Quinine improves the results of intensive chemotherapy in myelodysplastic syndromes expressing P glycoprotein: results of a randomized study

CuAAC-Based Synthesis, Copper-Catalyzed Aldehyde-Forming Hydrolytic Fission and Antiproliferative Evaluation of Novel Ferrocenoylamino-Substituted Triazole-Tethered Quinine-Chalcone Hybrids

A series of novel triazole-tethered ferrocenoylamino-substituted cinchona-chalcone hybrids along with two representative benzoylamino-substituted reference compounds were prepared by three methods of CuAAC chemistry. In line with the limited success or complete failure of attempted conversions with low catalyst loadings, by means of DFT modeling studies, we demonstrated that a substantial part of the Cu(I) ions can be chelated and thus trapped in the aroylamino-substituted cinchona fragment and all of the accessible coordinating sites of the chalcone residues. Accordingly, increased amounts of catalysts were used to achieve acceptable yields; however, the cycloadditions with para-azidochalcones were accompanied by partial or complete aldehyde-forming hydrolytic fission of the enone C=C bond in a substituent-, solvent- and copper load-dependent manner. The experienced hydrolytic stability of the hybrids obtained by cycloadditions with ortho-azidochalcones was interpreted in terms of relative energetics, DFT reactivity indices and MO analysis of simplified models of two isomer copper-enone complexes. The novel hybrids were evaluated on HeLa, MDA-MB-231 and A2780 cell lines and showed substantial activity at low-to-submicromolar concentrations. An organometallic model carrying 3,4,5-trimethoxyphenyl residue in the enone part with a para-disubstituted benzene ring in the central skeletal region was identified as the most potent antiproliferative lead, characterized by submicromolar IC50 values measured on the three investigated cells. The biological assays also disclosed that this ferrocenoylamino-containing lead compound displays a ca. two- to five-fold more substantial antiproliferative effect than its benzoylamino-substituted counterpart.

A clinical trial of zosuquidar plus gemtuzumab ozogamicin (GO) in relapsed or refractory acute myeloid leukemia (RR AML): evidence of efficacy based on leukemic blast P-glycoprotein functional phenotype

PURPOSE

To evaluate safety, tolerability, potential efficacy, and pharmacodynamics (PD) of zosuquidar (Zos) in combination with gemtuzumab ozogamicin (GO) in elderly patients with relapsed or refractory (RR) acute myeloid leukemia (AML).

METHODS

Patients with RR AML (N = 41) were treated with Zos as a 48-h continuous intravenous infusion initiated 4 h prior to a 2-h infusion of GO on days 1 and 15. P-glycoprotein (P-gp) status of the patients' leukemic blasts and PD determinations were assessed with ex vivo bioassays. Patient outcomes were analyzed for the total cohort and as stratified into P-gp-positive (P-gp +) and P-gp-negative (P-gp‒) subgroups.

RESULTS

The eligible cohort exhibited a 34% overall remission rate (ORR), a composite of patients that exhibited complete remission (CR), CR with incomplete platelet recovery, or morphologic remission. Patients with 1st relapsed disease exhibited 40% ORR. P-gp phenotype did not significantly predict ORR. However, the P-gp + subgroup exhibited a greater median overall survival (OS) of 6.0 months vs. 1.8 months for patients in the P-gp‒ subgroup (p = 0.01). PD analyses revealed 90-95% inhibition of blast P-gp function during Zos infusion. Treatment related toxicities were observed and resolved with decrease or discontinued Zos or GO dosages.

CONCLUSIONS

Zos plus GO elicited appreciable ORR for an elderly patient population with RR AML. The greater OS of the P-gp + subgroup vs. the P-gp‒ subgroup suggests that patients with P-gp + leukemic blasts were being more effectively targeted by GO with Zos co-therapy. The poorer OS of the P-gp‒ subgroup suggests activity of Zos-insensitive multidrug resistant mechanisms.

CLINICAL TRIALS

GOV IDENTIFIER

NCT00233909; First posted October 06, 2005.

Clinical Significance of ABCB1 in Acute Myeloid Leukemia: A Comprehensive Study

ABCB1 is a member of the ATP binding cassette transporter family and high ABCB1 activity is considered as a poor prognostic factor in acute myeloid leukemia (AML) treated with intensive chemotherapy, its direct relation with drug resistance remains unclear. We evaluated ABCB1 activity in relation with clinical parameters and treatment response to standard chemotherapy in 321 patients with de novo AML. We assessed multiple clinical relationships of ABCB1 activity—ex vivo drug resistance, gene expression, and the ABCB1 inhibitor quinine were evaluated. ABCB1 activity was observed in 58% of AML and was linked to low white blood cell count, high expression of CD34, absence of FLT3-ITD, and absence of mutant NPM1. Moreover, ABCB1 activity was associated with worse overall- and event-free survival. However, ABCB1 activity did not directly lead to ex vivo drug resistance to anthracyclines. We found that ABCB1 was highly correlated with gene expressions of BAALC, CD34, CD200, and CD7, indicating that ABCB1 expression maybe a passenger characteristic of high-risk AML. Furthermore, ABCB1 was inversely correlated to HOX cluster genes and CD33. Thus, low ABCB1 AML patients benefited specifically from anti-CD33 treatment by gemtuzumab ozogamicin in addition to standard chemotherapy. We showed prognostic importance of ABCB1 gene expression, protein expression, and activity. Furthermore, ABCB1 was not directly linked to drug resistance, ABCB1 inhibition did not improve outcome of high ABCB1 AML patients and thus high ABCB1 may represent a passenger characteristic of high-risk AML.

Evidence of a role for functional heterogeneity in multidrug resistance transporters in clinical trials of P-glycoprotein modulation in acute myeloid leukemia

BACKGROUND

Multidrug resistance (MDR) transporter proteins such as P-glycoprotein (P-gp) efflux a variety of chemotherapeutic drugs from acute myeloid leukemia (AML) blasts leading to clinical drug resistance.

METHODS

This study examined heterogeneity of MDR functional efflux by AML blasts using two flow cytometry bioassays. Bone marrow specimens (N = 50) from elderly patients with newly diagnosed AML were analyzed for CD34+ blasts with MDR efflux function. Efflux was measured with a fluorescent dye (DiOC₂ ) as a surrogate for oncology drugs that are substrates for MDR efflux. P-gp-mediated efflux was differentiated from non-P-gp MDR activities using zosuquidar, a highly selective P-gp modulator. The bioassays included a zosuquidar-dependent DiOC₂ accumulation bioassay that measured only P-gp. The second method, termed the efflux bioassay, could detect P-gp and other non-P-gp efflux depending on bioassay culture conditions.

RESULTS

Sixty-two percent of the specimens were considered positive for blasts with P-gp function, and 26% of such P-gp-positive specimens also exhibited zosuquidar-resistant (i.e., non-P-gp) MDR efflux activity; 37% of P-gp-negative AML blast specimens displayed zosuquidar-resistant MDR function in the efflux bioassay.

CONCLUSIONS

These results confirm the heterogeneous nature of MDR efflux pumps in AML blasts, and provide support for the hypothesis that non-P-gp MDR contributed to negative results with zosuquidar in AML trials like ECOG-ACRIN E3999. © 2018 International Clinical Cytometry Society.

