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In the present study, the dosage and duration of rasburicase administration were retrospectively evaluated for the ability to control the serum uric acid (S-UA) level in 13 patients diagnosed with hematological malignancies and tumor lysis syndrome (TLS), or those at risk of developing TLS, at the University of Fukui Hospital. At the time of diagnosis, seven patients already exhibited laboratory TLS, and three demonstrated clinical TLS. All patients received rasburicase in addition to chemotherapy agents. The median dose was 0.19 mg/kg (range, 0.13–0.25 mg/kg), and the median duration was four days (range, 1–7 days). Six patients sequentially received a xanthine oxidase inhibitor, allopurinol or febuxostat. The primary estimate was the normalization of the S-UA level at the end of rasburicase treatment and on treatment day seven. The average S-UA level prior to treatment was 10.4±4.5 mg/dl (mean ±standard deviation), and 11 out of 13 patients demonstrated a S-UA level >7 mg/dl. The S-UA level at the end of rasburicase administration was 0.5±1.5 mg/dl and the S-UA level at day seven was 1.4±1.5 mg/dl. All the patients achieved normalization of the S-UA level. On day seven subsequent to the initiation of treatment, the patients receiving rasburicase for a maximum of three days exhibited an S-UA level of 1.9±1.8 mg/dl, while the patients receiving rasburicase for longer than three days demonstrated an S-UA level of 1.0±1.3 mg/dl (P=0.20; Mann-Whitney test). The administration of 0.13 mg/kg and 0.22 mg/kg resulted in comparable UA level reductions. The administration of allopurinol or febuxostat following rasburicase administration suppressed the re-increase in S-UA level. Therefore, it was concluded that reduced administration of rasburicase successfully controlled the S-UA level in TLS.

Background To examine the utility of diffusion-weighted MRI (DW-MRI) for staging and early response to chemotherapy assessment in lymphoma patients as compared with fluorodeoxyglucose positron emission tomography/computed tomography (FDG-PET/CT). Methods Twenty-eight patients with histologically confirmed malignant lymphoma underwent both MRI and FDG-PET/CT before (pretreatment) and after two courses of chemotherapy (mid-treatment). Staging with MRI (DW-MRI alone and with T2-weighted images) and FDG-PET was compared visually, and the concordance rate (kappa value, κ) was calculated. To evaluate early response to chemotherapy, patients were divided into two groups, lesion-positive (LP) and lesion-negative (LN), based on a proposed original criterion. Progression-free survival (PFS) was compared between the groups using the Kaplan-Meier method. Results The stage diagnosed with DW-MRI alone and with FDG-PET/CT was concordant in 22 patients (κ = 0.71; P

Tumor lysis syndrome (TLS) is a life-threatening oncological emergency, in which control of serum uric acid (S-UA) levels is important. S-UA-lowering efficacy of a new xanthine oxidase inhibitor, febuxostat, was retrospectively evaluated in seven patients with hematological malignancies who were at an intermediate risk of developing TLS. A 10-mg dose of febuxostat was initiated and chemotherapy was started within 24 h of administering the first dose of febuxostat. Febuxostat was continued until at least day 7 of chemotherapy treatment. The UA-lowering treatment was considered effective if febuxostat reduced S-UA levels to ≤7.5 mg/dl by day 5. The mean S-UA level at base line was 6.4±2.6 mg/dl and, on day 5, the mean S-UA level was 4.7±1.8 mg/dl. All the patients achieved S-UA levels ≤7.5 mg/dl. Serum creatinine levels decreased from 0.93±0.25 to 0.85±0.25 mg/dl. The estimated glomerular filtration rate values increased from 69.7±24.5 to 76.9±26.2 ml/min. No adverse reactions were noted during the study period and no patients experienced progressive TLS. Successful control of S-UA and improved renal function were obtained in response to febuxostat treatment in cancer patients at a risk of TLS.

The collection of clinical samples, such as bone marrow (BM) and peripheral blood, is an important procedure for the extraction of the cellular RNA. It is essential to preserve the extracted RNA during and after the collection of clinical samples to ensure the accurate analysis of gene expression. To date, the PAXgene™ Blood RNA System has been proven useful for stabilizing RNA extracted from peripheral blood; however, a problem concerning the stability of the total RNA stored using the system has been identified. The PAXgene™ Bone Marrow RNA System (BM system) is a newly developed system, and its clinical usefulness as a stabilizer for the cellular RNA in BM and peripheral blood was investigated with respect to the quality of RNA extracted using this system. A quantitative reverse transcriptase polymerase chain reaction (RT-PCR) was carried out using total RNA extracted with the BM system, which showed that total RNA was more stable in the BM system than in the conventional system, indicating that the BM system can be applied to RT-PCR. The BM system enabled us to detect Wilms' tumor suppressor gene (WT1) more effectively than the conventional system. In conclusion, the BM system is clinically valuable for extracting and stabilizing total RNA of high quality.

Summary Objectives The rapid diagnosis of bacteremia is crucial for patient management including the choice of antimicrobial therapy, especially in cases of hematological disease, because neutropenia occurs frequently during antineoplastic chemotherapy or disease progression. We describe a rapid detection and identification system that uses universal PCR primers to amplify a variable region of bacterial 16S ribosomal DNA (rDNA), followed by DNA microarray hybridization. Methods Probes for 72 microorganisms including most causal clinical pathogens were spotted onto a microarray plate. The DNA microarray and conventional methods of identification were applied to 335 cultures from patients with hematological diseases. Results Forty-one samples (12.2%) tested positive by conventional blood culture test in a few days, while 40 cases (11.9%) were identified by the new method within 24h. The sensitivity and specificity of this new method were 93% and 99%, respectively, compared with conventional blood culture testing. Conclusions PCR combined with a DNA microarray is useful for the management of febrile patients with hematological diseases.

