-Methoxyestradiol on Acute Isoproterenol-Induced Cardiac Injury in Rats

Myocardial injury (MI) is an important pathological driver of mortality worldwide., and arises as a result of imbalances between myocardial oxygen demand and supply. In MI, oxidative stress often leads to inflammatory changes and apoptosis. Current therapies for MI are known to cause various adverse effects. Consequently, the development of new therapeutic agents with a reduced adverse event profile is necessary. In this regard, 2-methoxyestradiol (2ME), the metabolic end-product of oestradiol, possesses anti-inflammatory and antioxidant properties. The aim of this research is to assess the impact of 2ME on cardiac injury caused by isoproterenol (ISO) in rats. Animals were separated into six groups; controls, and those receiving 2ME (1 mg/kg), ISO (85 mg/kg), ISO + 2ME (0.25 mg/kg), ISO + 2ME (0.5 mg/kg), and ISO + 2ME (1 mg/kg). 2ME significantly attenuated ISO-induced changes in electrocardiographic changes and the cardiac histological pattern. This compound also decreased lactate dehydrogenase activity, creatine kinase myocardial band and troponin levels. The ability of 2ME to act as an antioxidant was shown by a decrease in malondialdehyde concentration, and the restoration of glutathione levels and superoxide dismutase activity. Additionally, 2ME antagonized inflammation and cardiac cell apoptosis, a process determined to be mediated, at least partially, by suppression of Gal-3/TLR4/MyD88/NF-κB signaling pathway. 2ME offers protection against acute ISO-induced MI in rats and offers a novel therapeutic management option.

Effect of 2-methoxyestradiol treatment on early- and late-stage breast cancer progression in a mouse model

The prevalence of breast cancer (BC) continues to increase and is the leading cause of cancer deaths in many countries. Numerous in vitro and in vivo studies have demonstrated that 2-methoxyestradiol (2-ME) has antiproliferative and antiangiogenic effects in BC, thereby inhibiting tumour growth and metastasis. We compared the effect of 2-ME in early- and late-stage BC using a transgenic mouse model-FVB/N-Tg(MMTV-PyVT)-of spontaneously development of aggressive mammary carcinoma with lung metastasis. Mice received 100 mg/kg 2-ME treatment immediately when palpable mammary tumours were identified (early-stage BC; Experimental group 1) and 28 days after palpable mammary tumours were detected (late-stage BC; Experimental group 2). 2-ME was administered via oral gavage three times a week for 28 days after initiation of treatment, whereas control mice received the vehicle containing 10% dimethyl sulfoxide and 90% sunflower oil for the same duration as the treatment group. Mammary tumours were measured weekly over the 28 days and at termination, blood, mammary and lung tissue were collected for analysis. Mice with a tumour volume threshold of 4000 mm3 were killed before the treatment regime was completed. 2-ME treatment of early-stage BC led to lower levels of mammary tumour necrosis, whereas tumour mass and volume were increased. Additionally, necrotic lesions and anti-inflammatory CD163-expressing cells were more frequent in pulmonary metastatic tumours in this group. In contrast, 2-ME treatment of late-stage BC inhibited tumour growth over the 28-day period and resulted in increased CD3+ cell number and tumour necrosis. Furthermore, 2-ME treatment slowed down pulmonary metastasis but did not increase survival of late-stage BC mice. Besides late-stage tumour necrosis, none of the other results were statistically significant. This study demonstrates that 2-ME treatment has an antitumour effect on late-stage BC, however, with no increase in survival rate, whereas the treatment failed to demonstrate any benefit in early-stage BC.

Cellular, Biophysical and in Silico Binding Study of β-Estradiol-6-one 6- (O-carboxy methyl Oxime) with Tubulin in Search of Antimitotic Derivative of 2-Methoxy Estradiol

The tubulin-microtubule system is a major target for a variety of small molecules which can interfere in cell cycle progression. Therefore, it serves as a prospective to control the incessant division of cancer cells. To identify novel inhibitors of the tubulin-microtubule system, a group of estrogen derivatives has been tested with tubulin as a target since literature surveys portray coveted behaviour from the same. Out of them, β-Estradiol-6-one 6- (O-carboxy methyl Oxime) abbreviated as Oxime, disrupts the cytoskeleton network and induces apoptosis with nuclei fragmentation. It has been revealed from the work that Oxime targets the colchicine binding site and binds tubulin in an entropy-driven manner. This suggests that structural variation might play a key role in modulating the anti-mitotic role of estrogen derivatives. Our work reveals that Oxime might serve as a lead molecule to nurture anti-cancer research, having the potential for recovery of the vast cancer population.

2-Methoxyestradiol-3,17-O,O-bis-sulfamate inhibits store-operated Ca2+ entry in T lymphocytes and prevents experimental autoimmune encephalomyelitis

Ca²⁺ signaling is one of the essential signaling systems for T lymphocyte activation, the latter being an essential step in the pathogenesis of autoimmune diseases such as multiple sclerosis (MS). Store-operated Ca²⁺ entry (SOCE) ensures long lasting Ca²⁺ signaling and is of utmost importance for major downstream T lymphocyte activation steps, e.g. nuclear localization of the transcription factor 'nuclear factor of activated T cells' (NFAT). 2-Methoxyestradiol (2ME2), an endogenous metabolite of estradiol (E2), blocks nuclear translocation of NFAT. The likely underlying mechanism is inhibition of SOCE, as shown for its synthetic sulfamate ester analogue 2-ethyl-3-sulfamoyloxy-17β-cyanomethylestra-1,3,5(10)-triene (STX564). Here, we demonstrate that another synthetic bis-sulfamoylated 2ME2 derivative, 2-methoxyestradiol-3,17-O,O-bis-sulfamate (2-MeOE2bisMATE, STX140), an orally bioavailable, multi-targeting anticancer agent and potent steroid sulfatase (STS) inhibitor, antagonized SOCE in T lymphocytes. Downstream events, e.g. secretion of the pro-inflammatory cytokines interferon-γ and interleukin-17, were decreased by STX140 in in vitro experiments. Remarkably, STX140 dosed in vivo completely blocked the clinical disease in both active and transfer experimental autoimmune encephalomyelitis (EAE) in Lewis rats, a T cell-mediated animal model for MS, at a dose of 10 mg/kg/day i.p., whereas neither 2ME2 nor Irosustat, a pure STS inhibitor, showed any effect. The STS inhibitory activity of STX140 is therefore not responsible for its activity in this model. Taken together, inhibition of SOCE by STX140 resulting in full antagonism of clinical symptoms in EAE in the Lewis rat, paired with the known excellent bioavailability and pharmaceutical profile of this drug, open potentially new therapeutic avenues for the treatment of MS.

Identification of chemotherapy targets reveals a nucleus-to-mitochondria ROS sensing pathway

Multiple chemotherapies are proposed to cause cell death in part by increasing the steady-state levels of cellular reactive oxygen species (ROS). However, for most of these drugs exactly how the resultant ROS function and are sensed is poorly understood. In particular, it's unclear which proteins the ROS modify and their roles in chemotherapy sensitivity/resistance. To answer these questions, we examined 11 chemotherapies with an integrated proteogenomic approach identifying many unique targets for these drugs but also shared ones including ribosomal components, suggesting one mechanism by which chemotherapies regulate translation. We focus on CHK1 which we find is a nuclear H ₂ O ₂ sensor that promotes an anti-ROS cellular program. CHK1 acts by phosphorylating the mitochondrial-DNA binding protein SSBP1, preventing its mitochondrial localization, which in turn decreases nuclear H ₂ O ₂ . Our results reveal a druggable nucleus-to-mitochondria ROS sensing pathway required to resolve nuclear H ₂ O ₂ accumulation, which mediates resistance to platinum-based chemotherapies in ovarian cancers.

Nanoparticles in the diagnosis and treatment of cancer metastases: Current and future perspectives

Metastasis accounts for greater than 90% of cancer-related deaths. Despite recent advancements in conventional chemotherapy, immunotherapy, targeted therapy, and their rational combinations, metastatic cancers remain essentially untreatable. The distinct obstacles to treat metastases include their small size, high multiplicity, redundancy, therapeutic resistance, and dissemination to multiple organs. Recent advancements in nanotechnology provide the numerous applications in the diagnosis and prophylaxis of metastatic diseases, including the small particle size to penetrate cell membrane and blood vessels and their capacity to transport complex molecular 'cargo' particles to various metastatic regions such as bones, brain, liver, lungs, and lymph nodes. Indeed, nanoparticles (NPs) have demonstrated a significant ability to target specific cells within these organs. In this regard, the purpose of this review is to summarize the present state of nanotechnology in terms of its application in the diagnosis and treatment of metastatic cancer. We intensively reviewed applications of NPs in fluorescent imaging, PET scanning, MRI, and photoacoustic imaging to detect metastasis in various cancer models. The use of targeted NPs for cancer ablation in conjunction with chemotherapy, photothermal treatment, immuno therapy, and combination therapy is thoroughly discussed. The current review also highlights the research opportunities and challenges of leveraging engineering technologies with cancer cell biology and pharmacology to fabricate nanoscience-based tools for treating metastases.

