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The article analyzes the outcome of several cases of adult acute myeloid leukemia (AML) patients who were homogeneously treated with a fludarabine-based induction therapy. The study found a correlation between breast cancer resistance protein ABCG2 positivity and FMS-like tyrosine kinase 3 (FLT3) mutation. However, neither ABCG2 overexpression nor FLT3-internal tandem duplication (ITD) revealed any impact on achievement of complete remission (CR).

The treatment of relapsed adult acute lymphoblastic leukaemia (ALL) is frequently unsuccessful with current chemotherapy regimens, and often there is an overexpression of multidrug resistance (MDR)-related proteins. Liposomal encapsulation makes daunorubicin (DNR) less sensitive to the efflux effect of P-glycoprotein (PGP), and in vitro data indicate that liposomal-encapsulated DNR (Daunoxome-DNX) is more toxic than DNR against ALL cell lines. In this study, we assessed the in vivo and in vitro efficacy and toxicity of DNX plus cytarabine (Ara-C) as reinduction chemotherapy in 25 relapsed ALL patients (pts). The expression of MDR-related proteins (PGP, MRP1 and LRP) was also analysed. Of the 25 pts, 12 were males and 13 females; median age was 32 yr (range 18–58). Six cases were ALL T and 19 ALL B; eight pts were Ph+ (32%), and nine Bcr-Abl+ (36%). The expression of MDR-related proteins, and DNR and DNX retention and induction of apoptosis in leukaemic cells were evaluated in all cases. Seventeen of 25 (68%) pts were at first relapse and eight (32%) at second or subsequent relapse. The DNX was given in a dose of 80 mg/m2/d (days 1–3) in 11/25 pts (44%) and in a dose of 100 mg/m2/d (days 1–3) in 14/25 pts (66%). In all pts, Ara-C was administered in a dose of 2 g/m2 (days 1–5). Twenty pts (80%) achieved a complete remission (CR) and two (8%) entered a partial remission (PR) for an overall response (OR) rate of 88% (22/25), with a tolerable toxicity and without significant cardiotoxicity. Before the start of DNX therapy, 18/25 (72%) cases overexpressed at least one MDR-related protein compared with 9/25 (36%) cases with MDR overexpression at diagnosis ( P = 0.01). Taking into account the small number of cases, the response rate was not affected by MDR expression and the in vitro results also showed a higher uptake and apoptotic cell death by DNX compared with DNR. Twelve pts subsequently underwent allogeneic bone marrow transplantation (11 unrelated donor BMT, and one sibling BMT). The overall survival was 39% after 12 months. These data show the efficacy (OR rate 88% and CR rate 80%) of DNX plus Ara-C as reinduction therapy in very poor-risk ALL pts and the response rate seems not to be affected by MDR overexpression. Moreover, the high rate of remissions and the good clinical tolerance in heavily pretreated pts suggest a promising role of DNX in ALL chemotherapy regimens. [ABSTRACT FROM AUTHOR]

Most of the substances used as fluorescent probes to study drug transport and the effect of efflux blockers in multidrug resistant cells have many drawbacks, such as toxicity, unspecific background, accumulation in mitochondria. New fluorescent compounds, among which Bodipy‐FL‐verapamil (BV), have been therefore proposed as more useful tools. The uptake of BV has been evaluated by cytofluorimetry and fluorescence microscopy using cell lines that overexpress P‐glycoprotein (P388/ADR and LLC‐PK1/ADR) or MRP (multidrug resistance‐related protein) (PANC‐1) and clinical specimens from patients. The effect of specific inhibitors for P‐glycoprotein (verapamil and vinblastine) or MRP (MK571 and probenecid) has been also studied. BV intracellular concentrations were significantly lower in the two P‐glycoprotein overexpressing cell lines in comparison with the parental lines. In addition, verapamil and vinblastine increased the intracellular concentrations of the dye; MK571 and probenecid, two MRP inhibitors, increased BV levels in PANC‐1 cells, that express this protein. These findings were confirmed in clinical specimens from patients. Fluorescence microscopy revealed a faint fluorescence emission in P‐glycoprotein or MRP expressing cell lines; however, treatment with specific inhibitors significantly increased the fluorescence. BV is a useful tool for studying multidrug resistance proteins with different techniques such as cytofluorimetry and fluorescence microscopy, but does not discriminate between P‐glycoprotein and MRP. In comparison with other classic fluorescent probes, the assay with this dye is extremely rapid, simple, not toxic for cells, devoid of fluorescent background, and can be useful in the clinical settings. [ABSTRACT FROM AUTHOR]

