2-Methoxyestradiol induces mitochondria dependent apoptotic signaling in pancreatic cancer cells

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.

Cancer-specific survival after diagnosis in men versus women: A pan-cancer analysis

Comprehensive understanding of cancer-specific survival differences in gender is critical for cancer prevention and treatment. Based on the Surveillance Epidemiology and End Results database, we included data from the most prevalent cancers (lung, esophageal, liver, pancreatic, stomach, colorectal, kidney, and bladder cancer). Cox proportional hazards regression models were constructed to estimate hazard ratios, simultaneously adjusting for demographic, clinical, and treatment factors. Overall, male patients had a worse cancer-specific survival than female patients. After adjustment for cancer prevalence with 1:1 matching, gender remained a significant factor in cancer-specific survival. Among the included cancer types, female patients showed survival benefit in lung, liver, colorectal, pancreatic, stomach, and esophageal cancer, and male patients showed better survival in bladder cancer. Except for kidney cancer, the gender disparity was consistent between cancer patients with nonmetastatic and metastatic disease. Overall, gender appears to be a significant factor influencing cancer-specific survival, and the prognosis of female patients is better than male patients in most cancers. This work might inspire the development of strategies for gender-specific precision cancer prevention and treatment.

Redox regulation of DUBs and its therapeutic implications in cancer

Reactive oxygen species (ROS) act as a double-edged sword in cancer, where low levels of ROS are beneficial but excessive accumulation leads to cancer progression. Elevated levels of ROS in cancer are counteracted by the antioxidant defense system. An imbalance between ROS generation and the antioxidant system alters gene expression and cellular signaling, leading to cancer progression or death. Post-translational modifications, such as ubiquitination, phosphorylation, and SUMOylation, play a critical role in the maintenance of ROS homeostasis by controlling ROS production and clearance. Recent evidence suggests that deubiquitinating enzymes (DUBs)-mediated ubiquitin removal from substrates is regulated by ROS. ROS-mediated oxidation of the catalytic cysteine (Cys) of DUBs, leading to their reversible inactivation, has emerged as a key mechanism regulating DUB-controlled cellular events. A better understanding of the mechanism by which DUBs are susceptible to ROS and exploring the ways to utilize ROS to pharmacologically modulate DUB-mediated signaling pathways might provide new insight for anticancer therapeutics. This review assesses the recent findings regarding ROS-mediated signaling in cancers, emphasizes DUB regulation by oxidation, highlights the relevant recent findings, and proposes directions of future research based on the ROS-induced modifications of DUB activity.

Sex Differences in the Exocrine Pancreas and Associated Diseases

Differences in pancreatic anatomy, size, and function exist in men and women. The anatomical differences could contribute to the increase in complications associated with pancreatic surgery in women. Although diagnostic criteria for pancreatitis are the same in men and women, major sex differences in etiology are reported. Alcohol and tobacco predominate in men, whereas idiopathic and obstructive etiologies predominate in women. Circulating levels of estrogens, progesterone, and androgens contribute significantly to overall health outcomes; premenopausal women have lower prevalence of cardiovascular and pancreatic diseases suggesting protective effects of estrogens, whereas androgens promote growth of normal and cancerous cells. Sex chromosomes and gonadal and nongonadal hormones together determine an individual's sex, which is distinct from gender or gender identity. Human pancreatic disease etiology, outcomes, and sex-specific mechanisms are largely unknown. In rodents of both sexes, glucocorticoids and estrogens from the adrenal glands influence pancreatic secretion and acinar cell zymogen granule numbers. Lack of corticotropin-releasing factor receptor 2 function, a G protein-coupled receptor whose expression is regulated by both estrogens and glucocorticoids, causes sex-specific changes in pancreatic histopathology, zymogen granule numbers, and endoplasmic reticulum ultrastructure changes in acute pancreatitis model. Here, we review existing literature on sex differences in the normal exocrine pancreas and mechanisms that operate at homeostasis and diseased states in both sexes. Finally, we review pregnancy-related pancreatic diseases and discuss the effects of sex differences on proposed treatments in pancreatic disease.

Resveratrol induced apoptosis in human gastric carcinoma SGC-7901 cells via activation of mitochondrial pathway

BACKGROUND

Resveratrol is a natural polyphenolic compound and its anticancer effect has been receiving considerable attention. Previous studies showed that resveratrol could inhibited the growth of human gastric carcinoma cells and apoptosis induction was an important mechanism. However, whether mitochondrial pathway was involved in resveratrol-induced apoptosis in human gastric cancer was not very clear.

METHODS

The cells were examined by 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2-H-tetrazolium bromide (MTT) assay, Annexin V/PI staining assay, mitochondrial membrane depolarization, cell morphological assessment, cytochrome c release assay, and Western blotting assay.

RESULTS

In this study, we found that resveratrol induced apoptosis in human gastric carcinoma SGC-7901 cells. Cleaved PARP was observed and caspase-3 was activated by resveratrol. Next, the mitochondrial membrane potential of cells dissipated after the cells were treated by resveratrol. Moreover, we found that pro-caspase 9 was downregulated and cytochrome c released from mitochondrial to the cytosol. We also found that the expression ratio of Bax/Bcl-2 was increased in the treated cells. We finally showed that resveratrol inhibited the proliferation of SGC-7901 xerograph in vivo.

CONCLUSIONS

Collectively, our findings demonstrate that resveratrol triggers apoptosis via mitochondrial pathway in SGC-7901 cells, which provide more basis for resveratrol acting as antitumor agents in cancer therapy.

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.

III-10, a newly synthesized flavonoid, induces cell apoptosis with the involvement of reactive oxygen species-mitochondria pathway in human hepatocellular carcinoma cells

Study of the mechanisms of apoptosis in tumor cells is an important field of tumor therapy and cancer molecular biology. We recently established that III-10, a new flavonoid with a pyrrolidinyl and a benzyl group substitution, exerted its anti-tumor effect via inducing differentiation of human U937 leukemia cells. In this study, we demonstrated that III-10 induced cell apoptosis in human hepatocellular carcinoma cells. The activation of caspase-3, caspase-9, and the increased expression ratio of Bax/Bcl-2 were detected in III-10-induced apoptosis. Z-VAD-FMK, a pan-caspase inhibitor, partly attenuated the apoptotic induction of III-10 on both HepG2 and BEL-7402 cells. Furthermore, the increase of intracellular reactive oxygen species levels and the reduction of mitochondria ΔΨm were also observed in BEL-7402 and HepG2 cells after the treatment of III-10. Pretreatment with NAC, a reactive oxygen species production inhibitor, partly attenuated the apoptosis induced by III-10 via blocking the reactive oxygen species generation. Our data also showed that III-10 induced the release of cytochrome c and AIF to cytosol followed after the reactive oxygen species accumulation. Moreover, the GSH levels and ATP generation were both inhibited after III-10 treatment. Besides, the MAPK, the downstream effect of reactive oxygen species accumulation including JNK could be activated by III-10, as well as the inactivation of ERK. Collectively, the generation of reactive oxygen species might play an crucial role in III-10-induced mitochondrial apoptosis pathway, provided more stubborn evidence for III-10 as a potent anticancer therapeutic candidate.

