2-Methoxyestradiol induces apoptosis in Ewing sarcoma cells through mitochondrial hydrogen peroxide production

2-Methoxyestradiol and Hydrogen Peroxide as Promising Biomarkers in Parkinson's Disease

Estrogens function in numerous physiological processes including controlling brain cell growth and differentiation. 2-Methoxestradiol (2-ME2), a 17β-estradiol (E2) metabolite, is known for its anticancer effects as observed both in vivo and in vitro. 2-ME2 affects all actively dividing cells, including neurons. The study aimed to determine whether 2-ME2 is a potentially cancer-protective or rather neurodegenerative agent in a specific tissue culture model as well as a clinical setup. In this study, 2-ME2 activity was determined in a Parkinson's disease (PD) in vitro model based on the neuroblastoma SH-SY5Y cell line. The obtained results suggest that 2-ME2 generates nitro-oxidative stress and controls heat shock proteins (HSP), resulting in DNA strand breakage and apoptosis. On the one hand, it may affect intensely dividing cells preventing cancer development; however, on the other hand, this kind of activity within the central nervous system may promote neurodegenerative diseases like PD. Thus, the translational value of 2-ME2's neurotoxic activity in a PD in vitro model was also investigated. LC-MS/MS technique was used to evaluate estrogens and their derivatives, namely, hydroxy and methoxyestrogens, in PD patients' blood, whereas the stopped-flow method was used to assess hydrogen peroxide (H2O2) levels. Methoxyestrogens and H2O2 levels were increased in patients' blood as compared to control subjects, but hydoxyestrogens were simultaneously decreased. From the above, we suggest that the determination of plasma levels of methoxyestrogens and H2O2 may be a novel PD biomarker. The presented research is the subject of the pending patent application "The use of hydrogen peroxide and 17β-estradiol and its metabolites as biomarkers in the diagnosis of neurodegenerative diseases," no. P.441360.

Methoxychlor induces oxidative stress and impairs early embryonic development in pigs

Introduction: Methoxychlor (MXC) is an organochlorine pesticide (OCP) that was formerly used worldwide as an insecticide against pests and mosquitoes. However, MXC is not biodegradable and has lipophilic characteristics; thus, it accumulates in organisms and affects reproductive function. MXC, as an estrogenic compound, promotes oxidative stress, induces oxidative stress damage to ovarian follicles, and causes miscarriages and stillbirths in females. In this research endeavor, our primary objective was to explore the ramifications of MXC regarding the developmental processes occurring during the initial stages of embryogenesis in pigs. Methods: In this study, we counted the blastocyst rate of early embryos cultured in vitro. We also examined the reactive oxygen species level, glutathione level, mitochondrial membrane potential, mitochondrial copy number and ATP level in four-cell stage embryos. Finally, apoptosis and DNA damage in blastocyst cells, as well as pluripotency-related and apoptosis-related genes in blastocyst cells were detected. The above experiments were used to evaluate the changes of MXC damage on early parthenogenetic embryo development. Results and Discussion: The results showed that early embryos exposed to MXC had a significantly lower cleavage rate, blastocyst rate, hatching rate, and total cell count compared with the control group. It was also of note that MXC not only increased the levels of reactive oxygen species (ROS), but also decreased the mitochondrial membrane potential (ΔΨm) and mitochondrial copy number during the development of early embryos. In addition, after MXC treatment, blastocyst apoptosis and DNA damage were increased, decreased cell proliferation, and the expression of pluripotency-related genes SOX2, NANOG, and OCT4 was down-regulated, while the expression of apoptosis-related genes BAX/BCL-2 and Caspase9 was up-regulated. Our results clearly show that MXC can have deleterious effects on the developmental processes of early porcine embryos, establishing the toxicity of MXC to the reproductive system. In addition, the study of this toxic effect may lead to greater concern about pesticide residues in humans and the use of safer pesticides, thus potentially preventing physiological diseases caused by chemical exposure.

2-Methoxyestradiol Damages DNA in Glioblastoma Cells by Regulating nNOS and Heat Shock Proteins

Gliomas are the most prevalent primary tumors of the central nervous system (CNS), accounting for over fifty percent of all primary intracranial neoplasms. Glioblastoma (GBM) is the most prevalent form of malignant glioma and is often incurable. The main distinguishing trait of GBM is the presence of hypoxic regions accompanied by enhanced angiogenesis. 2-Methoxyestradiol (2-ME) is a well-established antiangiogenic and antiproliferative drug. In current clinical studies, 2-ME, known as Panzem, was examined for breast, ovarian, prostate, and multiple myeloma. The SW1088 grade III glioma cell line was treated with pharmacological and physiological doses of 2-ME. The induction of apoptosis and necrosis, oxidative stress, cell cycle arrest, and mitochondrial membrane potential were established by flow cytometry. Confocal microscopy was used to detect DNA damage. The Western blot technique determined the level of nitric oxide synthase and heat shock proteins. Here, for the first time, 2-ME is shown to induce nitro-oxidative stress with the concomitant modulation of heat shock proteins (HSPs) in the SW1088 grade III glioma cell line. Crucial therapeutic strategies for GMB should address both cell proliferation and angiogenesis, and due to the above, 2-ME seems to be a perfect candidate for GBM therapy.

Bovine Serum Amine Oxidase and Polyamine Analogues: Chemical Synthesis and Biological Evaluation Integrated with Molecular Docking and 3-D QSAR Studies

Natural polyamines (PAs) are key players in cellular homeostasis by regulating cell growth and proliferation. Several observations highlight that PAs are also implicated in pathways regulating cell death. Indeed, the PA accumulation cytotoxic effect, maximized with the use of bovine serum amine oxidase (BSAO) enzyme, represents a valuable strategy against tumor progression. In the present study, along with the design, synthesis, and biological evaluation of a series of new spermine (Spm) analogues (1-23), a mixed structure-based (SB) and ligand-based (LB) protocol was applied. Binding modes of BSAO-PA modeled complexes led to clarify electrostatic and steric features likely affecting the BSAO-PA biochemical kinetics. LB and SB three-dimensional quantitative structure-activity relationship (Py-CoMFA and Py-ComBinE) models were developed by means of the 3d-qsar.com portal, and their analysis represents a strong basis for future design and synthesis of PA BSAO substrates for potential application in oxidative stress-induced chemotherapy.

2-methoxyestradiol inhibits melanoma cell growth by activating adaptive immunity

Background: The overall survival of melanoma patients remains poor despite advancements in surgical treatment and targeted therapies. Therefore, there is a need to develop new therapeutic strategies for melanoma. 2-methoxyestradiol (2-ME) is a major metabolite of estrogen that has been shown to have anti-tumor effects against many malignancies. However, the effects and mechanisms of action of 2-ME against melanoma remain unclear.Materials and methods: Melanoma cells (B16) were treated with 2-ME in vitro. Cell proliferation was detected by CCK8 and clone formation, transwell was carried out to measure the migration of B16 cells with or without 2-ME. Flow cytometry was performed to measure the apoptosis and cell cycle. C57BL/6 mice were used for tumor-bearing of B16 cells, tumor volumes were measured once a day, and sacrificed after it was over 2000 mm3, then immunofluorescence was implemented to examine the marker of CD3, CD8 and PD-L1.Results: In our study, we found that 2-ME significantly affected the proliferation, migration, apoptosis, and cell cycle of melanoma in vitro. Our results also showed that 2-ME had strong anti-tumor effects against melanoma in vivo and increased the infiltration of tumor-specific cytotoxic lymphocytes CD8+ T cells in the tumor microenvironment. Besides, PD-L1 expression in tumor cells was significantly higher in the 2-ME-treated group than in the control group, indicating that 2-ME could exhibit stronger anti-tumor effects against melanoma if combined with PD-1 blockade therapy.Conclusion: 2-ME suppresses melanoma in vivo and in vitro and is a promising synergistic enhancer of PD-1 blockade immunotherapy.