Radiosensitization of Breast Cancer Cells with a 2-Methoxyestradiol Analogue Affects DNA Damage and Repair Signaling In Vitro

Radiation resistance and radiation-related side effects warrant research into alternative strategies in the application of this modality to cancer treatment. Designed in silico to improve the pharmacokinetics and anti-cancer properties of 2-methoxyestradiol, 2-ethyl-3-O-sulfamoyl-estra-1,3,5(10)16-tetraene (ESE-16) disrupts microtubule dynamics and induces apoptosis. Here, we investigated whether pre-exposure of breast cancer cells to low-dose ESE-16 would affect radiation-induced deoxyribonucleic acid (DNA) damage and the consequent repair pathways. MCF-7, MDA-MB-231, and BT-20 cells were exposed to sub-lethal doses of ESE-16 for 24 h before 8 Gy radiation. Flow cytometric quantification of Annexin V, clonogenic studies, micronuclei quantification, assessment of histone H2AX phosphorylation and Ku70 expression were performed to assess cell viability, DNA damage, and repair pathways, in both directly irradiated cells and cells treated with conditioned medium. A small increase in apoptosis was observed as an early consequence, with significant repercussions on long-term cell survival. Overall, a greater degree of DNA damage was detected. Moreover, initiation of the DNA-damage repair response was delayed, with a subsequent sustained elevation. Radiation-induced bystander effects induced similar pathways and were initiated via intercellular signaling. These results justify further investigation of ESE-16 as a radiation-sensitizing agent since pre-exposure appears to augment the response of tumor cells to radiation.

Adverse effects of 2-Methoxyestradiol on mouse oocytes during reproductive aging

2-Methoxyestradiol (2-ME2) is a metabolite of 17β-estradiol and is currently in clinical trials as an antitumor agent. Here we found 2-ME2 level remains stable in the local environment of ovaries but declines in serum in aging mice, and exogenous 2-ME2 impacts the meiotic maturation of mouse oocytes in dose-dependent manner. In vitro 2-ME2 application arrested oocytes at metaphase I (MI), with abnormal spindle structure and chromosome alignment. 2-ME2 exposure induced excessive production of reactive oxygen species (ROS) and malondialdehyde, as well as accelerated apoptosis progression. 2-ME2 unbalanced mitochondrial dynamics by increasing DRP1 and MFN1 while decreasing Opa1. Similar phenotypes were also observed in oocytes from mice injected intraperitoneally with 2-ME2. Taken together, this study indicates 2-ME2 exposure impairs oocyte meiotic maturation through inducing mitochondrial imbalance, oxidative stress and apoptosis. The gradual decline in oocyte quality and quantity may be associated with the stable 2-ME2 in ovaries during female reproductive aging.

2-Methoxyestradiol inhibits carotid artery intimal hyperplasia induced by balloon injury via inhibiting JAK/STAT axis in rats

Intimal hyperplasia (IH) is a common complication of vascular interventional procedures that leads to narrowing of the vessel lumen. 2-Methoxyestradiol (2ME), an estrogen metabolite, has numerous pharmacological actions, including vasoprotective and antiproliferative activities. The present study aimed to evaluate the potential of 2ME, prepared as a self-nanoemulsifying drug delivery system (SNEDDS), to inhibit IH induced by balloon injury (BI) in the rat carotid artery. The prepared 2ME SNEDDS had a particle size of 119 ± 2.3 nm and a zeta potential of -7.1 ± 1.4 mV. Animals were divided into 5 groups, namely control, sham, BI, BI + 2ME (100 μg/kg), and BI + 2ME (250 μg/kg). The obtained data indicated that 2ME significantly inhibited IH as indicated by the histological and morphometric assessment of the intima, media and lumen areas. This was associated with enhanced expression of Bax and inhibited expression of Bcl2 mRNA. Furthermore, 2ME exhibited significant antioxidant properties as evidenced by prevention of malondialdehyde accumulation as well as superoxide dismutase and catalase enzymatic exhaustion. In addition, 2ME showed significant anti-inflammatory actions as it significantly inhibited vascular content of interleukin-6, tumor necrosis factor-alpha, and nuclear factor-κB. The observed vasoprotective activities of 2ME were accompanied by inhibition of Janus kinase/signal transducers and activators of transcription (JAK/STAT) protein expression. In conclusion, this study revealed that 2ME ameliorates balloon injury-induced IH in rats via suppressing JAK/STAT axis. This may help to develop new strategies to combat IH.

2-Methoxyestradiol TPGS Micelles Attenuate Cyclosporine A-Induced Nephrotoxicity in Rats through Inhibition of TGF-β1 and p-ERK1/2 Axis

The immunosuppressant cyclosporine A (CSA) has been linked to serious renal toxic effects. Although 2-methoxyestradiol (2ME) possesses a wide range of pharmacological abilities, it suffers poor bioavailability after oral administration. The purpose of this study was to evaluate the potential of 2ME loaded D-ɑ-tocopheryl polyethylene glycol succinate (TPGS) micelles to prevent CSA-induced nephrotoxicity in rats. A 2ME-TPGS was prepared and showed particle size of 44.3 ± 3.5 nm with good entrapment efficiency and spherical structures. Male Wistar rats were divided into 5 groups, namely: Control, Vehicle, CSA, CSA + 2ME-Raw, and CSA + 2ME-Nano. CSA was injected daily at a SC dose of 20 mg/kg. Both 2ME-Raw and 2ME-Nano were given daily at oral doses of 5 mg/kg. Treatments continued for three successive weeks. 2ME-TPGS exerted significant protective effects against CSA nephrotoxicity. This was evidenced in ameliorating deterioration of renal functions, attenuation of pathological changes in kidney tissues, exerting significant anti-fibrotic, antioxidant, and anti-inflammatory effects together with significant anti-apoptotic effects. Western blot analyses showed both 2ME-Raw and 2ME-Nano significantly inhibited protein expression of TGF-β1 and phospho-ERK (p-ERK). It was observed that 2ME-TPGS, in almost all experiments, exerted superior protective effects as compared with 2ME-Raw. In conclusion, 2ME loaded in a TPGS nanocarrier possesses significant protective activities against CSA-induced kidney injury in rats. This is attributable to 2ME anti-fibrotic, antioxidant, anti-inflammatory, and anti-apoptotic activities which are mediated at least partly by inhibition of TGF-β1/p-ERK axis.

Optimized 2-methoxyestradiol invasomes fortified with apamin: a promising approach for suppression of A549 lung cancer cells

Certain anticancer agents selectively target the nucleus of cancer cells. One such drug is 2-methoxyestradiol (2ME), which is used for treating lung cancer. To improve the therapeutic effectiveness of these agents, many new methods have been devised. 2ME was entrapped into the core of hydrophobic invasomes (INVA) covered with Phospholipon 90G and apamin (APA). The Box–Behnken statistical design was implemented to enhance the composition. Using Design-Expert software (Stat-Ease Inc., Minneapolis, MN), the INVA component quantities were optimized to obtain spherical particles with the smallest size, that is, a diameter of 167.8 nm. 2ME-INVA-APA significantly inhibited A549 cells and exhibited IC₅₀ of 1.15 ± 0.04 µg/mL, which is lower than raw 2ME (IC₅₀ 5.6 ± 0.2 µg/mL). Post 2ME-INVA-APA administration, a significant rise in cell death and necrosis was seen among the A549 cells compared to those treated with plain formula or 2ME alone. This effect was indicated by increased Bax expression and reduced Bcl-2 expression, as well as mitochondrial membrane potential loss. Moreover, the cell cycle analysis showed that 2ME-INVA-APA arrests the G2-M phase of the A549 cells. Additionally, it was observed that the micellar formulation of the drug increased the cell count in pre-G1, thereby exhibiting phenomenal apoptotic potential. Furthermore, it up-regulates caspase-9 and p53 and downregulates TNF-α and NF-κβ. Collectively, these findings showed that our optimized 2ME-INVA-APA could easily seep through the cell membrane and induce apoptosis in relatively low doses.

