Studies on the clinical efficacy and pharmacokinetics of low-dose arsenic trioxide in the treatment of relapsed acute promyelocytic leukemia: a comparison with conventional dosage

Arsenic-induced neurotoxicity in patients with acute promyelocytic leukaemia

Arsenic trioxide is an essential component of therapy for acute promyelocytic leukaemia (APL) and is currently dosed on actual body weight with no upper limit. Arsenic-induced neurotoxicity is a well-recognised complication; however, there is uncertainty about its relationship to arsenic dose and obesity. We conducted a large multicentre retrospective study of 487 patients with APL treated with arsenic-based therapy across 23 sites in Australia from 2008 to 2023. The primary outcome was incidence of neurotoxicity, and secondary outcomes included relationship of neurotoxicity to obesity and cumulative arsenic dose. Any-grade neurotoxicity occurred in 113 (23%) patients, predominantly peripheral neuropathy (91%). Most events were grade 1-2 severity (85%), with grade 3 events in 12% and grade 4-5 in 3%. The incidence of neurotoxicity increased with BMI (non-obese: 16%, obesity class I: 25%, obesity class II-III: 41%; p < 0.001). On univariable analysis, obesity class I (OR 1.81, p = 0.036), obesity class II-III (OR 3.93, p < 0.001), weight >100 kg (OR 2.72, p < 0.001), daily arsenic trioxide dose >15 mg (OR 5.05, p < 0.001) and cumulative induction dose >500 mg (OR 3.95, p < 0.001) were all significantly associated with neurotoxicity. Obesity class II-III and induction dose >500 mg remained significant on multivariable analysis. Our study highlights the strong association between BMI, arsenic trioxide dose and neurotoxicity. Pre-emptive dose reductions should be considered for obese patients receiving high doses of arsenic.

Combinatorial Effect of Arsenic and Herbal Compounds in Telomerase-Mediated Apoptosis Induction in Liver Cancer

Tumour illness and its resistance against existing anticancer therapies pose a serious health concern globally despite the progressive advancement of therapeutic options. The prevailing treatment of HCC using numerous antitumor agents has inflated long-lived complete remissions, but a percentage of individuals still die due to disease recurrence, indicating a need for further exploration of possible anti-tumour regimes. We aim to boost the effectiveness of the HCC treatment by conducting current investigations evaluating the effect of arsenic trioxide (ATO) with different herbal compounds like quercetin and aloe-emodin against liver tumour via inhibition of telomerase, a pro-cancer enzyme. The anticancer activity of ATO with herbal compounds was investigated in human control liver cell line (Wrl-68) and cancer liver cell line (HepG2) at different time intervals. Viability and cytotoxicity in response to combinatorial drugs were assessed in vitro by trypan blue dye exclusion assay and MTT and WST assay. Apoptosis was analysed by annexin V/PI assay, and the expression of telomerase and apoptosis-regulating proteins was evaluated by immunoblotting and qRT-PCR. Arsenic trioxide in combination with quercetin and aloe-emodin reduced cell viability in cancerous cells compared to normal cells by inducing apoptosis, downregulating telomerase and Bcl-2 (anti-apoptotic protein) and upregulating the expression of Bax (pro-apoptotic protein). ATO exhibited significant anticancer effects due to the synergistic effects of quercetin and aloe-emodin in liver tumour cells. The current study data collectively suggest that a successful inhibition of cancer growth by the combination of ATO and tested herbal medicines against liver tumour growth is via the inhibition of telomerase activity.

Predictors of early death and clinical features in newly diagnosed patients with low-intermediate risk acute promyelocytic leukemia

Background

Although most acute promyelocytic leukemia(APL) with low-intermediate risk could survive the induction treatment, early death still a big problem to have effects on overall survival in real world.This study aimed to analyze the clinical characteristics and possible predictors of early death in newly diagnosed patients with low-intermediate-risk acute promyelocytic leukemia.

Methods

Sixty patients with newly diagnosed low/intermediate-risk APL admitted to Mianyang Central Hospital from January 2013 to December 2021 were retrospectively analyzed.

Results

Sixty patients with a median age of 46 years (range, 17-75 years) were included. Fourteen patients (23.3%) were in low-risk group, and 46 patients (76.7%) were in intermediate-risk group. Fourteen patients (23.3%) died during induction treatment. Five patients died of hemorrhage, 5 of severe infection and 4 of differentiation syndrome. Multivariate analysis showed that HGB <65g/L at diagnosis (OR=38.474, 95%CI: 2.648~558.923, P=0.008) during induction treatment was an independent risk factors for early death in low- intermediate risk APL patients. In survival group, all patients achieved complete remission, the time to achieve remission was 25.87 ± 5.02 days, the average ATO dosage was 0.16 ± 0.03 mg/kg/day. In univariate analysis, there was no statistically significant difference in time span for remission when ATO dosage was in the 0.11~0.16mg/kg/day range. Compared with patients with low-risk APL, those with intermediate-risk APL had higher white blood cell counts (at diagnosis, day 3, day 5 and peak), higher level of lactate dehydrogenase, higher percentage of bone marrow promyelocytes, more platelet transfusions during treatment, and more early deaths (P<0.05). The overall survival of intermediate-risk APL patients seemed worse than those with low-risk APL (χ=5.033, P =0.025).

Conclusions

In patients with low-intermediate risk APL, HGB <65g/L at diagnosis was an independent risk factors for early death. Remission could still be achieved at low-dose ATO without affecting the required time for low-intermediate risk APL patients. Differences in clinical characteristics were found between low-risk and intermediate-risk APL. The intermediate-risk group had higher early mortality risk than the low-risk group.

Down-regulation of hepatic cytochromes P450 1A1 and 1A2 by arsenic trioxide (ATO) in vivo and in vitro: A role of heme oxygenase 1

Arsenic trioxide (ATO) has evolved from an environmental threat to a successful therapy for acute promyelocytic leukemia (APL) and probably for solid tumors in the future. However, its efficacy comes at a cost of multi-organ toxicity whose mechanism remains unresolved. Arsenicals have been reported to modulate cytochrome P450 1A (CYP1A) enzymes, thus modifying activation/detoxification of drugs/procarcinogens. Therefore, this study aimed to investigate the possible effects of ATO on CYP1A1 and CYP1A2, in absence and presence of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) using in vivo and in vitro models. For this purpose, C57BL/6 mice were intraperitoneally injected with 8 mg/kg ATO with or without 15 μg/kg TCDD for 6 and 24 h. Furthermore, HepG2 cells were treated with ATO (1, 5, and 10 μM) with or without 1 nM TCDD for 6 and 24 h. ATO significantly inhibited TCDD-mediated induction of CYP1A1/1A2 mRNA, protein, and activity in both models. ATO differentially modulated CYP1A1/1A2 basal levels in vivo. We also demonstrated that ATO downregulates CYP1A through inhibiting the transcriptional activation of its regulatory element at both basal and inducible levels. Additionally, ATO significantly induced mRNA and protein of heme oxygenase 1 (HMOX1) in vivo and in vitro. In HepG2 cells, inhibition of HMOX1 by tin (IV) mesoporphyrin (IX) (SnMP) resulted in a partial restoration of the TCDD-mediated induction of CYP1A1 activity that was inhibited by ATO co-exposure. Our findings show that ATO alters both constitutive and inducible CYP1A1/1A2 expressions through transcriptional and HMOX1-mediated post-translational mechanisms. This implies the possible involvement of ATO in clearance-related consequences for the substrates of these enzymes such as drug-drug interactions or suboptimal toxicant elimination.