Targeting the redox imbalance in mitochondria: A novel mode for cancer therapy

Changes in reactive oxygen species (ROS) levels affect many aspects of cell behavior. During carcinogenesis, moderate ROS production modifies gene expression to alter cell function, elevating metabolic activity and ROS. To avoid extreme ROS-activated death, cancer cells increase antioxidative capacity, regulating sustained ROS levels that promote growth. Anticancer therapies are exploring inducing supranormal, cytotoxic oxidative stress levels either inhibiting antioxidative capacity or promoting excess ROS to selectively destroy cancer cells, triggering mechanisms such as apoptosis, autophagy, necrosis, or ferroptosis. This review exemplifies pro-oxidants (natural/synthetic/repurposed drugs) and their clinical significance as cancer therapies providing revolutionary approaches.

Construction of homologous cancer cell membrane camouflage in a nano-drug delivery system for the treatment of lymphoma

BACKGROUND

Non-Hodgkin's lymphoma (NHL) possesses great heterogeneity in cytogenetics, immunophenotype and clinical features, and chemotherapy currently serves as the main treatment modality. Although employing monoclonal antibody targeted drugs has significantly improved its overall efficacy, various patients continue to suffer from drug resistance or recurrence. Chinese medicine has long been used in the treatment of malignant tumors. Therefore, we constructed a low pH value sensitivity drug delivery system based on the cancer cell membrane modified mesoporous silica nanoparticles loaded with traditional Chinese medicine, which can reduce systemic toxicity and improve the therapeutic effect for the targeted drug delivery of tumor cells.

RESULTS

Accordingly, this study put forward the construction of a nano-platform based on mesoporous silica nanoparticles (MSNs) loaded with the traditional Chinese medicine isoimperatorin (ISOIM), which was camouflaged by the cancer cell membrane (CCM) called CCM@MSNs-ISOIM. The proposed nano-platform has characteristics of immune escape, anti-phagocytosis, high drug loading rate, low pH value sensitivity, good biocompatibility and active targeting of the tumor site, blocking the lymphoma cell cycle and promoting mitochondrial-mediated apoptosis.

CONCLUSIONS

Furthermore, this study provides a theoretical basis in finding novel clinical treatments for lymphoma.

Free Radicals as a Double-Edged Sword: The Cancer Preventive and Therapeutic Roles of Curcumin

Free radicals, generally composed of reactive oxygen species (ROS) and reactive nitrogen species (RNS), are generated in the body by various endogenous and exogenous systems. The overproduction of free radicals is known to cause several chronic diseases including cancer. However, increased production of free radicals by chemotherapeutic drugs is also associated with apoptosis in cancer cells, indicating the dual nature of free radicals. Among various natural compounds, curcumin manifests as an antioxidant in normal cells that helps in the prevention of carcinogenesis. It also acts as a prooxidant in cancer cells and is associated with inducing apoptosis. Curcumin quenches free radicals, induces antioxidant enzymes (catalase, superoxide dismutase, glutathione peroxidase), and upregulates antioxidative protein markers-Nrf2 and HO-1 that lead to the suppression of cellular oxidative stress. In cancer cells, curcumin aggressively increases ROS that results in DNA damage and subsequently cancer cell death. It also sensitizes drug-resistant cancer cells and increases the anticancer effects of chemotherapeutic drugs. Thus, curcumin shows beneficial effects in prevention, treatment and chemosensitization of cancer cells. In this review, we will discuss the dual role of free radicals as well as the chemopreventive and chemotherapeutic effects of curcumin and its analogues against cancer.

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.

Understanding of ROS-Inducing Strategy in Anticancer Therapy

Redox homeostasis is essential for the maintenance of diverse cellular processes. Cancer cells have higher levels of reactive oxygen species (ROS) than normal cells as a result of hypermetabolism, but the redox balance is maintained in cancer cells due to their marked antioxidant capacity. Recently, anticancer therapies that induce oxidative stress by increasing ROS and/or inhibiting antioxidant processes have received significant attention. The acceleration of accumulative ROS disrupts redox homeostasis and causes severe damage in cancer cells. In this review, we describe ROS-inducing cancer therapy and the anticancer mechanism employed by prooxidative agents. To understand the comprehensive biological response to certain prooxidative anticancer drugs such as 2-methoxyestradiol, buthionine sulfoximine, cisplatin, doxorubicin, imexon, and motexafin gadolinium, we propose and visualize the drug-gene, drug-cell process, and drug-disease interactions involved in oxidative stress induction and antioxidant process inhibition as well as specific side effects of these drugs using pathway analysis with a big data-based text-mining approach. Our review will be helpful to improve the therapeutic effects of anticancer drugs by providing information about biological changes that occur in response to prooxidants. For future directions, there is still a need for pharmacogenomic studies on prooxidative agents as well as the molecular mechanisms underlying the effects of the prooxidants and/or antioxidant-inhibitor agents for effective anticancer therapy through selective killing of cancer cells.

Molecular modelling predicts that 2-methoxyestradiol disrupts HIF function by binding to the PAS-B domain

An estradiol metabolite, 2-methoxyestradiol (2ME), has emerged as an important regulator of ovarian physiology. 2ME is recognized as a potent anti-angiogenic agent in clinical trials and laboratory studies. However, little is known about its molecular actions and its endogenous targets. 2ME is produced by human ovarian cells during the normal menstrual cycle, being higher during regression of the corpus luteum, and is postulated to be involved in the anti-angiogenic process that plays out during luteolysis. We utilized cell biology techniques to understand the molecular mechanism of 2ME anti-angiogenic effects on human granulosa luteal cells. The principal effect of 2ME was to alter Hypoxia Inducible Factor 1A (HIF1A) sub-cellular localization. Molecular modelling and multiple bioinformatics tools indicated that 2ME impairs Hypoxia Inducible Factor complex (HIF) nuclear translocation by binding to a buried pocket in the HIF1A Per Arnt Sim (PAS)-B domain. Binding of 2ME to HIF1A protein is predicted to perturb HIF1A-Hypoxia Inducible Factor B (HIFB) interaction, a key step in HIF nuclear translocation, preventing the transcriptional actions of HIF, including Vascular Endotelial Growth Factor (VEGF) gene activation. To our knowledge, 2ME is the first putative HIF endogenous ligand characterized with anti-angiogenic activity. This postulate has important implications for reproduction, because angiogenic processes are critical for ovarian follicular development, ovulation and corpus luteum regression. The present research could contribute to the development of novel pharmacological approaches for controlling HIF activity in human reproductive diseases.