Gemtuzumab ozogamicin (GO) consists of the CD33 antibody linked to calicheamicin. The binding of GO to the CD33 antigen on leukemic cells results in internalization followed by the release of calicheamicin, thereby inducing DNA strand breaks. We hypothesized that the induction of DNA strand breaks would be a surrogate marker of GO cytotoxcity. Here, two GO‐resistant variants (HL/GO‐CSA [225‐fold], HL/GO [200‐fold]) were established by serially incubating human leukemia HL‐60 cells with GO with or without a P‐glycoprotein (P‐gp) inhibitor, cyclosporine A, respectively. The CD33 positivity was reduced in both variants. The HL/GO‐CSA cells showed an increased multidrug resistance protein‐1 (MRP1) transcript, and an MRP1 inhibitor partially reversed GO resistance. The HL/GO cells had neither P‐gp nor MRP1 overexpression. Microarray analysis and Western blotting indicated elevated levels of DNA repair‐associated proteins in both variants. Two other leukemic subclones, showing either P‐gp or MRP1 overexpression, were also GO‐resistant. Using single cell gel electrophoresis analysis, it was determined that GO‐induced DNA strand breaks increased dose‐dependently in HL‐60 cells, whereas the number of breaks was reduced in the GO‐resistant cell lines. The induction of DNA strand breaks was correlated with GO sensitivity among these cell lines. The CD33 positivity and the expression levels of transporters were not proportional to drug sensitivity. Using primary leukemic cells, the induction of DNA strand breaks appeared to be associated with GO sensitivity. Thus, GO‐induced DNA strand breaks as the final output of the mechanism of action would be critical to predict GO cytotoxicity.

We evaluated the diagnostic utility of peripheral blood neutrophil distribution patterns obtained using the CELL-DYN SAPPHIRE hematology analyzer in patients with myelodysplastic syndrome (MDS). Peripheral blood was obtained from 467 individuals including 32 patients with MDS, and the respective neutrophil distribution patterns were observed using two light scatters [7-degree complexity (7D) and 90-degree lobularity (90D)]. These scattering intensities are shown as median (median neutrophil distribution: MND) and coefficient of variation (neutrophil distribution width: NDW). Generally, MDS patients showed lower 7D MND, higher 7D NDW, lower 90D MND and higher 90D NDW than other comparable groups. Whereas 90D parameters were more diagnostically efficient than 7D ones in patients with MDS. The sensitivity and specificity of 90D MND for MDS patients became 78.1 and 78.9%, respectively (cut-off value = 14,514). 90D NDW was most diagnostically effective with 87.5% sensitivity and 91.0% specificity (cut-off value = 21.2%). Both 90D parameters showed no evident correlation with the degree of either leukocytopenia or peripheral blood dysgranulopoiesis. In conclusion, neutrophil distribution parameters, especially 90D NDW, appear to provide convenient and objective markers for the screening of patients with MDS in routine laboratory hematology.

近年輸血副作用の把握の重要性が認識され，その頻度や重症度について統計をとることが多施設で行われつつある．しかし時に集計の困難さもあり充分な集計ができない場合がある．我々は電子カルテを利用した副作用管理システムを樹立し全輸血における副作用報告を收集できるようになった．その結果バッグ単位ではなく通常報告されていない患者単位の副作用発生頻度の算出を容易にし興味ある結果を得たので報告する． 【対象】2008年1月から2009年12月の期間，輸血を実施した患者を対象とした．【結果】赤血球濃厚液（RCC）は1,154人で5,156バッグ，新鮮凍結血漿（FFP）は261人で1,795バッグ，濃厚血小板血漿（PC）は350人で3,394バッグの輸血が行なわれた．輸血副作用発生実人数はRCC 20人（1.7％），FFP 12人（4.6％），PC 50人（14.2％）であった．PCによる副作用頻度が最も高く診療科別でもPCの使用の多い血液腫瘍内科で22.2％，小児科で23.7％発生していた．患者単位での副作用はバッグ単位の副作用に比較し数倍の頻度が認められ，輸血副作用の評価は両者を比較しつつ行うことが重要であり，電子カルテを利用した副作用管理システムは副作用情報収集に有用と考えられた．

Glutathione S-transferase mu (GSTM1) is mainly known as a detoxification enzyme but it has also been shown to be a negative regulator of apoptosis-related signaling cascades. Recently GSTM1 has been reported to be a significant risk factor for hematological relapse in childhood acute lymphoblastic leukemia, although the underlying mechanism remains largely unknown. Glucocorticoids play a crucial role in the treatment of childhood acute lymphoblastic leukemia, therefore we hypothesized that GSTM1 plays important roles in glucocorticoid-induced apoptotic pathways. To clarify the relationship between GSTM1 and drug resistance, GSTM1 was transfected into a T-acute lymphoblastic leukemia cell line, CCRF-CEM (CEM), and we established the GSTM1-expressing cell lines CEM/M1-4 and CEM/M1-9. Transduction of GSTM1 into CEM selectively decreased cellular sensitivity to dexamethasone in a manner that was independent of glutathione conjugation, but was due to apoptosis inhibition. Dexamethasone-induced p38-MAPK and Bim activation were concomitantly suppressed. Interestingly, nuclear factor kappa b (NF-kappaB) p50 activity was upregulated in GSTM1-expressing CEM. Inhibition of NF-kappaB by the pharmacological agent BAY11-7082 greatly enhanced the sensitivity of the GSTM1-expressing CEM to dexamethasone and was accompanied by an increase in Bim expression. Thus, we propose that GSTM1, a novel regulator of dexamethasone-induced apoptosis, causes dexamethasone resistance by suppression of Bim through dual mechanisms of both downregulation of p38-MAPK and upregulation of NF-kappaB p50.

Cytarabine (ara-C) is the key agent for treating acute myeloid leukemia (AML). After being transported into leukemic cells by human equilibrative nucleoside transporter 1 (hENT1), ara-C is phosphorylated to ara-C triphosphate (ara-CTP), an active metabolite, and then incorporated into DNA, thereby inhibiting DNA synthesis. Deoxycytidine kinase (dCK) and cytosolic 5'-nucleotidase II (cN-II) are associated with the production of ara-CTP. Because ara-C's cytotoxicity depends on ara-CTP production, parameters that are most related to ara-CTP formation would predict ara-C sensitivity and the clinical outcome of ara-C therapy. The present study focused on finding any correlation between the capacity to produce ara-CTP and ara-C-metabolizing factors. In vitro ara-CTP production, mRNA levels of hENT1, dCK, and cN-II, and ara-C sensitivity were evaluated in 34 blast samples from 33 leukemic patients including 26 with AML. A large degree of heterogeneity was seen in the capacity to produce ara-CTP and in mRNA levels of hENT1, dCK, and cN-II. Despite the lack of any association between each of the transcript levels and ara-CTP production, the ratio of dCK/cN-II transcript levels correlated significantly with the amount of ara-CTP among AML samples. The HL-60 cultured leukemia cell line and its three ara-C-resistant variants (HL-60/R1, HL-60/R2, HL-60/R3), which were 8-, 10-, and 500-fold more resistant than HL-60, respectively, were evaluated similarly. The dCK/cN-II ratio was again proportional to ara-CTP production and to ara-C sensitivity. The dCK/cN-II ratio may thus predict the capacity for ara-CTP production and ultimately, ara-C sensitivity in AML.