Vitamin D Derivatives in Acute Myeloid Leukemia: The Matter of Selecting the Right Targets

Acute myeloid leukemia (AML) is an aggressive and often fatal hematopoietic malignancy. A very attractive way to treat myeloid leukemia, called “differentiation therapy”, was proposed when in vitro studies showed that some compounds are capable of inducing differentiation of AML cell lines. One of the differentiation-inducing agents, all-trans-retinoic acid (ATRA), which can induce granulocytic differentiation in AML cell lines, has been introduced into clinics to treat patients with acute promyelocytic leukemia (APL) in which a PML-RARA fusion protein is generated by a chromosomal translocation. ATRA has greatly improved the treatment of APL. Since 1,25-dihydroxyvitamin D (1,25D) is capable of inducing monocytic differentiation of leukemic cells, the idea of treating other AMLs with vitamin D analogs was widely accepted. However, early clinical trials in which cancer patients were treated either with 1,25D or with analogs did not lead to conclusive results. Recent results have shown that AML types with certain mutations, such as isocitrate dehydrogenase (IDH) mutations, may be the right targets for differentiation therapy using 1,25D, due to upregulation of vitamin D receptor (VDR) pathway.

Arsenic trioxide inhibits the functions of lung fibroblasts derived from patients with idiopathic pulmonary fibrosis

Idiopathic pulmonary fibrosis (IPF) is a chronic and fatal interstitial lung disease. Currently, no treatment can block or reverse the development of lung fibrosis in patients suffering from IPF. Recent studies indicate that arsenic trioxide (ATO), a safe, effective anti-cancer pro-oxidant drug, prevents the differentiation of normal human lung fibroblasts (NHLFs) in vitro and reduces experimental pulmonary fibrosis in vivo. In this context, we investigated the anti-fibrotic effects of ATO on the main fibrosis functions of human lung fibroblasts (HLFs) isolated from patients with IPF. IPF and non-IPF (control) HLFs were incubated with 0.01-1 μM ATO and stimulated with pro-fibrotic factors (PDGF-BB or TGF-β1). We measured their rates of proliferation, migration and differentiation and the cell stress response triggered by ATO. ATO did not affect cell viability but strongly inhibited the proliferation and migration of PDGF-BB-stimulated IPF and control HLFs. ATO also prevented myofibroblastic differentiation, as assessed by the expression of α-smooth muscle actin (α-SMA) and collagen-1, and the phosphorylation of SMAD2/3 in TGF-β1-stimulated HLFs. These antifibrotic effects were associated with increased expression of the transcription factor NRF2 and its target genes NQO1 and HMOX1. Genetic silencing of NRF2 inhibited the ATO-induced cell stress response but did not prevent the ATO-dependent inhibition of α-SMA expression in TGF-β1-stimulated HLFs. The results demonstrate that ATO, at concentrations similar to exposure in blood plasma of ATO-treated cancer patients, counteracted pro-fibrotic activities of HLFs from IPF patients. We propose to consider ATO for clinical exploration to define the therapeutic potential in patients with IPF.

Arsenic trioxide dose capping to decrease toxicity in the treatment of acute promyelocytic leukemia

Arsenic trioxide (ATO) and all-trans retinoic acid (ATRA) combination therapy yields high complete remission and disease-free survival rates in acute promyelocytic leukemia (APL). ATO is dosed on actual body weight and high ATO doses in overweight patients may contribute to increased toxicity. We performed a retrospective, two-center study comparing toxicities in patients who received the Lo-Coco et al ATRA/ATO regimen with capped ATO, ≤10 mg/dose, and non-capped ATO, >10 mg/dose. A total of 44 patients were included; 15 received doses ≤10 mg and 29 received >10 mg. During induction, there was no difference in the incidence of grade ≥3 hepatotoxicity, grade ≥3 QTc prolongation, neurotoxicity, and cardiac toxicity between groups. In consolidation, patients receiving >10 mg/dose experienced a greater incidence of neurotoxicity (66.7% vs 22.2%; p = 0.046). Capping doses saved $24634.37/patient and reduced waste of partially-used vials. At a median follow-up of 27 months, no disease relapses occurred in either group. This represents an opportunity to improve the safety profile of this highly effective regimen.

Acute promyelocytic leukemia drug - arsenic trioxide in the presence of eugenol shows differential action on leukemia cells (HL-60) and cardiomyocytes (H9c2) - inference from NMR study

The increased concern of cardiovascular dysfunction by cancer therapeutics has led to more effective treatment strategies. Arsenic trioxide (As₂O₃) is a potential chemotherapeutic agent for acute promyelocytic leukemia (APL), but the effectiveness is affected by potential cardiotoxicity. Researchers have been trying to find out novel modalities to manage the adverse effects of As₂O₃. In our study, the antioxidant molecule eugenol showed protective action against the destructive impact of As₂O₃ on cardiomyocytes (H9c2) without compromising the anti-cancer property As₂O₃ on leukemia cells (HL-60). We have studied the interaction between arsenic and eugenol in physiological and acidic pH to understand the molecular mechanism of differential action of As₂O₃ in the presence of eugenol using NMR spectroscopy. The study observed that at physiological pH, arsenic and eugenol interact to form an inactive product, positively affecting H9c2 cardiomyocytes. Still, there is no such interaction in acidic pH evidenced by the useful anti-cancer property of As₂O₃. The result concludes that the antioxidant molecule eugenol is an efficient protective agent against the adverse effect of As₂O₃ on cardiomyocytes.

Resurrection of Oral Arsenic Trioxide for Treating Acute Promyelocytic Leukaemia: A Historical Account From Bedside to Bench to Bedside

Various forms of arsenic were used in China and elsewhere for over 5,000 years. Following the initial success of intravenous arsenic trioxide (i.v. As₂O₃), we revived an oral formulation of pure As₂O₃ in 1998 for the treatment of acute promyelocytic leukemia (APL). We were the first to produce a 1 mg/ml oral-As₂O₃ solution and showed that it had comparable bioavailability to i.v. As₂O₃. Moreover, we also reported that intracellular arsenic concentrations were considerably higher than the corresponding plasma values. Our oral-As₂O₃ was patented internationally and registered in Hong Kong for the treatment of APL. Safety, tolerability and clinical efficacy was confirmed in long-term follow-up studies. We have extended the use of oral-As₂O₃ to frontline induction of newly diagnosed APL. With these findings, we are moving toward an era of completely oral and chemotherapy-free management of APL.

