Arsenic trioxide induces apoptosis in neuroblastoma cell lines through the activation of caspase 3 in vitro

Harness arsenic in medicine: current status of arsenicals and recent advances in drug delivery

INTRODUCTION

Arsenicals have a special place in the history of human health, acting both as poison and medicine. Having been used to treat a variety of diseases in the past, the success of arsenic trioxide (ATO) in treating acute promyelocytic leukemia (APL) in the last century marked its use as a drug in modern medicine. To expand their role against cancer, there have been clinical uses of arsenicals worldwide and progress in the development of drug delivery for various malignancies, especially solid tumors.

AREAS COVERED

In this review, conducted on Google Scholar [1977-2024], we start with various forms of arsenicals, highlighting the well-known ATO. The mechanism of action of arsenicals in cancer therapy is then overviewed. A summary of the research progress in developing new delivery approaches (e.g. polymers, inorganic frameworks, and biomacromolecules) in recent years is provided, addressing the challenges and opportunities in treating various malignant tumors.

EXPERT OPINION

Reducing toxicity and enhancing therapeutic efficacy are guidelines for designing and developing new arsenicals and drug delivery systems. They have shown potential in the fight against cancer and emerging pathogens. New technologies and strategies can help us harness the potency of arsenicals and make better products.

Pyrazole-Enriched Cationic Nanoparticles Induced Early- and Late-Stage Apoptosis in Neuroblastoma Cells at Sub-Micromolar Concentrations

Neuroblastoma (NB) is a severe form of tumor occurring mainly in young children and originating from nerve cells found in the abdomen or next to the spine. NB needs more effective and safer treatments, as the chance of survival against the aggressive form of this disease are very small. Moreover, when current treatments are successful, they are often responsible for unpleasant health problems which compromise the future and life of surviving children. As reported, cationic macromolecules have previously been found to be active against bacteria as membrane disruptors by interacting with the negative constituents of the surface of cancer cells, analogously inducing depolarization and permeabilization, provoking lethal damage to the cytoplasmic membrane, and cause loss of cytoplasmic content and consequently, cell death. Here, aiming to develop new curative options for counteracting NB cells, pyrazole-loaded cationic nanoparticles (NPs) (BBB4-G4K and CB1H-P7 NPs), recently reported as antibacterial agents, were assayed against IMR 32 and SHSY 5Y NB cell lines. Particularly, while BBB4-G4K NPs demonstrated low cytotoxicity against both NB cell lines, CB1H-P7 NPs were remarkably cytotoxic against both IMR 32 and SHSY 5Y cells (IC50 = 0.43–0.54 µM), causing both early-stage (66–85%) and late-stage apoptosis (52–65%). Interestingly, in the nano-formulation of CB1H using P7 NPs, the anticancer effects of CB1H and P7 were increased by 54–57 and 2.5–4-times, respectively against IMR 32 cells, and by 53–61 and 1.3–2 times against SHSY 5Y cells. Additionally, based on the IC50 values, CB1H-P7 was also 1-12-fold more potent than fenretinide, an experimental retinoid derivative in a phase III clinical trial, with remarkable antineoplastic and chemopreventive properties. Collectively, due to these results and their good selectivity for cancer cells (selectivity indices = 2.8–3.3), CB1H-P7 NPs represent an excellent template material for developing new treatment options against NB.

Enhancing an Oxidative "Trojan Horse" Action of Vitamin C with Arsenic Trioxide for Effective Suppression of KRAS-Mutant Cancers: A Promising Path at the Bedside

The turn-on mutations of the KRAS gene, coding a small GTPase coupling growth factor signaling, are contributing to nearly 25% of all human cancers, leading to highly malignant tumors with poor outcomes. Targeting of oncogenic KRAS remains a most challenging task in oncology. Recently, the specific G12C mutant KRAS inhibitors have been developed but with a limited clinical outcome because they acquire drug resistance. Alternatively, exploiting a metabolic breach of KRAS-mutant cancer cells related to a glucose-dependent sensitivity to oxidative stress is becoming a promising indirect cancer targeting approach. Here, we discuss the use of a vitamin C (VC) acting in high dose as an oxidative "Trojan horse" agent for KRAS-mutant cancer cells that can be potentiated with another oxidizing drug arsenic trioxide (ATO) to obtain a potent and selective cytotoxic impact. Moreover, we outline the advantages of VC's non-natural enantiomer, D-VC, because of its distinctive pharmacokinetics and lower toxicity. Thus, the D-VC and ATO combination shows a promising path to treat KRAS-mutant cancers in clinical settings.

Melatonin improves arsenic-induced hypertension through the inactivation of the Sirt1/autophagy pathway in rat

Arsenic (As), a metalloid chemical element, is classified as heavy metal. Previous studies proposed that As induces vascular toxicity by inducing autophagy, apoptosis, and oxidative stress. It has been shown that melatonin (Mel) can decrease oxidative stress and apoptosis, and modulate autophagy in different pathological situations. Hence, this study aimed to investigate the Mel effect on As-induced vascular toxicity through apoptosis and autophagy regulation. Forty male rats were treated with As (15 mg/kg; oral gavage) and Mel (10 and 20 mg/kg, intraperitoneally; i.p.) for 28 days. The systolic blood pressure (SBP) changes, oxidative stress markers, the aorta histopathological injuries, contractile and relaxant responses, the level of apoptosis (Bnip3 and caspase-3) and autophagy (Sirt1, Beclin-1 and LC3 II/I ratio) proteins were determined in rats aorta. The As exposure significantly increased SBP and enhanced MDA level while reduced GSH content. The exposure to As caused substantial histological damage in aorta tissue and changed vasoconstriction and vasorelaxation responses to KCl, PE, and Ach in isolated rat aorta. The levels of HO-1 and Nrf-2, apoptosis markers, Sirt1, and autophagy proteins also enhanced in As group. Interestingly, Mel could reduce changes in oxidative stress, blood pressure, apoptosis, and autophagy induced by As. On the other hand, Mel led to more increased the levels of Nrf-2 and HO-1 proteins compared with the As group. In conclusion, our findings showed that Mel could have a protective effect against As-induced vascular toxicity by inhibiting apoptosis and the Sirt1/autophagy pathway.

