In vitro evaluation of the reductive carbonyl idarubicin metabolism to evaluate inhibitors of the formation of cardiotoxic idarubicinol via carbonyl and aldo-keto reductases

The most important dose-limiting factor of the anthracycline idarubicin is the high risk of cardiotoxicity, in which the secondary alcohol metabolite idarubicinol plays an important role. It is not yet clear which enzymes are most important for the formation of idarubicinol and which inhibitors might be suitable to suppress this metabolic step and thus would be promising concomitant drugs to reduce idarubicin-associated cardiotoxicity. We, therefore, established and validated a mass spectrometry method for intracellular quantification of idarubicin and idarubicinol and investigated idarubicinol formation in different cell lines and its inhibition by known inhibitors of the aldo-keto reductases AKR1A1, AKR1B1, and AKR1C3 and the carbonyl reductases CBR1/3. The enzyme expression pattern differed among the cell lines with dominant expression of CBR1/3 in HEK293 and MCF-7 and very high expression of AKR1C3 in HepG2 cells. In HEK293 and MCF-7 cells, menadione was the most potent inhibitor (IC50 = 1.6 and 9.8 µM), while in HepG2 cells, ranirestat was most potent (IC50 = 0.4 µM), suggesting that ranirestat is not a selective AKR1B1 inhibitor, but also an AKR1C3 inhibitor. Over-expression of AKR1C3 verified the importance of AKR1C3 for idarubicinol formation and showed that ranirestat is also a potent inhibitor of this enzyme. Taken together, our study underlines the importance of AKR1C3 and CBR1 for the reduction of idarubicin and identifies potent inhibitors of metabolic formation of the cardiotoxic idarubicinol, which should now be tested in vivo to evaluate whether such combinations can increase the cardiac safety of idarubicin therapies while preserving its efficacy.

DNA-PKcs-dependent NHEJ pathway supports the progression of topoisomerase II poison-induced chromosome aberrant cells

The role of DNA double strand break (DSB) repair pathways, non-homologous end joining (NHEJ), and homologous recombination (HR) was evaluated to prevent the chromosome instability induced by the topoisomerase II (Top2) poisons, idarubicin, and etoposide in Chinese hamster cell lines. XR-C1 (DNA-PKcs deficient) and V-C8 (BRCA2 deficient) showed higher sensitivity to increased concentrations of Top2 poisons compared with their normal counterparts, CHO9 and V79. Both proficient and deficient cells exhibited a marked DSB induction in all phases of the cell cycle. Additionally, deficient cells showed persistent DNA damage 24 hr post-treatment. Chromosomal aberrations increased in the first mitosis following Top2 poison-treatments in G1 or G2 in proficient and deficient cells. CHO9 and V79 demonstrated chromosome and chromatid exchanges following treatments in G1 and G2 phases, respectively. Deficient cells showed high frequencies of chromatid exchanges following treatments in G1 and G2. Simultaneously, we analyzed the micronuclei (MN) induction in interphase cells after treatments in G1, S, or G2 of the previous cell cycle. Both Top2 poisons induced an important increase in MN in CHO9, V79, and V-C8 cells. XR-C1 exhibited an increased MN frequency when cells were treated in G1 phase but not in S or G2. This MN reduction was due to a cell accumulation at G2/M and death in G2-treated cells. Our data suggest that NHEJ and HR operate differentially throughout the cell cycle to protect from Top2 poison-induced chromosome instability, and that DNA-PKcs-dependent NHEJ pathway allows the survival of chromosome damaged cells during S/G2 to the next interphase.

Comparative aneugenicity of doxorubicin and its derivative idarubicin using fluorescence in situ hybridization techniques

The present study was designed to evaluate and compare the aneugenicity of idarubicin and doxorubicin, topoisomerase-targeting anticancer anthracyclines, using fluorescence in situ hybridization techniques. It was found that idarubicin and doxorubicin treatment (12 mg/kg) induced sperm meiotic delay of 24h. To determine the frequencies of disomic and diploid sperm, groups of 5 male Swiss albino mice were treated with 3, 6 and 12 mg/kg idarubicin or doxorubicin. Significant increases in the frequencies of disomic and diploid sperm were caused by treatment with all doses of idarubicin and the two highest doses of doxorubicin compared with the controls. Moreover, both compounds significantly increased the frequency of diploid sperm, indicating that complete meiotic arrest occurred. The observation that XX- and YY-sperm significantly prevailed XY-sperm indicates missegregation during the second meiotic division. The results suggest also that earlier prophase stages contribute relatively less to idarubicin and doxorubicin-induced aneuploidy. Effects of the same doses were investigated by the bone-marrow micronucleus test. Significant increases in the frequencies of micronuclei were found after treatment with all doses of both compounds. The responses were also directly correlated with bone marrow suppression. Idarubicin was more toxic than doxorubicin. Exposure to 12 mg/kg of idarubicin and doxorubicin yielded 3.82 and 2.64% micronuclei, respectively, and of these an average of 58.3 and 62.8%, respectively, showed centromeric signals, indicating their formation by whole chromosomes and reflecting the aneugenic activity of both compounds. Correspondingly, about 41.7 and 37.2% of the induced micronuclei, respectively, were centromere-negative, demonstrating that both compounds not only induce chromosome loss but also DNA strand breaks. Based on our data, aneuploidy assays such as sperm-fluorescence in situ hybridization assay and micronucleus test complemented by fluorescence in situ hybridization with centromeric DNA probes have been to some extent validated to be recommended for the assessment of aneuploidogenic effects of chemicals.

Evaluation of the protective effects of quercetin, rutin, naringenin, resveratrol and trolox against idarubicin-induced DNA damage

PURPOSE

Idarubicin is a synthetic anthracycline anticancer drug widely used in the treatment of some hematological malignancies. The studies in our laboratory have clearly demonstrated that idarubicin can undergo reductive bioactivation by NADPH-cytochrome P450 reductase to free radicals with resulting formation of DNA strand breaks, which can potentially contribute to its genotoxic effects [Celik, H., Arinç, E., Bioreduction of idarubicin and formation of ROS responsible for DNA cleavage by NADPH-cytochrome P450 reductase and its potential role in the antitumor effect. J Pharm Pharm Sci, 11(4):68-82, 2008]. In the current study, our aim was to investigate the possible protective effects of several phenolic antioxidants, quercetin, rutin, naringenin, resveratrol and trolox, against the DNA-damaging effect of idarubicin originating from its P450 reductase-catalyzed bioactivation.

METHODS

DNA damage was measured by detecting single-strand breaks in plasmid pBR322 DNA using a cell-free agarose gel method.

RESULTS

Our results indicated that, among the compounds tested, quercetin was the most potent antioxidant in preventing DNA damage. Quercetin significantly decreased the extent of DNA strand breaks in a dose-dependent manner; 100 microM of quercetin almost completely inhibited the DNA strand breakage. Unlike quercetin, its glycosidated conjugate rutin, failed to provide any significant protection against idarubicin-induced DNA strand breaks except at the highest concentration tested (2 mM). The protective effects of other antioxidants were significantly less than that of quercetin even at high concentrations. Quercetin was found to be also an effective protector against DNA damage induced by mitomycin C.

CONCLUSION

We conclude that quercetin, one of the most abundant flavonoids in the human diet, is highly effective in reducing the DNA damage caused by the antitumor agents, idarubicin and mitomycin C, following bioactivation by P450 reductase.

Chromosomal aberration and micronucleus studies of two topoisomerase (II) targeting anthracyclines

Anthracycline antibiotics are widely used in cancer chemotherapy. Doxorubicin and Idarubicin, topoisomerase-targeting anthracyclines, were examined for their effect on chromosomal aberration and micronucleus induction in cultured human lymphocytes employing lymphocyte transformation test and cytokinesis-blocked micronucleus (CBMN) assay. A statistically significant dose-dependent increase in micronucleus frequency (p < 0.001) in binucleated cells was seen as well as a significant increase in chromosomal aberration frequency was also observed for both the drugs. A variety of aberrations were scored including terminal deletions, breaks, gaps, exchanges, fragment formation, ends rejoining, interstitial deletions etc. Nuclear division index was also calculated and showed a cell cycle delay towards higher doses. A number of necrotic and apoptotic cells were also observed at higher concentrations. This confirms the two drugs to be clastogenic and aneugenic.

Repair of idarubicin-induced DNA damage: A cause of resistance?

Idarubicin, a widely used anticancer drug inhibits topoisomerase (topo) IIalpha and induces DNA double strand breaks. The finding that idarubicin-induced DNA damage is repaired before cell death is initiated encouraged us to examine the role of DNA repair for the cytotoxicity of idarubicin in human promyelocytic HL60 leukaemia cells. We found that DNA double strand breaks induced by a 90 min transient exposure to 0.5 microgml(-1) idarubicin were rapidly repaired throughout the whole population, while topo IIalpha itself was degraded. In spite of DNA repair, the vast majority of cells died within 40 h. Using differential staining of the chromatids and microscopic evaluation of DNA break points, we found evidence for a high number of false ligations of loose DNA strands arising from the inhibition of topo IIalpha action by idarubicin. If mainly actively transcribed genes are affected, this results in a disruption of vital genetic information, of regulatory sequences and, ultimately, in induction of the cell death pathway. Our results confirm the hypothesis that misrepair of DNA damage is a decisive event in idarubicin-induced cell death. They are discussed in the context of topo IIalpha-function and the currently known mechanisms of DNA double strand break repair.