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.

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.

Hrk mediates 2-methoxyestradiol-induced mitochondrial apoptotic signaling in prostate cancer cells

Prostate cancer is one of the most prevalent cancers in males and ranks as the second most common cause of cancer-related deaths. 2-methoxyestradiol (2-ME), an endogenous estrogen metabolite, is a promising anticancer agent for various types of cancers. Although 2-ME has been shown to activate c-Jun-NH2-kinase (JNK) and mitochondrial-dependent apoptotic signaling pathways, the underlying mechanisms, including downstream effectors, remain unclear. Here, we report that the human Bcl-2 homology 3 (BH3)-only protein harakiri (Hrk) is a critical effector of 2-ME-induced JNK/mitochondria-dependent apoptosis in prostate cancer cells. Hrk mRNA and protein are preferentially upregulated by 2-ME, and Hrk induction is dependent on the JNK activation of c-Jun. Hrk knockdown prevents 2-ME-mediated apoptosis by attenuating the decrease in mitochondrial membrane potential, subsequent cytochrome c (cyt c) release, and caspase activation. Involvement of the proapoptotic protein Bak in this process suggested the possible interaction between Hrk and Bak. Thus, Hrk activation by 2-ME or its overexpression displaced Bak from the complex with antiapoptotic protein Bcl-xL, whereas deletion of the Hrk BH3 domain abolished its interaction with Bcl-xL, reducing the proapoptotic function of Hrk. Finally, Hrk is also involved in the 2-ME-mediated reduction of X-linked inhibitor of apoptosis through Bak activation in prostate cancer cells. Together, our findings suggest that induction of the BH3-only protein Hrk is a critical step in 2-ME activation of the JNK-induced apoptotic pathway, targeting mitochondria by liberating proapoptotic protein Bak.

Increased COMT expression in pancreatic cancer and correlation with clinicopathologic parameters

Catechol-O-methyl transferase (COMT) is an enzyme involved in estrogen metabolism. Proteomic and immunoproteomic screens suggested COMT might be an immunogenic membrane antigen in human pancreatic cancer. The aim of this study was to investigate the dynamic expression of COMT in pancreatic ductal adenocarcinoma (PDAC) and noncancerous pancreatic tissue, and to determine the relationship between COMT expression and clinicopathologic parameters. COMT expression was analyzed by reverse transcription-polymerase chain reaction (RT-PCR) and western blot in five pancreatic cell lines and five pairs of PDAC and noncancerous pancreatic tissue. Immunohistochemistry was used to evaluate COMT expression in tissue microarrays and 20 cases of paraffin-embedded clinical specimens. The results indicated that COMT expression was detected in AsPC-1, BxPC-3, MIA PaCa-2, Capan-1 and SW1990 pancreatic cell lines, and in five pairs of PDAC and noncancerous pancreatic tissue, at the mRNA and protein levels. Immunohistochemistry analysis revealed that COMT expression was significantly higher in PDAC than in nonmalignant pancreatic tissue. High expression of COMT significantly correlated to early T stages. Therefore, we conclude that COMT might serve as a potential biomarker for applied clinical pathology in PDAC.

Acquisition of resistance of pancreatic cancer cells to 2-methoxyestradiol is associated with the upregulation of manganese superoxide dismutase

Acquired resistance of cancer cells to anticancer drugs or ionizing radiation (IR) is one of the major obstacles in cancer treatment. Pancreatic cancer is an exceptional aggressive cancer, and acquired drug resistance in this cancer is common. Reactive oxygen species (ROS) play an essential role in cell apoptosis, which is a key mechanism by which radio- or chemotherapy induce cell killing. Mitochondria are the major source of ROS in cells. Thus, alterations in the expression of mitochondrial proteins, involved in ROS production or scavenging, may be closely linked to the resistance of cancer cells to radio- or chemotherapy. In the present study, we generated a stable cell line by exposing pancreatic cancer cells to increasing concentrations of ROS-inducing, anticancer compound 2-methoxyestradiol (2-ME) over a 3-month period. The resulting cell line showed strong resistance to 2-ME and contained an elevated level of ROS. We then used a comparative proteomics method to profile the differential expression of mitochondrial proteins between the parental and the resistant cells. One protein identified to be upregulated in the resistant cells was manganese superoxide dismutase (SOD2), a mitochondrial protein that converts superoxide radicals to hydrogen peroxides. Silencing of SOD2 resensitized the resistant cells to 2-ME, and overexpression of SOD2 led the parental cells to 2-ME resistance. In addition, the 2-ME-resistant cells also showed resistance to IR. Our results suggest that upregulation of SOD2 expression is an important mechanism by which pancreatic cancer cells acquire resistance to ROS-inducing, anticancer drugs, and potentially also to IR.

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.

In vitro effects of 2-methoxyestradiol on cell numbers, morphology, cell cycle progression, and apoptosis induction in oesophageal carcinoma cells

The influence of 2-methoxyestradiol (2-ME) was investigated on cell numbers, morphology, cell cycle progression, and apoptosis induction in an oesophageal carcinoma cell line (WHCO3). Dose-dependent studies (1 x 10(-9)M-1 x 10(-6)M) revealed that 2-ME significantly reduced cell numbers to 60% in WHCO3 after 72 h of exposure at a concentration of 1 x 10(-6)M compared to vehicle-treated cells. Morphological studies entailing light-, fluorescent-, as well as transmission electron microscopy (TEM) confirmed 2-ME's antimitotic effects. These results indicated hallmarks of apoptosis including cell shrinkage, hypercondensation of chromatin, cell membrane blebbing, and apoptotic bodies in treated cells. Flow cytometric analyses demonstrated an increase in the G(2)/M-phase after 2-ME exposure; thus preventing cells from proceeding through the cell cycle. beta-tubulin immunofluorescence revealed that 2-ME caused spindle disruption. In addition, increased expression of death receptor 5 protein was observed further supporting the proposed mechanism of apoptosis induction via the extrinsic pathway in 2-ME-exposed oesophageal carcinoma cells.