Abstract: We report on a single-center experience about the characteristics and outcome of 36 acute promyelocytic leukemia (APL) patients observed at our Department of Hematology between 1990 and 2002. The expression, of multidrug-resistance (MDR) associated proteins (PGP, LRP, MRP1) was also analyzed. There were 12 males and 24 females (median age 37 yr), 89% (32 of 36) with classic morphology, and 11% (four of 36) with a microgranular variant. Risk class (according to GIMEMA/PETHEMA): 25% (nine of 36) high risk (HR), 53% (nineteen of 36) intermediate risk (IR), 22% (eight of 36) low risk (LR). PGP, LRP, and MRP1 expression at onset and at first relapse was low. CD33 antigen expression was high in all cases. The patients were treated according to GIMEMA protocols (LAP0389 and AIDA) including ATRA in induction in 75% (27 of 36) of cases and 94% (34 of 36) achieved a complete remission (CR) after induction therapy while 6% (two of 36) died early (DDI) of hemorrhage. Outcome: 71% (24 of 34) of evaluable patients remain in CR at a median follow-up of 57 months (range 4–158 months) while 29% (10 of 34) relapsed at a median time of 12 months (range 8–43 months) and, of them, eight of 10 died early. The majority of patients that relapsed were in high-risk group. The overall survival (OS) of the whole population at 32 months was 66% and the DFS at 42 months was 62%. A statistically significant difference in terms of DFS was observed between HR and IR/LR patients (P = 0.04 by log-rank). DFS was not affected by age, sex, Hb levels, karyotype, and BCR isoform. At conclusion, our data confirm that despite the high rate of success with ATRA plus chemotherapy as induction (more than 90% of CR), about 30% of APL patients have a relapse (without a long-lasting second remission) and underline the importance of patient stratification in distinct risk groups at diagnosis in order to better adapt the type and intensity of treatment (risk-adapted therapy). Taking into... [ABSTRACT FROM AUTHOR]

We analysed the expression of three drug transporter proteins [p-glycoprotein (PGP), lung resistance-related protein (LRP) and multidrug resistance-associated protein (MRP1)] involved in anthracycline resistance that are frequently overexpressed in poor-risk adult acute non-lymphocytic leukaemia (ANLL), in 23 acute promyelocytic leukaemia (APL) patients at onset managed at a single institution. Cellular daunorubicin accumulation was also evaluated. At onset, no case had PGP or MRP1 expression that exceeded that of non-multidrug-resistant (MDR) cell lines. Only one case showed LRP overexpression. No peculiar MDR features distinguished the seven patients who relapsed from those who maintained complete remission. In the onset vs. first relapse, only one patient showed an increased (threefold) PGP expression at relapse. At second relapse, three out of four patients showed a PGP expression two- to threefold higher than baseline values. These results are consistent with the view that low PGP, LRP and MRP1 expression and the absence of defects in intracellular drug accumulation may account for the peculiarly high sensitivity of APLs to anthracycline. It does not support the screening of MDR markers in APL patients at onset as predicting factors of early relapse. The results suggest that no significant changes in PGP, LRP or MRP1 expression are likely to occur at first relapse. In contrast, PGP expression is likely to increase later in the patient history as a result of additional chemotherapy courses. [ABSTRACT FROM AUTHOR]

The possibility that Daunoxome (DNX), a combination of daunorubicin (DNR) with a liposomal targeting system, escapes PGP was tested. Two pairs of leukaemic cell lines, each consisting of the parental non-multidrug resistance (MDR) line and of a MDR variant, were studied for cytotoxicity (MTT test) and for cellular DNR kinetic and accumulation (flow cytometry). DNX and free DNR were equally toxic against non-MDR cells, whereas the liposomal anthracycline was more toxic than the free drug against the MDR variant. Non-MDR cells accumulated DNR more rapidly when they were exposed to free DNR than to DNX, but MDR cells accumulated more DNR when they were exposed to DNX. The kinetics of DNX and free DNR were also studied in the blast cells of 41 cases of acute leukaemia and they were found to be related to blast cell PGP expression. In 15 cases with a low PGP expression intracellular DNR accumulation was faster and higher with free DNR than with DNX. In 26 cases with a high PGP expression the area under the curve was similar with DNX and free DNR, but the kinetics of intracellular DNR accumulation showed an early low plateau with free DNR and a slow and continuous increase with DNX. In MDR cell lines the ratio was more favourable to DNX than to free DNR. We conclude that liposome encapsulated DNR is partially protected from PGP and that it is worth testing for the treatment of PGP-positive acute leukaemia. [ABSTRACT FROM AUTHOR]

Examines the inhibitory effects of amifostine on the toxicity of anthracycline derivatives on multidrug resistance (MDR) tumor cell lines. Therapeutic use of the derivatives on leukemia; Analysis on the P-glycoprotein and multidrug related protein overexpressions; Assessment on the active metabolite of amifostine.

Abstract: Over-expression of multidrug resistance (MDR) proteins PGP and BCRP has a negative prognostic impact in acute myeloid leukemia (AML) patients. Inclusion of fludarabine in induction chemotherapy increases remission rate in PGP over-expressing cases. We investigated the role of BCRP in 138 adult AML patients receiving induction therapy with fludarabine. None of the MDR-related proteins influenced complete remission attainment. Conversely, high levels of BCRP significantly affected disease-free survival, as higher relapse rates (48.5% vs 28.5%) and earlier relapse occurred in BCRP+ patients. Also overall survival was affected by BCRP positivity, and survival significantly worsened in case of concomitant PGP and BCRP over-expression. [Copyright &y& Elsevier]