P-glycoprotein and terminal transferase expression identify prognostic subsets within cytogenetic risk classes in acute myeloid leukemia

Identification of prognostic subgroups among acute myeloid leukemia patients with intermediate risk cytogenetics using a flow-cytometry-based assessment of ABC-transporter function

BACKGROUND

A median fluorescence intensity ratio (MFIR) which measures the efflux of mitoxantrone (an ATP Binding Cassette (ABC) transporter substrate) with and without ABC transporter inhibition correlates with expression of MDR1 and BCRP in acute myeloid leukemia (AML) blasts.

METHODS

This study evaluates the impacts of the MFIR on AML outcomes and its interaction with detection of the FLT3 ITD.

RESULTS

Among 200 newly diagnosed AML patients, an MFIR of ≥ 1.9 (MFIR+) was detected in 60 (30%) leukemic blast samples. In multivariate analysis, MFIR was an independent prognostic factor for response to induction chemotherapy (OR=7.2, P<0.00001), DFS (HR=2.3, P=0.004) and OS (HR=2.2, P=0.0005) with the main effect being in the 141 patients with intermediate risk cytogenetics. Among intermediate risk cytogenetics patients: MFIR+ outcomes were similar to unfavorable cytogenetic risk (CR, 53% vs. 52%, P=1.0; OS, 11 vs. 9 months, P=0.79). MFIR status can further stratify the prognostic risk for patients with or without FLT3 ITD mutation.

CONCLUSIONS

MFIR has value in predicting outcomes including DFS and OS as well as induction failure. This is particularly true for patients with intermediate risk cytogenetics and when combined with assessment for the FLT3-ITD mutation.

Analysis of the interaction of induction regimens with p-glycoprotein expression in patients with acute myeloid leukaemia: results from the MRC AML15 trial

Retrospective analyses in non-randomised cohorts suggest that regimens containing fludarabine/Ara C and/or idarubicin/ara C may be more effective than daunorubicin/AraC (DA)-containing regimens in cases of acute myeloid leukaemia (AML) overexpressing p-glycoprotein (Pgp). We prospectively measured Pgp protein and function by flow cytometry in CD45-gated blasts from 434 AML15 trial patients randomised to remission induction therapy with two courses of FLAG-Ida or DA±etoposide (DA/ADE). In all, 34% were positive for Pgp protein and 38% for function. Pgp protein-positive cases had a higher incidence of resistant disease (14% vs 5%), adjusted odds ratio 2.67 (1.14–6.24). There was a trend towards a higher cumulative incidence of relapse at 5 years for Pgp-positive cases (46% vs 55%), adjusted hazard ratio 1.42 (0.98–2.07) (P=0.06). For patients treated with FLAG-Ida, the complete remission (CR) rate was 86% for both Pgp-positive and Pgp-negative patients. In patients treated with DA/ADE, 78% of Pgp-positive and 90% of Pgp-negative cases achieved CR (P=0.06). In analyses of overall survival, there was no interaction between treatment received and Pgp expression. Data for Pgp function followed similar trends. Our data suggest that FLAG-Ida may improve the remission rate for Pgp-positive AML, but the malignant clone is reduced rather than eradicated such that the relapse rate remains high in Pgp-positive patients.

Pim-1 expression and monoclonal antibody targeting in human leukemia cell lines

OBJECTIVE

Based on our previous findings that Pim-1 was expressed on the cell surface and could be targeted with a highly specific anti-Pim-1 monoclonal antibody (P9), this study aims to evaluate the possibility that Pim-1 could be targeted for the treatment of human leukemia.

MATERIALS AND METHODS

Pim-1 expression was investigated in a series of human leukemia cell lines with immunohistochemistry and flow cytometry. The inhibitory effect of P9 on cell proliferation was evaluated with (3)H-thymidine incorporation assay. Cell apoptosis was assayed with Annexin-V/propidium iodide dual staining. The in vivo effect of P9 was evaluated with xenograft tumor models in severe combined immunodeficient mice.

RESULTS

Pim-1 expression varied depending on the cell lines and correlated with the inhibitory effects mediated by P9. An association between Pim-1 expression and drug resistance was observed. Although the drug-resistant CEM/A7R cells were highly resistant to cytotoxic P-glycoprotein substrates, their growth was inhibited by P9 as demonstrated by in vitro proliferation assay and in vivo inhibition of xenograft tumors. P9 had little effect on P-glycoprotein expression and intracellular Rhodamine 123 accumulation, but it inhibited the phosphorylation of Bad and induced apoptosis.