Arsenic compounds induce apoptosis by activating the MAPK and caspase pathways in FaDu oral squamous carcinoma cells

For a number of years, oral cancer has remained in the top ten most common types of cancer, with an incidence rate that is steadily increasing. In total, ~75% oral cancer cases are associated with lifestyle factors, including uncontrolled alcohol consumption, betel and tobacco chewing, and the excessive use of tobacco. Notably, betel chewing is highly associated with oral cancer in Southeast Asia. Arsenic is a key environmental toxicant; however, arsenic trioxide has been used as a medicine for the treatment of acute promyelocytic leukemia, highlighting its anticancer properties. The present study aimed to investigate the role of arsenic compounds in the treatment of cancer, using FaDu oral squamous carcinoma cells treated with sodium arsenite (NaAsO₂) and dimethyl arsenic acid (DMA). The results demonstrated that FaDu cells exhibited membrane blebbing phenomena and high levels of apoptosis following treatment with 10 µM NaAsO₂ and 1 mM DMA for 24 h. The results of cell viability assay demonstrated that the rate of FaDu cell survival was markedly reduced as the concentration of arsenic compounds increased from 10 to 100 µM NaAsO₂, and 1 to 100 mM DMA. Moreover, flow cytometry was carried out to further examine the effects of arsenic compounds on FaDu cell cycle regulation; the results revealed that treatment with NaAsO₂ and DMA led to a significant increase in the percentage of FaDu cells in the sub‑G1 and G2/M phases of the cell cycle. An Annexin V/PI double staining assay was subsequently performed to verify the levels of FaDu cell apoptosis following treatment with arsenic compounds. Furthermore, the results of the western blot analyses revealed that the expression levels of caspase‑8, ‑9 and ‑3, and poly ADP‑ribose polymerase, as well the levels of phosphorylated JNK and ERK1/2 were increased following treatment with NaAsO₂ and DMA in the FaDu cells. On the whole, the results of the present study revealed that treatment with NaAsO₂ and DMA promoted the apoptosis of FaDu oral cancer cells, by activating MAPK pathways, as well as the extrinsic and intrinsic apoptotic pathways.

Label-Free Study of the Global Cell Behavior during Exposure to Environmental Radiofrequency Fields in the Presence or Absence of Pro-Apoptotic or Pro-Autophagic Treatments

It remains controversial whether exposure to environmental radiofrequency signals (RF) impacts cell status or response to cellular stress such as apoptosis or autophagy. We used two label-free techniques, cellular impedancemetry and Digital Holographic Microscopy (DHM), to assess the overall cellular response during RF exposure alone, or during co-exposure to RF and chemical treatments known to induce either apoptosis or autophagy. Two human cell lines (SH-SY5Y and HCT116) and two cultures of primary rat cortex cells (astrocytes and co-culture of neurons and glial cells) were exposed to RF using an 1800 MHz carrier wave modulated with various environmental signals (GSM: Global System for Mobile Communications, 2G signal), UMTS (Universal Mobile Telecommunications System, 3G signal), LTE (Long-Term Evolution, 4G signal, and Wi-Fi) or unmodulated RF (continuous wave, CW). The specific absorption rates (S.A.R.) used were 1.5 and 6 W/kg during DHM experiments and ranged from 5 to 24 W/kg during the recording of cellular impedance. Cells were continuously exposed for three to five consecutive days while the temporal phenotypic signature of cells behavior was recorded at constant temperature. Statistical analysis of the results does not indicate that RF-EMF exposure impacted the global behavior of healthy, apoptotic, or autophagic cells, even at S.A.R. levels higher than the guidelines, provided that the temperature was kept constant.

Arsenic trioxide in pediatric cancer - a case series and review of literature

Arsenic trioxide (ATO) has become an established component of treatment protocols for acute promyelocytic leukemia (APL) with excellent efficacy and no relevant sustained toxicity. Part of its action has been attributed to the inhibition of Hedgehog signaling (Hh) which enables a possible therapeutic approach as many pediatric tumor entities have been associated with increased Hh activity. We retrospectively analyzed 31 patients with refractory and relapsed pediatric cancer who were treated with ATO at the University Children's Hospital of Tuebingen. Additionally a literature review on the clinical and preclinical use of ATO in pediatric cancer treatment was performed.ATO alone as well as combinations with other drugs have proven effective in vitro and in mouse models of various pediatric malignancies. However, only few data on the clinical use of ATO in pediatric patients besides APL exist. In our patient sample, ATO was overall well tolerated in the treatment of various pediatric cancers, even in combination with other cytostatic drugs. Due to distinct tumor entities, differently progressed disease stages and varying co-medication, no clear statement can be made regarding the efficacy of ATO treatment. However, patients with proven Hh activation in molecular tumor profiling surpassed all other patients, who received ATO in an experimental treatment setting, in terms of survival. As molecular profiling of tumors increases and enhanced Hh activity can be detected at an early stage, ATO might expand its clinical use to other pediatric malignancies beyond APL depending on further clinical studies.

Mechanisms underlying the protective effect of tannic acid against arsenic trioxide‑induced cardiotoxicity in rats: Potential involvement of mitochondrial apoptosis

Arsenic trioxide (ATO) is a frontline chemotherapy drug used in the therapy of acute promyelocytic leukemia. However, the clinical use of ATO is hindered by its cardiotoxicity. The present study aimed to observe the potential effects and underlying mechanisms of tannic acid (TA) against ATO-induced cardiotoxicity. Male rats were intraperitoneally injected with ATO (5 mg/kg/day) to induce cardiotoxicity. TA (20 and 40 mg/kg/day) was administered to evaluate its cardioprotective efficacy against ATO-induced heart injury in rats. Administration of ATO resulted in pathological damage in the heart and increased oxidative stress as well as levels of serum cardiac biomarkers creatine kinase and lactate dehydrogenase and the inflammatory marker NF-κB (p65). Conversely, TA markedly reversed this phenomenon. Additionally, TA treatment caused a notable decrease in the expression levels of cleaved caspase-3/caspase-3, Bax, p53 and Bad, while increasing Bcl-2 expression levels. Notably, the application of TA decreased the expression levels of cytochrome c, second mitochondria-derived activator of caspases and high-temperature requirement A2, which are apoptosis mitochondrial-associated proteins. The present findings indicated that TA protected against ATO-induced cardiotoxicity, which may be associated with oxidative stress, inflammation and mitochondrial apoptosis.

Functional Profiling Identifies Determinants of Arsenic Trioxide Cellular Toxicity

Arsenic exposure is a worldwide health concern associated with an increased risk of skin, lung, and bladder cancer but arsenic trioxide (AsIII) is also an effective chemotherapeutic agent. The current use of AsIII in chemotherapy is limited to acute promyelocytic leukemia (APL). However, AsIII was suggested as a potential therapy for other cancer types including chronic myeloid leukemia (CML), especially when combined with other drugs. Here, we carried out a genome-wide CRISPR-based approach to identify modulators of AsIII toxicity in K562, a human CML cell line. We found that disruption of KEAP1, the inhibitory partner of the key antioxidant transcription factor Nrf2, or TXNDC17, a thioredoxin-like protein, markedly increased AsIII tolerance. Loss of the water channel AQP3, the zinc transporter ZNT1 and its regulator MTF1 also enhanced tolerance to AsIII whereas loss of the multidrug resistance protein ABCC1 increased sensitivity to AsIII. Remarkably, disruption of any of multiple genes, EEFSEC, SECISBP2, SEPHS2, SEPSECS, and PSTK, encoding proteins involved in selenocysteine metabolism increased resistance to AsIII. Our data suggest a model in which an intracellular interaction between selenium and AsIII may impact intracellular AsIII levels and toxicity. Together this work revealed a suite of cellular components/processes which modulate the toxicity of AsIII in CML cells. Targeting such processes simultaneously with AsIII treatment could potentiate AsIII in CML therapy.

