Kensuke Naito

Prolongation of the QT interval and ventricular tachycardia in patients treated with arsenic trioxide for acute promyelocytic leukemia.

Arsenic trioxide therapy has recently been found to be very effective in relapsed or refractory acute promyelocytic leukemia. It has resulted in complete remission in more than 52% of cases in China and the United States (1, 2). Shen and colleagues (1) have given the most detailed report of adverse events related to arsenic trioxide therapy. Although most of the patients in their study were critically ill, arsenic trioxide was relatively well tolerated. Updated analyses showed that nonlife-threatening cardiac toxicities related to arsenic trioxide occurred in 8 of 47 patients (3). Electrocardiographic abnormalities, such as QRS complex broadening, prolonged QT intervals, ST-segment depression, T-wave flattening, and multifocal ventricular tachycardia, have been reported in acute arsenic poisoning (4-6). Recently, Huang and colleagues (7) found that 1 patient developed complete atrioventricular block during arsenic trioxide therapy and required implantation of a permanent pacemaker. After observing a prolonged QT interval in the first patient with relapsed acute promyelocytic leukemia who received arsenic trioxide in our hospital, we used continuous monitoring to prospectively examine electrocardiograms and echocardiograms and determine the cardiac toxicities of arsenic trioxide in 8 patients with this disease. We observed prolonged QT intervals in all 8 patients and serious arrhythmias in 4 patients. Methods We used arsenic trioxide to treat 8 patients with acute promyelocytic leukemia who had relapse after extensive previous therapy with all-trans retinoic acid and chemotherapy, including anthracycline (Table). Arsenic trioxide was provided by PolaRx Biopharmaceuticals, Inc. (New York, New York). Our protocol, which was the same as that of a phase II study in the United States, was reviewed and approved by the institutional review board of Hamamatsu University School of Medicine in Hamamatsu, Japan. All patients gave written informed consent and were hospitalized while receiving arsenic trioxide (0.15 mg/kg of body weight), which was administered daily by 2-hour infusion for a maximum of 60 days. Treatment was discontinued if patients met conventional criteria for complete remission (cellular bone marrow aspirate with blasts 5%, absolute neutrophil count 1.5 109 cells/L, and platelet count 100 109 cells/L). Patients who achieved complete remission received one additional 25-day course of arsenic trioxide at the same dose between 3 and 6 weeks after induction therapy. Patients were continuously monitored with ambulatory electrocardiography while receiving arsenic trioxide, and standard 12-lead electrocardiography was performed at least once per week. The QT intervals were calculated in the weekly electrocardiograms, were expressed as the mean values in the 12-lead electrocardiograms, and were corrected by heart rates according to the Bazett formula (QTc interval=QT interval/R-R interval) (8). Table. Patient Characteristics and Prolongation of the QTc Interval during Arsenic Trioxide Therapy The funding source had no role in the collection, analysis, or interpretation of the data or in the decision to submit the paper for publication. Results Five patients (63%) achieved complete remission, and 4 patients received the second course of arsenic trioxide as consolidation therapy. Long QTc intervals (>440 ms) had been noted in 4 of 8 patients before arsenic trioxide therapy. Prolonged QT intervals were observed in all patients during induction therapy with arsenic trioxide and in 3 of 4 patients during the second course of therapy after complete remission (Table). The PQ interval and QRS duration were not prolonged in any case. Ventricular premature contractions were seen during 8 of 12 courses of therapy. Four patients developed nonsustained monomorphic ventricular tachycardia ( 3 successive ventricular premature contractions that stopped spontaneously within 30 seconds) and received antiarrhythmic agents (mexiletine HCl and lidocaine HCl). No patients developed sustained ventricular tachycardia or polymorphic ventricular tachycardia. Patient 1 received arsenic trioxide therapy during his second relapse. The QTc interval was prolonged gradually until day 33 and reverted to the pretreatment level after arsenic trioxide was stopped on day 43. The patient had seven successive ventricular premature contractions on day 25 when the QTc interval was 474 milliseconds (Figure). Therefore, mexiletine HCl (150 mg/d) was administered from day 28 to day 148 during arsenic trioxide therapy. The second course of arsenic trioxide with prophylactic mexiletine HCl was started on day 114. Although similar prolonged QT intervals were seen, only isolated ventricular premature contractions, not ventricular tachycardia, were induced. Patient 3 received arsenic trioxide for 46 days as induction therapy during her second relapse. She had five successive ventricular