CONCLUSIONS

Pim-1 is variably expressed in leukemia cell lines and associated with drug resistance. Targeting Pim-1 with monoclonal antibody could be explored for the treatment of leukemia and may represent a novel strategy to overcome drug resistance.

Prognostic scoring model based on multi-drug resistance status and cytogenetics in adult patients with acute myeloid leukemia

Clinical heterogenicity exists within an acute myeloid leukemia (AML) patient group with the same cytogenetic risk. Multi-drug resistance (MDR) is also regarded as one of the potential prognostic factors for AML. Accordingly, the prognostic scoring model can be generated based on both consideration of cytogenetic risk and the MDR status for AML. The CR rate, event-free (EFS) and overall survival (OS) were analysed according to cytogenetic risk, MDR status and clinical factors. Prognostic score was calculated by the sum of MDR status (0 for negative, 1 for positive) and dichotomized scoring for cytogenetic risk (0 for favorable/intermediate and 1 for unfavorable cytogenetics). MDR expression was noted in 36.6% of the patients and associated with a lower CR rate (p = 0.037). MDR, cytogenetics and the use of SCT were identified as independent prognostic factors for EFS and OS. The CR rate of the group scored with 0, 1 and 2 was 81.4, 66.7, and 44.4%, respectively (p = 0.050). The prognostic scoring model depicted a discriminating role in terms of EFS (p < 0.0001) and OS (p = 0.0001). The prognostic scoring model based on cytogenetic risk and MDR provided an improved method for evaluating the prognosis in AML and helped to stratify the risk of patients with the same cytogenetic risk.

MDR1 and BCRP1 expression in leukemic progenitors correlates with chemotherapy response in acute myeloid leukemia

OBJECTIVE

Overexpression of members of the adenosine triphosphate binding cassette (ABC) transporter superfamily has been implicated in multidrug resistance in cancer, but results in acute myeloid leukemia (AML) have been inconsistent. We investigated the expression and activity of ABC transporters in patient total blasts and subpopulations along the leukemic stem cell hierarchy.

MATERIALS AND METHODS

Using quantitative reverse transcriptase polymerase chain reaction, we measured expression of the ABC transporter superfamily in the blast cells from AML patients prior to chemotherapy. In addition, we measured ex vivo daunorubicin resistance of subpopulations with or without ABC inhibitors.

RESULTS

In the total blasts, no consistent difference was observed in 18 patients achieving complete remission (CR) and 13 patients who were refractory to induction chemotherapy (NR). However, among the subpopulation of CD34(+)CD38(-) AML cells (candidate "leukemic stem cells"), elevated expression of MDR1 and/or BCRP1, two ABC transporters associated with drug resistance, was found in 8 of 10 NR patients as compared to 0 of 7 CR patients. No such association was observed in the more differentiated CD34(+)CD38(+) or CD34(-) subpopulations. There was no significant difference in MRP1 expression between CR and NR patient samples in any of the subpopulations examined. The increased expression of MDR1 and BCRP1 in leukemic cells correlated with increased cellular daunorubicin resistance, which could be reversed by the ABC transporter inhibitors verapamil and PSC-833.

CONCLUSION

Expression of MDR1 and BCRP1 in leukemic stem cells correlates with chemotherapy response both at the cellular level and in AML patients.

Expression of the MDR1 gene and P-glycoprotein in canine mast cell tumor cell lines

Cellular drug resistance to antineoplastic drugs is often due to the presence of a drug efflux pump that reduces intracellular drug accumulation and chemosensitivity. P-glycoprotein (P-gp), which is encoded by the MDR1 gene, is considered to function as an ATP-driven membrane drug efflux pump and appears to play an important role in tumor cell resistance. In the present report, we assessed the expression of MDR1 by RT-PCR in three canine mast cell tumor cell lines, TiMC, CoMS and LuMC, originating from a cutaneous tumor, an oral-mucosal tumor and a gastrointestinal tumor, respectively. P-gp expression was also examined by Western blot analysis, while the functional activity of P-gp was assessed by flowcytometric analysis of intracellular rhodamine-123 (Rhd-123) uptake. The results revealed that MDR1 gene and P-gp were both expressed in CoMS and LuMC cells, whereas neither was present in TiMC cells. In CoMS and LuMC cells, intracellular uptake of Rhd-123 increased in the presence of verapamil, a functional modulator of P-gp. In contrast, TiMC cells did not show any changes in the intracellular accumulation of Rhd-123 after the verapamil addition. These findings suggest that the expressions of MDR1 gene and P-gp probably contribute to cellular drug resistance in canine mast cell tumors.