Oxidative damage under As3+ and/or Cu2+ stress leads to apoptosis and autophagy and may be cross-talking with mitochondrial disorders in bursa of Fabricius

Arsenic (As) exists in many forms in the whole natural environment, with As³⁺ the highest toxicity. Herein our study demonstrated that arsenic trioxide (As₂O₃) at a dose of 30 mg/kg caused serious oxidative damage to chickens' bursa of Fabricius (BF) in a time-dependent manner. Copper (Cu) is a necessary micronutrient and a key catalytic cofactor of many enzymes. We found excessive Cu (in the form of 300 mg/kg copper sulfate (CuSO₄)) also induced severe oxidative stress (OxS), and its co-exposure with As³⁺ had a greater destructive power against oxidative system. Under electron microscope, swollen mitochondria, disappeared cristae and agglutinated chromatin were observed, accompanied by myeloid structure and autophagosome. The results showed apoptosis and autophagy occurred under the action of As³⁺ and Cu²⁺, and the situation was more serious in combined exposure group, which was further explained by terminal deoxynucleotidyl transferase (TdT)-mediated 2'-Deoxyuridine 5'-Triphosphate (dUTP) Nick-End Labeling (TUNEL). By quantitative real time polymerase chain reaction (RT-qPCR) and western blot, we found that mitochondrial dynamics were disordered under OxS, and the abnormal changes of B-cell lymphoma (Bcl)-2, p53, Bcl-2-interacting protein (Beclin)-1 and autophagy-related gene (ATG) 4B indicated the crosstalk between apoptosis and autophagy. In conclusion, apoptosis and autophagy of BF induced by As³⁺ and Cu²⁺ and mitochondrial disorder are closely related to the collapse of antioxidant system, and their connections are inseparable. Our results provide a reference for environmental risk prevention and selection of poultry feed additives and pesticides to avoid the health risks caused by As³⁺ and Cu²⁺ exposure.

Sestrins as a Therapeutic Bridge between ROS and Autophagy in Cancer

The regulation of Reactive Oxygen Species (ROS) levels and the contribution therein from networks regulating cell metabolism, such as autophagy and the mTOR-dependent nutrient-sensing pathway, constitute major targets for selective therapeutic intervention against several types of tumors, due to their extensive rewiring in cancer cells as compared to healthy cells. Here, we discuss the sestrin family of proteins—homeostatic transducers of oxidative stress, and drivers of antioxidant and metabolic adaptation—as emerging targets for pharmacological intervention. These adaptive regulators lie at the intersection of those two priority nodes of interest in antitumor intervention—ROS control and the regulation of cell metabolism and autophagy—therefore, they hold the potential not only for the development of completely novel compounds, but also for leveraging on synergistic strategies with current options for tumor therapy and classification/stadiation to achieve personalized medicine.

Evaluation of phyto-medicinal efficacy of thymoquinone against Arsenic induced mitochondrial dysfunction and cytotoxicity in SH-SY5Y cells

BACKGROUND

It is evaluated that a few million individuals worldwide are experiencing Arsenic (As) harmfulness coming about because of anthropogenic discharges. There is likewise proof to propose that As can affect the peripheral, as well as, the central nervous system (CNS). On the contrary, thymoquinone (TQ), a biologically active ingredient of Nigella sativa has exhibited numerous neuro-pharmacological traits since ancient times.

HYPOTHESIS/PURPOSE

In the present study, the neuroprotective efficacy of TQ was explored by primarily studying its antioxidant and anti-apoptotic potential against Arsenic trioxide (As₂O₃) induced toxicity in SH-SY5Y human neuroblastoma cell lines.

STUDY DESIGN

For experimentation, cells were seeded in 96 well tissue culture plates and kept undisturbed for 24 h to attain proper adhesion. After 75-80% confluence, cells were pretreated with 10 µM and 20 µM thymoquinone (TQ) for 1 h After adding 2 µM As, cells were set aside for incubation for 24 h without changing the medium.

METHODS

The mitigatory effects of TQ with particular reference to cell viability and cytotoxicity, the generation of reactive oxygen species, DNA damage, and mitochondrial dynamics were studied.

RESULTS

Pretreatment of SH-SY5Y cells with TQ (10 and 20 μM) for an hour and subsequent exposure to 2 μM As₂O₃ protected the SH-SY5Y cells against the neuro-damaging effects of the latter. Also, the SH-SY5Y cells were better preserved with increased viability, repaired DNA, less free radical generation and balanced transmembrane potential than those exposed to As₂O₃ alone. TQ pretreatment also inhibited As₂O₃-induced exacerbation in protein levels of BAX and PARP-1 and restored the loss of Bcl₂ levels.

CONCLUSION

The findings of this study suggest that TQ may prevent neurotoxicity and As₂O₃-induced apoptosis and cytotoxicity. It is, therefore, worth studying further for its potential to reduce the risks of arsenic-related neurological implications.

Differential protein expression of hippocampal cells associated with heavy metals (Pb, As, and MeHg) neurotoxicity: Deepening into the molecular mechanism of neurodegenerative diseases

Chronic exposure to heavy metals such as Pb, As, and MeHg can be associated with an increased risk of developing neurodegenerative diseases. Our in vitro bioassays results showed the potency of heavy metals in the order of Pb < As < MeHg on hippocampal cells. The main objective of this study was combining in vitro label free proteomics and systems biology approach for elucidating patterns of biological response, discovering underlying mechanisms of Pb, As, and MeHg toxicity in hippocampal cells. The omics data was refined by using different filters and normalization and multilevel analysis tools were employed to explore the data visualization. The functional and pathway visualization was performed by using Gene ontology and PathVisio tools. Using these all integrated approaches, we identified significant proteins across treatments within the mitochondrial dysfunction, oxidative stress, ubiquitin proteome dysfunction, and mRNA splicing related to neurodegenerative diseases. The systems biology analysis revealed significant alterations in proteins implicated in Parkinson's disease (PD) and Alzheimer's disease (AD). The current proteomics analysis of three metals support the insight into the proteins involved in neurodegeneration and the altered proteins can be useful for metal-specific biomarkers of exposure and its adverse effects.

SIGNIFICANCE

The proteomics techniques have been claimed to be more sensitive than the conventional toxicological assays, facilitating the measurement of responses to heavy metals (Pb, As, and MeHg) exposure before obvious harm has occurred demonstrating their predictive value. Also, proteomics allows for the comparison of responses between Pb, As, and MeHg metals, permitting the evaluation of potency differences hippocampal cells of the brain. Hereby, the molecular information provided by pathway and gene functional analysis can be used to develop a more thorough understanding of each metal mechanism at the protein level for different neurological adverse outcomes (e.g. Parkinson's disease, Alzheimer's diseases). Efforts are put into developing proteomics based toxicity testing methods using in vitro models for improving human risk assessment. Some of the key proteins identified can also potentially be used as biomarkers in epidemiologic studies. These heavy metal response patterns shed new light on the mechanisms of mRNA splicing, ubiquitin pathway role in neurodegeneration, and can be useful for the development of molecular biomarkers of heavy metals exposure.

