Dependency of 2-methoxyestradiol-induced mitochondrial apoptosis on mitotic spindle network impairment and prometaphase arrest in human Jurkat T cells

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

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

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

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

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

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

G1 Cell Cycle Arrest and Extrinsic Apoptotic Mechanisms Underlying the Anti-Leukemic Activity of CDK7 Inhibitor BS-181

Simple Summary

Chemotherapy resistance in human T-cell acute lymphoblastic leukemia (T-ALL), an aggressive neoplasm, results in poor prognosis despite advances in treatment modalities. Toward the identification of an effective alternative, in the present study, we elucidated the mechanism underlying the antitumor activity of the CDK7 inhibitor BS-181 using malignant cells (Jurkat A3, U937, and HeLa) and normal human peripheral T cells. This is the first report to demonstrate that BS-181 antitumor activity is mainly caused by extrinsic apoptosis induction through cell-surface TRAIL/DR5 levels in human T-ALL Jurkat T cells. Moreover, combined treatment with recombinant TRAIL (rTRAIL) exerted synergistic effects on BS-181 cytotoxicity against malignant cells but not normal human peripheral T cells by augmenting both the extrinsic and intrinsic BCL-2-sensitive apoptosis pathways. Our findings suggest that the combination with rTRAIL may facilitate BS-181 antitumor activity against T-ALL cells while minimizing associated side effects, therefore potentially being applicable to clinical human T-ALL treatment.

Abstract

In vitro antitumor activity of the CDK7 inhibitor BS-181 against human T-ALL Jurkat cells was determined. Treatment of Jurkat clones (JT/Neo) with BS-181 caused cytotoxicity and several apoptotic events, including TRAIL/DR4/DR5 upregulation, c-FLIP down-regulation, BID cleavage, BAK activation, ΔΨ_m loss, caspase-8/9/3 activation, and PARP cleavage. However, the BCL-2-overexpressing Jurkat clone (JT/BCL-2) abrogated these apoptotic responses. CDK7 catalyzed the activating phosphorylation of CDK1 (Thr161) and CDK2 (Thr160), and CDK-directed retinoblastoma phosphorylation was attenuated in both BS-181-treated Jurkat clones, whereas only JT/BCL-2 cells exhibited G₁ cell cycle arrest. The G₁-blocker hydroxyurea augmented BS-181-induced apoptosis by enhancing TRAIL/DR4/DR5 upregulation and c-FLIP down-regulation. BS-181-induced FITC–annexin V-positive apoptotic cells were mostly in the sub-G₁ and G₁ phases. BS-181-induced cytotoxicity and mitochondrial apoptotic events (BAK activation/ΔΨ_m loss/caspase-9 activation) in Jurkat clones I2.1 (FADD-deficient) and I9.2 (caspase-8-deficient) were significantly lower than in A3 (wild-type). Exogenously added recombinant TRAIL (rTRAIL) markedly synergized BS-181-induced apoptosis in A3 cells but not in normal peripheral T cells. The cotreatment cytotoxicity was significantly reduced by the DR5-blocking antibody but not by the DR4-blocking antibody. These results demonstrated that the BS-181 anti-leukemic activity is attributed to extrinsic TRAIL/DR5-dependent apoptosis preferentially induced in G₁-arrested cells, and that BS-181 and rTRAIL in combination may hold promise for T-ALL treatment.

Concise synthesis of 2-methoxyestradiol through C(sp2)-H methoxylation

An efficient and concise synthesis of 2-methoxyestradiol (4) from 17β-estradiol (1) has been achieved in three synthetic steps with a 63.3% overall yield. The key step was the palladium-catalyzed direct C(sp²)-H methoxylation of 2-aryloxypyridines. Using 2-pyridyloxyl as the directing group, Pd(OAc)₂ as the catalyst, PhI(OAc)₂ as the oxidant and methanol as both the methoxylation reagent and solvent, the methoxy group could be handily installed at the 2-position of 3-(2-pyridoxy) estradiol (2). Subsequently, the pyridyl group could be easily removed by nucleophilic substitution with a methoxy anion after being oxidized to a pyridyl N-oxide by m-chloroperoxybenzoic acid, delivering the target product 2-methoxyestradiol (4) in quantitative yield. In contrast, when the pyridyl directing group was removed by the TfOMe-NaOMe/MeOH system as reported in the literature, TfOMe inevitably methylated the 17-OH of 2-methoxy-3-(2-pyridoxy) estradiol (3). In effect, we have fortuitously found a new method to cleave the pyridyl directing group, which is highly suitable for substrates bearing hydroxy groups.