MRP3, BCRP, and P-glycoprotein activities are prognostic factors in adult acute myeloid leukemia

PURPOSE

P-Glycoprotein (Pgp) is associated with poor outcome in acute myeloid leukemia (AML). We have investigated other ATP-binding cassette proteins such as BCRP, MRP1, MRP2, MRP3, and MRP5 for their potential implication in chemoresistance.

EXPERIMENTAL DESIGN AND RESULTS

Eighty five AML patient samples were analyzed in this study. First, MRP3 function was higher in patients which had a high level of leukocytes (P = 0.01), a M5 FAB subtype (P = 0.04), and an intermediate or poor cytogenesis (P = 0.05). BCRP activity was not correlated with clinical or biological variables, but high Pgp activity was correlated with the following variables: CD34 expression (P = 0.002), FAB subtype (P = 0.002), intermediate or poor cytogenesis (P = 0.02), and elderly patients (P = 0.03). Second, Pgp, MRP3, and BCRP activities were correlated with complete remission (P = 0.02, P = 0.04, and P = 0.04, respectively), disease-free survival (P = 0.02, P = 0.03, and P = 0.25, respectively), and overall survival (P = 0.04, P = 0.04, and P = 0.05, respectively) in multivariate analysis. The patient samples expressing one or none of these Pgp, MRP3, or BCRP functional proteins have a better prognosis than the patients expressing two or three of these functional proteins (complete remission, P = 0.02; disease-free survival, P = 0.01; overall survival, P < 0.001).

CONCLUSIONS

BCRP and MRP3 may also be involved in chemoresistance in AML, especially MRP3 in patients with M5 FAB. Additional modulation of BCRP or MRP3 to Pgp modulation may be necessary in some patients in order to improve the treatment outcome.

Expression dynamics of drug resistance genes, multidrug resistance 1 (MDR1) and lung resistance protein (LRP) during the evolution of overt leukemia in myelodysplastic syndromes

It is well-known that leukemic cells of overt leukemia (OL) that have transformed from myelodysplastic syndromes (MDS) are more resistant to chemotherapy as compared with de novo AML cells. Thus, to examine the expression levels of drug-resistant genes and their alterations with the development of OL in MDS, the expression of mRNA for MDR1 and LRP was determined in bone marrow samples from control, de novo AML, MDS, MDS at the time of OL transformation (MDS --> OL), and after transformation (OL) by quantitative real-time RT-PCR. The expression of MDR1 in MDS bone marrow at the time of initial diagnosis was as low as that for control subjects. However, the expression level was significantly elevated at the time of the development of OL (MDS --> OL) compared with the initial MDS subjects (P < 0.05), while expression was relatively reduced after OL development (OL). The expression of LRP was significantly higher in MDS and MDS --> OL samples than control subjects. However, the high expression of LRP in MDS --> OL was significantly reduced after OL development (OL). The expression levels of drug-resistant genes in MDS --> OL or OL were not significantly higher than those of de novo AML samples, although LRP expression in MDS or MDS --> OL was relatively higher than that of de novo AML. Detecting increases in the expression of MDR1 would be useful for predicting OL development in MDS patients.

Major improvement of the reference method of the French drug resistance network for P-glycoprotein detection in human haematological malignancies

The aim of this study was to improve significantly the sensitivity and specificity of the flow cytometric assay of P-glycoprotein (Pgp) implemented and validated by the laboratories of the French Drug Resistance Network [Huet S, Marie JP, Gualde N, Robert J. Reference method for detection of Pgp mediated multidrug resistance in human hematological malignancies: a method validated by the laboratories of the French Drug Resistance Network. Cytometry 1998;34:248-56] in cells displaying low level of resistance. Fluoresceine-conjugated monoclonal antibodies (Mabs) and propidium iodide were respectively replaced by phycoerythrin-conjugated Mabs and Sytox green. The removal of erythrocytes and granulocytes by density gradient was replaced by the lysis of erythrocytes after Mab incubation. Using these conditions, Pgp could be detected in the K-H30 line, which was negative in former studies, with Mab/Control ratios increasing by 3.7- to 5.9-fold, and Mab/Control ratios in the parental sensitive K562 line still ranging between 0.8 and 1.2. When tested on 16 blood samples from patients presenting haematological malignancies, six samples presented low positivity, which was not detected with the former method, while 10 samples remained negative with the two methods. Pgp was specifically detected in pathological blood cells in the six positive samples.