Knockdown of the Wnt receptor Frizzled-1 (FZD1) reduces MDR1/P-glycoprotein expression in multidrug resistant leukemic cells and inhibits leukemic cell proliferation

Multidrug resistance (MDR) is a major obstacle to leukemia treatment. The Frizzled-1 (FZD1) Wnt receptor is involved in MDR in some solid cancers, but has rarely been reported to act in acute myeloid leukemia (AML). We investigated whether the knockdown of FZD1 affects MDR1 expression and P-glycoprotein (P-gp) function in multidrug resistant leukemic cell lines, as well as FZD1 and MDR1/P-gp expression in leukemic cells taken from patients with AML (n = 112). FZD1 knockdown significantly reduced MDR1 expression through the Wnt/β-catenin pathway, disrupted the P-gp efflux function, induced the recovery of sensitivity to chemotherapeutic agents, and hindered cell proliferation in cell lines. FZD1 expression in leukemic cells was significantly higher in patients experiencing relapse (n = 34) than in those with no relapse (n = 44, P = .003). Leukemic cells unable to achieve complete response (CR) showed an increased expression of MDR1 and P-gp, compared to patients who achieved CR. Obtaining CR in patients with higher FZD1 expression at diagnosis is difficult. Moreover, they tend to present instances of relapse, suggesting that AML cells with increased FZD1 expression are resistant to chemotherapy. We conclude that the activated FZD1 observed in leukemic cells likely confers acquired drug resistance, whereas FZD1 silencing may be more effective in reversing MDR.

Idarubicin and cytarabine in combination with gemtuzumab ozogamicin (IAGO) for untreated patients with high-risk MDS or AML evolved from MDS: a phase II study from the EORTC and GIMEMA Leukemia Groups (protocol 06013)

The primary objective of this trial was to assess the feasibility, toxicity profile, and antitumor activity of gemtuzumab ozogamicin (GO) combined with a chemotherapy remission-induction regimen in adults with untreated high-risk myelodysplastic syndrome (HR-MDS) or secondary acute myeloid leukemia (sAML). In this phase II trial, 30 patients with median age of 58 years received 1 day of GO as a 1-h infusion at the dose level of 5 mg/m² on day 7 of the remission-induction course further consisting of a continuous infusion of cytarabine 100 mg/m²/day for 10 days and idarubicin 12 mg/m²/day on days 1, 3, and 5. A consolidation course, consisting of intermediate-dose cytarabine (A) and idarubicin (I) followed by hematopoietic stem cell transplantation (HSCT) was planned for patients in complete remission (CR). The primary endpoints were response rate (CR/CRi) and severe toxicity rate. The secondary endpoint(s) were survival and progression-free survival (PFS) from start of treatment. Thirteen patients (43 %) achieved CR (eight patients) or CR with incomplete hematopoietic recovery (CRi) (five patients). In patients who achieved CR or CRi, the median time to recovery of neutrophils to 0.5 × 10⁹/l and of platelets to >50 × 10⁹/l was 29 and 30 days, respectively. Grade 3 to 4 severe toxicities occurred in nine patients. The most prominent was liver toxicity, as shown by elevated bilirubin levels in 16 patients and one case of nonfatal veno-occlusive disease (VOD). All 13 patients with CR/CRi received consolidation therapy, which was followed by allogeneic HSCT in five patients and autologous HSCT in three patients. According to the statistical design of the study, the idarubicin and cytarabine in combination with gemtuzumab ozogamicin (IAGO) regimen did not show sufficient activity to warrant further exploration of this regimen in adult patients with HR-MDS or sAML.

Diagnosis and treatment of primary myelodysplastic syndromes in adults: recommendations from the European LeukemiaNet

Within the myelodysplastic syndrome (MDS) work package of the European LeukemiaNet, an Expert Panel was selected according to the framework elements of the National Institutes of Health Consensus Development Program. A systematic review of the literature was performed that included indexed original papers, indexed reviews and educational papers, and abstracts of conference proceedings. Guidelines were developed on the basis of a list of patient- and therapy-oriented questions, and recommendations were formulated and ranked according to the supporting level of evidence. MDSs should be classified according to the 2008 World Health Organization criteria. An accurate risk assessment requires the evaluation of not only disease-related factors but also of those related to extrahematologic comorbidity. The assessment of individual risk enables the identification of fit patients with a poor prognosis who are candidates for up-front intensive treatments, primarily allogeneic stem cell transplantation. A high proportion of MDS patients are not eligible for potentially curative treatment because of advanced age and/or clinically relevant comorbidities and poor performance status. In these patients, the therapeutic intervention is aimed at preventing cytopenia-related morbidity and preserving quality of life. A number of new agents are being developed for which the available evidence is not sufficient to recommend routine use. The inclusion of patients into prospective clinical trials is strongly recommended.

Drug resistance: still a daunting challenge to the successful treatment of AML

Resistance to chemotherapy remains a challenging issue for patients and their physicians. P-glycoprotein (Pgp, MDR1, ABCB1), as well as a family of structurally and functionally related proteins, are plasma membrane transporters able to efflux a variety of substrates from the cell cytoplasm, including chemotherapeutic agents. The discovery of ABCB1 made available a potential target for pharmacologic down-regulation of efflux-mediated chemotherapy resistance. In patients with acute myeloid leukemia (AML), a neoplasm characterized by proliferation of poorly differentiated myeloid progenitor cells, leukemic cells often express ABCB1 at high levels, which may lead to the development of resistance to chemotherapy. Thus, AML seemed to be a likely cancer for which the addition of drug efflux inhibitors to the chemotherapeutic regimen would improve outcomes in patients. Despite this rational hypothesis, the majority of clinical trials evaluating this strategy have failed to reach a positive endpoint, most recently the Eastern Cooperative Oncology Group E3999 trial. Here we review data suggesting the importance of ABCB1 in AML, address the failure of clinical trials to support a therapeutic strategy aimed at modulating ABCB1-mediated resistance, and consider the type of research that should be conducted in this field going forward.

ATP Binding Cassette transporters associated with chemoresistance: transcriptional profiling in extreme cohorts and their prognostic impact in a cohort of 281 acute myeloid leukemia patients

BACKGROUND

A major issue in the treatment of acute myeloid leukemia is resistance to chemotherapeutic drugs. An increasing number of ATP-Binding-Cassette transporters have been demonstrated to cause resistance to cancer drugs. The aim of this study was to highlight the putative role of other ATP-Binding-Cassette transporters in primary chemoresistant acute myeloid leukemia.

DESIGN AND METHODS

In the first part of this study, using taqman custom arrays, we analyzed the relative expression levels of 49 ATP-Binding-Cassette genes in 51 patients divided into two extreme cohorts, one very sensitive and one very resistant to chemotherapy. In the second part of this study, we evaluated the prognostic impact, in a cohort of 281 patients, of ATP-Binding-Cassette genes selected in the first part of the study.

RESULTS

In the first part of the study, six genes (ATP-Binding-CassetteA2, ATP-Binding-CassetteB1, ATP-Binding-CassetteB6, ATP-Binding-CassettC13, ATP-Binding-CassetteG1, and ATP-Binding-CassetteG2) were significantly over-expressed in the resistant group compared with the sensitive group. In the second cohort, overexpression of 5 of these 6 ATP-Binding-Cassette genes was correlated with outcome in univariate analysis, and only the well-known ATP-Binding-CassetteB1 and G2, and the new ATP-Binding-CassetteG1 in multivariate analysis. Prognosis decreased remarkably with the number of these over-expressed ABC genes. Complete remission was achieved in 71%, 59%, 54%, and 0%, (P=0.0011) and resistance disease in 21%, 37%, 43%, and 100% (P<0.0001) of patients over-expressing 0, 1, 2, or 3, ABC genes, respectively. The number of ATP-Binding-Cassette genes expressed, among ATP-Binding-CassetteB1, G1, and G2, was the strongest prognostic factor correlated, in multivariate analysis, with achievement of complete remission (P=0.01), resistant disease (P=0.01), and overall survival (P=0.02).