Digitoxin inhibits proliferation of multidrug-resistant HepG2 cells through G2/M cell cycle arrest and apoptosis

Hepatocellular carcinoma (HCC) remains a challenge in the medical field due to its high malignancy and mortality rates particularly for HCC, which has developed multidrug resistance. Therefore, the identification of efficient chemotherapeutic drugs for multidrug resistant HCC has become an urgent issue. Natural products have always been of significance in drug discovery. In the present study, a cell-based method was used to screen a natural compound library, which consisted of 78 compounds, and the doxorubicin-resistant cancer cell line, HepG2/ADM, as screening tools. The findings of the present study led to the shortlisting of one of the compounds, digitoxin, which displayed an inhibitory effect on HepG2/ADM cells, with 50% inhibitory concentration values of 132.65±3.83, 52.29±6.26, and 9.13±3.67 nM for 24, 48, and 72 h, respectively. Immunofluorescence, western blotting and cell cycle analyses revealed that digitoxin induced G₂/M cell cycle arrest via the serine/threonine-protein kinase ATR (ATR)-serine/threonine-protein kinase Chk2 (CHK2)-M-phase inducer phosphatase 3 (CDC25C) signaling pathway in HepG2/ADM cells, which may have resulted from a DNA double-stranded break. Digitoxin also induced mitochondrial apoptosis, which was characterized by changes in the interaction between Bcl-2 and Bax, the release of cytochrome c, as well as the activation of the caspase-3 and −9. To the best of our knowledge, the present study is the first report that digitoxin displays an anti-HCC effect on HepG2/ADM cells through G₂/M cell cycle arrest, which was mediated by the ATR-CHK2-CDC25C signaling pathway and mitochondrial apoptosis. Therefore, digitoxin could be a promising chemotherapeutic agent for the treatment of patients with HCC.

Concise synthesis of 2-methoxyestradiol from 17β-estradiol through the C(sp2)-H hydroxylation

A four-step route for the synthesis of 2-methoxyestradiol (5) starting from 17β-estradiol (1) has been achieved with a 51% overall yield. The key step was the ruthenium-catalyzed ortho-C(sp²)-H bond hydroxylation of aryl carbamates. Using dimethyl carbamate as the directing group, [RuCl₂(p-cymene)]₂ as the catalyst, PhI(OAc)₂ as the oxidant and trifluoroacetate/trifluoroacetic anhydride (1:1) as the co-solvent, the hydroxyl group could be singly installed at the 2-position of 3-dimethylcarbamoyloxyestradiol (2) with 65% yield. Subsequent methylation of hydroxy and removal of dimethyl carbamate afforded 2-methoxyestradiol (5).

Cytoprotective effect of 2-carbomethoxy-2,3-epoxy-3-prenyl-1,4-naphthoquinone (CMEP-NQ) is mediated by the inhibition of BAK-dependent mitochondrial apoptosis pathway

The inhibitory mechanism of 2-carbomethoxy-2,3-epoxy-3-prenyl-1,4-naphthoquinone (CMEP-NQ) against apoptosis induced by the microtubule-damaging agents (MDAs), nocodazole (NOC) and 2-methoxyestradiol (2-MeO-E₂), or a DNA-damaging agent (DDA), camptothecin (CPT) were investigated in human Jurkat T cell clones (J/Neo and J/BCL-XL cells). Treatment of J/Neo cells with NOC, 2-MeO-E₂, or CPT caused cytotoxicity and apoptotic DNA fragmentation but these events were significantly attenuated in the presence of CMEP-NQ. Although not only MDA (NOC or 2-MeO-E₂)-induced mitotic arrest, CDK1 activation, and BCL-2, BCL-XL and BIM phosphorylation, but also DDA (CPT)-induced S-phase arrest and ATM-CHK1/CHK2-p53 pathway activation were not or were barely affected in the presence of CMEP-NQ, the levels of anti-apoptotic BAG3 and MCL-1, which were markedly downregulated after MDA- or DDA-treatment, were rather elevated by CMEP-NQ. Under the same conditions, MDA- or DDA-induced mitochondrial apoptotic events including BAK activation, mitochondrial membrane potential (Δψm) loss, caspase-9 activation, and PARP cleavage were significantly inhibited by CMEP-NQ. While MDA- or DDA-induced sub-G₁ peak and Δψm loss were abrogated in J/BCL-XL cells, MDA-induced mitotic arrest and DDA-induced S-arrest were more apparent in J/BCL-XL cells than in J/Neo cells. Simultaneously, the induced cell cycle arrest in J/BCL-XL cells was not significantly disturbed by CMEP-NQ. MDA- or DDA-treatment caused intracellular reactive oxygen species (ROS) production; however, MDA- or DDA-induced ROS production was almost completely abrogated in J/BCL-XL cells. MDA- or DDA-induced ROS production in J/Neo cells was significantly suppressed by CMEP-NQ, but the suppressive effect was hardly observed in J/BCL-XL cells. Together, these results show that CMEP-NQ efficiently protects Jurkat T cells from apoptotic cell death via the elevation of BAG3 and MCL-1 levels, which results in the inhibition of intrinsic BAK-dependent mitochondrial apoptosis pathway, as does the overexpression of BCL-XL.