Breast cancer resistance protein and P-glycoprotein in 149 adult acute myeloid leukemias

PURPOSE

Recently, a new ABC protein, breast cancer resistance protein (BCRP), was described. But its prognosis is not known in acute myeloid leukemia (AML). In addition, the prognosis of P-glycoprotein (Pgp) and BCRP in patients treated homogeneously by the same anthracycline (daunorubicin, idarubicin, or mitoxantrone) during all of the treatment with aracytine is not known. Therefore, we have evaluated the relationship between drug resistance phenotype, in vitro anthracene sensitivity, and the relation to treatment outcome.

EXPERIMENTAL DESIGN

We have analyzed 149 AML treated according to protocol of the European Organization for Research and Treatment of Cancer group. The prognostic value of BCRP and Pgp were analyzed in the whole population and according to intercalating agent.

RESULTS

BCRP was a prognostic factor, for achievement of complete remission (43% in positive patients and 69% in negative patients, P = 0.005), the 4-year disease-free survival (12% versus 33%, P = 0.03), and the 4-year overall survival (19% versus 38%, P = 0.003). When BCRP expression and Pgp function were categorized in three groups, +/+, +/- or -/+, and -/-, the achievement of complete remission was 45%, 66%, and 90% (P = 0.0003), the 4-year disease-free survival was 8%, 26%, and 40% (P = 0.01), and the 4-year overall survival was 16%, 37%, and 48% (P = 0.001), respectively. Pgp function was a prognostic factor in patients treated by daunorubicin and idarubicin but not by mitoxantrone. In contrast, BCRP expression was a prognostic factor in patients treated by daunorubicin and mitoxantrone but not by idarubicin.

CONCLUSIONS

BCRP would be implicated in the resistance to chemotherapies in AML. But these are the patients expressing both BCRP and Pgp who have the poorest prognosis.

Multidrug resistance as a potential prognostic indicator in acute myeloid leukemia with normal karyotypes

INTRODUCTION

Approximately 45% of adults with acute myeloid leukemia (AML) have normal karyotypes and therefore lack structural abnormalities that can assist in the localization and characterization of molecular defects. The current study attempted to evaluate the potential prognostic role of multidrug resistance (MDR), regarded as one of the potential prognostic factors for the outcome of overall AML, for AML with normal karyotypes.

METHOD AND MATERIALS

A functional MDR assay was performed in pretreatment samples from AML patients with normal karyotypes. The complete remission (CR) rate, event-free survival (EFS), and overall survival (OS) were analyzed according to the MDR status and clinical prognostic factors for 88 patients with AML with normal karyotypes.

RESULTS

MDR by efflux was expressed in 14 out of 48 evaluable patients (29%) but failed to identify the association with CR (p = 0.124). However, MDR was identified as an independent prognostic factor for EFS and OS (p = 0.013 and 0.046) together with the use of stem cell transplantation (p = 0.009 for EFS and 0.029 for OS) and the WBC count at presentation (p = 0.023 for EFS and 0.034 for OS).

CONCLUSION

The functional MDR assay may provide information on the prognosis of AML patients with normal karyotypes, and it might be a possible guideline for risk-stratified treatment strategies in AML with normal karyotypes.