Comparison of 2-Methoxyestradiol and Methotrexate Effects on Non-Hodgkin's B-Cell Lymphoma

PURPOSE

Methotrexate (MTX) is the most commonly used chemotherapeutic agent to treat primary central nervous system lymphoma (PCNSL) and intraocular lymphoma (IOL). 2-methoxyestradiol (2ME2) is a potent antitumor and anti-angiogenesis agent which, unlike other cytotoxic drugs, has minimal toxicity. In this study, anti-proliferative, apoptotic, and cell-cycle effects of 2ME2 and MTX were compared to evaluate 2ME2 efficacy in human lymphoma cells, models for non-Hodgkin B cell lymphomas.

METHODS

The cells were cultured and incubated with varying concentrations of 2ME2 or MTX. A tetrazolium-based colorimetric assay was used to quantify the anti-proliferative effects of 2ME2 and MTX using a microplate reader. To detect apoptotic and cell cycle distribution changes induced by 2ME2 and MTX, the cells were stained with Annexin V-FITC and/or propidium iodide (PI) and analyzed by flow cytometry.

RESULTS

Lymphoma cell proliferation was inhibited by 50% at concentrations ranging from 0.4 to 1 microM for 2ME2 and 0.06 to 0.2 microM for MTX. Induction of apoptosis by 2ME2 and MTX was observed in the tested cells. 2ME2 was a G2/M-phase specific blocker whereas MTX was an S-phase specific blocker in cell cycle analyses. At 1 microM concentration, 2ME2 and MTX showed similar anti-proliferative effect on the lymphoma cell lines. In previously reported studies, for normal endothelial cells, 1 microM 2ME2 showed no appreciable toxicity, while MTX at this same concentration exhibited significant cytotoxicity. 2ME2 at a therapeutic target concentration of 1 mu M may be an effective and relatively non-toxic drug for the treatment of PCNSL with IOL.

CONCLUSIONS

Our study of the effect of 2ME2 and MTX on anti-proliferation, apoptosis, and cell cycling suggests that 2ME2 is a potential agent for treating PCNSL and IOL.

Bcl-2 blocks 2-methoxyestradiol induced leukemia cell apoptosis by a p27(Kip1)-dependent G1/S cell cycle arrest in conjunction with NF-kappaB activation

2-Methoxyestradiol (2-ME2) induces leukemia cells to undergo apoptosis in association with Bcl-2 inactivation but the mechanisms whereby Bcl-2 contributes to protection against programmed cell death in this context remain unclear. Here we showed that 2-ME2 inhibited the proliferation of Jurkat leukemia cells by markedly suppressing the levels of cyclins D3 and E, E2F1 and p21(Cip1/Waf1) and up-regulating p16(INK4A). Further, 2-ME2 induced apoptosis of Jurkat cells in association with down-regulation and phosphorylation of Bcl-2 (as mediated by JNK), up-regulation of Bak, activation of caspases-9 and -3 and PARP-1 cleavage. To determine the importance and mechanistic role of Bcl-2 in this process, we enforced its expression in Jurkat cells by retroviral transduction. Enforcing Bcl-2 expression in Jurkat cells abolished 2-ME2-induced apoptosis and instead produced a G1/S phase cell cycle arrest in association with markedly increased levels of p27(Kip1). Bcl-2 and p27(Kip1) were localized mainly in the nucleus in these apoptotic resistant cells. Interestingly, NF-kappaB activity and p50 levels were increased by 2-ME2 and suppression of NF-kappaB signaling reduced p27(Kip1) expression and sensitized cells to 2-ME2-induced apoptosis. Importantly, knocking-down p27(Kip1) in Jurkat Bcl-2 cells sensitized them to spontaneous and 2-ME2-induced apoptosis. Thus, Bcl-2 prevented the 2-ME2-induced apoptotic response by orchestrating a p27(Kip1)-dependent G1/S phase arrest in conjunction with activating NF-kappaB. Thus, we achieved a much better understanding of the penetrance and mechanistic complexity of Bcl-2 dependent anti-apoptotic pathways in cancer cells and why Bcl-2 inactivation is so critical for the efficacy of apoptosis and anti-proliferative inducing drugs like 2-ME2.

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.

Molecular consequences of SOD2 expression in epigenetically silenced pancreatic carcinoma cell lines

Manganese superoxide dismutase (SOD2) is an enzyme that catalyses the dismutation of superoxide in the mitochondria, leading to reduced levels of reactive oxygen species. Reduced expression levels of SOD2 have been shown to result in increased DNA damage and sod2 heterozygous mice have increased incidences of cancer. It has also been shown that SOD2 expression is lost in pancreatic cell lines, with reintroduction of SOD2 resulting in decreased rate of proliferation. The mechanism of decreased SOD2 expression in pancreatic carcinoma has not been previously determined. We demonstrate, through sodium bisulphite sequencing, that the sod2 locus is methylated in some pancreatic cell lines leading to a corresponding decrease in SOD2 expression. Methylation can be reversed by treatment with zebularine, a methyltransferase inhibitor, resulting in restored SOD2 expression. Furthermore, we demonstrate that sensitivity of pancreatic carcinoma cell lines to 2-methoxyestradiol correlates with SOD2 expression and SOD2 modulation can alter the sensitivity of these cells. Using both genomics and proteomics, we also identify molecular consequences of SOD2 expression in MIA-PaCa2 cells, including dephosphorylation of VEGFR2 and the identification of both SOD2-regulated genes and transcription factors with altered binding activity in response to SOD2 expression.