(-)-Epigallocatechin-3-gallate encapsulated realgar nanoparticles exhibit enhanced anticancer therapeutic efficacy against acute promyelocytic leukemia

Realgar and (-)-Epigallocatechin-3-gallate (EGCG) are natural medicines that inhibit cancer cell growth, resulting in inhibition of formation and development of tumors. The anticancer effects of realgar and EGCG were greatly improved following formulation as nanoparticles. EGCG has received increased attention as a drug carrier. The aim of this study was to prepare a new nanomedicine, (EGCG-RNPs), in which encapsulated nano-realgar. EGCG-RNPs were prepared by coprecipitation and characterized by transmission electron microscopy (TEM), differential scanning calorimetry (DSC), particle size and zeta potential, X-ray diffraction, Fourier transform infrared spectroscopy (FTIR) and in vitro release. Furthermore, we evaluated the antiproliferative effects of EGCG-RNPs on HL-60 cells in vitro, antitumor effect by intratumoral injection of EGCG-RNPs into solid tumors derived from APL HL-60 cells in vivo. Possible mechanisms were evaluated using uptake and efflux experiments in HL-60 cells. The results showed that the average particle size and zeta potentials of EGCG-RNPs was 200.3 ± 1.23 nm and −46.8 ± 1.31 mV. Controlled release of EGCG-RNPs was sustained and continued up to 72 h in vitro. Compared with nano-realgar and EGCG + RNPs (EGCG and nano-realgar physical mixing), EGCG-RNPs significantly inhibited growth of HL-60 cells. In a solid tumor model, EGCG-RNPs decreased tumor volumes, with an inhibitory rate of 60.18% at a dose of 70 mg · kg⁻¹. The mechanisms of antitumor improvement may correlate with the increased uptake of realgar and prolonged the retention time of realgar in HL-60 cells due to EGCG as a carrier. EGCG-RNPs could enhance anticancer therapeutic efficacy for acute promyelocytic leukemia.

An Overview on Arsenic Trioxide-Induced Cardiotoxicity

Arsenic trioxide (ATO) is among the first-line chemotherapeutic drugs used in oncological practice. It has shown substantial efficacy in treating patients with relapsed or refractory acute promyelocytic leukaemia. The clinical use of ATO is hampered due to cardiotoxicity and hence many patients are precluded from receiving this highly effective treatment. An alternative to this would be to use any drug that can ameliorate the cardiotoxic effects and allow exploiting the full therapeutic potential of ATO, with considerable impact on cancer therapy. Generation of reactive oxygen species is involved in a wide range of human diseases, including cancer, cardiovascular, pulmonary and neurological disorders. Hence, agents with the ability to protect against these reactive species may be therapeutically useful. The present review focuses on the beneficial as well as harmful effects of arsenic and ATO, the mechanisms underlying ATO toxicity and the possible ways that can be adopted to circumvent ATO-induced toxicity.

Acute Promyelocytic Leukemia: A History over 60 Years-From the Most Malignant to the most Curable Form of Acute Leukemia

Acute promyelocytic leukemia (APL) is a distinct subtype of acute myeloid leukemia (AML) that is cytogenetically characterized by a balanced reciprocal translocation between chromosomes 15 and 17, which results in the fusion of the promyelocytic leukemia (PML) and retinoic acid receptor alpha (RARα) genes. Because patients with APL present a tendency for severe bleeding, often resulting in an early fatal course, APL was historically considered to be one of the most fatal forms of acute leukemia. However, therapeutic advances, including anthracycline- and cytarabine-based chemotherapy, have significantly improved the outcomes of APL patients. Due to the further introduction of all-trans retinoic acid (ATRA) and-more recently-the development of arsenic trioxide (ATO)-containing regimens, APL is currently the most curable form of AML in adults. Treatment with these new agents has introduced the concept of cure through targeted therapy. With the advent of revolutionary ATRA-ATO combination therapies, chemotherapy can now be safely omitted from the treatment of low-risk APL patients. In this article, we review the six-decade history of APL, from its initial characterization to the era of chemotherapy-free ATRA-ATO, a model of cancer-targeted therapy.

Treatment of Acute Promyelocytic Leukemia in Adults

The treatment of acute promyelocytic leukemia (APL) has evolved rapidly in the past two decades after the introduction of highly active drugs, including tretinoin (all- trans-retinoic acid) and arsenic trioxide. It is now possible to treat this disease without the use of traditional cytotoxic chemotherapy. Today’s clinical guidelines include multiple regimens, some of which continue to use cytotoxic chemotherapy. This leaves the practicing oncologist with multiple treatment options when faced with a new case of APL. In an effort to standardize our approach to the treatment of newly diagnosed APL, we sought to develop a set of treatment recommendations at our institution. We identified eight major controversial issues in the treatment of APL. These controversial issues include the optimal dose and schedule of both all- trans-retinoic acid and arsenic trioxide, the optimal regimen for high-risk APL, the need for intrathecal prophylaxis, the use of prophylactic corticosteroids, and the need for maintenance therapy after consolidation. We reviewed the relevant literature and used the Delphi method among the coauthors to reach consensus for recommendations on the basis of the best available data and our own clinical experience. In this clinical review, we present our consensus recommendations, the reasoning behind them, and the grading of the evidence that supports them.

Gene expression profile induced by arsenic trioxide in chronic lymphocytic leukemia cells reveals a central role for heme oxygenase-1 in apoptosis and regulation of matrix metalloproteinase-9

CLL remains an incurable disease in spite of the many new compounds being tested. Arsenic trioxide (ATO) induces apoptosis in all CLL cell types and could constitute an efficient therapy. To further explore this, we have studied the gene expression profile induced by ATO in CLL cells. ATO modulated many genes, largely involved in oxidative stress, being HMOX1 the most upregulated gene, also induced at the protein level. ATO also increased MMP-9, as we previously observed, both at the mRNA and protein level. Using specific inhibitors, qPCR analyses, and gene silencing approaches we demonstrate that upregulation of MMP-9 by ATO involved activation of the p38 MAPK/AP-1 signaling pathway. Moreover, gene silencing HMOX1 or inhibiting HMOX1 activity enhanced p38 MAPK phosphorylation and c-jun expression/activation, resulting in transcriptional upregulation of MMP-9. Overexpression of HMOX1 or enhancement of its activity, had the opposite effect. Cell viability analyses upon modulation of HMOX1 expression or activity demonstrated that HMOX1 had a pro-apoptotic role and enhanced the cytotoxic effect of ATO in CLL cells. We have therefore identified a new mechanism in which HMOX1 plays a central role in the response of CLL cells to ATO and in the regulation of the anti-apoptotic protein MMP-9. Thus, HMOX1 arises as a new therapeutic target in CLL and the combination of HMOX1 modulators with ATO may constitute an efficient therapeutic strategy in CLL.

On arsenic trioxide in the clinical treatment of acute promyelocytic leukemia

Arsenic is generally considered hypertoxic. However, it has been used in traditional Chinese medicine since ancient times, to treat serious illnesses. Recently, a single dose of arsenic trioxide (As₂O₃) has been found especially effective in treating acute promyelocytic leukemia (APL). Generally speaking, As₂O₃ is a more effective treatment of APL than other, newer medications and has less severe adverse reactions and greater safety.