The Specific Vulnerabilities of Cancer Cells to the Cold Atmospheric Plasma-Stimulated Solutions

Cold atmospheric plasma (CAP), a novel promising anti-cancer modality, has shown its selective anti-cancer capacity on dozens of cancer cell lines in vitro and on subcutaneous xenograft tumors in mice. Over the past five years, the CAP-stimulated solutions (PSS) have also shown their selective anti-cancer effect over different cancers in vitro and in vivo. The solutions used to make PSS include several bio-adaptable solutions, mainly cell culture medium and simple buffered solutions. Both the CAP-stimulated medium (PSM) and the CAP-stimulated buffered solution (PSB) are able to significantly kill cancer cells in vitro. In this study, we systematically compared the anti-cancer effect of PSM and PSB over pancreatic adenocarcinoma cells and glioblastoma cells. We demonstrated that pancreatic cancer cells and glioblastoma cells were specifically vulnerable to PSM and PSB, respectively. The specific response such as the rise of intracellular reactive oxygen species of two cancer cell lines to the H₂O₂-containing environments might result in the specific vulnerabilities to PSM and PSB. In addition, we demonstrated a basic guideline that the toxicity of PSS on cancer cells could be significantly modulated through controlling the dilutability of solution.

A bis-sulphamoylated estradiol derivative induces ROS-dependent cell cycle abnormalities and subsequent apoptosis

Clinical trials have revealed that the potential anticancer agent, 2-methoxyestradiol (2ME2) has limitations due to its low bioavailability. Subsequently, 2ME2 derivatives including (8R,13S,14S,17S)-2-ethyl-13-methyl-7,8,9,11,12,13,14,15,16,17-decahydro-6H-cyclopenta[a]phenanthrane-3,17-diyl bis(sulphamate) (EMBS) have shown improved efficacies in inducing apoptosis. However, no conclusive data exist to explain the mode of action exerted by these drugs. This study investigated the mode of action used by EMBS as a representative of the sulphamoylated 2ME2 derivatives. Hydrogen peroxide and superoxide production was quantified using dichlorofluorescein diacetate and hydroethidine. Cell proliferation and mitochondrial metabolism were investigated using crystal violet and Alamar Blue. Apoptosis was assessed using Annexin V-FITC while mitochondrial integrity was assessed using Mitocapture. Autophagy was visualised using LC3B II antibodies. The effects of EMBS on H2A phosphorylation and nuclei were visualised using phospho H2A antibody and 4',6-diamidino-2-phenylindole, dihydrochloride. Data showed that EMBS exposure leads to increased reactive oxygen species (ROS) production which is correlated with loss of cell proliferation, mitochondrial membrane damage, decreased metabolic activity, G2/M arrest, endoreduplication, DNA double stranded breaks, micronuclei and apoptosis induction. Treatment of EMBS-exposed cells with the ROS scavenger, N-acetyl cysteine, abrogated ROS production, cell cycle arrest and apoptosis implying an essential role for ROS production in EMBS signaling. The inhibition of c-Jun N-terminal kinase (JNK) activity also inhibited EMBS-induced apoptosis suggesting that EMBS triggers apoptosis via the JNK pathway. Lastly, evaluation of LC3IIB protein levels indicated that autophagy is not activated in EMBS-exposed cells. Our data shows that EMBS targets a pathway that leads to increased ROS production as an early event that culminates in G2/M arrest and apoptosis by means of JNK-signaling in cancer cells. This study suggests a novel oxidative stress-dependent mode of action for sulphamoylated derivatives.

Neuronal Nitric Oxide Synthase-Mediated Genotoxicity of 2-Methoxyestradiol in Hippocampal HT22 Cell Line

2-methoxyestradiol, metabolite of 17β-estradiol, is considered a potential anticancer agent, currently investigated in several clinical trials. This natural compound was found to be effective towards great number of cancers, including colon, breast, lung, and osteosarcoma and has been reported to be relatively non-toxic towards non-malignant cells. The aim of the study was to determine the potential neurotoxicity and genotoxicity of 2-methoxyestradiol at physiological and pharmacological relevant concentrations in hippocampal HT22 cell line. Herein, we determined influence of 2-methoxyestradiol on proliferation, inhibition of cell cycle, induction of apoptosis, and DNA damage in the HT22 cells. The study was performed using imaging cytometry and comet assay techniques. Herein, we demonstrated that 2-methoxyestradiol, at pharmacologically and also physiologically relevant concentrations, increases nuclear localization of neuronal nitric oxide synthase. It potentially results in DNA strand breaks and increases in genomic instability in hippocampal HT22 cell line. Thus, we are postulating that naturally occurring 2-methoxyestradiol may be considered a physiological modulator of neuron survival.

DNA strand breaks induced by nuclear hijacking of neuronal NOS as an anti-cancer effect of 2-methoxyestradiol

2-Methoxyestradiol (2-ME) is a physiological metabolite of 17β-estradiol. At pharmacological concentrations, 2-ME inhibits colon, breast and lung cancer in tumor models. Here we investigated the effect of physiologically relevant concentrations of 2-ME in osteosarcoma cell model. We demonstrated that 2-ME increased nuclear localization of neuronal nitric oxide synthase, resulting in nitro-oxidative DNA damage. This in turn caused cell cycle arrest and apoptosis in osteosarcoma cells. We suggest that 2-ME is a naturally occurring hormone with potential anti-cancer properties.

The effects of bioactive compounds from plant foods on mitochondrial function: a focus on apoptotic mechanisms

Mitochondria are essential organelles for cellular integrity and functionality maintenance and their imparement is implicated in the development of a wide range of diseases, including metabolic, cardiovascular, degenerative and hyperproliferative pathologies. The identification of different compounds able to interact with mitochondria for therapeutic purposes is currently becoming of primary importance. Indeed, it is well known that foods, particularly those of vegetable origin, present several constituents with beneficial effects on health. This review summarizes and updates the most recent findings concerning the mechanisms through which different dietary compounds from plant foods affect mitochondria functionality in healthy and pathological in vitro and in vivo models, paying particular attention to the pathways involved in mitochondrial biogenesis and apoptosis.

Molecular mechanism of 17α-ethinylestradiol cytotoxicity in isolated rat hepatocytes

17α-Ethinylestradiol (17-EE) is used in formulations of contraceptives and hormone replacement therapy because it is an estradiol derivative. However, it has been associated with an increase in the risk of liver cancers and injury. The carcinogenic properties of 17-EE are similar to that of other estrogens, but the molecular mechanism of liver injury is still unclear. It is important to identify any secondary toxic mechanisms that can be used to prevent or treat the toxicity. The LC50 of 17-EE toward isolated rat hepatocytes was determined to be 150 ± 8 μmol/L. Accelerated cytotoxicity mechanism screening (ACMS) techniques using isolated rat hepatocytes showed that CYP1A inhibitors decreased cytotoxicity, whereas tyrosinase increased toxicity; this suggests that the toxic mechanism involved is the oxidation of 17-EE. A hepatocyte inflammation model also increased 17-EE-induced mitochondrial toxicity, as well as the formation of ROS and H2O2. Cytotoxicity was increased when inhibitors of quinone reduction, catechol-O-methylation, glucuronidation, glutathione conjugation, and sulfation were co-incubated with 17-EE. The hepatocytes could be rescued with antioxidants and quinone trapping agents, thereby suggesting a role for quinoid moiety induced oxidative stress in 17-EE induced cytotoxicity. These mechanisms for 17-EE hepatotoxicity could provide a new perspective for the treating 17-EE-induced liver injury.