Preclinical assessment of anthracycline cardiotoxicity in laboratory animals: predictiveness and pitfalls

Doxorubicin is one of the most prescribed anticancer drugs, due to its important activity in hematological malignancies as in solid tumors. However, its important cardiac toxicity still limits its long-term use and prevents from reaching optimal benefits. Numerous ways have been proposed to avoid cardiac toxicity, such as protracted infusions or special formulations, development of less cardiotoxic analogues and of cardioprotectors. There is a need for preclinical models able to screen rapidly these various approaches and to provide rational bases for clinical trials. The first model is the long-term rabbit model. Weanling rabbits given weekly injections of doxorubicin for 4 months developed a cardiomyopathy which was obvious from a clinical (cardiac failure) and from a pathological point of view. This model has been widely used afterwards for the discovery of cardioprotective molecules. Models in other animals such as rats or mice were similarly implemented, also with long-term exposures to the drug, resulting in cardiac failure and severe pathological alterations which could be graded for comparison. Starting from the evidence that the damage caused by anthracyclines on cardiomyocytes was immediate after each injection and that the functional efficiency of the myocardium should be affected by the anthracyclines long before the morphological alterations become detectable, we developed a short-term model studying the cardiac performances of isolated perfused hearts of rats that had been treated within 12 days by repetitive administrations of the molecule(s) to be tested. This model appeared easy to implement and provided the data expected from clinical experience: epirubicin appeared less cardiotoxic than doxorubicin; liposomal formulations appeared less cardiotoxic than free drug formulations; dexrazoxane strongly protected against doxorubicin cardiotoxicity. We were then to show that paclitaxel could potentiate doxorubicin cardiotoxicity, but that docetaxel did not so; or that a high dose of dexrazoxane brought significantly higher protection than a conventional dose. Based upon these various contributions, we can encourage the use of the short-term model of isolated perfused rat heart to screen the preclinical cardiotoxicity of anthracycline molecules, formulations and combinations.

Multidrug reverting activity toward leukemia cells in a group of new verapamil analogues with low cardiovascular activity

The development of refractory disease is often associated with the overexpression of multidrug resistance (MDR) proteins, especially in several hematological malignancies, such as acute myeloid leukemias (AML), multiple myeloma (MM) and non-Hodgkin's lymphomas (NHL). Since the recognition of these proteins, several attempts have been made to modulate their expression and activity (protein kinase C inhibitors, anti-MDR-1 oligonucleotides, pharmacological competitors and transcriptional inhibitors). Six new compounds (MM 36, CTS 4, CTS 9, CTS 12, CTS 27 and CTS 41), derived from verapamil (VRP), were designed and synthesized to improve their MDR-reverting activity and reduce cardiovascular effects. Cytotoxicity (WST-1 methods) and functional (calcein-acetoxymethyl (Calcein-AM)) assays were performed on a resistant cell line K-562/doxR and on the mononuclear cells (MNCs) of patients with AML. Furthermore, the six molecules were tested for their vasodilator, inotropic and chronotropic activity on guinea pig aortic strip and isolated atrium preparations, respectively. Comparison between survival plots and relative ID50, obtained from the K-562/doxR cells treated with Idarubicin (IDA), in the presence or absence of inhibitors, showed that these compounds function well. All the resistance modifying agents potentiated IDA activity inducing a significant reduction (P<0.01) in ID(50) values in comparison to VRP at each of the concentrations tested, but MM 36, CTS 27 and CTS 41 demonstrated the strongest activity. Results obtained from the MNCs were superimposible to K-562/doxR. Further studies on pump functional analysis confirmed the cytotoxic test results: MM 36, CTS 27 and CTS 41 showed a striking inhibition of P-glycoprotein (Pgp) efflux in K-562/doxR and MNCs. Cardiovascular activity of MM 36, CTS 27 and CTS 41, that are the most interesting compounds as MDR inhibitors, followed this course: MM 36>CTS 27>CTS 41, the last one presenting no cardiovascular activity. Chemosensivity to IDA in K-562/doxR cells and AML blasts could be enhanced in vitro by the adjuvant use of the six new VRP analogues. Compared to VRP, all the new compounds presented good MDR-reverting- and reduced cardiovascular activities along with no vasorelaxant effects. The particularly favourable results in some cases (MM 36, CTS 27 and CTS 41) suggests that anti-MDR activity should be further evaluated in clinical trials in patients with myeloid malignancies.

Anti-CD33 monoclonal antibodies enhance the cytotoxic effects of cytosine arabinoside and idarubicin on acute myeloid leukemia cells through similarities in their signaling pathways

OBJECTIVE

Chemotherapy agents (CA) such as cytosine arabinoside (ara-C), idarubicin (IDA), and etoposide (VP-16) are widely used in the treatment of acute myeloid leukemia (AML) However, their effects on signaling pathways leading to cytotoxicity have only been described recently. Ligation of the leukemia-associated antigen CD33 by anti-CD33 monoclonal antibody (mAb) also results in signaling events that induce a downregulation of cell growth. We examined the possibility that anti-CD33 mAb and CA might cooperate in mediation of growth inhibition in primary AML samples and AML cell lines.

MATERIALS AND METHODS

We investigated two AML cells lines and 14 primary AML samples for their proliferative response ((3)H-thymidine incorporation), colony formation, and biochemical (Western blot analysis) to anti-CD33 mAb treatment combined with chemotherapy agents.

RESULTS

CD33 ligation induced a significant increase in ara-C- or IDA- but not VP-16-or Bryostatin-mediated inhibition of proliferation and colony formation. Ara-C and IDA induced SHP-1 and SHP-2 protein tyrosine phosphatase (PTPs) phosphorylation and Lyn/SHP-1 complex formation, while VP-16 and Bryostatin did not. CD33 ligation, however, mediated phosphorylation of these PTPs and Syk/SHP-1 complex formations. Combined treatment of AML cells by ara-C or IDA with anti-CD33 mAb resulted in higher levels of SHP-1 phosphorylation. Reduction in SHP-1 by short interfering RNA abrogated these effects.

CONCLUSION

These data suggest that combined incubation of leukemia cells with anti-CD33 mAb and ara-C or IDA, but not VP-16 or Bryostatin, independently triggers similar events in the downstream signaling cascade, and therefore leads to additive antiproliferative effects and enhanced cytotoxicity.

Early Deaths and Treatment-Related Mortality in Children Undergoing Therapy for Acute Myeloid Leukemia: Analysis of the Multicenter Clinical Trials AML-BFM 93 and AML-BFM 98

Purpose

The rates of early death (ED) and treatment-related mortality (TRM) are unacceptably high in children undergoing intensive chemotherapy for acute myeloid leukemia (AML). Better strategies of supportive care might help to improve overall survival in these children.

Patients and Methods

In a retrospective study, we analyzed incidence, clinical features, and risk factors for lethal complications of 901 children enrolled onto the multicenter trials Acute Myeloid Leukemia-Berlin-Frankfurt-Muenster (AML-BFM) 93 and AML-BFM 98.

Results

One hundred four patients (11.5%) enrolled onto the clinical trials AML-BFM 93 and AML-BFM 98 died shortly after diagnosis or as a result of treatment-related complications. Thirty-two patients (3.5%) died before (six patients) or during (26 patients) the first 14 days of treatment, mainly as a result of bleeding or leukostasis. Low performance status, hyperleukocytosis, and French-American-British type M5 were the main risk factors for a lethal event before day 15. After day 15, the predominant causes of death were complications caused by infections, particularly bacterial and fungal infections. The incidence of lethal infections was highest during induction therapy and decreased thereafter. When comparing both clinical trials, significantly fewer patients died within the first 6 weeks in AML-BFM 98 than in AML-BFM 93 (14 [3.5%] of 430 patients v 35 [7.4%] of 471 patients; P = .01).

Conclusion

To reduce the high incidence of ED and TRM in children with AML, early diagnosis and adequate treatment of complications are needed. Children with AML should be treated in specialized pediatric cancer centers only. Prophylactic and therapeutic regimens for better treatment management of bleeding disorders and infectious complications have to be assessed in future trials to ultimately improve overall survival in children with AML.

New oral drugs in older patients: a review of idarubicin in elderly patients

Idarubicin (IDA) is a structural analogue of daunorubicin with the same mechanism of action. Unlike the other currently available anthracyclines, it has a significant oral bioavailability, which makes it particularly attractive for the treatment of elderly patients. IDA resulted at least as effective as daunorubicin for acute nonlymphocytic leukemia and additional data are in analysis as far as lymphomas and breast cancer are concerned. Adverse effects are mainly hematological, while hair loss, mucositis and cardiotoxicity are less frequently reported with IDA than with other anthracyclines. The pharmacokinetics, activity, adverse effects and new modalities of oral administration are reviewed.

Treatment of acute leukemia with idarubicin, etoposide and cytarabine (IDEA). A randomized study of etoposide schedule

BACKGROUND

The differences in toxicity of etoposide following continuous or bolus infusion are unknown.

METHODS

We studied the schedule-dependent toxicity of high-dose etoposide when combined with high-dose cytarabine and idarubicin (IDEA) in 138 patients with acute leukemia. Four groups of patients were studied: group I, relapse; group II, secondary acute myeloid leukemia (AML); group III, de novo AML, age >60 years; and group IV, induction failure or blast crisis of myeloproliferative syndrome. Treatment for groups I-III was idarubicin 8 mg/m(2) per day days 1-3, cytarabine 2000 mg/m(2) once a day days 1-6, and etoposide 1600 mg/m(2) total dose. Group IV treatment differed by cytarabine given twice daily days 1-6. Patients were randomized to etoposide as a continuous infusion days 1-6 or as a bolus infusion over 10 h on day 7.

RESULTS

Continuous infusion etoposide produced significantly more oral mucositis than bolus etoposide. In groups I-III, comparing continuous and bolus etoposide, there was a median of 3 vs 0 days of grade 2 or more oral mucositis (P<0.0001) and 13.5 vs 0 days of total parenteral nutrition (TPN) (P=0.0003). Group IV patients had a median 7 vs 0 days of grade 2 or more oral mucositis (P<0.01) and 21 vs 7 days of TPN (P<0.003), respectively. There were no differences in hematologic recovery, length of hospital stay, complete remission rate or overall survival between the two etoposide schedules. Of groups I-III patients, 51% achieved complete remission, and 11% died from treatment-related complications.