RGD conjugated liposome-hollow silica hybrid nanovehicles for targeted and controlled delivery of arsenic trioxide against hepatic carcinoma

The aim of our study was to construct an Arg-Gly-Asp (RGD)-conjugated liposome-hollow silica hybrid nanovehicle for targeted delivery and controlled release of arsenic trioxide (ATO), whose anti-solid tumor effect was hampered by poor pharmacokinetics and dose-limited toxicity. Hydrophobic interactions were used to attach intact lipid membrane to the surface of chlorodimethyloctadecylsilane-modified hollow mesoporous silica nanoparticles. The prepared nanovehicles (RGD-LP-CHMSN) were characterized for uniform structure (silica core of ∼140nm in diameter and liposomal shell of ∼6nm), comparable drug loading efficiency (6.76%), desirable stability and strengthened controlled release. In vitro, RGD-LP-CHMSN showed good biocompatibility and low toxicity on HepG2, MCF-7 and LO2 cells. The targeted delivery of ATO by nanocarriers (RGD-LP-CHMSN-ATO) was demonstrated by an enhanced cellular uptake and a reduced half maximal inhibitory concentration (IC₅₀) value. In pharmacokinetic studies, the RGD-LP-CHMSN-ATO group, compared to the free ATO group, prolonged the half time (t_1/2β) by 1.7 times and increased the area under curve (AUC) by 2.4 times. In addition, in a H22 tumor-xenograft mouse model, nanovehicles improved the targeting efficiency and anticancer potential of ATO. In conclusion, the strategy of constructing a nanocarrier with targeted delivery and controlled release characteristics is prospective to enhance the antitumor effect of ATO.

RUNX3 plays an important role in As2O3‑induced apoptosis and allows cells to overcome MSC‑mediated drug resistance

The interaction between bone marrow stromal cells and leukemia cells is critical for the persistence and progression of leukemia, and this interaction may account for residual disease. However, the link between leukemia cells and their environment is still poorly understood. In our study, runt‑related transcription factor 3 (RUNX3) was identified as a novel target gene affected by As2O3 and involved in mesenchymal stem cell (MSC)‑mediated protection of leukemia cells from As2O3‑induced apoptosis. We observed induction of RUNX3 expression and the translocation of RUNX3 into the nucleus after As2O3 treatment in leukemia cells. In K562 chronic myeloid leukemia cells, downregulation of endogenous RUNX3 compromised As2O3‑induced growth inhibition, cell cycle arrest, and apoptosis. In the presence of MSC, As2O3‑induced expression of RUNX3 was reduced significantly and this reduction was modulated by CXCL12/CXCR4 signaling. Furthermore, overexpression of RUNX3 restored, at least in part, the sensitivity of leukemic cells to As2O3. We conclude that RUNX3 plays an important role in As2O3‑induced cellular responses and allows cells to overcome MSC‑mediated drug resistance. Therefore, RUNX3 is a promising target for therapeutic approaches to overcome MSC‑mediated drug resistance.

Molecular Characteristics and Clinical Significance of 12 Fusion Genes in Acute Promyelocytic Leukemia: A Systematic Review

Acute promyelocytic leukemia (APL) is characterized by the generation of the promyelocytic leukemia-retinoic acid (RA) receptor α (PML-RARα) fusion gene. PML-RARα is the central leukemia-initiating event in APL and is directly targeted by all-trans-RA (ATRA) as well as arsenic. In classic APL harboring PML-RARα transcripts, more than 90% of patients can achieve complete remission when treated with ATRA combined with arsenic trioxide chemotherapy. In the last 20 years, more than 10 variant fusion genes have been found and identified in APL patients. These variant APL cases present different clinical phenotypes and treatment outcomes. All variant APL cases show a similar breakpoint within the RARα gene, whereas its partner genes are variable. These fusion proteins have the ability to repress rather than activate retinoic targets. These chimeric proteins also possess different molecular characteristics, thereby resulting in variable sensitivities to ATRA and clinical outcomes. In this review, we comprehensively analyze various rearrangements in variant APL cases that have been reported in the literature as well as the molecular characteristics and functions of the fusion proteins derived from different RARα partner genes and their clinical implications.

pH-triggered sustained release of arsenic trioxide by polyacrylic acid capped mesoporous silica nanoparticles for solid tumor treatment in vitro and in vivo

Arsenic trioxide (As2O3, ATO), a FDA approved drug for hematologic malignancies, was proved of efficient growth inhibition of cancer cell in vitro or solid tumor in vivo. However, its effect on solid tumor in vivo was hampered by its poor pharmacokinetics and dose-limited toxicity. In this study, a polyacrylic acid capped pH-triggered mesoporous silica nanoparticles was conducted to improve the pharmacokinetics and enhance the antitumor effect of arsenic trioxide. The mesoporous silica nanoparticles loaded with arsenic trioxide was grafted with polyacrylic acid (PAA-ATO-MSN) as a pH-responsive biomaterial on the surface to achieve the release of drug in acidic microenvironment of tumor, instead of burst release action in circulation. The nanoparticles were characterized with uniform grain size (particle sizes of 158.6 ± 1.3 nm and pore sizes of 3.71 nm, respectively), historically comparable drug loading efficiency (11.42 ± 1.75%), pH-responsive and strengthened sustained release features. The cell toxicity of amino groups modified mesoporous silica nanoparticles (NH2-MSN) was significantly reduced by capping of polyacrylic acid. In pharmacokinetic studies, the half time (t1/2β) was prolonged by 1.3 times, and the area under curve) was increased by 2.6 times in PAA-ATO-MSN group compared with free arsenic trioxide group. Subsequently, the antitumor efficacy in vitro (SMMC-7721 cell line) and in vivo (H22 xenografts) was remarkably enhanced indicated that PAA-ATO-MSN improved the antitumor effect of the drug. These results suggest that the polyacrylic acid capped mesoporous silica nanoparticles (PAA-MSN) will be a promising nanocarrier for improving pharmacokinetic features and enhancing the anti-tumor efficacy of arsenic trioxide.

Synergistic targeted therapy for acute promyelocytic leukaemia: a model of translational research in human cancer

Acute promyelocytic leukaemia (APL), the M3 subtype of acute myeloid leukaemia, was once a lethal disease, yet nowadays the majority of patients with APL can be successfully cured by molecularly targeted therapy. This dramatic improvement in the survival rate is an example of the advantage of modern medicine. APL is characterized by a balanced reciprocal chromosomal translocation fusing the promyelocytic leukaemia (PML) gene on chromosome 15 with the retinoic acid receptor α (RARα) gene on chromosome 17. It has been found that all-trans-retinoic acid (ATRA) or arsenic trioxide (ATO) alone exerts therapeutic effect on APL patients with the PML-RARα fusion gene, and the combination of both drugs can act synergistically to further enhance the cure rate of the patients. Here, we provide an insight into the pathogenesis of APL and the mechanisms underlying the respective roles of ATRA and ATO. In addition, treatments that lead to more effective differentiation and apoptosis of APL cells, including leukaemia-initiating cells, and more thorough eradication of the disease will be discussed. Moreover, as a model of translational research, the development of a cure for APL has followed a bidirectional approach of 'bench to bedside' and 'bedside to bench', which can serve as a valuable example for the diagnosis and treatment of other malignancies.