premature contractions on day 5 and three on day 31. She was given amphotericin B and received potassium and calcium supplements because she had low-normal levels of serum potassium and calcium on day 5. The QTc interval was prolonged from 408 to 460 milliseconds until day 50 and decreased to 442 milliseconds on day 87, when the second course was started. The second course again caused a prolonged QT interval. Figure. Electrocardiographic tracing and QT intervals in patient 1 during arsenic trioxide therapy. Patient 6 had two acute myocardial infarctions before developing acute promyelocytic leukemia. He relapsed four times and received large doses of chemotherapy before receiving arsenic trioxide. The ejection fraction was low (0.45) before arsenic trioxide therapy began. The patient had been receiving mexiletine HCl, 300 mg/d, since his second myocardial infarction. On day 38, nonsustained ventricular tachycardia (27 successive beats) was noticed when the QTc interval was prolonged from 443 to 485 milliseconds. Arsenic trioxide was reduced to 0.1 mg/kg per day and was administered intermittently until day 92 with lidocaine HCl or verapamil HCl. However, the patient developed accelerated idioventricular rhythm on day 62 and nonsustained ventricular tachycardia on day 70. He did not achieve complete remission, and arsenic trioxide therapy was discontinued on day 92. Patient 7 had nonsustained ventricular tachycardia before arsenic trioxide therapy in her second relapse, and mexiletine HCl, 150 mg/d, was given prophylactically until day 54. Arsenic trioxide was not effective and was withdrawn on day 40. The QTc interval was prolonged from 448 to 479 milliseconds; however, no serious arrhythmias were induced. Patient 8, who had a second relapse, had four successive ventricular premature contractions on day 23 and day 24 when the QTc interval was 461 milliseconds. Arsenic trioxide was withdrawn on day 23, and mexiletine HCl, 300 mg/d, was given. Thereafter, no ventricular tachycardia developed and arsenic trioxide therapy was restarted on day 26. Complete remission occurred, and arsenic trioxide therapy was stopped on day 41. No patient developed echocardiographic abnormalities (such as contractile dysfunction, cardiac enlargement, or hypertrophy) except the patient with previous myocardial infarctions. Serum electrolyte levels were within normal limits in all patients during the study. Discussion We used continuous monitoring by ambulatory electrocardiography to show prolonged QT intervals in 8 patients receiving arsenic trioxide. Ventricular arrhythmias, including ventricular tachycardia, developed in 5 of 12 courses of therapy and were associated with prolonged QT intervals. Previous reports of cardiographic abnormalities in arsenic trioxide therapy have shown low-flat T-wave, sinus tachycardia, prolonged QT intervals, and atrioventricular blocks, but not ventricular arrhythmias (1, 2, 7). However, multifocal ventricular tachycardia and ventricular fibrillation have been reported in arsenic poisoning (4-6). The tachyarrhythmias in our study were not sustained ventricular tachycardia or torsade de pointes but nonsustained ventricular tachycardia, accelerated idioventricular rhythm, or paroxysmal supraventricular tachycardia. It is unknown why polymorphic ventricular tachycardias and torsade de pointes were not observed. We believe that spatial inhomogeneity (QT dispersion) or abnormal ventricular repolarization might also be related to the arrhythmias. Indeed, in some cases, prolonged QT intervals were accompanied by an increase in the QT dispersion with no change in the QRS duration. It remains unclear why arsenic prolongs the QT interval. The metal is known to affect the peripheral nervous system diffusely (9), and imbalance of the sympathetic nervous system may be involved. Arsenic also causes widespread damage in many organs by combining with sulfhydryl proteins (9). A direct effect of arsenic on the myocardium could also be involved. However, the evidence remains speculative and further study is needed. Because of its remarkable effectiveness, arsenic trioxide will continue to be widely used for relapsed or refractory acute promyelocytic leukemia. Since such patients have been heavily treated with chemotherapeutic agents, including anthracycline and all-trans retinoic acid, cardiac damage is likely to be universal before arsenic trioxide therapy begins. Arsenic trioxide thus might induce arrhythmia. In our study, although the number of patients was small, ventricular arrhythmias were observed, often through careful monitoring. Therefore, we believe that patients taking arsenic trioxide should have frequent electrocardiographic monitoring and, in particular, should be monitored carefully for serious arrhythmias when QT intervals are prolonged. Prophylactic antiarrhythmic drugs that do not prolong the QT interval should be used because previous reports showed an association between fatal ventricular tachycardias and prolonged QT intervals in arsenic intoxication (4-6). Elect