3,17-disubstituted 2-alkylestra-1,3,5(10)-trien-3-ol derivatives: synthesis, in vitro and in vivo anticancer activity

Estradiol-3,17-O,O-bis-sulfamates inhibit steroid sulfatase (STS), carbonic anhydrase (CA), and, when substituted at C-2, cancer cell proliferation and angiogenesis. C-2 Substitution and 17-sulfamate replacement of the estradiol-3,17-O,O-bis-sulfamates were explored with efficient and practical syntheses developed. Evaluation against human cancer cell lines revealed the 2-methyl derivative 27 (DU145 GI(50) = 0.38 microM) as the most active novel bis-sulfamate, while 2-ethyl-17-carbamate derivative 52 (GI(50) = 0.22 microM) proved most active of its series (cf. 2-ethylestradiol-3,17-O,O-bis-sulfamate 4 GI(50) = 0.21 microM). Larger C-2 substituents were deleterious to activity. 2-Methoxy-17-carbamate 50 was studied by X-ray crystallography and was surprisingly 13-fold weaker as an STS inhibitor compared to parent bis-sulfamate 3. The potential of 4 as an orally dosed anti-tumor agent is confirmed using breast and prostate cancer xenografts. In the MDA-MB-231 model, dramatic reduction in tumor growth or regression was observed, with effects sustained after cessation of treatment. 3-O-Sulfamoylated 2-alkylestradiol-17-O-carbamates and sulfamates have considerable potential as anticancer agents.

2-methoxyestradiol induces apoptosis and cell cycle arrest in human chondrosarcoma cells

2-Methoxyestradiol (2ME) is an endogenous metabolite with estrogen receptor-independent anti-tumor activity. The current study seeks to determine the mechanism of anti-tumor activity of 2ME on human chondrosarcoma. 2ME caused a time- and dose-dependent cytotoxity in chondrosarcoma cells, while primary chondrocytes were minimally affected. Cells accumulated in G0/G1 phase in response to 2ME and DAPI stain indicated an induction of apoptosis. Bax, Cytochrome C, and Caspase-3 protein expression were increased, while p53 expression was decreased. A higher Bax/Bcl-2 ratio followed 2ME treatment. 2ME has a potentially promising role as a systemic therapy of chondrosarcoma when the mechanism of action is better delineated.

Glutathione supplementation potentiates hypoxic apoptosis by S-glutathionylation of p65-NFkappaB

In murine embryonic fibroblasts, N-acetyl-L-cysteine (NAC), a GSH generating agent, enhances hypoxic apoptosis by blocking the NFkappaB survival pathway (Qanungo, S., Wang, M., and Nieminen, A. L. (2004) J. Biol. Chem. 279, 50455-50464). Here, we examined sulfhydryl modifications of the p65 subunit of NFkappaB that are responsible for NFkappaB inactivation. In MIA PaCa-2 pancreatic cancer cells, hypoxia increased p65-NFkappaB DNA binding and NFkappaB transactivation by 2.6- and 2.8-fold, respectively. NAC blocked these events without having an effect on p65-NFkappaB protein levels and p65-NFkappaB nuclear translocation during hypoxia. Pharmacological inhibition of the NFkappaB pathway also induced hypoxic apoptosis, indicating that the NFkappaB signaling pathway is a major protective mechanism against hypoxic apoptosis. In cell lysates after hypoxia and treatment with N-ethylmaleimide (thiol alkylating agent), dithiothreitol (disulfide reducing agent) was not able to increase binding of p65-NFkappaB to DNA, suggesting that most sulfhydryls in p65-NFkappaB protein were in reduced and activated forms after hypoxia, thereby being blocked by N-ethylmaleimide. In contrast, with hypoxic cells that were also treated with NAC, dithiothreitol increased p65-NFkappaB DNA binding. Glutaredoxin (GRx), which specifically catalyzes reduction of protein-SSG mixed disulfides, reversed inhibition of p65-NFkappaB DNA binding in extracts from cells treated with hypoxia plus NAC and restored NFkappaB activity. This finding indicated that p65-NFkappaB-SSG was formed in situ under hypoxia plus NAC conditions. In cells, knock-down of endogenous GRx1, which also promotes protein glutathionylation under hypoxic radical generating conditions, prevented NAC-induced NFkappaB inactivation and hypoxic apoptosis. The results indicate that GRx-dependent S-glutathionylation of p65-NFkappaB is most likely responsible for NAC-mediated NFkappaB inactivation and enhanced hypoxic apoptosis.

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.

Metastatic progression of pancreatic cancer: changes in antioxidant enzymes and cell growth

Pancreatic cancer has a dismal prognosis due to the fact that patients present late when metastatic disease is already present. Previous studies have demonstrated that pancreatic cancer cells have decreased levels of MnSOD, which correlates well with increased rates of tumor cell proliferation. Recently, we have found that nude mice injected with MIA PaCa-2 human pancreatic cancer cells in the flank occasionally develop ascites and intra-abdominal metastatic deposits. Mice that developed ascites were sacrificed and the ascites cultured. Necropsy demonstrated metastatic tumors in the retroperitoneum, which were excised, digested, and cultured. Western blots, enzyme activity and enzyme activity gels were performed for manganese superoxide dismutase (MnSOD), copper/zinc (CuZnSOD), catalase, and glutathione peroxidase (GPx) in the ascites cell line, metastatic tumor cell line, MIA PaCa-2 primary pancreatic cancer cell line, and the Capan-1, a metastatic pancreatic cancer cell line. Cell growth, plating efficiency, growth in soft agar and growth in nude mice were determined in the ascites, metastatic tumor, and MIA PaCa-2 cell lines. MnSOD, CuZnSOD, and GPx protein and activity were increased in the ascites, metastatic tumor, and Capan-1 cell lines compared to MIA PaCa-2. The ascites and metastatic tumor cell lines had decreased cell growth, plating efficiency, and growth in soft agar, but the ascites cell line had increased cell growth in 4 and 1% O(2) concentrations in vitro and more rapid growth in vivo. Metastatic disease is associated with changes in the content and activity of antioxidant enzymes with an associated change in growth characteristics depending on the O(2) concentrations.