Combination treatment with 2-methoxyestradiol overcomes bortezomib resistance of multiple myeloma cells

Bortezomib is a proteasome inhibitor used for the treatment of relapsed/refractory multiple myeloma (MM). However, intrinsic and acquired resistance to bortezomib has already been observed in MM patients. In a previous report, we demonstrated that changes in the expression of mitochondrial genes lead to changes in mitochondrial activity and bortezomib susceptibility or resistance, and their combined effects contribute to the differential sensitivity or resistance of MM cells to bortezomib. Here we report that the combination treatment of bortezomib and 2-methoxyestradiol (2ME), a natural estrogen metabolite, induces mitochondria-mediated apoptotic cell death of bortezomib-resistant MM KMS20 cells via mitochondrial reactive oxygen species (ROS) overproduction. Bortezomib plus 2ME treatment induces a higher level of cell death compared with treatment with bortezomib alone and increases mitochondrial ROS and Ca(2+) levels in KMS20 cells. Pretreatment with the antioxidant N-acetyl-L-cysteine scavenges mitochondrial ROS and decreases cell death after treatment with bortezomib plus 2ME in KMS20 cells. Moreover, we observed that treatment with bortezomib plus 2ME maintains the activation of c-Jun N-terminal kinase (JNK) and mitogen-activated protein kinase kinase kinase 4/7 (MKK4/7). Collectively, combination treatment with bortezomib and 2ME induces cell death via JNK-MKK4/7 activation by overproduction of mitochondrial ROS. Therefore, combination therapy with specific mitochondrial-targeting drugs may prove useful to the development of novel strategies for the treatment of bortezomib-resistant MM patients.

Antiproliferative effect of H2O2 against human acute myelogenous leukemia KG1 cell line

It has clearly been established that oxidative stress leads to perturbation of various cellular processes resulting in either inhibition of cell proliferation or cell death. In addition, there is a growing body of evidence indicating that reactive oxygen species (ROS) are required as signal molecules that regulate different physiological processes including survival or death. Free radicals, particularly ROS, have been proposed as general mediators for apoptosis and recent studies have established that the mode of cell death depends on the severity of the oxidative damage. In this study, we determined the effect of oxidative stress on cell proliferation and characterization of cell death in human KG1 cells treated with H2O2. Our results indicated that oxidative stress leads to a significant decrease in cell proliferation and induction of apoptosis. Moreover, our study suggests that antiproliferative and apoptotic cell death effects of H2O2 took place via activation of caspase-3, affecting the expression of Bcl-2 and Bax (an antiapoptotic and a proapoptotic factor, respectively), and through deactivation of catalase enzyme, leading to accumulation of intracellular ROS and depletion of intracellular ATP level.

Factors Affecting EWS-FLI1 Activity in Ewing's Sarcoma

Ewing's sarcoma family tumors (ESFT) are characterized by specific chromosomal translocations, which give rise to EWS-ETS chimeric proteins. These aberrant transcription factors are the main pathogenic drivers of ESFT. Elucidation of the factors influencing EWS-ETS expression and/or activity will guide the development of novel therapeutic agents against this fatal disease.

Involvement of reactive oxygen species in 2-methoxyestradiol-induced apoptosis in human neuroblastoma cells

Neuroblastoma is the most common extra-cranial solid tumor in children. Despite advances in the treatment of childhood cancer, outcomes for children with advanced-stage neuroblastoma remain poor. Here we reported that 2-methoxyestradiol (2-ME) inhibited the proliferation and induced apoptosis in human neuroblastoma SK-N-SH and SH-SY5Y cells. 2-ME treatment also resulted in the generation of ROS and the loss of mitochondrial membrane potential in SK-N-SH and SH-SY5Y, indicating that 2-ME-induced apoptosis is mediated by ROS. This is supported by the results that have shown that co-treatment with antioxidants, VC, L-GSH and MitoQ(10), decreased 2-ME-induced generation of ROS and the loss of the mitochondrial membrane potential, increased the Bcl-2/Bax ratio, decreased 2-ME-induced activation of caspase-9 and caspase-3 and the up-regulation of apoptosis-inducing factor (AIF), and prevented 2-ME-induced apoptosis in SK-N-SH and SH-SY5Y cells. These results suggested that oxidative stress plays an important role in 2-ME-induced apoptotic death of human neuroblastoma cells.

Oxidative stress and therapeutic opportunities: focus on the Ewing's sarcoma family of tumors

Reactive oxygen species (ROS) are highly reactive by-products of energy production that can have detrimental as well as beneficial effects. Unchecked, high levels of ROS result in an imbalance of cellular redox state and oxidative stress. High levels of ROS have been detected in most cancers, where they promote tumor development and progression. Many anticancer agents work by further increasing cellular levels of ROS, to overcome the antioxidant detoxification capacity of the cancer cell and induce cell death. However, adaptation of the level of cellular antioxidants can lead to drug resistance. The challenge for the design of effective cancer therapeutics exploiting oxidative stress is to tip the cellular redox balance to induce ROS-dependent cell death but without increasing the antioxidant activity of the cancer cell or inducing toxicity in normal cells.

2-Methoxyestradiol blocks cell-cycle progression at the G2/M phase and induces apoptosis in human acute T lymphoblastic leukemia CEM cells

2-Methoxyestradiol (2-ME2) is an endogenous metabolite of 17beta-estradiol (E2) with estrogen receptor-independent anti-cancer activity. The current study sought to determine the mechanism of anti-cancer activity of 2-ME2 in human acute T lymphoblastic leukemia CEM cells. Results showed that 2-ME2 markedly suppressed proliferation of CEM cells in a time- and dose-dependent manner. 2-ME2-treated CEM cells underwent typical apoptotic changes. Exposure to 2-ME2 led to G(2)/M phase cell-cycle arrest, which preceded apoptosis characterized by the appearance of a sub-G(1) cell population. In addition, cytosolic cytochrome c release, increased procaspase-9 and -3 expressions, poly(ADP-ribose) polymerase (PARP) cleavage, and induced expression of caspase-8 were detected, suggesting that both the intrinsic apoptotic pathway and extrinsic apoptotic pathway were involved in 2-ME2-induced apoptosis. Moreover, the expression level of p21 protein was upregulated, whereas Bcl-2 and dysfunctional p53 protein were downregulated, which also contributed to 2-ME2-induced apoptosis. Our findings revealed that 2-ME2 might be a potent natural candidate for chemotherapeutic treatment of human acute T lymphoblastic leukemia when the precise effects of 2-ME2 were investigated further in other T leukemia cell lines and in primary T-cell leukemias.

Apoptosis induced by emodin is associated with alterations of intracellular acidification and reactive oxygen species in EC-109 cells

Emodin (1,3,8-trihydroxy-6-methylanthraquinone), a natural anthraquinone derivative found in several herbal medicines, is highly active in suppressing the proliferation of various tumor cells such as breast, hepatocellular, and lung cancer cells under in vitro conditions. The mechanism of emodin-induced apoptosis in esophagus carcinoma cells, EC-109, is not completely understood. In this study, EC-109 cells treated with emodin underwent rapid apoptosis as judged by morphological changes and flow cytometry analysis. The addition of emodin to EC-109 cells led to the inhibition of growth in a time- and dose-dependent manner. Fluorescence measurements of cells indicated that the intracellular pH (pHi) decreased significantly by 0.47-0.78 units. The results obtained from flow cytometry suggested that bursts of reactive oxygen species took place after the application of emodin. The present study indicates that emodin may be a strong anticancer drug against esophagus cancer cells by causing various early events leading to growth inhibition, including the production of reactive oxygen species and decrease of pHi, which may result in cellular apoptosis.