CONCLUSIONS

Using expression profiling, we have emphasized the diversity of ATP-Binding-Cassette transporters that cooperate to promote chemoresistance rather than overexpression of single transporters and the putative role of new ATP-Binding-Cassette tranporters, such as ATP-Binding-CassetteG1. Modulation of these multiple transporters might be required to eradicate leukemic cells.

Value of allogeneic versus autologous stem cell transplantation and chemotherapy in patients with myelodysplastic syndromes and secondary acute myeloid leukemia. Final results of a prospective randomized European Intergroup Trial

BACKGROUND

Allogeneic stem cell transplantation is usually considered the only curative treatment option for patients with advanced or transformed myelodysplastic syndromes in complete remission, but post-remission chemotherapy and autologous stem cell transplantation are potential alternatives, especially in patients over 45 years old.

DESIGN AND METHODS

We evaluated, after intensive anti-leukemic remission-induction chemotherapy, the impact of the availability of an HLA-identical sibling donor on an intention-to treat basis. Additionally, all patients without a sibling donor in complete remission after the first consolidation course were randomized to either autologous peripheral blood stem cell transplantation or a second consolidation course consisting of high-dose cytarabine.

RESULTS

The 4-year survival of the 341 evaluable patients was 28%. After achieving complete remission, the 4-year survival rates of patients under 55 years old with or without a donor were 54% and 41%, respectively, with an adjusted hazard ratio of 0.81 (95% confidence interval [95% CI], 0.49-1.35) for survival and of 0.67 (95% CI, 0.42-1.06) for disease-free survival. In patients with intermediate/high risk cytogenetic abnormalities the hazard ratio in multivariate analysis was 0.58 (99% CI, 0.22-1.50) (P=0.14) for survival and 0.46 (99% CI, 0.22-1.50) for disease-free survival (P=0.03). In contrast, in patients with low risk cytogenetic characteristics the hazard ratio for survival was 1.17 (99% CI, 0.40-3.42) and that for disease-free survival was 1.02 (99% CI, 0.40-2.56). The 4-year survival of the 65 patients randomized to autologous peripheral blood stem cell transplantation or a second consolidation course of high-dose cytarabine was 37% and 27%, respectively. The hazard ratio in multivariate analysis was 1.22 (95% CI, 0.65-2.27) for survival and 1.02 (95% CI, 0.56-1.85) for disease-free survival.

CONCLUSIONS

Patients with a donor and candidates for allogeneic stem cell transplantation in first complete remission may have a better disease-free survival than those without a donor in case of myelodysplastic syndromes with intermediate/high-risk cytogenetics. Autologous peripheral blood stem cell transplantation does not provide longer survival than intensive chemotherapy.

Immunosuppressors as multidrug resistance reversal agents

Multidrug-resistance (MDR) is the major reason for failure of cancer therapy. ATP-binding cassette (ABC) transporters contribute to drug resistance via ATP-dependent drug efflux. P-glycoprotein (Pgp), which is encoded by MDR1 gene, confers resistance to certain anticancer agents. The development of agents able to modulate MDR mediated by Pgp and other ABC transporters remained a major goal for the past 20 years. The calcium blocker verapamil was the first drug shown to be a modulator of Pgp, and since many different chemical compounds have been shown to exert the same effect in vitro by blocking Pgp activity. These included particularly immunosuppressors. Cyclosporin A (CSA) was the first immunosuppressor that have been shown to modulate Pgp activity in laboratory models and entered very early into clinical trials for reversal of MDR. The proof of reversing activity of CSA was found in phase II studies with myeloma and acute leukemia. In phase III studies, the results were less convincing regarding the response rate, progression-free survival, and overall survival, which were detected in advanced refractory myeloma. The non-immunosuppressive derivative PSC833 (valspodar) was subsequently developed. This compound showed tenfold higher potency in reversal of MDR mediated by Pgp. However, pharmacokinetic interactions required reductions in the dose of the concurrently administered anticancer agents. The pharmacokinetic interactions were likely because of decreased clearance of the anticancer agents, possibly as a result of Pgp inhibition in organs such as the gastrointestinal tract and kidney, as well as inhibition of cytochrome P450. Finally, CSA and PSC833 have been shown also to modulate the ceramide metabolism which stands as second messenger of anticancer agent-induced apoptosis. In fact, CSA and PSC833 are also able to respectively inhibit ceramide glycosylation and stimulate de novo ceramide synthesis. This could enhance the cellular level of ceramide and potentiate apoptosis induced by some anticancer agents.

A phase I trial of continuous infusion of the multidrug resistance inhibitor zosuquidar with daunorubicin and cytarabine in acute myeloid leukemia

Zosuquidar is a potent and specific inhibitor of P-glycoprotein (P-gp). In preliminary experiments, blockade of P-gp for at least 12 h was required to reverse daunorubicin resistance. Because of the short half-life of zosuquidar, we performed a phase I trial of this drug as a 72-h infusion (CIV) in 16 patients during leukemic induction with daunorubicin and cytarabine. Study goals were to establish safety and determine the dose required for P-gp inhibition in NK cells and AML blasts. > 90% P-gp inhibition was achieved within 2h at a plasma threshold of 132 ng/ml zosuquidar. The recommended phase II dose of zosuquidar is 700 mg/day.

Leukemic blast and natural killer cell P-glycoprotein function and inhibition in a clinical trial of zosuquidar infusion in acute myeloid leukemia

A bioassay was developed to assess P-glycoprotein (P-gp) function of peripheral blood natural killer (NK) cells and AML blasts during zosuquidar infusion. Cells were incubated with the fluorescent dye DiOC(2)(3) in the presence and absence of zosuquidar, and dye accumulation measured by flow cytometry. The assay performance was assessed using NK cells and the P-gp-positive K562/R7 cell line, and then utilized to determine the function of P-gp and its inhibition by zosuquidar in AML blasts and NK cells from patients enrolled in a Phase I trial. The assay of zosuquidar-inhibitable accumulation of DiOC(2) is robust and reproducible.

The interaction between HMGB1 and TLR4 dictates the outcome of anticancer chemotherapy and radiotherapy

For the last four decades, the treatment of cancer has relied on four treatment modalities, namely surgery, radiotherapy, cytotoxic chemotherapy, and hormonotherapy. Most of these therapies are believed to directly attack and eradicate tumor cells. The emerging concept that cancer is not just a disease of a tissue or an organ but also a host disease relies on evidence of tumor-induced immunosuppression and polymorphisms in genes involved in host protection against tumors. This theory is now gaining new impetus, based on our recent data showing that optimal therapeutic effects require the immunoadjuvant effect of tumor cell death induced by cytotoxic anticancer agents. Here, we show that the release of the high mobility group box 1 protein (HMGB1) by dying tumor cells is mandatory to license host dendritic cells (DCs) to process and present tumor antigens. HMGB1 interacts with Toll-like receptor 4 (TLR4) on DCs, which are selectively involved in the cross-priming of anti-tumor T lymphocytes in vivo. A TLR4 polymorphism that affects the binding of HMGB1 to TLR4 predicts early relapse after anthracycline-based chemotherapy in breast cancer patients. This knowledge may be clinically exploited to predict the immunogenicity and hence the efficacy of chemotherapeutic regimens.