The induction of apoptosis and cell cycle arrest by arsenic trioxide in lymphoid neoplasms.

Arsenic trioxide (As2O3) has recently been shown to induce complete remission in acute promyelocytic leukemia (APL). As2O3 reportedly has dose-dependent dual effects on APL cells, triggering apoptosis at relatively high concentrations and inducing differentiation at lower concentrations. However, its effect is still controversial for other AML cells and hematological neoplasms. We studied the in vitro effect of As2O3 on lymphoid lineage cells: lymphoma cell lines, NOL-3, Raji and Daudi, a myeloma cell line, NOP-1, normal peripheral blood lymphocytes (PBL), non-Hodgkins lymphoma (NHL) cells and chronic lymphocytic leukemia (CLL) cells, and compared it with the effect on APL cell line, NB4, as well as other myeloid cell lines, HL-60 and NKM-1. As2O3 at a concentration of 1 μmol/l markedly inhibited both proliferation and viability of NB4, NOP-1, NOL-3 and NKM-1 cells, but it reduced only viability in normal PBL, CLL cells and NHL cells. As2O3 induced apoptosis and down-regulated bcl-2 expression in NB4, NOP-1 and NKM-1 cells. On the other hand, in HL-60, Raji and Daudi cells, 1 μmol/l As2O3 inhibited only the proliferation weakly, and neither induced apoptosis nor down-regulated bcl-2 expression, but arrested only cell cycle at G1 phase. As2O3 at a low concentration of 0.1 μmol/l had no effect on proliferation and viability of these cells except for NB4. These results showed that As2O3 exerted variable and definite effects on lymphoid cells and indicated that As2O3 might be clinically useful in lymphoid neoplasms such as malignant lymphoma and CLL.

Clinicopathological and prognostic characteristics of CD56‐negative multiple myeloma

Summary. We analysed CD56 expression in 70 patients with multiple myeloma (MM) to determine its clinicopathological and prognostic significance. Fifty‐five (79%) patients were CD56+. CD56– patients (n = 15) had higher β2 microglobulin levels and a higher incidence of extramedullary disease, Bence Jones protein, renal insufficiency and thrombocytopenia than CD56+ patients. Their myelomas more frequently had a plasmablastic morphology. Overall survival was significantly lower in CD56– than CD56+ patients (22 vs 63 months, P = 0·0002). We conclude that CD56– MM is a discrete entity associated with more aggressive disease. The higher incidence of plasmablastic cases suggested that CD56– MM may develop from a less mature plasma cell than CD56+ MM.

Arsenic trioxide therapy in relapsed or refractory Japanese patients with acute promyelocytic leukemia: updated outcomes of the phase II study and postremission therapies.

Recently, arsenic trioxide (ATO) has been proved to induce complete remission (CR) at a high rate in patients with acute promyelocytic leukemia (APL).We prospectively investigated the safety and efficacy of ATO therapy in patients with relapsed and refractory APL and examined the duration of CR and the postremission therapies. Initially, 0.15 mg/kg ATO was administered until bone marrow remission to a maximum of 60 days. After the patient achieved CR, 1 additional ATO course at the same dosage was administered for 25 days. Of 34 patients, 31 (91%) achieved CR. PML-RARα messenger RNA was not detected in the bone marrow of 18 (72%) of the 25 patients evaluated by reverse transcriptase—polymerase chain reaction analysis. At a median follow-up of 30 months, the estimated 2-year overall survival rate was 56%, and the estimated 2-year event-free survival rate was 17%. During the ATO therapy, QTc prolongation was observed in most cases. Fifteen patients developed ventricular tachycardia, and 1 of them showed torsades de pointes. Other adverse events were nausea, water retention, APL differentiation syndrome, skin eruption, liver dysfunction, and peripheral neuropathy, all of which were quite tolerable. ATO therapy was remarkably effective for relapsed APL; however, postremission therapies were necessary to maintain a durable remission.

