Arsenic induces apoptosis of multidrug-resistant human myeloid leukemia cells that express Bcr-Abl or overexpress MDR, MRP, Bcl-2, or Bcl-xL

Long-circulating gambogic acid-loaded nanodiamond composite nanosystem with inhibition of cell migration for tumor therapy

Herein, ultra dispersed and stably suspended nanodiamonds (NDs) were demonstrated to have a high load capacity, sustained release, and ability to serve as a biocompatible vehicle for delivery anticancer drugs. NDs with size of 50-100 nm exhibited good biocompatibility in normal human liver (L-02) cells. In particular, 50 nm ND not only promoted the noticeable proliferation of the L-02 cells but also can effectively inhibited the migration of human liver carcinoma (HepG2) cells. The gambogic acid-loaded nanodiamond (ND/GA) complex assembled by π-π stacking exhibits ultrasensitive and apparent suppression efficiency on the proliferation of HepG2 cells through high internalization and less efflux compared to free GA. More importantly, the ND/GA system can significantly increase the intracellular reactive oxygen species (ROS) levels in HepG2 cells and thus induce the cell apoptosis. The increase in intracellular ROS levels causes damage to the mitochondrial membrane potential (MMP) and activates cysteinyl aspartate specific proteinase 3 (Caspase-3) and cysteinyl aspartate specific proteinase 9 (Caspase-9), which leads to the occurrence of apoptosis. In vivo experiments also confirmed that the ND/GA complex has a much higher anti-tumor capability than free GA. Thus, the current ND/GA system is promising for cancer therapy.

Cancer-cell-membrane-camouflaged supramolecular self-assembly of antisense oligonucleotide and chemodrug for targeted combination therapy

The anti-apoptotic B-cell lymphoma-2 (Bcl-2) family of proteins are critical regulators of cell death that are overexpressed in many cancer cells, especially in multi-drug resistant cancer cells. Combinatorial gene- and chemotherapies using antisense oligonucleotides (ASOs) to suppress the expression of Bcl-2-family mRNA and restore the sensitivity of the cell to chemodrugs provide a promising pathway for anticancer treatment. However, intrinsic differences between macromolecular ASOs and small molecular chemodrugs make their co-delivery challenging. Moreover, extraneous carriers may induce immunogenicity and inflammation problems. Herein, we develop a targeted nanodrug delivery system using the cationic amphiphilic chemodrug mitoxantrone (Mito), which interacts with Bcl-2 ASO through electrostatic interaction and self-assembles into nanoparticles (NP_[Bcl-2/Mito]), whose size can be controlled by regulating the ratio of ASO and Mito. NP_[Bcl-2/Mito] can protect the ASO from degradation during delivery and combine gene- and chemotherapies to improve the anticancer effect. Furthermore, cancer cell membranes (CCMs) derived from homologous tumors were used to camouflage NP_[Bcl-2/Mito] (NP_[Bcl-2/Mito]@CCM) to achieve immune escape and tumor targeting. Both in vitro and in vivo assessments demonstrate the excellent performance of NP_[Bcl-2/Mito]@CCM for drug-resistant breast tumor therapy. This CCM-camouflaged ASO/chemodrug nanoplatform provides a promising pathway for the targeted delivery of ASOs and chemodrugs for tumor combination therapy.

Synergistic effects of arsenic and fluoride on oxidative stress and apoptotic pathway in Leydig and Sertoli cells

Excessive intake of arsenic (As) and fluoride (F), which are present in underground drinking water, have adverse effects on human health, and especially on the male reproductive system. In this regard, it's critical to figure out how As and F affect Leydig and Sertoli cells, which are key cells in the male reproductive system. The goal of this study was to determine the synergistic effects of co-exposure of As and F, via drinking water, on Leydig and Sertoli cells, which are models for the male reproductive system, as well as the mechanisms underlying these effects in terms of oxidative damage and apoptosis. Leydig and Sertoli cells were exposed to concentrations of 7.7 µM (0.57 ppm) As and 0.4 mM (7.24 ppm) F based on the highest daily intake of drinking water for 24 h. The present results revealed that As and/or F treatment reduced cell viability and proliferation in Leydig and Sertoli cells, elevated lactate dehydrogenase, a cytotoxicity marker, and triggered oxidative stress and apoptosis. Furthermore, it has been proven that when As and F are exposed in combination, they have a synergistic effect. In conclusion, by revealing the harmful effects of As and F on Leydig and Sertoli cells, and thus on male infertility, it is possible to reduce As and F exposure to prevent infertility after exposure to these molecules not only separately but also together. It will be considered to determine new action and action plans to reduce As and F exposure.

Insights into the mechanism of Arnebia euchroma on leukemia via network pharmacology approach

BACKGROUND

Arnebia euchroma (A. euchroma) is a traditional Chinese medicine (TCM) used for the treatment of blood diseases including leukemia. In recent years, many studies have been conducted on the anti-tumor effect of shikonin and its derivatives, the major active components of A. euchroma. However, the underlying mechanism of action (MoA) for all the components of A. euchroma on leukemia has not been explored systematically.

METHODS

In this study, we analyzed the MoA of A. euchroma on leukemia via network pharmacology approach. Firstly, the chemical components and their concentrations in A. euchroma as well as leukemia-related targets were collected. Next, we predicted compound-target interactions (CTIs) with our balanced substructure-drug-target network-based inference (bSDTNBI) method. The known and predicted targets of A. euchroma and leukemia-related targets were merged together to construct A. euchroma-leukemia protein-protein interactions (PPIs) network. Then, weighted compound-target bipartite network was constructed according to combination of eight central attributes with concentration information through Cytoscape. Additionally, molecular docking simulation was performed to calculate whether the components and predicted targets have interactions or not.

RESULTS

A total of 65 components of A. euchroma were obtained and 27 of them with concentration information, which were involved in 157 targets and 779 compound-target interactions (CTIs). Following the calculation of eight central attributes of targets in A. euchroma-leukemia PPI network, 37 targets with all central attributes greater than the median values were selected to construct the weighted compound-target bipartite network and do the KEGG pathway analysis. We found that A. euchroma candidate targets were significantly associated with several apoptosis and inflammation-related biological pathways, such as MAPK signaling, PI3K-Akt signaling, IL-17 signaling, and T cell receptor signaling pathways. Moreover, molecular docking simulation demonstrated that there were eight pairs of predicted CTIs had the strong binding free energy.

CONCLUSIONS

This study deciphered that the efficacy of A. euchroma in the treatment of leukemia might be attributed to 10 targets and 14 components, which were associated with inhibiting leukemia cell survival and inducing apoptosis, relieving inflammatory environment and inhibiting angiogenesis.

Reversal of glucocorticoid resistance in Acute Lymphoblastic Leukemia cells by miR-145

Objective

To analyze the expression levels of miR-145 in ALL children and their effects on the prognosis of ALL and to explore the mechanism of miR-145 in reversing the resistance of ALL cells to glucocorticoids.

Methods

A GEO database dataset was used to analyze the expression levels of miR-145 in ALL children. The association between miR-145 and childhood prognosis was analyzed by the TARGET database data. The expression levels of miR-145 in the glucocorticoid-resistant ALL cell line CEM-C1 were increased by lipofectamine 2000-mediated transfection. Cell proliferation inhibition experiments were performed to detect the effect of miR-145 on the response of CEM-C1 cell line to glucocorticoids. The expression levels of the apoptotic, autophagic and drug resistance-associated genes and proteins were detected by qPCR and western blot analysis.