原発性アミロイドーシス7例に対して自己末梢血幹細胞移植併用melphalan大量療法を実施した．顆粒球コロニー刺激因子の単独投与で必要な末梢血幹細胞の確保が可能で，7例中2例（29%）に血液学的寛解が得られた．心アミロイドーシスの存在した2例は移植後それぞれ42日目と159日目に治療関連死亡し，安全性確保の観点から本治療の対象外とする必要性が推測された．非寛解の4例にサルベージ治療が行われ3例に血液学的効果が得られた．Melphalan大量療法またはサルベージ治療で血液学的効果の得られた5例中4例（80%）に臨床症状の改善または安定化が得られた．心アミロイドーシスを除外すればmelphalan大量療法は安全に実施可能と推測されたが有効性には限界がある．心アミロイドーシス例やmelphalan大量療法の無効例には新規治療法を組み込んだ更なる臨床研究が必要である．

The combination of cytarabine (ara-C) with fludarabine is a common approach to treating resistant acute myeloid leukemia. Success depends on a fludarabine triphosphate (F-ara-ATP)-mediated increase in the active intracellular metabolite of ara-C, ara-C 5'-triphosphate (ara-CTP). Therapy-resistant leukemia may exhibit ara-C resistance, the mechanisms of which might induce cross-resistance to fludarabine with reduced F-ara-ATP formation. The present study evaluated the effect of combining ara-C and fludarabine on ara-C-resistant leukemic cells in vitro. Two variant cell lines (R1 and R2) were 8-fold and 10-fold more ara-C resistant, respectively, than the parental HL-60 cells. Reduced deoxycytidine kinase activity was demonstrated in R1 and R2 cells, and R2 cells also showed an increase in cytosolic 5'-nucleotidase II activity. Compared with HL-60 cells, R1 and R2 cells produced smaller amounts of ara-CTP. Both variants accumulated less F-ara-ATP than HL-60 cells and showed cross-resistance to fludarabine nucleoside (F-ara-A). R2 cells, however, accumulated much smaller amounts of F-ara-ATP and were more F-ara-A resistant than R1 cells. In HL-60 and R1 cells, F-ara-A pretreatment followed by ara-C incubation produced F-ara-ATP concentrations sufficient for augmenting ara-CTP production, thereby enhancing ara-C cytotoxicity. No potentiation was observed in R2 cells. Nucleotidase might preferentially degrade F-ara-A monophosphate over ara-C monophosphate, leading to reduced F-ara-ATP production and thereby compromising the F-ara-A-mediated potentiation of ara-C cytotoxicity in R2 cells. Thus, F-ara-A-mediated enhancement of ara-C cytotoxicity depended on F-ara-ATP accumulation in ara-C-resistant leukemic cells but ultimately was associated with the mechanism of ara-C resistance.

We have established an arsenic trioxide (As2O3)-resistant cell line (K562/AS-3) derived from the human leukemia cell line K562. K562/AS-3 was sequentially cultured with increasing concentrations of As2O3 up to 3.5 microM and then cloned by the limiting dilution method. K562/AS-3 was found to be about 7-fold more resistant to As2O3 than the parent cells (IC50=12.9 microM for K562/AS-3 and 1.8 microM for K562), and also showed cross resistance to VP-16 and vincristine. The multidrug resistance-associated protein (MRP1) gene was found to be overexpressed, but the MDR gene was not detected. MRP1 function was evaluated by measuring calcein acetoxymethyl ester (calcein-AM) efflux, and by verifying its inhibition by MK571, a potent MRP inhibitor. In addition, an increase of the total intracellular glutathione content was found in K562/AS-3. The resistance of K562/AS-3 to As2O3 was reversed by the addition of MK571, but not by verapamil. K562/AS-3 may be useful for studying the mechanism of the anticancer effect of As2O3 and how to overcome As2O3-resistance.

Standardized treatments for indolent B cell lymphoma primarily consisting of follicular lymphoma (FL) and for mantle cell lymphoma (MCL) have yet to be established. Here the Hokuriku Hematology Oncology Study Group conducted a multicenter prospective study to investigate the efficacy and safety of a combination regimen of rituximab, cladribine, mitoxantrone, and dexamethasone (R-CMD) in indolent B cell lymphoma and MCL. A total of 33 CD20-positive patients who received care between January 2008 and August 2011 were investigated. These patients' illnesses were FL (n = 21), nodal marginal zone B cell lymphoma (NMZB, n = 3), MCL (n = 3), splenic marginal zone B cell lymphoma (n = 2), hairy cell leukemia (n = 1), Waldenstrom macroglobulinemia (WM, n = 1), and lymphoplasmacytic lymphoma (LPL, n = 2). Patients received four 21-day cycles of rituximab 375 mg/m(2) (day 1), cladribine 0.10 mg/kg (days 1-3), mitoxantrone 8 mg/m(2) (day 1), and dexamethasone 8 mg/body (days 1-3), with four additional rituximab doses at 4-week intervals. Of the 33 patients, 26 achieved complete response/unconfirmed complete response, and six achieved a partial response (4 with FL, 1 with NMZB, 1 with WM). One had progressive disease (FL), and four relapsed after remission (1 with FL, 2 with MCL, 1 with LPL). R-CMD therapy was relatively convenient and effective in indolent B cell lymphoma and MCL. Nonetheless, to suppress the number and function of both B cells and T cells, comprehensive infection prevention and follow-up are necessary in the future.

CpG DNA induces plasmacytoid dendritic cells (pDC) to produce type I IFN and chemokines. However, it has not been fully elucidated how the TLR9 signaling pathway is linked to these gene expressions. We examined the mechanisms involving the TLR9 and type I IFN signaling pathways, in relation to CpG DNA-induced IFN-α, IFN regulatory factor (IRF)-7, and chemokines CXCL10 and CCL3 in human pDC. In pDC, NF-κB subunits p65 and p50 were constitutively activated. pDC also constitutively expressed IRF-7 and CCL3, and the gene expressions seemed to be regulated by NF-κB. CpG DNA enhanced the NF-κB p65/p50 activity, which collaborated with p38 MAPK to up-regulate the expressions of IRF-7, CXCL10, and CCL3 in a manner independent of type I IFN signaling. We then examined the pathway through which IFN-α is expressed. Type I IFN induced the expression of IRF-7, but not of IFN-α, in a NF-κB-independent way. CpG DNA enabled the type I IFN-treated pDC to express IFN-α in the presence of NF-κB/p38 MAPK inhibitor, and chloroquine abrogated this effect. With CpG DNA, IRF-7, both constitutively and newly expressed, moved to the nuclei independently of NF-κB/p38 MAPK. These findings suggest that, in CpG DNA-stimulated human pDC, the induction of IRF-7, CXCL10, and CCL3 is mediated by the NF-κB/p38 MAPK pathway, and that IRF-7 is activated upstream of the activation of NF-κB/p38 MAPK in chloroquine-sensitive regulatory machinery, thereby leading to the expression of IFN-α.

