Treatment of acute promyelocytic leukemia with arsenic compounds: in vitro and in vivo studies

AQP9 (Aquaporin 9) Determines Arsenic Uptake and Tolerance in Human Hepatocellular Carcinoma Cells In Vitro

Arsenic-based therapeutic strategies, even though promising for acute promyelocytic leukemia (APL), are limited by arsenic-related toxic effect and resistance with unknown mechanisms. The purpose of this study is to better understand the different sensitivities of hepatocellular carcinoma cells to arsenic and its mechanism. Arsenic-sensitive liver cancer cell line (HepG2) and arsenic-resistant HepG2 (AsHepG2) cells are employed to study the role of aquaporin 9 (AQP9) in arsenic uptake and tolerance. The half-maximal inhibitory concentration (IC₅₀) value of arsenic in AsHepG2 cells (15.59 ± 1.36 µM) is significantly higher than that in HepG2 cells (7.33 ± 0.93 µM; p= 0.0288). We demonstrated that, with the treatment of sodium arsenite (NaAsO₂), arsenic was accumulated at a significantly lower level in AsHepG2 cells in comparison with HepG2 cells (p= 0.00549). Further, arsenic level in AsHepG2 cells reaches a plateau after six hours of treatment, whereas arsenic continues to increase in HepG2 cells during the entire experimental period. Mechanistic study showed that the expression of AQP9 is decreased in a dose-dependent manner in AsHepG2 cells, but no significant difference in HepG2 cells. Furthermore, NaAsO₂ dramatically increases AQP9 and p38 phosphorylation, which may partially regulate arsenic sensitivity in both cell lines. In conclusion, the expression and phosphorylation of AQP9 regulated by p38 kinase are involved in the arsenic uptake, thus regulating cellular arsenic sensitivity.

Acute myeloid leukemia in an 86-year-old man with AML1/ETO treated with Homoharringtonine and Arsenic Trioxide: A case report

RATIONALE

Acute myeloid leukemia (AML) is a malignantly clonal and highly heterogeneous disease. Although the treatment of AML has brought promising outcomes for younger patients, prognosis of the elderly remains dismal. Innovative regimens are increasingly necessary to be investigated.

PATIENT CONCERNS

We present an 86-year-old AML patient with fever, cough, and sputum production.

DIAGNOSES

A diagnosis of AML with maturation (AML-M2) and AML1/ETO was made.

INTERVENTIONS

The patient was treated with a regimen of Homoharringtonine coupled with arsenic trioxide.

OUTCOMES

The AML-M2 patient with AML1/ETO achieved incomplete remission, but showed few toxic side effects and improved survival. Besides, we analyzed the dynamic counts of complete blood cells during the treatment. The count of white blood cell had a positive correlation with the percentage of blast cells (r = 0.65), both of which had a negative correlation with the percentage of segmented neutrophils (r = -0.63, -0.89).

LESSONS

Homoharringtonine and arsenic trioxide may induce both the apoptosis and differentiation of leukemic cells in AML-M2 with AML1/ETO.

Tetra-arsenic tetra-sulfide ameliorates lupus syndromes by inhibiting IL-17 producing double negative T cells

Systemic lupus erythematosus (SLE) is an autoimmune disease of uncertain etiology that affects multiple tissues and organs. Tetra-arsenic tetra-sulfide (As₄ S₄ ), a traditional Chinese medicine, is effective on acute promyelocytic leukemia with mild side effects. In our previous study, BXSB lupus-prone mice treated with As₄ S₄ has showed improved monocytosis, decreased serum interleukin (IL)-6 and suppressed skin, liver and renal lesions with well-tolerance. In this study, we explored the effect and mechanism of As₄ S₄ on the MRL/lpr mice. MRL/lpr and wild MRL/MpJ mice were divided into control and As₄ S₄ treatment groups and dosed with As₄ S₄ or placebo for 8 weeks. We found that As₄ S₄ prevented the skin, renal and lung lesions of MRL/lpr mice. As₄ S₄ significantly decreased the double negative T (DN T) cells and reduced the serum levels of IL-17, IL-10, and antinuclear antibodies titer. Further results revealed that the FasL was decreased, and activated caspases elevated in DN T cells in As₄ S₄ treated MRL/lpr mice. Taken together, As₄ S₄ could selectively suppresses DN T cells by inducing apoptosis. It also reduced inflammatory cytokines IL-17, which may be produced by DN T cells. As₄ S₄ may represent a new therapy for SLE.

Activation of integrated stress response pathway regulates IL-1β production through posttranscriptional and translational reprogramming in macrophages

Immune cells sense and programme its cellular machinery appropriately to the environmental changes through the activation of cytoprotective adaptive pathway so-called the "integrated stress response (ISR)". However, the mechanisms implicated in ISR-induced protective responses are poorly understood. Here, we show that ISR activation by arsenite (Ar) results in suppression of IL-1β production in macrophages and inhibition of DSS-induced colitis in a murine model through a novel posttranscriptional and translation regulatory (PTR) mechanism. Ar triggers PTR events through eIF2α-phosphorylation, which results in the attenuation of active polysome formation leading to the accumulation of translationally stalled IL-1β mRNAs. Translationally stalled IL-1β mRNAs recruit RNA-binding proteins (TIA-1/TIAR), resulting in the formation of RBP-RNA complexes known as stress granules (SGs). The SGs bound IL-1β mRNAs might undergo degradation through induction of autophagy. Also, we show that Ar posttranslationally impairs processing and secretion of IL-1β by diminishing inflammasome activation. Altogether, this study unveils a novel mechanism of IL-1β regulation and further suggests that pharmacological activation of cytoprotective ISR pathway might provide an effective therapeutic intervention against inflammatory diseases.

Synergistic antitumor activity of oridonin and valproic acid on HL-60 leukemia cells

BACKGROUND

Oridonin is a diterpenoid isolated from Rabdosia rubescens with potent anticancer activities. Valproic acid (VPA) is a recently emerged antineoplastic histone deacetylase inhibitor. The aim of the present study is to investigate the synergistic role of oridonin and VPA to inhibit the growth and metastasis of human leukemia cells.

METHODS

The effect of oridonin and VPA on proliferation was evaluated by the MTT assay. Cell migration and invasion were evaluated by transwell and scratch assays, respectively. In addition, cell apoptosis was examined by flow cytometry. The inhibitive effects of oridonin and VPA in vivo were determined by using xenografted nude mice.

RESULTS

The results demonstrated that oridonin in combination with VPA synergistically inhibited the proliferation of HL-60 cells, and induced obvious caspase-dependent apoptosis through activation of the intrinsic apoptosis pathway, which is involved in the downregulation of Bcl-2/Bax ratio. Furthermore, the combination treatment in vivo remarkably reduced the xenograft tumor size and triggered tumor cell apoptosis.