Results

The expression levels of miR-145 were decreased in ALL patients (P < 0.001) and the prognosis of ALL in children with high miR-145 expression was significantly improved (P < 0.001). Increased miR-145 expression can improve the sensitivity of CEM-C1 cells to glucocorticoids. The expression levels of the proapoptotic and the anti-apoptotic genes Bax and Bcl-2 were increased and decreased, respectively, whereas the expression levels of the autophagicgenes Beclin 1 and LC were increased. In addition, the expression levels of the drug resistance gene MDR1 were decreased.

Conclusion

The expression levels of miR-145 in ALL children were decreased and they were associated with disease prognosis. The data indicated that miR-145 can reverse cell resistance by regulating apoptosis of CEM-C1 cells and autophagy.

Polymeric nanovesicles as simultaneous delivery platforms with doxorubicin conjugation and elacridar encapsulation for enhanced treatment of multidrug-resistant breast cancer

Multidrug resistance (MDR) is one of the major obstacles hindering the successful chemotherapy of cancer. Overexpression of drug efflux transporters such as P-glycoprotein (P-gp) is an important factor responsible for MDR. In this study, a novel copolymer methoxy-poly(ethylene glycol)-poly[(N-(6-hydroxyhexyl)-g-doxorubicin-l-aspartamide)-(β-benzyl-l-aspartate)] (mPEG-P[Asp(HPA-g-DOX)-BLA)] was synthesized and utilized to assemble into nanovesicles with hydrophilic P-gp inhibitor elacridar hydrochloride (Ela) encapsulated into the aqueous lumen. Doxorubicin (DOX) was covalently conjugated onto the polymer chain via a pH-cleavable amide linkage, leading to a pH responsive DOX release as well as disintegration of the nanovesicles in the lysosome of tumor cells. In vitro studies demonstrated that the DOX and Ela co-delivered nanovesicles showed superior cytotoxicity and enhanced anti-tumor properties as compared to single DOX-delivery nanosystems in MCF-7/ADR cancer, which was attributed to the P-gp bioactivity inhibition as investigated by a cell immunofluorescence assay. In vivo studies showed that the polymeric nanovesicles effectively accumulated at the tumor site and the co-delivered DOX and Ela effectively suppressed the MCF-7/ADR tumor growth. All the results indicated that the acid-liable nanovesicles had a synergistic effect to enhance antitumor efficacy for multidrug-resistant breast cancer treatment.

Combination of ATO with FLT3 TKIs eliminates FLT3/ITD+ leukemia cells through reduced expression of FLT3

Acute myeloid leukemia (AML) patients with FLT3/ITD mutations have a poor prognosis. Monotherapy with selective FLT3 tyrosine kinase inhibitors (TKIs) have shown transient and limited efficacy due to the development of resistance. Arsenic trioxide (ATO, As₂O₃) has been proven effective in treating acute promyelocytic leukemia (APL) and has shown activity in some cases of refractory and relapsed AML and other hematologic malignances. We explored the feasibility of combining FLT3 TKIs with ATO in the treatment of FLT3/ITD+ leukemias. The combination of FLT3 TKIs with ATO showed synergistic effects in reducing proliferation, viability and colony forming ability, and increased apoptosis in FLT3/ITD+ cells and primary patient samples. In contrast, no cooperativity was observed against wild-type FLT3 leukemia cells. ATO reduced expression of FLT3 RNA and its upstream transcriptional regulators (HOXA9, MEIS1), and induced poly-ubiquitination and degradation of the FLT3 protein, partly through reducing its binding with USP10. ATO also synergizes with FLT3 TKIs to inactivate FLT3 autophosphorylation and phosphorylation of its downstream signaling targets, including STAT5, AKT and ERK. Furthermore, ATO combined with sorafenib, a FLT3 TKI, in vivo reduced growth of FLT3/ITD+ leukemia cells in NSG recipients. In conclusion, these results suggest that ATO is a potential candidate to study in clinical trials in combination with FLT3 TKIs to improve the treatment of FLT3/ITD+ leukemia.

Multifactorial Modes of Action of Arsenic Trioxide in Cancer Cells as Analyzed by Classical and Network Pharmacology

Arsenic trioxide is a traditional remedy in Chinese Medicine since ages. Nowadays, it is clinically used to treat acute promyelocytic leukemia (APL) by targeting PML/RARA. However, the drug's activity is broader and the mechanisms of action in other tumor types remain unclear. In this study, we investigated molecular modes of action by classical and network pharmacological approaches. CEM/ADR5000 resistance leukemic cells were similar sensitive to As2O3 as their wild-type counterpart CCRF-CEM (resistance ratio: 1.88). Drug-resistant U87.MG ΔEGFR glioblastoma cells harboring mutated epidermal growth factor receptor were even more sensitive (collateral sensitive) than wild-type U87.MG cells (resistance ratio: 0.33). HCT-116 colon carcinoma p53-/- knockout cells were 7.16-fold resistant toward As2O3 compared to wild-type cells. Forty genes determining cellular responsiveness to As2O3 were identified by microarray and COMPARE analyses in 58 cell lines of the NCI panel. Hierarchical cluster analysis-based heat mapping revealed significant differences between As2O3 sensitive cell lines and resistant cell lines with p-value: 1.86 × 10-5. The genes were subjected to Galaxy Cistrome gene promoter transcription factor analysis to predict the binding of transcription factors. We have exemplarily chosen NF-kB and AP-1, and indeed As2O3 dose-dependently inhibited the promoter activity of these two transcription factors in reporter cell lines. Furthermore, the genes identified here and those published in the literature were assembled and subjected to Ingenuity Pathway Analysis for comprehensive network pharmacological approaches that included all known factors of resistance of tumor cells to As2O3. In addition to pathways related to the anticancer effects of As2O3, several neurological pathways were identified. As arsenic is well-known to exert neurotoxicity, these pathways might account for neurological side effects. In conclusion, the activity of As2O3 is not restricted to acute promyelocytic leukemia. In addition to PML/RARA, numerous other genes belonging to diverse functional classes may also contribute to its cytotoxicity. Network pharmacology is suited to unravel the multifactorial modes of action of As2O3.

A review on the effects of current chemotherapy drugs and natural agents in treating non-small cell lung cancer

Lung cancer is the leading cause of cancer deaths worldwide, and this makes it an attractive disease to review and possibly improve therapeutic treatment options. Surgery, radiation, chemotherapy, targeted treatments, and immunotherapy separate or in combination are commonly used to treat lung cancer. However, these treatment types may cause different side effects, and chemotherapy-based regimens appear to have reached a therapeutic plateau. Hence, effective, better-tolerated treatments are needed to address and hopefully overcome this conundrum. Recent advances have enabled biologists to better investigate the potential use of natural compounds for the treatment or control of various cancerous diseases. For the past 30 years, natural compounds have been the pillar of chemotherapy. However, only a few compounds have been tested in cancerous patients and only partial evidence is available regarding their clinical effectiveness. Herein, we review the research on using current chemotherapy drugs and natural compounds (Wortmannin and Roscovitine, Cordyceps militaris, Resveratrol, OSU03013, Myricetin, Berberine, Antroquinonol) and the beneficial effects they have on various types of cancers including non-small cell lung cancer. Based on this literature review, we propose the use of these compounds along with chemotherapy drugs in patients with advanced and/or refractory solid tumours.