International audience; Topoisomerase I (Top1), an abundant nuclear enzyme expressed throughout the cell cycle, relaxes DNA supercoiling by forming transient covalent DNA cleavage complexes. We show here that staurosporine, a ubiquitous inducer of apoptosis in mammalian cells, stabilizes cellular Top1 cleavage complexes. These complexes are formed indirectly as staurosporine cannot induce Top1 cleavage complexes in normal DNA with recombinant Top1 or nuclear extract from normal cells. In treated cells, staurosporine produces oxidative DNA lesions and generates reactive oxygen species (ROS). Quenching of these ROS by the antioxidant N-acetyl-l-cysteine or inhibition of the mitochondrial dependent production of ROS by the caspase inhibitor benzyloxycarbonyl-VAD prevents staurosporine-induced Top1 cleavage complexes. Down-regulation of Top1 by small interfering RNA decreases staurosporine-induced apoptotic DNA fragmentation. We propose that Top1 cleavage complexes resulting from oxidative DNA lesions generated by ROS in staurosporine-treated cells contribute to the full apoptotic response.

The prognosis of acute myeloid leukemia (AML) in elderly patients remains poor due to their poor general condition and the intrinsic chemotherapy-resistant nature of their leukemia cells. The present retrospective study evaluated the clinical background as well as the response to treatment, of an unselected group of elderly patients with AML who were admitted to our Institution over a period of six years.Patients aged 65 years or older with AML admitted to our Institution between January 2005 and May 2011 were evaluated retrospectively.Forty-six patients were admitted to our Institution, among whom 41 received remission induction chemotherapy. Twenty-four patients received intensive chemotherapy, while 13 received low-dose cytarabine-based chemotherapy. Other modalities were used in four patients. Complete remission was obtained in 20 patients (48.8%). The complete remission rate (50.0%) tended to be higher in patients receiving intensive chemotherapy than in those receiving low-dose cytarabine-based regimens (30.7%; p=0.25). The median survival time for the whole patient group was 12 months and the 2-year overall survival was 18%. The median survival times for patients with complete remission and for non-responding patients were 14 months and 7 months, respectively. The 2-year overall survival in patients with complete remission was 32%, while that of non-responding patients was 6% (p=0.0025, log-rank test).The present study suggests the necessity of achieving complete remission for obtaining better survival for elderly patients with AML.

To examine the utility of diffusion-weighted MRI (DW-MRI) for staging and early response to chemotherapy assessment in lymphoma patients as compared with fluorodeoxyglucose positron emission tomography/computed tomography (FDG-PET/CT).Twenty-eight patients with histologically confirmed malignant lymphoma underwent both MRI and FDG-PET/CT before (pretreatment) and after two courses of chemotherapy (mid-treatment). Staging with MRI (DW-MRI alone and with T2-weighted images) and FDG-PET was compared visually, and the concordance rate (kappa value, κ) was calculated. To evaluate early response to chemotherapy, patients were divided into two groups, lesion-positive (LP) and lesion-negative (LN), based on a proposed original criterion. Progression-free survival (PFS) was compared between the groups using the Kaplan-Meier method.The stage diagnosed with DW-MRI alone and with FDG-PET/CT was concordant in 22 patients (κ = 0.71; P 0.05), and by adding T2-weighted images, the number of concordant patients increased to 26 (κ = 0.90; P 0.05). On mid-treatment imaging, 19 patients were diagnosed as LN from both modalities. PFS differed significantly between LP and LN on both DW-MRI (P = 0.0013) and FDG-PET/CT (P = 0.037).DW-MRI is a promising tool for staging and evaluation of early response to chemotherapy in patients with lymphoma.

1-beta-D-Arabinofuranosylcytosine (ara-C) is used empirically at a low, conventional, or high dose. Ara-C therapy may be optimal if it is directed by the clinical pharmacokinetics of the intracellular active metabolite of ara-C, 1-beta-D-arabinofuranosylcytosine 5'-triphosphate (ara-CTP). However, ara-CTP has seldom been monitored during low- and conventional-dose ara-C therapies because detection methods were insufficiently sensitive. Here, with the use of our newly established method (Cancer Res., 56, 1800 -- 1804 (1996)), ara-CTP was monitored in leukemic cells from acute myelogenous leukemia patients receiving low- or conventional-dose ara-C [subcutaneous ara-C administration (10 mg / m(2) ) (3 patients), continuous ara-C infusion (20 or 70 mg / m(2) / 24 h) (7 patients), 2-h ara-C infusion (70 mg / m(2) ) (4 patients), and 2-h infusion of N(4)-behenoyl-1-beta-D-arabinofuranosylcytosine, a deaminase-resistant ara-C derivative (70 mg / m(2) ) (6 patients)]. Ara-CTP could be determined at levels under 1 microM. There was a close correlation between the elimination half-life values of the plasma ara-C and the intracellular ara-CTP. The presence of ara-C in the plasma was important to maintain ara-CTP. The continuous ara-C and the 2-h N(4)-behenoyl-1-beta-D-arabinofuranosylcytosine infusions maintained ara-CTP and the plasma ara-C longer than the subcutaneous ara-C or the 2-h ara-C infusion. They also afforded relatively higher ara-CTP concentrations, and consequently produced ara-CTP more efficiently than the 2-h ara-C infusion. Different administration methods produced different quantities of ara-CTP even at the same dose.