In vitro effects of 2-methoxyestradiol on morphology, cell cycle progression, cell death and gene expression changes in the tumorigenic MCF-7 breast epithelial cell line

In the present study, the antiproliferative mechanism of action of 1 microM 2-methoxyestradiol (2ME) was investigated in the MCF-7 cell line. Measurement of intracellular cyclin B and cytochrome c protein levels, reactive oxygen species formation, cell cycle progression and apoptosis induction were conducted by means of flow cytometry. Morphological changes were evaluated using transmission electron microscopy and fluorescent microscopy by employing Hoechst 33342 and acridine orange. Gene expression changes were conducted by means of microarrays. 2ME-treated cells demonstrated an increase in cyclin B protein levels, hydrogen peroxide formation, intracellular levels of cytochrome c, as well as an increase in early and late stages of apoptosis. In addition, morphological data revealed the presence of autophagic processes. Fluorescent microscopy showed an increase in acridine orange staining and electron microscopy revealed an increase in vacuolar formation in 2ME-treated cells. The gene expression of several genes associated with mRNA translation, autophagy-related processes and genes involved in microtubule dynamics were affected. The study contributes to the mechanistic understanding of 2ME's growth inhibition in MCF-7 cells and highlights the possibility of both apoptotic and autophagic processes being activated in response to 2ME treatment in this cell line.

Quercetin induces oxidative stress and potentiates the apoptotic action of 2-methoxyestradiol in human hepatoma cells

Hepatocellular carcinoma (HCC) is the leading cause of cancer mortality in Asia. This study evaluated the growth inhibition effect of quercetin and 2-methoxyestradiol in vitro in human HCC cell lines. Combination treatment enhanced the cytotoxic effect in HA22T/VGH and HepG2 cell lines as compared with quercetin or 2-methoxyestradiol alone. The cell population of sub-G0/G1 phase and the level of annexin V binding were increased synergistically after combination treatment with quercetin and 2-methoxyestradiol in both cell lines. Moreover, quercetin combined with 2-methoxyestradiol increased superoxide levels, mitochondrial superoxide dismutase (MnSOD) in mRNA, protein levels, and SOD activity. Finally, we also found the mitochondrial membrane potential was decreased after combination treatment. The changes of reactive oxygen species and mitochondrial disruption were likely to be involved in the mechanism for the synergistic cytotoxicity effects of combination treatment in human hepatoma cells. These results provided a basis for further study of the potential usage of quercetin combination with hormonal agents for the treatment of human hepatoma.

Structure activity analysis of 2-methoxyestradiol analogues reveals targeting of microtubules as the major mechanism of antiproliferative and proapoptotic activity

2-Methoxyestradiol (2ME2) is an anticancer agent with antiproliferative, antiangiogenic, and proapoptotic effects. A major proposed mechanism of drug action is the disruption of the microtubule skeleton, leading to the induction of cell cycle arrest and apoptosis. In addition, other mechanisms of action have been proposed, including the generation of reactive oxygen species (ROS), inhibition of hypoxia-inducible factor (HIF), and interference with mitochondrial function. In this study, we used a selection of 2ME2 analogues to conduct structure activity analysis and correlated the antiproliferative and proapoptotic activity of the various analogues with their effects on different drug targets. A good correlation was observed between drug activity and effects on microtubule function. In contrast, our results indicate that effects on ROS, HIF, and mitochondria are unlikely to contribute significantly to the cellular activity of 2ME2. Thus, our data indicate that the structural requirements for inducing ROS and inhibition of complex I of the mitochondrial electron transport chain were different from those required for proapoptotic drug activity. Furthermore, antioxidant treatment or overexpression of catalase did not inhibit the cellular activity of 2ME2 in epithelial cancer cells. Inhibition of HIF required much higher concentrations of 2ME2 analogues compared with concentrations that inhibited cell proliferation and induced apoptosis. Our results thus provide a better insight into the mechanism of action of 2ME2 and reveal structural requirements that confer high cellular activity, which may aid future drug development.

A new view of carcinogenesis and an alternative approach to cancer therapy

During the last few decades, cancer research has focused on the idea that cancer is caused by genetic alterations and that this disease can be treated by reversing or targeting these alterations. The small variations in cancer mortality observed during the previous 30 years indicate, however, that the clinical applications of this approach have been very limited so far. The development of future gene-based therapies that may have a major impact on cancer mortality may be compromised by the high number and variability of genetic alterations recently found in human tumors. This article reviews evidence that tumor cells, in addition to acquiring a complex array of genetic changes, develop an alteration in the metabolism of oxygen. Although both changes play an essential role in carcinogenesis, the altered oxygen metabolism of cancer cells is not subject to the high genetic variability of tumors and may therefore be a more reliable target for cancer therapy. The utility of this novel approach for the development of therapies that selectively target tumor cells is discussed.

c-Jun NH2-terminal kinase activation is essential for DRAM-dependent induction of autophagy and apoptosis in 2-methoxyestradiol-treated Ewing sarcoma cells

Ewing sarcoma and osteosarcoma are two aggressive cancers that affect bones and soft tissues in children and adolescents. Despite multimodal therapy, patients with metastatic sarcoma have a poor prognosis, emphasizing a need for more effective treatment. We have shown previously that 2-methoxyestradiol (2-ME), an antitumoral compound, induces apoptosis in Ewing sarcoma cells through c-Jun NH(2)-terminal kinase (JNK) activation. In the present study, we provide evidence that 2-ME elicits macroautophagy, a process that participates in apoptotic responses, in a JNK-dependent manner, in Ewing sarcoma and osteosarcoma cells. We also found that the enhanced activation of JNK by 2-ME is partially regulated by p53, highlighting the relationship of JNK and autophagy to p53 signaling pathway. Furthermore, we showed that 2-ME up-regulates damage-regulated autophagy modulator (DRAM), a p53 target gene, in Ewing sarcoma cells through a mechanism that involves JNK activation. The silencing of DRAM expression reduced both apoptosis and autophagy triggered by 2-ME in Ewing sarcoma and osteosarcoma cells. Our results therefore identify JNK as a novel mediator of DRAM regulation. These findings suggest that 2-ME or other anticancer therapies that increase DRAM expression or function could be used to effectively treat sarcoma patients.

The role of steroid hormones in the NF1 phenotype: focus on pregnancy

The Neurofibromatosis Type 1 (NF1) gene functions as a tumor suppressor gene. Loss of its protein, neurofibromin, in the autosomal dominant disorder NF1 is associated with peripheral nervous system tumors, particularly neurofibromas, benign lesions in which the major cell type is the Schwann Cell (SC). Benign and malignant human tumors found in NF1 patients are heterogeneous with respect to their cellular composition. The number and size of neurofibromas in NF1 patients has been shown to increase during pregnancy, with, in some cases, post-partum regression, which suggests hormonal involvement in this increase. However, in this review, we consider evidence from the literature that both direct hormonal influence on tumor growth and on angiogenesis may contribute to these effects.