Mutations of Epigenetic Modifier Genes as a Poor Prognostic Factor in Acute Promyelocytic Leukemia Under Treatment With All-Trans Retinoic Acid and Arsenic Trioxide

BACKGROUND

Acute promyelocytic leukemia (APL) is a model for synergistic target cancer therapy using all-trans retinoic acid (ATRA) and arsenic trioxide (ATO), which yields a very high 5-year overall survival (OS) rate of 85 to 90%. Nevertheless, about 15% of APL patients still get early death or relapse. We performed this study to address the possible impact of additional gene mutations on the outcome of APL.

METHODS

We included a consecutive series of 266 cases as training group, and then validated the results in a testing group of 269 patients to investigate the potential prognostic gene mutations, including FLT3-ITD or -TKD, N-RAS, C-KIT, NPM1, CEPBA, WT1, ASXL1, DNMT3A, MLL (fusions and PTD), IDH1, IDH2 and TET2.

RESULTS

More high-risk patients (50.4%) carried additional mutations, as compared with intermediate- and low-risk ones. The mutations of epigenetic modifier genes were associated with poor prognosis in terms of disease-free survival in both training (HR = 6.761, 95% CI 2.179-20.984; P = 0.001) and validation (HR = 4.026, 95% CI 1.089-14.878; P = 0.037) groups. Sanz risk stratification was associated with CR induction and OS.

CONCLUSION

In an era of ATRA/ATO treatment, both molecular markers and clinical parameter based stratification systems should be used as prognostic factors for APL.

Dose-adjusted arsenic trioxide for acute promyelocytic leukaemia in chronic renal failure

OBJECTIVE

To determine the potential for arsenic trioxide (ATO) to be safely and effectively incorporated into induction therapy of newly diagnosed acute promyelocytic leukaemia (APL) in patients with severe chronic renal failure (CRF) by reduction of the ATO dosage to compensate for reduced renal elimination of arsenic in CRF.

PATIENTS AND METHODS

Two of the four CRF patients with APL in the study were dialysis-dependent, and two had eGFRs of 18 and 19 mL/min/1.73 m(2) . ATO dosage schedules were adjusted to obtain comparable whole-blood arsenic levels to those in APL patients with normal renal function who achieved molecular remission (MR) while receiving 10 mg ATO daily for 28 d.

RESULTS

Average ATO administered per day in CRF patients ranged from 36 to 50% of the ATO administered to APL patients with normal renal function. No clinically significant cardiac, hepatic or other toxicities were detected. RT-PCR-negative MR was achieved after one treatment course in two patients and after two courses in the others. Relapse-free survival is 155, 60, 43 and 5 months.

CONCLUSION

The observations in this pilot study have demonstrated whole-blood arsenic levels can provide a guide to adjustments of ATO dosage schedules that permit safe and effective therapeutic outcomes in APL patients with severely compromised renal function.

Synthesis, crystal structure and properties of sandwich type compounds based on {AsW9} and a hexa-nuclear unit with three supporting TM–triazole complexes

Tree {AsW₉}-based sandwich compounds exhibit good electrocatalytic activity, antiferromagnetic interactions, and inhibitory effect on proliferation of HeLa cells.

Arsenic trioxide exerts a double effect on osteoblast growth in vitro

Arsenic trioxide (ATO) is a promising antitumor agent used to treat acute promyelocytic leukemia (APL) and, recently solid tumor. The present study was designed to evaluate the effect of ATO proliferation of osteoblast that plays very important roles in maintaining the structure integrity and function of bone. Cell survives, apoptosis, collagen, and molecular targets were identified by multiple detecting techniques, including MTT assay, electron microscopy, collagen detecting kit, TUNEL kit, and western blot in hFOB1.19 human osteoblasts cell line. The results showed that low dose of ATO (0.25, 0.5, and 1μM) remarkably enhanced the viability of cultured osteoblasts in a concentration- and time-dependent manner. Intriguingly, a dual effect of high dose of ATO (5, 10, and 20μM) was also observed showing significant reduction in viability of culture osteoblasts at concentration- and time-dependent fashion. Moreover, low dose of ATO promoted secretion and synthesis of collagen, whereas high dose of ATO induced typical morphological characteristics of apoptosis in osteoblasts. Mechanically, western blot results demonstrated that low dose of ATO dramatically up-regulated TGF-β1 protein and activated p-AKT proliferative signaling. And, high dose of ATO increased Bax/Bcl-2 ratio in a time-dependent fashion and activated caspase-3 apoptotic signaling. These results demonstrate at the first time that ATO exerts a double effect on osteoblast function depending upon the concentration and provide a clue to rationally use ATO for clinicians to pay more attention to protect bone from the adverse effects of therapeutic dose of ATO during tumor therapy.

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.

Retiferols - synthesis and biological activity of a conceptually novel class of vitamin D analogs

INTRODUCTION

The hypothesis that retiferols are a novel class of vitamin D analogs with therapeutic potential has been recently proved. The CD-ring of vitamin D, originated from a steroid precursor, is not necessary for biological activity. The retiferol, disubstituted at C-13, was bound to the ligand-binding domain (LBD) of vitamin D receptor (VDR) just like the vitamin D hormone [1,25-(OH)2D3]. This finding opens the way for retiferols as a novel class of vitamin D therapeutics.

AREAS COVERED

This review presents the concept of retiferols and their structure evolution. Medicinal chemistry and therapeutic perspective of retiferols are reviewed showing how these vitamin D analogs became a source of potential therapeutics.

EXPERT OPINION

Docking experiments and molecular modeling have shown that positioning of vitamin D analog at the LBD of VDR is not disturbed by deletion of a large portion of the vitamin D, exactly as hypothesized. Twenty years of structural modifications have shown that removal of the CD-ring fragment and regioselective methylation results in an almost complete loss of the undesired calcemic activity of retiferol while gaining the agonistic activity comparable to that of 1,25-(OH)2D3.

Role of arsenic trioxide in acute promyelocytic leukemia

Acute promyelocytic leukemia (APL) is a unique subtype of acute myeloid leukemia that is characterized by distinct clinical, morphological, cytogenetic, and molecular abnormalities. It is associated with a striking risk of early hemorrhagic death due to disseminated intravascular coagulation and hyperfibrinolysis. The prognosis of APL has improved dramatically following the introduction of all-trans retinoic acid (ATRA) and its combination with anthracycline-based chemotherapy during induction and consolidation. Patients with high-risk APL, defined by a white cell count >10 × 10(9)/L at diagnosis, also appear to benefit from the addition of intermediate- or high-dose cytarabine during consolidation. Arsenic trioxide (ATO) has proved to be even more effective than ATRA as a single agent, and is now routinely used for the treatment of the 20%-30% of patients who manifest disease relapse after initial treatment with ATRA and chemotherapy. ATO has a toxicity profile that differs considerably from that of both ATRA and cytotoxic chemotherapy, and accordingly presents its own specific challenges during treatment. Optimizing a strategy for the incorporation of ATO into initial therapy is currently the focus of several cooperative group trials, with an emphasis on minimizing or even eradicating the use of chemotherapy. ATRA plus ATO without chemotherapy appears to be adequate during induction and consolidation for patients with standard-risk APL, but triple therapy that includes limited anthracycline or gemtuzumab ozogamicin (GO) during induction is required for high-risk APL. Uncertainty still exists regarding the minimum amount of chemotherapy and number of consolidation cycles necessary, the optimal scheduling of ATO, and the potential utility of oral ATO administration. Although prolonged oral maintenance therapy is usually included in most current APL treatment protocols, its value remains controversial, and the superior anti-leukemic efficacy of ATO-based therapy may facilitate its elimination in the future.

