Arsenic trioxide therapy for relapsed or refractory Japanese patients with acute promyelocytic leukemia: need for careful electrocardiogram monitoring

Risk factors and remaining challenges in the treatment of acute promyelocytic leukemia

The treatment of acute promyelocytic leukemia (APL) has evolved with the introduction of all-trans retinoic acid (ATRA) and subsequent arsenic trioxide (ATO), particularly in standard-risk APL with an initial white blood cell count (WBC) < 10,000/μL, where a high cure rate can now be achieved. However, for some patients with risk factors, early death or relapse remains a concern. Insights from the analysis of patients treated with ATRA and chemotherapy have identified risk factors such as WBC, surface antigens, complex karyotypes, FLT3 and other genetic mutations, p73 isoforms, variant rearrangements, and drug resistance mutations. However, in the ATRA + ATO era, the significance of these risk factors is changing. This article provides a comprehensive review of APL risk factors, taking into account the treatment approach, and explores the challenges associated with APL treatments.

Darinaparsin in patients with relapsed or refractory peripheral T-cell lymphoma: results of an Asian phase 2 study

Darinaparsin is a novel organic arsenical compound of dimethylated arsenic conjugated to glutathione, with antitumor activity and a mechanism of action markedly different from other available agents. This phase 2, nonrandomized, single-arm, open-label study evaluated the efficacy and safety of intravenous darinaparsin (300 mg/m2 over 1 hour, once daily for 5 consecutive days, per 21-day cycle) and its pharmacokinetics at multiple doses in 65 Asian patients with relapsed or refractory peripheral T-cell lymphoma (PTCL). The primary end point was the overall response rate (ORR). The ORR based on central assessment was 19.3% (90% confidence interval, 11.2-29.9), which was significantly higher than the predefined threshold of 10% (P = .024). The ORR was 16.2% in patients with PTCL-not otherwise specified and 29.4% in patients with angioimmunoblastic T-cell lymphoma. Tumor size decreased in 62.3% of patients. Treatment-emergent adverse events (TEAEs) were observed in 98.5% of patients. Grade ≥3 TEAEs with an incidence rate of ≥5% included anemia (15.4%), thrombocytopenia (13.8%), neutropenia (12.3%), leukopenia (9.2%), lymphopenia (9.2%), and hypertension (6.2%). Darinaparsin is effective and well tolerated, with TEAEs that were clinically acceptable and manageable with symptomatic treatment and dose reductions. This trial was registered at www.clinicaltrials.gov as #NCT02653976.

Arsenic exposure and pruritus: Evidence from observational, interventional, and mendelian randomization studies

BACKGROUND

Pruritus is identified as an adverse drug reaction to arsenic trioxide, but the association of arsenic exposure with pruritus has not been investigated.

METHODS

A cross-sectional study was conducted in Shimen, China. A Mendelian randomization analysis was conducted to confirm the causal relationship between genetically predicted percentages of monomethylated arsenic (MMA%) and dimethylated arsenic (DMA%) in urine with chronic pruritus in UK Biobank. A case-control study was then conducted to determine the biomarker for pruritus. Arsenite-treated mice were used to confirm the biomarker, and von Frey test was used to induce scratching bouts. Last, a randomized, double-blind, placebo-controlled trial was conducted to test the efficacy of naloxone in arsenic-exposed patients with pruritus in Shimen.

RESULTS

Hair arsenic (μg/g) showed a dose-response relationship with the intensity of itch in 1079 participants, with odds ratios (OR) of 1.11 for moderate-to-severe itch (p = 0.012). The Mendelian randomization analysis confirmed the causal relationship, with ORs of 1.043 for MMA% (p = 0.029) and 0.904 for DMA% (p = 0.077) above versus under median. Serum β-endorphin was identified as a significant biomarker for the intensity of itch (p < 0.001). Consistently, treatment with arsenite upregulated the level of β-endorphin (p = 0.002) and induced scratching bouts (p < 0.001) in mice. The randomized controlled trial in 126 participants showed that treatment with sublingual naloxone significantly relieved the intensity of itch in arsenic-exposed participants in 2 weeks (β = -0.98, p = 0.04).

CONCLUSION

Arsenic exposure is associated with pruritus, and β-endorphin serves as a biomarker of pruritus. Naloxone relieves pruritus in patients with arseniasis.

Japanese subgroup analysis in the Asian phase II study of darinaparsin in patients with relapsed or refractory peripheral T-cell lymphoma

A Japanese subgroup analysis from the Asian phase II study of darinaparsin in patients with relapsed or refractory peripheral T-cell lymphoma (PTCL) was performed to evaluate the efficacy and safety outcomes of the Japanese population. In this Asian phase II study, darinaparsin was administered to 65 patients, including 37 Japanese patients. In the Japanese population, the histopathological type of PTCL was PTCL, not otherwise specified in 26 patients (70.3%), angioimmunoblastic T-cell lymphoma in 9 patients (24.3%) and anaplastic large cell lymphoma, anaplastic lymphoma kinase (ALK) -negative in 2 patients (5.4%), and the median patient age was 70.0 (range: 43-85). 94.6% and 35.1% of the Japanese population had previously received multi-agent and single-agent regimen, respectively. The efficacy and safety were summarized and compared between the overall and Japanese populations. Based on central assessment, the overall response rate was 22.2% (8/36; 90% confidence interval [CI]: 11.6-36.5) in the Japanese population and 19.3% (11/57; 90% CI: 11.2-29.9) in the overall population. There were no essential differences in the safety profile of darinaparsin between the Japanese population and the overall population. The results of this subgroup analysis indicate that the efficacy and safety profiles of the Japanese subpopulation were broadly consistent with that of the overall population, and that darinaparsin is potentially an effective treatment with a manageable safety profile in Japanese patients with relapse or refractory PTCL.