2-Methoxyestradiol Inhibits Radiation-Induced Skin Injuries

Radiation-induced skin injury (RISI) is a main side effect of radiotherapy for cancer patients, with vascular damage being a common pathogenesis of acute and chronic RISI. Despite the severity of RISI, there are few treatments for it that are in clinical use. 2-Methoxyestradiol (2-ME) has been reported to regulate the radiation-induced vascular endothelial-to-mesenchymal transition. Thus, we investigated 2-ME as a potent anti-cancer and hypoxia-inducible factor 1 alpha (HIF-1α) inhibitor drug that prevents RISI by targeting HIF-1α. 2-ME treatment prior to and post irradiation inhibited RISI on the skin of C57/BL6 mice. 2-ME also reduced radiation-induced inflammation, skin thickness, and vascular fibrosis. In particular, post-treatment with 2-ME after irradiation repaired the damaged vessels on the irradiated dermal skin, inhibiting endothelial HIF-1α expression. In addition to the increase in vascular density, post-treatment with 2-ME showed fibrotic changes in residual vessels with SMA⁺CD31⁺ on the irradiated skin. Furthermore, 2-ME significantly inhibited fibrotic changes and accumulated DNA damage in irradiated human dermal microvascular endothelial cells. Therefore, we suggest that 2-ME may be a potent therapeutic agent for RISI.

2-Methoxy-estradiol Loaded Alpha Lipoic Acid Nanoparticles Augment Cytotoxicity in MCF-7 Breast Cancer Cells

The therapeutic effectiveness of anticancer drugs with a selective target for the nucleus of cancer cells may be improved by experimental approaches. In this regard, the formulation of anticancer drugs is considered one of the best ways to improve their effectiveness in targeting cancerous tissues. To enhance the anticancer activity of 2-methoxy-estradiol (2 ME) for breast cancer, 2-methoxyestradiol loaded alpha lipoic acid nanoparticles have been formulated. The prepared formula was observed to be spherical with a nanometer-scale and low PDI size (.234). The entrapment efficiency of the 2ME-ALA NPs was 87.32 ± 2.21% with > 85% release of 2 ME within 24 h. There was a 1.2-fold increase in apoptosis and a 3.46-fold increase in necrosis of the MCF-7 cells when incubated with 2ME-ALA NPs when compared to control cells. This increased apoptosis was also associated with increased ROS and increased p53 expression in 2ME-ALA NPs treated cells compared to the raw-2 ME group. Evaluation of cell-cycle data showed a substantial arrest of the G2-M phase of the MCF-7 cells when incubated with 2ME-ALA NPs. At the same time, a dramatically increased number of pre-G1 cells showed the increased apoptotic potential of the 2 ME when administered via the proposed formulation. In the end, the differential upregulation of caspase-3, p53, and ROS in MCF-7 cells established the superiority of the 2ME-ALA-Ms approach in targeting breast cancer. In summary, these results demonstrate that 2ME-ALA NPs are an efficient delivery tool for controlling the growth of breast cancer cells.

Oxymestane, a cytostatic steroid derivative of exemestane with greater antitumor activity in non-estrogen-dependent cell lines

A new promising steroid derivative of Exemestane (Exe), the drug used for the treatment of estrogen-dependent breast cancer, was synthesized and evaluated against a set of human cancer cell lines. The new compound (Oxymestane-D1, Oxy) was tested comparatively with Exe against colon (C2BBe1, WiDr), liver (HepG2, HuH-7), lung (A549, H1299) and prostate (LNCaP, PC3) human cancer cell lines. Likewise, its effect on human colon normal cells (CCD-841 CoN) and human normal fibroblast cells (HFF-1) was studied. The cytostatic activity of Oxy was also compared with that of the reference cytostatic drugs used in chemotherapy protocols, namely carboplatin, cisplatin, doxorubicin, epirubicin, etoposide, flutamide, 5-fluorouracil, irinotecan, oxaliplatin and sorafenib. In all cell lines tested, Oxy proved to be more powerful cytostatic than Exe. Additionally, the IC₅₀ at 72 h showed a three-fold activity greater than 5-fluorouracil in the WiDr cell line, twice as high as cisplatin for cell line A549 and five times higher than cisplatin for cell line H1299. Also, Oxy surprisingly revealed to induce DNA damage and inhibit the DNA damage response (DDR) proteins ATM, ATR, CHK1 and CHK2. The results obtained allow concluding that Oxy can be a promising anticancer agent to be used in chemotherapy protocols. Furthermore, its ability to inhibit crucial components of DDR can also be useful for the monotherapy or for combination with chemo and/or radiotherapy of cancer.

Development, Optimization and Evaluation of 2-Methoxy-Estradiol Loaded Nanocarrier for Prostate Cancer

The therapeutic efficacy of antineoplastic agents possessing a selective target to the nucleus of the cancer cells could be enhanced through novel formulation approaches. Thus, toward the improvement of the anticancer potential of 2-methoxy estradiol (2 ME) on prostate cancer, the drug was entrapped into the hydrophobic micelles core formulated with Phospholipon 90G and d-α-tocopheryl polyethylene glycol succinate (TPGS). Optimization of the formulation was done by Box-Behnken statistical design using Statgraphics software to standardize percentages of TPGS and phospholipid to obtain the smallest particle size. The optimized formulation was found to be spherical with nanometer size of 152 ± 5.2 nm, and low PDI (0.234). The entrapment efficiency of the micelles was 88.67 ± 3.21% with >93% release of 2 ME within 24 h. There was a 16-fold increase in apoptosis and an 8-fold increase in necrosis of the PC-3 cells when incubated with 2 ME micellar delivery compared to control cells (2.8 ± 0.2%). This increased apoptosis was further correlated with increased BAX expression (11.6 ± 0.7) and decreased BCL-2 expression (0.29 ± 0.05) in 2 ME micelles treated cells when compared to the control group. Further, loss of mitochondrial membrane potential (∼50-fold) by the drug-loaded micelles and free drug compared to control cells was found to be due to the generation of ROS. Findings on cell cycle analysis revealed the significant arrest of the G2-M phase of the PC-3 cells when incubated with the optimized formulation. Simultaneously, a significantly increased number of cells in pre-G1 revealed the maximum apoptotic potential of the drug when delivered via micellar formulation. Finally, upregulation of caspase-9, p53, and NO, with downregulation of TNF-α, NF-κβ, and inflammatory mediators of the PC-3 cells established the superiority of the micellar approach against prostate cancer. In summary, the acquired results highlighted the potentiality of the 2 ME-micellar delivery tool for controlling the growth of prostate cancer cells for improved efficacy.

Would the Recommended Dose Have Been Different Using Novel Dose-Finding Designs? Comparing Dose-Finding Designs in Published Trials

Simulation studies have shown that novel designs such as the continual reassessment method and the Bayesian optimal interval (BOIN) design outperform the 3 + 3 design by recommending the maximum tolerated dose (MTD) more often, using less patients, and allotting more patients to the MTD. However, it is not clear whether these novel designs would have yielded different results in the context of real-world dose-finding trials. This is a commonly mentioned reason for the continuous use of 3 + 3 designs for oncology trials, with investigators considering simulation studies not sufficiently convincing to warrant the additional design complexity of novel designs.

METHODS

We randomly sampled 60 published dose-finding trials to obtain 22 that used the 3 + 3 design, identified an MTD, published toxicity data, and had more than two dose levels. We compared the published MTD with the estimated MTD using the continual reassessment method and BOIN using target toxicity rates of 25% and 30% and toxicity data from the trial. Moreover, we compared patient allocation and sample size assuming that these novel designs had been implemented.

RESULTS

Model-based designs chose dose levels higher than the published MTD in about 40% of the trials, with estimated and observed toxicity rates closer to the target toxicity rates of 25% and 30%. They also assigned less patients to suboptimal doses and permitted faster dose escalation.

CONCLUSION

This study using published dose-finding trials shows that novel designs would recommend different MTDs and confirms the advantages of these designs compared with the 3 + 3 design, which were demonstrated by simulation studies.

Evidence for 2-Methoxyestradiol-Mediated Inhibition of Receptor Tyrosine Kinase RON in the Management of Prostate Cancer

2-Methoxyestradiol (2-ME₂) possesses anti-tumorigenic activities in multiple tumor models with acceptable tolerability profile in humans. Incomplete understanding of the mechanism has hindered its development as an anti-tumorigenic compound. We have identified for the first-time macrophage stimulatory protein 1 receptor (MST1R) as a potential target of 2-ME₂ in prostate cancer cells. Human tissue validation studies show that MST1R (a.k.a RON) protein levels are significantly elevated in prostate cancer tissues compared to adjacent normal/benign glands. Serum levels of macrophage stimulatory protein (MSP), a ligand for RON, is not only associated with the risk of disease recurrence, but also significantly elevated in samples from African American patients. 2-ME₂ treatment inhibited mechanical properties such as adhesion and elasticity that are associated with epithelial mesenchymal transition by downregulating mRNA expression and protein levels of MST1R in prostate cancer cell lines. Intervention with 2-ME₂ significantly reduced tumor burden in mice. Notably, global metabolomic profiling studies identified significantly higher circulating levels of bile acids in castrated animals that were decreased with 2-ME₂ intervention. In summary, findings presented in this manuscript identified MSP as a potential marker for predicting biochemical recurrence and suggest repurposing 2-ME₂ to target RON signaling may be a potential therapeutic modality for prostate cancer.