Characteristics of doxorubicin-selected multidrug-resistant human leukemia HL-60 cells with tolerance to arsenic trioxide and contribution of leukemia stem cells

The present study selected and characterized a multidrug-resistant HL-60 human acute promyelocytic leukemia cell line, HL-60/RS, by exposure to stepwise incremental doses of doxorubicin. The drug-resistant HL-60/RS cells exhibited 85.68-fold resistance to doxorubicin and were cross-resistant to other chemotherapeutics, including cisplatin, daunorubicin, cytarabine, vincristine and etoposide. The cells over-expressed the transporters P-glycoprotein, multidrug-resistance-related protein 1 and breast-cancer-resistance protein, encoded by the adenosine triphosphate-binding cassette (ABC)B1, ABCC1 and ABCG2 genes, respectively. Unlike other recognized chemoresistant leukemia cell lines, HL-60/RS cells were also strongly cross-resistant to arsenic trioxide. The proportion of leukemia stem cells (LSCs) increased synchronously with increased of drug resistance in the doxorubicin-induced HL-60 cell population. The present study confirmed that doxorubicin-induced HL-60 cells exhibited multidrug-resistance and high arsenic-trioxide resistance. Drug-resistance in these cells may be due to surviving chemoresistant LSCs in the HL-60 population, which have been subjected to long and consecutive selection by doxorubicin.

Effectiveness of imatinib mesylate over etoposide in the treatment of sensitive and resistant chronic myeloid leukaemia cells in vitro

Chronic myeloid leukaemia (CML) is a form of leukaemia derived from the myeloid cell lineage. Imatinib mesylate, the breakpoint cluster region-abelson murine leukeamia kinase inhibitor, is a specific reagent used in the clinical treatment of CML. The DNA topoisomerase II inhibitor, etoposide, is also employed as a therapeutic, though it is used to a lesser extent. The present study aims to evaluate the effects of CML-targeted therapy, utilising imatinib mesylate and etoposide in the in vitro treatment of parental sensitive and adriamycin-resistant CML in the K562 and K562/ADM cell lines, respectively. Preliminary work involved the screening of multidrug resistant (MDR) gene expression, including MDR1, MRP1 and B-cell lymphoma 2 (BCL-2) at the mRNA levels. The sensitive and resistant CML cell lines expressed the MRP1 gene, though the sensitive K562 cells expressed low, almost undetectable levels of MDR1 and BCL-2 genes relative to the K562/ADM cells. Following treatment with imatinib mesylate or etoposide, the IC50 for imatinib mesylate did not differ between the sensitive and resistant cell lines (0.492±0.024 and 0.378±0.029, respectively), indicating that imatinib mesylate is effective in the treatment of CML regardless of cell chemosensitivity. However, the IC50 for etoposide in sensitive K562 cells was markedly lower than that of K562/ADM cells (50.6±16.5 and 194±8.46 µM, respectively), suggesting that the higher expression levels of MDR1 and/or BCL-2 mRNA in resistant cells may be partially responsible for this effect. This is supported by terminal deoxynucleotidyl transferase dUTP nick-end labeling data, whereby a higher percentage of apoptotic cells were found in the sensitive and resistant K562 cells treated with imatinib mesylate (29.3±0.2 and 31.9±16.7%, respectively), whereas etoposide caused significant apoptosis of sensitive K562 cells (18.3±8.35%) relative to K562/ADM cells (5.17±3.3%). In addition, the MDR genes in K562/ADM cells were knocked down by short interfering RNAs. The percentage knockdowns were 15.4% for MRP1, 17.8% for MDR and 30.7% for BCL-2, which resulted in a non-significant difference in the half maximal inhibitory concentration value of K562/ADM cells relative to K562 cells upon treatment with etoposide.

Associations between post translational histone modifications, myelomeningocele risk, environmental arsenic exposure, and folate deficiency among participants in a case control study in Bangladesh

Arsenic exposure may contribute to disease risk in humans through alterations in the epigenome. Previous studies reported that arsenic exposure is associated with changes in plasma histone concentrations. Posttranslational histone modifications have been found to differ between the brain tissue of human embryos with neural tube defects and that of controls. Our objectives were to investigate the relationships between plasma histone 3 levels, history of having an infant with myelomeningocele, biomarkers of arsenic exposure, and maternal folate deficiency. These studies took place in Bangladesh, a country with high environmental arsenic exposure through contaminated drinking water. We performed ELISA assays to investigate plasma concentration of total histone 3 (H3) and the histone modification H3K27me3. The plasma samples were collected from 85 adult women as part of a case-control study of arsenic and myelomeningocele risk in Bangladesh. We found significant associations between plasma %H3K27me3 levels and risk of myelomeningocele (P<0.05). Mothers with higher %H3K27me3 in their plasma had lower risk of having an infant with myelomeningocele (odds ratio: 0.91, 95% confidence interval: 0.84, 0.98). We also found that arsenic exposure, as estimated by arsenic concentration in toenails, was associated with lower total H3 concentrations in plasma, but only among women with folate deficiency (β = -9.99, standard error = 3.91, P=0.02). Our results suggest that %H3K27me3 in maternal plasma differs between mothers of infants with myelomeningocele and mothers of infants without myelomeningocele, and may be a marker for myelomeningocele risk. Women with folate deficiency may be more susceptible to the epigenetic effects of environmental arsenic exposure.

Influence of Arsenic on Global Levels of Histone Posttranslational Modifications: a Review of the Literature and Challenges in the Field

Arsenic is a human carcinogen and also increases the risk for non-cancer outcomes. Arsenic-induced epigenetic dysregulation may contribute to arsenic toxicity. Although there are several reviews on arsenic and epigenetics, these have largely focused on DNA methylation. Here, we review investigations of the effects of arsenic on global levels of histone posttranslational modifications (PTMs). Multiple studies have observed that arsenic induces higher levels of H3 lysine 9 dimethylation (H3K9me2) and also higher levels of H3 serine 10 phosphorylation (H3S10ph), which regulate chromosome segregation. In contrast, arsenic causes a global loss of H4K16ac, a histone PTM that is a hallmark of human cancers. Although the findings for other histone PTMs have not been entirely consistent across studies, we discuss biological factors which may contribute to these inconsistencies, including differences in the dose, duration, and type of arsenic species examined; the tissue or cell line evaluated; differences by sex; and exposure timing. We also discuss two important considerations for the measurement of histone PTMs: proteolytic cleavage of histones and arsenic-induced alterations in histone expression.