Urolithin A attenuates arsenic-induced gut barrier dysfunction

Environmental chemicals such as inorganic arsenic (iAs) significantly contribute to redox toxicity in the human body by enhancing oxidative stress. Imbalanced oxidative stress rapidly interferes with gut homeostasis and affects variety of cellular processes such as proliferation, apoptosis, and maintenance of intestinal barrier integrity. It has been shown that gut microbiota are essential to protect against iAs3+-induced toxicity. However, the effect of microbial metabolites on iAs3+-induced toxicity and loss of gut barrier integrity has not been investigated. The objectives of the study are to investigate impact of iAs on gut barrier function and determine benefits of gut microbial metabolite, urolithin A (UroA) against iAs3+-induced adversaries on gut epithelium. We have utilized both colon epithelial cells and in a human intestinal 3D organoid model system to investigate iAs3+-induced cell toxicity, oxidative stress, and gut barrier dysfunction in the presence or absence of UroA. Here, we report that treatment with UroA attenuated iAs3+-induced cell toxicity, apoptosis, and oxidative stress in colon epithelial cells. Moreover, our data suggest that UroA significantly reduces iAs3+-induced gut barrier permeability and inflammatory markers in both colon epithelial cells and in a human intestinal 3D organoid model system. Mechanistically, UroA protected against iAs3+-induced disruption of tight junctional proteins in intestinal epithelial cells through blockade of oxidative stress and markers of inflammation. Taken together, our studies for the first time suggest that microbial metabolites such as UroA can potentially be used to protect against environmental hazards by reducing intestinal oxidative stress and by enhancing gut barrier function.

Phase I studies of darinaparsin in patients with relapsed or refractory peripheral T-cell lymphoma: a pooled analysis of two phase I studies conducted in Japan and Korea

OBJECTIVE

Two phase I studies of darinaparsin including Japanese and Korean patients with relapsed/refractory peripheral T-cell lymphoma were performed to evaluate its safety (primary purpose), efficacy and pharmacokinetic profile (ClinicalTrials.gov: NCT01435863 and NCT01689220).

METHODS

Patients received intravenous darinaparsin for 5 consecutive days at 200 mg/m2/day in 4-week cycles, 300 mg/m2/day in 4-week cycles or 300 mg/m2/day in 3-week cycles.

RESULTS

Seventeen Japanese and 6 Korean patients were enrolled and treated. Drug-related adverse events developed in 18 patients (78%). Dose-limiting toxicity, grade 3 hepatic dysfunction, was reported on Day 15 of cycle 1 in 1 Japanese patient who received 300 mg/m2/day. The most common drug-related, grade ≥ 3 adverse events were lymphopenia (9%), neutropenia (9%) and thrombocytopenia (9%). No deaths occurred. In 14 evaluable patients, 1 and 3 patients had complete response and partial response, respectively. The plasma concentration-time profiles of arsenic, a surrogate marker for darinaparsin, were similar between Japanese and Korean patients. No significant difference was found in its pharmacokinetic profile.

CONCLUSIONS

These data indicate the good tolerability and potential efficacy of darinaparsin in patients with relapsed/refractory peripheral T-cell lymphoma. Darinaparsin 300 mg/m2/day for 5 consecutive days in 3-week cycles is the recommended regimen for phase II study.

Incidence of Differentiation Syndrome Associated with Treatment Regimens in Acute Myeloid Leukemia: A Systematic Review of the Literature

Differentiation syndrome (DS) is a potentially fatal adverse drug reaction caused by the so-called differentiating agents such as all-trans retinoic acid (ATRA) and arsenic trioxide (ATO), used for remission induction in the treatment of the M3 subtype of acute myeloid leukemia (AML), acute promyelocytic leukemia (APL). However, recent DS reports in trials of isocitrate dehydrogenase (IDH)-inhibitor drugs in patients with IDH-mutated AML have raised concerns. Given the limited knowledge of the incidence of DS with differentiating agents, we conducted a systematic literature review of clinical trials with reports of DS to provide a comprehensive overview of the medications associated with DS. In particular, we focused on the incidence of DS reported among the IDH-inhibitors, compared to existing ATRA and ATO therapies. We identified 44 published articles, encompassing 39 clinical trials, including 6949 patients. Overall, the cumulative incidence of DS across all treatment regimens was 17.7%. Incidence of DS was notably lower in trials with IDH-inhibitors (10.4%) compared to other regimens, including ATRA and/or ATO (15.4-20.6%). Compared to other therapies, the median time to onset was four times longer with IDH-inhibitors (48 vs. 11 days). Treating oncologists should be mindful of this potentially fatal adverse drug reaction, as we expect the current trials represent an underestimation of the actual incidence.

Patient-Reported Outcomes of Arsenic-Related Skin Lesions in China

Purpose

Previous studies confirmed that chronic arsenic exposure could lead to pigmentary changes and hyperkeratosis. However, skin health-related quality of life (HRQoL) among people under lifetime arsenic exposure remains underappreciated. Our study is aimed at investigating several patient-reported outcomes in a population under chronic arsenic exposure. Patients and Methods. A cross-sectional study was conducted in communities in Shimen, China. Dermatologists performed skin examinations for participants. Patient-reported outcomes (PROs) included HRQoL, itch, sleep quality, and symptoms of anxiety and depression. The Dermatology Life Quality Index (DLQI) was used to measure skin HRQoL. The numerical rating scale (NRS) was used to measure the intensity of itching. Sleep disturbance was measured by Pittsburgh Sleep Quality Index (PSQI). Anxiety and depression were measured by two-item Generalized Anxiety Disorder (GAD-2) and Patient Health Questionnaire (PHQ-2), respectively.

Results

A total of 464 participants suffering from arsenic-related skin lesions finished the assessment of DLQI. Pigmentary changes and arsenical keratosis were not associated with the patient-reported outcomes except PHQ-2. Hair arsenic exceeding 1 μg/g was associated with higher itch NRS and DLQI (P < 0.05). Itch NRS (adjusted β = 0.80, 95% CI: 0.70–0.90, P < 0.01) and hair arsenic concentration (adjusted β = 0.12, 95% CI: 0.01–0.24, P < 0.05) were independently associated with the DLQI.

Conclusion

HRQoL, sleep quality, and mental wellbeing are impaired in residents under chronic arsenic exposure. Itching and hair arsenic are independent risk factors for impaired HRQoL.