A retrospective study was performed on 125 patients with de-novo acute myeloid leukemia (AML) who had received first remission induction therapy at Fukui Medical University Hospital in the 16 years between 1983 and 1998. For remission induction therapies, patients in the 1980s received mainly behenoylcytarabine (BHAC), 6-mercaptopurine (6-MP), and prednisolone (PSL), plus aclarubicin (ACR) or daunorubicin (DNR). Patients in the 1990s received mainly BHAC, 6-MP, and etoposide (VP-16) plus DNR or mitoxantrone (MIT) or idarubicin (IDA). Patients with hypoplastic bone marrow received low-dose cytarabine (Ara-C) therapy or cytarabine ocfosfate (SPAC). Since 1992, patients with French-American-British disease classification of M3 have received all-trans retinoic acid (ATRA) (+/-chemotherapy). In the 1990s, more intensified postremission therapy was performed compared with that done in the 1980s. The complete remission (CR) rate of all patients was 58%. Predicted 6-year overall survival (OS) and disease-free survival (DFS) rates in the CR patients were 22% and 28%, respectively. Multivariate analysis showed age and leukocyte counts as significant prognostic factors regarding CR, OS, and DFS rates. The CR and OS rates in the 1990s were improved significantly from those in the 1980s, at 69% versus 48% (P = 0.016), and 32% versus 15% (P = 0.0014), respectively. The early death rate, within 30 days, was decreased from 26% in the 1980s to 9% in the 1990s (P = 0.013). This decrease was thought to be the main cause of the high CR rate in the 1990s. However, DFS was not significantly improved. It is necessary to establish more effective postremission therapies in order to reduce the relapse rate and improve the prognosis.

N(4)-Behenoyl-1-beta-D-arabinofuranosylcytosine (BHAC), a prodrug of 1-beta-D-arabinofuranosylcytosine, is used effectively for the treatment of leukemia in Japan. BHAC therapy may be more effective if it is delivered in conjunction with monitoring of 1-beta-D-arabinofuranosylcytosine 5'-triphosphate (ara-CTP), the intracellular active metabolite of ara-C derived from BHAC. However, previous monitoring methods for ara-CTP were insufficiently sensitive. Here, using our new sensitive method, we evaluated the ara-CTP pharmacokinetics in relation to the therapeutic response in 11 acute myelogenous leukemia patients who received a 2-h infusion of BHAC (70 mg / m(2)) in combination remission induction therapy. ara-CTP could be monitored at levels under 1 mM. BHAC maintained effective levels of plasma ara-C and intracellular ara-CTP for a longer time, even compared with historical values of high-dose ara-C. The area under the concentration-time curve of ara-CTP was significantly greater in the patients with complete remission than in the patients without response. This greater amount of ara-CTP was attributed to the higher ara-CTP concentrations achieved in the responding patients. There was no apparent difference of plasma ara-C pharmacokinetics between the two groups. Thus, for the first time, the ara-CTP pharmacokinetics was evaluated in relation to the therapeutic effect of BHAC, and the importance of ara-CTP was proven. Administration of optimal BHAC therapy may require monitoring of the ara-CTP pharmacokinetics in each individual patient.

We evaluated the outcome of anti-leukemia chemotherapy on 42 patients with the high-risk myelodysplastic syndromes (MDS)—refractory anemia with excess of blasts (RAEB), 8 cases; RAEB in transformation (RAEB-T), 18 cases; chronic myelomonocytic leukemia (CMMOL), 6 cases; and leukemic transformation of MDS, 10 cases. The median age was 67 (range 20 to 84). As a remission-induction therapy, 35 patients received low-dose chemotherapy, such as low-dose cytarabine infusion, and seven patients received high-dose combination chemotherapy. The complete remission (CR) rates of the low-dose chemotherapy group and the high-dose combination chemotherapy group were 29% and 57%, respectively, and the overall CR rate was 33%. The median survival durations after induction chemotherapy of the CR group (14 cases), the partial remission (PR) group (11 cases), and the non-remission (NR) group (17 cases) were 19 months, 8 months, and 3 months, respectively. As a post-remission consolidation chemotherapy, high-dose combination chemotherapy seemed to be superior to low-dose chemotherapy judging from the median CR duration (16 months versus 4 months), but a long-term disease-free survival is hardly expected, in contrast with results in cases of de novo acute myeloid leukemia.

Uric acid in serum (S-UA) is produced by the breakdown of the cellular nucleic acids of leukemia cells, and may be a marker of disease aggressiveness. S-UA levels were examined for association with clinical outcomes in patients with acute myeloid leukemia (AML). Fifty-six patients with AML admitted to our Institution were evaluated retrospectively. The median S-UA level at diagnosis was 5.0 mg/dl (range 2-13.8 mg/dl). The S-UA levels did not correlate with peripheral lactate dehydrogenase, peripheral white blood cell counts, or peripheral blast counts, and were not proportional to bone marrow blast counts or marrow cellularity. The S-UA levels in the patients who achieved complete remission were slightly lower than those in those who did not. S-UA levels less than, or equal to the median (5.0 mg/dl) were significantly associated with better prognoses, compared with S-UA levels greater than 5.0 mg/dl. Thus, the S-UA level may predict the prognosis of AML, and is a versatile and cost-effective test for such a purpose.

The present retrospective study was conducted to measure Wilms' tumor-1 (WT1) mRNA levels in the peripheral blood of patients with acute myeloid leukemia (AML) in order to examine any association with the clinical outcomes.A total of 58 AML patients were evaluated retrospectively in our institution. WT1 transcripts were determined by real-time reverse transcriptase-polymerase chain reaction in peripheral blood samples.WT1 levels at diagnosis did not vary according to response of induction treatments, and the levels were comparable between the patients with durable remission and the patients with relapse of disease. WT1 levels at the completion of the treatment were higher in the group with relapse of disease than in the group with sustained remission. Detectable WT1 transcripts after the completion of chemotherapy courses were associated with poor prognoses.WT1 mRNA levels at treatment completion may predict for prognosis of AML.

The collection of clinical samples, such as bone marrow (BM) and peripheral blood, is an important procedure for the extraction of the cellular RNA. It is essential to preserve the extracted RNA during and after the collection of clinical samples to ensure the accurate analysis of gene expression. To date, the PAXgene(TM) Blood RNA System has been proven useful for stabilizing RNA extracted from peripheral blood; however, a problem concerning the stability of the total RNA stored using the system has been identified. The PAXgene(TM) Bone Marrow RNA System (BM system) is a newly developed system, and its clinical usefulness as a stabilizer for the cellular RNA in BM and peripheral blood was investigated with respect to the quality of RNA extracted using this system. A quantitative reverse transcriptase polymerase chain reaction (RT‐PCR) was carried out using total RNA extracted with the BM system, which showed that total RNA was more stable in the BM system than in the conventional system, indicating that the BM system can be applied to RT‐PCR. The BM system enabled us to detect Wilms’ tumor suppressor gene (WT1) more effectively than the conventional system. In conclusion, the BM system is clinically valuable for extracting and stabilizing total RNA of high quality.