2-Methoxyestradiol Reverses the Pro-Carcinogenic Effect of L-Lactate in Osteosarcoma 143B Cells

BACKGROUND/AIM

According to the reverse Warburg effect, tumor cells may metabolize lactate as an energy source and shuttle L-lactate to neighboring cancer cells, adjacent stroma, and vascular endothelial cells, thus inducing metabolic reprogramming. An increased tumor L-lactate level strictly correlates with increased metastasis, tumor recurrence and a poor outcome. A potent anticancer agent that may act on L-lactate activated cells is 2-metoxyestradiol. Thus, the aim of the study was to evaluate whether a potent anticancer agent, 2-methoxyestradiol, is able to reverse L-lactate-induced metabolic reprogramming in osteosarcoma 143B cells.

MATERIALS AND METHODS

We used flow cytometry in order to determine cell death, autophagy, expression of KI-67, mitochondrial membrane depolarization. We performed cell proliferation assay in order to determine cell viability and cell migration assay to determine invasive potential of osteosarcoma cells. While, CalcuSyn software was used in order to evaluate the interaction between 2-methoxyestradiol and L-lactate.

RESULTS

We demonstrated that 2-methoxyestradiol abolished L-lactate-induced migration and proliferation of osteosarcoma cells. Moreover, we observed that this effect was associated with regulation of Ki-67 and induction of autophagy.

CONCLUSION

2-Methoxyestradiol is a potent anticancer agent also under metabolic reprogramming conditions.

Cis-trimethoxy resveratrol induces intrinsic apoptosis via prometaphase arrest and prolonged CDK1 activation pathway in human Jurkat T cells

Cis-trimethoxy resveratrol (cis-3M-RES) induced dose-dependent cytotoxicity and apoptotic DNA fragmentation in Jurkat T cell clones (JT/Neo); however, it induced only cytostasis in BCL-2-overexpressing cells (JT/BCL-2). Treatment with 0.25 μM cis-3M-RES induced G₂/M arrest, BAK activation, Δψm loss, caspase-9 and caspase-3 activation, and poly (ADP-ribose) polymerase (PARP) cleavage in JT/Neo cells time-dependently but did not induce these events, except G₂/M arrest, in JT/BCL-2 cells. Moreover, cis-3M-RES induced CDK1 activation, BCL-2 phosphorylation at Ser-70, MCL-1 phosphorylation at Ser-159/Thr-163, and BIM (BIM_EL and BIM_L) phosphorylation irrespective of BCL-2 overexpression. Enforced G₁/S arrest by using a G₁/S blocker aphidicolin completely inhibited cis-3M-RES-induced apoptotic events. Cis-3M-RES-induced phosphorylation of BCL-2 family proteins and mitochondrial apoptotic events were suppressed by a validated CDK1 inhibitor RO3306. Immunofluorescence microscopy showed that cis-3M-RES induced mitotic spindle defects and prometaphase arrest. The rate of intracellular polymeric tubulin to monomeric tubulin decreased markedly by cis-3M-RES (0.1-1.0 μM). Wild-type Jurkat clone A3, FADD-deficient Jurkat clone I2.1, and caspase-8-deficient Jurkat clone I9.2 exhibited similar susceptibilities to the cytotoxicity of cis-3M-RES, excluding contribution of the extrinsic death receptor-dependent pathway to the apoptosis. IC₅₀ values of cis-3M-RES against Jurkat E6.1, U937, HL-60, and HeLa cells were 0.07-0.17 μM, whereas those against unstimulated human peripheral T cells and phytohaemagglutinin A-stimulated peripheral T cells were >10.0 and 0.23 μM, respectively. These results indicate that the antitumor activity of cis-3M-RES is mediated by microtubule damage, and subsequent prometaphase arrest and prolonged CDK1 activation that cause BAK-mediated mitochondrial apoptosis, and suggest that cis-3M-RES is a promising agent to treat leukemia.