Tariquidar (XR9576): a P-glycoprotein drug efflux pump inhibitor

P-glycoprotein actively transports structurally unrelated compounds out of cells, conferring the multidrug resistance phenotype in cancer. Tariquidar is a potent, specific, noncompetitive inhibitor of P-glycoprotein. Tariquidar inhibits the ATPase activity of P-glycoprotein, suggesting that the modulating effect is derived from the inhibition of substrate binding, inhibition of ATP hydrolysis or both. In clinical trials, tariquidar is tolerable and does not have significant pharmacokinetic interaction with chemotherapy. In patients, inhibition of P-glycoprotein has been demonstrated for 48 h after a single dose of tariquidar. Studies to assess a possible increase in toxicity of chemotherapy and the impact of P-glycoprotein inhibition on tumor response and patient outcome are ongoing. Tariquidar can be considered an ideal agent for testing the role of P-glycoprotein inhibition in cancer.

ABC transporters and drug resistance in leukemia: was P-gp nothing but the first head of the Hydra?

More than 30 years ago it was discovered that permeability glycoprotein (P-gp) can cause drug resistance. Over the following decades numerous studies showed that high expression of P-gp is associated with poor prognosis in acute myeloid leukemia in adults and that it causes multidrug resistance via ATP-dependent drug efflux. It was hoped that an inhibition of P-gp could sensitize resistant leukemic cells to chemotherapy and thus improve treatment results. Today we know that the family of ATP-binding cassette transporters (ABC transporters) comprises 48 different proteins. Some of them seem to be able to cause drug resistance as well as P-gp. This review focuses on emerging data on the clinical relevance of other ABC transporters, such as BCRP, MRP3, and ABCA3. When Heracles fought the ancient Hydra, he had to fight all the heads at ones but only one head was vital for the beast. Can we block all the relevant ABC transporters at once? Is there one transporter that is more important than the others?

[Expression of multidrug resistance (MDR)-associated proteins in solid tumors]

The causes of drug resistance in tumor cells vary widely. The present study aims to provide an update of multidrug resistance in tumor cells and, in particular, of multidrug resistance-associated proteins.

Targeting multidrug resistance in cancer

Effective treatment of metastatic cancers usually requires the use of toxic chemotherapy. In most cases, multiple drugs are used, as resistance to single agents occurs almost universally. For this reason, elucidation of mechanisms that confer simultaneous resistance to different drugs with different targets and chemical structures - multidrug resistance - has been a major goal of cancer biologists during the past 35 years. Here, we review the most common of these mechanisms, one that relies on drug efflux from cancer cells mediated by ATP-binding cassette (ABC) transporters. We describe various approaches to combating multidrug-resistant cancer, including the development of drugs that engage, evade or exploit efflux by ABC transporters.

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.

Management of patients with higher risk myelodysplastic syndromes

Higher risk myelodysplastic syndromes (MDS) include patients in the Intermediate-2 and high-risk categories of the International Prognostic Scoring System, as well as patients with MDS secondary to radiation or chemical exposure. Ideally, the goal of therapy is to alter the natural history of disease in these patients to achieve cure or durable remission. High-intensity chemotherapy can achieve moderate rates of complete remission, however, durability of remission and overall survival tend to be short. Hematopoietic stem cell transplantation (HSCT) offers the possibility of cure, with long-term disease-free survival inversely related to age. Patients who are elderly or have poor functional status are candidates for reduced intensity HSCT, although this is still an experimental modality. Azacitidine is a hypomethylating agent that is a reasonable option for many patients ineligible for high-intensity therapies. Other therapies, such as immunomodulatory agents, arsenic trioxide, and farnesyl transferase inhibitors have thus far shown limited usefulness in higher risk MDS. This paper reviews the various therapeutic options for higher risk MDS, providing rationale for specific management approaches for these patients.

Treatment-related myelodysplastic syndrome/acute myeloid leukemia in survivors of childhood cancer--an update

Treatment-related myelodysplastic syndrome/acute myeloid leukemia (t-MDS/t-AML) is a devastating complication of treatment for childhood cancer. However, the major cause of premature death of children treated for cancer remains their primary cancer. The understanding of the presentation, incidence, predisposing risk factors and pathobiology of t-MDS/t-AML is increasing. This increased understanding has not yet been translated into improved outcomes of therapy for t-MDS/t-AML. However, newer approaches are under study.

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.

Immunophenotyping as a guide for targeted therapy

Immunophenotyping of acute and chronic leukaemias has revealed many lineage- and differentiation-specific antigens. It has now become possible to classify leukaemias according to their unique antigenic expression pattern. Among many lineage- and differentiation-specific antigens, disease-specific antigens are increasingly recognized because of their specific prognostic or therapeutic relevance. Expression of the multidrug resistance proteins of the ABC transporter family is associated with a poor response to treatment and a grave clinical prognosis. Recently, attempts to reverse refractory disease by using P-glycoprotein inhibitors have been performed in acute myeloid leukaemia, so far without evidence of clinical benefit. Other new leads to use antigen expression as a way of designing tumour-specific therapy have resulted in imatinib and Flt3 inhibitors which target tyrosine kinases in the leukaemic cell. Clinical trials are underway to investigate the effect of these new agents. The development of an antibody-calicheamycin complex directed against the myeloid-specific antigen CD33 has shown clinical activity in patients with relapsed acute myeloid leukaemia. The further development of these approaches is discussed.

Mitoxantrone, etoposide, and cytarabine with or without valspodar in patients with relapsed or refractory acute myeloid leukemia and high-risk myelodysplastic syndrome: a phase III trial (E2995)

PURPOSE

To determine whether adding the multidrug resistance gene-1 (MDR-1) modulator valspodar (PSC 833; Novartis Pharmaceuticals, Hanover, NJ) to chemotherapy provided clinical benefit to patients with poor-risk acute myeloid leukemia (AML) and high-risk myelodysplastic syndrome (MDS).

PATIENTS AND METHODS

A phase III randomized study was performed using valspodar plus mitoxantrone, etoposide, and cytarabine (PSC-MEC; n=66) versus MEC (n=63) to treat patients with relapsed or refractory AML and high-risk MDS.

RESULTS

For the PSC-MEC versus MEC arms, complete response (CR) was achieved in 17% versus 25% of patients, respectively (P=not significant). For patients who had not received prior intensive chemotherapy (ie, with secondary AML or high-risk MDS), the CR rate was increased--35% versus 15% for the remaining patients (P=.018); CR rates did not differ between treatment arms. The median disease-free survival in those achieving CR was similar in the two arms (10 versus 9.3 months) as was the patients' overall survival (4.6 versus 5.4 months). The CR rates in MDR+ (69% of patients) versus MDR- patients were similar for those receiving either chemotherapy regimen (16% versus 24%). The CR rate for unfavorable cytogenetic patients (45% of patients) was 13% compared to the remainder, 28% (P=.09). Population pharmacokinetic analysis demonstrated that the clearances of mitoxantrone and etoposide were decreased by 59% and 50%, respectively, supporting the empiric dose reductions in the PSC-MEC arm designed in anticipation of drug interactions between valspodar and the chemotherapeutic agents.

CONCLUSION

CR rates and overall survival were not improved by using PSC-MEC compared to MEC chemotherapy alone in patients with poor-risk AML or high-risk MDS.