Inhibition of MDA-MB-231 cell cycle progression and cell proliferation by C-2-substituted oestradiol mono- and bis-3-O-sulphamates

A natural metabolite of oestradiol (E2), 2-methoxyoestradiol (2-MeOE2), exerts both antitumour and antiangiogenic effects. 2-MeOE2 is currently in clinical trials for the treatment of a variety of cancers. We have previously shown that a number of sulphamoylated analogues of 2-MeOE2 possess enhanced potency and bioavailability with respect to 2-MeOE2. In our study, the effects of C-2-substituted E2 derivatives, with sulphamoylation at the C-3 and/or C-17 position, on ERalpha -ve MDA-MB-231 breast cancer cells were evaluated. Sulphamoylated derivatives were potent inhibitors of cell proliferation, and these effects were irreversible when compared to growth inhibitory effects induced by 2-MeOE2. Cell cycle analysis suggested that these derivatives caused cells to arrest at the G2-M phase of the cell cycle. Sulphamoylated analogues suppressed the clonogenic potential of MDA-MB-231 cells and also their growth on Matrigel culture substratum. Immunofluorescence studies showed fragmented nuclear bodies and an abnormal microtubule cytoskeleton in cells exposed to one of the potent compounds, 2-MeOE2-bis-sulphamate. In addition, these analogues induced phosphorylation of BCL-2, a protein considered to be the guardian of microtubule integrity. In each of the assays, the sulphamoylated derivatives were at least 10-fold more potent than the parent compound 2-MeOE2. In view of the enhanced potencies associated with sulphamoylated E2 derivatives in ERalpha -ve cells, these analogues should hold considerable therapeutic potential for the treatment of hormone-independent breast cancers.

2-Methoxyestradiol-induced apoptosis in human leukemia cells proceeds through a reactive oxygen species and Akt-dependent process

The effects of 2-Methoxyestradiol (2ME)-induced apoptosis was examined in human leukemia cells (U937 and Jurkat) in relation to mitochondrial injury, oxidative damage, and perturbations in signaling pathways. 2ME induced apoptosis in these cells in a dose-dependent manner associated with release of mitochondrial proteins (cytochrome c, AIF), generation of reactive oxygen species (ROS), downregulation of Mcl-1 and XIAP, and inactivation (dephosphorylation) of Akt accompanied by activation of JNK. In these cells, enforced activation of Akt by a constitutively active myristolated Akt construct prevented 2ME-mediated mitochondrial injury, XIAP and Mcl-1 downregulation, JNK activation, and apoptosis, but not ROS generation. Conversely, 2ME lethality was potentiated by the phosphatidylinositol 3-kinase (PI3K) inhibitor LY294002. Furthermore, in U937 cells, the hydrogen peroxide scavenger catalase and a superoxide dismutase (SOD) mimetic, TBAP, blocked these events, as well as Akt inactivation. Interruption of the JNK pathway by pharmacologic or genetic (e.g. siRNA) means attenuated 2ME-induced mitochondrial injury, XIAP and Mcl-1 downregulation, and apoptosis. Collectively, these findings suggest a hierarchical model of 2ME-related apoptosis induction in human leukemia cells in which 2ME-induced oxidative injury represents a primary event resulting in Akt inactivation, leading, in turn, to JNK activation, and culminating in XIAP and Mcl-1 downregulation, mitochondrial injury, and apoptosis. They also suggest that in human leukemia cells, the Akt pathway plays a critical role in mediating the response to oxidative stress induced by 2ME.

Inhibition of VEGF receptors significantly impairs mammary cancer growth in C3(1)/Tag transgenic mice through antiangiogenic and non-antiangiogenic mechanisms

Cancer growth and progression is often critically influenced by the production of vascular endothelial growth factor (VEGF), a key mediator of angiogenesis. VEGF produced by tumor cells stimulates endothelial cell growth through the binding and activation of the KDR/Flk-1 receptor (VEGFR-2) on endothelial cells. Recently, some human breast cancer epithelial cells have been shown to express VEGF receptors, suggesting a potential autocrine-mediated growth stimulation of a subset of cancers by VEGF. We demonstrate that mammary tumors in the C3(1)/Tag transgenic model express VEGF and VEGF receptors and tumor growth is stimulated by this autocrine mechanism. GW654652, an indazolylpyrimidine, is a VEGFRs tyrosine kinase inhibitor that dramatically reduces both angiogenesis and tumor cell growth in this model, as demonstrated using both in vitro and in vivo assays. GW654652 significantly decreased cell proliferation and induced apoptosis in human umbilical vein endothelial cells and M6 mammary tumor cells derived from C3(1)/Tag (Tag: simian virus 40 T-antigen) transgenic mice. A 75% reduction in VEGF-induced angiogenesis was observed with GW654652 using the chick chorioallantoic membrane assay, whereas GW654652 produced an approximately 85% reduction in angiogenesis as assessed by the Matrigel plug assay. A profound inhibitory effect on tumor growth in the C3(1)/Tag transgenic model of human breast cancer was observed with oral administration of GW654652 as measured by delayed tumor onset, decreased multiplicity, reduced tumor volume, and extended animal survival. The antitumor effects of GW654652 were associated with reduced tumor vascularization and no apparent toxicity. Tumor growth, however, rapidly advanced following cessation of treatment. This is the first demonstration that a VEGF receptor inhibitor, GW654652, has a strong inhibitory effect on angiogenesis and tumor progression in a transgenic model of mammary cancer, suggesting that this is a useful approach for preclinical testing of such agents.

New insights into 2-methoxyestradiol, a promising antiangiogenic and antitumor agent

PURPOSE OF REVIEW

2-Methoxyestradiol (2ME2) is a natural metabolite of estradiol with antiangiogenic and antitumor activities. The ability of 2ME2 to target both tumor cells and neovasculature in preclinical models led to ongoing evaluations of 2ME2 in clinical trials. This brief review focuses on recent progress with 2ME2, specifically the effectiveness of 2ME2 in diverse tumor types, new mechanistic information that clarifies the multiple cellular effects of 2ME2, and the identification of promising 2ME2 analogues.

RECENT FINDINGS

New preclinical data show that 2ME2 has a broader spectrum of antitumor activities than first anticipated and suggest that 2ME2 may have utility in treating multiple myeloma, sarcoma, and other solid tumors. The mechanisms of action of 2ME2 are complex and still unclear. Recent mechanistic studies indicate that the pleiotropic activities of 2ME2 are not mediated through alpha and beta estrogen receptors. 2ME2's actions are mediated through inhibition of the proangiogenic transcription factor hypoxia-inducible factor 1 alpha, c-Jun NH2-terminal kinase signaling, and the generation of reactive oxygen species. Both the intrinsic and extrinsic apoptotic pathways are initiated by 2ME2. Although the relative roles of each pathway vary with specific cell types, this may help explain 2ME2's wide spectrum of activity.

SUMMARY

In summary, preclinical studies continue to provide enthusiasm for 2ME2 as a broad-spectrum agent. New data help resolve the roles of the diverse cellular effects of 2ME2 including microtubule disruption, initiation of signal transduction pathways, and generation of reactive oxygen species, which culminate in induction of apoptosis. 2ME2 analogues with superior properties have been identified and may provide opportunities for second-generation drugs.