Crocin ameliorates arsenic trioxide‑induced cardiotoxicity via Keap1-Nrf2/HO-1 pathway: Reducing oxidative stress, inflammation, and apoptosis

Arsenic trioxide (ATO) is an excellent therapy for acute promyelocytic leukemia; however, its use is limited due to its cardiotoxicity. Crocin (CRO) possesses abundant pharmacological and biological properties, including antioxidant, anti-inflammatory, and anti-apoptotic. This study examined the cardioprotective effects of crocin and explored their mechanistic involvement in ATO-induced cardiotoxicity. Forty-eight male rats were treated with ATO to induce cardiotoxicity. In combination with ATO, CRO were given to evaluate its cardioprotection. The results demonstrated that CRO administration not only diminished QTc prolongation, myocardial enzymes and Troponin T levels but also improved histopathological results. CRO administration reduced reactive oxygen species generation. However, the CRO administration caused an increase in glutathione, superoxide dismutase, catalase, glutathione peroxidase, glutathione S-transferase and total sulphydryl levels and a decrease in malondialdehyde content, gamma glutamyl transferase and lipid hydroperoxides levels and proinflammatory cytokines. Importantly, immunohistochemical analysis, real time PCR and western blotting showed a reduction in Caspase-3 and Bcl-2-associated X protein expressions and enhancement of B cell lymphoma-2 expression. Real time PCR and western blotting showed a reduction in proinflammatory cytokines. Moreover, CRO caused an activation in nuclear factor erythroid-2 related factor 2, leading to enhanced Kelch-like ECH-associated protein 1, heme oxygenase-1 and nicotinamide adenine dinucleotide quinone dehydrogenase 1 expressions involved in Nrf2 signaling during ATO-induced cardiotoxicity. CRO was shown to ameliorate ATO-induced cardiotoxicity. The mechanisms for CRO amelioration of cardiotoxicity due to inflammation, oxidative damage, and apoptosis may occur via an up-regulated Keap1-Nrf2/HO-1 signaling pathway.

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.

Assessment of the Dermatology Life Quality Index (DLQI) in a homogeneous population under lifetime arsenic exposure

PURPOSE

The psychometric property of the Dermatology Life Quality Index (DLQI) is underappreciated in public health settings. Our study aimed to assess the reliability, validity, and measurement invariance of DLQI in a homogeneous population with arsenic-related skin lesions and symptoms.

METHODS

A cross-sectional study was conducted in communities under lifetime arsenic exposure. The DLQI was measured through a face-to-face interview. Skin examinations were performed by certificated dermatologists. The intensity of itching was measured by a numerical rating scale. Reliability, structural validity, and measurement invariance were determined using classical and modern test theories, including confirmatory factor analysis and item response models.

RESULTS

465 participants with arsenic-related skin lesions and symptoms completed the DLQI assessment. The Cronbach's alpha was 0.79, and the split-half reliability was 0.77. A two-factor model exhibited the best model fit among models evaluated, but local dependencies among items were identified. The model showed good root mean square error of approximation (0.031) and acceptable Tucker-Lewis index (0.92). Multi-group confirmatory factor analysis showed no measurement invariance across subgroups of age, gender, ethnicity, and intensity of itching.

CONCLUSIONS

The DLQI had acceptable psychometric properties, but measurement invariance was not observed across different groups of participants.

(-)-Epicatechin rescues the As2 O3 -induced HERG K+ channel deficiency possibly through upregulating transcription factor SP1 expression

(-)-Epicatechin (EPI) has beneficial effects on the cardiovascular disease. The human ether-a-go-go-related gene (HERG) potassium channel is crucial for repolarization of cardiac action potential. Dysfunction of the HERG channel can cause long QT syndrome type 2 (LQT2). Arsenic trioxide (As2 O3 ) has shown efficacy in the treatment of acute promyelocytic leukemia. However, As2 O3 can induce the deficiency of HERG channel and cause LQT2. In this study, we examined whether EPI could rescue the As2 O3 -induced HERG channel deficiency. We found that 3 μM EPI obviously increased protein expression and current of HERG channel. EPI was able to recover the protein expression and current of HERG channel disrupted by As2 O3 . EPI was able to increase the expression of SP1 protein and recover the expression of SP1 protein disrupted by As2 O3 . In addition, EPI significantly shortened action potential duration prolonged by As2 O3 . Our data suggest that EPI rescues As2 O3 -induced HERG channel deficiency through upregulating SP1 expression.

Current first- and second-line treatment options in acute promyelocytic leukemia

Outcome of acute promyelocytic leukemia (APL) has remarkably improved during the last 30 years, especially after the identification of PML-RARA oncogene as a key in the pathogenesis of APL and all-trans retinoic acid as therapeutic agent. Arsenic trioxide has been recently demonstrated to be the most effective single antileukemic agent and it has also showed synergistic action when combined with all-trans retinoic acid, decreasing relapse rate especially in low/intermediate-risk settings. Therapeutic advances led to complete remission rates of more than 90%, modifying disease history. In relapse setting, arsenic trioxide-based regimens showed efficacy for the achievement of second molecular complete remission. The most challenging issue in APL management remains the significant early deaths rate, nowadays the principal reason for treatment failure.

Differential mechanistic investigation of protective effects from imperatorin and sec-O-glucosylhamaudol against arsenic trioxide-induced cytotoxicity in vitro

BACKGROUND AND PURPOSE

The clinical use of arsenic trioxide (As₂O₃) for treating acute promyelocytic leukemia (APL) is limited due to its severe cardiotoxicity. The possible mechanisms of As₂O₃-induced cardiotoxicity include DNA fragmentation, reactive oxygen species (ROS) generation, cardiac ion channel changes and apoptosis. The present study is designed to investigate the protective effects of imperatorin and sec-O-glucosylhamaudol and to explore their mechanistic involvement in As₂O₃-induced cytotoxicity.