Myelodysplastic syndromes

The myelodysplastic syndromes (MDS) are characterized by hemopoietic insufficiency associated with cytopenias leading to serious morbidity plus the additional risk of leukemic transformation. Therapeutic dilemmas exist in MDS because of the disease's multifactorial pathogenetic features, heterogeneous stages, and the patients' generally elderly ages. Underlying the cytopenias and evolutionary potential in MDS are innate stem cell lesions, cellular/cytokine-mediated stromal defects, and immunologic derangements. This article reviews the developing understanding of biologic and molecular lesions in MDS and recently available biospecific drugs that are potentially capable of abrogating these abnormalities. Dr. Peter Greenberg's discussion centers on decision-making approaches for these therapeutic options, considering the patient's clinical factors and risk-based prognostic category. One mechanism underlying the marrow failure present in a portion of MDS patients is immunologic attack on the hemopoietic stem cells. Considerable overlap exists between aplastic anemia, paroxysmal nocturnal hemoglobinuria, and subsets of MDS. Common or intersecting pathophysiologic mechanisms appear to underlie hemopoietic cell destruction and genetic instability, which are characteristic of these diseases. Treatment results and new therapeutic strategies using immune modulation, as well as the role of the immune system in possible mechanisms responsible for genetic instability in MDS, will be the subject of discussion by Dr. Neal Young. A common morphological change found within MDS marrow cells, most sensitively demonstrated by electron microscopy, is the presence of ringed sideroblasts. Such assessment shows that this abnormal mitochondrial iron accumulation is not confined to the refractory anemia with ring sideroblast (RARS) subtype of MDS and may also contribute to numerous underlying MDS pathophysiological processes. Generation of abnormal sideroblast formation appears to be due to malfunction of the mitochondrial respiratory chain, attributable to mutations of mitochondrial DNA, to which aged individuals are most vulnerable. Such dysfunction leads to accumulation of toxic ferric iron in the mitochondrial matrix. Understanding the broad biologic consequences of these derangements is the focus of the discussion by Dr. Norbert Gattermann.

Quinine as a multidrug resistance inhibitor: a phase 3 multicentric randomized study in adult de novo acute myelogenous leukemia

Based on our previous demonstration that quinine could be used clinically to reverse P-glycoprotein-mediated resistance, we designed a multicenter, randomized trial aiming to determine whether quinine would improve the survival of adult patients (15-60 years old) with de novo acute myelogenous leukemia (AML). These patients randomly received (n = 213) or did not receive (n = 212) a 30 mg/kg/day continuous intravenous infusion of quinine in combination with induction chemotherapy combining idarubicine and cytarabine and, depending on bone marrow examination at day 20, an additional course of cytarabine and mitoxantrone. The mean steady-state quinine concentration was 7.8 mg/L and the mean multidrug resistance reversing activity of serum was 1.96. Complete remission (CR) was obtained in 344 patients (80.9%) without significant influence of quinine. Of the patients in complete remission, 82 were assigned to receive HLA-matched bone marrow transplants, whereas 262 were assigned to 2 courses of intensive consolidation chemotherapy, with or without quinine, depending on initial randomization. The 4-year actuarial overall survival (OS) of the 425 eligible patients was 42.0% +/- 2.5%, without significant influence of quinine. Of 160 patients who could be studied, 54 demonstrated rhodamine 123 efflux. In these patients, quinine significantly improved the CR rate from 12 of 25 (48.0%) to 24 of 29 (82.8%) (P =.01). However, there was no significant difference in OS. Neither mdr1 gene nor P-glycoprotein expression influenced the outcome. We conclude that quinine does not improve the survival of adult patients with de novo AML, even though it improves CR rate in a small subgroup of patients defined by rhodamine 123 efflux.

Quinine 3-hydroxylation as a biomarker reaction for the activity of CYP3A4 in man

OBJECTIVE

To investigate the usefulness of the 3-hydroxylation of quinine as a biomarker reaction for the activity of CYP3A4 in man and to study the interindividual variation in the metabolic ratio (MR), i.e. quinine/3-hydroxyquinine.

METHODS

Data from a previous study (A) was used for determination of the MR of quinine in plasma and urine at different time points. In study B, 24 healthy Swedish subjects received 250 mg quinine hydrochloride first alone and later together with four other CYP probe drugs [losartan (CYP2C9), omeprazole (CYP2C19), debrisoquine (CYP2D6) and caffeine (CYP1A2)] administered on the same day. Plasma and urine samples were collected before quinine intake and 16 h thereafter and analysed for quinine and 3-hydroxyquinine using high-performance liquid chromatography. Plasma and/or urine were collected for the other probes at different time points. MRs of all the probes were determined and correlations to quinine MR were studied.

RESULTS

In study A, the MR in plasma was stable over 96 h. The ratio increased from 5.8 to 12.2 (P=0.006) during co-administration with ketoconazole, whereas no significant difference (P=0.76) was observed during co-administration with fluvoxamine (from 5.8 to 6.0). In study B, there was no significant difference (P=0.36) between the mean MRs when quinine was given alone (4.7) or together with the four other drugs (4.5). There was a significant correlation between the MR of quinine and omeprazole sulphone formation (r=0.52, P<0.01), but not to the MRs of the other probes. There was a fivefold interindividual variability in the MR.

CONCLUSIONS

The MR of quinine in plasma or urine may serve as a stable measure of the activity of CYP3A4 in man. These results together with in vitro data show that quinine is also a specific CYP3A4 probe.

Myelodysplastic syndrome

The last decade has witnessed a multistep evolution in the understanding of the natural history, clinical manifestations, and some of the molecular mechanisms that underlie the ineffective hematopoiesis and leukemic transformation in the myelodysplastic syndrome (MDS). The international prognostic scoring system, FAB, and WHO classifications have helped define specific subgroups with their characteristic cytogenetic, molecular and immunological abnormalities. Until recently the mainstay of the treatment has been entirely supportive with blood and platelet transfusions. What is increasingly manifest now is the considerable excitement generated by the emergence of novel therapeutic strategies based on painstaking research findings from the laboratories. In Section I, Dr. Alan List reviews the therapeutic strategies with the specific emphasis on the relevance of molecular mechanism of apoptosis and targeted therapies using small molecules. Of particular interest is the excitement surrounding the clinical benefit obtained from potent immunomodulatory derivative (IMiD) of thalidomide CC5013. The review provides an update of the role of small molecule inhibitors of VEGF receptor tyrosine kinase, arsenic trioxide, oral matrix metalloprotease inhibitors, farnesyl transferase inhibitors, and imatinib mesylate in the treatment of MDS subgroups. In Section II, Dr. Steven Gore describes the results of clinical trials of inhibitors of DNA methylation such as 5 azacytidine (5 AC) and 5-aza 2-deoxycytidine (Decitabine). The review also provides an update on the rationale and results obtained from the combination therapy using histone deacetylases (HDAC) and DNA methyltransferase inhibitors in the treatment of MDS. In Section III, Professor Ghulam Mufti and Dr. Aloysius Ho describe the role of bone marrow transplantation with particular emphasis on recent results from reduced-intensity conditioned transplants, exploiting the graft versus leukemia effect without significant early treatment-related mortality. The section provides an update on the results obtained from the manipulation of the host's immune system with immunosuppressive agents such as ALG and/or cyclosporine A.