Ajoene (natural garlic compound): a new anti-leukaemia agent for AML therapy

The reputation of garlic (Allium sativum) as an effective remedy for tumours extends back to the Egyptian Codex Ebers of 1550 b.c. Several garlic compounds including allicin and its corresponding sulfide inhibit the proliferation and induce apoptosis of several human non-leukaemia malignant cells including breast, bladder, colorectal, hepatic, prostate cancer, lymphoma and skin tumour cell lines. Ajoene (4,5,9-trithiadodeca-1,6,11-triene-9-oxide) is a garlic-derived compound produced most efficiently from pure allicin and has the advantage of a greater chemical stability than allicin. Several clinical trials and in vitro studies of ajoene have demonstrated its best-known anti-thrombosis, anti-microbial and cholesterol lowering activities. Recently, topic application of ajoene has produced significant clinical response in patients with skin basal cell carcinoma. Ajoene was shown to inhibit proliferation and induce apoptosis of several human leukaemia CD34-negative cells including HL-60, U937, HEL and OCIM-1. Also, ajoene induces 30% apoptosis in myeloblasts from chronic myeloid leukaemia patient in blast crisis. More significantly, ajoene profoundly enhanced the apoptotic effect of the two chemotherapeutic drugs: cytarabine and fludarabine in human CD34-positive resistant myeloid leukaemia cells through enhancing their bcl-2 inhibitory and caspase-3 activation activities. The two key anti-leukaemia biological actions of ajoene were the inhibition of proliferation and the induction of apoptosis. Studies have shown the anti-proliferation activity of ajoene to be associated with a block in the G2/M phase of cell cycle in human myeloid leukaemia cells. The apoptosis inducing activity of ajoene is via the mitochondria-dependent caspase cascade through a significant reduction of the anti-apoptotic bcl-2 that results in release of cytochrome c and the activation of caspase-3. Since acute myeloid leukaemia (AML) is a heterogeneous malignant disease in which disease progression at the level of CD34-positive cells has a major impact on resistance to chemotherapy and relapse and the inability to undergo apoptosis is a crucial mechanism of multi-drug resistance in AML patients. The recent findings of the potent enhancing activity of ajoene on chemotherapy-induced apoptosis in CD34-positive resistant human myeloid leukaemia cells suggest a novel promising role for the treatment of refractory and/or relapsed AML patients as well as elderly AML patients. Further studies are warranted to evaluate similar enhancing effect for ajoene in blast cells from AML patients in primary cultures before its introduction in pilot clinical study.

CD90/Thy-1 is preferentially expressed on blast cells of high risk acute myeloid leukaemias

Different transformation mechanisms have been proposed for elderly acute myeloid leukaemia (AML) and secondary AML (sAML) when compared with de novo AML or AML of younger patients. However, little is known regarding differences in the immunophenotypic profile of blast cells in these diseases. We systematically analysed, by flow cytometry, 148 patients affected by de novo (100 cases) or sAML (48 cases). By defining a cut-off level of 20% of CD34+ cells co-expressing CD90, the frequency of CD90+ cases was higher in sAML (40%) versus de novo AML (6%, P < 0.001), elderly AML (>60 years) (24%) versus AML of younger patients (10%, P = 0.010) and poor- versus good-risk karyotypes (according to the Medical Research Council classification, P < 0.001). The correlation between CD90 expression, sAML and unfavourable karyotypes was confirmed by analysing the subset of CD34+ AML cases alone (91/148). Consistently, univariate analysis showed that expression of CD90 was statistically relevant in predicting a shorter survival in CD90+ AML patients (P = 0.042). Our results, demonstrating CD90 expression in AML with unfavourable clinical and biological features, suggest an origin of these diseases from a CD90-expressing haemopoietic progenitor and indicate the use of CD90 as an additional marker of prognostic value in AML.

Cytogenetic findings in adult de novo acute myeloid leukaemia. A population-based study of 303/337 patients

During a 10-year period (1992-2001) in the region of Southern Denmark, 337 patients aged 15 years or older (range 16-93 years, median 67 years) were diagnosed with acute myeloid leukaemia (AML). Cytogenetic analysis was carried out in 90%, of whom 53% had clonal chromosome aberrations. Some 24% and 31% had only numerical or structural abnormalities respectively. The remaining patients showed both types of abnormalities. Ploidy levels in decreasing order were: pseudodiploidy, 41%; hyperdiploidy, 32%; and hypodiploidy, 27%. Pseudodiploidy characterizes type M3 (70%) and hypodiploidy M6 (56%). Recurrent cytogenetic abnormalities--t(8;21), t(15;17) and inv(16)--were found in 3.3%, 3.3% and 2.0% of all patients respectively. Prognostically intermediate and adverse aberrations were found in 39% and 44%, respectively, of those with an abnormal karyotype. Rare recurrent aberrations were found in two patients in this material. A previously described non-recurrent abnormality was found to be recurrent in one patient [der(20)t(11;20)(q13.2;p13)]. New, previously undescribed abnormalities were found in 41 patients. Statistically significant correlations were found between t(15;17) and young age (P < 0.001), inv(16) and young age (P < 0.006), -17 and M6 (P = 0.007), and M6 and complex karyotype with five or more unrelated aberrations (P = 0.004). We conclude that this truly population-based cytogenetic study of adult AML showed distributions of chromosome abnormalities that differ from those described so far.

Autologous stem-cell transplantation for patients with acute myeloid leukemia aged over 60 yr

OBJECTIVES

Preliminary reports have suggested that autologous stem-cell transplantation (ASCT) is feasible in elderly patients with acute myeloid leukemia (AML). The objective of this study was to describe the disease characteristics and treatment results from a series of 22 elderly AML patients undergoing ASCT.