Regulation of Mitochondrial Dynamics in Parkinson's Disease-Is 2-Methoxyestradiol a Missing Piece?

Mitochondria, as "power house of the cell", are crucial players in cell pathophysiology. Beyond adenosine triphosphate (ATP) production, they take part in a generation of reactive oxygen species (ROS), regulation of cell signaling and cell death. Dysregulation of mitochondrial dynamics may lead to cancers and neurodegeneration; however, the fusion/fission cycle allows mitochondria to adapt to metabolic needs of the cell. There are multiple data suggesting that disturbed mitochondrial homeostasis can lead to Parkinson's disease (PD) development. 2-methoxyestradiol (2-ME), metabolite of 17β-estradiol (E2) and potential anticancer agent, was demonstrated to inhibit cell growth of hippocampal HT22 cells by means of nitric oxide synthase (NOS) production and oxidative stress at both pharmacologically and also physiologically relevant concentrations. Moreover, 2-ME was suggested to inhibit mitochondrial biogenesis and to be a dynamic regulator. This review is a comprehensive discussion, from both scientific and clinical point of view, about the influence of 2-ME on mitochondria and its plausible role as a modulator of neuron survival.

Characterization of Signalling Pathways That Link Apoptosis and Autophagy to Cell Death Induced by Estrone Analogues Which Reversibly Depolymerize Microtubules

The search for novel anti-cancer compounds which can circumvent chemotherapeutic drug resistance and limit systemic toxicity remains a priority. 2-Ethyl-3-O-sulphamoyl-estra-1,3,5(10)15-tetraene-3-ol-17one (ESE-15-one) and 2-ethyl-3-O-sulphamoyl-estra-1,3,5(10)16-tetraene (ESE-16) are sulphamoylated 2-methoxyestradiol (2-ME) analogues designed by our research team. Although their cytotoxicity has been demonstrated in vitro, the temporal and mechanistic responses of the initiated intracellular events are yet to be determined. In order to do so, assays investigating the compounds' effects on microtubules, cell cycle progression, signalling cascades, autophagy and apoptosis were conducted using HeLa cervical- and MDA-MB-231 metastatic breast cancer cells. Both compounds reversibly disrupted microtubule dynamics as an early event by binding to the microtubule colchicine site, which blocked progression through the cell cycle at the G₁/S- and G₂/M transitions. This was supported by increased pRB and p27^Kip1 phosphorylation. Induction of apoptosis with time-dependent signalling involving the p-JNK, Erk1/2 and Akt/mTOR pathways and loss of mitochondrial membrane potential was demonstrated. Inhibition of autophagy attenuated the apoptotic response. In conclusion, the 2-ME analogues induced a time-dependent cross-talk between cell cycle checkpoints, apoptotic signalling and autophagic processes, with an increased reactive oxygen species formation and perturbated microtubule functioning appearing to connect the processes. Subtle differences in the responses were observed between the two compounds and the different cell lines.

Serine-70 phosphorylated Bcl-2 prevents oxidative stress-induced DNA damage by modulating the mitochondrial redox metabolism

Bcl-2 phosphorylation at serine-70 (S70pBcl2) confers resistance against drug-induced apoptosis. Nevertheless, its specific mechanism in driving drug-resistance remains unclear. We present evidence that S70pBcl2 promotes cancer cell survival by acting as a redox sensor and modulator to prevent oxidative stress-induced DNA damage and execution. Increased S70pBcl2 levels are inversely correlated with DNA damage in chronic lymphocytic leukemia (CLL) and lymphoma patient-derived primary cells as well as in reactive oxygen species (ROS)- or chemotherapeutic drug-treated cell lines. Bioinformatic analyses suggest that S70pBcl2 is associated with lower median overall survival in lymphoma patients. Empirically, sustained expression of the redox-sensitive S70pBcl2 prevents oxidative stress-induced DNA damage and cell death by suppressing mitochondrial ROS production. Using cell lines and lymphoma primary cells, we further demonstrate that S70pBcl2 reduces the interaction of Bcl-2 with the mitochondrial complex-IV subunit-5A, thereby reducing mitochondrial complex-IV activity, respiration and ROS production. Notably, targeting S70pBcl2 with the phosphatase activator, FTY720, is accompanied by an enhanced drug-induced DNA damage and cell death in CLL primary cells. Collectively, we provide a novel facet of the anti-apoptotic Bcl-2 by demonstrating that its phosphorylation at serine-70 functions as a redox sensor to prevent drug-induced oxidative stress-mediated DNA damage and execution with potential therapeutic implications.

Pharmacologic Inhibition of HIF-1α Attenuates Radiation-Induced Pulmonary Fibrosis in a Preclinical Image Guided Radiation Therapy

PURPOSE

Radiation-induced pulmonary fibrosis (RIPF) is a long-term side effect of thoracic radiation therapy. Hypoxia-induced vascular endothelial mesenchymal transition (EndMT) can occur during the development of RIPF. Here, we examined the direct contribution of endothelial HIF-1α (EC-HIF1α) on RIPF.

METHODS AND MATERIALS

An inducible Cre-lox-mediated endothelial Hif1a deletion mouse line was used to evaluate the potential of HIF-1α inhibition to suppress RIPF. To evaluate the effects of a pharmacologic HIF-1α inhibitor on RIPF after image guided radiation therapy (IGRT) for spontaneous lung adenocarcinoma, we generated conditional tdTomato; K-Ras^G12D; and p53 ^flox/flox mice to facilitate tracking of tumor cells expressing tdTomato.

RESULTS

We found that vascular endothelial-specific HIF-1α deletion shortly before radiation therapy inhibited the progression of RIPF along with reduced EndMT, whereas prolonged deletion of endothelial HIF-1α before irradiation did not. Moreover, we revealed that postirradiation treatment with the novel HIF-1α inhibitor, 2-methoxyestradiol (2-ME) could efficiently inhibit RIPF and EndMT. In addition, IGRT using primary mouse models of non-small cell lung cancer showed that combined treatment of 2-ME with ablative high-dose radiation therapy efficiently inhibited RIPF and the growth of both multifocal and single tumors, concomitantly reducing radiation-induced EndMT of normal as well as tumor regions.

CONCLUSION

These results suggest that a negative regulator of HIF-1α-mediated EndMT, such as 2-ME, may serve as a promising inhibitor of RIPF in radiation therapy.

Smart Hydrogels - Synthetic Stimuli-Responsive Antitumor Drug Release Systems

Among modern drug formulations, stimuli-responsive hydrogels also called "smart hydrogels" deserve a special attention. The basic feature of this system is the ability to change their mechanical properties, swelling ability, hydrophilicity, bioactive molecules permeability, etc., influenced by various stimuli, such as temperature, pH, electromagnetic radiation, magnetic field and biological factors. Therefore, stimuli-responsive matrices can be potentially used in tissue engineering, cell cultures and technology of innovative drug delivery systems (DDSs), releasing the active substances under the control of internal or external stimuli. Moreover, smart hydrogels can be used as injectable DDSs, due to gel-sol transition connected with in situ cross-linking process. Innovative smart hydrogel DDSs can be utilized as matrices for targeted therapy, which enhances the effectiveness of tumor chemotherapy and subsequently limits systemic toxicity. External stimulus sensitivity allows remote control over the drug release profile and gel formation. On the other hand, internal factors provide drg accumulation in tumor tissue and reduce the concentration of active drug form in healthy tissue. In this report, we summarise the basic knowledge and chemical strategies for the synthetic smart hydrogel DDSs applied in antitumor therapy.

Modification of DNA structure by reactive nitrogen species as a result of 2-methoxyestradiol-induced neuronal nitric oxide synthase uncoupling in metastatic osteosarcoma cells

2-methoxyestradiol (2-ME) is a physiological anticancer compound, metabolite of 17β-estradiol. Previously, our group evidenced that from mechanistic point of view one of anticancer mechanisms of action of 2-ME is specific induction and nuclear hijacking of neuronal nitric oxide synthase (nNOS), resulting in local generation of nitro-oxidative stress and finally, cancer cell death.

The current study aims to establish the substantial mechanism of generation of reactive nitrogen species by 2-ME. We further achieved to identify the specific reactive nitrogen species involved in DNA-damaging mechanism of 2-ME.

The study was performed using metastatic osteosarcoma 143B cells. We detected the release of biologically active (free) nitric oxide (^•NO) with concurrent measurements of peroxynitrite (ONOO⁻) in real time in a single cell of 143B cell line by using ^•NO/ONOO⁻ sensitive microsensors after stimulation with calcium ionophore. Detection of nitrogen dioxide (^•NO₂) and determination of chemical rate constants were carried out by a stopped-flow technique. The affinity of reactive nitrogen species toward the guanine base of DNA was evaluated by density functional theory calculations. Expression and localization of nuclear factor NF-kB was determined using imaging cytometry, while cell viability assay was evaluated by MTT assay.