EXPERIMENTAL METHODS

Cell viability assay, Lactate dehydrogenase (LDH) release, Acridine orange/ethidium bromide (AO/EB) double staining, Caspase-3 activity assay, ROS generation, cellular calcium levels, mRNA expression levels by qRT-PCR and protein expression levels by Western blotting were measured in H9c2 cells in combination with As₂O₃ and imperatorin or sec-O-glucosylhamaudol.

KEY RESULTS

We observed that H9c2 cells treated with imperatorin or sec-O-glucosylhamaudol were more resistant to As₂O₃-induced cell death. Both imperatorin and sec-O-glucosylhamaudol reduced H9c2 cell apoptosis, but both imperatorin and sec-O-glucosylhamaudol had no effects on Caspase-3 activity and intracellular calcium accumulation. Furthermore, imperatorin was capable of suppressing ROS generation, while sec-O-glucosylhamaudol did not show this effect. Moreover, imperatorin and sec-O-glucosylhamaudol triggered Nrf2 activation, which resulted in upregulation of downstream phase II metabolic enzymes and antioxidant protein/enzyme, probably offering cellular protection to As₂O₃-induced cardiotoxicity via the Nrf2 signal pathway.

CONCLUSIONS AND IMPLICATIONS

Imperatorin and sec-O-glucosylhamaudol can ameliorate As₂O₃-induced cytotoxicity and apoptosis in H9c2 cells, the mechanisms probably related to antioxidation. As₂O₃ in combination with imperatorin or sec-O-glucosylhamaudol could be considered as a novel strategy to expand the clinical application of As₂O₃.

Arsenic trioxide-based therapy is suitable for patients with psoriasis-associated acute promyelocytic leukemia - A retrospective clinical study

OBJECTIVE

Many patients with psoriasis have developed acute promyelocytic leukemia (APL) whereas few reports on psoriasis-associated APL were found in the published literature. This study was aimed to study the etiology, clinical characteristics, and prognosis of psoriasis-associated APL and to map a suitable treatment regime for this condition.

METHODS

This study retrospectively analyzed the clinical data of 17 patients with psoriasis-associated APL diagnosed and treated in our hospital in the past decade.

RESULTS

The 17 patients accounted for 8.3% of the total patients diagnosed with de novo APL during the same period in our hospital. Their clinical characteristics of APL were similar to those of general APL. Four patients had a definite history of taking bimolane. All patients received arsenic trioxide (ATO)-based remission induction and postremission treatment. After induction, 15 patients (88%) achieved hematologic complete remission. With a median follow-up of 27 months, the 3-year estimates of overall survival were 77.2% ± 12.4% and the 3-year estimates of event-free survival were 70.6% ± 13.5%. In addition, the ATO-based remission induction and postremission treatment significantly improved psoriasis symptoms in 83 and 85.7% of patients, respectively. Through the final follow-up, no chronic arsenicosis or secondary malignancy was observed.

CONCLUSIONS

Psoriasis patients are at high risk for APL. The increased risk is most likely associated with the genetic background and bimolane treatment. The ATO-based therapy is especially suitable for patients with psoriasis-associated APL. Our study also brings a new treatment option for psoriasis.

Mechanisms of Cardiotoxicity of Cancer Chemotherapeutic Agents: Cardiomyopathy and Beyond

Tremendous strides have been made in the treatment of various oncological diseases such that patients are surviving longer and are having better quality of life. However, the success has been tainted by the iatrogenic cardiac toxicities. This is especially concerning in the younger population who are facing cardiac disease such as heart failure in their 30s and 40s as the consequence of the anthracycline's side effects (used for childhood leukemia and lymphoma). This resulted in the awareness of cardiotoxic effects of anticancer drugs and emergence of a new discipline: oncocardiology. Since then, numerous anticancer drugs have been correlated to cardiomyopathy. Additionally, other cardiovascular effects have been identified, which includes but is not limited to myocardial infarction, thrombosis, hypertension, arrhythmias, and pulmonary hypertension. In this review we examine some of the anticancer agents that mitigate cardiotoxicity and present current knowledge of molecular mechanism(s). The aim of the review is to ignite awareness of emerging cardiotoxic effects as new generations of anticancer agents are being tested in clinical trials and introduced as part of the therapeutic armamentarium to our oncological patients.

Up-regulation of miR-21 and miR-23a Contributes to As2 O3 -induced hERG Channel Deficiency

Arsenic trioxide (As2O3) is used to treat acute pro-myelocytic leukaemia. However, the cardiotoxicity of long QT syndrome restricts its clinical application. Previous studies showed that As2O3 can damage the hERG current via disturbing its trafficking to cellular membrane. Consistent with these findings, in this study, we reported that As2O3 inhibited hERG channel at both protein and mRNA levels and damaged hERG current but did not affect channel kinetics. Further, we demonstrated that As2O3 up-regulated miR-21 and miR-23a expression in hERG-HEK293 cells and neonatal cardiomyocytes. In addition, knock-down of miR-21 by its specific antisense molecules AMO-21 was able to rescue Sp1 and hERG inhibition caused by As2O3. Consistently, phosphorylation of NF-κB, the upstream regulatory factor of miR-21, was significantly up-regulated by As2O3 . This finding revealed that regulation of the NF-κB-miR-21-Sp1 signalling pathway is a novel mechanism for As2O3-induced hERG inhibition. Meanwhile, the expression of Hsp90 and hERG was rescued by transfection with AMO-23a. And the hERG channel inhibition induced by As2O3 was rescued after being transfected with AMO-23a, which may be a molecular mechanism for the role of As2O3 in hERG trafficking deficiency. In brief, our study revealed that miR-21 and miR-23a are involved in As2O3-induced hERG deficiency at transcriptional and transportational levels. This discovery may provide a novel mechanism of As2O3-induced hERG channel deficiency, and these miRNAs may serve as potential therapeutic targets for the handling of As2O3 cardiotoxicity.