Daunorubicin-Loaded DNA Origami Nanostructures Circumvent Drug-Resistance Mechanisms in a Leukemia Model

Many cancers show primary or acquired drug resistance due to the overexpression of efflux pumps. A novel mechanism to circumvent this is to integrate drugs, such as anthracycline antibiotics, with nanoparticle delivery vehicles that can bypass intrinsic tumor drug-resistance mechanisms. DNA nanoparticles serve as an efficient binding platform for intercalating drugs (e.g., anthracyclines doxorubicin and daunorubicin, which are widely used to treat acute leukemias) and enable precise structure design and chemical modifications, for example, for incorporating targeting capabilities. Here, DNA nanostructures are utilized to circumvent daunorubicin drug resistance at clinically relevant doses in a leukemia cell line model. The fabrication of a rod-like DNA origami drug carrier is reported that can be controllably loaded with daunorubicin. It is further directly verified that nanostructure-mediated daunorubicin delivery leads to increased drug entry and retention in cells relative to free daunorubicin at equal concentrations, which yields significantly enhanced drug efficacy. Our results indicate that DNA origami nanostructures can circumvent efflux-pump-mediated drug resistance in leukemia cells at clinically relevant drug concentrations and provide a robust DNA nanostructure design that could be implemented in a wide range of cellular applications due to its remarkably fast self-assembly (≈5 min) and excellent stability in cell culture conditions.

Dickkopf-3 (Dkk3) induces apoptosis in cisplatin-resistant lung adenocarcinoma cells via the Wnt/β-catenin pathway

Previous studies have shown that Dickkopf‑3 (Dkk3) is inactivated in lung cancer cells, while the inactivation of the Wnt/β‑catenin signaling pathway by Dkk3 inhibits lung cancer progression. In the present study, we investigated whether Dkk3 enhances the sensitivity of lung cancer cells to cisplatin. A549, Calu1 and H460 lung adenocarcinoma cell lines were transfected with DKK3 siRNA, while the cisplatin‑resistant subline A549cis was transfected with DKK3. DKK3 expression was attenuated in A549cis, Calu1cis and H460cis compared to A549, Calu1 and H460, respectively. Lung adenocarcinoma cell growth, proliferation, apoptosis, cell cycle in vitro and in vivo were then analyzed. DKK3 knockdown by siRNA transfection rendered A549, Calu1 and H460 resistant to cisplatin. As a result of DKK3 transfection, the expression of DKK3 and E‑cadherin was significantly upregulated, while that of MMP7, survivin, c‑myc and cyclin D1 was downregulated. DKK3 overexpression retarded cell proliferation, induced cell cycle arrest and apoptosis, and reduced cell invasive ability in the A549 and A549cis cells. In addition, the proportions of apoptotic cells and the PARP level were significantly increased in A549cis‑ and H460cis‑DKK3 cells treated with cisplatin. Moreover, tumor growth was retarded more in cisplatin‑treated nude mice seeded with A549cis‑DKK3 cells than with A549cis cells. Cell viability increased with the pretreatment of SB216763 for 2 h in A549cis and A549cis‑DKK3 cells incubated with cisplatin (1 µM) for 72 h. In conclusion, the re‑activation of Dkk3 enhances the chemosensitivity to cisplatin in cisplatin‑resistant lung adenocarcinoma cell lines, which requires additional studies to realize this potential in clinical use.

Integrating GO and KEGG terms to characterize and predict acute myeloid leukemia-related genes

BACKGROUND/OBJECTIVE

Acute myeloid leukemia (AML) is a progressive and malignant cancer of myelogenous blood cells, which disturbs the production of normal blood cells. Although several risk and genetic factors (AML-related genes) have been investigated, the concrete mechanism underlying the development of AML remains unclear. In view of this, it is crucial to develop an effective computational method for meaningfully characterizing AML genes and accurately predicting novel AML genes.

METHODS

In this study, we integrated gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway annotations as features to characterize AML genes. We also provided an optimal set of features for predicting AML-related genes by using the minimum redundancy maximum relevance (mRMR) algorithm and dagging metaclassifier.

RESULTS

We obtained 26 optimal GO terms that characterized AML genes well. Finally, we predicted 464 novel genes to provide clinical researchers with additional candidates and useful insights for further analysis of AML.

DISCUSSION

An in-depth feature analysis indicated that the results are quite consistent with previous knowledge. We developed a systematic method to identify the possible underlying mechanism of AML by analyzing the related genes. Our method has the ability to identify the types of features that are optimal to meaningfully interpret AML and accurately predict more AML genes for further clinical researches.

VEGF depletion enhances bcr-abl-specific sensitivity of arsenic trioxide in chronic myelogenous leukemia

The development of resistance to imatinib mesylate may partly depend on high bcr-abl expression levels or point mutation(s). Arsenic trioxide (ATO) has bcr-abl suppressing activity in vitro, without cross-resistance to imatinib. Meanwhile, bcr-abl also induces expression of vascular endothelial growth factor (VEGF), which is associated with tumor-related angiogenesis and is involved in chronic myelogenous leukemia (CML) pathogenesis. Here, we investigated ways to improve ATO activity in CML by modulating cellular VEGF levels. K562 and primary CML cells were transfected with a VEGF antisense sequence. Cell viability and survival were assessed using 3-(4,5-dimethylthiazol-2-yl-2,5-diphenyltetrazolium bromide and trypan blue exclusion assays. Apoptotic cells were detected by flow cytometry following annexin V and propidium iodide staining. The results showed that VEGF depletion effectively promotes enhanced ATO antileukemic activity by repressing bcr-abl protein levels. These data provide a rationale for the clinical development of optimized ATO-based regimens that incorporate VEGF modulator for CML treatment.

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.

Magnetic core–shell nanoprobe for sensitive killing of cancer cells via induction with a strong external magnetic field

The title system, composed of a highly magnetic core surrounded by a thin arsenite shell, has been synthesized and applied to the magnetically facilitated targeting of anticancer agent (sodium arsenite) at lower dose with minimal side effects and higher efficacy in a biocompatible manner.

Anticancer activity of small-molecule and nanoparticulate arsenic(III) complexes

Starting in ancient China and Greece, arsenic-containing compounds have been used in the treatment of disease for over 3000 years. They were used for a variety of diseases in the 20th century, including parasitic and sexually transmitted illnesses. A resurgence of interest in the therapeutic application of arsenicals has been driven by the discovery that low doses of a 1% aqueous solution of arsenic trioxide (i.e., arsenous acid) lead to complete remission of certain types of leukemia. Since Food and Drug Administration (FDA) approval of arsenic trioxide (As2O3) for treatment of acute promyelocytic leukemia in 2000, it has become a front-line therapy in this indication. There are currently over 100 active clinical trials involving inorganic arsenic or organoarsenic compounds registered with the FDA for the treatment of cancers. New generations of inorganic and organometallic arsenic compounds with enhanced activity or targeted cytotoxicity are being developed to overcome some of the shortcomings of arsenic therapeutics, namely, short plasma half-lives and a narrow therapeutic window.