CONCLUSION

Our results suggested that the novel combination of oridonin plus VPA exerted synergistic antiproliferative and apoptosis-inducing effects on human myeloid leukemia cells, and may serve as a potentially promising antileukemia strategy.

Arsenic-induced apoptosis in the p53-proficient and p53-deficient cells through differential modulation of NFkB pathway

Arsenic is a well-known environmental carcinogen and an effective chemotherapeutic agent. The underlying mechanism of this dual-effect, however, is not fully understood. In this study, we applied mouse p53^+/+ and p53^-/- cells to examine the NFκB pathway and proinflammatory cytokines after arsenic treatment. Arsenic reduced cell viability and increased more apoptosis in the p53-/- cells as compared to p53+/+ cells, which was correlated with activation of SAPK/JNK, p38 MAPK, and AKT pathways. A transcriptional regulatory network analysis revealed that arsenic activated transcription regulatory elements E2F, Egr1, Trp53, Stat6, Bcl6, Creb2 and ATF4 in the p53+/+ cells, while in the p53-/- cells, arsenic treatment altered transcription factors NFκB, Pparg, Creb2, ATF4, and Egr1. We observed dynamic changes in phosphorylated NFκB p65 (p-NFκB p65) and phosphorylated IKKαβ (p-IKKαβ) in both genotypes from 4 h to 24 h after treatment, significant decreases of p-NFκB p65 and p-IKKαβ in the p53-/- cells, whereas increases of p-NFκB p65 and p-IKKαβ were observed in the p53+/+ cells. Our study confirmed the differential modulation of NFκB pathway by arsenic in the p53+/+ or p53-/- cells and this observation of the differential mechanism of cell death between the p53+/+ and p53-/- cells might be linked to the unique ability of arsenic to act as both a carcinogen and a chemotherapeutic agent.

A novel combination of oridonin and valproic acid in enhancement of apoptosis induction of HL-60 leukemia cells

Oridonin, obtained from the traditional Chinese herbal medicine rabdosia rubescens, exerts potent antitumor activities in cancer cells. Valproic acid (VPA), as a potent histone deacetylase inhibitor (HDACI), also plays an important role in inhibition of proliferation of tumor cells. However, there are no reports so far on the cooperation between oridonin and VPA for anti-leukemic effect. Therefore, in the present study, we undertook experiments to determine whether lower concentration of oridonin in conjunction with lower concentration of VPA would produce even more encouraging synergistic effect than each of them alone, and to clarify its molecular mechanism. The results demonstrated that the lower concentration of oridonin in combination with lower concentration of VPA synergistically inhibited the proliferation of HL-60 cells, and induced obvious caspase-dependent apoptosis through activation of the intrinsic apoptosis pathway, which is involved in the downregulation of Bcl-2/Bax ratio, release of cytochrome c to cytosol and caspase-9 activation, as well as through the extrinsic apoptosis pathway mediated by Fas/FasL and caspase-8 activation. In addition, MAPK signaling pathway was also involved in apoptosis induced by oridonin plus VPA. Furthermore, the combination treatment in vivo remarkably reduced the xenograft tumor size and triggered tumor cell apoptosis. Taken together, the novel combination of oridonin plus VPA exerted synergistic anti-proliferative and apoptosis-inducing effects on human myeloid leukemia cells, and may serve as a potential promising anti-leukemia strategy.

ANXA1 silencing increases the sensitivity of cancer cells to low-concentration arsenic trioxide treatment by inhibiting ERK MAPK activation

AIMS AND BACKGROUND

Arsenic trioxide (ATO), an antitumor agent, is widely used for treating acute promyelocytic leukemia (APL), in which it induces apoptosis. In most solid tumors, ATO disturbs the cell cycle instead of inducing apoptosis. We aimed to determine the exact mechanism underlying the different response of APL to ATO compared with the response of solid tumors.

METHODS

A proteomics-based screening was used to identify the ATO-associated proteins in the human esophageal squamous cell carcinoma cell line, Eca109. The expression levels of Annexin A1 (ANXA1) in 4 different types of cancer cells were determined by quantitative reverse transcription polymerase chain reaction and Western blotting. Human esophageal squamous cell carcinoma cell line Eca109 and pancreatic carcinoma cell line BxPC3 cells were transfected with siRNAs targeting ANXA1 and scrambled control siRNA. Cell proliferation was evaluated by methyl thiazolyl tetrazolium assay.

RESULTS

After verification of the mRNA and protein levels in 4 cancer cell lines, ANXA1 and lamin A/B were validated to have increased expression levels after low-concentration ATO treatment. Lower concentrations of ATO, which has no effect on proliferation of cancer cells, induced apoptosis after ANXA1 silencing. Furthermore, overexpression of ANXA1 induced by ATO resulted in activation of extracellular signal-regulated kinase (ERK) mitogen-activated protein kinases (MAPKs), rendering cancer cells resistant to the agent. In addition, PD98059, a specific ERK inhibitor, increased the sensitivity of cancer cells to a lower concentration of ATO treatment.

CONCLUSIONS

Taken together, these data indicate that overexpression of ANXA1 induced by low-concentration ATO makes cancer cells more resistant to the agent via activated ERK MAPKs. Specific silencing of ANXA1 increased the sensitivity of cancer cells to ATO treatment.

Perspectives of differentiation therapies of acute myeloid leukemia: the search for the molecular basis of patients' variable responses to 1,25-dihydroxyvitamin d and vitamin d analogs

The concept of differentiation therapy of cancer is ~40 years old. Despite many encouraging results obtained in laboratories, both in vitro and in vivo studies, the only really successful clinical application of differentiation therapy was all-trans-retinoic acid (ATRA)-based therapy of acute promyelocytic leukemia (APL). ATRA, which induces granulocytic differentiation of APL leukemic blasts, has revolutionized the therapy of this disease by converting it from a fatal to a curable one. However, ATRA does not work for other acute myeloid leukemias (AMLs). Since 1,25-dihydroxyvitamin D₃ (1,25D) is capable of inducing monocytic differentiation of leukemic cells, the idea of treating other AMLs with vitamin D analogs (VDAs) was widely accepted. Also, some types of solid cancers responded to in vitro applied VDAs, and hence it was postulated that VDAs can be used in many clinical applications. However, early clinical trials in which cancer patients were treated either with 1,25D or with VDAs, did not lead to conclusive results. In order to search for a molecular basis of such unpredictable responses of AML patients toward VDAs, we performed ex vivo experiments using patient’s blast cells. Experiments were also performed using 1,25D-responsive and 1,25D-non-responsive cell lines, to study their mechanisms of resistance toward 1,25D-induced differentiation. We found that one of the possible reasons might be due to a very low expression level of vitamin D receptor (VDR) mRNA in resistant cells, which can be increased by exposing the cells to ATRA. Our considerations concerning the molecular mechanism behind the low VDR expression and its regulation by ATRA are reported in this paper.