Nona-copper(II)-containing 18-tungsto-8-arsenate(III) exhibits antitumor activity

The nona-Cu(II)-containing tungstoarsenate(III) [H4{Cu(II)9As(III)6O15(H2O)6}(α-As(III)W9O33)2](8-) (1a) has been synthesized and characterized. Polyanion 1a comprises a unique, cylindrical {Cu(II)9As(III)6O15(H2O)6}(6+) cluster, which forms a large central cavity and is capped on either end by an [α-As(III)W9O33](9-) capping group. It exhibits remarkable activity against K562 leukaemia cells, as well as induces HepG2 cell apoptosis and autophagy.

Oral tetra-arsenic tetra-sulfide formula versus intravenous arsenic trioxide as first-line treatment of acute promyelocytic leukemia: a multicenter randomized controlled trial

PURPOSE

This randomized, multicenter, phase III noninferiority trial was designed to test the efficacy and safety of an oral tetra-arsenic tetra-sulfide (As4S4) -containing formula named the Realgar-Indigo naturalis formula (RIF) compared with intravenous arsenic trioxide (ATO) as both induction and maintenance therapies for newly diagnosed acute promyelocytic leukemia (APL).

PATIENTS AND METHODS

In all, 242 patients with APL were randomly assigned (1:1) to oral RIF (60 mg/kg) or ATO (0.16 mg/kg) combined with all-trans retinoic acid (ATRA; 25 mg/m(2)) during induction therapy. After achieving complete remission (CR), all patients received three courses of consolidation chemotherapy and maintenance treatment with sequential ATRA followed by either RIF or ATO for 2 years. The primary end point was the rate of disease-free survival (DFS) at 2 years, which was assessed for noninferiority with a 10% noninferiority margin.

RESULTS

The median follow-up time was 39 months. DFS at 2 years was 98.1% (106 of 108) in the RIF group and 95.5% (107 of 112) in the ATO group. The DFS difference was 2.6% (95% CI, -3.0% to 8.0%). The lower limit of the 95% CI of DFS difference was greater than the -10% noninferiority margin, confirming noninferiority (P < .001). No significant differences were noted between the RIF and ATO groups with regard to the CR rate (99.1% v 97.2%; P = .62) or the overall survival at 3 years (99.1% v 96.6%; P = .18). The rates of adverse events were similar in the two groups.

CONCLUSION

Oral RIF plus ATRA is not inferior to intravenous ATO plus ATRA as first-line treatment of APL and may be considered as a routine treatment option for appropriate patients.

Management of elderly patients with acute promyelocytic leukemia: progress and problems

Despite substantial progress in the management and outcome of acute promyelocytic leukemia (APL) during the last decades, older age remains a prominent negative prognostic factor. The improvement of long-term stabilization and cure of older APL patients is therefore a particular challenge. Data of unselected population-based studies suggest a high rate of exclusion from clinical trials in older age. The comparison of registry and study data indicates that study patients represent a positive selection. Older APL patients seem as sensitive to therapy as younger patients. With conventional therapy, based on all-trans retinoic acid (ATRA) and chemotherapy, over 50 % of older APL patients can probably be cured. Special problems of advanced age are the high rate of early death before or during induction therapy and the high frequency of death in remission with negative influence on the outcome. Both may be related in part to a higher vulnerability against the common treatment with ATRA and chemotherapy. Alternative less toxic approaches including arsenic trioxide (ATO) with or without ATRA and combinations with gemtuzumab ozogamicin or with reduced chemotherapy can induce long-lasting remission in all stages of APL. Considering the high curative potential and the excellent tolerance of ATO in newly diagnosed and relapsed APL, older patients are probably a particular target group for a chemotherapy-free approach with ATO.

Arsenic suppresses cell survival via Pirh2-mediated proteasomal degradation of ΔNp63 protein

Transcription factor p63, a member of the p53 family, shares a high degree of sequence similarity with p53. Because of transcription from two distinct promoters, the p63 gene encodes two isoforms, TAp63 and ΔNp63. Although TAp63 acts as a tumor suppressor, ΔNp63 functions as an oncogene and is often overexpressed in squamous cell carcinomas. Thus, therapeutic agents targeting ΔNp63 might be used to manage tumors that overexpress ΔNp63. Here we found that arsenic trioxide, a frontline agent for acute promyelocytic leukemia, inhibits ΔNp63 but not TAp63 expression in time- and dose-dependent manners. In addition, we found that arsenic trioxide decreases the stability of ΔNp63 protein via a proteasome-dependent pathway but has little effect on the level of ΔNp63 transcript. Furthermore, we found that arsenic trioxide activates the Pirh2 promoter and consequently induces Pirh2 expression. Consistent with this, we found that knockdown of Pirh2 inhibits, whereas ectopic expression of Pirh2 enhances, arsenic-induced degradation of ΔNp63 protein. Importantly, we found that knockdown of ΔNp63 sensitizes, whereas ectopic expression of ΔNp63 inhibits, growth suppression induced by arsenic. Together, these data suggest that arsenic degrades ΔNp63 protein at least in part via Pirh2-dependent proteolysis and that inhibition of ΔNp63 expression facilitates tumor cells to arsenic-induced death.

Telomere and microtubule targeting in treatment-sensitive and treatment-resistant human prostate cancer cells

Modulating telomere dynamics may be a useful strategy for targeting prostate cancer cells, because they generally have short telomeres. Because a plateau has been reached in the development of taxane-based treatments for prostate cancer, this study was undertaken to evaluate the relative efficacy of targeting telomeres and microtubules in taxane-sensitive, taxane-resistant, androgen-sensitive, and androgen-insensitive prostate cancer cells. Paclitaxel- and docetaxel-resistant DU145 cells were developed and their underlying adaptive responses were evaluated. Telomere dynamics and the effects of targeting telomeres with sodium meta-arsenite (KML001) (an agent undergoing early clinical trials), including combinations with paclitaxel and docetaxel, were evaluated in parental and drug-resistant cells. The studies were extended to androgen-sensitive LNCaP cells and androgen-insensitive LNCaP/C81 cells. Both P-glycoprotein (Pgp)-dependent and non-Pgp-dependent mechanisms of resistance were recruited within the same population of DU145 cells with selection for drug resistance. Wild-type DU145 cells have a small side population (SP) (0.4-1.2%). The SP fraction increased with increasing drug resistance, which was correlated with enhanced expression of Pgp but not breast cancer resistance protein. Telomere dynamics remained unchanged in taxane-resistant cells, which retained sensitivity to KML001. Furthermore, KML001 targeted SP and non-SP fractions, inducing DNA damage signaling in both fractions. KML001 induced telomere erosion, decreased telomerase gene expression, and was highly synergistic with the taxanes in wild-type and drug-resistant DU145 cells. This synergism extended to androgen-sensitive and androgen-insensitive LNCaP cells under basal and androgen-deprived conditions. These studies demonstrate that KML001 plus docetaxel and KML001 plus paclitaxel represent highly synergistic drug combinations that should be explored further in the different disease states of prostate cancer.