CONCLUSION

The toxicity profile of high-dose etoposide is schedule-dependent with prolonged exposure producing significantly more non-hematologic toxicity.

Activity of topoisomerase inhibitors daunorubicin, idarubicin, and aclarubicin in the Drosophila Somatic Mutation and Recombination Test

Anthracyclines have been widely used as anticancer drugs against different types of human cancers. The present study evaluated the mutagenic and recombinagenic properties of two anthracycline topoisomerase II (topo II) poisons, daunorubicin (DNR) and idarubicin (IDA), as well as the related topo II catalytic inhibitor aclarubicin (ACLA), using the wing Somatic Mutation and Recombination Test (SMART) in Drosophila melanogaster. The three anthracyclines were positive in this bioassay, producing mainly mitotic homologous recombination. The results for spot-size distribution and recombinagenic activity indicate that recombinational DNA damage accounts for approximately 91, 86, and 62% of DNR, IDA, and ACLA genotoxicity, respectively. Besides being a catalytic inhibitor of topo II, ACLA is also a topoisomerase I (topo I) poison. This dual topo I and II inhibitory effect, associated with its DNA-intercalating activity, could contribute to the activity of ACLA in the SMART assay.

Dexrazoxane's protection of jejunal crypt cells in the jejunum of C3Hf/Kam mice from doxorubicin-induced toxicity

Dexrazoxane (DEX) is used clinically to reduce doxorubicin-induced cardiotoxicity. Because DEX inhibits anthracycline-induced toxicity, we set out to investigate DEX's ability to reduce the incidence and severity of gastrointestinal toxicity associated with anthracycline administration in C3Hf/Kam mice. Doxorubicin and idarubicin, two commonly used anthracyclines, were each examined in combination with DEX. A jejunal crypt survival assay demonstrated that DEX increased crypt survival from 40% (doxorubicin 22.5 mg/kg) to 63% at a DEX/doxorubucin dose ratio of 10:1 ( P<0.05). When doxorubicin was increased to a dose of 27.5 mg/kg, crypt survival increased from 18% to 40% at a DEX:Dox ratio of 5:1 ( P<0.05). At ratios of 10:1 and 20:1, DEX had no protective effect on idarubicin-induced crypt cell toxicity. Our findings support the use of DEX to prevent or ameliorate mucositis in patients receiving anthracycline-based therapy and the use of DEX with high-dose doxorubicin to treat refractory disease.

Inhibition of membrane-associated calcium-independent phospholipase A2 as a potential culprit of anthracycline cardiotoxicity

Administration of anthracyclines, a family of highly effective anticancer drugs, is associated with a cumulative dose-related cardiomyopathy, the etiology of which remains poorly understood. We have discovered that administration of the anthracyclines leads to a marked inhibition of membrane-associated calcium-independent phospholipase A(2) (iPLA(2)) both in vitro and in vivo. To elucidate the clinical relevance of this effect and to correlate it with known cardiotoxicity of the individual anthracyclines, we have compared four anthracycline analogues: doxorubicin, daunorubicin, idarubicin, and epirubicin for their ability to inhibit iPLA(2). Isolated adult rat cardiomyocytes were treated with each analogue at concentrations of 0.1-100 micro M, and PLA(2) activity was assessed in cytosolic and membrane fractions using (16:0, [(3)H]18:1) plasmenylcholine in the absence of calcium. For all of the examined analogues, iPLA(2) inhibition was concentration and time dependent, preceded detectable changes in cell viability, and was specific to the membrane-associated enzyme. The degree of iPLA(2) inhibition by equimolar concentrations of epirubicin and idarubicin was significantly less than that of doxorubicin or daunorubicin, which correlates with the reported in vivo cardiotoxicity of these drugs. Because membrane iPLA(2) represents the majority of myocardial PLA(2) activity, its inhibition by anthracyclines would critically impair the ability of cardiomyocytes to repair oxidized phospholipids. Indeed, anthracycline-pretreated myocytes become more susceptible to the low-level oxidative stress imposed by repetitive additions of tert-butyl peroxide. The results suggest that iPLA(2) inhibition may be the initial step in a chain of events leading to chronic cardiotoxicity of the anthracyclines.

Activation of caspases-3/7 is dispensable for idarubicin-induced apoptotic DNA fragmentation in human leukemia cells

Idarubicin (IDA) is a 4-demethoxy-anthracycline analogue of daunorubicin (DNR). IDA has been recognized as a potent anti-leukemic agent. However, the molecular mechanism of IDA-induced cell death remains unclear. In the present study, we investigated the activity of IDA to induce apoptosis in human leukemia HL-60 and Jurkat cells, and studied its relationship with activation of caspases-3/7. IDA induced apoptotic DNA fragmentation in a time- and dose-dependent manner. The kinetics of apoptotic DNA fragmentation induced by IDA was well correlated with that of caspase-3/7 activation. We examined the effect of caspase-3/7 inhibitor Ac-DEVD-CHO on IDA-induced apoptosis in HL-60 and Jurkat cells. Ac-DEVD-CHO abolished IDA-induced caspases-3/7 activation in both cell lines. We have also found that L-carnitine can inhibit recombinant caspase-3 activity in vitro. L-carnitine treatment prevented IDA-induced caspases-3/7 activation in both cell lines in a dose-dependent manner. However, neither Ac-DEVD-CHO nor L-carnitine inhibited IDA-induced apoptotic internucleosomal DNA fragmentation in HL-60 or Jurkat cells. These data suggest that caspase-3/7 may be dispensable for idarubicin-induced internucleosomal DNA cleavage during apoptosis in human leukemia cells.

Effect of imatinib on haematopoietic recovery following idarubicin exposure

SCF is a potent pro-proliferative cytokine crucial for haematopoiesis, which binds to c-kit and activates its tyrosine kinase activity. Inactivating mutations of either SCF or c-kit have been described in mice and lead to increased sensitivity to treatment with ionising radiation. Imatinib is a tyrosine kinase inhibitor with high affinity for c-Abl, PDGFR and c-kit. In this study we investigated the effect of concomitant administration of imatinib and idarubicin, an anthracycline with haematosuppressive activity, in nu/nu mice and murine bone marrow cells. Double-treated animals showed significantly increased mortality compared to mice that received imatinib or idarubicin alone only when idarubicin and imatinib were given simultaneously. The combined treatment induced a more severe neutropenia with a slower recovery when compared to mice treated with idarubicin alone. The myeloid metaplasia usually observed in the spleen after idarubicin treatment was absent in mice co-treated with imatinib. Bone marrow from double-treated animals also showed decreased numbers of megakaryocytes and myeloid precursor cells. In vitro culture of murine bone marrow cells in the presence of imatinib inhibited SCF-induced proliferation and recovery from treatment with idarubicin. Our results indicate that the simultaneous administration of imatinib enhances idarubicin-induced haematopoietic toxicity in vivo and in vitro.

Idarubicin containing regimen in multiple myeloma: preliminary results of a pilot study using a modified "TANDEM" transplant program

Tandem autologous transplant actually represents a challenge in multiple myeloma treatment, but the best conditioning regimen is still under investigation. With the aim of evaluating the feasibility of a modified tandem transplant strategy, we treated 10 multiple myeloma patients after conventional first line chemotherapy with a two step conditioning regimen consisting of high-dose melphalan (200 mg/m2) followed by high-dose melphalan (180 mg/m2) together with indarubicin (15 mg/sqm2 c.i. x 3 days) both with peripheral stem cell support. At first transplant, the median age wasyears, performance status was good and disease status was CR in 2 patients and PR in the rest. At the end of the first transplant, 70% of patients achieved CR and only mild toxicity was observed. After the second transplant further improvement of the response rate was obtained with 90% CR. However, we observed three toxic early infection-related deaths from CMV and legionella pneumonia at day + 17, +26, +54 after transplantation. Although this schedule seems to be effective in terms of response rate, the 30% TRM imposes an anthracycline dose-reduction with careful patient selection. This approach could reduce the toxic effects and maintain the efficacy of therapy at the same time.

The influence of intracellular idarubicin and daunorubicin levels on drug cytotoxicity in childhood acute leukemia

Uptake and efflux of two anthracyclines, idarubicin (IDA) and daunorubicin (DNR), was studied in childhood acute leukemia samples. A comparison of IDA and DNR transport phenomena in relation to drug cytotoxicity and expression of P-glycoprotein (PGP) was made. Intracellular content of IDA/DNR was determined by flow cytometry using the fluorescent properties of the drugs. In vitro drug cytotoxicity was measured by the 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyl tetrazolium bromide (MTT) assay. PGP expression was analysed by flow cytometry. The uptake and efflux rates were non-significantly higher for IDA than DNR. There were no differences between three types of leukemia with respect to drug content during accumulation and retention. After correction for the cell volume, intracellular concentration of both drugs in each moment of uptake and efflux was significantly lower in relapsed ALL and AML samples in comparison with initial ALL cells. Efflux, but not uptake, of both drugs was inversely correlated with PGP expression and IDA, but not DNR, cytotoxicity. The cytotoxicity was correlated with drug accumulation for both drugs and with drug retention for IDA. In conclusion, it seems that (1) intracellular content was related to the lipophilic properties of the drugs rather than to the type of leukemia, (2) decreased intracellular concentration of both drugs might have an impact on compromised therapy results in AML and relapsed ALL children, (3) IDA presents higher cytotoxicity, which possibly might be decreased by the presence of PGP. These results might have a practical impact on the rational design of new chemotherapy protocols.