PI3K/Akt/mTOR Signaling Pathway and the Biphasic Effect of Arsenic in Carcinogenesis

Arsenic is a naturally occurring, ubiquitous metalloid found in the Earth’s crust. In its inorganic form, arsenic is highly toxic and carcinogenic and is widely found across the globe and throughout the environment. As an International Agency for Research on Cancer–defined class 1 human carcinogen, arsenic can cause multiple human cancers, including liver, lung, urinary bladder, skin, kidney, and prostate. Mechanisms of arsenic-induced carcinogenesis remain elusive, and this review focuses specifically on the role of the PI3K/AKT/mTOR pathway in promoting cancer development. In addition to exerting potent carcinogenic responses, arsenic is also known for its therapeutic effects against acute promyelocytic leukemia. Current literature suggests that arsenic can achieve both therapeutic as well as carcinogenic effects, and this review serves to examine the paradoxical effects of arsenic, specifically through the PI3K/AKT/mTOR pathway. Furthermore, a comprehensive review of current literature reveals an imperative need for future studies to establish and pinpoint the exact conditions for which arsenic can, and through what mechanisms it is able to, differentially regulate the PI3K/AKT/mTOR pathway to maximize the therapeutic and minimize the carcinogenic properties of arsenic.

Arsenic trioxide induces apoptosis and the formation of reactive oxygen species in rat glioma cells

Background

Arsenic trioxide (As₂O₃) has a dramatic therapeutic effect on acute promyelocytic leukemia (APL) patients. It can also cause apoptosis in various tumor cells. This study investigated whether As₂O₃ has an antitumor effect on glioma and explored the underlying mechanism.

Results

MTT and trypan blue assays showed that As₂O₃ remarkably inhibited growth of C6 and 9 L glioma cells. Cell viability decreased in glioma cells to a greater extent than in normal glia cells. The annexin V-FITC/PI and Hoechest/PI staining assays revealed a significant increase in apoptosis that correlated with the duration of As₂O₃ treatment and occurred in glioma cells to a greater extent than in normal glial cells. As₂O₃ treatment induced reactive oxygen species (ROS) production in C6 and 9 L cells in a time-dependent manner. Cells pretreated with the antioxidant N-acetylcysteine (NAC) showed significantly lower As₂O₃-induced ROS generation. As₂O₃ significantly inhibited the expression of the anti-apoptotic gene Bcl-2, and upregulated the proapoptotic gene Bax in both C6 and 9 L glioma cells in a time-dependent manner.

Conclusions

As₂O₃ can significantly inhibit the growth of glioma cells and it can induce cell apoptosis in a time- and concentration-dependent manner. ROS were found to be responsible for apoptosis in glioma cells induced by As₂O₃. These results suggest As₂O₃ is a promising agent for the treatment of glioma.

Arsenic trioxide-mediated suppression of miR-182-5p is associated with potent anti-oxidant effects through up-regulation of SESN2

Arsenic trioxide (ATO) is a traditional Chinese medicine that can induce oxidative stress for treatment of cancer cells. However, ATO may generate anti-oxidative responses to compromise the cytotoxic effect, but the underlying mechanisms remain unclear. Here we found that ATO could inhibit miR-182-5p expression in patient-derived primary S1 glioblastoma (GBM) cells accompanied by up-regulation of Sestrin-2 (SESN2) mRNA, a known anti-oxidant molecule. This phenomenon was also detected in a U87MG glioma cell line, human lung adenocarcinoma H1299 cell line and A549 cell line. Pretreatment with a free radical scavenger N-acetylcysteine (NAC) reduced the oxidative stress induced by ATO. Concomitantly, ATO mediated suppression of miR-182-5p and enhancement of SESN2 expression were also compromised. The MTT assay further showed that ATO induced cytotoxicity was enhanced by transfection of miR-182-5p mimics. Overexpression of miR-182-5p mimics significantly suppressed the expression of SENS2 and a firefly luciferase reporter gene fused to 3’- untranslated region (UTR) of SESN2 mRNA. Use of ribonucleoprotein immunoprecipitation (RNP-IP), ATO mediated suppression of miR-182-5p led to the stabilization of SESN2 mRNA as a result of Argonaute-2 (AGO2) dependent gene silencing. Furthermore, high expression of miR-182-5p and low expression of SESN2 mRNA tend to be associated with longer survival of glioma or lung cancer patients using public available gene expression datasets and online tools for prediction of clinical outcomes. Taken together, current data suggest that the miR-182-5p/SENS2 pathway is involved in ATO induced anti-oxidant responses, which may be important for the design of novel strategy for cancer treatment.

Ellagic acid mitigates arsenic-trioxide-induced mitochondrial dysfunction and cytotoxicity in SH-SY5Y cells

In the current study, neuroprotective significance of ellagic acid (EA, a polyohenol) was explored by primarily studying its antioxidant and antiapoptotic potential against arsenic trioxide (As₂ O₃ )-induced toxicity in SH-SY5Y human neuroblastoma cell lines. The mitigatory effects of EA with particular reference to cell viability and cytotoxicity, the generation of reactive oxygen species, DNA damage, and mitochondrial dynamics were studied. Pretreatment of SH-SY5Y cells with EA (10 and 20 μM) for 60 min followed by exposure to 2 μM As₂ O₃ protected the SH-SY5Y cells against the harmful effects of the second. Also, EA pre-treated groups expressed improved viability, repaired DNA, reduced free radical generation, and maintained altered mitochondrial membrane potential than those exposed to As₂ O₃ alone. EA supplementation also inhibited As₂ O₃ -induced cytochrome c expression that is an important hallmark for determining mitochondrial dynamics. Thus, the current investigations are more convinced for EA as a promising candidate in modulating As₂ O₃ -induced mitochondria-mediated neuronal toxicity under in vitro system.

Cytotoxicity and genotoxicity effects of arsenic trioxide on SQ20B human laryngeal carcinoma cells

This study investigates the cytotoxicity and the genotoxicity induced by arsenic trioxide As₂O₃in human laryngeal SQ20B carcinoma cell line. SQ20B cells were exposed to graded concentrations of arsenic trioxide (2 and 5μM) for 48h. Comet assay and γ-H2AX foci formation were used for measuring DNA damages, flow cytometry was used to identify cell cycle alterations and apoptosis, while cell morphology was visualized using transmission electron microscopy. The results show a dose-dependent induction of DNA damages and double strand breaks, alterations in cell cycle and morphologic alterations of cells. These results prove that As₂O₃ is highly cytotoxic and genotoxic at the micromolar range ina human laryngeal carcinoma cell line.