Molecular mechanisms of the antileukemia activities of retinoid and arsenic

Acute promyelocytic leukemia (APL) is characterized by the occurrence of translocations between chromosomes 15 and 17, resulting in generation of a fusion protein of promyelocytic leukemia (PML) and retinoid A receptor (RAR) α. APL cells are unable to differentiate into mature granulocytes since PML-RARα functions as a strong transcriptional repressor for a gene involved in granulocyte differentiation. All-trans retinoic acid (ATRA) is the first agent that has been developed to target specific disease-causing molecules, i.e., ATRA suppresses abnormal functions of oncogenic proteins. Moreover, ATRA facilitates the differentiation of APL cells toward mature granulocytes by changing epigenetic modifiers from corepressor complexes to co-activator complexes on target genes after binding to the ligand-binding domain at the RARα moiety of the PML-RARα oncoprotein. On the other hand, arsenic trioxide (ATO), another promising agent used to treat APL, directly binds to the PML moiety of the PML-RARα protein, causing oxidation and multimerization. ATO enhances the conjugation of small ubiquitin-like modifiers to PML-RARα, followed by ubiquitination and degradation, relieving the genes associated with granulocytic differentiation from suppressive restraint by the oncoprotein. Recent clinical studies have demonstrated that combination therapy with both ATRA and ATO is useful to achieve remission.

α-Lipoic acid protects against arsenic trioxide-induced acute QT prolongation in anesthetized guinea pigs

Clinical use of arsenic trioxide (As₂O₃), which can induce the remission of relapsed or refractory acute promyelocytic leukemia, is often limited because of its cardiotoxicity. Symptoms of cardiotoxicity include acute cardiac conduction disturbances, such as QT prolongation. The present study was undertaken to evaluate the effects of α-lipoic acid (LA) on acute As₂O₃-induced ECG abnormalities (QTc interval prolongation) in anesthetized guinea pigs. Intravenous injection of As₂O₃ in guinea pigs caused QTc interval prolongation, which was significantly attenuated by co-treatment with LA (0.35, 3.5 and 35 mg/kg) in a dose-dependent manner. In isolated guinea pig cardiomyocytes, the decrease in IKs current induced by As₂O3 (1 μM) was rapidly restored to the basal level by the addition of LA (10 μM). Consistent with this finding, the As₂O₃-induced QTc interval prolongation was also improved rapidly by post-treatment with LA in guinea pigs. Electrospray ionization time-of-flight mass spectrometry analysis detected an expected peak of arsenic-LA complex in vitro, indicating that LA and As₂O3 form a new compound in vivo. In addition, pre-treatment with a chelating agent, British anti-Lewisite (BAL, 3.5 or 35 mg/kg), also attenuated the As₂O₃-induced QTc interval prolongation. In this study, co- and post-treatments with LA and pre-treatment with BAL ameliorated As₂O₃-induced acute QT prolongation in anesthetized guinea pigs. Because LA and probably BAL may bind to As₂O₃, these agents may exert protective effects through their chelating activity. Further studies are needed to determine whether LA is beneficial as a prophylactic or rescue agent for acute promyelocytic leukemia patients treated with As₂O₃.

Arsenic trioxide-induced hERG K(+) channel deficiency can be rescued by matrine and oxymatrine through up-regulating transcription factor Sp1 expression

The human ether-a-go-go-related gene (hERG) encodes the rapidly activating, delayed rectifier potassium channel (IKr) important for cardiac repolarization. Dysfunction of the hERG channel can cause Long QT Syndrome (LQTS). A wide variety of structurally diverse therapeutic compounds reduce the hERG current by acute direct inhibition of the hERG current or/and selective disruption of hERG protein expression. Arsenic trioxide (As(2)O(3)), which is used to treat acute promyelocytic leukemia, can cause LQTS type 2 (LQT2) by reducing the hERG current through the diversion of hERG trafficking to the cytoplasmic membrane. This cardiotoxicity limits its clinical applications. Our aim was to develop cardioprotective agents to decrease As(2)O(3)-induced cardiotoxicity. We reported that superfusion of hERG-expressing HEK293 (hERG-HEK) cells with matrine (1, 10 μM) increased the hERG current by promoting hERG channel activation. Long-term treatment with 1 μM matrine or oxymatrine increased expression of the hERG protein and rescued the hERG surface expression disrupted by As(2)O(3). In addition, Matrine and oxymatrine significantly shortened action potential duration prolonged by As(2)O(3) in guinea pig ventricular myocytes. These results were ascribed to the up-regulation of hERG at both mRNA and protein levels via an increase in the expression of transcription factor Sp1, an established transactivator of the hERG gene. Therefore, matrine and oxymatrine may have the potential to cure LQT2 as a potassium channel activator by promoting hERG channel activation and increasing hERG channel expression.

Direct effects of arsenic trioxide on action potentials in isolated cardiac tissues: importance of the choice of species, type of cardiac tissue and perfusion time

INTRODUCTION

The aim of the present study was to evaluate direct/acute effects of arsenic trioxide on action potentials (APs) in isolated cardiac tissues, and to investigate if the choice of species and tissue and the duration of the perfusion play a role in arsenic-induced acute/direct prolongation of AP/QT.

METHODS AND RESULTS

Direct electrophysiological effects of arsenic trioxide were measured in cardiac tissues isolated from four different species using micro-electrode recording. Arsenic (after 30 to 95 min perfusion at 10 μM) significantly prolonged APD(90), increased triangulation of the AP and elicited early afterdepolarizations (EADs) only in isolated guinea-pig and dog Purkinje fibers but not in rabbit and porcine (minipig) Purkinje fibers. Arsenic induced a prolongation of the APD(90) and increases in triangulation and the occurrence of EADs was not observed in papillary muscles of guinea-pigs and rabbits. Arsenic at 4 increasing concentrations from 0.1 μM to 10 μM at the standard perfusion-time of 15 min per concentration, and after a continuous 90-min perfusion at 1 μM and 1 Hz did not induce these direct effects on APD(90), triangulation and EADs in isolated guinea-pig Purkinje fibers, but it at 1 µM elicited EADs in 2 out of 7 preparations after 90 min at 0.2 Hz.

DISCUSSION

The present study demonstrates that the choice of species and cardiac tissue as well as perfusion-time play important roles in arsenic-induced direct/acute effects on APD(90) and induction of EADs in vitro.