A comparison of the in vitro genotoxicity of anticancer drugs idarubicin and mitoxantrone

Idarubicin is an anthracycline antibiotic used in cancer therapy. Mitoxantrone is an anthracycline analog with presumed better antineoplastic activity and lesser toxicity. Using the alkaline comet assaywe showed that the drugs at 0.01-10 microM induced DNA damage in normal human lymphocytes. The effect induced by idarubicin was more pronounced than by mitoxantrone (P < 0.001). The cells treated with mitoxantrone at 1 microM were able to repair damage to their DNA within a 30-min incubation, whereas the lymphocytes exposed to idarubicin needed 180 min. Since anthracyclines are known to produce free radicals, we checked whether reactive oxygen species might be involved in the observed DNA damage. Catalase, an enzyme inactivating hydrogen peroxide, decreased the extent of DNA damage induced by idarubicin, but did not affect the extent evoked by mitoxantrone. Lymphocytes exposed to the drugs and treated with endonuclease III or formamidopyrimidine-DNA glycosylase (Fpg), enzymes recognizing and nicking oxidized bases, displayed a higher level of DNA damage than the untreated ones. 3-Methyladenine-DNA glycosylase II (AlkA), an enzyme recognizing and nicking mainly methylated bases in DNA, increased the extent of DNA damage caused by idarubicin, but not that induced by mitoxantrone. Our results indicate that the induction of secondary malignancies should be taken into account as side effects of the two drugs. Direct strand breaks, oxidation and methylation of the DNA bases can underlie the DNA-damaging effect of idarubicin, whereas mitoxantrone can induce strand breaks and modification of the bases, including oxidation. The observed in normal lymphocytes much lesser genotoxicity of mitoxantrone compared to idarubicin should be taken into account in planning chemotherapeutic strategies.

FLAG-IDA regimen (fludarabine, cytarabine, idarubicin and G-CSF) in the treatment of patients with high-risk myeloid malignancies

Forty-five patients with high-risk myeloid malignancies (32 acute myeloid leukemia and 13 high-risk myelodysplastic syndromes) were treated with fludarabine, cytarabine, idarubicin, and G-CSF (FLAG-IDA). Twenty-four (53%) patients achieved complete remission (CR), and five (11%) partial remission. Infection predominantly with pulmonary involvement was the most common regimen-related toxicity. Mucositis (15 patients) and pulmonary toxicity (19 patients) were the most frequently observed non-hematologic side effects. There were four early deaths and 12 patients presented with resistant disease. Overall survival (OS) at 12 months was 40%. The FLAG-IDA regimen shows evident antileukemic activity in patients with high-risk myeloid malignancies with acceptable toxicity.

Genotoxicity of idarubicin and its modulation by vitamins C and E and amifostine

Idarubicin is an anthracycline anticancer drug used in haematological malignancies. The main side effect of idarubicin is free-radicals based cardiotoxicity. Using the comet assay we showed that the drug at concentrations from the range 0.001 to 10 microM induced DNA damage in normal human lymphocytes, measured as the increase in percentage of DNA in the tail (% tail DNA). The effect was dose-dependent. Treated cells were able to recover within a 120-min incubation. Recognised cell protector, amifostine at 14 mM decreased the mean % tail DNA of the cells exposed to idarubicin at all tested concentrations of the drug. So did vitamin C at 10 microM, but vitamin E (alpha-tocopherol) at 50 microM increased the % tail DNA. Lymphocytes exposed to idarubicin and treated with endonuclease III, formamidopyrimidine-DNA glycosylase and 3-methyladenine-DNA glycosylase II, enzymes recognizing oxidized and alkylated bases, displayed greater extent of DNA damage than those not treated with these enzymes. Pretreatment of lymphocytes with nitrone spin traps, N-tert-butyl-alpha-phenylnitrone and alpha-(4-pyridil-1-oxide)-N-tert-butylnitrone decreased the extent of DNA damage evoked by idarubicin. To discuss the influence of vitamins and amifostine in cancer cells we used also murine pro-B lymphoid BaF3 transformed with BCR/ABL oncogene. These cells can be treated as model cells of human acute myelogenous leukemia. The response of these cells to vitamin E was quantitatively the same as human lymphocytes. However, vitamin C did not exert any effect on DNA damage and amifostine, in spite to normal lymphocytes, potentiated this effect. The results obtained suggest that reactive oxygen species, including free radicals, may be involved in the formation of DNA lesions induced by idarubicin. The drug can also methylate DNA bases. Our results indicate that not only cardiotoxicity but also genotoxicity and in consequence induction of secondary malignancies should be taken into account as diverse side effects of idarubicin. Amifostine may potentate DNA-damage effect of idarubicin in cancer cells and decrease this effect in normal cells. Vitamin C can be considered as protective agents against DNA damage in normal cells in persons receiving idarubicin-based chemotherapy, but the use of vitamin E cannot be recommended and at least needs further research.

Correlation between chromosome damage and apoptosis induced by fludarabine and idarubicin in normal human lymphocytes

Fludarabine (FLU, a fluorinated purine analog) and idarubicin (IDA, a DNA-topoisomerase II poison) are frequently used in cancer chemotherapy. The effects of these drugs on cultured normal human lymphocytes were studied to establish the possible involvement of chromosome damage in the apoptotic program. Chromosome aberrations (CA) were evaluated in first division metaphases and the apoptotic process was measured by morphological and electrophoretical techniques. The percentage of abnormal cells was increased from the doses of FLU 1.0 microg/ml and IDA 0.005 microg/ml (P<0.0001) with an important decrease in the mitotic index (MI) for the highest doses assayed. A significant dose-dependent induction of abnormal cells was observed for both drugs. An increase of apoptotic cells was found at 5.0 and 10.0 microg/ml of FLU (P<0.001) while IDA activated apoptosis at 0.05 microg/ml (P<0.01) and markedly from 0.1 microg/ml (P<0.001). These increments were dose dependent. Apoptotic cell morphology was associated with DNA fragmentation at the highest doses. The increased induction of abnormal cells and the decreased MI were in correlation with the apoptotic index for FLU and IDA, suggesting the role of CA in drug-induced cell death.

P-glycoprotein inhibitors enhance saturable uptake of idarubicin in rat heart: pharmacokinetic/pharmacodynamic modeling

Little is known about cardiac uptake kinetics of idarubicin, including a possible protective role of P-glycoprotein (Pgp)-mediated transport. This study therefore investigated uptake and negative inotropic action of idarubicin in the single-pass isolated perfused rat heart by using a pharmacokinetic/pharmacodynamic modeling approach. Idarubicin was administered as a 10-min constant infusion of 0.5 mg followed by a 70-min washout period in the absence and presence of the Pgp antagonists verapamil or amiodarone. Outflow concentration and left ventricular developed pressure were measured and the model parameters were estimated by simultaneous nonlinear regression. The results indicate the existence of a saturable, Michaelis-Menten type uptake process into the heart (K(m) = 3.06 microM, V(max) = 46.0 microM/min). Verapamil and amiodarone significantly enhanced the influx rate (V(max) increased 1.8-fold), suggesting that idarubicin is transported by Pgp directly out of the membrane before it gets into the cell. Verapamil and amiodarone attenuated the negative inotropic action of idarubicin, which was linked to the intracellular concentration of idarubicin.

Idarubicin, cytarabine, and topotecan in patients with refractory or relapsed acute myelogenous leukemia and high-risk myelodysplastic syndrome

In an effort to develop more effective therapy for patients with refractory or relapsed acute myelogenous leukemia (AML) and high-risk myelodysplastic syndrome (MDS), we investigated the efficacy of a combination chemotherapy consisting of idarubicin, cytarabine, and topotecan. Twenty-seven patients were treated: four with primary refractory AML, nine with AML in first relapse, four with AML in second relapse, and 10 with MDS-RAEB/RAEBT. Patients received as salvage therapy a single course of idarubicin 12 mg/m(2) IV bolus on days 1-3, cytarabine 1 g/m(2) over two hours q 12 hr on days 1-5, and topotecan 1.25 mg/m(2) over 24 hr on days 1-5. Median age was 42 years (range 17-65 years). All patients were evaluable for response: 14 (51.9%) achieved complete remission, 10 with AML (59%) and four with MDS (40%), respectively. Thirteen AML patients (excluding four relapsed after autologous stem cell transplantation) were grouped into four categories to stratify the probability of achieving complete remission (CR): group 1, first CR duration > or = 2 years and receiving first salvage treatment (S1); group 2, first CR duration 1-2 years and receiving S1; group 3, first CR duration 0-1 years and receiving S1; and group 4, first CR duration 0-1 years and receiving S2, S3, or S4 after failing S1. The response rate of each group was as follows: group 1, one of two (50%); group 2, one of one (100%); group 3, four of four (100%); group 4, two of six (33.3%). The median remission duration and survival of patients with AML were six and 12 months, respectively. Median duration of survival in 10 MDS patients was 15 months, and all four MDS patients achieving a CR maintained continuous CR with a median follow-up of 11 months. Severe myelosuppression was observed in all patients, resulting in fever or documented infections in 89% of patients. Median time to recovery of neutrophils > or =0.5 x 10(9)/l was 22 days (11-34) and for platelets > 20 x 10(9)/l 35 days (11-58). Reversible grade 3-4 toxicities included diarrhea (two patients) and mucositis (seven patients). We conclude that combination chemotherapy with intermediate dose cytarabine, idarubicin, and topotecan has significant antileukemic activity and acceptable toxicity in salvage AML and high-risk MDS.