METHODS

The median age was 64 yr (range 61-71). Twenty patients were in first complete remission (CR1), two in CR2, and all were in performance status 0-1. The median interval between CR achievement and ACST was 3 months (range 2-5). In 20 cases peripheral blood stem cells were infused, in two bone marrow.

RESULTS

All patients had a successful engrafment. One patient (5%) died from transplant-related complications. The median number of days to granulocytes > 500 mm-3 and platelets > 20 000 mm-3 was 11(range 9-15) and 13 (range 9-20), respectively. Non-hematologic toxicity included WHO grade III-IV stomatitis in 32% patients and grade IV nausea and vomiting in one (4.5%). Seven patients had fever of unknown origin, while in 14 a documented infection was diagnosed. Median duration of hospitalization was 31 d (range 16-60).

CONCLUSIONS

After a median follow-up of 12 months from ASCT, nine patients are alive in continuous CR and 13 died from AML relapse. Median survival from diagnosis and disease-free survival (DFS) was 19 and 14 months, respectively. Our data show that ASCT with a standard conditioning regimen is feasible in AML patients aged more than 60 yr. Toxicity and hemopoietic recovery do not substantially differ from those observed in young adults. DFS and overall survival (OS) duration are encouraging, but a longer follow up is needed on a larger series of patients.

P-glycoprotein in acute myeloid leukaemia: therapeutic implications of its association with both a multidrug-resistant and an apoptosis-resistant phenotype

P-glycoprotein (Pgp) expression is an independent prognostic factor for response to remission-induction chemotherapy in acute myeloblastic leukaemia, particularly in the elderly. There are several potential agents for modulating Pgp-mediated multi-drug resistance, such as cyclosporin A and PSC833, which are currently being evaluated in clinical trials. An alternative therapeutic strategy is to increase the use of drugs which are unaffected by Pgp. However, in this review, we explain why this may be more difficult than it appears. Evidence from in vitro studies of primary AML blasts supports the commonly held supposition that chemoresistance may be linked to apoptosis-resistance. We have found that Pgp has a drug-independent role in the inhibition of in vitro apoptosis in AML blasts. Modulation of cytokine efflux, signalling lipids and intracellular pH have all been suggested as ways by which Pgp may affect cellular resistance to apoptosis; these are discussed in this review. For a chemosensitising agent to be successful, it may be more important for it to enhance apoptosis than to increase drug uptake.

The role of drug efflux pumps in acute myeloid leukemia

A major problem in the treatment of patients with acute myeloid leukemia (AML) is the occurrence of resistance to structurally and functionally unrelated chemotherapeutic agents, called multidrug resistance (MDR). One of the known MDR mechanisms is the overexpression of adenosine triphosphate (ATP)-dependent efflux pumps. Permeability-glycoprotein (P-gp), the best characterized of the human drug efflux pumps, has been shown to be associated with poor treatment outcome in AML patients. Besides P-gp, in addition the multidrug resistance protein 1 (MRP1) appeared to contribute to the observed resistance in AML. Alternative transporter proteins, such as the MRP1 homologues MRP2, MRP3, MRP5 and MRP6, and the breast cancer resistance protein (BCRP), have been shown to be expressed at variable levels in AML patient cells. The latter proteins have been described to confer resistance to chemotherapeutic agents, such as daunorubicin, mitoxantrone, etoposide and 6-mercaptopurine, which are generally used in the treatment of AML patients; however, theyhave not yet proven to play a role in drug resistance in AML. The present review gives an overview of the current knowledge concerning these drug transporters, with a focus on the role of the transporter proteins in AML.

Clinical relevance of minimal residual disease detection in adult acute myeloid leukemia