N-Acetyl-l-cysteine Enhances Apoptosis through Inhibition of Nuclear Factor-κB in Hypoxic Murine Embryonic Fibroblasts

In this study, we investigated the role of reduced glutathione (GSH) and nuclear factor-kappaB (NFkappaB) in hypoxia-induced apoptosis. Hypoxia caused p53-dependent apoptosis in murine embryonic fibroblasts transfected with Ras and E1A. N-Acetyl-l-cysteine (NAC) but not other antioxidants, such as the vitamin E analog trolox and epigallocatechin-3-gallate, enhanced hypoxia-induced caspase-3 activation and apoptosis. NAC also enhanced hypoxia-induced apoptosis in two human cancer cell lines, MIA PaCa-2 pancreatic cancer cells and A549 lung carcinoma cells. In murine embryonic fibroblasts, all three antioxidants blocked hypoxia-induced reactive oxygen species formation. NAC did not enhance hypoxia-induced cytochrome c release but did enhance poly-(ADP ribose) polymerase cleavage, indicating that NAC acted at a post-mitochondrial level. NAC-mediated enhancement of apoptosis was mimicked by incubating cells with GSH monoester, which increased intracellular GSH similarly to NAC. Hypoxia promoted degradation of an inhibitor of kappaB(IkappaBalpha), NFkappaB-p65 translocation into the nucleus, NFkappaB binding to DNA, and subsequent transactivation of NFkappaB, which increased X chromosome-linked inhibitor of apoptosis protein levels. NAC failed to block degradation by IkappaBalpha and sequestration of the p65 subunit of NFkappaB to the nucleus. However, NAC did abrogate hypoxia-induced NFkappaB binding to DNA, NFkappaB-dependent gene expression, and induction of X chromosome-linked inhibitor of apoptosis protein. In conclusion, NAC enhanced hypoxic apoptosis by a mechanism apparently involving GSH-dependent suppression of NFkappaB transactivation.

In vitroandin vivoantitumor effect of 2-methoxyestradiol on human melanoma

2-methoxyestradiol (2ME(2)) is an endogenous metabolite of estradiol with estrogen-receptor-independent antitumor and antiangiogenic activity. We examined the effects of 2ME(2) on the cellular proliferation of 8 human melanoma cell lines. We show that 2ME(2) inhibited cell proliferation by inducing apoptosis and an arrest in the G(2)/M phase, and the mechanism of action involved microtubules, mitochondrial damage and caspase activation. In male SCID mice, 2ME(2) was effective in reducing primary tumor weight and the number of liver metastases after intrasplenic injection of human melanoma cells. In the metastases, we found a significantly higher rate of apoptotic cells after 2ME(2) treatment. These findings on the antitumor effect of 2ME(2) in cell culture as well as in an animal model may have implications for designing alternative treatment options for patients with advanced malignant melanoma.

2-Methoxyestradiol exhibits a biphasic effect on VEGF-A in tumor cells and upregulation is mediated through ER-alpha: a possible signaling pathway associated with the impact of 2-ME2 on proliferative cells

2-Methoxyestradiol (2-ME2) was reported to elicit both stimulation and inhibition of tumor angiogenesis and growth depending on the dosage used. However, the mechanism(s) of the biphasic action of 2-ME2 has been elusive. Here we describe a regulatory role of vascular endothelial growth factor-A (VEGF-A) in the biphasic effects on estrogen receptor (ER)+ GH3 rat pituitary tumor cells and MCF-7 human breast tumor cells depending on the dosage of 2-ME2 used. We observed that acute exposure to 2-ME2, irrespective of dosage, did not alter cellular proliferation, but enhanced the VEGF-A mRNA level. As the treatment duration increased, biphasic effect was elicited. A concentration of 1 microM 2-ME2 increased both cell proliferation and VEGF-A levels in these cells, whereas higher doses exhibited reversed impact. A low dose of 2-ME2 also increased the VEGF-A mRNA expression in ER-alpha-transfected human mammary epithelial cells (HMECs). The effect was reversed in ER- cells. The enhanced expression of VEGF-A mRNA could be blocked by the pure estrogen antagonist, ICI 182,780, and reveal that the upregulation of VEGF-A expression by 2-ME2 is mediated through ER-alpha. Furthermore, the biphasic effect of 2-ME2 on cell proliferation can be modulated by administrating VEGF-A antibodies or VEGF-A proteins. Studies also demonstrate that the VEGF-A protein, induced by 2-ME2, is functionally active and upregulates the proliferation of adjacent endothelial cells.

Mechanism of action of 2-methoxyestradiol: new developments

2-Methoxyestradiol (2ME2) is an endogenous metabolite of estrogen that has both antiangiogenic and antitumor effects. In preclinical models, 2ME2 showed promising activity that led to its clinical development as an orally active, small-molecule inhibitor of angiogenesis. Initial results suggest that 2ME2 is well tolerated and several Phase I and II clinical trials are evaluating 2ME2 in multiple tumor types. While many studies over the past 10 years have increased our understanding of how 2ME2 exerts its pleiotropic effects, its molecular mechanisms of action are not yet clear. Recent data have shown that 2ME2 inhibits HIF-1alpha, a key angiogenic transcription factor. The ability of 2ME2 to inhibit HIF-1alpha correlates with its microtubule-depolymerizing effects. The extrinsic and intrinsic pathways of apoptosis and reactive oxygen species are involved in apoptosis initiated by 2ME2; the relative contribution of each pathway appears to vary depending on the cell type. This review focuses on papers published within the past 2 years up to September 2003 that provide significant new insights into how 2ME2 exerts its diverse effects.