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

Recent studies have shown that arsenic trioxide (As2O3) can induce complete remission in patients with acute promyelocytic leukemia (APL). We tested the efficacy and safety of As2O3 for the treatment of patients with APL who had relapsed from or become refractory to all-trans retinoic acid (ATRA) and conventional chemotherapy in a prospective study. As2O3 at a dose of 0.15 mg/kg was administered until the date of bone marrow remission to a maximum of 60 days. In patients who achieved complete remission (CR), one additional course of As2O3 was administered using the same dose for 25 days. Of 14 patients, 11 (78%) achieved CR. Six of 10 patients who achieved CR showed disappearance of PML-RARα transcript by RT-PCR assay. The duration of As2O3-induced CR ranged from 4 to 22 months (median, 8 months) at a median follow-up of 17 months. Adverse events included 13 electrocardiogram abnormalities (13 QTc prolongation, eight ventricular premature contraction, four nonsustained ventricular tachycardia and two paroxysmal supraventricular tachycardia), seven nausea and vomiting, four pruritus, three peripheral neuropathy, three fluid retention and one APL differentiation syndrome. Four patients received antiarrhythmic agents. Hyperleukocytosis developed in five patients and in three cytotoxic drugs were necessary. Other adverse events were relatively mild. As2O3 treatment is effective and relatively safe in relapsed or refectory patients with APL. Cardiac toxicities in patients with QTc prolongation should be carefully monitored.

Reduced effect of gemtuzumab ozogamicin (CMA-676) on P-glycoprotein and/or CD34-positive leukemia cells and its restoration by multidrug resistance modifiers

Gemtuzumab ozogamicin (CMA-676), a calicheamicin-conjugated humanized anti-CD33 mouse monoclonal antibody, has recently been introduced clinically as a promising drug for the treatment of patients with acute myeloid leukemia (AML), more than 90% of which express CD33 antigen. However, our recent study suggested that CMA-676 was excreted by a multi- drug-resistance (MDR) mechanism in P-glycoprotein (P-gp)-expressing leukemia cell lines. We analyzed the in vitro effects of CMA-676 on leukemia cells from 27 AML patients in relation to the amount of P-gp, MDR-associated protein 1 (MRP1), CD33 and CD34, using a multi-laser-equipped flow cytometer. The cytocidal effect of CMA-676, estimated by the amount of hypodiploid portion on cell cycle, was inversely related to the amount of P-gp estimated by MRK16 monoclonal antibody (P = 0.004), and to the P-gp function assessed by intracellular rhodamine-123 accumulation in the presence of PSC833 or MS209 as a MDR modifier (P = 0.0004 and P = 0.002, respectively). In addition, these MDR modifiers reversed CMA-676 resistance in P-gp-expressing CD33+ leukemia cells (P = 0.001 with PSC833 and P = 0.0007 with MS209). In CD33+ AML cells from 13 patients, CMA-676 was less effective on CD33+CD34+ than CD33+CD34− cells (P = 0.002). PSC833 partially restored the effect of CMA-676 in CD33+CD34+ cells. These results suggest that the combined use of CMA-676 and a MDR modifier will be more effective on CD33+ AML with P-gp-related MDR.