The antitumor effect of arsenic trioxide on hepatocellular carcinoma is enhanced by andrographolide

High concentrations of arsenic trioxide (As₂O₃) are used to treat acute promyelocytic leukemia and solid tumors, with negative side effects to normal cells. Andrographolide is a traditional Chinese medicine that exerts anti-cancer, anti-inflammatory, anti-virus, and anti-diabetic effects. Here, we tested the effects of combined andrographolide with As₂O₃ against hepatocellular carcinoma (HCC). We found that by increasing apoptosis, andrographolide synergistically enhanced the anti-tumor effects of As2O3 in HepG2 cells in vitro and in vivo. Furthermore, results from our microarray assays and experiments with mouse xenografts showed that EphB4 was downregulated by the combination of As₂O₃ plus andrographolide. These findings suggest that the combination of andrographolide and As₂O₃ could yield therapeutic benefits in the treatment of HCC.

Evaluation of Arsenic Trioxide Potential for Lung Cancer Treatment: Assessment of Apoptotic Mechanisms and Oxidative Damage

Background

Lung cancer is one of the most lethal and common cancers in the world, causing up to 3 million deaths annually. The chemotherapeutic drugs that have been used in treating lung cancer include cisplatin-pemetrexed, cisplastin-gencitabinoe, carboplatin-paclitaxel and crizotinib. Arsenic trioxide (ATO) has been used in the treatment of acute promyelocytic leukemia. However, its effects on lung cancer are not known. We hypothesize that ATO may also have a bioactivity against lung cancer, and its mechanisms of action may involve apoptosis, DNA damage and changes in stress-related proteins in lung cancer cells.

Methods

To test the above stated hypothesis, lung carcinoma (A549) cells were used as the test model. The effects of ATO were examined by performing 6-diamidine-2 phenylindole (DAPI) nuclear staining for morphological characterization of apoptosis, flow cytometry analysis for early apoptosis, and western blot analysis for stress-related proteins (Hsp70 and cfos) and apoptotic protein expressions. Also, the single cell gel electrophoresis (Comet) assay was used to evaluate the genotoxic effect.

Results

ATO-induced apoptosis was evidenced by chromatin condensation and formation of apoptotic bodies as revealed by DAPI nuclear staining. Cell shrinkage and membrane blebbing were observed at 4 and 6 µg/ml of ATO. Data from the western blot analysis revealed a significant dose-dependent increase (p < 0.05) in the Hsp 70, caspase 3 and p53 protein expression, and a significant (p < 0.05) decrease in the cfos, and bcl-2 protein expression at 4 and 6 µg/ml of ATO. There was a slight decrease in cytochrome c protein expression at 4 and 6 µg/ ml of ATO. Comet assay data revealed significant dose-dependent increases in the percentages of DNA damage, Comet tail lengths, and Comet tail moment.

Conclusion

Taken together our results indicate that ATO is cytotoxic to lung cancer cells and its bioactivity is associated with oxidative damage, changes in cellular morphology, and apoptosis.

Arsenic trioxide inhibits breast cancer cell growth via microRNA-328/hERG pathway in MCF-7 cells

Arsenic trioxide (As2O3) has been widely used in the treatment of acute promyelocytic leukemia and has been observed to exhibit therapeutic effects in various types of solid tumor. In a previous study by this group, it was shown that As2O3 induces the apoptosis of MCF-7 breast cancer cells through inhibition of the human ether-à-go-go-related gene (hERG) channel. The present study was designed to further investigate the effect of As2O3 on breast cancer cells and to examine the mechanism underlying the regulation of hERG expression. The present study confirmed that As2O3 inhibited tumor growth in vivo, following MCF-7 cell implantation into nude mice. Using computational prediction , it was identified that microRNA (miR)-328 had a binding site in the 3'-untranslated region of hERG mRNA. A luciferase activity assay demonstrated that hERG is a target gene of miR-328. Further investigation using western blot analysis and reverse transcription-quantitative polymerase chain reaction revealed that As2O3 downregulated hERG expression via upregulation of miR-328 expression in MCF-7 cells. In conclusion, As2O3 was observed to inhibit breast cancer cell growth, at least in part, through the miR-328/hERG pathway.

Adding ascorbic acid to arsenic trioxide produces limited benefit in patients with acute myeloid leukemia excluding acute promyelocytic leukemia

Arsenic trioxide (ATO) is highly effective in acute promyelocytic leukemia (APL), but despite its multiple mechanism of action, it has no activity in acute myeloid leukemia (AML) that excludes APL (non-APL AML). Ascorbic acid (AA) and ATO induces apoptosis in AML cell lines by depleting intracellular glutathione and generation of reactive oxygen species. In this study, we evaluated the effect of ATO plus AA in patients with non-APL AML. The study enrolled patient aged 18 or older with relapsed or refractory AML (non-APL) after conventional chemotherapy or previously untreated patients 55 years or older who were unfit for standard induction chemotherapy for AML. Intravenous ATO (0.25 mg/kg/day over 1-4 h) was given with intravenous AA (1 g/day over 30 min after ATO) for 5 days a week for 5 weeks (25 doses). Eleven AML patients were enrolled, including six previously untreated elderly patients aged 66-84 years in whom five had antecedent hematological disorder (ADH). Among 10 evaluable patients, one achieved a CR one a CRi and 4 patients had disappearance of blasts from peripheral blood and bone marrow. Five of the six responders were seen in previously untreated elderly patients. ATO related toxicity was mild. The combination of ATO and AA has limited clinical meaningful antileukemia activity in patients with non-APL AML.

Arsenic trioxide induces apoptosis of human gastrointestinal cancer cells

AIM: To investigate the changes in apoptosis in gastrointestinal cancer cells from patients with gastrointestinal cancers treated with arsenic trioxide (As₂O₃); and to study the possible molecular mechanisms of such changes by detecting the expression levels of p53 and Bcl-2.

METHODS: Twenty patients with gastrointestinal adenocarcinoma based on endoscopic and biopsy findings (ten patients with gastric cancer and ten patients with colorectal cancer) who received treatment in our hospital between August 2007 and December 2008 were included in this study. None of the patients had received anti-tumour agents prior to As₂O₃ treatment. As₂O₃ was administered intravenously at a dose of 0.01 g/d diluted with 5% glucose in normal saline for 2-3 h for 3 consecutive days before surgery. Morphological changes associated with apoptosis of gastrointestinal cancer cells were observed by light microscopy. Changes in the apoptotic index induced by As₂O₃ were investigated using the terminal deoxynucleotidyl transferase dUTP nick end labelling method. Expression levels of p53 and Bcl-2 proteins in gastrointestinal cancer tissues were determined by immunohistochemistry.

RESULTS: The apoptotic index of human gastrointestinal cancer cells was higher in cells from patients treated with As₂O₃ than in those not treated (P < 0.05). p53 protein expression in gastrointestinal tissues was unchanged by As₂O₃ (P > 0.05). However, Bcl-2 protein expression in gastrointestinal tissues was down-regulated by As₂O₃ (P < 0.01).

CONCLUSION: These results demonstrate that As₂O₃ treatment in patients with gastrointestinal cancers can induce apoptosis in gastrointestinal cancer cells and down-regulate Bcl-2 protein expression.