Pharmacokinetics and toxicity of idarubicin in the rat

This study was designed to examine the pharmacokinetics and toxicity of idarubicin (IDA) in rats. In two groups of rats IDA was infused either into the V. iugularis interna or into the A. carotis communis, respectively. The venous plasma concentration of IDA and its primary metabolite idarubicinol (IDOL) were measured up to 48 hours by high-performance liquid chromatography (HPLC) with fluorescence detection. The weights of the rats and the levels of haemoglobin, leukocytes, and thrombocytes were recorded. The plasma concentration-time data were analysed, assuming a biexponential disposition curve, both by the traditional (two-stage) method and by population pharmacokinetic modelling. The basic pharmacokinetic parameters clearance (CL = 27.0 ml min(-1)), mean disposition residence time (MDRT = 519.2 min), and volume of distribution at steady state (Vss = 12.51) were estimated for IDA. The mean residence time (MRT) of the generated IDOL was 2982.5 min. No significant differences between pre- and postpulmonal injection were found in the pharmacokinetics and pharmacodynamics of IDA. The mean survival time of 13.3 days is attributed to a severe myelosuppression.

Oligonucleotide enhanced cytotoxicity of Idarubicin for lymphoma cells

Oligonucleotides offer the potential to manipulate gene expression in targeted cells which might be exploitable for therapeutic benefit. The effects of combining a phosphorothioate oligonucleotide OL(1) p53, which transiently down-regulates p53 levels, with an anthracycline, Idarubicin, on the growth of wild-type p53 WMN gene-expressing lymphoma cells was evaluated. Fluorescent OL(1) p53, was used to demonstrate oligonucleotide uptake and retention by the WMN cells. Uptake was maximal at 24 hours and compared to baseline (0 hours) increasing apoptotic cells were evident in WMN cells treated with OL(1) (1 microM) alone and in combination with Idarubicin (0.2 nM) for 24 to 48 hours. In cells treated with OL(1) p53 and Idarubicin, truncated p53 message of a predicted 201 base pair length based on RNAase H cleavage of the OL(1) p53-p53 mRNA heteroduplex was detected after 7 hours of incubation. The message for p53 was transiently downregulated as detected by RT-PCR analysis at 24 hours, and protein levels transiently reduced at 36 hours, as shown by a quantitative Western blot. Corresponding to these events, the growth of WMN cells ceased after 48 hours in the concurrent presence of OL(1) p53 and Idarubicin and, the lymphoma cells were dead after 72 hours. No reduction in hematopoietic colony forming cell capacity of similarly treated hematopoietic progenitor cells harvested from cytokine-mobilized blood by apheresis was observed. Therefore, synergistic cytotoxicity of Idarubicin for lymphoma cells treated with an oligonucleotide targeting p53 message was demonstrated at oligonucleotide and Idarubicin concentrations which were minimally toxic to hematopoietic progenitor cells. This approach offers new opportunities for purging of lymphoma cells from hematopoietic harvests and systemic lymphoma therapy.

Chemotherapy for mobilisation of Ph-negative progenitor cells from patients with CML: impact of different mobilisation regimens

Mobilised peripheral blood stem cells are widely used for autografting in patients with chronic myeloid leukaemia (CML) and it is generally thought that a high proportion of Ph-negative progenitor cells in the graft is desirable. We report here the results of 91 stem cell mobilisations performed with various chemotherapy regimens followed by G-CSF. We show that mobilisation of Ph-negative cells is possible after diagnosis as well as in advanced stages of the disease. The yield of Ph-negative cells is highly dependent on the chemotherapy regimen: while the combination of idarubicin and cytarabin for 3-5 days (IC3-5) mobilised Ph-negative cells in most patients, high-dose cyclophosphamide was ineffective. Mobilisation of Ph-negative progenitor cells after IC3 was at least as effective as after IC5; however, less apheresis sessions were required, and toxicity was much reduced after IC3. Compared to historical controls, IC was equally effective as the widely used ICE/miniICE (idarubicin, cytarabin, etoposide) protocol. No correlation was found between graft quality and the cytogenetic response to subsequent treatment with interferon-alpha. We conclude that IC3 is an effective and well-tolerated regimen for mobilising Ph-negative cells that compares well with more aggressive approaches such as IC5 and ICE/miniICE.

High-dose cytosine arabinoside and idarubicin treatment of chronic myeloid leukemia in myeloid blast crisis

Chronic myeloid leukemia in myeloid blast crisis (CML-MBC) is highly resistant to standard induction chemotherapy regimens. Anecdotal results from previous clinical trials support the concept of dose escalation in patients with CML-MBC. Eight patients with CML-MBC were treated with cytosine arabinoside (Ara-C) 1.5-3.0 g/m2 intravenously over 1 hr every 12 hr for 12 doses and idarubicin 12 mg/m2 intravenously daily for 3 days. Sixteen previous reports describing the use of Ara-C-based chemotherapy regimens in patients with CML-MBC were also reviewed. Our patients' median age was 62 years (range, 42-69 years). One patient achieved complete hematologic remission (95% confidence interval, 0.3%, 53%). The median survival for our patients was 7.3 months. These results were not different from previous published reports using Ara-C-based chemotherapy regimens to treat CML-MBC. In summary, the combination of high-dose Ara-C and idarubicin did not improve the overall prognosis of patients with CML-MBC. Innovative approaches need to be explored for this patient population.

Combination chemotherapy of intermediate-dose cytarabine, idarubicin, plus etoposide and subsequent mobilized donor leukocyte infusion for relapsed acute leukemia after allogeneic bone marrow transplantation

The efficacy and side effects of intermediate-dose cytarabine, idarubicin plus etoposide and subsequent donor leukocyte infusion (DLI) were investigated in patients with acute leukemia who relapsed after allogeneic bone marrow transplantation (BMT). Patients were given cytarabine continuous i.v. (1 g/m2 per day x 5), idarubicin i.v. (12 mg/m2 per day x 3), and etoposide i.v. infusion (150 mg/m2 per day x 3). Two days later, G-CSF mobilized donor leukocytes were infused for 2 days. No graft-versus-host disease (GVHD) prophylaxis was given. Between August 1997 and February 2000, 13 patients enrolled (eight acute myeloid leukemia (AML) and five acute lymphoblastic leukemia (ALL)). All patients finished chemotherapy and DLI. Eleven patients (85%) achieved complete remission (CR) at median 27 days after DLI. After median follow up of 10.9 months (2.5-33.3), five of 11 patients who achieved CR relapsed. Overall, six of 13 patients were surviving (6/8 AML and 0/5 ALL, P=0.059). Marrow recovery after chemotherapy and DLI was rapid (12 days for absolute neutrophil count (ANC) >500/microl). Side effects included fever with neutropenia (100%), pneumonia (46%), grade II-IV mucositis (69%), grade III-IV acute GVHD (45%), and extensive chronic GVHD (64%). One patient died from chronic GVHD. Chemotherapy containing intermediate-dose cytarabine and DLI produced a high CR rate in acute leukemia in relapse after allogeneic BMT. A fraction of patients are surviving long term. Side effects were substantial but manageable.

Double reinforcement with fludarabine/high-dose cytarabine enhances the impact of autologous stem cell transplantation in acute myeloid leukemia patients

Reinforced chemotherapy based on a double high-dose consolidation regimen could be a different way to enhance in vivo purging prior to autologous stem cell transplantation (auto-SCT) in acute myeloid leukemia (AML). We investigated the impact on outcome of auto-SCT after two different strategies of early intensification performed after an identical induction regimen in adult patients with AML. Between January 1993 and December 1998, 140 consecutive AML patients were enrolled in a program consisting of an identical anthracycline-based induction (ICE) and two different consolidation regimens: one cycle, cytarabine-based (single-NOVIA: 91 patients); two cycles, fludarabine-based (double-FLAN: 49 patients). Seventy out of 91 patients received single-NOVIA consolidation: 60 underwent a transplantation procedure (allogeneic bone marrow transplantation (allo-BMT):16 patients; auto-SCT: 44). Thirty-five out of 49 patients received double-FLAN consolidation: 31 underwent a transplantation procedure (allo-BMT: 10; auto-SCT: 21). The double consolidation regimen was well-tolerated with only minor side-effects. Median follow-up observation time for surviving patients was 38 months (range, 17-71) for the double-FLAN consolidation group and 70 months (range: 48-93) for the single-NOVIA consolidation group. Among the patients who received auto-SCT, the double consolidation strategy produced a superior disease-free survival curve at 36 months (78.6% (95%CI: 59.4-97.8) vs 47.7% (95%CI: 33-62.4)) compared with the single-NOVIA group. This difference was confirmed when the patients were analyzed for intention to treat (P = 0.04). In addition, the double-FLAN consolidation group showed a superior overall survival and lower relapse rate (P = 0.02). We conclude that the double-FLAN reinforcement strategy is safe and enhances the clinical impact of auto-SCT for AML patients in first complete remission. It may provide specific clinical benefit for patients undergoing auto-SCT.

Fludarabine, arabinosyl cytosine and idarubicin (FLAI) for remission induction in poor-risk acute myeloid leukemia

Progress in treatment of acute myeloid leukemia (AML) is slow and treatment intensification alone has limited effects, particularly in poor-risk cases. Poor-risk cases, that are identified mainly by prior history, leukemic cell mass and cytogenetic abnormalities, share multiple mechanisms of drug resistance that are responsible for treatment failure. Since Pgp-mediated resistance to anthracycline can be reduced with Idarubicin (IDA) and resistance to arabinosyl cytosine (AC) can be reduced with Fludarabine (FLUDA), we tested a combination of high dose AC (2000 mg/sqm, 5 doses), FLUDA (30 mg/sqm, 5 doses) and IDA (12 mg/sqm, 3 doses) for remission induction and consolidation in 45 consecutive cases of poor-risk AML. The complete remission (CR) rate was 71% after the first course and 82% overall, with a projected 2-year survival and relapse-free survival of 44% and 50% respectively. Non-hematologic toxicity was very mild, that is very important in elderly patients, but hemopoietic toxicity was substantial, with a time to hematologic recovery of 3 to 4 weeks and two cases of death in CR. Peripheral blood stem cells (PBSC) could be mobilized and collected successfully only in 11 cases. This three-drug combination is effective and has a limited non-hematologic toxicity, but FLUDA may increase the difficulty of obtaining PBSC early after remission induction.