Acute promyelocytic leukemia: A model of molecular target based therapy

Leukemia, a group of hematological malignancies characterized by clonal expansion of hematopoietic cells with uncontrolled proliferation, decreased apoptosis and blocked differentiation, is one of the most notorious enemies of mankind which accounts for some 300,000 new cases and 222,000 deaths each year worldwide. Leukemia can be divided into acute or chronic, lymphoid or myeloid types, based on the disease progression and hematopoietic lineages involved 5. The responses of leukemia to therapies differ from one type or subtype to another. Hence, to improve the clinical outcome, the therapeutic strategies should be disease pathogenesis-based and individualized. The close collaboration between bench and bedside may not only shed new lights on leukemogenesis, gain insights into therapeutic mechanisms, but also provide opportunities for designing more rational therapies. The development of curative approaches for acute promyelocytic leukemia (APL) may serve as a paradigm.

The two opposite facets of arsenic: toxic and anticancer drug

Arsenic compounds have been known and used for centuries but their effects in living organisms still represent a large unknown. Arsenic compounds have paradoxical effects: they are threatening to human health, especially upon long-term exposure that can induce the development of cancer; however, they are used as drugs against cancer. This review focuses on the effects shown by clinically and environmentally relevant arsenic compounds in living organisms with a focus on the calcium–apoptosis link.

Arsenic methylation metabolism and liver injury of acute promyelocytic leukemia patients undergoing arsenic trioxide treatment

Although arsenic is effective in the treatment of acute promyelocytic leukemia (APL), as a well-known environmental toxicant, the side effects of arsenic treatment and arsenic methylation metabolism of the patients are rarely reported. In this manuscript, we investigated 23 APL patients treated with 10 mg arsenic trioxide daily, detected the arsenic metabolites in urine samples collected on the 0, 10th, and 20th day of arsenic treatment. At the same time, liver function and blood routine examination were also investigated in these APL patients. We found that, urinary monomethylated arsenic proportion (MMA%) increased, but dimethylated arsenic proportion (DMA%), the first methylation ratio (FMR) and the secondary methylation ratio (SMR) decreased with consecutive administration of arsenic trioxide. After adjustment for age impact, no statistical difference was observed in urinary arsenic concentrations and arsenic methylation capacity between male and female at the same treatment time point. During arsenic trioxide treatment of APL, transient elevation of serum aminotransferases was found in the blood samples, which indicated that liver injury occurred and probably reversible. Leukocytosis developed in 5 of the 23 patients with the administration of arsenic trioxide. No statistical difference was observed in the other blood routine examination parameters. These results demonstrated that the capacity of arsenic methylation decreased and transient liver injury occurred during arsenic trioxide treatment of APL, which indicated that the side effects of clinical arsenic treatment can not be ignored.

Inhibition of AKT enhances mitotic cell apoptosis induced by arsenic trioxide

Accumulated evidence has revealed a tight link between arsenic trioxide (ATO)-induced apoptosis and mitotic arrest in cancer cells. AKT, a serine/threonine kinase frequently over-activated in diverse tumors, plays critical roles in stimulating cell cycle progression, abrogating cell cycle checkpoints, suppressing apoptosis, and regulating mitotic spindle assembly. Inhibition of AKT may therefore enhance ATO cytotoxicity and thus its clinical utility. We show that AKT was activated by ATO in HeLa-S3 cells. Inhibition of AKT by inhibitors of the phosphatidyl inositol 3-kinase/AKT pathway significantly enhanced cell sensitivity to ATO by elevating mitotic cell apoptosis. Ectopic expression of the constitutively active AKT1 had no effect on ATO-induced spindle abnormalities but reduced kinetochore localization of BUBR1 and MAD2 and accelerated mitosis exit, prevented mitotic cell apoptosis, and enhanced the formation of micro- or multi-nuclei in ATO-treated cells. These results indicate that AKT1 activation may prevent apoptosis of ATO-arrested mitotic cells by attenuating the function of the spindle checkpoint and therefore allowing the formation of micro- or multi-nuclei in surviving daughter cells. In addition, AKT1 activation upregulated the expression of aurora kinase B (AURKB) and survivin, and depletion of AURKB or survivin reversed the resistance of AKT1-activated cells to ATO-induced apoptosis. Thus, AKT1 activation suppresses ATO-induced mitotic cell apoptosis, despite the presence of numerous spindle abnormalities, probably by upregulating AURKB and survivin and attenuating spindle checkpoint function. Inhibition of AKT therefore effectively sensitizes cancer cells to ATO by enhancing mitotic cell apoptosis.

Tumor growth inhibition of metastatic nasopharyngeal carcinoma cell lines by low dose of arsenic trioxide via alteration of cell cycle progression and induction of apoptosis

BACKGROUND

Although arsenic trioxide (ATO) has displayed anticancer activity against primary nasopharyngeal carcinoma (NPC), its efficacy in metastatic NPC deserved further investigation because the biological/therapeutic difference in cancer cells probably exists between primary and distant sites.

METHODS

Two human metastatic NPC cell lines (NPC-BM1 and NPC-BM2) were investigated. We measured cellular proliferation, cell cycle, and apoptotic extent of BM1 and BM2 cells treated with ATO in vitro. Furthermore, we evaluated the tumor growth after ATO treatment in vivo.

RESULTS

Low-dose ATO treatment is sufficient to induce an antiproliferative effect, alter the cell cycle, and increase apoptosis in BM1 and BM2 cells. BM1 tumor growth in a xenograft model with low-dose and short-schedule (1 mg/kg/day, intraperitoneal injection for 5 consecutive days) of ATO treatment significantly slowed in vivo.

CONCLUSION

ATO at low dose seems to be an encouraging schedule for palliative treatment of metastatic NPC.

Biological effects of Atra and Arsenic Trioxide on short term cultures of non-M3 leukemic blasts

The efficacy of All-Trans Retinoic Acid (Atra) and Arsenic Trioxide (As(2)O(3)) in the treatment of Acute Promyelocytic Leukemia (APL) is well known. Further, these drugs inhibit cell growth and induce apoptosis in several cell lines, but few data are reported on leukemic blasts. The aim of this study was to evaluate the biological effects on non-M3 Acute Myeloid Leukemia (AML) cells. Blasts of six patients, after exposition to Atra and As(2)O(3) were tested for growth inhibition, induction of apoptosis and change in cell cycle distribution, evaluating cell viability, percentage of apoptotic cells and of blasts positive for Ki-67 and BrdU. In the present study we demonstrated that either Atra or As(2)O(3) inhibit leukemic cells proliferation by induction of apoptosis. The effects are time and dose dependent. We did not observe additive or synergistic effects with the combination of the drugs. Further, our results showed that Atra and As(2)O(3) have effects on cell cycle distribution reducing S-phase and proliferating cells. These results should be taken in to account preparing future laboratory and clinical experimental protocols that associate these drugs with antineoplastic agents with different cell cycle specificity.