Arsenic trioxide inhibits Hedgehog, Notch and stem cell properties in glioblastoma neurospheres

Background

Notch and Hedgehog signaling have been implicated in the pathogenesis and stem-like characteristics of glioblastomas, and inhibitors of the pathways have been suggested as new therapies for these aggressive tumors. It has also been reported that targeting both pathways simultaneously can be advantageous in treating glioblastoma neurospheres, but this is difficult to achieve in vivo using multiple agents. Since arsenic trioxide has been shown to inhibit both Notch and Hedgehog in some solid tumors, we examined its effects on these pathways and on stem cell phenotype in glioblastoma.

Results

We found that arsenic trioxide suppresses proliferation and promotes apoptosis in three stem-like glioblastoma neurospheres lines, while inhibiting Notch and Hedgehog target genes. Importantly, arsenic trioxide markedly reduced clonogenic capacity of the tumor neurospheres, and the stem-like CD133-positive fraction was also diminished along with expression of the stem cell markers SOX2 and CD133.

Conclusions

Our results suggest that arsenic trioxide may be effective in targeting stem-like glioblastoma cells in patients by inhibiting Notch and Hedgehog activity.

Cell-penetrating properties of the transactivator of transcription and polyarginine (R9) peptides, their conjugative effect on nanoparticles and the prospect of conjugation with arsenic trioxide

Cell-penetrating peptides (CPPs) are short chains of amino acids with the distinct ability to cross cell plasma membranes. They are usually between seven and 30 residues in length. The mechanism of action is still a highly debated subject among researchers; it seems that a commonality between all CPPs is the presence of positively charged residues within the amino acid chain. Polyarginine and the transactivator of transcription peptide are two widely used CPPs. One distinct application of these CPPs is the ability to further enhance the therapeutic properties of a range of different agents. One group of agents of particular importance are nanoparticles (NPs). Most NPs have no mechanism for cellular uptake. Hence, by conjugating CPPs to NPs, the amount of NPs taken up by cells can be increased, and therefore, the therapeutic benefits can be maximized. Some examples of this will be explored further in this review. In addition to CPPs, the concept of conjugation with the anticancer drug arsenic trioxide is reviewed and the prospect of transactivator of transcription-conjugated arsenic trioxide albumin microspheres is also discussed. Recent locked nucleic acid technology to stabilize nucleotides (RNA or DNA) aptamer complexes able to target cancer cells more specifically and selectively to kill tumour cells and spare normal body cells. NPs tagged with modified locked nucleic acid-aptamers have the potential to kill cancer cells more specifically and effectively while sparing normal cells.

Arsenic Trioxide Induces Apoptosis in Uveal Melanoma Cells Through the Mitochondrial Pathway

Uveal melanoma, the most common primary intraocular malignancy in adults, is highly resistant to most chemotherapeutic drugs. Arsenic trioxide (ATO) is known to inhibit ocular melanoma cell growth. However, the effects of ATO on human uveal melanoma cells are poorly understood. Therefore, this study evaluated the mechanisms of ATO and its inhibiting effects on a human uveal melanoma cell line (SP6.5). An MTT assay indicated that, compared to human fibroblasts, ATO had a stronger inhibiting effect on SP6.5 cell proliferation in a dose- and time-dependent manner. The apoptosis ratio in SP6.5 cells, which was indicated by cell DNA fragmentation, was 4.1- to 7.7-fold higher after ATO-treatment. The ATO treatment substantially increased the activities of caspase-3 and caspase-9, but not of caspase-8. These findings were consistent with the protein expression observed by Western blots. ATO also significantly enhanced expression of Bax and cytochrome c proteins but suppressed those of Bcl-2. Therefore, ATO-induced apoptosis in uveal melanoma cells occurs mainly through the mitochondrial pathway rather than through the death receptor pathway. This report is the first to evaluate the complete mitochondria-dependent apoptotic pathway of ATO in uveal melanoma cells. These results can be used to improve the clinical effectiveness of ATO treatment for uveal melanoma.

Arsenic trioxide enhances the cytotoxic effect of cisplatin in head and neck squamous cell carcinoma cell lines

Arsenic trioxide (ATO) has been approved for the treatment of relapsed acute promyelocytic leukaemia. The aim of this study was to determine whether ATO would lead to cell death in head and neck squamous cell carcinoma (HNSCC) cell lines and whether it was able to enhance the cytotoxicity of cisplatin, a standard chemotherapeutic agent. The four HNSCC cell lines SCC9, SCC25, CAL27 and FADU were treated with ATO or cisplatin alone or with ATO and cisplatin in combination. Cytotoxicity assays, immunohistochemistry, western blot analysis and flow cytometry were carried out. Possible interactions between the two drugs were calculated using the Chou-Talalay equation. Ther results demonstrated a synergistic cytotoxic effect of the combination of ATO and cisplatin at high doses. The two agents induced apoptosis in all four HNSCC cell lines. In conclusion, this study showed that ATO is a promising therapeutic drug with cytotoxic effects in HNSCC. We demonstrated a synergistic effect in the combined treatment with cisplatin at high doses.

Arsenic trioxide induces the apoptosis of human breast cancer MCF-7 cells through activation of caspase-3 and inhibition of HERG channels

Arsenic trioxide (As(2)O(3)) has been widely used to treat patients with acute promyelocytic leukemia and has also been shown to exhibit therapeutic effects on various types of solid tumors, including gastric cancer and lung carcinoma. Breast cancer is a type of solid tumor whose incidence has been increasing for many years. The present study was designed to investigate the effects of As(2)O(3) on the human breast cancer cell line MCF-7, and to explore its potential mechanisms. The MTT assay demonstrated that As(2)O(3) decreased the cellular viability of MCF-7 cells in a concentration-dependent manner. Morphological observation, the TUNEL assay and flow cytometric analysis revealed that apoptosis was involved in the process. An assay for caspase-3 activity suggested that the apoptosis was mediated through caspase-3 activation. Further investigation indicated that protein levels of the human ether-a-go-go-related gene (HERG) were markedly downregulated by As(2)O(3). Taken together, the results indicate that arsenic trioxide induces the apoptosis of human breast cancer MCF-7 cells at least in part through the activation of caspase-3 and the decrease in HERG expression.

Basic mechanisms of arsenic trioxide (ATO)-induced apoptosis in human leukemia (HL-60) cells

Background

Acute promyelocytic leukemia (APL) is a blood cancer that affects people of all ages and strikes about 1,500 patients in the United States each year. The standard treatment of APL has been based on the combined administration of all-trans retinoic acid and chemotherapy including anthracyclins and cytarabine. However, 10-20% of patients relapse, with their disease becoming resistant to conventional treatment. Recently the Food and Drug Administration has approved the use of arsenic trioxide (ATO) or Trisenox for the treatment of APL, based on clinical studies showing a complete remission, especially in relapsed patients. In a recently published study we demonstrated that ATO pharmacology as an anti-cancer drug is associated with its cytotoxic and genotoxic effects in human leukemia cells.