Chemopreventive effects of grape seed proanthocyanidin extract on Chang liver cells

In an attempt to ameliorate the chemotherapy associated normal cell toxicity, in this study a known antioxidant, grape seed proanthocyanidin extract (GSPE) using Chang liver cells has been used. Chang liver cells were treated in vitro with idarubicin (Ida) (30 nM) and 4-hydroxyperoxycyclophosphamide (4-HC) (1 microg/ml) with or without proanthocyanidin (25 microg/ml). The cells were grown in vitro and the growth rate of the cells were determined using MTT assay. The results showed that the GSPE decreased growth inhibitory effects of Ida and 4-HC on Chang liver cells in vitro. Since these chemotherapeutic agents are known to induce apoptosis in the target cells, these cells were also analyzed for presence of apoptotic cells using flow cytometry. The GSPE decreased the number of apoptotic cell population induced by either chemotherapy. In an attempt to determine the mechanisms of ameliorating effects of proanthocyanidin, the expression of apoptosis/cell cycle/growth related genes, Bcl-2, p53 and c-myc was determined in the treated and control cells using Western blotting or reverse transcriptase-polymerase chain reaction (RT-PCR) techniques. There was an increased expression of Bcl-2 in the cells treated with GSPE. However, there was a significant decrease in the expression of other cell cycle related genes such as p53 and c-myc in these cells following treatment with GSPE. Thus, these results indicate that proanthocyanidin can be a potential candidate to ameliorate the toxic effects associated with chemotherapeutic agents used in treatment of cancer.

Long-term survival after induction therapy with idarubicin and cytosine arabinoside for de novo acute myeloid leukemia

We treated 153 patients with de novo acute myeloid leukemia (AML) with two induction courses of conventional-dose cytosine arabinoside (ara-C) and idarubicin (AIDA) followed by either a third course of AIDA, high-dose ara-C or bone-marrow transplantation. The complete remission (CR) rate for all patients was 63.4%, with a higher CR rate for patients with a normal (versus unfavorable) karyotype (73.2% vs 52.5%; P=0.038). The probability of overall survival (OS) was 30.7% after 5 years (26.3% after 7 years). Improved OS at 5 years could be observed for patients up to 50 years old versus patients older than 50 years of age (37.6% vs 19.9%; P=0.001) and patients with a normal (versus unfavorable) karyotype (42.9% vs 14.1%; P=0.0016). Disease-free survival (DFS) after 5 years was 33.2% for all 97 CR patients and was significantly better for patients with a normal (versus unfavorable) karyotype (44.3% vs 12.3%; P= 0.003). Multivariate analysis revealed that the age for OS (P < 0.02) and the karyotype for both OS (P<0.03) and DFS (P< 0.05) were independent prognostic factors. In conclusion, AIDA is an effective and well-tolerated induction regimen (even in elderly patients) with a 5-year survival of more than 30% when combined with ara-C-containing postremission therapy. The karyotype is the most powerful prognostic factor for predicting the outcome of patients treated with this protocol.

Treatment of anthracycline extravasation with dexrazoxane

Accidental extravasation of anthracyclines is a feared complication. Present treatment consists of local cooling and extensive surgical debridement, which often results in severe morbidity. All clinically important anthracyclines are topoisomerase II poisons that are antagonized by topoisomerase II catalytic inhibitors such as dexrazoxane. Therefore, we investigated whether dexrazoxane protects against extravasation lesions caused by anthracyclines. B6D2F1 mice received s.c. daunorubicin, doxorubicin, or idarubicin followed by systemic treatment with dexrazoxane or saline. One single systemic dose of dexrazoxane immediately after s.c. administration of doxorubicin, daunorubicin, or idarubicin reduced the tissue lesions (expressed as area under the curve of wound size times duration) by 96% (P < 0.0001), 70% (P < 0.0001), and 87% (P = 0.0004), respectively. Moreover, the treatment resulted in a statistically significant reduction in the fraction of mice with wounds as well as the duration of wounds. The induction of wounds was dose-dependent, as was the degree of protection by dexrazoxane. Dexrazoxane could be administered up to 3 h after the anthracycline without loss of protection. Triple-dosage of dexrazoxane tended to be more effective than a single injection. Dexrazoxane had no effect on lesions induced by hydrogen peroxide. This is the first report of use of a topoisomerase II catalytic inhibitor such as dexrazoxane in the treatment of anthracycline extravasation injuries. These convincing preclinical data represent a novel nontoxic approach that can easily be implemented into the clinical handling of accidental extravasation of anthracyclines.

Combination chemotherapy with risk factor-adjusted dose attenuation for high-risk myelodysplastic syndrome and resulting leukemia in the multicenter study of the Japan Adult Leukemia Study Group (JALSG): results of an interim analysis

Forty-nine adult patients with high-risk myelodysplastic syndrome (MDS) or acute myeloid leukemia that progressed from MDS were registered for the multicenter study of the Japan Adult Leukemia Study Group. Forty-three patients were evaluable for the analysis. Idarubicin 12 mg/m2 per day for 3 days and continuous cytosine arabinoside 100 mg/m2 per day for 7 days were given as induction therapy, followed by postremission chemotherapy after complete remission (CR). Because elderly patients and those with hypoplastic marrow usually have complications after intensive chemotherapy, often causing early death, the treatment dose was reduced to 60% or 80% according to the presence of 3 risk factors: age 60 years or older, performance status 2 or more, or presence of hypoplastic bone marrow. Of the 43 evaluable patients (median age, 58 years), 26 (60%) achieved CR. Two patients (5%) died within 2 months of completion of induction therapy. The CR rates for patients treated with 100%, 80%, and 60% of the chemotherapy dose were 55% (12 of 22), 63% (10 of 16), and 80% (4 of 5), respectively, indicating that the risk factor-adjusted dose attenuation was appropriately applied to those who might have had problems with the original dose, thus reducing regimen-related mortality rate. The median overall survival of the 43 patients was 8 months.

Dose-finding and pharmacologic study of chronic oral idarubicin therapy in metastatic breast cancer patients

Oral idarubicin (IDA) is an active drug in metastatic breast cancer, but its role in the management of this tumor is yet not established completely. To investigate a new modality of IDA administration, a dose-finding study was designed with hyperfractionated doses. The purpose was to determine the maximum tolerated dose (MTD), the dose-limiting toxicity (DLT), and the pharmacokinetics of this schedule. IDA was administered twice daily as outpatient therapy in cycles of 3 weeks followed by a 1-week rest. Thirty-one patients with progressive metastatic breast cancer and pretreated with chemotherapy (including epirubicin and doxorubicin) were enrolled. DLT was defined as G4 hematological toxicity or any other toxicity G3 or higher (Bloom and Richardson grading). Inter- and intrapatient dose increases were studied. Pharmacokinetics of IDA and its metabolite idarubicinol (IDOL) were evaluated. IDA dose was increased from 2 mg/day to 10 mg/day, by steps of 1 mg/day, with the larger dose given in the evening. MTD was reached at 10 mg/day. Overall, the therapy cycles were 69 (median/patient, 2; range, 1-6). DLTs were G4 neutropenia associated with leukopenia and thrombocytopenia in one patient and G3 diarrhea in another of the 5 patients in the 10 mg/day cohort. The two patients developing DLT at the daily dose of 10 mg received a dose normalized for body surface of 6.85 and 5.65 mg/m2/day, respectively. We considered 5.5 mg/m2/day to be the MTD. Other toxicities were nausea, vomiting, neutropenia, and diarrhea, grades G1 to G2. By univariate analysis, significant correlations were observed between absolute neutrophil count at nadir and IDA area under the curve (P = 0.022; r = -0.33), IDA Cmax (P = 0.0067; r = -0.38), IDOL area under the curve (P = 0.0009; r = -0.43), and IDOL Cmax (P = 0.0016; r = -0.41), respectively. By multivariate analysis, IDA Cmax was the strongest determinant for neutropenia (R2 = 0.14; P = 0.01). Among the 21 patients evaluable for response, 3 (14.3%) had partial response (lasting 3, 6, and 8 months, respectively), and 6 (28.6%) had a complete arrest of disease progression (lasting 2-6 months). In conclusion, the MTD of this schedule is 10 mg/day and the DLTs are neutropenia and diarrhea. Tolerance was good, and the treatment is feasible as home therapy. Some objective measurable responses were documented in this group of anthracycline-pretreated patients. IDOL could have a role for the pharmacological effect. Further evaluation of this schedule is warranted to assess the activity and toxicity of prolonged oral IDA administration.

Idarubicin and cyclophosphamide--an active oral chemotherapy regimen for advanced breast cancer

Between October 1993 and September 1994, 33 women with metastatic breast cancer aged between 29 and 74 years with a median age of 58 were entered into a study of oral chemotherapy from three UK centres. Patients by definition had metastatic disease and were fit and well with performance status 0 or 1 in 23 cases, 2 in seven cases and 3 in two cases (one missing). Five patients had received prior adjuvant CMF chemotherapy, nine first line non-anthracycline containing chemotherapy for relapse, eight patients second line non-anthracycline containing chemotherapy and all patients had had hormone therapy either as adjuvant or for relapsed disease. Adjuvant radiotherapy had been given to 17 and palliative radiotherapy to 12 patients. In nine patients there was one site of disease at start of therapy, in 10 two sites, in 11 three sites and in three patients four or more sites. The regimen comprised oral idarubicin 15 mg/m2 on day 1, 10 mg/m2 on days 2 and 3 and oral cyclophosphamide 250 mg/m2 (maximum 400 mg) on days 1, 2 and 3. Treatment was continued until disease progression or toxicity.