Sodium selenite induces apoptosis by ROS-mediated endoplasmic reticulum stress and mitochondrial dysfunction in human acute promyelocytic leukemia NB4 cells

INTRODUCTION

In this study, we delineated the apoptotic signaling pathways activated by sodium selenite in NB4 cells.

MATERIALS AND METHODS

NB4 cells were treated with 20 microM sodium selenite for different times. The activation of caspases and ER stress markers, ROS levels, mitochondrial membrane potential and cell apoptosis induced by sodium selenite were analyzed by immunoblotting analysis, DCF fluorescence and flow cytometric respectively. siRNA was used to detect the effect of GADD153 on selenite-induced cell apoptosis.

CONCLUSIONS

Sodium selenite-induced reactive oxygen species generation is an early event that triggers endoplasmic reticulum stress mitochondrial apoptotic pathways in NB4 cells.

Hypoxia-HIF-1alpha-C/EBPalpha/Runx1 signaling in leukemic cell differentiation

Acute myeloid leukemia (AML), a class of prevalent hematopoietic malignancies, is caused by the acquisition of gene mutations that confer deregulated proliferation, impaired differentiation and a survival advantage of hematopoietic progenitors. More recently, we reported that cobalt chloride (CoCl(2))/iron chelator desferrioxamine (DFO)-mimicked hypoxia or moderate hypoxia (2% and 3% O(2)) can directly trigger differentiation of many subtypes of AML cells. Also, intermittent hypoxia significantly prolongs the survival of the transplanted leukemic mice with differentiation induction of leukemic cells. Additionally, these hypoxia-simulating agents selectively stimulate differentiation in acute promyelocytic leukemic cells induced by arsenic trioxide, an effective second-line drug for this unique type of leukemia. Based on this interesting evidence in vitro and in vivo, the ongoing investigations showed the role of hypoxia-inducible factor-1alpha (HIF-1alpha) protein through its non-transcriptional activity in myeloid cell differentiation, as evidenced by chemical interference, the conditional HIF-1alpha induction, the specific short hairpin RNAs (shRNAs) against HIF-1alpha and HIF-1beta, an essential partner for transcription activity of HIF-1. Furthermore, HIF-1alpha and two hematopoietic transcription factors CCAAT/enhancer binding protein alpha (C/EBPalpha) and Runx1/AML1 interact directly with each other. Such interactions increase the transcriptional activities of C/EBPalpha and Runx1/AML1, while C/EBPalpha competes with HIF-1beta for direct binding to HIF-1alpha protein, and significantly inhibits the DNA-binding ability of HIF-1. As a protein is rapidly responsive to all-trans retinoic acid (ATRA), a classical clinical differentiation-inducing drug for AML, HIF-1alpha also plays a role in ATRA-induced differentiation of leukemic cells.

Increased aquaglyceroporin 9 expression disrupts arsenic resistance in human lung cancer cells

Resistance to chemotherapy is one of the major problems in treatment responses of lung cancer. This study explored the mechanism underlying the arsenic resistance of lung cancer. Four lung cancer cells with different proliferation activity were characterized for cytotoxicity, arsenic influx/efflux, and arsenic effects on intracellular glutathione and 8-hydroxy-2'-deoxyguanosine (8-OHdG) production. Our data revealed that relative proliferation potency of these cells was H1299>A549>CL3>H1355. Moreover, A549, H1299, and H1355 were markedly resistant to As(2)O(3) with IC50 approximately 100 microM, whereas CL3 was sensitive to As(2)O(3) with IC50 approximately 11.8 microM. After treatment with the respective As(2)O(3) at IC50, arsenic influx/efflux activity in CL3 was comparable to those in the other three arsenic-resistant cells. However, differences in glutathione levels and 8-OHdG production were also detected either before or after arsenic treatment, indicating that a certain degree of variation in anti-oxidative systems and/or 8-OHdG repair activity existed in these cell lines. By transfection of an aquaglyceroporin 9 (AQP9) gene, we showed that increased AQP9 expression significantly enhanced arsenic uptake and disrupted arsenic resistance of A549. The present study strongly suggests that membrane transporters responsible for arsenic uptake, such as AQP9, may play a critical role in development of arsenic resistance in human lung cancer cells.

Arsenic trioxide-induced apoptosis in H9c2 cardiomyocytes: implications in cardiotoxicity

Arsenic trioxide (As(2)O(3)) achieved dramatic remissions in patients with acute promyelocytic leukaemia. Clinical reports have shown that treatment was associated with cardiotoxicity. We investigated the toxic mechanisms of As(2)O(3) in H9c2 cardiomyocytes. Clinically relevant concentrations of As(2)O(3) (2-10 microM) reduced the viability of H9c2 cells in a concentration-dependent manner. The decreased cell viability was because As(2)O(3) induced cell apoptosis (cell shrinkage, nuclear alterations and caspase-3 activation), or even necrosis at higher concentrations. Inhibition of caspase-3 with a specific inhibitor, Ac-DEVD-CHO, suppressed apoptosis induced by As(2)O(3). In addition, reactive oxygen species formation and cellular Ca(2+) overload were observed in H9c2 cells exposed to As(2)O(3), which was partly inhibited by vitamin E and verapamil. These results suggest that As(2)O(3)-induced cardiotoxicity is mediated, at least in part, by activation of caspase-3 pathway, which may be triggered by reactive oxygen species formation and intracellular Ca(2+) overload.

Emodin-induced generation of reactive oxygen species inhibits RhoA activation to sensitize gastric carcinoma cells to anoikis

RhoA is a critical signaling molecule regulating a variety of cellular processes, such as cytoskeletal organization, adhesion, and apoptosis. It is recently considered responsive to reactive oxygen species (ROS). Nevertheless, how RhoA regulates anoikis, a detachment-initiated apoptosis, and how this regulation is affected by ROS are not clear. The present study investigated the role of RhoA in apoptosis/anoikis in gastric cancer cells and the changes of RhoA and anoikis under oxidative stress. Immunohistochemistry showed that RhoA expression was upregulated in the primary gastric carcinoma compared with normal gastric mucosa. Overactivation of RhoA by transfection with the V14RhoA mutant prevented gastric cancer line SGC-7901 cells from arsenic-induced apoptosis and conferred anoikis resistance through, at least in part, promoting formations of F-actin fibers and focal adhesion. Oxidative stress caused by emodin, an ROS producer, in combination with arsenic trioxide (ATO) led to RhoA inactivation that triggered structural disruption of focal adhesion complex and eventually resulted in anoikis, and these effects could be partially reversed by antioxidant N-acetylcysteine (NAC). In conclusion, activation of RhoA is required for the maintenance of anoikis resistance phenotype of gastric cancer cells, and oxidative stress might be a therapeutic strategy for the inhibition of RhoA in cancer cells.