Methods

In the present study, we further investigated the apoptotic mechanisms of ATO toxicity using the HL-60 cell line as a test model. Apoptosis was measured by flow cytometry analysis of phosphatidylserine externalization (Annexin V assay) and caspase 3 activity, and by DNA laddering assay.

Results

Flow cytometry data showed a strong dose-response relationship between ATO exposure and Annexin-V positive HL-60 cells. Similarly, a statistically significant and dose-dependent increase (p <0.05) was recorded with regard to caspase 3 activity in HL60 cells undergoing late apoptosis. These results were confirmed by data of DNA laddering assay showing a clear evidence of nucleosomal DNA fragmentation in ATO-treated cells.

Conclusion

Taken together, our research demonstrated that ATO represents an apoptosis-inducing agent and its apoptotic mechanisms involve phosphatidylserine externalization, caspase 3 activation and nucleosomal DNA fragmentation.

Antitumor effect and mechanisms of arsenic trioxide on subcutaneously implanted human gastric cancer in nude mice

We sought to investigate the efficacy of arsenic trioxide (As(2)O(3)) against a human gastric cell line implanted in nude mice in vivo, as well as the mechanism involved. The solid tumor model was created in nude mice with the gastric cancer cell line SGC-7901. The animals were randomly divided into three groups. As(2)O(3) was injected into animals in two arsenic-treated groups (2.5 mg/kg and 5 mg/kg), and the same volume of saline solution was injected into the control group. The inhibitory effect was observed in every group. Apoptotic cells and apoptotic bodies were observed by transmission electron microscope; the fraction of apoptotic cells was detected by TUNEL (terminal deoxynucleotidyl transferase dUTP nick-end labeling) under laser confocal technology. The expression of Fas and FasL was detected by immunohistochemical staining. In nude mice, after treatment with 5 mg/kg and 2.5 mg/kg As(2)O(3), approximately 50% and 30% tumor growth inhibition were observed, respectively (P < 0.05 for both treatment groups). Increase in apoptotic cells and apoptotic bodies appeared in As(2)O(3)-treated tumors compared with the control group. The fluorescence intensity levels of apoptotic cells in tumor were significantly higher in the arsenic-treated groups (P < 0.05 for both treatment groups). The fluorescence intensity level of apoptotic cells in the 5-mg/kg group was higher than that in the 2.5-mg/kg group (P < 0.05). The expression of Fas protein increased in dose- and time-dependent manner after the treatment with As(2)O(3), but that of FasL protein showed no significant difference between control and treated groups. As(2)O(3) did not induce hepatic and renal system injury in the nude mice. As(2)O(3) can inhibit the growth of human gastric cell implanted tumor. We ascribe this to upregulation of Fas, which can induce apoptosis of gastric cells.

A novel combination therapy with arsenic trioxide and parthenolide against pancreatic cancer cells

OBJECTIVES

To investigate the anticancer effect and potential mechanism of combination treatment with arsenic trioxide (ATO) and parthenolide (PTL) in human pancreatic cancer cells.

METHODS

The effects of PTL/ATO on 2 pancreatic carcinoma cell lines, PANC-1 and BxPC-3, were determined by trypan blue exclusion, annexin V/propidium iodide, 4',6-diamidino-2-phenylindole HCl, terminal deoxynucleotidyltransferase-mediated nick-end labeling, flow cytometry, Western blot, and clonogenic assay. In vivo study was performed in PANC-1 tumor xenografts in nude mice.

RESULTS

The combination of PTL and ATO inhibited the growth of pancreatic tumor cell lines much greater than each agent alone. The PTL/ATO treatment induced apoptosis and reactive oxygen species generation. Both of them were inhibited by L-N-acetylcysteine and diphenylene iodonium chloride. During ATO/PTL-mediated apoptosis, the collapse of mitochondrial transmembrane potential occurred with cytochrome c release, which was reversed by L-N-acetylcysteine. The combination treatment significantly reduced tumor growth rates of PANC-1 xenografts compared with those treated with either PTL or ATO alone.

CONCLUSIONS

Combination therapy with ATO and PTL has an augmented anticancer effect on pancreatic cancer in vitro and in vivo, which provides a novel promising approach in the treatment of pancreatic cancer. The mechanism of growth-suppressive effect of combination therapy was correlated with its ability to induce reactive oxygen species generation and apoptosis via the mitochondrial pathway.

Neuroblastoma cell death is induced by inorganic arsenic trioxide (As(2)O(3)) and inhibited by a normal human bone marrow cell-derived factor

Three phenotypically distinct cell types are present in human neuroblastomas (NB) and NB cell lines: I-type stem cells, N-type neuroblastic precursors, and S-type Schwannian/melanoblastic precursors. The stimulation of human N-type neuroblastoma cell proliferation by normal human bone marrow monocytic cell conditioned medium (BMCM) has been demonstrated in vitro, a finding consistent with the high frequency of bone marrow (BM) metastases in patients with advanced NB. Inorganic arsenic trioxide (As₂O₃), already clinically approved for the treatment of several hematological malignancies, is currently under investigation for NB. Recent studies show that As₂O₃ induces apoptosis in NB cells. We examined the impact of BMCM on growth and survival of As₂O₃-treated NB cell lines, to evaluate the response of cultured NB cell variants to regulatory agents. We studied the effect of BMCM on survival and clonogenic growth of eleven As₂O₃-treated NB cell lines grown in sparsely seeded, non-adherent, semi-solid cultures. As₂O₃ had a strong inhibitory effect on survival of all tested NB cell lines. BMCM augmented cell growth and survival and reversed the inhibitory action of As₂O₃ in all tested cell lines, but most strongly in N-type cells_. While As₂O₃ effectively reduced survival of all tested NB cell lines, BMCM effectively impacted its inhibitory action. Better understanding of micro-environmental regulators affecting human NB tumor cell growth and survival may be seminal to the development of therapeutic strategies and clinically effective agents for this condition.

Environmental toxicity, oxidative stress and apoptosis: ménage à trois

Apoptosis is an evolutionary conserved homeostatic process involved in distinct physiological processes including organ and tissue morphogenesis, development and senescence. Its deregulation is also known to participate in the etiology of several human diseases including cancer, neurodegenerative and autoimmune disorders. Environmental stressors (cytotoxic agents, pollutants or toxicants) are well known to induce apoptotic cell death and to contribute to a variety of pathological conditions. Oxidative stress seems to be the central element in the regulation of the apoptotic pathways triggered by environmental stressors. In this work, we review the established mechanisms by which oxidative stress and environmental stressors regulate the apoptotic machinery with the aim to underscore the relevance of apoptosis as a component in environmental toxicity and human disease progression.