Characterization of the role of protein-cysteine residues in the binding with sodium arsenite

To better characterize the interaction of protein-cysteines with sodium arsenite, arsenic-binding proteins were identified from the arsenic-resistant Chinese hamster ovary cell line SA7 using a p-aminophenylarsine oxide (PAO)-agarose matrix in combination with proteomic techniques. Twenty of the isolated arsenic-binding proteins were further peptide-mapped by MALDI-Q-TOF-MS. The binding capacity of PAO-agarose-retained proteins was then verified by re-applying Escherichia coli overexpressed recombinant proteins with various numbers of cysteine residues onto the PAO-agarose matrix. The results showed that recombinant heat shock protein 27 (HSP27, with one cysteine residue), reticulocalbin-3 (RCN3, with no cysteine residue), galectin-1 (GAL1, with six cysteine residues), but not peroxiredoxin 6 (Prdx6, with one cysteine residue but not retained by the PAO-agarose matrix), were bound to the PAO-agarose matrix. The six free cysteine residues in GAL1 were individually or double-mutated to alanine by means of site-directed mutagenesis and subjected to CD and ICP-MS analysis. The binding capacity of GAL1 for sodium arsenite was significantly attenuated in C16A, C88A and all double mutant clones. Taken together, our current data suggest that the cysteine residues in GAL1 may play a critical role in the binding of arsenic, but that in the case of RCN3 and Prdx6, this interaction may be mediated by other factors.

YY1 is a novel potential therapeutic target for the treatment of HPV infection-induced cervical cancer by arsenic trioxide

OBJECTIVE

YY1 is a zinc finger transcription factor involved in the regulation of cell growth, development, and differentiation. Although YY1 can regulate human papillomavirus-type (HPV) viral oncogenes E6 and E7, it remains unknown if YY1 plays a key role in carcinoma progression of HPV-infected cells. Here we sought to determine whether YY1 is upregulated in the cervical cancer tissues and YY1 inhibition contributes to apoptosis of cervical cancer cells, which is at least partly p53 dependent. Therefore, YY1 can be a potential therapeutic target for cervical cancer treatment by arsenic trioxide (As2O3).

MATERIALS AND METHODS

The expression level of YY1 was examined and analyzed by Western blot in pathologically confirmed primary cervical cancer samples, in the adjacent normal samples, as well as in normal cervix samples. The effects of YY1 inhibition by specific small interfering RNA in HeLa cells were determined by Western blot analysis of p53 level, cell growth curve, colony formation assay, and apoptosis. The contribution of YY1 to As2O3-induced p53 activation and apoptosis was also examined by Western blot and cell cycle analysis.

RESULTS

Here we report that the expression level of YY1 is significantly elevated in the primary cancer tissues. In HPV-positive HeLa cells, small interfering RNA-mediated YY1 inhibition induced apoptosis and increased the expression of p53. Treatment of HeLa cells with As2O3, a known anti-cervical cancer agent, reduced both protein and mRNA levels of YY1 in HeLa cells. YY1 knockdown significantly further enhanced As2O3-induced apoptosis.

CONCLUSIONS

These results demonstrated that the expression of YY1 is upregulated in cervical carcinomas and that YY1 plays a critical role in the progression of HPV-positive cervical cancer. In addition, YY1 inhibition induces p53 activation and apoptosis in HPV-infected HeLa cells. Thus, YY1 is an As2O3 target and could serve as a potential drug sensitizer for anti-cervical cancer therapy.

Arsenic trioxide enhances the radiation sensitivity of androgen-dependent and -independent human prostate cancer cells

Prostate cancer is the most common malignancy in men. In the present study, LNCaP (androgen-sensitive human prostate cancer cells) and PC-3 cells (androgen-independent human prostate cancer cells) were used to investigate the anti-cancer effects of ionizing radiation (IR) combined with arsenic trioxide (ATO) and to determine the underlying mechanisms in vitro and in vivo. We found that IR combined with ATO increases the therapeutic efficacy compared to individual treatments in LNCaP and PC-3 human prostate cancer cells. In addition, combined treatment showed enhanced reactive oxygen species (ROS) generation compared to treatment with ATO or IR alone in PC-3 cells. Combined treatment induced autophagy and apoptosis in LNCaP cells, and mainly induced autophagy in PC-3 cells. The cell death that was induced by the combined treatment was primarily the result of inhibition of the Akt/mTOR signaling pathways. Furthermore, we found that the combined treatment of cells pre-treated with 3-MA resulted in a significant change in AO-positive cells and cytotoxicity. In an in vivo study, the combination treatment had anti-tumor growth effects. These novel findings suggest that combined treatment is a potential therapeutic strategy not only for androgen-dependent prostate cancer but also for androgen-independent prostate cancer.

Speciation of arsenic trioxide metabolites in peripheral blood and bone marrow from an acute promyelocytic leukemia patient

Background

Speciation of arsenic trioxide (ATO) metabolites in clinical samples such as peripheral blood (PB) from acute promyelocytic leukemia (APL) patients has been conducted. However, speciation of arsenicals in bone marrow (BM) has not yet been performed. Profiles of arsenic speciation in plasma of BM were thus investigated and compared with those of PB plasma from a relapsed APL patient. The total arsenic concentrations in high molecular weight fraction (HMW-F) of BM and PB plasma were also determined.

Methods

Response assessment was evaluated by BM aspirate examination and fluorescence in situ hybridization analysis. The analyses of total arsenic concentrations and speciation were preformed by inductively coupled plasma mass spectrometry (ICP-MS), and high-performance liquid chromatography (HPLC)/ICP-MS, respectively.

Results

Response assessment showed that the patient achieved complete remission. The total arsenic concentrations in BM plasma increased with time during the consecutive administration. The PB plasma concentrations of methylated arsenic metabolites substantially increased after the start of administration, while those of inorganic arsenic were still kept at a low level, followed by substantially increase from day-14 after administration. The arsenic speciation profiles of PB plasma were very similar to those of BM plasma. Furthermore, the total arsenic concentrations of HMW-F in BM plasma were much higher than those in PB plasma.

Conclusions

The behaviors of arsenic speciation suggested for the first time that arsenic speciation analysis of PB plasma could be predicative for BM speciation, and showed relatively higher efficiency of drug metabolism in the patient. These results may further provide not only significance of clinical application of ATO, but also a new insight into host defense mechanisms in APL patients undergoing ATO treatment, since HMW proteins-bound arsenic complex could be thought to protect BM from the attack of free arsenic species.

Impact of arsenic trioxide in the treatment of acute promyelocytic leukemia

Arsenic trioxide (ATO) is presently the most active single agent in the treatment of acute promyelocytic leukemia (APL). This review provides insights into the mode of action and the pharmacological properties of ATO, and summarizes the most relevant results of more than 20 treatment studies in relapsed or newly diagnosed APL published between 1997 and 2011. ATO acts by targeting multiple pathways in APL leading to apoptosis and myeloid differentiation. It induces complete remission without myelosuppression and causes only few adverse effects. In relapsed APL, ATO-based salvage therapy has been able to induce long-lasting remissions and possible cure in 50-81% of patients. In newly diagnosed APL, two main strategies are currently pursued. ATO is either included into induction therapy with the aim to minimize or eliminate chemotherapy, or it is incorporated as an additive into established first-line concepts with all-trans-retinoic acid and chemotherapy to reinforce their anti-leukemic efficacy. Recent results suggest a high efficacy of ATO in both concepts. In conclusion, experimental research and clinical studies have made contributions toward a better understanding of the molecular mechanisms induced by ATO in APL cells and have established this historic substance as an important candidate for the further improvement of APL therapy.