Acute myeloid leukaemia: optimising treatment in elderly patients

Acute myeloid leukaemia (AML) is a disease of the elderly (median age at presentation 64 years). The outcome in older patients with AML is much worse than that for similarly treated younger patients. Older patients have a high incidence of recognised poor prognostic features (poor performance status, unfavourable cytogenetics, CD34 positive phenotype, raised serum lactate dehydrogenase levels and increased incidence of multidrug resistance protein expression). In addition, treatment is less well tolerated as there is an increased incidence of comorbidity in the elderly. The outlook for most patients is poor (4% survival at 5 years). However, it is possible to select a group of patients who are fit, with no pre-existing problems and good performance status who will respond well to intensive chemotherapy, and these patients should be treated aggressively. Less intensive treatment is probably more suitable for patients not fitting these criteria. Patients and their relatives should be counselled appropriately as to the prognosis of AML, the choices of treatment available and that intensive regimens are not an appropriate choice for many patients.

[Prognostic factors in myelodysplasia syndromes]

Large studies have shown that, in MDS, main prognostic factors for survival and progression to AML were the percentage of bone marrow blasts, the number and importance of cytopenias, and the presence of cytogenetic abnormalities. The combination of those 3 factors has yielded an International Prognostic Scoring System (IPSS), with very strong prognostic value for survival and progression to AML, which can therefore be used as a guideline for therapeutic choices. Other important prognostic factors can be derived from molecular studies. They include ras genes mutations, p53 mutations and p15 hypermethylation, but their independent prognostic value remains uncertain.

Drug resistance in hematologic malignancies

Drug resistance eventually occurs in most hematologic malignancies treated with chemotherapy. The mechanisms responsible for drug resistance include expression of transporters of xenobiotics of the adenosine triphosphate-binding cassette protein superfamily (P-glycoprotein, multidrug resistance associated proteins, breast cancer resistance protein), modifications of enzymes like deoxycytidine kinase, and defects in chemotherapy-induced apoptosis. The efforts to overcome this drug resistance have been focused, thus far, on modulation of P-glycoprotein. Several compounds were manufactured for this purpose, and phase III trials of PSC833, one of the most potent P-glycoprotein inhibitors, are completed. The emergence of modulators with several adenosine triphosphate-binding cassette protein targets, like GG120918 (inhibiting P-glycoprotein and breast cancer resistance protein) and VX710 (inhibiting P-glycoprotein and multidrug resistance associated protein 1), are of clinical interest in malignancies often expressing several efflux pumps simultaneously. Another approach is the use of "furtive" drugs like liposomal or nanoparticular anthracyclines.

High-dose chemotherapy in high-risk myelodysplastic syndrome: covariate-adjusted comparison of five regimens

BACKGROUND

Antileukemic chemotherapy has been used for two decades to treat high-risk myelodysplastic syndrome (refractory anemia with excess of blasts [RAEB] and RAEB in transformation into acute leukemia [RAEB-t]) patients. Because the results of standard regimens have been disappointing, high-dose chemotherapeutic regimens were investigated recently. In the absence of randomized trials, the relative merits of various treatment regimens are unknown.

METHODS

The authors analyzed the outcome for 394 newly diagnosed patients treated between 1991 and 1999 with five regimens consisting of intermediate- or high-dose cytosine arabinoside (A) in combination with idarubicin (I), and introduced cyclophosphamide (C) and the new agents fludarabine (F) and topotecan (T) into new combinations with A. In addition to defining the role of high-intensity chemotherapy in the overall outcome for patients with RAEB-t and RAEB, the authors determined the relative merits of the five regimens (IA, FA, FAI, TA, and CAT), accounting for the nonrandom distribution of the prognostic covariates.

RESULTS

The overall complete response (CR) rate of 58% was significantly associated with karyotype, performance status (PS), treatment in the laminar air flow room, duration of antecedent hematologic disorder and age, but not French-American-British or International Prognostic Scoring System risk categories. Multivariate analysis did not identify statistically significant differences in CR rates obtained with each regimen. Induction death rates increased with age with all but the TA regimen; they were lowest with TA (5.4%) and highest with FAI (20.7%), and these differences were significant in patients older than 65 years. The trend for time to death was the same as for time to recurrence in all groups. Multivariate analysis of time to death identified treatment regimen (FA, FAI, and CAT), cytogenetic status (-5/-7), increasing age, and PS greater than 2 as significant independent unfavorable prognostic factors. After prognostic variables were accounted for, survival with IA treatment remained superior to that of FA and FAI but comparable to TA, and CR duration was only marginally shorter with FA. Landmark analysis showed the overall survival of responders to be superior to that of nonresponders, the difference remaining significant after adjustment for prognostic covariates.

CONCLUSIONS

Although the newer regimens did not improve outcome, TA and CAT produced results comparable to those of IA and may be considered treatment alternatives. The TA regimen was particularly effective in RAEB patients and could be delivered safely, with low induction mortality. Our results indicated that although CR seemed associated with survival advantage, innovative post-remission managements represent a challenge because improvement in outcome is not likely to come from intensified therapy.

Combined action of PSC 833 (Valspodar), a novel MDR reversing agent, with mitoxantrone, etoposide and cytarabine in poor-prognosis acute myeloid leukemia

PSC 833 (Valspodar) can reverse multidrug resistance (MDR) in patients with hematologic malignancies, but alters the pharmacokinetics of concomitant anticancer agents. A phase I, dose-finding study was initiated to define a safe and effective regimen of mitoxantrone, etoposide, and cytarabine (MEC) when administered with PSC 833 to patients with early relapsed or refractory acute myeloid leukemia (AML). Poor-prognosis AML patients refractory to first-line induction therapy or relapsing within 9 months of attaining complete remission (CR) were treated with cytarabine (1.0 g/m2/day), etoposide (30 mg/m2/day), and mitoxantrone at a dose of either 3.0 mg/m2/day (cohort 1) or 4.5 mg/m2/day (cohorts 2 and 3) for 6 days plus continuous-infusion PSC 833 (10 mg/kg/24 h with a 2.0 mg/kg loading dose) for 6 or 7 days each 21-day cycle. Patients achieving CR were given a 4-day MEC plus PSC 833 consolidation cycle. Twenty-three patients were enrolled (eight with primary refractory AML and 15 in relapse). Dose-limiting toxicity occurred in one of six patients in cohort 2 (grade 4 mucositis) and one of seven patients in cohort 3 (grade 4 hyperbilirubinemia). The maximum tolerated dose of mitoxantrone was defined as 4.5 mg/m2/day. Clinically significant grade 4 hyperbilirubinemia, possibly related to PSC 833, occurred in four patients. Hematologic toxicities were as expected in this patient population, but were not dose limiting. Mild to moderate cerebellar ataxia and paresthesia occurred in six (26%) and five (22%) patients, respectively, but were not dose limiting. Overall, six of 23 (26%) patients achieved CR, including five patients with demonstrated P-glycoprotein expression and/or function. The median overall survival was 4 months. All six patients with a CR were alive and four (17%) patients were disease free at 12 months. Blood levels of PSC 833 were well above the target level of 1000 ng/ml, a concentration that is known to reverse MDR in vitro. PSC 833 reduced the clearance of etoposide by approximately two-fold. No correlation was observed between the mitoxantrone or etoposide area under the curve and response. In conclusion, the MEC plus PSC 833 tested regimen was well tolerated and the 26% CR rate warrants further testing of this regimen in a randomized, phase III trial.

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.