Sodium arsenite and arsenic trioxide differently affect the oxidative stress, genotoxicity and apoptosis in A549 cells: an implication for the paradoxical mechanism

Although arsenic toxicity greatly depends on its chemical forms, few studies have taken into account the paradoxical phenomenon which is manifested by that sodium arsenite (NaAsO₂) acts as a potent carcinogen but arsenic trioxide (As₂O₃) serves as an effective therapeutic agent. In this study, we compared the in vitro effects of NaAsO₂ and As₂O₃ on cell viability, colony formation, cell cycle progression, apoptosis, genotoxicity and oxidative stress in human lung adenocarcinoma A549 cells. Our results demonstrated that both NaAsO₂ and As₂O₃ caused oxidative stress, genotoxicity, cytotoxicity, cell cycle arrest as well as apoptosis, while As₂O₃ induced higher production of reactive oxygen species (ROS) with a more remarkable decrease in superoxide dismutase (SOD) activities and intracellular levels of glutathione (GSH) than NaAsO₂. Moreover, the degree of DNA damage, chromosomal breakage, cell cycle arrest and apoptosis in As₂O₃-treated cells were more severe than those in NaAsO₂-treated cells. These findings suggest that differential effects and mechanisms of NaAsO₂ and As₂O₃ may responsible for the paradoxical effects of arsenic on the carcinogenesis and anticancer function.

Effective targeting of chronic myeloid leukemia initiating activity with the combination of arsenic trioxide and interferon alpha

Imatinib is the standard of care in chronic meloid leukemia (CML) therapy. However, imatinib is not curative since most patients who discontinue therapy relapse indicating that leukemia initiating cells (LIC) are resistant. Interferon alpha (IFN) induces hematologic and cytogenetic remissions and interestingly, improved outcome was reported with the combination of interferon and imatinib. Arsenic trioxide was suggested to decrease CML LIC. We investigated the effects of arsenic and IFN on human CML cell lines or primary cells and the bone marrow retroviral transduction/transplantation murine CML model. In vitro, the combination of arsenic and IFN inhibited proliferation and activated apoptosis. Importantly, arsenic and IFN synergistically reduced the clonogenic activity of primary bone marrow cells derived from CML patients. Finally, in vivo, combined interferon and arsenic treatment, but not single agents, prolonged the survival of primary CML mice. Importantly, the combination severely impaired engraftment into untreated secondary recipients, with some recipients never developing the disease, demonstrating a dramatic decrease in CML LIC activity. Arsenic/IFN effect on CML LIC activity was significantly superior to that of imatinib. These results support further exploration of this combination, alone or with imatinib aiming at achieving CML eradication rather than long-term disease control.

Combination of siRNA-directed Kras oncogene silencing and arsenic-induced apoptosis using a nanomedicine strategy for the effective treatment of pancreatic cancer

The synergetic inhibitory effects on human pancreatic cancer by nanoparticle-mediated siRNA and arsenic therapy were investigated both in vitro and in vivo. Poly(ethylene glycol)-block-poly(L-lysine) were prepared to form siRNA-complexed polyplex and poly(ethylene glycol)-block-poly(DL-lactide) were prepared to form arsenic-encapsulated vesicle, respectively. Down-regulation of the mutant Kras gene by siRNA caused defective abilities of proliferation, clonal formation, migration, and invasion of pancreatic cancer cells, as well as cell cycle arrest at the G0/G1 phase, which substantially enhanced the apoptosis-inducing effect of arsenic administration. Consequently, co-administration of the two nanomedicines encapsulating siRNA or arsenic showed ideal tumor growth inhibition both in vitro and in vivo as a result of synergistic effect of the siRNA-directed Kras oncogene silencing and arsenic-induced cell apoptosis. These results suggest that the combination of mutant Kras gene silencing and arsenic therapy using nanoparticle-mediated delivery strategy is promising for pancreatic cancer treatment.

FROM THE CLINICAL EDITOR

Treatment of pancreatic cancer remains a major challenge. These authors demonstrate a method that combines a siRNA-based Kras silencing with arsenic delivery to pancreatic cancer cells using nanoparticles, resulting in enhanced apoptosis induction in the treated cells.

Endoplasmic reticulum stress-mediated apoptosis in imatinib-resistant leukemic K562-r cells triggered by AMN107 combined with arsenic trioxide

The first tyrosine kinase inhibitor (TKI) imatinib mesylate (imatinib) targets the kinase domain of BCR-ABL and induces apoptosis in newly diagnosed chronic myeloid leukaemia (CML). However, resistant and relapse are common problems in imatinib-treated patients. Although second-generation TKI such as AMN107 appears to improve the treatment of CML, TKI resistance and relapse are also frequently occurred in the patients. To test whether arsenic trioxide (ATO) could potentiate the efficacy of AMN107 in imatinib-resistant cells, we conducted a series of assays in TKI-resistant K562-r cells treated with AMN107 and ATO. Based on a time-course cDNA microarray analysis, we found many genes typically involved in the endoplasmic reticulum (ER) stress signalling were significantly up-regulated, implicating the occurrence of ER stress-mediated apoptosis in K562-r cells treated with the combination of ATO and AMN107. Such implication was also supported by the data showing the activation of members in the JNK pathway, which are known to be characteristic markers bridging ER-stress and apoptosis. Partial knock-down of the JNK activities alleviated the effects of apoptosis (p < 0.05) triggered by combining AMN107 with ATO. In conclusion, this study for the first time demonstrates a synergistic effect of AMN107 with ATO, allowing insights into the possible mechanisms underlying imatinib-induced resistance in CML. Our data also suggest that combination of AMN107 with ATO may represent a new strategy for the treatment of imatinib-resistant CML patients.

Systems biology approaches to evaluate arsenic toxicity and carcinogenicity: an overview

Long term exposure to arsenic, either through groundwater, food stuff or occupational sources, results in a plethora of dermatological and non-dermatological health effects including multi-organ cancer and early mortality. Several epidemiological studies, across the globe have reported arsenic-induced health effects and cancerous outcomes; but the prevalence of such diseases varies depending on environmental factors (geographical location, exposure level), and genetic makeup (and variants thereof); which is further modulated by several other factors like ethnicity, age-sex, smoking status, diet, etc. It is also interesting to note that, chronic arsenic exposure to a similar extent, even among the same family members, result in wide inter-individual variations. To understand the adverse effect of this toxic metabolite on biological system (cellular targets), and to unravel the underlying molecular basis (at the level of transcript, proteome, or metabolite), a holistic, systems biology approach was taken. Due to the paradoxical nature and unavailability of any suitable animal model system; the literature review is primarily based on cell line and population based studies. Thus, here we present a comprehensive review on the systems biology approaches to explore the underlying mechanism of arsenic-induced carcinogenicity, along with our own observations and an overview of mitigation strategies and their effectiveness till date.

Cellular redox, epigenetics and diseases

Since the Central dogma of Molecular Biology was proposed about 40 years ago; our understanding of the intricacies of gene regulation has undergone tectonic shifts almost every decade. It is now widely accepted that the complexity of an organism is not directed by the sheer number of genes it carries but how they are decoded by a myriad of regulatory modules. Over the years, it has emerged that the organizations chromatins and its remodeling; splicing and polyadenylation of pre-mRNAs, stability and localization of mRNAs and modulation of their expression by non-coding and miRNAs play pivotal roles in metazoan gene expression. Nevertheless, in spite of tremendous progress in our understanding of all these mechanisms of gene regulation, the way these events are coordinated leading towards a highly defined proteome of a given cell type remains enigmatic. In that context, the structures of many metazoan genes cannot fully explain their pattern of expression in different tissues, especially during embryonic development and progression of various diseases. Further, numerous studies done during the past quarter of a century suggested that the heritable states of transcriptional activation or repression of a gene can be influenced by the covalent modifications of constituent bases and associated histones; its chromosomal context and long-range interactions between various chromosomal elements (Holliday 1987; Turner 1998; Lyon 1993). However, molecular dissection of these phenomena is largely unknown and is an exciting topic of research under the sub-discipline epigenetics (Gasser et al. 1998).