Herein, we presented that 2-ME triggers pro-apoptotic signalling cascade by increasing cellular reactive nitrogen species overproduction – a result of enzymatic uncoupling of increased nNOS protein levels. In particular, we proved that ONOO⁻ and ^•NO₂ directly formed from peroxynitrous acid (ONOOH) and/or by auto-oxidation of ^•NO, are inducers of DNA damage in anticancer mechanism of 2-ME. Specifically, the affinity of reactive nitrogen species toward the guanine base of DNA, evaluated by density functional theory calculations, decreased in the order: ONOOH > ONOO⁻ > ^•NO₂ > ^•NO.

Therefore, we propose to consider the specific inducers of nNOS as an effective tool in the field of chemotherapy.

2-Methoxyestradiol inhibits high fat diet-induced obesity in rats through modulation of adipose tissue macrophage infiltration and immunophenotype

Recently, experimental studies demonstrated that 2-methoxyestradiol (2ME2) ameliorates high fat diet (HFD)-induced obesity and restores insulin sensitivity. However, the mechanisms underlying these effects are unveiled yet. The current study was undertaken to test the hypothesis that 2ME2 exerts its effects by modulating adipose tissue macrophages (ATMs) accumulation, polarization and immunophenotypes. The experiment was carried out in males Wistar rats (n = 28) for 13 consecutive weeks. In HFD-fed group; body weight, glucose intolerance, serum insulin, HOMA-IR, lipid profile and adipose tissue (AT) weight were significantly higher compared to normal standard diet (NSD)- fed rats. However, treatment of HFD-fed rats with 2ME2 (200 μg/kg/day; i.p. from the beginning of the 9th week) resulted in significant enhancements in all these parameters as compared to HFD-fed rats. Treatment with 2ME2 was associated with a significant reduction in macrophage infiltration in the AT, shifting macrophage polarization towards M2 phenotype as indicated by significant decrease in the expression of pro-inflammatory M1 macrophages markers (IL-6, IL-1β, CD11c and iNOS) and concurrent significant increase in the M2 anti-inflammatory macrophage markers (Arginase 1 and IL-10). 2ME2 ameliorates HFD-induced obesity and glucose intolerance through inhibition of ATM infiltration in AT and shifting macrophage polarization from pro-inflammatory M1 to M2 anti-inflammatory phenotypes.

The Major Heat Shock Proteins, Hsp70 and Hsp90, in 2-Methoxyestradiol-Mediated Osteosarcoma Cell Death Model

2-Methoxyestradiol is one of the natural 17β-estradiol derivatives and a potential novel anticancer agent currently being under evaluation in advanced phases of clinical trials. However, the mechanism of anticancer action of 2-methoxyestradiol has not been yet fully established. In our previous studies we have demonstrated that 2-methoxyestradiol selectively induces the expression and nuclear translocation of neuronal nitric oxide synthase in osteosarcoma 143B cells. Heat shock proteins (Hsps) are factors involved in the regulation of expression and activity of nitric oxide synthases. Herein, we chose osteosarcoma cell lines differed in metastatic potential, metastatic 143B and highly metastatic MG63.2 cells, in order to further investigate the anticancer mechanism of 2-methoxyestradiol. The current study aimed to determine the role of major heat shock proteins, Hsp90 and Hsp70 in 2-methoxyestradiol-induced osteosarcoma cell death. We focused on the implication of Hsp90 and Hsp70 in control under expression of neuronal nitric oxide synthase, localization of the enzyme, and further generation of nitro-oxidative stress. To give the insight into the role of Hsp90 in regulation of anticancer efficacy of 2-methoxyestradiol, we used geldanamycin as a potent Hsp90 inhibitor. Herein, we evidenced that inhibition of Hsp90 controls the protein expression of 2-methoxyestradiol-induced neuronal nitric oxide synthase and inhibits enzyme nuclear translocation. We propose that decreased level of neuronal nitric oxide synthase protein after a combined treatment with 2-methoxyestradiol and geldanamycin is directly associated with the accompanying upregulation of Hsp70 and downregulation of Hsp90. This interaction resulted in abrogation of anticancer efficacy of 2-methoxyestradiol by geldanamycin.

A Combination of an Antimitotic and a Bromodomain 4 Inhibitor Synergistically Inhibits the Metastatic MDA-MB-231 Breast Cancer Cell Line

Current chemotherapeutic agents have many side effects and are toxic to normal cells, providing impetus to identify agents that can effectively eliminate tumorigenic cells without damaging healthy cells. The aim of this study was to examine whether combining a novel BRD4 inhibitor, ITH-47, with the antimitotic estradiol analogue, ESE-15-ol, would have a synergistic effect on inhibiting the growth of two different breast cancer cell lines in vitro. Our docking and molecular dynamics studies showed that compared to JQ1, ITH-47 showed a similar binding mode with hydrogen bonds forming between the ligand nitrogens of the pyrazole, ASN99, and water of the BRD4 protein. Data from cell growth studies revealed that the GI₅₀ of ITH-47 and ESE-15-ol after 48 hours of exposure was determined to be 15 μM and 70 nM, respectively, in metastatic MDA-MB-231 breast cancer cells. In tumorigenic MCF-7 breast cancer cells, the GI₅₀ of ITH-47 and ESE-15-ol was 75 μM and 60 nM, respectively, after 48 hours of exposure. Furthermore, the combination of 7.5 μM and 14 nM of ITH-47 and ESE-15-ol, respectively, resulted in 50% growth inhibition of MDA-MB-231 cells resulting in a synergistic combination index (CI) of 0.7. Flow cytometry studies revealed that, compared to the control, combination-treated MDA-MB-231 cells had significantly more cells present in the sub-G₁ phase and the combination treatment induced apoptosis in the MDA-MB-231 cells. Compared to vehicle-treated cells, the combination-treated cells showed decreased levels of the BRD4, as well as c-Myc protein after 48 hours of exposure. In combination, the selective BRD4 inhibitor, ITH-47, and ESE-15-ol synergistically inhibited the growth of MDA-MB-231 breast cancer cells, but not of the MCF-7 cell line. This study provides evidence that resistance to BRD4 inhibitors may be overcome by combining inhibitors with other compounds, which may have treatment potential for hormone-independent breast cancers.

2-Methoxyestradiol and Its Combination with a Natural Compound, Ferulic Acid, Induces Melanoma Cell Death via Downregulation of Hsp60 and Hsp90

Melanoma is an aggressive type of skin cancer with one of the highest mortality rates. Notably, its incidence in the last few decades has increased faster than any other cancer. Therefore, searching for novel anticancer therapies is of great clinical importance. In the present study, we investigated the anticancer potential of 2-methoxyestradiol, potent chemotherapeutic, in the A375 melanoma cellular model. In order to furthermore evaluate the anticancer efficacy of 2-methoxyestradiol, we have additionally combined the treatment with a naturally occurring polyphenol, ferulic acid. The results were obtained using the melanoma A375 cellular model. In the study, we used MTT assay, flow cytometry, and western blot techniques. Herein, we have evidenced that the molecular mechanism of action of 2-methoxyestradiol and ferulic acid is partly related to the reduction of Hsp60 and Hsp90 levels and the induction of nitric oxide in the A375 melanoma cell model, while no changes were observed in Hsp70 expression after 2-methoxyestradiol and ferulic acid treatment separately or in combination. This is especially important in case of chemoresistance mechanisms because the accumulation of Hsp70 reduces induction of cancer cell death, thus decreasing antitumour efficacy.

Nitric oxide and its derivatives in the cancer battlefield

Elevated levels of reactive nitrogen species, alteration in redox balance and deregulated redox signaling are common hallmarks of cancer progression and chemoresistance. However, depending on the cellular context, distinct reactive nitrogen species are also hypothesized to mediate cytotoxic activity and are thus used in anticancer therapies. We present here the dual face of nitric oxide and its derivatives in cancer biology. Main derivatives of nitric oxide, such as nitrogen dioxide and peroxynitrite cause cell death by inducing protein and lipid peroxidation and/or DNA damage. Moreover, they control the activity of important protein players within the pro- and anti-apoptotic signaling pathways. Thus, the control of intracellular reactive nitrogen species may become a sophisticated tool in anticancer strategies.

Pro-apoptotic and anti-angiogenic actions of 2-methoxyestradiol and docosahexaenoic acid, the biologically derived active compounds from flaxseed diet, in preventing ovarian cancer

BACKGROUND

We have previously shown that a whole flaxseed supplemented diet decreased the onset and severity of ovarian cancer in the laying hen, the only known animal model of spontaneous ovarian cancer. Flaxseed is rich in omega-3 fatty acids (OM3FA), mostly α-Linoleic acid (ALA), which gets converted to Docosahexaenoic acid (DHA) by the action of delta-6 desaturase enzyme. Ingestion of flaxseed also causes an increase in production of 2-methoxyestradiol (2MeOE2) via the induction of the CYP1A1 pathway of estrogen metabolism. We have previously reported that the flaxseed diet induces apoptosis via p38-MAPK pathway in chicken tumors. The objective of this study was to investigate the effect of the flaxseed diet on ovarian cancer in chickens, focusing on two hallmarks of cancer, apoptosis and angiogenesis.