Pancytopenia is caused by acute myeloid leukemia (AML), myelodysplastic syndrome (MDS), aplastic anemia (AA), or by non-hematological diseases. Because Wilms' tumor-1 (WT1) is overexpressed in patients with AML and MDS, its expression level may be helpful for diagnosing these hematological malignancies.We retrospectively investigated the WT1 transcripts in peripheral blood (PB) from 47 patients with decreased blood cell counts.The final diagnoses included AML, MDS, AA, drug poisoning, and non-hematological diseases. PB WT1 mRNA was overexpressed in AML and MDS, whereas the patients with other diseases mostly tested negatively for the transcript. The patients with MDS with higher marrow blast counts had higher PB WT1 mRNA levels. The sensitivity of the PB WT1 transcript in detecting AML and MDS was 78%, and the specificity was 90%.The WT1 mRNA level in PB may help diagnose AML and MDS in patients with pancytopenia.

We conducted a prospective, multicenter cooperative study to compare two courses of modified intermediate-dose cytarabine (Ara-C) (mIDAC; Ara-C at a dose of 1.0 g/m(2) every 12 hours for 5 days) versus high-dose Ara-C (HDAC; Ara-C at a dose of 2.0 g/m(2) every 12 hours for 5 days) in post-remission therapy for acute myeloid leukemia (AML) to confirm the post-remission antileukemic efficacy and safety of mIDAC.Twenty-six newly diagnosed patients with AML underwent remission induction therapy consisted of behenoyl Ara-C, mitoxantrone, etoposide, and 6-mercaptopurine. Post-remission therapy included four courses of consolidation and four courses of intensification. Patients who achieved complete remission (CR) were randomly assigned to mIDAC or HDAC for the second course of consolidation. The third course of intensification was the same as the second course of consolidation. Other post-remission therapies were the same in each group.Twenty-two patients (84.6%) achieved CR and 21 patients were randomly assigned to receive either mIDAC (n=11) or HDAC (n=10). The predicted 4-year relapse-free survival for the mIDAC group and for the HDAC group were 49% and 56%, respectively (p=0.86). Although HDAC developed severe leukocytopenia compared to mIDAC, there were no significant differences between HDAC and mIDAC in the incidence of ≥grade 3 and ≥grade 4 documented infections. The mean lowest white blood cell count (WBC) after HDAC was significantly lower than that after mIDAC (0.208±0.120×10(3)/mm(3) and 0.459±0.333×10(3)/mm(3), respectively, p0.05). The time to WBC recovery to 2.0×10(3)/mm(3) after HDAC was significantly longer than that after mIDAC (34.3±12.1 days and 27.1±9.5 days, respectively, p0.05).This study suggests that mIDAC may have an equivalent post-remission antileukemic efficacy to HDAC with less myelosuppression for AML patients.

The reversing effect of toremifene, a new tamoxifen derivative, on multidrug resistance in a K562 subline and its mechanism were studied. K562 cells were cultured in serially increasing concentrations up to 1.0 microM daunorubicin (DNR), and were found to be 28 times more resistant to DNR in comparison to the parent cells. In the resistant cell line (K562/D1-9), intracellular accumulation of DNR was less than that of the parent cell line, and P-glycoprotein was overexpressed. The resistance was reversed by addition of toremifene in a dose-dependent manner in K562/D1-9, while toremifene had no effect in K562. DNR accumulation was also reversed by toremifene in K562/D1-9, but not in K562. However, there was no significant difference of toremifene retention between K562/D1-9 and K562, and neither verapamil nor DNR increased toremifene accumulation in K562/D1-9. Moreover, toremifene and verapamil did not show an additive effect on intracellular DNR accumulation. These results suggested that the reversing mechanism of toremifene is different from that of verapamil, and this compound could be a good candidate for overcoming multidrug resistance.

Cytarabine (ara-C) is the key drug for treatment of acute myeloid leukemia. Since intracellular cytarabine triphosphate (ara-CTP) is an active metabolite of ara-C, factors that reduce the amount of ara-CTP are known to induce drug resistance. However, these factors do not fully explain the development of resistance to ara-C. The present study was conducted to search for new candidate ara-C resistance factors, including those that are unrelated to ara-CTP production. For this purpose, we newly established five ara-C-resistant leukemic clones from different blood cell lineage leukemic cell lines (HL-60, K562, CEM, THP1 and U937). The resistant subclones were 5-58-fold more ara-C-resistant than their parental counterparts. All of the ara-C-resistant subclones, except for ara-C-resistant CEM cells, displayed alteration of ara-CTP-related factors such as ara-C membrane transport capacity, deoxycytidine kinase activity or cytosolic nucleotidase II activity. To identify new candidate factors, we used two comprehensive approaches: DNA microarray and proteome analyses. The DNA microarray analysis revealed eight genes (C19orf2, HSPA8, LGALS1, POU4F3, PSAP, AKT1, MBC2 and CACNA2D3) that were altered in all five ara-C-resistant lines compared to parental cells. Both proteome and DNA microarray analyses further detected a reduced protein level of stathmin1 in the ara-C-resistant CEM subclone compared to its parental line. Thus, the present findings suggested the involvement of novel multiple mechanisms in mediating the ara-C resistance of leukemic cells. The role of some of these molecules in resistance is still unclear.

Low-dose cytarabine (ara-C) has been used to treat older patients with acute myeloid leukemia (AML) or high-risk myelodysplastic syndrome (MDS), but has resulted in complete remission for20% of cases. A pilot study of the efficacy of a combination chemotherapy using low-dose ara-C, melphalan (Mel), and mitoxantrone (Mit) was conducted.The treatment comprised ara-C (10 mg/m2) twice daily, melphalan (2 mg/body) every other day, and mitoxantrone (3 mg/m2) every 3 days. The treatment was discontinued if the nuclear cell count was15,000/microl with20% blast count in the bone marrow. The primary end-points were initial response and tolerability.The study comprised 9 patients with AML or high-risk MDS (median age, 75 years). Complete remission was achieved in 3 patients. All the patients displayed grade 4 neutropenia and thrombocytopenia. One patient died from sepsis.The present regimen was more effective and displayed similar safety, compared with low-dose ara-C alone.