RESULTS

Overall 25% of 32 evaluable patients responded objectively including one complete response; 50% of patients had stable disease and 25% of patients progression. Among patients who had had no prior chemotherapy the objective response rate was 37.5%; 45% of patients had symptomatic improvement. The most common severe toxicity was granulocytopenia WHO grade 3 or more in 69.7% of patients. Thrombocytopenia grade 3 or 4 was seen in four patients. Six patients had documented infections and all but four patients had alopecia. All patients complained of mild or moderate fatigue. Nausea and vomiting occurred in 75% of patients but only four individuals had grade 3 toxicity. Two patients stopped therapy after myocardial infarction and one after impaired cardiac function was noted. The median time to progression was 2.7 months (1-11.5 months) and median survival time 8.8 months (1-13+ months).

CONCLUSION

The combination chemotherapy is active in heavily treated patients with manageable toxicity but there are problems in heavily pre-treated patients. There was good compliance in taking medication and at the doses chosen the drugs appear to be suitable for younger fitter patients.

Idarubicin-145-2C11-F(ab')2 promotes peripheral tolerance and reduces chronic vascular disease in mouse cardiac allografts

In order to reduce the toxic effects of the T cell activating anti-CD3 monoclonal antibody, 145-2C11, F(ab')2 fragments were prepared by pepsin digestion. These fragments were then used as non-immunosuppressive carriers for the cytotoxic drug idarubicin (IDA), to reduce toxicity of both the monodonal antibodies (mAb) and the drug and to increase the specificity of drug delivery. The IDA-145-2C11 F(ab')2 immunoconjugate was tested for specificity by fluorometry. 145-2C11 intact antibody, 145-2C11 F(ab')2 and IDA conjugates of the antibody and F(ab')2 were used to treat CBA recipients of BALB/c vascularized cardiac allografts. Mice with hearts surviving >100 days were challenged with donor and third party (C57BL/6) skin grafts. Although both antibody and F(ab')2 blocked the binding of 145-2C11-FITC to CBA spleen cells, only the intact antibody caused sustained depletion of CD3 cells in vivo. 145-2C11 F(ab')2 blocked cell surface CD3 within 30 min, but was cleared in 24 h without depletion of CD3 cells from the spleen. In BALB/c to CBA cardiac allografts (rejected in 12-17 days), IDA-145-2C11 F(ab')2 (0.2 mg/20 g mouse i.p. at the time of transplantation) induced >100 days' allograft survival and specific tolerance, in contrast to the equivalent dose of 145-2C11 F(ab')2 (mean survival 25 days). Hearts from IDA-145-2C11 F(ab')2-treated mice at >100 days showed decreased cellular infiltration and less chronic vascular disease than long-surviving hearts from mice treated with an alternative antibody, KT3. Thus, F(ab')2 prepared from 145-2C11 provided a suitable CD3-specific, nonimmunosuppressive carrier for IDA. This immunoconjugate was more effective against both acute and chronic rejection than other conjugates or whole antibody. IDA-145-2C11 F(ab')2 is an effective, nontoxic tolerogen in the mouse cardiac allograft model.

Fludarabine-based chemotherapy in untreated mantle cell lymphomas: an encouraging experience in 29 patients

BACKGROUND AND OBJECTIVE

A prospective study to evaluate the role of fludarabine alone or in combination with idarubicin in untreated patients with mantle cell lymphoma (MCL).

DESIGN AND METHODS

Twenty-nine untreated patients with mantle cell lymphoma were stochastically treated with intravenous fludarabine at a dose of 25 mg/m(2)/day for 5 days (11 patients) or with a combination of fludarabine and idarubicin (FLU-ID) (fludarabine 25 mg/m(2) i.v. on days 1 to 3 and idarubicin 12 mg/m(2) i.v. on day 1 (18 patients). For both regimens, cycles were given at three-week intervals for a total of six courses. According to the International Prognostic Index, the most part of high-intermediate and high risk factor patients were in the FLU-ID subset: 7 (39%) patients vs. 2 (18%) in the fludarabine alone subset.

RESULTS

Of the 29 patients, 8 (28%) obtained a complete response and 10 (35%) a partial response, with an overall response rate of 63%. The remaining 11 (37%) patients did not respond to the therapy. The overall response rates were 64% (7 patients) in the fludarabine group and 61% (11 patients) in the FLU-ID group. The complete response rate was 27% (3 patients) for fludarabine and 28% (5 patients) for FLU-ID. The toxicity was mild in terms of neutropenia and infections, and no fatalities occurred due to drug-induced side effects.

INTERPRETATION AND CONCLUSIONS

These results suggest the efficacy of fludarabine alone or in combination with idarubicin in MCL patients. It will be important to increase this experience and to assess other fludarabine-containing regimens, in particular with cyclophosphamide plus idarubicin and with mitoxantrone and or cyclophosphamide, to test the true role of this approach in MCL.

Triggering noncycling hematopoietic progenitors and leukemic blasts to proliferate increases anthracycline retention and toxicity by downregulating multidrug resistance

Expression of the multidrug resistance (MDR) mechanisms P-glycoprotein (Pgp) and MDR-related protein (MRP) decrease cellular retention and consequently cytotoxicity of anthracyclines. MDR is expressed on normal human hematopoietic progenitors and leukemic blasts. Normal CD34(+) progenitors showed rhodamine efflux in 20% to 30% of the cells, which could be blocked by verapamil. These cells appeared noncycling, in contrast to the proliferating rhodamine bright (RhoB) cells. We postulated that MDR expression can be downregulated by proliferation induction. Triggering rhodamine dull (RhoD) CD34(+) cells to proliferate indeed resulted in a higher rhodamine retention and significantly decreased efflux modulation by verapamil (P =.04). Also in acute myeloid leukemia (AML), the proliferation rate (percentage S/G(2)+M and Iododeoxyuridine labelings index) was significantly less in the RhoD blasts (P </=. 008) and proliferation induction of RhoD blasts resulted in increased rhodamine retention. Anthracycline cytotoxicity was less for RhoD than RhoB cells in both normal progenitors and leukemic blasts. Proliferation induction of the RhoD cells resulted in increased anthracycline sensitivity. We conclude that noncycling progenitors, both normal and leukemic, have a relatively high MDR expression. Triggering these cells into proliferation downregulates MDR expression. These findings can be exploited to overcome MDR in the treatment of AML patients.

Apoptosis by anthracyclines at therapeutic concentrations in MDR1+ human leukemic cells

Induction of apoptosis by daunorubicin (DNR) and idarubicin (IDA) was evaluated cytofluorometrically in CEM and CEM-MDR1+ leukemic cells exposed to drug concentrations similar to peak plasma levels obtainable in vivo (DNR 200-400 ng/ml, IDA 50-100 ng/ml, 30' incubation), and differentiating apoptosis from necrosis (FITC-annexin V+/propidium iodide- and + cells, respectively). Firstly, to set experimental conditions, apoptosis was evaluated in CEM cells at 3, 6, 12, 18, 24, 48, 72, and 96 hours from end of drug incubation, the maximal increase being noted at 24-48 hours. Net apoptosis rates were determined after subtraction of the spontaneous activity observed in untreated cells. The apoptotic effect from varying drug type and concentration was compared at 24 hours in CEM-MDR1+ cells, with and without co-incubation with MDR1 functional downregulator cyclosporin A (CSA) used at therapeutic concentration (1500 ng/ml). The results indicated that, at drug concentrations likely to be approached in vivo as a short-lasting peak level (IDA 100-200 ng/ml) with increased-dose IDA (> 12-15 mg/m2), pro-apoptotic effects by IDA+CSA in CEM-MDR1+ cells were significantly greater than by DNR+CSA, and corresponded to the levels observed with IDA 50 ng/ml without CSA in control CEM cells. This in vitro study demonstrates that it is possible to determine in the same sample cell fluorescence related to anthracyclines, apoptotic cells (FITC-annexin V positive), and necrotic cells (propidium iodide positive), and confirms that cytofluorimetric evaluation of apoptosis can reliably predict the effects of anthracycines in function of drug type, concentration and, in MDR1+ cells, concurrent MDR1 inhibition. Extension of this assay to the clinical ground may be warranted.

Effects of PARP inhibition on drug and Fas-induced apoptosis in leukaemic cells

Poly (ADP-ribose) polymerase (PARP) is activated following binding to DNA strand breaks and is cleaved in cells undergoing apoptosis. Work predominantly in murine systems has suggested that inhibitors of PARP might potentiate the effects of chemotherapeutic agents and be used as adjuncts to cancer therapy. Therefore, we studied the role of PARP in drug-induced apoptosis in HL-60, myeloid leukaemia cells and found that pre-treatment with 3-aminobenzamide (3AB) or 6(5H)-phenanthridinone, inhibitors of PARP, resulted in resistance to, rather than potentiation of apoptotic death induced by DNA-damaging agents, idarubicin, etoposide and fludarabine, as determined by flow cytometry, following propidium iodide staining. 3AB treated CEM/VLB100, mdr-expressing human lymphoblastic leukaemia cells were also found to be more resistant to idarubicin compared to cells treated with idarubicin alone, however, apoptosis was not reduced in parental CCRF-CEM cells under the same conditions. Similar results were obtained using agents with primary modes of action which do not involve DNA damage, vinblastine and a fas-ligating antibody (CH11). The precise role of PARP has yet to be defined but might involve effects on cell cycle progression. We conclude that PARP activation appears to be involved in apoptosis in certain leukaemic cell lines and that these effects are independent of lineage or p-glycoprotein. Constitutive failure to activate PARP might be responsible for conferring resistance to apoptosis.