Arsenic trioxide and ascorbic acid interfere with the BCL2 family genes in patients with myelodysplastic syndromes: an ex-vivo study

BACKGROUND

Arsenic Trioxide (ATO) is effective in about 20% of patients with myelodysplasia (MDS); its mechanisms of action have already been evaluated in vitro, but the in vivo activity is still not fully understood. Since ATO induces apoptosis in in vitro models, we compared the expression of 93 apoptotic genes in patients' bone marrow before and after ATO treatment. For this analysis, we selected 12 patients affected by MDS who received ATO in combination with Ascorbic Acid in the context of the Italian clinical trial NCT00803530, EudracT Number 2005-001321-28.

METHODS

Real-time PCR quantitative assays for genes involved in apoptosis were performed using TaqMan® Assays in 384-Well Microfluidic Cards "TaqMan® Human Apoptosis Array".Quantitative RT-PCR for expression of EVI1 and WT1 genes was also performed. Gene expression values (Ct) were normalized to the median expression of 3 housekeeping genes present in the card (18S, ACTB and GAPDH).

RESULTS

ATO treatment induced up-regulation of some pro-apoptotic genes, such as HRK, BAK1, CASPASE-5, BAD, TNFRSF1A, and BCL2L14 and down-regulation of ICEBERG. In the majority of cases with stable disease, apoptotic gene expression profile did not change, whereas in cases with advanced MDS more frequently pro-apoptotic genes were up-regulated. Two patients achieved a major response: in the patient with refractory anemia the treatment down-regulated 69% of the pro-apoptotic genes, whereas 91% of the pro-apoptotic genes were up-regulated in the patient affected by refractory anemia with excess of blasts-1. Responsive patients showed a higher induction of BAD than those with stable disease. Finally, WT1 gene expression was down-regulated by the treatment in responsive cases.

CONCLUSIONS

These results represent the basis for a possible association of ATO with other biological compounds able to modify the apoptotic pathways, such as inhibitors of the BCL2 family.

NCI's provocative questions on cancer: some answers to ignite discussion

National Cancer Institute has announced 24 provocative questions on cancer. Here I try to answer some of them by linking the dots of existing knowledge.

Factors determining sensitivity and resistance of tumor cells to arsenic trioxide

Previously, arsenic trioxide showed impressive regression rates of acute promyelocytic leukemia. Here, we investigated molecular determinants of sensitivity and resistance of cell lines of different tumor types towards arsenic trioxide. Arsenic trioxide was the most cytotoxic compound among 8 arsenicals investigated in the NCI cell line panel. We correlated transcriptome-wide microarray-based mRNA expression to the IC(50) values for arsenic trioxide by bioinformatic approaches (COMPARE and hierarchical cluster analyses, Ingenuity signaling pathway analysis). Among the identified pathways were signaling routes for p53, integrin-linked kinase, and actin cytoskeleton. Genes from these pathways significantly predicted cellular response to arsenic trioxide. Then, we analyzed whether classical drug resistance factors may also play a role for arsenic trioxide. Cell lines transfected with cDNAs for catalase, thioredoxin, or the anti-apoptotic bcl-2 gene were more resistant to arsenic trioxide than mock vector transfected cells. Multidrug-resistant cells overexpressing the MDR1, MRP1 or BCRP genes were not cross-resistant to arsenic trioxide. Our approach revealed that response of tumor cells towards arsenic trioxide is multi-factorial.

Targeting metabolism with arsenic trioxide and dichloroacetate in breast cancer cells

BACKGROUND

Cancer cells have a different metabolic profile compared to normal cells. The Warburg effect (increased aerobic glycolysis) and glutaminolysis (increased mitochondrial activity from glutamine catabolism) are well known hallmarks of cancer and are accompanied by increased lactate production, hyperpolarized mitochondrial membrane and increased production of reactive oxygen species.

METHODS

In this study we target the Warburg effect with dichloroacetate (DCA) and the increased mitochondrial activity of glutaminolysis with arsenic trioxide (ATO) in breast cancer cells, measuring cell proliferation, cell death and mitochondrial characteristics.

RESULTS

The combination of DCA and ATO was more effective at inhibiting cell proliferation and inducing cell death than either drug alone. We examined the effect of these treatments on mitochondrial membrane potential, reactive oxygen species production and ATP levels and have identified new molecular mechanisms within the mitochondria for both ATO and DCA: ATO reduces mitochondrial function through the inhibition of cytochrome C oxidase (complex IV of the electron transport chain) while DCA up-regulates ATP synthase β subunit expression. The potentiation of ATO cytotoxicity by DCA is correlated with strong suppression of the expression of c-Myc and HIF-1α, and decreased expression of the survival protein Bcl-2.

CONCLUSION

This study is the first to demonstrate that targeting two key metabolic hallmarks of cancer is an effective anti-cancer strategy with therapeutic potential.

Epoxyeicosatrienoic acids attenuate reactive oxygen species level, mitochondrial dysfunction, caspase activation, and apoptosis in carcinoma cells treated with arsenic trioxide

Epoxyeicosatrienoic acids (EETs) and the cytochrome P450 epoxygenase CYP2J2 promote tumorogenesis in vivo and in vitro via direct stimulation of tumor cell growth and inhibition of tumor cell apoptosis. Herein, we describe a novel mechanism of inhibition of tumor cell apoptosis by EETs. In Tca-8113 cancer cells, the antileukemia drug arsenic trioxide (ATO) led to the generation of reactive oxygen species (ROS), impaired mitochondrial function, and induced apoptosis. 11,12-EET pretreatment increased expression of the antioxidant enzymes superoxide dismutase and catalase and inhibited ATO-induced apoptosis. 11,12-EET also prevented the ATO-induced activation of p38 mitogen-activated protein kinase, c-Jun NH(2)-terminal kinase, caspase-3, and caspase-9. Therefore, 11,12-EET-pretreatment attenuated the ROS generation, loss of mitochondrial function, and caspase activation observed after ATO treatment. Moreover, the CYP2J2-specific inhibitor compound 26 enhanced arsenic cytotoxicity to a clinically relevant concentration of ATO (1-2 μM). Both the thiol-containing antioxidant, N-acetyl-cysteine, and 11,12-EET reversed the synergistic effect of the two agents. Taken together, these data indicate that 11,12-EET inhibits apoptosis induced by ATO through a mechanism that involves induction of antioxidant proteins and attenuation of ROS-mediated mitochondrial dysfunction.