Cyclosporin increases cellular idarubicin and idarubicinol concentrations in relapsed or refractory AML mainly due to reduced systemic clearance

The feasibility of adding both the multidrug resistance modulator cyclosporin (CsA) and granulocyte colony-stimulating factor (G-CSF) to a standard salvage regimen of idarubicin (IDA) and cytarabine was evaluated in patients with resistant or relapsed acute myeloid leukemia and myelodysplastic syndrome. Three patients received IDA 12 mg/m2/day, the next four patients 9 mg/m2/day. The dose of CsA was 16 mg/kg/day. Six patients showed Pgp expression and none MRP1 expression. Grade III or IV toxicity (CTC-NCIC criteria) was registered in six patients for gastrointestinal, two patients for cardiovascular and one patient for neurological complications. Three patients died in hypoplasia and three patients showed leukemic regrowth. Three control patients were treated with IDA 12 mg/m2/day and cytarabine, but no CsA and G-CSF. The plasma IDA and idarubicinol (ida-ol) area under the curve's of patients treated with IDA 12 mg/m2 plus CsA were higher (P< 0.05) than in controls. Cellular IDA concentrations were almost similar, but cellular ida-ol concentrations were significantly higher (P < 0.05) in the presence of CsA than in controls. We conclude that the toxicity either with IDA 12 or 9 mg/m2/day was too high. The modulating effect of CsA was mainly based on changes in plasma kinetics of IDA and ida-ol, although ida-ol cellular clearance was delayed in the presence of CsA.

Phase I study of cinchonine, a multidrug resistance reversing agent, combined with the CHVP regimen in relapsed and refractory lymphoproliferative syndromes

Overexpression of P-glycoprotein (P-gp) in cancer cells reduces intracellular accumulation of various anticancer drugs including anthracyclines and vinca alkaloids. This multidrug resistance (MDR) phenotype can be reversed in vitro by a number of non-cytotoxic drugs. We have identified the quinine's isomer cinchonine as a potent MDR reversing agent, both in vitro and in animal models. Here, we report an open phase I dose escalation trial in patients with refractory or relapsed malignant lymphoid diseases. Cinchonine dihydrochloride was administered by continuous i.v. infusion for 48 h and escalated over five dose levels ranging from 15 to 35 mg/kg/d. Cinchonine infusion started 24 h before i.v. doxorubicin (25 mg/m2), vinblastine (6 mg/m2), cyclophosphamide (600 mg/m2) and methylprednisolone (1 mg/kg/d) (CHVP regimen) and lasted for 24 h after chemotherapy infusion. Thirty-four patients received 87 cycles of CHVP/cinchonine. The MTD of cinchonine administered by continuous i.v. infusion was 30 mg/kg/d. Prolonged cardiac repolarization was the main dose-limiting toxicity. No ventricular arrhythmia including 'torsade de pointes' was observed. An MDR reversing activity was identified in the serum from every patient and correlated with cinchonine serum level. When infused at 30 mg/kg/d, cinchonine demonstrated a limited influence on doxorubicin pharmacokinetic. We conclude that i.v. infusion of cinchonine might be started 12 h before MDR-related chemotherapy infusion and requires continuous cardiac monitoring but no reduction of cytotoxic drug doses.

Positive and negative regulation of apoptotic pathways by cytotoxic agents in hematological malignancies

Most chemotherapeutic drugs can induce tumor cell death by apoptosis. Analysis of the molecular mechanisms that regulate apoptosis has indicated that anticancer agents simultaneously activate several pathways that either positively or negatively regulate the death process. The main pathway from specific damage induced by the drug to apoptosis involves activation of caspases in the cytosol by pro-apoptotic molecules such as cytochrome c released from the mitochondrial intermembrane space. At least in some cell types, anticancer drugs also upregulate the expression of death receptors and sensitize tumor cells to their cognate ligands. The Fas-mediated pathway could contribute to the early steps of drug-induced apoptosis while sensitization to the cytokine TRAIL could be used to amplify the response to cytotoxic drugs. The Bcl-2 family of proteins, that includes anti- and pro-apoptotic molecules, regulates cell sensitivity mainly at the mitochondrial level. Anticancer drugs modulate their expression (eg through p53-dependent gene transcription), their activity (eg by phosphorylating Bcl-2) and their subcellular localization (eg by inducing the translocation of specific BH3-only pro-apoptotic proteins). Very early after interacting with tumor cells, anticancer drugs also activate lipid-dependent signaling pathways that either increase or decrease cell ability to die by apoptosis. In addition, cytotoxic agents can activate protective pathways that involve activation of NFkappaB transcription factor, accumulation of heat shock proteins such as Hsp27 and activation of proteins involved in cell cycle regulation. This review discusses how modulation of the balance between noxious and protective signals that regulate drug-induced apoptosis could be used to improve the efficacy of current therapeutic regimens in hematological malignancies.

Expression of the multidrug resistance-associated protein in myelodysplastic syndromes

In the myelodysplastic syndromes (MDS), P-glycoprotein (P-gp) expression is clinically associated with drug resistance, whereas the clinical significance of multidrug resistance-associated protein (MRP1) is uncertain. Bone marrow from 56 patients with MDS, including six with refractory anaemia (RA)/RA with ringed sideroblasts (RARS), 23 cases of RA with excess blasts/in transformation (RAEB/T), four patients with chronic myelomonocytic leukaemia (CMML) and 23 cases of MDS having progressed to acute myeloid leukaemia (MDS-AML), were studied. MRP1 expression was investigated by immunocytochemistry (ICC) and by flow cytometry using MRPm6 monoclonal antibody. The efflux test using calcein-AM (CAM) +/- probenecid to evaluate MRP1 activity was performed in ten of the 56 patients. Twenty-eight of the 56 cases (50%) expressed MRP1. MRP1 expression was more frequent in MDS-AML than in MDS (70% vs. 36%). The efflux test using CAM was positive in three out of the ten patients tested. The results were in agreement with expression of MRP1 in six cases, and were discordant in four cases (1 MRP-/CAM+, 3 MRP+/CAM-). No correlation was observed between MRP1 expression and P-gp, lung resistance-associated protein (LRP) or CD34 expression, although there was a trend for more frequent MRP1 expression in P-gp-positive cases in MDS-AML (P = 0.08). Ten of the 26 patients treated with intensive chemotherapy achieved complete remission including six out of 16 MRP1+ and four out of ten MRP1- cases (P = NS). In conclusion, MRP1 expression was correlated with disease stage in MDS in our study. As for P-gp, discordant expression/function of MRP1 could be found in some cases, suggesting the existence of non-functional transport proteins in MDS. MRP1 expression did not seem to be a prognostic factor in MDS in our experience.

Chemotherapy of secondary leukemias

Chemotherapy of secondary leukemias is currently still considered to be associated with poor results. However, recent data suggest that the response to remission induction may substantially differ according to the previous medical history of the patients. Therapy related leukemia, arising following exposure to previous alkylating agents or radiotherapy, is often associated with chromosomal abnormalities involving chromosomes 5 and 7 and has a particularly bad response, whereas AML after exposure to epipodophyllotoxins or topoisomerase-II active agents could have a somewhat better response. Acute promyelocytic leukemia secondary to treatment of a primary malignant neoplasm seems to be associated with a better response if compared to other cytotypes of AML or to AML arising after transformation of myelodysplasia. However, here the literature data are not in full agreement, as different kinds of approaches have been applied. In fact, even if the problems encountered in treating patients with secondary leukemia are similar to those seen in patients with AML arising in a background of myelodysplasia (resistant disease and prolonged cytopenia after treatment), there are data suggesting that the use of high dose ara-C, with or without fludarabine, can circumvent resistance in a small but significant number of cases. One of the unsolved problems which still remains is how to consolidate the CR induced with high dose ara-C or with cycles based on anthracycline derivatives. In addition, another question relates to the categories of patients in whom chemotherapy may change the expected survival. Intensive post-remission chemotherapy, with or without autologous HSCT, may constitute an appropriate alternative for patients lacking a suitable sibling donor or for older patients who are in remission after chemotherapy and also able to tolerate other cycles of intensive chemotherapy. In this respect, the specific cytogenetic abnormality involved should be considered the most important prognostic factor for response and disease free survival; patients with abnormalities of chromosome 5 and 7 have a particularly low possibility of response and duration of CR. Furthermore, it is still debatable whether patients, especially the elderly, with these characteristics should go through a series of conventional treatments or just receive supportive treatment. On the other hand, patients with better prognostic factors should be entitled to further intensive treatments, taking into account possible delayed recovery and/or possible less successful collection of peripheral or marrow stem cells.

