Idarubicin and idarubicinol are less affected by topoisomerase II-related multidrug resistance than is daunorubicin

Influence of lipophilicity of anthracyclines on the interactions with cholesterol in the model cell membranes - Langmuir monolayer and SEIRAS studies

The interactions of anthracyclines with biological membranes strongly depend on the drug lipophilicity, which might also determine the specific affinity to cholesterol molecules. Therefore, in this work we show the studies concerning the effect of two selected anthracyclines, daunorubicin (DNR) and idarubicin (IDA) on simple models of healthy (DMPC:Chol 7:3) and cancer cells membranes with increased level of cholesterol (DMPC:Chol 3:7) as well as pure cholesterol monolayers prepared at the air-water interface and supported on gold surface. It has been shown that more lipophilic IDA is able to penetrate cholesterol monolayers more effectively than DNR due to the formation of IDA-cholesterol arrangements at the interface, as proved by the thermodynamic analysis of compression-expansion cycles. The increased interactions of IDA were also confirmed by the time measurements of pre-compressed monolayers exposed to drug solutions as well as grazing incidence X-ray diffraction studies demonstrating differences in the 2D organization of cholesterol monolayers. Langmuir studies of mixed DMPC:Chol membranes revealed the reorganization of molecules in the cancer cell models at the air-water interface at higher surface pressures due to the removal of DNR, while increased affinity of IDA towards cholesterol allowed this drug to penetrate the layer more efficiently without its removal. The SEIRAS spectra obtained for supported DMPC:Chol bilayers proved that IDA locates both in the ester group and in the acyl chain region of the bilayer, while DNR does not penetrate the membranes as deeply as IDA. The increased penetration of the mixed phospholipid layers by idarubicin might be attributed to the higher lipophilicity caused by the lack of methoxy group and resulting in a specific affinity towards cholesterol.

Mechanisms of drug resistance in acute myeloid leukemia

Acute myeloid leukemia (AML) is a kind of malignant hematopoietic system disease characterized by abnormal proliferation, poor cell differentiation, and infiltration of bone marrow, peripheral blood, or other tissues. To date, the first-line treatment of AML is still based on daunorubicin and cytosine arabinoside or idarubicin and cytosine arabinoside regimen. However, the complete remission rate of AML is still not optimistic, especially in elderly patients, and the recurrence rate after complete remission is still high. The resistance of leukemia cells to chemotherapy drugs becomes the main obstacle in the treatment of AML. At present, the research on the mechanisms of drug resistance in AML is very active. This article will elaborate on the main mechanisms of drug resistance currently being studied, including drug resistance-related proteins and enzymes, gene alterations, micro RNAs, and signal pathways.

Low-dose triptolide in combination with idarubicin induces apoptosis in AML leukemic stem-like KG1a cell line by modulation of the intrinsic and extrinsic factors

Leukemia stem cells (LSCs) are considered to be the main reason for relapse and are also regarded as a major hurdle for the success of acute myeloid leukemia chemotherapy. Thus, new drugs targeting LSCs are urgently needed. Triptolide (TPL) is cytotoxic to LSCs. Low dose of TPL enhances the cytotoxicity of idarubicin (IDA) in LSCs. In this study, the ability of TPL to induce apoptosis in leukemic stem cell (LSC)-like cells derived from acute myeloid leukemia cell line KG1a was investigated. LSC-like cells sorted from KG1a were subjected to cell cycle analysis and different treatments, and then followed by in vitro methyl thiazole tetrazolium bromide cytotoxicity assay. The effects of different drug combinations on cell viability, intracellular reactive-oxygen species (ROS) activity, colony-forming ability and apoptotic status were also examined. Combination index-isobologram analysis indicates a synergistic effect between TPL and IDA, which inhibits the colony-forming ability of LSC-like cells and induces their apoptosis. We further investigated the expression of Nrf2, HIF-1α and their downstream target genes. LSC-like cells treated with both TPL and IDA have increased levels of ROS, decreased expression of Nrf2 and HIF-1α pathways. Our findings indicate that the synergistic cytotoxicity of TPL and IDA in LSCs-like cells may attribute to both induction of ROS and inhibition of the Nrf2 and HIF-1α pathways.

Idarubicin is superior to daunorubicin in remission induction of de novo acute myeloid leukemia patients with high MDR1 expression

Aim: To investigate whether idarubicin in a cytarabine-based induction regimen was superior to daunorubicin in de novo acute myeloid leukemia patients expressing high MDR1. Patients & methods: The clinicopathological data were analyzed in 125 patients receiving daunorubicin or idarubicin with cytarabine for remission induction. Median MDR1 mRNA expression in pretreated bone marrow cells was used as the cutoff point for high and low MDR1 expression. Results: A total of 59.7% high and 77.8% low MDR1 expressers achieved complete remission (CR; p = 0.029). Idarubicin yielded a higher CR rate than daunorubicin in high MDR1 expressers (82.1 vs 41.2%; p = 0.001), it also demonstrated a higher CR rate than daunorubicin (p < 0.05) in high MDR1 expressers exhibiting favorable or intermediate risk, while there was no difference between the two treatment arms in low MDR1 expressers exhibiting either favorable or intermediate risk. Conclusion: Idarubicin is associated with better remission induction of de novo acute myeloid leukemia patients with high MDR1 expression.