Influence of hormones and hormone metabolites on the growth of Schwann cells derived from embryonic stem cells and on tumor cell lines expressing variable levels of neurofibromin

Loss of neurofibromin, the protein product of the tumor suppressor gene neurofibromatosis type 1 (NF1), is associated with neurofibromas, composed largely of Schwann cells. The number and size of neurofibromas in NF1 patients have been shown to increase during pregnancy. A mouse embryonic stem cell (mESC) model was used, in which mESCs with varying levels of neurofibromin were differentiated into Schwann-like cells. NF1 cell lines derived from a malignant and a benign human tumor were used to study proliferation in response to hormones. Estrogen and androgen receptors were not expressed or expressed at very low levels in the NF1+/+ cells, at low levels in NF1+/-cells, and robust levels in NF1-/-cells. A 17beta-estradiol (E2) metabolite, 2-methoxy estradiol (2ME2) is cytotoxic to the NF1-/- malignant tumor cell line, and inhibits proliferation in the other cell lines. 2ME2 or its derivatives could provide new treatment avenues for NF1 hormone-sensitive tumors at times of greatest hormonal influence.

Targeting human 8-oxoguanine DNA glycosylase to mitochondria protects cells from 2-methoxyestradiol-induced-mitochondria-dependent apoptosis

2-Methoxyestradiol (2-ME), an endogenous estrogen metabolite of 17beta-estradiol, is known to induce mitochondria-mediated apoptosis through several mechanisms. We sought to study the effect of mitochondrialy targeted hOGG1 (MTS-hOGG1) on HeLa cells exposed to 2-ME. MTS-hOGG1-expressing cells exposed to 2-ME showed increased cellular survival and had significantly less G(2)/M cell cycle arrest compared to vector-only-transfected cells. In addition, 2-ME exposure resulted in an increase in mitochondrial membrane potential, increased apoptosis, accompanied by higher activation of caspase-3, -9, cleavage of Bid to tBid and protein poly(ADP-ribose) polymerase (PARP) cleavage in HeLa cells lacking MTS-hOGG1. Fas inhibitors cerulenin or C75 inhibited 2-ME-induced caspase activation, PARP cleavage, apoptosis and reversed mitochondrial membrane hyperpolarization, thereby recapitulating the increased expression of MTS-hOGG1. Hence, MTS-hOGG1 plays an important protective role against 2-ME-mediated mitochondrial damage by blocking apoptosis induced through the Fas pathway.

The role of mitochondria in pharmacotoxicology: a reevaluation of an old, newly emerging topic

In addition to their well-known critical role in energy metabolism, mitochondria are now recognized as the location where various catabolic and anabolic processes, calcium fluxes, various oxygen-nitrogen reactive species, and other signal transduction pathways interact to maintain cell homeostasis and to mediate cellular responses to different stimuli. It is important to consider how pharmacological agents affect mitochondrial biochemistry, not only because of toxicological concerns but also because of potential therapeutic applications. Several potential targets could be envisaged at the mitochondrial level that may underlie the toxic effects of some drugs. Recently, antiviral nucleoside analogs have displayed mitochondrial toxicity through the inhibition of DNA polymerase-γ (pol-γ). Other drugs that target different components of mitochondrial channels can disrupt ion homeostasis or interfere with the mitochondrial permeability transition pore. Many known inhibitors of the mitochondrial electron transfer chain act by interfering with one or more of the respiratory chain complexes. Nonsteroidal anti-inflammatory drugs (NSAIDs), for example, may behave as oxidative phosphorylation uncouplers. The mitochondrial toxicity of other drugs seems to depend on free radical production, although the mechanisms have not yet been clarified. Meanwhile, drugs targeting mitochondria have been used to treat mitochondrial dysfunctions. Importantly, drugs that target the mitochondria of cancer cells have been developed recently; such drugs can trigger apoptosis or necrosis of the cancer cells. Thus the aim of this review is to highlight the role of mitochondria in pharmacotoxicology, and to describe whenever possible the main molecular mechanisms underlying unwanted and/or therapeutic effects.

Dual role of hydrogen peroxide in cancer: Possible relevance to cancer chemoprevention and therapy

Accumulating evidence suggests that hydrogen peroxide (H(2)O(2)) plays an important role in cancer development. Experimental data have shown that cancer cells produce high amounts of H(2)O(2). An increase in the cellular levels of H(2)O(2) has been linked to several key alterations in cancer, including DNA alterations, cell proliferation, apoptosis resistance, metastasis, angiogenesis and hypoxia-inducible factor 1 (HIF-1) activation. It has also been observed that the malignant phenotype of cancer cells can be reversed just by decreasing the cellular levels of H(2)O(2). On the other hand, there is evidence that H(2)O(2) can induce apoptosis in cancer cells selectively and that the activity of several anticancer drugs commonly used in the clinic is mediated, at least in part, by H(2)O(2). The present report discusses that the high levels of H(2)O(2) commonly observed in cancer cells may be essential for cancer development; these high levels, however, seem almost incompatible with cell survival and may make cancer cells more susceptible to H(2)O(2)-induced cell death than normal cells. An understanding of this dual role of H(2)O(2) in cancer might be exploited for the development of cancer chemopreventive and therapeutic strategies.

4-Methoxyestradiol-induced oxidative injuries in human lung epithelial cells

Epidemiological studies indicated that people exposed to dioxins were prone to the development of lung diseases including lung cancer. Animal studies demonstrated that 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) increased liver tumors and promoted lung metaplasia in females. Metabolic changes in 17beta-estradiol (E(2)) resulted from an interaction between TCDD and E(2) could be associated with gender difference. Previously, we reported that methoxylestradiols (MeOE(2)), especially 4-MeOE(2), accumulated in human lung cells (BEAS-2B) co-treated with TCDD and E(2). In the present study, we demonstrate unique accumulation of 4-MeOE(2), as a result of TCDD/E(2) interaction and revealed its bioactivity in human lung epithelial cell line (H1355). 4-Methoxyestradiol treatment significantly decreased cell growth and increased mitotic index. Elevation of ROS and SOD activity, with a concomitant decrease in the intracellular GSH/GSSG ratio, was also detected in 4-MeOE(2)-treated cells. Quantitative comet assay showed increased oxidative DNA damage in the 4-MeOE(2)-treated H1355 cells, which could be significantly reduced by the anti-oxidant N-acetylcysteine (NAC). However, inhibition of cell growth and increase in mitotic arrest induced by 4-MeOE(2) were unaffected by NAC. We concluded that 4-MeOE(2) accumulation resulting from TCDD and E(2) interaction would contribute to the higher vulnerability on lung pathogenesis in females when exposed to TCDD.