From dissection of disease pathogenesis to elucidation of mechanisms of targeted therapies: leukemia research in the genomic era

Leukemia is a group of heterozygous diseases of hematopoietic stem/progenitor cells that involves dynamic change in the genome. Dissection of genetic abnormalities critical to leukemia initiation provides insights into the elusive leukemogenesis, identifies distinct subsets of leukemia and predicts prognosis individually, and can also provide rational therapeutic targets for curative approaches. The past three decades have seen tremendous advances in the analysis of genotype-phenotype connection of leukemia, and in the identification of molecular biomarkers for leukemia subtypes. Intriguingly, differentiation therapy, targeted therapy and chemotherapy have turned several subtypes of leukemia from highly fatal to highly curable. The use of all-trans retinoic acid and arsenic trioxide, which trigger degradation of PML-RARalpha, the causative fusion protein generated by t (15;17) translocation in acute promyelocytic leukemia (APL), has led to a dramatic improvement of APL clinical outcome. Imatinib mesylate/ Gleevec/STI571, which inhibits the tyrosine kinase activity of BCR-ABL oncoprotein, has now become the new gold standard for the treatment of chronic myeloid leukemia. Optimal use of chemotherapeutic agents together with a stringent application of prognostic factors for risk-directed therapy in clinical trials has resulted in a steady improvement in the treatment outcome of acute lymphoblastic leukemia. Hence, the pace of progress extrapolates to a prediction of leukemia control in the twenty-first century.

Treatment of acute promyelocytic leukaemia with all-trans retinoic acid and arsenic trioxide: a paradigm of synergistic molecular targeting therapy

To turn a disease from highly fatal to highly curable is extremely difficult, especially when the disease is a type of cancer. However, we can gain some insight into how this can be done by looking back over the 50-year history of taming acute promyelocytic leukaemia (APL). APL is the M3 type of acute myeloid leukaemia characterized by an accumulation of abnormal promyelocytes in bone marrow, a severe bleeding tendency and the presence of the chromosomal translocation t(15;17) or variants. APL was considered the most fatal type of acute leukaemia five decades ago and the treatment of APL was a nightmare for physicians. Great efforts have been made by scientists worldwide to conquer this disease. The first use of chemotherapy (CT) was unsuccessful due to lack of supportive care and cytotoxic-agent-related exacerbated coagulopathy. The first breakthrough came from the use of anthracyclines which improved the complete remission (CR) rate, though the 5-year overall survival could only be attained in a small proportion of patients. A rational and intriguing hypothesis, to induce differentiation of APL cells rather than killing them, was raised in the 1970s. Laudably, the use of all-trans retinoic acid (ATRA) in treating APL resulted in terminal differentiation of APL cells and a 90-95% CR rate of patients, turning differentiation therapy in cancer treatment from hypothesis to practice. The combination of ATRA with CT further improved the 5-year overall survival. When arsenic trioxide (ATO) was used to treat relapsed APL not only the patients but also the ancient drug were revived. ATO exerts dose-dependent dual effects on APL cells: at low concentration, ATO induces partial differentiation, while at relatively high concentration, it triggers apoptosis. Of note, both ATRA and ATO trigger catabolism of the PML-RARalpha fusion protein which is the key player in APL leukaemogenesis generated from t(15;17), targeting the RARalpha (retinoic acid receptor alpha) or promyelocytic leukaemia (PML) moieties, respectively. Hence, in treating APL both ATRA and ATO represent paradigms for molecularly targeted therapy. At molecular level, ATRA and ATO synergistically modulate multiple downstream pathways/cascades. Strikingly, a clearance of PML-RARalpha transcript in an earlier and more thorough manner, and a higher quality remission and survival in newly diagnosed APL are achieved when ATRA is combined with ATO, as compared to either monotherapy, making APL a curable disease. Thus, the story of APL can serve as a model for the development of curative approaches for disease; it suggests that molecularly synergistic targeted therapies are powerful tools in cancer, and dissection of disease pathogenesis or anatomy of the cancer genome is critical in developing molecular target-based therapies.

Induction of human promyelocytic leukemia HL-60 cell differentiation into monocytes by arsenic sulphide: Involvement of serine/threonine protein phosphatases

The clinical efficacy of arsenic sulfide (As(4)S(4)), also known as realgar, in the treatment of leukemia in China is prompting people to explore the underlying mechanism. We examined the realgar-induced differentiation in human promyelocytic leukemia cell line HL-60. Cells exhibited proliferation inhibition when treated with 0.10-1.5 microM of realgar, and underwent monocytic differentiation as indicated by morphological changes, NBT reduction assay, and cytofluorometric analyses of the cell surface antigens, CD11b and CD14. Accompanying the differentiation, the activity of serine/threonine protein phosphatase type 1 (PP1) and type 2A (PP2A) were enhanced, whereas the activity of PP2B remained virtually the same compared to the control. When cells were treated with realgar in the presence of an inhibitor of PP1 and 2A or an inhibitor of PP2B, the differentiation of the cells was partially suppressed as revealed by NBT reduction assay and the expression of CD14. Our data demonstrate that realgar induces monocytic differentiation in HL-60 cells and that some serine/threonine protein phosphatases may be involved in the process.

Alteration of subcellular redox equilibrium and the consequent oxidative modification of nuclear factor kappaB are critical for anticancer cytotoxicity by emodin, a reactive oxygen species-producing agent

We previously found that emodin produced reactive oxygen species (ROS) intracellularly. In various tumor cells at low doses it enhances the cytotoxicity of As(2)O(3), and at higher doses it renders cytotoxicity independently in vitro and in vivo. The effects involve redox-mediated inhibition of NF-kappaB activation. In this study, we focus on the mechanisms by which emodin inhibits NF-kappaB activation. Results in HeLa cells demonstrated that emodin at high doses or in combination with As(2)O(3), via generation of ROS especially in the nucleus, altered subcellular redox equilibrium and thus oxidized the redox-sensitive site on NF-kappaB and prevented its binding to the target DNA. In vivo study showed that tumors exposed to the arsenic/emodin cotreatment had dramatically smaller sizes and weaker antioxidant capacity, compared with arsenic alone. NF-kappaB binding and transactivation were inhibited in these tumors. These data help in the understanding of the mechanisms by which manipulation of cellular redox and NF-kappaB activation may enhance chemotherapy.