RESULTS

The anti-cancer effects of two active biologically derived compounds of flax diet, 2MeOE2 and DHA, were individually tested on human ovarian cancer cells and in vivo by the Chick Chorioallantoic Membrane (CAM) assay. Our results indicate that a flaxseed-supplemented diet promotes apoptosis and inhibits angiogenesis in chicken tumors but not in normal ovaries. 2MeOE2 promotes apoptosis in human ovarian cancer cells, inhibits angiogenesis on CAM and its actions are dependent on the p38-MAPK pathway. DHA does not have any pro-apoptotic effect on human ovarian cancer cells but has strong anti-angiogenic effects as seen on CAM, but not dependent on the p38-MAPK pathway.

CONCLUSIONS

Dietary flaxseed supplementation promotes a pro-apoptotic and anti-angiogenic effect in ovarian tumors, not in normal ovaries. The biologically derived active compounds from flaxseed diet act through different pathways to elicit their respective anti-cancer effects. A flaxseed-supplemented diet is a promising approach for prevention of ovarian cancer as well as having a significant potential as an adjuvant treatment to supplement chemotherapeutic agents for treatment of advanced stages of ovarian cancer.

Novel sulphamoylated 2-methoxy estradiol derivatives inhibit breast cancer migration by disrupting microtubule turnover and organization

BACKGROUND

The estrogen metabolite 2-methoxyestradiol (2ME2) and a number of synthesised derivatives have been shown to bind to microtubules thereby arresting cancer cells in mitosis which leads to apoptosis. In interphase cells, microtubules play an important role in the delivery of proteins to subcellular locations including the focal adhesions. In fact, focal adhesion dynamics and cell migration are in part regulated by microtubules. We hypothesised that novel 2ME2 derivatives can alter cell migration by influencing microtubule dynamics in interphase cells. In this report we describe 2ME2 derivatives that display anti-migratory capabilities in a metastatic breast cancer cell line through their effects on the microtubule network resulting in altered focal adhesion signalling and RhoA activity.

METHODS

Cell migration was assayed using wound healing assays. To eliminate mitosis blockage and cell rounding as a confounding factor cell migration was also assessed in interphase blocked cells. Fluorescence confocal microscopy was used to visualise microtubule dynamics and actin cytoskeleton organisation while western blot analysis was performed to analyse focal adhesion signalling and RhoA activation.

RESULTS

2ME2 derivatives, ESE-one and ESE-15-one, inhibited cell migration in cycling cells as expected but equally diminished migration in cells blocked in interphase. While no significant effects were observed on the actin cytoskeleton, focal adhesion kinase activity was increased while RhoA GTPase activity was inhibited after exposure to either compound. Microtubule stability was increased as evidenced by the increased length and number of detyrosinated microtubules while at the same time clear disorganisation of the normal radial microtubule organisation was observed including multiple foci.

CONCLUSIONS

ESE-15-one and ESE-one are potent migration inhibitors of metastatic breast cancer cells. This ability is coupled to alterations in focal adhesion signalling but more importantly is associated with severe disorganisation of microtubule dynamics and polarity. Therefore, these compounds may offer potential as anti-metastatic therapies.

2-Methoxyestradiol attenuates liver fibrosis in mice: implications for M2 macrophages

Liver fibrosis is a major health problem worldwide due to its serious complications including cirrhosis and liver cancer. 2-Methoxyestradiol (2-ME) is an end metabolite of estradiol with anti-proliferative, antioxidant, and anti-inflammatory activities. However, the protective role of 2-ME in liver fibrosis has not been fully investigated. The aim of this study was to determine the protective effect of 2-ME in carbon tetrachloride (CCl₄)-induced liver fibrosis in mice. Animals were injected intraperitoneally with CCl₄ twice weekly for 6 weeks. 2-ME 50 mg/kg or 100 mg/kg was administrated intraperitoneally every day over the same period. Our data showed that 2-ME reduced the extent of liver toxicity and fibrosis due to CCl₄ exposure. It restored the elevated serum liver enzymes aspartate aminotransferase (AST), alanine aminotransferase (ALT), and alkaline phosphatase (ALP) levels and ameliorated oxidative status. In addition, 2-ME significantly reduced collagen deposition and alpha-smooth muscle actin (α-SMA) protein expressions. Furthermore, 2-ME markedly lowered macrophage infiltration and macrophage alternative activation marker chitinase-like molecules (CHI3L3/YM1). The results of this study indicate an important protective activity of 2-ME in liver fibrosis and highlight the role of macrophage recruitment and alternative activation as a possible target.

A novel non-sulphamoylated 2-methoxyestradiol derivative causes detachment of breast cancer cells by rapid disassembly of focal adhesions

Background

2-Methoxyestradiol (2ME2) is an estradiol metabolite with well documented antiproliferative properties in many cancer cell lines. However, it is rapidly metabolised in vivo which limits its clinical application. Therefore, more stable derivatives with potentially improved clinical features have been designed by our group. Here we describe an estrone-like derivative of 2ME2, namely EE-15-one, that unlike other derivatives which induce cell cycle arrest, induces a rapid loss of cell–substrate adhesion through the inactivation and disassembly of focal adhesions.

Methods

To assess the effect of 2-ethyl-estra-1,3,5 (10),15-tetraen-3-ol-17-one (EE-15-one) on breast cancer cell lines, cell survival was quantified. The effect of EE-15-one on cell attachment was assessed by measuring cell adhesion and cell rounding via light microscopy. Effects on focal adhesion dynamics and actin cytoskeleton organisation were visualised by immunofluorescence while focal adhesion signalling was assessed by western blot. Cell death was quantified using a lactate dehydrogenase activity (LDH) assay. To investigate specificity towards cell–substrate over cell–cell contact inhibition, EE-15-one effects on 3D cell cultures were assessed.

Results

Cell survival assays show an almost complete loss of cells within 24 h of EE-15-one exposure in contrast to published sulphamoylated 2ME2 derivatives. Cell loss is linked to rapid detachment and adhesion inhibition. Focal adhesion size and number are rapidly diminished while actin fibres became severed and disappeared within 2 h post exposure. These changes were not due to cell necrosis as LDH activity only slightly increased after 24 h. Cells grown in cell–cell adhesion dependent spheroids did not respond to EE-15-one exposure suggesting that EE-15-one specifically inhibits cell–substrate adhesions but not cell–cell adhesions and does not directly impact the actin cytoskeleton.

Conclusion

We show that a novel 2ME2 derivative, EE-15-one, induces rapid loss of focal adhesion function leading to cell–substrate detachment through interference with integrin-based cell–substrate adhesions, but not cadherin dependent cell–cell adhesions. Therefore, EE-15-one is the first 2ME2 derivative that has an alternative mode of action to the antimitotic activity of 2ME2. As such EE-15-one shows potential as a lead compound for further development as an inhibitor of cell–substrate adhesion which is essential for metastatic dissemination.

Electronic supplementary material

The online version of this article (10.1186/s12935-018-0688-7) contains supplementary material, which is available to authorized users.

Synthesis of Artemisinin-Estrogen Hybrids Highly Active against HCMV, P. falciparum, and Cervical and Breast Cancer

Artemisinin-estrogen hybrids were for the first time both synthesized and investigated for their in vitro biological activity against malaria parasites (Plasmodium falciparum 3D7), human cytomegalovirus (HCMV), and a panel of human malignant cells of gynecological origin containing breast (MCF7, MDA-MB-231, MDA-MB-361, T47D) and cervical tumor cell lines (HeLa, SiHa, C33A). In terms of antimalarial efficacy, hybrid 8 (EC50 = 3.8 nM) was about two times more active than its parent compound artesunic acid (7) (EC50 = 8.9 nM) as well as the standard drug chloroquine (EC50 = 9.8 nM) and was, therefore, comparable to the clinically used dihydroartemisinin (6) (EC50 = 2.4 nM). Furthermore, hybrids 9-12 showed a strong antiviral effect with EC50 values in the submicromolar range (0.22-0.38 μM) and thus possess profoundly stronger anti-HCMV activity (approximately factor 25) than the parent compound artesunic acid (7) (EC50 = 5.41 μM). These compounds also exerted a higher in vitro anti-HCMV efficacy than ganciclovir used as the standard of current antiviral treatment. In addition, hybrids 8-12 elicited substantially more pronounced growth inhibiting action on all cancer cell lines than their parent compounds and the reference drug cisplatin. The most potent agent, hybrid 12, exhibited submicromolar EC50 values (0.15-0.93 μM) against breast cancer and C33A cell lines.