Acute myeloblastic leukemia secondary to myelodysplasia (MDS-AML): a comparison of remission induction with three drugs versus standard two-drugs induction

To evaluate the addition of a third drug to standard induction chemotherapy in patients with MDS-AML, 23 patients (males/females 13/10, median age 54.3 years, range 24-74 years, median MDS duration 9.8 months, range 2-39 months) who received a standard 2-drugs induction were compared with 23 patients (males/females 11/12, median age 45.6 months, range 21-60 years, median MDS duration 8.3 months, range 2-29 months) who received an intensified 3-drugs induction with etoposide. CR rate, median CR duration and median OS were similar in both groups (48% vs 56%, 4.8 vs 5.9 months, 6.5 vs 7.0 months respectively). Among responding patients, all but one, who underwent allogeneic bone marrow transplantation, relapsed. In conclusion, addition of a third drug (etoposide) does not seem to significantly improve the poor prognosis of MDS-AML patients.

Achievements in Understanding and Treatment of Myelodysplastic Syndromes

The myelodysplastic syndromes (MDS) constitute a challenge for the biologist as well as for the treating physician. In Section I, Dr. Willman reviews the current classifications and disease mechanisms involved in this heterogeneous clonal hematopoietic stem cell disorder. A stepwise genetic progression model is proposed in which inherited or acquired genetic lesions promote the acquisition of “secondary” genetic events mainly characterized by gains and losses of specific chromosome regions. The genetic risk to develop MDS is likely multifactorial and dependent on various constellations of risk-producing and -protecting alleles. In Section II Dr. Barrett with Dr. Saunthararajah addresses the immunologic factors that may act as important secondary events in the development of severe pancytopenia. T cells from patients with MDS may suppress autologous erythroid and granulocytic growth in vitro, and T cell suppression by antithymocyte globulin or cyclosporine may significantly improve cytopenia, especially in refractory anemia. Recent studies have also demonstrated an increased vessel density in MDS bone marrow, and a phase II trial of thalidomide showed responses in a subgroup of MDS patients especially in those with low blast counts. In Section III Dr. Hellström-Lindberg presents results of allogeneic and autologous stem cell transplantation (SCT), intensive and low-dose chemotherapy. The results of allogeneic SCT in MDS are slowly improving but are still poor for patients with unfavorable cytogenetics and/or a high score according to the International Prognostic Scoring System. A recently published study of patients between 55-65 years old showed a disease-free survival (DFS) at 3 years of 39%. Consolidation treatment with autologous SCT after intensive chemotherapy may result in long-term DFS in a proportion of patients with high-risk MDS. Low-dose treatment with 5-azacytidine has been shown to significantly prolong the time to leukemic transformation or death in patients with high-risk MSA. Erythropoietin and granulocyte colony-stimulating factor may synergistically improve hemoglobin levels, particularly in sideroblastic anemia. Recent therapeutic advances have made it clear that new biological information may lead to new treatment modalities and, in combination with statistically developed predictive models, help select patients for different therapeutic options.

Achievements in Understanding and Treatment of Myelodysplastic Syndromes

The myelodysplastic syndromes (MDS) constitute a challenge for the biologist as well as for the treating physician. In Section I, Dr. Willman reviews the current classifications and disease mechanisms involved in this heterogeneous clonal hematopoietic stem cell disorder. A stepwise genetic progression model is proposed in which inherited or acquired genetic lesions promote the acquisition of “secondary” genetic events mainly characterized by gains and losses of specific chromosome regions. The genetic risk to develop MDS is likely multifactorial and dependent on various constellations of risk-producing and -protecting alleles. In Section II Dr. Barrett with Dr. Saunthararajah addresses the immunologic factors that may act as important secondary events in the development of severe pancytopenia. T cells from patients with MDS may suppress autologous erythroid and granulocytic growth in vitro, and T cell suppression by antithymocyte globulin or cyclosporine may significantly improve cytopenia, especially in refractory anemia. Recent studies have also demonstrated an increased vessel density in MDS bone marrow, and a phase II trial of thalidomide showed responses in a subgroup of MDS patients especially in those with low blast counts. In Section III Dr. Hellström-Lindberg presents results of allogeneic and autologous stem cell transplantation (SCT), intensive and low-dose chemotherapy. The results of allogeneic SCT in MDS are slowly improving but are still poor for patients with unfavorable cytogenetics and/or a high score according to the International Prognostic Scoring System. A recently published study of patients between 55-65 years old showed a disease-free survival (DFS) at 3 years of 39%. Consolidation treatment with autologous SCT after intensive chemotherapy may result in long-term DFS in a proportion of patients with high-risk MDS. Low-dose treatment with 5-azacytidine has been shown to significantly prolong the time to leukemic transformation or death in patients with high-risk MSA. Erythropoietin and granulocyte colony-stimulating factor may synergistically improve hemoglobin levels, particularly in sideroblastic anemia. Recent therapeutic advances have made it clear that new biological information may lead to new treatment modalities and, in combination with statistically developed predictive models, help select patients for different therapeutic options.

Current Clinical Practice: Application of Resistance Reversal Agents in Hematologic Malignancies

The clinical application of resistance reversal drugs for patients with hematologic malignancies is reviewed. The phenomenon of multidrug resistance versus other mechanisms are discussed. The pump-like mechanisms of P-glycoprotein, multidrug resistance associated protein, lung resistance protein and of other ATP binding cassette transporter proteins are reviewed briefly, as well as the important substrate drugs and pump-blocking compounds. The problems associated with resistance protein assays in clinical samples and the concept of prognostic versus therapeutic clinical relevance are described, within the context of selected hematologic malignancies. Toxicities and treatment outcomes of phase II and III trials of reversal agents in lymphoma, multiple myeloma, myelodysplastic syndromes, acute myeloid leukemia and blast phase of chronic myeloid leukemia are reviewed. Finally, current options for on-study management of relapsed or refractory hematologic malignancy patients are discussed.

Diagnostics of multidrug resistance in cancer

Multidrug resistance (MDR), caused by the overexpression of two membrane proteins, MDR1-Pgp and/or MRP, is a major obstacle in the chemotherapy of cancer. The proper laboratory diagnosis of clinical multidrug resistance is still an unresolved question, and this uncertainty, in a vicious cycle, does not allow the correct evaluation of the clinical relevance of the MDR phenomenon. More-over, inefficient MDR diagnostics hinders the development of effective resistance-modulation strategies. In this review, after describing the basic features of the MDR drug pump proteins, the currently employed diagnostic methods are discussed. We suggest that a quantitative, functional method developed in our laboratory may provide a major help in the laboratory assessment of cancer MDR.