Molecular determinants of pentamidine-induced hERG trafficking inhibition

Pentamidine is an antiprotozoal compound that clinically causes acquired long QT syndrome (acLQTS), which is associated with prolonged QT intervals, tachycardias, and sudden cardiac arrest. Pentamidine delays terminal repolarization in human heart by acutely blocking cardiac inward rectifier currents. At the same time, pentamidine reduces surface expression of the cardiac potassium channel I(Kr)/human ether à-go-go-related gene (hERG). This is unusual in that acLQTS is caused most often by direct block of the cardiac potassium current I(Kr)/hERG. The present study was designed to provide a more complete picture of how hERG surface expression is disrupted by pentamidine at the cellular and molecular levels. Using biochemical and electrophysiological methods, we found that pentamidine exclusively inhibits hERG export from the endoplasmic reticulum to the cell surface in a heterologous expression system as well as in cardiomyocytes. hERG trafficking inhibition could be rescued in the presence of the pharmacological chaperone astemizole. We used rescue experiments in combination with an extensive mutational analysis to locate an interaction site for pentamidine at phenylalanine 656, a crucial residue in the canonical drug binding site of terminally folded hERG. Our data suggest that pentamidine binding to a folding intermediate of hERG arrests channel maturation in a conformational state that cannot be exported from the endoplasmic reticulum. We propose that pentamidine is the founding member of a novel pharmacological entity whose members act as small molecule antichaperones.

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.

Interactive effect of arsenic and fluoride on cardio-respiratory disorders in male rats: possible role of reactive oxygen species

Epidemiological evidence demonstrates positive correlation between environmental and occupational arsenic or fluoride exposure and risk to various cardio-respiratory disorders. Arsenic-exposure has been associated with atherosclerosis, hypertension, cerebrovascular diseases, ischemic heart disease, and peripheral vascular disorders, whereas Fluoride-exposure manifests cardiac irregularities and low blood pressure (BP). Present study aims to study the combined effects of these toxicants on various cardio-respiratory variables in male rats. Single intravenous (i.v.) dose of arsenic (1, 5, 10 mg/kg) or fluoride (5, 10, 20, 36.5 mg/kg) either alone or in combination were administered. Individual exposure to arsenic or fluoride led to a significant depletion of mean arterial pressure, heart rate (HR), respiration rate and neuromuscular (NM) transmission in a dose-dependent manner. These changes were accompanied by increased levels of blood reactive oxygen species (ROS) and decreased glutathione (GSH) concentrations. An increase in the blood acetyl cholinesterase (AChE) activity was observed in both arsenic or fluoride exposed rats. These changes were significantly more pronounced in arsenic-exposed animals than in fluoride. During combined exposure to arsenic (5 mg/kg) + fluoride (20 mg/kg) or arsenic (10 mg/kg) + fluoride (36.5 mg/kg) the toxic effects were more pronounced compared to individual toxicities of arsenic or fluoride alone. However, combined exposure to arsenic (5 mg/kg) + fluoride (36.5 mg/kg) resulted in antagonistic effects on variables suggestive of altered cardio-respiratory function and oxidative stress. The results from the present study suggest that arsenic or fluoride individually demonstrate cardio-respiratory failure at all doses whereas during combination exposure these toxins show variable toxicities; both synergistic and antagonistic effects depending upon the dose. Moreover, it may be concluded that arsenic and/or fluoride cardio-respiratory toxicity may be mediated via oxidative stress. However, these results are new in the discipline thus requires further exploration.

The importance of clinical grading of heart failure and other cardiac toxicities during chemotherapy: updating the common terminology criteria for clinical trial reporting

Although the use of chemotherapy and targeted therapy has improved the clinical benefit, progression-free survival, and overall survival of various cancers in recent years, old and new toxicities have limited their use. To balance the risk with the benefit of treatment, Common Toxicity Criteria and now Common Terminology Criteria for Adverse Events (CTCAE) have been used by the oncology community for more than 20 years to assess toxicity from cancer treatment. This article details the description and grading of cardiac toxicities reported in association with cancer treatment and the use of CTCAE to assess them.

Rat H9c2 cardiac myocytes are sensitive to arsenite due to a modest activation of transcription factor Nrf2

The mechanism underlying the hepatotoxicity induced by arsenic exposure is well investigated. However, little is known about the detailed mechanisms of arsenic-induced cardiotoxicity or cardiac factors involved in high sensitivity to arsenicals in spite of the fact that arsenic trioxide, which is used to treat acute promyelocytic leukemia, causes cardiotoxicity. Here, we show that rat H9c2(2-1) cardiac myocytes exhibit high sensitivity to inorganic arsenite (As(III)) as compared with rat-derived four cell lines (liver epithelial TRL1215 cells, kidney epithelial NRK-52E cells, PC12 phechromocytoma cells and C6 glioma cells). Furthermore, we found a lower steady-state level of glutathione and glutamyl-cysteine ligase (GCL) in H9c2(2-1) cells compared with TRL1215 cells, resulting in an increase in arsenic accumulation. In addition, we detected that the up-regulation of GCL and multi-drug resistance-associated protein (MRP) caused by As(III) was extremely low in H9c2(2-1) cells compared with TRL1215 cells. It is known that Nrf2, which regulates GCL and MRP expression, plays an important role in the protection of cells from arsenicals. We investigated the participation of Nrf2 in the difference of sensitivity to arsenicals between H9c2(2-1) and TRL1215 cells and found that Nrf2 was clearly activated by As(III) exposure in TRL1215 cells but only poorly activated in H9c2(2-1) cells. Considering these results together, we propose that modest activation of Nrf2 during exposure to As(III) in H9c2(2-1) cardiac myocytes leads to reduced ability to metabolize and excrete arsenic.

Regulation of the human CHOP gene promoter by the stress response transcription factor ATF5 via the AARE1 site in human hepatoma HepG2 cells

AIMS

Activating transcription factor (ATF) 5 is a member of the cAMP response element-binding protein (CREB)/ATF family of transcription factors. We have shown that ATF5 is a stress response transcription factor that responds to amino acid limitation, arsenite exposure, or cadmium exposure. In this study we investigated whether ATF5 is involved in the regulation of CCAAT/enhancer-binding protein (C/EBP) homologous protein (CHOP) gene expression.