Central nervous system (CNS) relapse accompanying the prolonged administration of imatinib mesylate has recently become apparent as an impediment to the therapy of Philadelphia chromosome–positive (Ph+) leukemia. CNS relapse may be explained by limited penetration of imatinib mesylate into the cerebrospinal fluid because of the presence of P-glycoprotein at the blood-brain barrier. To overcome imatinib mesylate–resistance mechanisms such as bcr-abl amplification, mutations within the ABL kinase domain, and activation of Lyn, we developed a dual BCR-ABL/Lyn inhibitor, INNO-406 (formerly NS-187), which is 25 to 55 times more potent than imatinib mesylate in vitro and at least 10 times more potent in vivo. The aim of this study was to investigate the efficacy of INNO-406 in treating CNS Ph+ leukemia. We found that INNO-406, like imatinib mesylate, is a substrate for P-glycoprotein. The concentrations of INNO-406 in the CNS were about 10% of those in the plasma. However, this residual concentration was enough to inhibit the growth of Ph+ leukemic cells which expressed not only wild-type but also mutated BCR-ABL in the murine CNS. Furthermore, cyclosporine A, a P-glycoprotein inhibitor, augmented the in vivo activity of INNO-406 against CNS Ph+ leukemia. These findings indicate that INNO-406 is a promising agent for the treatment of CNS Ph+ leukemia.

To determine the antitumor effect of arsenic trioxide (As2O3) on multidrug-resistant cells, we applied 3 human leukemia cell lines: daunorubicin (DNR)-resistant cell line K562/D1-9, which overexpresses p-glycoprotein (Pgp); DNR and 1-beta-D-arabinofuranosylcytosine (Ara-C) double-resistant cell line HL60/AD, which overexpresses multidrug resistance-associated protein (MRP1); and Bcl-2-transfected pre-B lineage leukemia cell line 697/Bcl-2. Interestingly, K562/D1-9 showed collateral sensitivity. Only HL60/AD showed small cross resistance, but 697/Bcl-2 had no resistance to As2O3. An intracellular content of glutathione (GSH) played a critical role in sensitivity to As2O3. Buthionine-sulfoximine (BSO), which reduces the GSH content, not only increased the As2O3 sensitivity but also conquered the MRP1-related cross resistance in HL60/AD. In conclusion, As2O3 was effective in all 3 cell lines, suggesting that As2O3 may be a promising agent for the treatment of multidrug-resistant leukemia.

Two antibiotics recommended by the guideline of Infectious Diseases Society of America (IDSA) were selected for treatment of febrile neutropenia, and these paired antibiotics were changed periodically three times. The clinical efficacy of each antibiotic was retrospectively evaluated at the end of the final period. There was no significant difference about efficacy rate between two kinds of antibiotics in the same sequential period. However, the efficacy rate has been rising and febrile duration has been shortening by degrees. Only a few drug resistant bacteria were recognized by the surveillance culture during antibiotic cycling. Recently, antibiotic cycling therapy has attracted attention especially in the ICU. However, a clinical study of treatment for febrile neutropenia has not been reported. Our trial suggests that cycling therapy may be useful for febrile neutropenia. However, Some deviation in the patients characteristics of each period may affect the result. It seems that further examination is necessary about usefullness of the cycling therapy for febrile neutropenia.

Imatinib mesylate, a competitive inhibitor of Abl tyrosine kinase, is highly effective for the early stages of chronic myelogenous leukemia (CML), but remissions induced in advanced-phase CML and Philadelphia chromosome-positive (Ph+) acute lymphoblastic leukemia tend to be relatively short-lived. Therefore, the search for agents that enhance the anti-Ph+ effect of imatinib mesylate is warranted. We investigated the combined effects of imatinib mesylate and the third-generation bisphosphonate zoledronate (ZOL) on Ph+ leukemias, because ZOL inhibited the prenylation of Ras-related proteins downstream of Bcr/Abl. First, we identified the potency of ZOL in vitro against human leukemic cell lines, including 2 Ph+ and a P-glycoprotein-overexpressing leukemic cell line. ZOL was also effective in vivo because as it prolonged the survival of nonobese diabetic/severe combined immunodeficient (NOD/SCID) mice who were given xenografts with Ph+ BV173 leukemic cells. Next, we showed the in vitro synergistic effects with ZOL and imatinib mesylate for Ph+ cell lines. ZOL combined with imatinib mesylate showed synergistic effects in vivo that prolonged the survival of mice inoculated with BV173. ZOL only minimally inhibited the growth of normal hematopoietic progenitors in vitro, and mice receiving ZOL or imatinib mesylate or both tolerated these treatments well. These findings indicate that ZOL is a potent antileukemic agent that augments synergistically the anti-Ph+ leukemia activity of imatinib mesylate.

To study the molecular mechanisms by which drug resistance develops, we compared DU145 humanprostate cancer cells with a subline selected for resistance to camptothecin. Differences in gene expression level were assessed by hybridizing the two cell types against each other using quadruplicate "Oncochip" cDNA microarrays that included 1648 cancer-related genes. Expression levels differing by a factor of1.5 were detected for 181 of the genes. These differences were judged statistically reliable on the basis of a stratum-adjusted Kruskal-Wallis test, after taking into account a dye-dependent variable. The 181 expression-altered genes included a larger than expected number of the "apoptosis-related" genes (P = 0.04). To assess whether this observation reflected a generalized resistance of RCO.1 to apoptosis, we exposed the cells to a range of stresses (cisplatin, staurosporine, UV, ionizing radiation, and serum starvation) and found greatly reduced apoptotic responses for RC0.1 (relative to DU145) using flow cytometric Annexin V and terminal deoxynucleotidyl transferase-mediated nick end labeling assays. We next examined the apoptosis-related genes in the context of a molecular interaction map and found expression differences in the direction "expected" on the basis of the apoptosis-resistance of RC0.1 for BAD, caspase-6, and genes that signal via the Akt pathway. Exposure of the cells to wortmannin, an inhibitor of the Akt effector phosphatidylinositol 3-kinase, provided functional support for involvement of the Akt pathway. However, closer examination of the molecular interaction map revealed a paradox: many of the expression differences observed for apoptosis-related genes were in the direction "contrary" to that expected given the resistance of RC0.1. The map indicated that most of these unexpected expression differences were associated with genes involved in the nuclear factor kappa B and transforming growth factor beta pathways. Overall, the patterns that emerged suggested a two-step model for the selection process that led to resistance in RC0.1 cells. The first hypothesized step would involve a decrease in apoptotic susceptibility through changes in the apoptosis-control machinery associated with the Bcl-2 and caspase gene families, and also in antiapoptotic pathways operating through Akt/PKB. The second step would involve changes in multifunctional upstream genes (including some genes in the nuclear factor kappa B and transforming growth factor beta pathways) that can facilitate apoptosis but that would also tend to contribute to cell proliferation in the presence of drug. Thus, we propose that a downstream blockade of apoptosis was "permissive" for the selection of upstream pathway changes that would otherwise have induced apoptosis. This model is analogous to one suggested previously for the relationship between oncogene function and apoptosis in carcinogenesis.