2-Methoxyestradiol Attenuates Testosterone-Induced Benign Prostate Hyperplasia in Rats through Inhibition of HIF-1α/TGF-β/Smad2 Axis

Benign prostatic hyperplasia (BPH) is a common disorder in the male population. 2-Methoxyestradiol (2ME) is an end metabolite of estrogens with pleiotropic pharmacological properties. This study aimed to explore the potential ameliorative effects of 2ME against testosterone-induced BPH in rats. 2-Methoxyestradiol (50 and 100 mg/kg, dissolved in DMSO) prevented the rise in prostatic index and weight in comparison to testosterone-alone-treated animals for 2 weeks. Histological examination indicated that 2ME ameliorated pathological changes in prostate architecture. This was confirmed by the ability of 2ME to decrease the glandular epithelial height when compared to the testosterone group. Also, 2ME improved testosterone-induced oxidative stress as it inhibited the rise in lipid peroxide content and the exhaustion of superoxide dismutase (SOD) activity. The beneficial effects of 2ME against the development of BPH were substantiated by assessing proliferation markers, preventing the rise in cyclin D1 protein expression and enhancing Bax/Bcl2 mRNA ratio. It significantly reduced prostate content of tumor necrosis factor α (TNF-α), interleukin-1β (IL-1β), nuclear factor κB (NF-κB), and transforming growth factor β (TGF-β). In addition, 2ME reduced hypoxia-inducible factor 1-α (HIF-1α) and phospho-Smad2 (p-Smad2) protein expression compared to the testosterone group. In conclusion, 2ME attenuates experimentally induced BPH by testosterone in rats through, at least partly, inhibition of HIF-1α/TGF-β/Smad2 axis.

Synthesis, molecular modeling and biological evaluation of potent analogs of 2-methoxyestradiol

The endogenous steroid 2-methoxyestradiol (1) has attracted a great interest as a lead compound towards the development of new anti-cancer drugs. Herein, the synthesis, molecular modeling, anti-proliferative and anti-angiogenic effects of ten 2-ethyl and four 2-methoxy analogs of estradiol are reported. The ethyl group was introduced to the steroid A-ring using a novel Friedel-Crafts alkylation protocol. Several analogs displayed potent anti-proliferative activity with IC₅₀-values in the submicromolar range towards the CEM human leukemia cancer cell line. As such, all of these compounds proved to be more active than the lead compound 2-methoxyestradiol (1) in these cells. The six most cytostatic analogs were also tested as anti-angiogenic agents using an in vitro tube formation assay. The IC₅₀-values were determined to be in the range of 0.1 μM ± 0.03 and 1.1 μM ± 0.2. These six compounds were also modest inhibitors against tubulin polymerization with the most potent inhibitor was 14b (IC₅₀ = 2.1 ± 0.1 μM). Binding studies using N,N'-ethylene-bis(iodoacetamide) revealed that neither14a or 14b binds to the colchicine binding site in the tubulin protein, in contrast to 2-methoxyestradiol (1). These observations were supported by molecular modeling studies. Results from a MDA-MB-231 cell cycle assay showed that both 10e and 14b gave accumulation in the G2/M phase resulting in induction of apoptosis. The results presented herein shows that the novel analogs reported exhibit their anticancer effects via several modes of action.

SULFATION PATHWAYS: Steroid sulphatase inhibition via aryl sulphamates: clinical progress, mechanism and future prospects

Steroid sulphatase is an emerging drug target for the endocrine therapy of hormone-dependent diseases, catalysing oestrogen sulphate hydrolysis to oestrogen. Drug discovery, developing the core aryl O-sulphamate pharmacophore, has led to steroidal and non-steroidal drugs entering numerous clinical trials, with promising results in oncology and women's health. Steroidal oestrogen sulphamate derivatives were the first irreversible active-site-directed inhibitors and one was developed clinically as an oral oestradiol pro-drug and for endometriosis applications. This review summarizes work leading to the therapeutic concept of sulphatase inhibition, clinical trials executed to date and new insights into the mechanism of inhibition of steroid sulphatase. To date, the non-steroidal sulphatase inhibitor Irosustat has been evaluated clinically in breast cancer, alone and in combination, in endometrial cancer and in prostate cancer. The versatile core pharmacophore both imbues attractive pharmaceutical properties and functions via three distinct mechanisms of action, as a pro-drug, an enzyme active-site-modifying motif, likely through direct sulphamoyl group transfer, and as a structural component augmenting activity, for example by enhancing interactions at the colchicine binding site of tubulin. Preliminary new structural data on the Pseudomonas aeruginosa arylsulphatase enzyme suggest two possible sulphamate-based adducts with the active site formylglycine as candidates for the inhibition end product via sulphamoyl or sulphonylamine transfer, and a speculative choice is suggested. The clinical status of sulphatase inhibition is surveyed and how it might develop in the future. Also discussed are dual-targeting approaches, development of 2-substituted steroidal sulphamates and non-steroidal derivatives as multi-targeting agents for hormone-independent tumours, with other emerging directions.

The in vitro effects of a novel estradiol analog on cell proliferation and morphology in human epithelial cervical carcinoma

Background

The majority of novel chemotherapeutics target the cell cycle, aiming to effect arrest and cause apoptosis. One such agent, 2-methoxyestradiol (2ME), has been shown to possess anticancer properties against numerous cancer types, both in vitro and in vivo. Despite its promise, 2ME has exhibited limitations, including low oral bioavailability and rapid hepatic enzymatic inactivation in vivo. A novel sulphamoylated estrogen analog, 2-ethyl-3-O-sulphamoyl-estra-1,3,5(10)16-tetraene (ESE-16), was in silico-designed in our laboratory to overcome these issues. It was then synthesized by a pharmaceutical company and used in an in vitro antiproliferative effect study on a human cervical carcinoma (HeLa) cell line.

Results

Cell proliferation data obtained from the crystal violet assay and real-time cell analysis demonstrated that 0.2 μM of ESE-16 had a significant inhibitory effect on the HeLa cells 24 h post-exposure. Immunofluorescence showed that ESE-16 is a microtubule disruptor that causes cells to undergo a mitotic block. Qualitative morphological studies using polarization-optical transmitted light differential interference contrast (PlasDIC) and light microscopy revealed a decrease in cell density and an increase in the number of cells arrested in metaphase. After ESE-16 exposure, hallmarks of apoptosis were also observed, including membrane blebbing, chromatin condensation and the presence of apoptotic bodies. Flow cytometry provided quantitative results from cell cycle progression analysis, indicating cells undergoing apoptosis and cells in the G₂/M phase of the cell cycle, confirming cell cycle arrest in metaphase after ESE-16 treatment. Quantification of the ESE-16-mediated upregulation of cyclin B in HeLa cells and spectrophotometric and flow cytometric confirmation of cell death via apoptosis further confirmed the substance's impact.

Conclusion

ESE-16 exerts its antiproliferative effects through microtubule disruption, which induces a mitotic block culminating in apoptosis. This research provided information on ESE-16 as a potential antitumor agent and on cellular targets that could aid in the design of prospective microtubule-disrupting compounds. Further in vitro and in vivo investigations of this novel compound are needed.

2-Methoxyestradiol protects against pressure overload-induced left ventricular hypertrophy

Numerous experimental studies have supported the evidence that 2-methoxyestradiol (2 ME) is a biologically active metabolite that mediates multiple effects on the cardiovascular system, largely independent of the estrogen receptor. 2 ME is a major cytochrome P450 1B1 (CYP1B1) metabolite and has been reported to have vasoprotective and anti-inflammatory actions. However, whether 2 ME would prevent cardiac hypertrophy induced by abdominal aortic constriction (AAC) has not been investigated yet. Therefore, the overall objectives of the present study were to elucidate the potential antihypertrophic effect of 2 ME and explore the mechanism(s) involved. Our results showed that 2 ME significantly inhibited AAC-induced left ventricular hypertrophy using echocardiography. The antihypertrophic effect of 2 ME was associated with a significant inhibition of CYP1B1 and mid-chain hydroxyeicosatetraenoic acids. Based on proteomics data, the protective effect of 2 ME is linked to the induction of antioxidant and anti-inflammatory proteins in addition to the modulation of proteins involved in myocardial energy metabolism. In vitro, 2 ME has shown a direct antihypertrophic effect through mitogen-activated protein kinases- and nuclear factor-κB-dependent mechanisms. The present work shows a strong evidence that 2 ME protects against left ventricular hypertrophy. Our data suggest the potential of repurposing 2 ME as a selective CYP1B1 inhibitor for the treatment of heart failure.