Efficacy of gemtuzumab ozogamicin on ATRA- and arsenic-resistant acute promyelocytic leukemia (APL) cells

Acute promyelocytic leukemia (APL) cells express a considerable level of CD33, which is a target of gemtuzumab ozogamicin (GO), and a significantly lower level of P-glycoprotein (P-gp). In this study, we examined whether GO was effective on all-trans retinoic acid (ATRA)- or arsenic trioxide (ATO)-resistant APL cells. Cells used were an APL cell line in which P-gp was undetectable (NB4), ATRA-resistant NB4 (NB4/RA), NB4 and NB4/RA that had been transfected with MDR-1 cDNA (NB4/MDR and NB4/RA/MDR, respectively), ATO-resistant NB4 (NB4/As) and blast cells from eight patients with clinically ATRA-resistant APL including two patients with ATRA- and ATO-resistant APL. The efficacy of GO was analyzed by 3H-thymidine incorporation, the dye exclusion test and cell cycle distribution. GO suppressed the growth of NB4, NB4/RA and NB4/As cells in a dose-dependent manner. GO increased the percentage of hypodiploid cells significantly in NB4, NB4/RA and NB4/As cells, and by a limited degree in NB4/MDR and NB4/RA/MDR cells. Similar results were obtained using blast cells from the patients with APL. GO is effective against ATRA- or ATO-resistant APL cells that do not express P-gp, and the mechanism of resistance to GO is not related to the mechanism of resistance to ATRA or ATO in APL cells.

Disease-related potential of mutations in transcriptional cofactors CREB-binding protein and p300 in leukemias.

CREB-binding protein (CBP) and highly related p300 protein are transcriptional co-activators that play an essential role in chromatin remodeling through histone acetyltransferase activity and interaction with other transcriptional regulators. In this study, various hematological malignancies, including nine cell lines and 45 clinical samples (32 acute myeloid leukemias (AML), nine acute lymphoblastic leukemias (ALL), two cases of myelodysplastic syndrome (MDS), one multiple myeloma, and one chronic myelogenous leukemia in blast crisis), were examined to ask whether mutation of the CBP and p300 genes could be involved in leukemogenesis. The answer was approached by employing the reverse transcription-polymerase chain reaction and single-strand conformation polymorphism (RT-PCR/SSCP) technique and subsequent sequence analysis. A T-lymphoblastic cell line, CEM had an in-frame 21-base-pair deletion within the bromodomain of its p300 cDNA. Genomic DNA analysis revealed aberrant splicing caused by mutation of the acceptor site of intron 17 from ag to gg, which should interfere with catalytic step II of the pre-mRNA splicing reaction. In 1 MDS patient, a missense mutation was detected, which caused a replacement from Ser to Gly at codon 507 of p300. This is the first report of CBP/p300 mutations in leukemias, which might be relatively rare but nonetheless contribute to pathogenesis in some fraction of cases.

Role of P-glycoprotein in all-trans retinoic acid (ATRA) resistance in acute promyelocytic leukaemia cells: analysis of intracellular concentration of ATRA

We analysed the relationship between all‐trans retinoic acid (ATRA) resistance and P‐glycoprotein (P‐gp)‐associated multidrug resistance (MDR) in acute promyelocytic leukaemia (APL). There was no difference in the intracellular ATRA accumulation between NB4 cells and an MDR1 cDNA‐transduced NB4 subline and between ATRA‐resistant NB4 cells (NB4/RA) and an MDR1 cDNA‐transduced NB4/RA subline. PSC833, a MDR modifier, did not increase the intracellular accumulation of ATRA or affect the expression of CD11b, the nitroblue tetrazolium (NBT) reduction activity, the proportion of apoptotic cells or the morphology of these four ATRA‐treated cell lines. Similar results were obtained in the analysis of APL cells from five patients relapsed after ATRA‐induced complete remission.

Two cases of acute promyelocytic leukemia complicated by torsade de pointes during arsenic trioxide therapy

We describe 2 patients with acute promyelocytic leukemia (APL) in whom torsade de pointes (TdP) developed during treatment with arsenic trioxide. Patient 1 was a 23-year-old woman with second-relapse APL. Ventricular premature beat bigeminy developed on day 27 of treatment, and episodes of TdP developed on day 28. Patient 2 was a 51-year-old woman with second-relapse APL who had cardiomyopathy due to prior anthracycline treatment. TdP developed on day 17 of treatment. Arsenic trioxide is known to cause electrocardiographic abnormalities, such as ventricular tachycardia and prolongation of QT interval. Patient 1 was given fluconazole as a concomitant drug. Patient 2 had cardiomyopathy and hypokalemia. Careful management is needed during arsenic trioxide therapy because this treatment prolongs the QT interval, possibly inducing episodes of TdP.