Inhibition of FAS/FAS-ligand does not block chemotherapy-induced apoptosis in drug sensitive and resistant cells

It has been suggested that one means by which chemotherapeutic agents exert their effect on leukaemic cells, is via autocrine induction of fas-ligand which then binds to fas (CD95), activates the caspase pathway and results ultimately in apoptotic death. In order to test this hypothesis, we have treated leukaemic cell lines with various chemotherapeutic agents (idarubicin, etoposide, fludarabine and 2-CdA) with and without pre-treatment with fas (ZB4) and fas-ligand (NOK-1) blocking monoclonal antibodies. Cell cycle analysis and quantitation of apoptosis were performed by flow cytometry following propidium iodide staining. HL-60 cells were found to be sensitive to the induction of apoptosis with all drugs tested but were highly resistant to treatment with a fas-ligating antibody (CH11). Apoptosis was neither inhibited in parental CEM cells nor their mdr-expressing drug resistant counterpart, CEM/VLB100 by pre-treatment with either ZB4 or NOK1. In addition, CEM/VLB100 were slightly more sensitive to treatment with CH11 (100 ng/ml) than parental CEM cells (% age apoptosis = 30.35 and 23.675, p = 0.024) and at least as sensitive to recombinant fas-ligand (50 ng/ml) (% age apoptosis = 26.6 and 20.2, p = NS). We conclude that it is unlikely that fas/fas-ligand interactions play a significant role in the induction of apoptosis by these chemotherapeutic agents in the leukaemic cell lines tested.

Comparative cardiotoxicity of idarubicin and doxorubicin using the isolated perfused rat heart model

Attempts to reduce the incidence of congestive heart failure following anthracycline therapy include the replacement of the parent compounds (especially doxorubicin) by less cardiotoxic analogs. Among these analogs, idarubicin (4-demethoxy-daunorubicin) was shown to be less cardiotoxic than doxorubicin in phase II clinical trials, but its actual cardiotoxicity has never been evaluated in large series and has never been compared to that of doxorubicin in relevant experimental models. Using the isolated perfused rat heart model, we compared the cardiac effects (developed pressure, contractility and relaxation of the left ventricle) induced by idarubicin to those induced by doxorubicin. Drugs were administered i.v. every other day for 11 days at doses of 1, 2, 2.5 and 3 mg/kg per injection for doxorubicin and 0.5, 0.75 and 1 mg/kg per injection for idarubicin. We confirmed that similar general toxicity symptoms were obtained for a dose ratio of 1:4 (idarubicin:doxorubicin). However, at the maximum tolerated doses of both drugs (3 mg/kg per injection for doxorubicin and 0.75 mg/kg per injection for idarubicin), the cardiac toxicity of idarubicin remained significantly lower than that of doxorubicin. Anthracycline cardiac accumulation was evaluated in parallel and revealed a lower cardiac accumulation of idarubicin, which could explain the reduced cardiac toxicity of this analog. Direct perfusion of the drugs in the isolated hearts of untreated animals revealed that idarubicin was taken up more readily than doxorubicin in the cardiac tissue, despite the fact that it had less deleterious effects on cardiac function. This indicates that idarubicin also had less intrinsic cardiotoxicity than doxorubicin in this model.

Anthraquinone-induced cell injury: acute toxicity of carminomycin, epirubicin, idarubicin and mitoxantrone in isolated cardiomyocytes

Acute toxic effects of the antineoplastic anthraquinones carminomycin, epirubicin, idarubicin and mitoxantrone were studied in primary cultures of cardiomyocytes, which were isolated from adult rats. Both time- and concentration-dependent changes of cell structure and viability (trypan blue exclusion) following incubation of myocytes with subclinical, clinical and toxic concentrations of the anthraquinones were examined by light microscopy. The area under the decay curve of viable and rod-shaped myocytes was used to express cytotoxicity of the drugs. Mitoxantrone was found to reduce cell viability and number of rod-shaped cells to the greatest extent, followed by carminomycin, idarubicin and epirubicin. A significantly lower accumulation in cardiomyocytes was obtained with epirubicin and idarubicin compared with carminomycin. An inhibitory effect on oxygen consumption by the cells occurred already at 0.1 microM with epirubicin, whereas inhibition caused by other anthraquinones was less pronounced. Our data indicate a weak association of net accumulation and the toxicity parameter IC50 for carminomycin and idarubicin. In contrast to these results, a more significant correlation of cytotoxicity and anthraquinone lipophilicity was found, which suggests that the lipophilic character of a particular anthraquinone may be an important factor in drug-induced acute cardiotoxicity.

Induction of MDR1 gene expression by anthracycline analogues in a human drug resistant leukaemia cell line

The effects of 4-demethoxydaunorubicin (idarubicin, IDA) and MX2, a new morpholino-anthracycline, on up-regulation of the MDR1 gene in the low-level multidrug resistant (MDR) cell line CEM/A7R were compared at similar concentrations (IC10, IC50 and IC90) over a short time exposure (4 and 24 h). The chemosensitivity of each drug was determined by a 3-day cell growth inhibition assay. Compared with epirubicin (EPI), IDA and MX2 were 17- and eightfold more effective in the CEM/A7R line respectively. No cross-resistance to 5-FU was seen in the CEM/A7R line. Verapamil (5 microM) and PSC 833 (1 microM), which dramatically reversed resistance to EPI in the CEM/A7R line, had no sensitizing effect on the resistance of this line to MX2, but slightly decreased resistance to IDA. The sensitivity to 5-FU was unchanged by these modulators. The induction of MDR1 mRNA expression by IDA, MX2 and 5-FU was analysed by Northern blotting and semiquantitatively assessed by scanning Northern blots on a phosphorimager. The relative level of MDR1 expression was expressed as a ratio of MDR1 mRNA to the internal RNA control glyceraldehyde-3-phosphate dehydrogenase (GAPDH). IDA, MX2 and 5-FU differentially up-regulated MDR1 mRNA in the CEM/A7R line in a dose-dependent manner. Both IDA and MX2 induced MDR1 expression within 4 h. 5-FU up-regulated MDR1 expression only when drug exposure was prolonged to 24 h. Based on MRK 16 binding, flow cytometric analysis of P-glycoprotein (Pgp) expression paralleled the increase in MDR1 mRNA levels. For the three anthracyclines, the increase in MDR1 expression was stable in cells grown in the absence of drug for more than 3 weeks after drug treatment. The induction of MDR1 expression by 5-FU was transient, associated with a rapid decrease in the increased Pgp levels which returned to baseline 72 h after the removal of 5-FU. This study demonstrates that MDR1 expression can be induced by analogues of anthracyclines not pumped by Pgp, and that this induction appears to be stable despite a 3-week drug-free period.

Human DNA topoisomerase IIalpha-dependent DNA cleavage and yeast cell killing by anthracycline analogues

Anthracyclines are among the most clinically useful topoisomerase II poisons. A complete understanding of their molecular mechanism is thus fundamental for a rational design of novel agents. We evaluated four anthracycline analogues with respect to human topoisomerase IIalpha-dependent DNA cleaving activity, efficiency in killing yeast cells, and uptake and retention in yeast and compared the yeast system to tumor cell line models. The yeast JN394top2-4 strain was used because it has a topoisomerase II ts gene mutation: enzyme activity is much less at 30 degrees C than at 25 degrees C and is completely lost at 35 degrees C. Untransformed JN394top2-4 cells were 33-fold more sensitive to idarubicin at 25 degrees C than at 30 degrees C, showing that topoisomerase II is the primary drug target. Overexpression of human topoisomerase IIalpha was toxic to yeast cells when the yeast enzyme was inactivated. Drug-dependent killing of yeast cells expressing low levels of the human alpha isoenzyme at 35 degrees C showed that the analogues spanned a 3-log range of cytotoxic potency in yeast, as they did in tumor cells. However, the compounds were much less active against the yeast strain than mammalian tumor cell lines. Drug uptake was determined and found to be altered in yeast with respect to tumor cells. Although DNA cleavage stimulated by anthracyclines roughly correlated with cytotoxicity, the cleavage level:cytotoxicity ratios were different for the studied drugs. Thus, the results suggest that other drug-dependent molecular factors contribute to drug activity in addition to the cellular content of topoisomerase IIalpha and drug uptake.

Acute myelogenous leukemia in Down's syndrome: report of a single pediatric institution using a BFM treatment strategy

Between July 1990 and December 1995, 111 new consecutive pediatric patients with acute myelogenous leukemia (AML) have been treated in our institution. Eleven of them (9.9%) had Down's syndrome (DS), 6 boys and 5 girls. The median age was 22.5 (range 10-40) months. FAB subtypes were the following: M7: 6, M4: 3, and M0: 2. Five of them had previously had myelodysplasia and in 3, all FAB M7, myelofibrosis was detected. This population was treated with two consecutive protocols. Nine patients were included in the AML-HPG-90 protocol and 2 patients in the AML-HPG-95 study, respectively. However, all DS patients in this series received the same treatment. Eight patients achieved complete remission: two patients received two cycles of intensification with high dose (HD) ara-C, and 1 patient, only one cycle; the other 5 were prevented from receiving such therapy because of unacceptable toxicity or death. At 45 months, event-free survival and overall survival estimates were 0.30, S.E. 0.16. Mortality was remarkably high. All deaths (7) were associated with sepsis (5) or pulmonary infection (2). Three deaths occurred before achieving complete remission, 3 patients died during the consolidation phase and 1 died whilst off treatment. No one presented leukemic relapse. We conclude that this AML-BFM treatment strategy is highly toxic to children with DS and AML in our setting. Efforts will be made to improve clinical support and to administer less intensive therapy to this particular pediatric AML subgroup, which, in fact, has a better prognosis than the same non-trisomic population.