2-Methoxyestradiol protects against IgG immune complex-induced acute lung injury by blocking NF-κB and CCAAT/enhancer-binding protein β activities

Increasing evidences indicate that 2-Methoxyestradiol (2ME2) plays an essential role in protecting against inflammatory responses. However, its effect on IgG immune complex (IC)-induced acute lung injury (ALI) remains enigmatic. In the study, by using i.p. administration of 2ME2, we evaluated its influence on IgG IC-induced pulmonary injury in mice. We found that during IgG IC-induced ALI, mice treated by 2ME2 displayed a substantial decrease in vascular permeability and neutrophil influx (represented by myeloperoxidase activity) when compared with their counterparts receiving vehicle treatment. Furthermore, 2ME2 treatment significantly decreased pro-inflammatory mediator production and inflammatory cell, especially neutrophil accumulation in bronchoalveolar lavage fluids (BALFs) upon IgG IC stimulation. In vitro, IgG IC-triggered inflammatory mediator production was markedly down-regulated by 2ME2 in macrophages. Moreover, we verified that the activation of the transcription factors, NF-κB and CCAAT/enhancer-binding protein (C/EBP) β, were inhibited by 2ME2 in IgG IC-challenged macrophages. We demonstrated that alleviation of NF-κB-dependent transcription might be associated with reduced phosphorylation of NF-κB p65, and reduction of C/EBP activation was directly linked to its expression. In addition, we discovered that IgG IC-stimulated phosphorylation of both p38 MAPK and ERK1/2 was alleviated by 2ME2. These data indicated a novel strategy for blockade of IgG IC-induced inflammatory activities.

Influence of surface passivation of 2-Methoxyestradiol loaded PLGA nanoparticles on cellular interactions, pharmacokinetics and tumour accumulation

In the present work, 2-Methoxyestradiol [2ME2] loaded PLGA nanoparticles [NPs] were stabilized with Casein or poly(ethylene glycol) [PEG] and evaluated for its cellular interactions, pharmacokinetics and tumour accumulation. Surface stabilized PLGA nanoparticles prepared through a modified emulsion route possessed similar size, surface charge, drug loading and release characteristics. Particle-cell interactions as well as the anti-angiogenesis activity were similar for both nanoformulations in vitro. However, in vivo pharmacokinetics and tumour accumulation of the drug were substantially improved for the PEGylated nanoformulation. Reduced protein binding was observed for PEG stabilized PLGA NPs. Thus, it was demonstrated that nanoencapsulation of 2-ME2 within PEGylated PLGA nanocarrier could improve its half-life and plasma concentration and thereby increase the tumour accumulation.

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.

Recent Advances in chemistry and pharmacology of 2-methoxyestradiol: An anticancer investigational drug

2-Methoxyestradiol (2ME2), an estrogen hormone metabolite is a potential cancer chemotherapeutic agent. Presently, it is an investigational drug under various phases of clinical trials alone or in combination therapy. Its anticancer activity has been attributed to its antitubulin, antiangiogenic, pro-apoptotic and ROS induction properties. This anticancer drug candidate has been explored extensively in last twenty years for its detailed chemistry and pharmacology. Present review is an update of its chemistry and biological activity. It also extends an assessment of potential of 2ME2 and its analogues as possible anticancer drug in future.

2-Methoxyestradiol: A Hormonal Metabolite Modulates Stimulated T-Cells Function and proliferation

BACKGROUND

2-Methoxyestradiol (2ME2) is an endogenous metabolite of estrogen that is nonestrogenic and has been studied in cancer as an antimitotic agent that is beneficial by its selectivity for cancer cells without toxicity to nonmalignant cells. Because the effect of 2ME2 in a transplant rejection setting remains unknown, we hypothesized that 2ME2 can inhibit stimulated T-cell function.

METHODS

Human peripheral blood mononuclear cells (PBMCs) were cultured and pretreated with 2ME2 before stimulation. The cultured medium was collected for enzyme-linked immunosorbent assays, and whole-cell lysates were collected for Western immunoblotting. Proliferation and apoptosis assays were performed and analyzed by means of flow cytometry.

RESULTS

Tumor necrosis factor -α and interferon-γ cytokine production in 2ME2-treated stimulated PBMCs were modestly reduced relative to control samples. T-cell proliferation was blunted by treatment with 2ME2, and a decrease in apoptosis correlated with a decrease in caspase-9 activity. Additionally, 2ME2 was able to block stress-induced senescence caused by stimulation of T-cells.

CONCLUSIONS

2ME2 is a hormone-based therapy that blunts stimulated T-cell proliferation and does not induce apoptosis or stress-induced senescence. Stimulated T-cells treated with 2ME2 are still able to produce normal levels of cytokines. Therefore, 2ME2 may lead to an oral immunomodulatory adjunct therapy with a low side effect profile for individuals undergoing transplantation.

Redox signaling: Potential arbitrator of autophagy and apoptosis in therapeutic response

Redox signaling plays important roles in the regulation of cell death and survival in response to cancer therapy. Autophagy and apoptosis are discrete cellular processes mediated by distinct groups of regulatory and executioner molecules, and both are thought to be cellular responses to various stress conditions including oxidative stress, therefore controlling cell fate. Basic levels of reactive oxygen species (ROS) may function as signals to promote cell proliferation and survival, whereas increase of ROS can induce autophagy and apoptosis by damaging cellular components. Growing evidence in recent years argues for ROS that below detrimental levels acting as intracellular signal transducers that regulate autophagy and apoptosis. ROS-regulated autophagy and apoptosis can cross-talk with each other. However, how redox signaling determines different cell fates by regulating autophagy and apoptosis remains unclear. In this review, we will focus on understanding the delicate molecular mechanism by which autophagy and apoptosis are finely orchestrated by redox signaling and discuss how this understanding can be used to develop strategies for the treatment of cancer.

Effects of 2-methoxyestradiol on apoptosis and HIF-1α and HIF-2α expression in lung cancer cells under normoxia and hypoxia

Hypoxic tumor cells are known to be more resistant to conventional chemotherapy and radiation than normoxic cells. However, the effects of 2-methoxyestradiol (2-ME), an anti-angiogenic, antiproliferative and pro-apoptotic drug, on hypoxic lung cancer cells are unknown. The aim of the present study was to compare the effects of 2-ME on cell growth, apoptosis, hypoxia-inducible factor 1α (HIF-1α) and HIF-2α gene and protein expression in A549 cells under normoxic and hypoxic conditions. To establish the optimal 2-ME concentration with which to carry out the apoptosis assay and to examine mRNA and protein expression of HIFs, cell growth analysis was carried out through N-hexa-methylpararosaniline staining assays in A549 cell cultures treated with one of five different 2-ME concentrations at different times under normoxic or hypoxic growth conditions. The 2-ME concentration of 10 mM at 72 h was selected to perform all further experiments. Apoptotic cells were analyzed by flow cytometry. Western blotting was used to determine HIF-1α and HIF-2α protein expression in total cell extracts. Cellular localization of HIF-1α and HIF-2α was assessed by immunocytochemistry. HIF-1α and HIF-2α gene expression was determined by real-time PCR. A significant increase in the percentage of apoptosis was observed when cells were treated with 2-ME under a normoxic but not under hypoxic conditions (p=0.006). HIF-1α and HIF-2α protein expression levels were significantly decreased in cells cultured under hypoxic conditions and treated with 2-ME (p<0.001). Furthermore, 2-ME decreased the HIF-1α and HIF-2α nuclear staining in cells cultured under hypoxia. The HIF-1α and HIF-2α mRNA levels were significantly lower when cells were exposed to 2-ME under normoxia and hypoxia. Our results suggest that 2-ME could have beneficial results when used with conventional chemotherapy in an attempt to lower the invasive and metastatic processes during cancer development due to its effects on the gene expression and protein synthesis of HIFs.

Inhibition of 2-methoxyestradiol glucuronidation by probenecid

Objectives

2-Methoxyestradiol (2ME2), a metabolite of estradiol, has antitumour activity in vitro. However, potential clinical applicability has been limited by low oral bioavailability. Probenecid was evaluated in vitro as an inhibitor of 2ME2 glucuronidation for purposes of enhancing 2ME2 oral bioavailability.

Methods

Human liver microsomes were used to determine kinetic parameters for transformation of 2ME2 to its glucuronide metabolites (M1, M2) and inhibition of the reactions by probenecid.

Key findings

M1 and M2 formation from 2ME2 proceeded with features of substrate inhibition. Probenecid inhibited metabolite formation, with mean inhibition constant (Ki) values of 0.9 and 2.6 mM, respectively. Inhibition was reversible, with mixed competitive–non-competitive characteristics.

Conclusion

The Ki values for probenecid inhibition of 2ME2 glucuronide formation, when compared to maximum probenecid plasma concentrations anticipated clinically, indicate that probenecid co-administration has the potential to augment systemic plasma levels of 2ME2 after oral dosage in humans.