Inhibition of mitochondrial protein translation sensitizes melanoma cells to arsenic trioxide cytotoxicity via a reactive oxygen species dependent mechanism

PURPOSE

Current standard chemotherapeutic regimens for malignant melanoma are unsatisfactory. Although in vitro studies of arsenic trioxide (ATO) have demonstrated promise against melanoma, recent phase II clinical trials have failed to show any significant clinical benefit when used as a single agent. To enhance the efficacy of ATO in the treatment of melanoma, we sought to identify compounds that potentiate the cytotoxic effects of ATO in melanoma cells. Through a screen of 2,000 marketed drugs and naturally occurring compounds, a variety of antibiotic inhibitors of mitochondrial protein translation were identified.

METHODS

The mechanism of action for the most effective agent identified, thiostrepton, was examined in a panel of melanoma cells. Effects of combinatorial ATO and thiostrepton treatment on cytotoxicity, apoptosis, mitochondrial protein content, and reactive oxygen species (ROS) were assessed.

RESULTS

Thiostrepton (1 microM) sensitized three out of five melanoma cell lines to ATO-mediated growth inhibition. Treatment with thiostrepton resulted in reduced levels of the mitochondrial-encoded protein cytochrome oxidase I (COX1). Exposure to thiostrepton in combination with ATO resulted in increased levels of cleaved poly (ADP-ribose) polymerase and cellular ROS. The growth inhibitory and pro-apototic effects of addition of the ATO/thiostrepton combination were reversed by the free radical scavenger N-acetyl-L-cysteine.

CONCLUSIONS

Our data suggest that thiostrepton enhances the cytotoxic effects of ATO through a ROS-dependent mechanism. Co-administration of oxidative stress-inducing drugs such as thiostrepton in order to enhance the efficacy of ATO in the treatment of melanoma warrants further investigation.

Arsenic trioxide sensitizes human glioma cells, but not normal astrocytes, to TRAIL-induced apoptosis via CCAAT/enhancer-binding protein homologous protein-dependent DR5 up-regulation

The current study shows that treatment of tumor necrosis factor-related apoptosis-inducing ligand (TRAIL)-resistant glioma cells with a combination of TRAIL and subtoxic doses of arsenic trioxide (As(2)O(3)) induces rapid apoptosis. Whereas TRAIL-mediated proteolytic processing of procaspase-3 was partially blocked in glioma cells, treatment with As(2)O(3) efficiently recovered TRAIL-induced activation of caspases. We also found that As(2)O(3) treatment of glioma cells significantly up-regulated DR5, a death receptor of TRAIL. Furthermore, suppression of DR5 expression by small interfering RNA (siRNA) inhibited As(2)O(3)/TRAIL-induced apoptosis of U87MG glioma cells, suggesting that DR5 up-regulation is critical for As(2)O(3)-induced sensitization of glioma cells to TRAIL-mediated apoptosis. Our results also indicate that an increase in CCAAT/enhancer binding protein homologous protein (CHOP) protein levels precedes As(2)O(3)-induced DR5 up-regulation. The involvement of CHOP in this process was confirmed by siRNA-mediated CHOP suppression, which not only attenuated As(2)O(3)-induced DR5 up-regulation but also inhibited the As(2)O(3)-stimulated TRAIL-induced apoptosis. These results therefore suggest that the CHOP-mediated DR5 up-regulation, brought about by As(2)O(3), stimulates the TRAIL-mediated signaling pathway. This in turn leads to complete proteolytic processing of caspase-3, which is partially primed by TRAIL in glioma cells. In contrast to human glioma cells, astrocytes were very resistant to the combined administration of As(2)O(3) and TRAIL, demonstrating the safety of this treatment. In addition, As(2)O(3)-mediated up-regulation of CHOP and DR5, as well as partial proteolytic processing of procaspase-3 by TRAIL, was not induced in astrocytes. Taken together, the present results suggest that the combined treatment of glioma cells with As(2)O(3) plus TRAIL may provide an effective and selective therapeutic strategy.

Dynamic effects of autophagy on arsenic trioxide-induced death of human leukemia cell line HL60 cells

AIM

To evaluate the contribution of an autophagic mechanism to the As2O3- induced death of human acute myeloid leukaemia cell line HL60 cells.

METHODS

The growth inhibition of HL60 cells induced by As2O3 was assessed with 3-(4,5- dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide colorimetric assay. The activation of autophagy was determined with monodansylcadaverine labeling and transmission electron microscope. The role of autophagy in the As2O3-induced death of HL60 cells was assessed using autophagic and lysosomal inhibitors. Immunofluorescence, flow cytometry, and Western blot analysis were used to study the apoptotic and autophagic mechanisms.

RESULTS

After treatment with As2O3, the proliferation of HL60 cells was significantly inhibited and the formation of autophagosomes increased. The blockade of autophagy maturation with the autophagy-specific inhibitor 3-methyladenine (3-MA) or the lysosome-neutralizing agent NH4Cl 1 h before As2O3 potentiated the As2O3-induced death of HL60 cells. In contrast, 3-MA attenuated As2O3-induced death when administered 30 min after As2O3. 3-MA and NH4Cl also inhibited As2O3-induced upregulation of microtubule-associated protein 1 light chain 3, the protein required for autophagy in mammalian cells. Following As2O3, lysosomes were activated as indicated by increased levels of cathepsins B and L. The apoptotic response of HL60 cells to As2O3 was suggested by the collapse of mitochondrial membrane potential, release of cytochrome c from mitochondria, and the activation of caspase-3. Pretreatment with 3-MA prior to As2O3 amplified these apoptotic signals, while posttreatment with 3-MA 30 min after As2O3 attenuated the apoptotic pathways.

CONCLUSION

Autophagy plays complex roles in the As2O3-induced death of HL60 cells; it inhibits As2O3-induced apoptosis in the initiation stage, but amplifies the As2O3-mediated apoptotic program if it is persistently activated.

Trolox enhances the anti-lymphoma effects of arsenic trioxide, while protecting against liver toxicity

Arsenic trioxide (As2O3) is an effective therapy in acute promyelocytic leukemia (APL), but its use in other malignancies is limited by the higher concentrations required to induce apoptosis. We have reported that trolox, an analogue of alpha-tocopherol, increases As2O3-mediated apoptosis in a variety of APL, myeloma and breast cancer cell lines, while non-malignant cells may be protected. In the present study, we extended previous results to show that trolox increases As2O3-mediated apoptosis in the P388 lymphoma cell line in vitro, as evidenced by decrease of mitochondrial membrane potential and release of cytochrome c. We then sought to determine whether this combination can enhance antitumor effects while protecting normal cells in vivo. In BDF1 mice, trolox treatment decreased As2O3-induced hepatomegaly, markers of oxidative stress and hepatocellular damage. In P388 tumor-bearing mice, As2O3 treatment prolonged survival, and the addition of trolox provided a further significant increase in lifespan. In addition, the combination of As2O3 and trolox inhibited metastatic spread, and protected the tumor-bearing mice from As2O3 liver toxicity. Our results suggest, for the first time, that trolox might prevent some of the clinical manifestations of As2O3-related toxicity while increasing its pro-apoptotic capacity and clinical efficacy in hematological malignancies.