Reactive oxygen species mediate arsenic induced cell transformation and tumorigenesis through Wnt/β-catenin pathway in human colorectal adenocarcinoma DLD1 cells

Long term exposure to arsenic can increase incidence of human cancers, such as skin, lung, and colon rectum. The mechanism of arsenic induced carcinogenesis is still unclear. It is generally believed that reactive oxygen species (ROS) may play an important role in this process. In the present study, we investigate the possible linkage between ROS, β-catenin and arsenic induced transformation and tumorigenesis in human colorectal adenocarcinoma cell line, DLD1 cells. Our results show that arsenic was able to activate p47(phox) and p67(phox), two key proteins for activation of NADPH oxidase. Arsenic was also able to generate ROS in DLD1 cells. Arsenic increased β-catenin expression level and its promoter activity. ROS played a major role in arsenic-induced β-catenin activation. Treatment of DLD1 cells by arsenic enhanced both transformation and tumorigenesis of these cells. The tumor volumes of arsenic treated group were much larger than those without arsenic treatment. Addition of either superoxide dismutase (SOD) or catalase reduced arsenic induced cell transformation and tumor formation. The results indicate that ROS are involved in arsenic induced cell transformation and tumor formation possible through Wnt/β-catenin pathway in human colorectal adenocarcinoma cell line DLD1 cells.

Antiproliferative and anti-invasive effects of inorganic and organic arsenic compounds on human and murine melanoma cells in vitro

OBJECTIVES

For patients with advanced melanoma, no treatment options are available at present that provide either sufficient response rates or a significant prolongation of overall survival. The present study examines the effects of two inorganic and six organic arsenic compounds on cell proliferation and cell invasion of melanoma cells in vitro.

METHODS

The effects of arsenic compounds on proliferation of human melanoma A375 cells and murine melanoma B16F10 cells were examined by MTT assay and 5-bromo-2'-deoxyuridine (BrdU) incorporation assay, and the effects of the compounds on cell invasion were examined by the Boyden chamber invasion assay. The amounts of active matrix metalloproteinase (MMP)-2 and pro-MMP-2 in the culture supernatant of A375 cells were determined by an MMP-2 activity assay system.

KEY FINDINGS

Arsenate and arsenic trioxide (As(2) O(3) ) inhibited the proliferation of A375 and B16F10 cells significantly at concentration ranges of 0.1-20µg/ml (P<0.001), while the organic compounds arsenobetaine, arsenocholine, dimethylarsinic acid, methylarsonic acid, tetramethylarsonium and trimethylarsine oxide did not show any inhibitory effects even at 20µg/ml. Cell invasion of A375 and B16F10 cells through a layer of collagen IV was significantly inhibited by 0.1-20 µg/ml of arsenate or As(2) O(3) (P<0.05), while the organic compounds did not inhibit cell invasion. Arsenate or As(2) O(3) at 0.2-10µg/ml significantly inhibited the amount of active MMP-2 and pro-MMP-2 secreted into the A375 cell culture supernatant (P<0.05).

CONCLUSIONS

Our findings show that the inorganic arsenic compounds arsenate and As(2) O(3) inhibit cell proliferation and prevent the invasive properties of melanoma cells, possibly by decreasing MMP-2 production from the cells.

Arsenic-induced oxidative stress and its reversibility

This review summarizes the literature describing the molecular mechanisms of arsenic-induced oxidative stress, its relevant biomarkers, and its relation to various diseases, including preventive and therapeutic strategies. Arsenic alters multiple cellular pathways including expression of growth factors, suppression of cell cycle checkpoint proteins, promotion of and resistance to apoptosis, inhibition of DNA repair, alterations in DNA methylation, decreased immunosurveillance, and increased oxidative stress, by disturbing the pro/antioxidant balance. These alterations play prominent roles in disease manifestation, such as carcinogenicity, genotoxicity, diabetes, cardiovascular and nervous systems disorders. The exact molecular and cellular mechanisms involved in arsenic toxicity are rather unrevealed. Arsenic alters cellular glutathione levels either by utilizing this electron donor for the conversion of pentavalent to trivalent arsenicals or directly binding with it or by oxidizing glutathione via arsenic-induced free radical generation. Arsenic forms oxygen-based radicals (OH(•), O(2)(•-)) under physiological conditions by directly binding with critical thiols. As a carcinogen, it acts through epigenetic mechanisms rather than as a classical mutagen. The carcinogenic potential of arsenic may be attributed to activation of redox-sensitive transcription factors and other signaling pathways involving nuclear factor κB, activator protein-1, and p53. Modulation of cellular thiols for protection against reactive oxygen species has been used as a therapeutic strategy against arsenic. N-acetylcysteine, α-lipoic acid, vitamin E, quercetin, and a few herbal extracts show prophylactic activity against the majority of arsenic-mediated injuries in both in vitro and in vivo models. This review also updates the reader on recent advances in chelation therapy and newer therapeutic strategies suggested to treat arsenic-induced oxidative damage.

Arsenic trioxide reduces drug resistance to adriamycin in leukemic K562/A02 cells via multiple mechanisms

The present study aimed to study the mechanisms by which low dose arsenic trioxide (As(2)O(3)) reduces multidrug resistance. The potential influence of As(2)O(3) on cytotoxicity was examined by methyl thiazolyl tetrazolium (MTT) assay and the intracellular mean fluorescence intensity (MFI) of Adriamycin (ADM) was examined by flow cytometry. The gene expression of mdr1 mRNA was determined by RT-PCR. The change of cellular expression levels of drug resistant-related proteins, including P-gp, bcl-2, Topo-II, and GST-π, were measured by Western-blotting or immunocytochemistry assay. Data showed As(2)O(3) at non-cytotoxic concentration (2μM) significantly increased the cytotoxicity of ADM on K562/A02 cells. Cotreatment of As(2)O(3) and ADM significantly increased the ADM MFI than ADM alone (P<0.01). Following pretreatment of K562/A02 cells with As(2)O(3), the expression of Topo-II was increased while the expression of GST-π and bcl-2 was decreased. No obvious alternation of expression of mdr1 mRNA or P-gp was observed. Thus, low dose As(2)O(3) partially reduced drug resistance to ADM in K562/A02 cells via multiple mechanisms, which selectively inhibited the efflux pump GST-π but not P-gp, as well as modulated the expression of MDR-related proteins such as Topo-II and bcl-2, in line with previous studies. In conclusions: The effect of As(2)O(3) on reducing MDR may have wide clinical application in chemotherapy regimens for leukemia.

Resistance to the translation initiation inhibitor silvestrol is mediated by ABCB1/P-glycoprotein overexpression in acute lymphoblastic leukemia cells

Protein synthesis is a powerful therapeutic target in leukemias and other cancers, but few pharmacologically viable agents are available that affect this process directly. The plant-derived agent silvestrol specifically inhibits translation initiation by interfering with eIF4A/mRNA assembly with eIF4F. Silvestrol has potent in vitro and in vivo activity in multiple cancer models including acute lymphoblastic leukemia (ALL) and is under pre-clinical development by the US National Cancer Institute, but no information is available about potential mechanisms of resistance. In a separate report, we showed that intraperitoneal silvestrol is approximately 100% bioavailable systemically, although oral doses were only 1% bioavailable despite an apparent lack of metabolism. To explore mechanisms of silvestrol resistance and the possible role of efflux transporters in silvestrol disposition, we characterized multi-drug resistance transporter expression and function in a silvestrol-resistant ALL cell line generated via culture of the 697 ALL cell line in gradually increasing silvestrol concentrations. This resistant cell line, 697-R, shows significant upregulation of ABCB1 mRNA and P-glycoprotein (Pgp) as well as cross-resistance to known Pgp substrates vincristine and romidepsin. Furthermore, 697-R cells readily efflux the fluorescent Pgp substrate rhodamine 123. This effect is prevented by Pgp inhibitors verapamil and cyclosporin A, as well as siRNA to ABCB1, with concomitant re-sensitization to silvestrol. Together, these data indicate that silvestrol is a substrate of Pgp, a potential obstacle that must be considered in the development of silvestrol for oral delivery or targeting to tumors protected by Pgp overexpression.