Effect of low doses of estradiol and tamoxifen on breast cancer cell karyotypes

Evidence supports a role of 17&-estradiol (E2) in carcinogenesis and the large majority of breast carcinomas are dependent on estrogen. The anti-estrogen tamoxifen (TAM) is widely used for both treatment and prevention of breast cancer; however, it is also carcinogenic in human uterus and rat liver, highlighting the profound complexity of its actions. The nature of E2- or TAM-induced chromosomal damage has been explored using relatively high concentrations of these agents, and only some numerical aberrations and chromosomal breaks have been analyzed. This study aimed to determine the effects of low doses of E2 and TAM (10(&8 )mol L(&1) and 10(&6 )mol L(&1) respectively) on karyotypes of MCF7, T47D, BT474, and SKBR3 breast cancer cells by comparing the results of conventional karyotyping and multi-FISH painting with cell proliferation. Estrogen receptor (ER)-positive (+) cells showed an increase in cell proliferation after E2 treatment (MCF7, T47D, and BT474) and a decrease after TAM treatment (MCF7 and T47D), whereas in ER& cells (SKBR3), no alterations in cell proliferation were observed, except for a small increase at 96 h. Karyotypes of both ER+ and ER& breast cancer cells increased in complexity after treatments with E2 and TAM leading to specific chromosomal abnormalities, some of which were consistent throughout the treatment duration. This genotoxic effect was higher in HER2+ cells. The ER&/HER2+ SKBR3 cells were found to be sensitive to TAM, exhibiting an increase in chromosomal aberrations. These in vitro results provide insights into the potential role of low doses of E2 and TAM in inducing chromosomal rearrangements in breast cancer cells.

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

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

Bakkenolide-IIIa Protects Against Cerebral Damage Via Inhibiting NF-κB Activation

AIMS

This study was designed to examine the neuroprotective effects of bakkenolide-IIIa, a major novel compound extracted from the rhizome of P. trichinous.

METHODS

Transient focal cerebral damage model in rats and oxygen-glucose deprivation (OGD) in cultured hippocampal neurons were performed. The amount of apoptotic neurons was determined using TUNEL assay. The expressions of Bcl-2, Bax, Akt, ERK1/2, IKKβ, IκBα were measured using Western blot. The nuclear translocation and activation of NF-κB was measured using a fluorescence microscope and electrophoretic mobility shift assay (EMSA).

RESULTS

Bakkenolide-IIIa (4, 8, 16 mg/kg; i.g.) was administered immediately after reperfusion could reduce the brain infarct volume, and the neurological deficit, as well as a high dose of bakkenolide-IIIa, increases the 72 h survival rate in cerebrally damaged rats. In vitro data demonstrated that bakkenolide-IIIa could increase cell viability and decrease the amount of apoptotic cells in cultured primary hippocampal neurons exposed to OGD. Bakkenolide-IIIa also dose-dependently increased the ratio of Bcl-2 to Bax. These results indicated that inhibition of apoptosis partly mediated the neuroprotection of bakkenolide-IIIa. Furthermore, bakkenolide-IIIa inhibited the phosphorylation of Akt, ERK1/2, IKKβ, IκBα, and p65 in cultured hippocampal neurons exposed to OGD. Bakkenolide-IIIa not only inhibited the nuclear translocation of NF-κB in cultured neurons exposed to OGD, but also inhibited the activation of NF-κB in peri-infarct area in cerebrally damaged rats.

CONCLUSION

Collectively, our findings indicated that bakkenolide-IIIa protects against cerebral damage by inhibiting AKT and ERK1/2 activation and inactivated NF-κB signaling.