Reactive oxygen species and mitochondrial membrane potential are modulated during CDDP-induced apoptosis in EC-109 cells

cis-Diamminedichloroplatinum (CDDP), commonly know as cisplatin, is a well known DNA-damaging agent, which is highly active in suppressing the proliferation of tumor cells. However, it is not clear that CDDP can induce growth inhibition of esophagus cancer cells. Using the cell line EC-109 from the esophagus, we found that CDDP would induce apoptotic responses. The addition of CDDP to cells led to the inhibition of growth in a time- and dose-dependent manner. CDDP generated reactive oxygen species (ROSs) in cells, which brought about a reduction in the intracellular mitochondrial transmembrane potential (Deltapsim), leading to apoptosis. Our findings demonstrate that ROSs, and the resulting oxidative stress, play a pivotal role in apoptosis. Preincubation of EC-109 cells with the hydrogen-peroxide-scavenging enzyme catalase partially inhibited the following: (i) the production of ROS; (ii) the disruption of the Deltapsim; and (iii) apoptosis. These results indicate that the enhancement of the generation of ROS and the disruption of Deltapsim are events involved in the apoptotic pathway of EC-109 induced by CDDP.

2-Methoxyestradiol, an Endogenous Mammalian Metabolite, Radiosensitizes Colon Carcinoma Cells through c-Jun NH2-Terminal Kinase Activation

PURPOSE

2-Methoxyestradiol (2ME), an estrogen metabolite, induces apoptosis in various cell types. We investigated whether 2ME pretreatment can radiosensitize colon adenocarcinoma cells.

EXPERIMENTAL DESIGN

Radiosensitizing effects of 2ME were evaluated by cell death, clonogenic assay, nuclear fragmentation, and tumor progression of xenografts. Ionizing radiation-induced DNA damage was evaluated by histone H2AX phosphorylation and its foci. The c-Jun NH2-terminal kinase (JNK) activation was evaluated by anti-phosphorylated JNK antibody and inhibited by the JNK-specific inhibitor SP600125 or dominant-negative SEK1 expression.

RESULTS

Clonogenic assays revealed that 2ME, but not estradiol, radiosensitized three colon carcinoma cells, DLD-1, HCT-8, and HCT-15, and strongly suppressed tumor progression of DLD-1 xenografts. Gene transfer-mediated Bcl-xL overexpression largely abolished both augmented apoptosis and reduced survival fractions. Pretreatment with 2ME enhanced H2AX phosphorylation, its foci, and phosphorylation of ATM kinase and delayed re-entry of cell cycle progression after ionizing radiation. Augmentation of both radiosensitivity and H2AX phosphorylation was substantially reduced by SP600125 or overexpression of a dominant-negative mutant SEK1.

CONCLUSION

2ME radiosensitized colon carcinoma cells through enhanced DNA damage via JNK activation, thereby representing a novel radiosensitizing therapy against colon cancer.

Crosstalk between extrinsic and intrinsic cell death pathways in pancreatic cancer: synergistic action of estrogen metabolite and ligands of death receptor family

2-Methoxyestradiol is a physiologic metabolite of 17beta-estradiol. This orally active compound can inhibit tumor growth or metastasis in tumor models without inducing any clinical sign of toxicity. Our previous studies indicated that 2-methoxyestradiol-mediated apoptosis involves the disappearance of intact 21-kDa Bid protein, cytochrome c release, and predominant procaspase-3 cleavage. Here, using MIA PaCa-2 cells as a model, we investigated whether this estrogen metabolite induces apoptosis by converging two major pathways: the death receptor-mediated extrinsic and the mitochondrial intrinsic pathway. Exogenous expression of dominant-negative caspase-8 or dominant-negative FADD reverts the effect of 2-methoxyestradiol-mediated cell death. In parallel with this observation, Z-IETD-FMK, a cell permeable irreversible inhibitor of caspase-8, can render significant protection against 2-methoxyestradiol-induced apoptosis. RNase protection assay and cell surface receptor analysis by flow cytometry show the up-regulation of members of death receptor family in 2-methoxyestradiol-exposed pancreatic cancer cells. Our mechanistic studies also implicate that oxidative stress precedes 2-methoxyestradiol-mediated c-Jun NH2-terminal kinase activation, leading to elevated Fas level. Because 2-methoxyestradiol is able to trigger death receptor signaling, we were interested in examining the effects of 2-methoxyestradiol and Fas ligand (FasL)/tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) together on pancreatic cancer cell death. Interestingly, the endogenous angiogenesis inhibitor 2-methoxyestradiol augments FasL/TRAIL-induced apoptosis in these cells. Moreover, the combination of 2-methoxyestradiol and TRAIL reduces the tumor burden in vivo in MIA PaCa-2 tumor xenograft model by caspase-3 activation.

Effects of hormone deprivation and 2-methoxyestradiol combination therapy on hormone-dependent prostate cancer in vivo

2-Methoxyestradiol (2-ME) has potent antiproliferative effects on cancer cells. Its utility alone or in combination with other therapies for treating prostate cancer, however, has not been fully explored. Androgen-dependent and independent human prostate cancer cells were examined in vivo for their response to combination therapy. Efficacy was assessed by terminal deoxynucleotide transferase-mediated dUTP nick-end labeling assay and measuring microvessel density (MVD) in excised tumors. Animals harboring hormone-dependent tumors treated with 2-ME alone, androgen deprivation therapy alone, or the combination of the two had a 3.1-fold, 5.3-fold, and 10.1-fold increase in apoptosis, respectively. For hormone-independent tumors, treatment with 2-ME resulted in a 2.43-fold increase in apoptosis and a 73% decrease in MVD. 2-ME was most effective against hormone-dependent tumors in vivo and combination therapy resulted in a significant increase in efficacy compared to no treatment controls and trended toward greater efficacy than either 2-ME or androgen deprivation alone. Combination therapy should be investigated further as an additional therapeutic option for early prostate cancer.

2-methoxyestradiol induces apoptosis in cultured human anaplastic thyroid carcinoma cells

Anaplastic thyroid carcinoma (ATC) is one of the most malignant tumors in humans, and currently there is no effective treatment. In the present study we investigated the effect of an endogenous estrogen metabolite, 2-methoxyestradiol (2-ME), on the growth of human ATC cells. 2-ME treatment had a strong growth inhibitory effect on five human ATC cell lines (HTh7, HTh 74, HTh83, C643, and SW1736), but showed no effect on one cell line (KAT-4). Cell cycle analysis of the growth-inhibited cells showed that 2-ME induced a G2/M-arrest, followed by an increased fraction of cells in sub-G1. Analysis of internucleosomal DNA laddering as well as DNA fragmentation in a terminal deoxynucleotide transferase-mediated dUTP nick-end labeling (TUNEL) assay demonstrated a high number of cells undergoing apoptosis after 2-ME treatment. An increased activation of caspase-3 and caspase-8 by 2-ME was observed, and inhibition of caspase-3 decreased the apoptotic effect. Addition of 2-ME increased activity of p38 mitogen-activated protein kinase (MAPK) in the sensitive HTh7 as well as the refractory KAT-4 cells, however, activation of stress-activated protein kinase/c-jun aminoterminal kinase (SAPK/JNK) was seen only in the HTh7 cells. Inhibitors of p38 MAPK and SAPK/JNK significantly attenuated the 2-ME effect. Taken together, our data demonstrate an antiproliferative and apoptotic effect of 2-ME on ATC cells involving activation of MAPKs.