International audience; We previously isolated a 34-kDa nuclease (AN34) from apoptotic human leukemia cells. Here, we identify AN34 as an N-terminally truncated form of human AP endonuclease (Ape1) lacking residues 1-35 (delta35-Ape1). Although Ape1 has hitherto been considered specific for damaged DNA (specific to AP site), recombinant AN34 (delta35-Ape1) possesses significant endonuclease activity on undamaged (normal) DNA and in chromatin. AN34 also displays enhanced 3'-5' exonuclease activity. Caspase-3 activates AN34 in a cell-free system, although caspase-3 cannot cleave Ape1 directly in vitro. We also found that Ape1 itself preferentially cleaves damaged chromatin DNA isolated from cells treated with apoptotic stimuli and that silencing of Ape1 expression decreases apoptotic DNA fragmentation in DFF40/CAD-deficient cells. Thus, we propose that AN34 and Ape1 participate in the process of chromatin fragmentation during apoptosis.

International audience; While investigating the novel anticancer drug ecteinascidin 743 (Et743), a natural marine product isolated from the Caribbean sea squirt, we discovered a new cell-killing mechanism mediated by DNA nucleotide excision repair (NER). A cancer cell line selected for resistance to Et743 had chromosome alterations in a region that included the gene implicated in the hereditary disease xeroderma pigmentosum (XPG, also known as Ercc5). Complementation with wild-type XPG restored the drug sensitivity. Xeroderma pigmentosum cells deficient in the NER genes XPG, XPA, XPD or XPF were resistant to Et743, and sensitivity was restored by complementation with wild-type genes. Moreover, studies of cells deficient in XPC or in the genes implicated in Cockayne syndrome (CSA and CSB) indicated that the drug sensitivity is specifically dependent on the transcription-coupled pathway of NER. We found that Et743 interacts with the transcription-coupled NER machinery to induce lethal DNA strand breaks.

We examined the effect of PSC 833, a nonimmunosuppressive cyclosporin analogue, on the cytotoxicity, accumulation and retention of an anthraquinone antileukemia drug mitoxantrone (MIT). This was done in P-glycoprotein (PGP)-overexpressing multidrug-resistant K562/D1-9 cells and compared with the effect of cyclosporin A (CsA). We also compared MIT with the effect of PSC 833 on the cytotoxicity of daunorubicin (DNR) and doxorubicin (DOX). While PSC 833 and CsA had no effect on the cytotoxicity, accumulation and retention of MIT in the parent K562 cells, PSC 833 and CsA restored accumulation and retention of MIT in K562/D1-9 cells dose-dependently. Consequently, there was increased sensitivity of K562/D1-9 cells to MIT. The reversing activity of PSC 833 on the cytotoxicity of MIT was stronger than that of CsA, and was almost the same as the reversing activity of PSC 833 on the cytotoxicity of DNR and DOX. The resistance index of MIT decreased from 43.9-fold to 2.8-fold by 0.4 microM PSC 833, which is a clinically achievable plasma concentration. These results suggest that the combination of PSC 833 with MIT could be a promising treatment in reversing PGP-mediated MDR in leukemia patients.

A rare condition of enlargement of the mandibular canal caused by an extra-nodal non-Hodgkin's lymphoma in a 59-year-old Japanese woman was reported. The patient had a swelling of the hard palate and protrusion of both ocular bulbs, which had been present for 10 years. A panoramic radiograph revealed that the right mandibular canal was widely enlarged, extending from the mandibular foramen to the mental foramen, without bone destruction. The continuous dilation of the mandibular canal to an approximate 15-mm width was associated with peripheral bony sclerosis. Computed tomography and magnetic resonance imaging showed a soft tissue tumor inside the mandibular canal. The lesion demonstrated expansive growth in the orbits, extending to the skull base through the superior orbital fissures and cavernous sinus. The lymphoma was suspected to have grown so slowly that the adjacent mandibular canal and ocular bulbs enlarged without destroying the normal bone and nervous tissue.

1-β- d -Arabinofuranosylcytosine (Ara-C) is a nucleoside analog commonly used in the treatment of leukemias. Ara-C inhibits DNA polymerases and can be incorporated into DNA. Its mechanism of cytotoxicity is not fully understood. Using oligonucleotides and purified human topoisomerase I (top1), we found a 4- to 6-fold enhancement of top1 cleavage complexes when ara-C was incorporated at the +1 position (immediately 3′) relative to a unique top1 cleavage site. This enhancement was primarily due to a reversible inhibition of top1-mediated DNA religation. Because ara-C incorporation is known to alter base stacking and sugar puckering at the misincorporation site and at the neighboring base pairs, the observed inhibition of religation at the ara-C site suggests the importance of the alignment of the 5′-hydroxyl end for religation with the phosphate group of the top1 phosphotyrosine bond. This study also demonstrates that ara-C treatment and DNA incorporation trap top1 cleavage complexes in human leukemia cells. Finally, we report that camptothecin-resistant mouse P388/CPT45 cells with no detectable top1 are crossresistant to ara-C, which suggests that top1 poisoning is a potential mechanism for ara-C cytotoxicity.

We examined the effect of PSC 833, a non-immunosuppressive cyclosporin analogue, on the cytotoxicity, accumulation and retention of idarubicin (IDA) and its 13-dihydro metabolite, idarubicinol (IDAol). P-glycoprotein (PGP)-overexpressing multidrug-resistant K562/D1-9 cells were used for these studies. PSC 833 had no effect on the cytotoxicity, intracellular accumulation, or retention of IDA and IDAol in the parent K562 cells. However, intracellular accumulation of IDA and IDAol in K562/D1-9 cells after a 60-min incubation was restored by 0.4 microM PSC 833 to 104% and 116%, respectively, of the level in parent K562 cells. The retention of IDA and IDAol in K562/D1-9 cells was also restored by 0.4 microM PSC 833. Consequently, 0.4 microM PSC 833 increased the sensitivity of K562/D1-9 cells to IDA and IDAol. The resistance index (RI) of IDA decreased from 20-fold to 4.0-fold, and the RI of IDAol decreased from 104-fold to 1.5-fold. These results suggest that the combination of IDA and PSC 833 may be effective in reversing PGP-mediated multidrug resistance in leukemia cells.