Original submitted 23 May 2012; Revision submitted 10 October 2012

Involvement of P-glycoprotein in regulating cellular levels of Ginkgo flavonols: quercetin, kaempferol, and isorhamnetin

Quercetin, kaempferol, and isorhamnetin were the most important flavonoid constituents in extracts from Ginkgo biloba leaves. Transport studies of Ginkgo flavonols were performed in Caco-2 cell mono-layers. Their apparent permeability in absorptive and secretion directions was determined, and quercetin, kaempferol and isorhamnetin displayed polarized transport, with the Papp,B-A being higher than the Papp,A-B (P &lt; 0.01 for quercetin, P &lt; 0.001 for kaempferol and isorhamnetin, Student's t-test). Bcap37/MDR1 cells, which were transfected with a P-glycoprotein (P-gp) gene construct, were treated with quercetin, kaempferol or isorhamnetin. The concentrations of Ginkgo flavonol in Bcap37/MDR1 cells were lower than those in parent cells (P &lt; 0.05 for quercetin, P &lt; 0.01 for isorhamnetin, Mann-Whitney U test). The concentrations of the flavonol in transfected cells increased when incubated with the P-gp inhibitor verapamil (P &lt; 0.05 for kaempferol, Mann-Whitney U test). A colorometric assay for ATPase activity was applied to the detection of interaction of flavonol with P-gp. Quercetin and kaempferol inhibited the ATPase activity, and isorhamnetin stimulated the ATPase activity (P &lt; 0.05 for isorhamnetin, Mann Whitney U test). The results indicated that Ginkgo flavonols quercetin, kaempferol and isorhamnetin were substrates of P-gp. The P-gp type efflux pump might limit the bioavailability of Ginkgo flavonols.

Doxorubicin-resistant, MRP1-expressing U-1285 cells are sensitive to idarubicin

A doxorubicin-resistant subline (U-1285dox(900)) was derived from the human small cell lung carcinoma cell line U-1285. U-1285dox(900) was exposed to a wide range of anticancer agents to determine its resistance profile. In contrast to U-1285 cells, the resistant subline U-1285dox(900) expressed elevated MRP1 mRNA detected by reversed transcriptase-polymerase chain reaction (RT-PCR) and MRP1 protein analyzed with Western blot. Neither MDR1 mRNA nor P-glycoprotein could be detected in the parental cell line or resistant subline. U-1285dox(900) exhibited high resistance to doxorubicin, epirubicin, daunorubicin, and vincristine, an intermediate resistance to mitoxantrone, and a low resistance to etoposide. A collateral sensitivity to cytosine arabinoside, chlorodeoxyadenosine, and melphalan was observed. The resistance could be reversed by buthionine-sulphoximine and verapamil for all tested drugs. Compared with daunorubicin, resistance to idarubicin was very low, 14-fold and 2.6-fold, respectively. This was associated with a higher accumulation due to a slower transport of idarubicin out of U-1285dox(900) cells.

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.

A pharmacokinetic study of idarubicin in Japanese patients with malignant lymphoma: relationship with leukocytopenia and neutropenia

To clarify the pharmacokinetic properties of idarubicin (IDA) in Japanese patients and to clarify the relationship between the pharmacokinetic parameters of IDA or idarubicinol (IDAol), an active metabolite of IDA, and leukocytopenia or neutropenia, we examined the pharmacokinetics of IDA in patients with malignant lymphoma. Nine of 21 patients registered in an early phase II study of IDA were enrolled in the pharmacokinetic study. IDA (12 or 15 mg/m2) was administered by intravenous infusion for 5 minutes. The elimination half lives (t 1/2) of IDA were 11.0 hours and 12.5 hours after administration of 12 and 15 mg/m2 IDA, respectively. IDAol appeared rapidly both in plasma and in blood cells, and its concentrations exceeded those of IDA within 4 hours. IDAol had a very long t 1/2 (69.2 hours and 70.0 hours for 12 and 15 mg/m2, respectively). The areas under the concentration curves of IDAol in plasma were 3.4 and 5.8 times higher than those of IDA after administration of 12 and 15 mg/m2 IDA, respectively. The t 1/2 of IDAol in plasma correlated significantly with the nadir of neutrophils, and the steady-state volume of distribution of IDA in plasma and in blood cells correlated significantly with the nadirs of white blood cells and neutrophils. These results suggest that both IDA and IDAol play an important role in leukocytopenia or neutropenia. No substantial differences between Japanese and Caucasian people in the pharmacokinetics of IDA were apparent.

Effect of PSC 833 on the cytotoxicity of idarubicin and idarubicinol in multidrug-resistant K562 cells

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.