Tissue factor as an effector of angiogenesis and tumor progression in hematological malignancies

In the last few years, it has become clear that the processes of tumor angiogenesis, metastasis and invasiveness are highly dependent on components of the blood coagulation cascade. One of the key proteins in coagulation is tissue factor (TF). In addition, TF is also known as a mediator of intracellular signaling events that can alter gene expression patterns and cell behavior. TF significantly participates in tumor-associated angiogenesis and its expression levels have been correlated with the metastatic potential of many types of hematological malignancies. Signaling pathways initiated by both, tissue factor-activated factor VII (TF-FVIIa) protease activation of protein-activated receptors (PARs), and phosphorylation of the TF-cytoplasmic domain, appear to regulate these tumoral functions. Advances in antiangiogenic therapies and preclinical studies with TF-targeted therapeutics are hopeful in the control of tumor growth and metastasis, but continued studies on the regulation of TF are still needed. In the last few years, the use of approaches of functional genomics and proteomics has allowed the discovery of new proteins involved in the origin of the neoplasia and their participation in the development of the disease. This review attempts to establish a cellular and molecular causal link between cancer coagulopathy, angiogenesis and tumor progression in hematological malignancies.

TRAIL sensitisation by arsenic trioxide is caspase-8 dependent and involves modulation of death receptor components and Akt

The majority of leukaemic cells are resistant to apoptosis induced by tumour necrosis factor-related apoptosis-inducing ligand (TRAIL). Here, we show that sublethal concentrations of arsenic trioxide (ATO) specifically enhanced TRAIL-induced apoptosis in leukaemic but not in other tumour cell lines. The combination of ATO and TRAIL synergistically enhanced cleavage of caspase-8, which was blocked by the caspase inhibitor IETD.fmk as well as in cells deficient for caspase-8, suggesting a requirement for the death-inducing signalling complex. Arsenic trioxide led to increased cell surface expression of DR5 (death receptor 5), inhibition of the serine/threonine kinase Akt and downregulation of the short isoform of FLIP (FLICE-inhibitory protein, FLIP_S). Inhibition of the phosphatidylinositol 3 kinase (PI3K) was equally efficient in sensitising leukaemic cells to TRAIL with similar effects on DR5 and FLIP_S expression, suggesting that ATO may in part act through inhibition of the PI3K/Akt signalling pathway. These results indicate that the enhancement in TRAIL-mediated apoptosis induced by ATO is due to alteration in the levels of multiple components and regulators of the death receptor-mediated pathway. These findings offer a promising and novel strategy involving a combination of TRAIL and ATO, or more specific Akt inhibitors in the treatment of various haematopoietic malignancies.

The effect of steroid on myeloid leukemic cells: The potential of short-course high-dose methylprednisolone treatment in inducing differentiation, apoptosis and in stimulating myelopoiesis

Several in vitro studies have shown that dexamethasone (Dex) and prednisolone can induce differentiation of some mouse and human myeloid leukemic cells to macrophages and granulocytes. Based on in vitro experiments, we have shown that short-course (3-7 days) high-dose methylprednisolone (HDMP) (20-30 mg/kg/day) treatment can induce differentiation of myeloid leukemic cells in vivo in children with different subtypes of acute myeloblastic leukemia (AML) (AML-M1, -M2, -M3, -M4, -M7). We have also shown that induction of apoptosis of myeloid leukemic cells with or without differentiation is possible by short-course HDMP treatment. In addition, short-course HDMP treatment has been shown to be effective in accelerating leukocyte recovery, possibly stimulating normal CD34-positive hematopoietic progenitor cells. Addition of HDMP to mild cytotoxic chemotherapy (low-dose cytosine arabinoside (LD-Ara-c), weekly mitoxantrone and Ara-c or 6-thioguanine) increased the remission rate (87-89%) and improved the outcome of AML children. We believe that the results of our 17-year clinical experience will provide important benefits to AML patients.

Gene expression alteration during redox-dependent enhancement of arsenic cytotoxicity by emodin in HeLa cells

Emodin (1,3,8-trihydroxy-6-methylanthraquinone) could enhance the sensitivity of tumor cells to arsenic trioxide (As2O3)-induced apoptosis via generation of ROS, but the molecular mechanism has not been elucidated. Here, we carried out cDNA microarray-based global transcription profiling of HeLa cells in response to As2O3/emodin cotreatment, comparing with As2O3-only treatment. The results showed that the expression of a number of genes was substantially altered at two time points. These genes are involved in different aspects of cell function. In addition to redox regulation and apoptosis, ROS affect genes encoding proteins associated with cell signaling, organelle functions, cell cycle, cytoskeleton, etc. These data suggest that based on the cytotoxicity of As2O3, emodin mobilize every genomic resource through which the As2O3-induced apoptosis is facilitated.

All-trans retinoic acid-induced downregulation of annexin II expression in myeloid leukaemia cell lines is not confined to acute promyelocytic leukaemia

Most acute promyelocytic leukaemia (APL) patients suffer from disordered haemostasis. APL can be treated successfully in most instances by all-trans retinoic acid (ATRA) therapy, which induces endpoint maturation of the leukaemic promyelocytes with the characteristic t(15;17). Annexin II (AnII), a profibrinolytic protein, has been implicated in the bleeding manifestation seen in APL. Our group has shown previously that high levels of AnII are expressed on other acute myeloid leukaemia subtypes that are sometimes associated with disordered haemostasis, albeit less frequently than APL. This study examined the effects of ATRA on AnII expression and cell differentiation, on myeloid leukaemia cell lines to determine whether a regulatory influence on AnII may contribute to the return of haemostatic stability in APL following treatment. The results confirmed that AnII expression in the APL cell line (NB4) was significantly downregulated in response to ATRA (P < 0.01), with associated morphological and immunophenotypical evidence of myeloid differentiation. ATRA also downregulated AnII expression on other myeloid cell lines, albeit to a lesser extent than observed on NB4 cells. The results provide evidence that ATRA may resolve the hyperfibrinolysis in APL by downregulation of AnII expression.

Arsenic trioxide: an anti cancer missile with multiple warheads

The proven efficacy of ATO in the treatment of APL and the emerging importance of ATO in other diseases prompted extensive studies of the mechanisms of action of ATO in APL and in other types of cancers. In this review we will focus on downstream events in ATO-induced intrinsic and extrinsic apoptotic pathways with an emphasis on the role of pro-apoptotic and anti-apoptotic proteins and the role of p53 in ATO-induced apoptosis including its effect on cell cycle, its anti-mitotic effect and the role of apoptosis inducing factors (AIF) in ATO-induced apoptosis, chromatin condensation and nuclear fragmentation in myeloma cells as a model.

Synergistic effect of all-trans-retinoic acid and arsenic trioxide on growth inhibition and apoptosis in human hepatoma, breast cancer, and lung cancer cells in vitro

AIM: To investigate the effect of all-trans-retinoic acid (ATRA) on arsenic trioxide (As₂O₃)-induced apoptosis of human hepatoma, breast cancer, and lung cancer cells in an attempt to find a better combination therapy for solid tumors.