MAIN METHODS

We used a transient transfection system to express ATF5 and analyzed the regulation of CHOP gene promoter in human hepatoma, HepG2 cells. We also studied the effect of ATF5 knockdown on arsenite-induced CHOP protein expression and arsenite-induced cell death of HepG2 cells.

KEY FINDINGS

We showed that ATF5 activates the CHOP gene promoter in HepG2 cells. Both deletion analysis and point mutations of the promoter revealed that amino acid response element (AARE) 1 is responsible for ATF5-dependent promoter activation. Furthermore, the existence of either AARE1 or activating protein-1 (AP-1) site is sufficient for transcriptional activation of the CHOP gene promoter by arsenite exposure, although complete induction requires the existence of both elements. We also demonstrated that knockdown of ATF5 reduced arsenite-induced CHOP protein expression and arsenite-induced cell death of HepG2 cells.

SIGNIFICANCE

These results suggested that the CHOP gene is a potential target for ATF5, and that ATF5 raises the arsenite-induced CHOP gene expression level via the AARE1 site in HepG2 cells.

How I treat acute promyelocytic leukemia

Acute promyelocytic leukemia is the first malignant disease highly curable with targeted therapy directed at a unique molecular abnormality. The characteristic bleeding diathesis is the most notorious manifestation of the disease, which historically has accounted for a high mortality rate during induction. Acute promyelocytic leukemia is one of the few hematologic diseases that must be recognized under the microscope by the practicing hematologist because early institution of all-trans retinoic acid (ATRA) at the first suspicion of the disease before confirmation of the diagnosis and aggressive blood product support are critical to reduce early mortality. ATRA plus anthracycline-based chemotherapy for induction and consolidation followed by maintenance ATRA with low-dose chemotherapy is currently the standard of care. However, the combination of ATRA and arsenic trioxide, with minimal chemotherapy to control leukocytosis, is very effective therapy for newly diagnosed patients. This combination may replace conventional approaches for most, if not all, patients in the very near future. Acute promyelocytic leukemia should be considered in any patient with newly diagnosed acute myeloid leukemia because the treatment is urgent and different from all other subtypes.

Cardiovascular complications of cancer therapy: incidence, pathogenesis, diagnosis, and management

Cancer treatment today employs a combination of chemotherapy, radiotherapy, and surgery to prolong life and provide cure. However, many of these treatments can cause cardiovascular complications such as heart failure, myocardial ischemia/infarction, hypertension, thromboembolism, and arrhythmias. In this article we review the incidence of cardiotoxicity caused by commonly used chemotherapeutic agents as well as discuss the pathogenesis, diagnosis, management, and prevention of these cardiovascular side effects. Cardiotoxicity related to anticancer treatment is important to recognize as it may have a significant impact on the overall prognosis and survival of cancer patients, and it is likely to remain a significant challenge for both cardiologists and oncologists in the future due to an increasing aging population of patients with cancer and the introduction of many new cancer therapies.

Arsenic trioxide: safety issues and their management

Arsenic trioxide (As2O3) has been used medicinally for thousands of years. Its therapeutic use in leukaemia was described a century ago. Recent rekindling in the interest of As2O3 is due to its high efficacy in acute promyelocytic leukaemia (APL). As2O3 has also been tested clinically in other blood and solid cancers. Most studies have used intravenous As2O3, although an oral As2O3 is equally efficacious. Side effects of As2O3 are usually minor, including skin reactions, gastrointestinal upset, and hepatitis. These respond to symptomatic treatment or temporary drug cessation, and do not compromise subsequent treatment with As2O3. During induction therapy in APL, a leucocytosis may occasionally occur, which can be associated with fluid accumulation and pulmonary infiltration. The condition is similar to the APL differentiation syndrome during treatment with all-trans retinoic acid, and responds to cytoreductive treatment and corticosteroids. Intravenous As2O3 treatment leads to QT prolongation. In the presence of underlying cardiopulmonary diseases or electrolyte disturbances, particularly hypokalaemia and hypomagnesaemia, serious arrhythmias may develop, with torsades du pointes reported in 1% of cases. This may be related to a dose-dependent arsenic-mediated inhibition of potassium ion channels that compromises cardiac repolarization. Because of slow intestinal absorption, oral-As2O3 gives a lower plasma arsenic concentration, which is associated with lesser QT prolongation and hence a more favorable cardiac safety profile. As2O3 does not appear to enter the central nervous system. However, if the blood brain barrier is breached, elemental arsenic may enter the cerebrospinal fluid. As2O3 is predominantly excreted in the kidneys, and dose adjustment is required when renal function is impaired.

PML-RARalpha inhibitors (ATRA, tamibaroten, arsenic troxide) for acute promyelocytic leukemia

Acute promyelocytic leukemia (APL) is characterized by generation of the PML-RARalpha fusion gene. PML-RARalpha can homodimerize with another PML-RARalpha, and the hybrid binds the histone-deacetylase recruiting co-repressor complex with higher affinity than the wild-type RARalpha. However, the co-repressor complex is releasable by pharmacological doses of all-trans retinoic acid (ATRA). More than 90% of patients with APL achieve a complete remission (CR) with differentiation therapy consisting of ATRA combined with chemotherapy. A new synthetic retinoid, tamibaroten, showed therapeutic effectiveness in patients with ATRA-resistant APL with increased expression of cellular retinoic acid binding protein (CRABP), and about 60% of patients with relapsed APL achieved a CR. Arsenic trioxide triggers the rapid degradation of PML-RARalpha through the targeting of the PML moieties of the fusion protein and showed a high CR rate in relapsed APL. The combination of ATRA, chemotherapy, and/or new agents improved the long-term survival in patients with APL.