Concentration-dependent mitogenic and antiproliferative actions of 2-methoxyestradiol in estrogen receptor-positive human breast cancer cells

We compared in this study the effects of 2-methoxyestradiol (2-MeO-E(2)) on the growth of two estrogen receptor (ER)-negative human breast cancer cell lines (MDA-MB-231 and MDA-MB-435s) and two ER-positive human breast cancer cell lines (MCF-7 and T-47D). 2-MeO-E(2) exerted a concentration-dependent antiproliferative action in the ER-negative MDA-MB-231 and MDA-MB-435s cells. The presence or absence of exogenous 17beta-estradiol (E(2)) in the culture medium did not affect the potency and efficacy of 2-MeO-E(2)'s antiproliferative action in these ER-negative cells. When the ER-positive MCF-7 and T-47D cells were cultured in a medium supplemented with 10nM of exogenous E(2), 2-MeO-E(2) at 750 nM to 2 microM concentrations exerted a similar antiproliferative effect. However, when the ER-positive cell lines were cultured in the absence of exogenous E(2), 2-MeO-E(2) at relatively low concentrations (10-750 nM) had a moderate mitogenic effect, with its apparent efficacy 75-80% of that of E(2). This mitogenic effect of 2-MeO-E(2) was ER-mediated and largely attributable to 2-MeO-E(2)'s residual estrogenic activity on the basis of our following findings: (i) its effect was only manifested in the ER-positive cells but not in the ER-negative cells; (ii) its effect in the ER-positive cells was partially or fully abolished when exogenous E(2) was concomitantly present in the culture medium; (iii) 2-MeO-E(2) retained 1-2% of E(2)'s binding affinity for the human ERalpha and ERbeta, and its mitogenic effect was inhibited in a concentration-dependent manner by ICI-182,780, a pure ER antagonist; and (iv) its effect was not due to its metabolic conversion to 2-hydroxyestradiol. Our timely findings are of importance to the on-going clinical trials designed to evaluate 2-MeO-E(2)'s effectiveness for the treatment of different types (ER-positive or ER-negative) of human breast cancer. This knowledge will improve the design of clinical trials as well as the interpretation of clinical outcomes when 2-MeO-E(2) is used as a single agent therapy or as part of a combination therapy for human breast cancer.

2-methoxyestradiol induces caspase-independent, mitochondria-centered apoptosis in DS-sarcoma cells

The anti-cancer potential of the natural estrogen metabolite 2-methoxyestradiol is associated with microtubuli interaction, anti-angiogenetic effects and inhibition of superoxide dismutase leading to apoptosis. The effectors of apoptotic signaling through 2-methoxyestradiol, however, are cell type-dependent. We investigated the effect of 2-methoxyestradiol on several events associated with apoptosis in rat DS-sarcoma cells. Translocation of the pro-apoptotic protein Bax to mitochondria was identified as an initial apoptotic event that was accompanied by a decrease in mitochondrial transmembrane potential and the formation of reactive oxygen species (ROS) followed by mitochondrial release of apoptosis inducing factor and endonuclease G. In addition, 2-methoxyestradiol treatment caused upregulation of death receptor ligands FasL and TNFalpha and induced caspase-8 activation. The pan caspase inhibitor Z-VAD-FMK did not suppress apoptotic cell death, however, indicating that the major pro-apoptotic effect of 2-methoxyestradiol is mediated by a caspase-independent mechanism. Furthermore, ROS do not seem to play a pivotal role in the toxic/apoptotic effect of 2-methoxyestradiol in DS-sarcoma cells because supplementation with various antioxidants provided only limit protection. Colony formation was not affected by antioxidants. Therefore, in DS-sarcoma cells, the breakdown of mitochondrial integrity with the subsequent release of mitochondrial nucleases is the main factor in 2-methoxyestradiol mediated cell death.

Neuroprotective and neurotoxic effects of estrogens

The ovarian hormone 17beta-estradiol (E2) is neuroprotective in animal models of neurodegenerative diseases. Some studies suggest that the neuroprotective effects of 17beta-estradiol are a consequence of its antioxidant activity that depend on the hydroxyl group in the C3 position of the A ring. As in other tissues, 17beta-estradiol is metabolized in the brain to 2-hydroxyestradiol (2OHE2) and 2-methoxyestradiol (2MEOHE2). These two molecules present the hydroxyl group in the A ring and have a higher antioxidant activity than 17beta-estradiol. To test the hypothesis that conversion to 2-hydroxyestradiol and 2-methoxyestradiol may mediate neuroprotective actions of 17beta-estradiol in vivo, we have assessed whether these molecules protect hilar hippocampal neurons from kainic acid toxicity. Ovariectomized Wistar rats received an i.p. injection of 1, 10 or 100 microg 17beta-estradiol, 2-hydroxyestradiol or 2-methoxyestradiol followed by an i.p. injection of kainic acid (7 mg/kg) or vehicle. Treatment with kainic acid resulted in a significant loss of hilar neurons. Only the highest dose tested of 17beta-estradiol (100 microg/rat) prevented kainic acid-induced neuronal loss. 2-Hydroxyestradiol and 2-methoxyestradiol did not protect hilar neurons from kainic acid, suggesting that the mechanism of neuroprotection by 17beta-estradiol in vivo is not mediated by its metabolism to catecholestrogens or methoxycatecholestrogens. Furthermore, 2-methoxyestradiol (100 microg/rat), by itself, resulted in a significant neuronal loss in the hilus that was detected 96 h after the treatment with the steroid. This finding suggests that endogenous metabolism of 17beta-estradiol to 2-methoxyestradiol may counterbalance the neuroprotective effects of the hormone.

Red oil A5 inhibits proliferation and induces apoptosis in pancreatic cancer cells

AIM: To study the effect of red oil A5 on pancreatic cancer cells and its possible mechanisms.

METHODS: Effect of different concentrations of red oil A5 on proliferation of three pancreatic cancer cell lines, AsPC-1, MiaPaCa-2 and S2013, was measured by ³H-methyl thymidine incorporation. Time-dependent effects of 1:32 000 red oil A5 on proliferation of three pancreatic cancer cell lines, were also measured by ³H-methyl thymidine incorporation, and Time-course effects of 1:32 000 red oil A5 on cell number. The cells were counted by Z1-Coulter Counter. Flow-cytometric analysis of cellular DNA content in the control and red oil A5 treated AsPC-1, MiaPaCa-2 and S2013 cells, were stained with propidium iodide. TUNEL assay of red oil A5-induced pancreatic cancer cell apoptosis was performed. Western blotting of the cytochrome c protein in AsPC-1, MiaPaCa-2 and S2013 cells treated 24 hours with 1:32 000 red oil A5 was performed. Proteins in cytosolic fraction and in mitochondria fraction were extracted. Proteins extracted from each sample were electrophoresed on SDS-PAGE gels and then were transferred to nitrocellulose membranes. Cytochrome c was identified using a monoclonal cytochrome c antibody. Western blotting of the caspase-3 protein in AsPC-1, MiaPaCa-2 and S2013 cells treated with 1:32 000 red oil A5 for 24 hours was carried out. Proteins in whole cellular lysates were electrophoresed on SDS-PAGE gels and then transferred to nitrocellulose membranes. Caspase-3 was identified using a specific antibody. Western blotting of poly-ADP ribose polymerase (PARP) protein in AsPC-1, MiaPaCa-2 and S2013 cells treated with 1:32 000 red oil A5 for 24 hours was performed. Proteins in whole cellular lysates were separated by electrophoresis on SDS-PAGE gels and then transferred to nitrocellulose membranes. PARP was identified by using a monoclonal antibody.