MicroRNA-32 upregulation by 1,25-dihydroxyvitamin D3 in human myeloid leukemia cells leads to Bim targeting and inhibition of AraC-induced apoptosis

1,25-Dihydroxyvitamin D(3) (1,25D) used to treat human acute myeloid leukemia (AML) cells induces features of normal monocytes, but the mechanisms underlying this response are not fully understood. We hypothesized that one or more microRNAs (miRNA) known to control mouse hematopoiesis and lineage commitment might contribute to the ability of 1,25D to control the malignant phenotype. Here we report that 1,25D markedly induces expression of miR-32 in human myeloid leukemia cells, in which it targets the 3'-untranslated region of the mRNA encoding the proapoptotic factor Bim to reduce its expression. RNAi-mediated suppression of the miRNA-processing enzymes Drosha and Dicer increased Bim levels, in support of the concept that Bim is under miRNA control in AML cells. Antisense-mediated suppression of miR-32 was sufficient to upregulate Bim expression in AML cells. Conversely, ectopic expression of miR-32 downregulated Bim expression and increased the differentiation response to 1,25D treatment in a manner that was associated with increased cell survival. The positive effects of miR-32 on cell survival were confirmed by evidence of increased cell death in AML cells preexposed to antisense miR-32 before treatment with arabinocytosine, a chemotherapeutic drug used to treat human AML. Together, our findings indicate that miR-32 blockade is sufficient to elevate Bim expression and sensitize AML cells to chemotherapy-induced apoptosis. Thus, agents which can inhibit miR-32 expression may offer clinical utility by enhancing therapeutic efficacy in human AML.

Arsenic oxide targets stem cell marker CD133/prominin-1 in gallbladder carcinoma

CD133+ tumor cells are responsible for the initiation, propagation and recurrence of tumors, which raises the question of how to effectively target CD133+ tumor cells. Arsenic trioxide (As2O3) has considerable efficacy in treating solid tumors with induction of apoptosis. Here, we found that purified CD133+ gallbladder carcinoma cells are highly resistant to conventional chemotherapy. However, As2O3 effectively induces CD133+ gallbladder carcinoma cells apoptosis. Treatment with As2O3 reduces CD133 expression at transcriptional levels. Furthermore, the ectopic expression of CD133 attenuated the apoptotic effect of As2O3 on cells through activation of AKT signaling pathways. Collectively, As2O3 effectively targets CD133 in gallbladder carcinoma, providing a new mechanism of As2O3-induced cell apoptosis and a better understanding of drug resistance in gallbladder carcinoma.

Arsenic trioxide and radiation enhance apoptotic effects in HL-60 cells through increased ROS generation and regulation of JNK and p38 MAPK signaling pathways

The induction of apoptotic cell death is a significant mechanism of tumor cells under the influence of radio-/chemotherapy, and resistance to these treatments has been linked to some cancer cell lines with a low propensity for apoptosis. The present study aimed to investigate the enhanced effects and mechanisms in apoptosis and the cycle distribution of HL-60 cells, a human leukemia cell line lacking a functional p53 protein, after combination treatment with arsenic trioxide (ATO) and irradiation (IR). Our results indicated that combined treatment led to increased cytotoxicity and apoptotic cell death in HL-60 cells, which was correlated with the activation of cdc-2 and increased expression of cyclin B, the induction of intracellular reactive oxygen species (ROS) generation, the loss of mitochondria membrane potential, and the activation of caspase-3. The combined treatment of HL-60 cells pre-treated with Z-VAD or NAC resulted in a significant reduction in apoptotic cells. In addition, activation of JNK and p38 MAPK may be involved in combined treatment-mediated apoptosis. The data suggest that a combination of IR and ATO could be a potential therapeutic strategy against p53-deficient leukemia cells.

Differentiation therapy of acute myeloid leukemia

Acute Myeloid Leukemia (AML) is a predominant acute leukemia among adults, characterized by accumulation of malignantly transformed immature myeloid precursors. A very attractive way to treat myeloid leukemia, which is now called 'differentiation therapy', was proposed as in vitro studies have shown that a variety of agents stimulate differentiation of the cell lines isolated from leukemic patients. One of the differentiation-inducing agents, all-trans retinoic acid (ATRA), which can induce granulocytic differentiation in myeloid leukemic cell lines, has been introduced into clinics to treat patients with acute promyelocytic leukemia (APL) in which a PML-RARA fusion protein is generated by a t(15;17)(q22;q12) chromosomal translocation. Because differentiation therapy using ATRA has significantly improved prognosis for patients with APL, many efforts have been made to find alternative differentiating agents. Since 1,25-dihydroxyvitamin D3 (1,25D) is capable of inducing in vitro monocyte/macrophage differentiation of myeloid leukemic cells, clinical trials have been performed to estimate its potential to treat patients with AML or myelodysplastic syndrome (MDS). Unfortunately therapeutic concentrations of 1,25D can induce potentially fatal systemic hypercalcemia, thus limiting clinical utility of that compound. Attempts to overcome this problem have focused on the synthesis of 1,25D analogs (VDAs) which retain differentiation inducing potential, but lack its hypercalcemic effects. This review aims to discuss current problems and potential solutions in differentiation therapy of AML.

Mutant p53 protein is targeted by arsenic for degradation and plays a role in arsenic-mediated growth suppression

p53 is frequently mutated in tumor cells, and mutant p53 is often highly expressed due to its increased half-life. Thus, targeting mutant p53 for degradation might be explored as a therapeutic strategy to manage tumors that are addicted to mutant p53 for survival. Arsenic trioxide, a drug for patients with acute promyelocytic leukemia, is found to target and degrade a class of proteins with high levels of cysteine residues and vicinal thiol groups, such as promyelocytic leukemia protein (PML) and PML-retinoic acid receptor α fusion protein. Interestingly, wild type p53 is accumulated in cells treated with arsenic compounds, presumably due to arsenic-induced oxidative stresses. In this study, we found that wild type p53 is induced by arsenic trioxide in tumor cells, consistent with published studies. In contrast, we found that arsenic compounds degrade both endogenous and ectopically expressed mutant p53 in time- and dose-dependent manners. We also found that arsenic trioxide decreases the stability of mutant p53 protein through a proteasomal pathway, and blockage of mutant p53 nuclear export can alleviate the arsenic-induced mutant p53 degradation. Furthermore, we found that knockdown of endogenous mutant p53 sensitizes, whereas ectopic expression of mutant p53 desensitizes, tumor cells to arsenic treatment. Taken together, we found that mutant p53 is a target of arsenic compounds, which provides an insight into exploring arsenic compound-based therapy for tumors harboring a mutant p53.

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.