METHODS: Human hepatoma cell lines HepG2, Hep3B, human breast cancer cell line MCF-7, and human lung adenocarcinoma cell line AGZY-83-a were treated with As₂O₃ together with ATRA. Cell survival fraction was determined by MTT assay, cell viability and apoptosis were measured by annexin V-fluorescein isothiocyanate (FITC) and PI staining, and intracellular glutathione (GSH) and glutathione-S-transferase (GST) activities were determined using commercial kits.

RESULTS: Cytotoxicity of ATRA was low. ATRA (0.1, 1, and 10 μmol/L) could synergistically potentiate As₂O₃ to exert a dose-dependent inhibition of growth and to induce apoptosis in each of the cell lines. HepG2 and Hep3B with low intracellular GSH or GST activities were remarkably sensitive to As₂O₃ or As₂O₃+ATRA, while AGZY-83-a with higher GSH or GST activities was less sensitive to As₂O₃ or As₂O₃+ATRA. Treatment with 2 μmol/L As₂O₃ for 72 h significantly decreased intracellular GSH and GST levels in each of the cell lines, and 1 μmol/L ATRA alone reduced minimal intracellular GSH and GST levels. ATRA potentiated the effect of As₂O₃ on intracellular GSH levels, but intracellular GST levels were not significantly affected by the combination of As₂O₃ and ATRA for 72 h as compared to As₂O₃ alone.

CONCLUSION: ATRA can strongly potentiate As 2O3-induced growth-inhibition and apoptosis in each of the cell lines, and two drugs can produce a significant synergic effect. The sensitivity to As2O3 or As2O3+ATRA is inversely proportional to intracellular GSH or GST levels in each of the cell lines. The GSH redox system may be the possible mechanism by which ATRA synergistically potentiates As2O3 to exert a dose-dependent inhibition of growth and to induce apoptosis.

Up-regulation of telomere-binding TRF1, TRF2 related to reactive oxygen species induced by As(2)O(3) in MGC-803 cells

In this work, our study focused on As(2)O(3) action in view point of telomere. Results showed that treatment of human gastric cancer MGC-803 cells with arsenic trioxide could cause up-regulation of telomeric repeat binding factor TRF1 and TRF2 mRNA and protein levels, and induced G2/M phase arrest and cell apoptosis. At the same time, telomere length shortening and telomerase inhibitory were not obvious. Flow cytometry measurements indicated that the increase of TRF1 and TRF2 proteins is related to oxidative stress by arsenic trioxide. Results also indicate that after arsenic trioxide treatment, p53 protein levels increased significantly and also could bind directly at the telomere t-loop junction. These findings demonstrate arsenic trioxide-induced cell cycle arrest and apoptosis might involve a novel pathway related to TRF1, TRF2 protein.

Delayed recovery of normal hematopoiesis in arsenic trioxide treatment of acute promyelocytic leukemia: a comparison to all-trans retinoic acid treatment

OBJECTIVE

To examine laboratory data including total blood cell count, leukocyte morphology and coagulation parameters during treatment for acute promyelocytic leukemia (APL) at a single institute, and compare the precise differences between all-trans retinoic acid (ATRA) and arsenic trioxide (As2O3) treatment.

PATIENTS AND METHODS

Sixteen patients with APL who were treated with ATRA or As2O3 alone and achieved complete remission (CR) were analyzed. ATRA 45 mg/m2/day was given orally until CR. As2O3 0.15 mg/kg/day was given intravenously until leukemic blasts and promyelocytes were eliminated from the bone marrow.

RESULTS

All 7 patients in the ATRA-treated group were primary cases and all 9 patients in the As2O3-treated group were relapsed cases after the achievement of CR with the ATRA. There was no difference in the data before treatment between these two groups. The duration of leukocytopenia and neutropenia during As2O3 treatment was significantly longer than those of ATRA treatment. The nadir of leukocyte and neutrophil counts was observed later in the As2O3-treated group. Terminal neutrophil differentiation was observed more obviously in the ATRA-treated group. The red blood cell count and hemoglobin concentration decreased significantly at the end of As2O3 treatment and were lower than those of ATRA treatment. Platelets recovered earlier in the ATRA-treated group. Coagulation parameters were not significantly changed between the two groups.

CONCLUSION

In comparison with ATRA treatment, the recovery of several components in the peripheral blood cells was delayed in As2O3 treatment. Therefore we should pay more and longer attention in As2O3 treatment.

Primary myeloid sarcoma of the testicle with t(15;17)

The first case of acute promyelocytic leukemia presenting as a solitary testicular mass (myeloid sarcoma) that relapsed in the contralateral testicle is described. The neoplastic cells strongly expressed chloroacetate esterase, myeloperoxidase, CD33, CD43, and weakly, CD117. The presence of many azurophil granules and Auer rods was detected by electron microscopy. Translocation (15;17)(q22;q21.1) was revealed by cytogenetics and was verified by fluorescence in situ hybridization. Contralateral testicle is a favorite site for recurrence in a subset of testicular myeloid sarcomas. Subclassification of all cases of myeloid sarcoma ought to be attempted.

19-Nor-1,25(OH)2D2(a Novel, Noncalcemic Vitamin D Analogue), Combined with Arsenic Trioxide, Has Potent Antitumor Activity against Myeloid Leukemia

Recently, we reported that a novel, noncalcemic vitamin D analogue (19-nor-1,25(OH)2D2; paricalcitol) had anticancer activity. In this study, we explored if paricalcitol enhanced anticancer effects of other clinically useful drugs in vitro against a large variety of cancer cells. Paricalcitol, when combined with As2O3, showed a markedly enhanced antiproliferative effect against acute myeloid leukemia (AML) cells. This combination induced monocytic differentiation of NB-4 acute promyelocytic leukemia (APL) cells and HL-60 AML cells and caused both to undergo apoptosis associated with down-regulation of Bcl-2 and Bcl-x(L). Paricalcitol induced monocytic differentiation of U937 AML cells, which was partially blocked by inducing expression of APL-related PML-retinoic acid receptor alpha (RARalpha) chimeric protein in the U937 cells containing a Zn2+-inducible expression vector coding for this fusion protein (PR9 cells). Exposure to As2O3 decreased levels of PML-RARalpha in PR9 cells, and the combination of paricalcitol and As2O3 enhanced their monocytic differentiation in parallel with the As2O3-mediated decrease of PML-RARalpha. Furthermore, As2O3 increased the transcriptional activity of paricalcitol probably by increasing intracellular levels of paricalcitol by decreasing the function of the mitochondrial enzyme 25-hydroxyvitamin D3-24-hydroxylase, which functions to metabolize the active vitamin D in cells. In summary, the combination of paricalcitol and As2O3 potently decreased growth and induced differentiation and apoptosis of AML cells. This probably occurred by As2O3 decreasing levels of both the repressive PML-RARalpha fusion protein and the vitamin D metabolizing protein, 25-hydroxyvitamin D3-24-hydroxylase, resulting in increased activity of paricalcitol. The combination of both of these Food and Drug Administration-approved drugs should be considered for treatment of all-trans retinoic acid-resistant APL patients as well as those with other types of AML.