RESULTS: Red oil A5 caused dose- and time-dependent inhibition of pancreatic cancer cell proliferation. Propidium iodide DNA staining showed an increase of the sub-G0/G1 cell population. The DNA fragmentation induced by red oil A5 in these three cell lines was confirmed by the TUNEL assay. Furthermore, Western blotting analysis indicated that cytochrome c was released from mitochondria to cytosol during apoptosis, and caspase-3 was activated following red oil A5 treatment which was measured by procaspase-3 cleavage and PARP cleavage.

CONCLUSION: These findings show that red oil A5 has potent anti-proliferative effects on human pancreatic cancer cells with induction of apoptosis in vitro.

Restoration of silenced Peutz-Jeghers syndrome gene, LKB1, induces apoptosis in pancreatic carcinoma cells

Germ line mutations of the LKB1 tumor suppressor gene lead to Peutz-Jeghers syndrome (PJS) with a predisposition to cancer. Previous reports suggest that inactivation of this tumor-suppressor gene plays a role in the pathogenesis of gastrointestinal hamartomas as well as several cancers, including adenocarcinoma of the pancreas. Here, we have shown that LKB1 gene is silenced in the pancreatic cancer cell line AsPC-1, but can be recovered by treatment with the methylation inhibitor, 5-aza-2'-deoxycytidine (5aza2dC). Restoring the level of LKB1 through gene transfer initiated mitochondria-mediated apoptosis in AsPC-1 cells, as evidenced by the release of cytochrome c from the mitochondria. By confocal microscopy as well as biochemical fractionation, we demonstrate that LKB1 is present in the nuclear and mitochondrial compartments of pancreatic cancer cells. Our observations also indicate that although functional p53 is absent, the p53 kin, p73, is inducible by doxorubicin in AsPC-1 cells. This suggests that LKB1-induced apoptosis is p53 independent but might be p73-mediated in the pancreatic tumor cell line, AsPC-1.

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

The Ewing sarcoma is the second most common bone tumor in children and young adults. Despite the advances in therapy, the 5-year survival rate for patients with metastatic disease is poor, indicating the need for alternative treatments. Here, we report that 2-methoxy-estradiol (2-Me), a natural estrogen metabolite, induced a caspase-dependent apoptosis of Ewing sarcoma-derived cells independently of their p53 status. 2-Me-induced apoptosis occurred through the mitochondrial death pathway as evidenced by reduction of the mitochondrial transmembrane potential, cytochrome c release and caspase-9 activation. Treatment of cells with 2-Me resulted in generation of intracellular H(2)O(2), which occurred earlier than caspase-9 activation. The H(2)O(2)-reducing agent Ebselen and the lipid peroxidation inhibitor vitamin E decreased both 2-Me-induced caspase-9 activation and cell death, thus providing evidence for a role of H(2)O(2) and lipid peroxides in the initiation of this process. Rotenone, an inhibitor of the mitochondrial respiratory chain, abolished both apoptosis and H(2)O(2) production, thereby identifying mitochondria as the source of H(2)O(2). Moreover, we observed that treatment of cells with 2-Me or H(2)O(2) induced activation of the c-Jun N-terminal kinase (JNK). Overexpression of a dominant-negative mutant of JNK1 reduced 2-Me-induced apoptosis indicating that JNK participates in this process. Altogether, our results provide evidence that 2-Me triggers apoptosis of Ewing sarcoma cells through induction of a mitochondria redox-dependent mechanism and suggest that this compound or other agents that selectively increase the level of reactive oxygen species may prove useful to the development of novel strategies for treatment of Ewing tumors.

Identification of genes regulated by 2-methoxyestradiol (2ME2) in multiple myeloma cells using oligonucleotide arrays

Our previous study demonstrated that 2-methoxyestradiol (2ME2), an estrogen derivative, induces apoptosis in multiple myeloma (MM) cells; however, the related transcriptional events are unclear. In the present study, we used oligonucleotide microarrays to identify genes altered during 2ME2-induced apoptosis in MM cells. 2ME2 triggers an early transient induction of genes known to trigger cell death and repression of growth/survival-related genes. Many genes regulating cell defense/repair machinery also were transiently induced. Since 2ME2 also induces apoptosis in MM cells resistant to conventional therapies such as dexamethasone (Dex), we compared the gene profiles of 2ME2-treated and Dex-resistant MM cells. Our results suggest that 2ME2 overcomes Dex resistance by modulating genes that confer chemoresistance in MM cells. Microarray results were confirmed by Northern and Western blot analyses. A comparative analysis of selected genes from freshly isolated MM patient cells and 2ME2-treated MM.1S MM cells further provides an in vivo relevance of our in vitro studies. Collectively, these findings suggest genetic events mediating anti-MM activity of 2ME2, as well as mechanisms whereby 2ME2 overcomes Dex resistance in MM cells. These studies may therefore allow improved therapeutic use of 2ME2, based upon targeting genes that regulate MM cell growth and survival.

Identification of a novel Bcl-xL phosphorylation site regulating the sensitivity of taxol- or 2-methoxyestradiol-induced apoptosis

Bcl-xL, a close homolog of Bcl2, is an important regulator of apoptosis and is overexpressed in human cancer. Phosphorylation of Bcl-xL can be induced by microtubule-damaging drugs such as taxol or 2-methoxyestradiol (2-ME). By site-directed mutagenesis studies, we have identified that serine 62 is the necessary site for taxol- or 2-ME-induced Bcl-xL phosphorylation in prostate cancer cells. Further studies with the inhibitor of Jun kinase (JNK) and phosphorylation null mutant of Bcl-xL reveal the augmentative role of JNK-mediated Bcl-xL phosphorylation in apoptosis of prostate cancer cells. In summary, our studies suggest that the phosphorylation of Bcl-xL by stress response kinase signaling might oppose the anti-apoptotic function of Bcl-xL to permit prostate cancer cells to die by apoptosis.