We have used flow cytometry to quantify minimal residual disease (MRD) in 63 patients with acute myeloid leukemia (AML). No significant correlation was found between the level of MRD after induction and disease outcome. After consolidation, a threshold of 3.5 x 10(-4) residual leukemic cells divided the 57 evaluable patients into two distinct groups: the MRDCons(+) and the MRDCons(-) group, with a relapse rate of 81% (22/27) and 27% (8/30), respectively (p = 0.000035). Although not correlated with prognosis, the level of MRD after induction course affected the degree of cytoreduction achieved with consolidation. In fact, the patients who entered a MRDCons(-) status had a median number of leukemic residual cells of 1.8 x 10(-4) after induction; at the same stage, the bone marrow of patients who were in a MRDCons(+) condition harbored a median level of 1.7 x 10(-3) malignant residual cells (p = 0.00073). The MRDCons(+) status also correlated significantly with poor/intermediate risk cytogenetics, MDR1 phenotype, short duration of overall survival, and relapse-free survival (p = 0.024, 0.021, 0.00001, and 0.00001, respectively). In multivariate analysis, the MRDCons(+) status was associated with a high probability of relapse (p < 0.00026) and short duration of relapse free survival (p = 0.008). Stem cell transplantation did not seem to alter the prognostic impact of high levels of MRD after consolidation: within the MRDCons(+) group, the relapse rate after transplant was 78%. Thus, a MRD > or = 3.5 x 10(-4) leukemic cells at the end of consolidation strongly predicts relapse, and is significantly associated with MDR1-positive phenotype and intermediate/unfavorable cytogenetics.

Acute myeloid leukemia in the elderly: biology and therapeutic strategies

Age represents one of the most important adverse prognostic factors in acute myeloid leukemia (AML). The therapeutic results for patients older than 60 years accrued into clinical trials of intensive chemotherapy are largely unsatisfactory (complete remission rates rarely superior to 50-60%; median relapse-free survival usually less than 12 months). Because only 30-40% of elderly patients are actually entered into these trials, the overall failure of current treatments appear even more disappointing when considered in the context of the whole population of older individuals with AML. This appears primarily due to intrinsic differences in the biology of leukemia itself and to host-related factors (i.e. reduced tolerance to chemotherapy and comorbidity). AMLs of older subjects display several biological overlaps with secondary AMLs including multilineage involvement, phenotype, unfavorable cytogenetics and elevated activity of multidrug resistance genes. The clinical application of biologically-based prognostic factors may enable to separate patients who may actually benefit from aggressive chemotherapy from those who should be offered attenuated/palliative treatments or enrolled upfront into experimental trials of new drugs or biologic/immunologic treatments. This may hopefully result in a 'risk-adapted' strategy aimed at improving disease free survival and/or quality of life for patients with differing risk profiles.

Significant association between expression of the CD11b surface molecule and favorable outcome for patients with acute myeloblastic leukemia

The expression of several myeloid and non-lineage associated surface antigens in 70 patients with acute myeloblastic leukemia was investigated in relation to patient and disease characteristics, response to therapy, and prognosis. A leukocyte integrin, CD11b, was the only antigen that showed a significant association with complete remission (CR) duration and survival (P < .025). The mean survival for CD11b+ patients was longer than for CD11b- patients (578 +/- 76 versus 397 +/- 7 days, respectively). CR duration was 897 +/- 84 for CD11b+ patients and 366 +/- 71 for CD11b- patients. Multivariate analysis confirmed the predictive value of CD11b expression for longer survival (relative risk, 3.2; P = .02) and CR duration (relative risk, 3.2; P = .03). CR rate was also significantly higher in CD11b+ patients (77.3%) than in CD11b- patients (46.1%) (P = .01). Survival and remission duration were not influenced by expression of other surface markers including CD13, CD14, CD33, CD34, CD71, CD38, and HLA-DR or by other variables including French-American-British subtype, age, and leukocyte count. Extramedullary disease (EXD) was associated with the presence of both CD13 and CD14 expression (P < .04) but occurred less frequently in CD13+ cases. CD13 expression occurred more frequently in female patients (P = .03). CD38 expression was associated with lower platelet count and an increase in the number of blasts (P < .02).

Glutathione S-transferase polymorphisms and outcome of chemotherapy in childhood acute myeloid leukemia

PURPOSE

Glutathione S-transferase theta (GSTT1) and mu (GSTM1) genes are polymorphic, the genes being absent in approximately 15% and 50% of the population, respectively. Because glutathione S-transferases may be involved in the metabolism of chemotherapy drugs, we hypothesized that presence or absence of the genes may influence the outcome of treatment for childhood acute myeloid leukemia (AML).

PATIENTS AND METHODS

We genotyped GSTT1 and GSTM1 in 306 children with AML receiving chemotherapy on Children's Cancer Group therapeutic studies. Outcomes were compared in those with and without GSTT1 and GSTM1 genes.