Triterpenoid CDDO-Im downregulates PML/RARα expression in acute promyelocytic leukemia cells

The triterpenoid 2-cyano-3,12-dioxooleana-1,9-dien-28-oic acid (CDDO) induces differentiation and apoptosis of diverse human tumor cells. In the present study, we examined the effects of the CDDO imidazolide imide (CDDO-Im) on the NB4 acute promyelocytic leukemia (APL) cell line and primary APL cells. The results show that CDDO-Im selectively downregulates expression of the PML/retinoic receptor alpha fusion protein by a caspase-dependent mechanism and sensitizes APL cells to the differentiating effects of all-trans retinoic acid (ATRA). CDDO-Im treatment of APL cells was also associated with disruption of redox balance and activation of the extrinsic apoptotic pathway. In concert with these results, CDDO-Im sensitizes APL cells to arsenic trioxide (ATO)-induced apoptosis. Our findings indicate that CDDO-Im may be effective in the treatment of APL by: (i) downregulation of PML/RARalpha; (ii) enhancement of ATRA-induced differentiation; and (iii) sensitization of ATO-induced APL cell death.

Arsenite Delays Progression through Each Cell Cycle Phase and Induces Apoptosis following G2/M Arrest in U937 Myeloid Leukemia Cells

Arsenic is a well known toxicant and carcinogen that is also effective as a chemotherapeutic in the treatment of acute promyelocytic leukemia. Although its effects on humans are well documented, arsenic's mechanism of action is not well understood. Its ability to act as a carcinogen and as a chemotherapeutic seems paradoxical. However, cancer cell transformation and cancer cell destruction can both occur through perturbations of the cell cycle machinery, making cell cycle function a likely target of arsenic action. Arsenic has previously been shown to inhibit cancer cell cycle progression, but the targeted cell cycle phase has been debated. This study was designed to identify the cell cycle phase at which U937 cells are most sensitive to arsenite-induced growth inhibition. Centrifugal elutriation was used to divide asynchronous cell cultures into specific cell cycle phase-enriched fractions. These fractions were monitored for cell cycle phase progression in the presence and absence of sodium arsenite. We found an overall reduction in cell cycle progression rather than induction of arrest at one specific checkpoint. G(2)/M is the phase most sensitive to arsenite-induced apoptosis. However, arsenite profoundly affects U937 cell growth by increasing the length of time it takes cells to transit each phase of the cell cycle. Future study of cell cycle inhibition by arsenic should consider that the effect may not be mediated by the major cell cycle checkpoints. Arsenic's ability to inhibit growth in any cell cycle phase may increase its value as a chemotherapeutic used together with other, more phase-selective agents, such as camptothecin.

Treatment of acute promyelocytic leukemia in the very elderly: case report and review of the literature

Acute promyelocytic leukemia (APL) is the most curable subtype of AML yet it is not known to what extent newer therapies will succeed in the very elderly. Conventional chemotherapeutic induction regimens are usually too toxic for older patients, however, all trans-retinoic acid (ATRA) and arsenic trioxide (ATO) may be useful therapeutic options if used judiciously. This case series describes three octogenarians with APL all treated with ATRA and achieved complete remissions. The last patient received ATO at the time of first relapse and achieved a second remission. To our knowledge, this is the first report of successful use of ATO for induction in an octogenarian with APL.

Arsenic trioxide causes redistribution of cell cycle, caspase activation, and GADD expression in human colonic, breast, and pancreatic cancer cells

Arsenic trioxide is valuable for treatment of promyelocytic leukemia, but less attention has been paid to its therapeutic potential for other cancers. In this study, the effects of arsenic trioxide were tested in human pancreatic (AsPC-1), colonic (HT-29), and breast (MCF-7) cancer cells. In all three cancer cell lines, arsenic trioxide inhibited proliferation in a concentration and time-dependent manner, as measured by 3H-methyl thymidine incorporation and cell counting. Coincident with inhibition of growth, arsenic trioxide induced marked morphologic changes, including reduced cytoplasmic volume, membrane blebbing, and nuclear condensation consistent with apoptosis. Propidium iodide DNA staining at 24 hours revealed cell cycle arrest in the G0/G1 phase and an increase in the S phase, while at 72 hr there was G2/M phase arrest with a marked increase in the sub-G0/G1, apoptotic cell population. The DNA fragmentation induced by arsenic trioxide was confirmed by the terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick-end labeling (TUNEL) assay in all cell lines. Western blot analysis revealed activation of caspase -3, -7, and -9 by arsenic trioxide. Caspase-3 activity was confirmed by demonstrating cleavage of its downstream target, poly ADP-ribose polymerase (PARP). Expression of the antiapoptosis protein, Bcl-2, was time-dependently decreased. In contrast, arsenic trioxide markedly enhanced the expression of the p21 protein, GADD45 and GADD153, in a time-dependent manner. These findings suggest that arsenic trioxide has potential as a therapeutic agent for these cancers.

Sodium selenite induces apoptosis in acute promyelocytic leukemia-derived NB4 cells by a caspase-3-dependent mechanism and a redox pathway different from that of arsenic trioxide

Two relatively recent discoveries stand behind our current effort to investigate the effects of the chemopreventive agent, selenium, on the proliferation and survival of NB4 cells. The first is that certain selenium compounds such as sodium selenite have pro-oxidant ability to catalyze the oxidation of thiols and simultaneously generate superoxide. The second lies in the exquisite susceptibility of NB4 cells to arsenic trioxide-induced, reactive oxygen species (ROS)-mediated apoptosis due to less efficiency of the cellular defense system. In this study, we demonstrated that sodium selenite could induce apoptosis in NB4 cells via the classic mitochondrial pathway involving caspase-3 activation and Bcl-2 cleavage. An increase in the basal cellular glutathione (GSH) content rendered NB4 cells resistant to arsenic trioxide, but could sensitize NB4 cells to sodium selenite. Moreover, combined treatment of NB4 cells with all- trans retinoic acid (ATRA) at low concentration and sodium selenite exhibited a synergistic effect on apoptosis induction. Together, our results suggest that selenite is a promising candidate for treatment of acute promyelocytic leukemia (APL) and the mechanism underlying its anticancer effects warrants further investigation.