Arsenite-induced apoptosis is prevented by selenite in A375 cell line

Arsenic trioxide induces apoptosis and clinical remission in patients diagnosed with acute promyelocytic leukemia. The human malignant melanoma A375 cells were treated with NaAsO2 (0.1–130 μM) and also treated with combined 10 μM NaAsO2 and 10 μM Na2SeO3. NaAsO2 arrested cell growth in the G1 phase and induced apoptosis in a concentration- and time-dependent manner. In contrast, administration of Na2SeO3 antagonized the cell growth inhibition and apoptosis induced by NaAsO2. The NaAsO2 treatment resulted in a marked increase in p53 protein as early as 4 h and in Bcl-2 protein level by 12 h. In addition, p53 downregulation accompanied the combined treatment of NaAsO2 and Na2SeO3. Thus, our results indicate upregulation of p53 and Bcl-2 play acrucial role in the NaAsO2-induced G1 arrest and apoptosis of A375 cells and that downregulation p53 appears to contribute to the inhibition by Na2SeO3 of the effects induced by NaAsO2.

Arsenic trioxide cooperates with all trans retinoic acid to enhance mitogen-activated protein kinase activation and differentiation in PML-RARalpha negative human myeloblastic leukemia cells

Arsenic trioxide (ATO) synergistically promotes all trans retinoic acid (ATRA)-induced differentiation of PML-RARalpha negative HL-60 myeloblastic leukemia cells. In PML-RARalpha positive myeloid leukemia cells, ATO is known to cause degradation of PML-RARalpha with subsequent induced myeloid differentiation. We found that ATO by itself does not cause differentiation of the PML-RARalpha negative HL-60 cells, but enhances ATRA's capability to cause differentiation. ATO augmented ATRA-induced RAF/MEK/ERK axis signaling, expression of CD11b and p47(PHOX), and inducible oxidative metabolism. ATO enhanced ATRA-induced population growth retardation without evidence of apoptosis or enhanced G1/G0 growth arrest. Compared to ATRA-treated cells, the ATRA plus ATO-treated cells progressed more slowly through the cell cycle as detected by a slower rate of accumulation in G2/M following nocodazole treatment. Hoechst/PI staining showed that low-dose ATO did not induce apoptosis. In summary, our results indicate that ATO in conjunction with ATRA is of potential chemotherapeutic use in PML-RARalpha negative leukemias.

E3 ubiquitin ligase Cbl-b potentiates the apoptotic action of arsenic trioxide by inhibiting the PI3K/Akt pathway

Arsenic trioxide (ATO) is a strong inducer of apoptosis in malignant hematological cells. Inducible phosphatidyl inositol 3 kinase (PI3K)-Akt activation promotes resistance to ATO. In the present study, we evaluated whether E3 ubiquitin ligase Cbl-b, a negative regulator of PI3K activation, is involved in the action of ATO. The effect of ATO on cell viability was measured by the Trypan blue exclusion assay or by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. Apoptosis was determined by flow cytometry and protein expression was assayed by Western blotting. ATO decreased the viability of HL60 cells and induced cellular apoptosis, which was accompanied by transient activation of Akt. The PI3K/Akt inhibitor, LY294002, significantly increased ATO-induced apoptosis (P < 0.05). In addition, ATO up-regulated the expression of Cbl-b proteins. Furthermore, ATO inhibited cell viability with an IC50 of 18.54 μM at 24 h in rat basophilic leukemia-2H3 cells. ATO induced cellular apoptosis with transient activation of Akt and Cbl-b was also up-regulated. Rat basophilic leukemia-2H3 cells transfected with a dominant negative (DN) Cbl-b mutation showed overexpression of Cbl-b (DN) and enhanced Akt activation. Compared with cells transfected with vector, ATO-induced apoptosis was decreased and G2/M phase cells were increased at the same concentration (P < 0.05). The PI3K/Akt inhibitor, LY294002, re-sensitized Cbl-b (DN) overexpressing cells to ATO and reversed G2/M arrest (P < 0.05). Taken together, these results suggest that Cbl-b potentiates the apoptotic action of ATO by inhibition of the PI3K/Akt pathway.

Evaluation of the serum catalase and myeloperoxidase activities in chronic arsenic-exposed individuals and concomitant cytogenetic damage

Chronic arsenic exposure through contaminated drinking water is a major environmental health issue. Chronic arsenic exposure is known to exert its toxic effects by a variety of mechanisms, of which generation of reactive oxygen species (ROS) is one of the most important. A high level of ROS, in turn, leads to DNA damage that might ultimately culminate in cancer. In order to keep the level of ROS in balance, an array of enzymes is present, of which catalase (CAT) and myeloperoxidase (MPO) are important members. Hence, in this study, we determined the activities of these two enzymes in the sera and chromosomal aberrations (CA) in peripheral blood lymphocytes in individuals exposed and unexposed to arsenic in drinking water. Arsenic in drinking water and in urine was used as a measure of exposure. Our results show that individuals chronically exposed to arsenic have significantly higher CAT and MPO activities and higher incidence of CA. We found moderate positive correlations between CAT and MPO activities, induction of CA and arsenic in urine and water. These results indicate that chronic arsenic exposure causes higher CAT and MPO activities in serum that correlates with induction of genetic damage. We conclude that the serum levels of these enzymes might be used as biomarkers of early arsenic exposure induced disease much before the classical dermatological symptoms of arsenicosis begin to appear.

Synergistic antiproliferative effect of arsenic trioxide combined with bortezomib in HL60 cell line and primary blasts from patients affected by myeloproliferative disorders

Both arsenic trioxide (ATO) and bortezomib show separate antileukemic activity. With the purpose of evaluating whether the combination of ATO and bortezomib would be an option for patients with acute leukemia, we incubated HL60 leukemic cells with ATO alone and in combination with bortezomib. ATO and bortezomib cooperated to induce cell death and to inhibit proliferation and apoptosis in a synergistic way. The combined treatment resulted in a stronger activation of caspase 8 and 9, moderate activation of caspase 3, and increased expression of Fas and tumor necrosis factor-related apoptosis-inducing ligand (TRAIL)-DR5 receptors. When bortezomib was added, some proapoptotic genes (CARD9, TRAIL) were upregulated, and some antiapoptotic genes (BCL2, BCL3, FLICE) were downregulated. When coincubated, approximately 80% of cells showed altered mitochondrial membrane permeability. Moreover, ATO alone and in combination with bortezomib abrogated DNA-binding activity of nuclear factor kappa beta (NF-kappaB). Gene expression assays showed that more deregulated genes were related to proliferation of leukocytes, tumorigenesis, control of cell cycle, hypoxia and oxidative stress, cytokines, PI3K-AKT, ERK-MAPK, EGF pathways, and ubiquitination. Finally, in three cases of acute myeloid leukemia, the addition of bortezomib to ATO significantly increased cytotoxicity. We conclude that the combination of bortezomib and ATO may be efficacious in the treatment of myeloid disorders.