RESULTS

Patients with the GSTT1-negative genotype had reduced survival compared with those with at least one GSTT1 allele (GSTT1 positive) (52% v 40% at 5 years; log-rank P =.05). A multivariate model of survival adjusted for age group, sex, WBC count, chloroma, CNS involvement, and French-American-British group confirmed the increased risk of death in the GSTT1-null cases (relative risk, AQ 1.6; P =.02). The frequency of death in remission was increased in GSTT1-negative cases compared with GSTT1-positive cases (24% v 12%, log-rank P =.05). The frequency of relapse from end of induction was similar in GSTT1-negative and GSTT1-positive cases (38% v 35%, log-rank P =.5).

CONCLUSION

Children who lacked GSTT1 had greater toxicity and reduced survival after chemotherapy for AML compared with children with at least one GSTT1 allele. If confirmed in further studies, GSTT1 genotype might be useful in selecting appropriate chemotherapy regimens for children with AML.

Level of minimal residual disease after consolidation therapy predicts outcome in acute myeloid leukemia

We used flow cytometry to quantify minimal residual disease (MRD) in 56 patients with acute myeloid leukemia (AML) expressing a leukemia-associated phenotype. Thirty-four patients aged 18 to 60 years were entered into the AML-10 protocol (induction, consolidation, and autologous stem-cell transplantation [ASCT]), whereas 22 patients older than 60 years received the AML-13 protocol (induction, consolidation, and consolidation II). After induction, the level of MRD that was best associated with treatment outcome was 4.5 × 10−4 residual leukemic cells. However, the outcome in patients with at least 4.5 × 10−4 cells (n = 26) was not significantly different from that in patients with fewer leukemic cells (n = 30); there were 15 (58%) relapses in the first group and 12 (40%) relapses in the second. After consolidation, the most predictive MRD cutoff value was 3.5 × 10−4cells: 22 patients had an MRD level of 3.5 × 10−4 cells or higher and 17 (77%) of these patients had relapse, compared with 5 of 29 patients (17%) with lower MRD levels (P < .001). An MRD level of 3.5 × 10−4 cells or higher after consolidation was significantly correlated with poor or intermediate-risk cytogenetic findings, a multidrug resistance 1 (MDR1) phenotype, short duration of overall survival, and short duration of relapse-free survival (P = .014, .031, .00022, and .00014, respectively). In multivariate analysis, this MRD status was significantly associated with a high frequency of relapse (P < .001) and a short duration of overall (P = .025) and relapse-free survival (P = .007). ASCT did not alter the prognostic effect of high MRD levels after consolidation: the relapse rate after transplantation was 70%. Thus, we found that an MRD level of 3.5 × 10−4 cells or higher at the end of consolidation strongly predicts relapse and is significantly associated with an MDR1 phenotype and intermediate or unfavorable cytogenetic findings.

Level of minimal residual disease after consolidation therapy predicts outcome in acute myeloid leukemia

We used flow cytometry to quantify minimal residual disease (MRD) in 56 patients with acute myeloid leukemia (AML) expressing a leukemia-associated phenotype. Thirty-four patients aged 18 to 60 years were entered into the AML-10 protocol (induction, consolidation, and autologous stem-cell transplantation [ASCT]), whereas 22 patients older than 60 years received the AML-13 protocol (induction, consolidation, and consolidation II). After induction, the level of MRD that was best associated with treatment outcome was 4.5 × 10−4 residual leukemic cells. However, the outcome in patients with at least 4.5 × 10−4 cells (n = 26) was not significantly different from that in patients with fewer leukemic cells (n = 30); there were 15 (58%) relapses in the first group and 12 (40%) relapses in the second. After consolidation, the most predictive MRD cutoff value was 3.5 × 10−4cells: 22 patients had an MRD level of 3.5 × 10−4 cells or higher and 17 (77%) of these patients had relapse, compared with 5 of 29 patients (17%) with lower MRD levels (P &lt; .001). An MRD level of 3.5 × 10−4 cells or higher after consolidation was significantly correlated with poor or intermediate-risk cytogenetic findings, a multidrug resistance 1 (MDR1) phenotype, short duration of overall survival, and short duration of relapse-free survival (P = .014, .031, .00022, and .00014, respectively). In multivariate analysis, this MRD status was significantly associated with a high frequency of relapse (P &lt; .001) and a short duration of overall (P = .025) and relapse-free survival (P = .007). ASCT did not alter the prognostic effect of high MRD levels after consolidation: the relapse rate after transplantation was 70%. Thus, we found that an MRD level of 3.5 × 10−4 cells or higher at the end of consolidation strongly predicts relapse and is significantly associated with an MDR1 phenotype and intermediate or unfavorable cytogenetic findings.