TNFα Potentiates 2-Methoxyestradiol-Induced Mitochondrial Death Pathway

Ewing sarcoma cells are resistant to TNFalpha-induced cell death and this resistance results from the activation of the transcription factor NF-kappaB. Here, we investigated whether NF-kappaB activation interferes with 2-Me-induced cell death signaling in Ewing sarcoma cells and we examined the effect of treatment of these cells with 2-Me either alone or in combination with TNFalpha. Our results show that TNFa cooperates with 2-Me to induce apoptosis in Ewing tumor cells through mitochondrial cell death signaling. These results suggest that the use of TNFalpha in combination with 2-Me may be beneficial for Ewing tumor treatment.

Tamoxifen and estradiol interact with the flavin mononucleotide site of complex I leading to mitochondrial failure

This study evaluated the action of tamoxifen and estradiol on the function of isolated liver mitochondria. We observed that although tamoxifen and estradiol per se did not affect mitochondrial complexes II, III, or IV, complex I is affected, this effect being more drastic (except for state 4 of respiration) when mitochondria were coincubated with both drugs. Furthermore, using two respiratory chain inhibitors, rotenone and diphenyliodonium chloride, we identified the flavin mononucleotide site of complex I as the target of tamoxifen and/or estradiol action(s). Tamoxifen (25 microm) per se induced a significant increase in hydrogen peroxide production and state 4 of respiration. Additionally, a significant decrease in respiratory control ratio, transmembrane, and depolarization potentials were observed. Estradiol per se decreased carbonyl cyanide p-trifluoromethoxyphenylhydrazone (FCCP)-stimulated respiration, state 3 of respiration, and respiratory control ratio and increased lag phase of repolarization. With the exception of state 4 of respiration whose increase induced by tamoxifen was reversed by the presence of estradiol, the effects of tamoxifen were highly exacerbated when estradiol was present. We observed that 10 microm tamoxifen in the presence of estradiol affected mitochondria significantly by decreasing FCCP-stimulated respiration, state 3 of respiration, respiratory control ratio, and ADP depolarization and increasing the lag phase of repolarization. All of the deleterious effects induced by 25 microm tamoxifen were highly exacerbated in the presence of estradiol. Furthermore, we observed that the effects of both compounds were independent of estrogen receptors because the pure estrogen antagonist ICI 182,780 did not interfere with tamoxifen and/or estradiol detrimental effects. Altogether, our data provide a mechanistic explanation for the multiple cytotoxic effects of tamoxifen including its capacity to destroy tamoxifen-resistant breast cancer cells in the presence of estradiol. This new piece of information provides a basis for the development of new and promising anticancer therapeutic strategies.

alpha-Lipoic acid induces apoptosis in human colon cancer cells by increasing mitochondrial respiration with a concomitant O2-*-generation

The antioxidant alpha-lipoic acid (ALA) has been shown to affect a variety of biological processes associated with oxidative stress including cancer. We determined in HT-29 human colon cancer cells whether ALA is able to affect apoptosis, as an important parameter disregulated in tumour development. Exposure of cells to ALA or its reduced form dihydrolipoic acid (DHLA) for 24 h dose dependently increased caspase-3-like activity and was associated with DNA-fragmentation. DHLA but not ALA was able to scavenge cytosolic O2-* in HT-29 cells whereas both compounds increased O2-*-generation inside mitochondria. Increased mitochondrial O2-*-production was preceded by an increased influx of lactate or pyruvate into mitochondria and resulted in the down-regulation of the anti-apoptotic protein bcl-X(L). Mitochondrial O2-*-generation and apoptosis induced by ALA and DHLA could be prevented by the O2-*-scavenger benzoquinone. Moreover, when the lactate/pyruvate transporter was inhibited by 5-nitro-2-(3-phenylpropylamino) benzoate, ALA- and DHLA-induced mitochondrial ROS-production and apoptosis were blocked. In contrast to HT-29 cells, no apoptosis was observed in non-transformed human colonocytes in response to ALA or DHLA addition. In conclusion, our study provides evidence that ALA and DHLA can effectively induce apoptosis in human colon cancer cells by a prooxidant mechanism that is initiated by an increased uptake of oxidizable substrates into mitochondria.

Synergistic antileukemic interactions between 2-medroxyestradiol (2-ME) and histone deacetylase inhibitors involve Akt down-regulation and oxidative stress

Interactions between the endogenous estradiol metabolite 2-medroxyestradiol (2-ME) and histone deacetylase inhibitors (HDACIs) have been investigated in human leukemia cells. Coadministration of subtoxic or marginally toxic concentrations of 2-ME and SAHA or sodium butyrate in diverse human leukemia-cell types resulted in a marked increase in oxidative damage (eg, generation of reactive oxygen species [ROSs]), mitochondrial injury (eg, cytochrome c release and Bax translocation), caspase activation, and apoptosis. These interactions were also noted in primary human leukemia cells but not in normal bone marrow CD34+ cells. Synergistic interactions between these agents were associated with inactivation of Akt and activation of c-Jun N-terminal kinase (JNK). Essentially all of these events were reversed by free radical scavengers such as the manganese superoxide dismutase (MnSOD) mimetic TBAP and catalase. Notably, treatment with 2-ME/HDACIs resulted in down-regulation of thioredoxin, MnSOD, and glutathione peroxidase. Enforced activation of Akt blocked 2-ME/HDACI-mediated mitochondrial injury, caspase activation, and JNK up-regulation, but not generation of ROSs. Pharmacologic or genetic (siRNA) interruption of the JNK pathway also significantly attenuated the lethality of this regimen. Together, these findings support a model in which antileukemic synergism between 2-ME and HDACIs stems primarily from induction of oxidative damage, leading in turn to Akt inactivation and JNK activation, culminating in mitochondrial injury and apoptosis. They also raise the possibility that these events may preferentially occur in leukemic versus normal hematopoietic cells.

Melatonin potentiates flavone-induced apoptosis in human colon cancer cells by increasing the level of glycolytic end products

Melatonin is a natural compound synthesized by a variety of organs. It has been described to possess cell protecting activity in normal cells but was shown to induce apoptotic cell death in cancer cells. We determined to which extent and based on which molecular mechanisms melatonin is able to cause apoptosis in HT-29 human colon cancer cells. Induction of apoptosis was assessed by caspase-3-like activity, nuclear fragmentation and chromatin condensation. Melatonin, when given alone at a concentration of 1 mM, did not affect any of the apoptosis markers. It potentiated apoptosis induced by the flavonoid flavone significantly. Whereas flavone alone at a concentration of 150 microM led to a 8-fold increase in caspase-3-like activity associated with around 40% of cells displaying DNA-fragmentation, a combination of flavone and melatonin increased caspase-3-like activity 30-fold and 80% of cells exhibited fragmentation of DNA when compared to untreated controls. Melatonin caused an increase in cytosolic lactate levels that most likely allows the flavone-induced activation of the mitochondrial pyruvate/lactate importer to deliver more substrates to mitochondrial respiration. The subsequent increased production of mitochondrial O2-* in the presence of flavone was further increased by melatonin. Scavenging mitochondrial O2-* by benzoquinone or blocking the lactate/pyruvate transporter by 5-nitro-2-(3-phenylpropylamino) benzoate inhibited mitochondrial O2-* -generation and apoptosis execution mediated by flavone and melatonin. Our study provides evidence that melatonin potentiates flavone-induced apoptosis in HT-29 human colon cancer cells by enhancing the level of oxidizable substrates that can be transported into mitochondria in the presence of flavone.