Single-agent liposomal all-trans retinoic acid can cure some patients with untreated acute promyelocytic leukemia: an update of The University of Texas M. D. Anderson Cancer Center Series

The present study aimed to investigate single-agent liposomal all-trans retinoic acid (Lipo-ATRA) in untreated acute promyelocytic leukemia (APL). Induction therapy consisted of Lipo-ATRA 90 mg/m2 i.v. every other day. Patients in complete remission (CR) continued to receive Lipo-ATRA 90 mg/m2 i.v. three times a week for 9 months. Idarubicin was added only if a polymerase chain reaction test for promyelocytic leukemia-retinoic acid receptor alpha (sensitivity level, 10(-4)), performed every 3 months from CR, was positive. The results were compared with those of a historical control group treated with oral ATRA and idarubicin. Lipo-ATRA induced CR in 79% of patients; CR rates were 92% and 38% in patients with white blood cell (WBC) counts <10 x 10(9)/L and >10 x 10(9)/L, respectively. Ten of the 26 responders to Lipo-ATRA remain in first CR at a median of 6.4 years, despite never receiving idarubicin; all 10 had initial WBC counts <10 x 10(9)/L. The 5-year survival rate was 76% for patients treated with Lipo-ATRA. Comparisons with oral ATRA+idarubicin as given at M. D. Anderson are confounded because of their historical nature and the absence of ATRA from post-remission therapy in the former group. Nonetheless, a multivariate Cox model identified higher WBC counts and older age, but not treatment (historical vs. Lipo-ATRA), as being predictive of shorter relapse-free and overall survival. Lipo-ATRA can cure patients presenting with WBC counts <10 x 10(9)/L (low risk) without additional therapy, contrary to conventional ATRA, which, when given alone, probably cures no patients. The observation that patients can be cured of APL without the use of chemotherapy should encourage further study of 'targeted' therapy in APL and in other leukemias.

Chronic arsenic exposure and cardiac repolarization abnormalities with QT interval prolongation in a population-based study

BACKGROUND

Chronic arsenic exposure is associated with cardiovascular abnormalities. Prolongation of the QT (time between initial deflection of QRS complex to the end of T wave) interval and profound repolarization changes on electrocardiogram (ECG) have been reported in patients with acute promyelocytic leukemia treated with arsenic trioxide. This acquired form of long QT syndrome can result in life-threatening arrhythmias.

OBJECTIVE

The objective of this study was to assess the cardiac effects of arsenic by investigating QT interval alterations in a human population chronically exposed to arsenic.

METHODS

Residents in Ba Men, Inner Mongolia, have been chronically exposed to arsenic via consumption of water from artesian wells. A total of 313 Ba Men residents with the mean arsenic exposure of 15 years were divided into three arsenic exposure groups: low (< or = 21 microg/L), medium (100-300 microg/L), and high (430-690 microg/L). ECGs were obtained on all study subjects. The normal range for QTc (corrected QT) interval is 0.33-0.44 sec, and QTc > or = 0.45 sec was considered to be prolonged.

RESULTS

The prevalence rates of QT prolongation and water arsenic concentrations showed a dose-dependent relationship (p = 0.001). The prevalence rates of QTc prolongation were 3.9, 11.1, 20.6% for low, medium, and high arsenic exposure, respectively. QTc prolongation was also associated with sex (p < 0.0001) but not age (p = 0.486) or smoking (p = 0.1018). Females were more susceptible to QT prolongation than males.

CONCLUSIONS

We found significant association between chronic arsenic exposure and QT interval prolongation in a human population. QT interval may potentially be useful in the detection of early cardiac arsenic toxicity.

Treatment of relapsed or refractory acute promyelocytic leukemia

Current treatment for acute promyelocytic leukemia (APL) usually includes an induction phase with all-trans retinoic acid (ATRA) and anthracycline-based chemotherapy, followed by a consolidation phase of anthracycline-based chemotherapy and maintenance therapy with ATRA with or without low-dose chemotherapy for 1-2 years. This treatment strategy results in a high complete remission (CR) rate of about 90% and an overall survival rate of 80%. About 5%-30% of patients relapse, mainly patients with high-risk APL. Relapse at extramedullary sites, which occurs in approximately 3%-5% of patients, is emerging as a new issue. Treatment of relapsed/advanced APL includes the use of arsenic trioxide (ATO), gemtuzumab ozogamicin, and hematopoietic stem cell transplantation. ATO is currently the most effective therapeutic agent in relapsed APL. Hematopoietic stem cell transplantation is becoming a common strategy after achieving remission with ATO. Autologous transplant appears to have a more favorable outcome than allogeneic transplant in this setting, particularly when carried out during second remission, primarily because of significantly higher treatment-related mortality with allogeneic transplants. Allogeneic transplant, however, should be strongly considered for patients who remain molecularly positive. Future directions for APL therapy should include developing agents that can prevent relapse, particularly for high-risk patients. Other future treatment strategies may include use of ATO administered concomitantly or sequentially with chemotherapy, gemtuzumab or FLT-3 inhibitors that may obviate the need for autologous transplantation, and posttransplant maintenance perhaps with FLT-3 inhibitors.

Optimizing treatment for elderly patients with acute promyelocytic leukemia: is it time to replace chemotherapy with all-trans retinoic acid and arsenic trioxide?

This review focuses on the treatment of acute promyelocytic leukemia (APL) in elderly patients and offers recommendations for improving outcomes. Nineteen percent of patients with APL are > or =60 years. Rates of response and survival are lower in elderly compared with younger patients, owing to a higher incidence of early deaths or deaths in remission. However, relapse-free survival rates are similar in both groups. Ongoing trials assess the role of reduced-intensity regimens. All-trans retinoic acid (ATRA) and concurrent arsenic trioxide is associated with high rates of response and molecular remission and low rates of induction deaths. We propose this combination as the treatment of choice in patients with APL, including the elderly. Patients with elevated leukocyte counts may also benefit from gemtuzumab ozogamicin therapy, with or without leukapheresis. Monitoring major organ function and toxicity is essential. Patients should be assessed for minimal residual disease using polymerase chain reaction testing for promyelocytic leukemia-retinoic acid receptor alpha. If molecular relapse is evident, treatment with ATRA and idarubicin, with or without gemtuzumab ozogamicin, is recommended.