Expression of the polycomb-group gene BMI1 is related to an unfavourable prognosis in primary nodal DLBCL

BACKGROUND

Clinical outcome in patients with diffuse large B cell lymphomas (DLBCL) is highly variable and poorly predictable. Microarray studies showed that patients with DLBCL with a germinal centre B cell-like (GCB) phenotype have a better prognosis than those with an activated B cell-like (ABC) phenotype. The BMI1 proto-oncogene was identified as one of the genes present in the signature of the ABC type of DLBCL, associated with a poor prognosis.

OBJECTIVES

(1) To investigate, in primary nodal DLBCL, the expression of BMI1 and its association with clinical outcome and DLBCL signature; (2) to look for an association between BMI1 expression and the expression of its putative downstream targets p14ARF and p16INK4a.

RESULTS

BMI1 expression was found to be associated with poor clinical outcome, but not clearly with an ABC-like phenotype of DLBCL. Expression of BMI1 was frequently, but not always, related to low levels of expression of p14ARF and p16INK4a.

CONCLUSION

Expression of BMI1 is associated with an unfavourable clinical outcome of primary nodal DLBCL.

MHC class II molecules in tumour immunology: prognostic marker and target for immune modulation

MHC class II molecules presenting MHC class II restricted antigens play an important role in the activation of CD4+ T cells, which are the central orchestrating cells of an immune response. This review focuses on the particular role of MHC class II molecules in tumour immunology. The MHC class II antigen presentation pathway and the expression of MHC class II molecules on tumour cells related to clinical outcome is discussed. Improving the MHC class II tumour antigen presentation pathway, for instance by downregulation of the invariant chain or modulation of HLA-DO expression, offers many opportunities for developing new modalities of immunotherapy.

Leukemia-derived dendritic cells: towards clinical vaccination protocols in acute myeloid leukemia

The ability of acute myeloid leukemic (AML) blasts to differentiate into leukemic dendritic cells (DC) thus acquiring the potential to present known and unknown leukemic antigens efficiently, holds promise as a possible new treatment for AML patients with minimal residual disease. Recent advances in culture methods have made the clinical use of leukemic DC feasible. However, additional measures appear to be essential in order to potentiate vaccines and to overcome the intrinsic tolerant state of the patients immune system. This review describes ways to improve AML-DC vaccines and discusses critical aspects concerning the development of clinical vaccination protocols.

Quantification of T-cell-mediated apoptosis in heterogeneous leukemia populations using four-color multiparameter flow cytometry

BACKGROUND

The unique capacity of dendritic cells to present antigens to naive T cells is being increasingly utilized in cancer therapy. The efficacy of cell-based immunotherapy can be analyzed by determination of cytotoxic activity of T cells toward tumor cells in vitro. This study supplies a flow cytometric method to analyze T-cell-mediated cytotoxic activity toward heterogeneous leukemic cell populations at a single-cell level.

METHODS

The fluorescent probe SYTO16 and the dead-cell dye 7-aminoactinomycine-D (7-AAD) were used to identify early and late stages of apoptosis in combination with leukemia cell-identifying markers. Determination of viable, apoptotic, and necrotic cells was performed by inclusion of fluorescent beads.

RESULTS

In nine acute myeloid leukemia samples and three leukemic cell lines the use of SYTO16 next to the dead-cell marker 7-AAD significantly increased (P = 0.001) the sensitivity of the cytotoxicity assay as compared with single use of 7-AAD. Analysis of several effector-to-target ratios revealed the ability to determine dose-response effects. Enumeration of absolute numbers resulted in coefficients of variation of 4.1% and 8.4% for cell lines and leukemic samples, respectively.

CONCLUSION

The presented flow cytometric cytotoxicity assay enables the study of T-cell-mediated apoptosis in a heterogenous leukemia population.

Immunohistochemical profiling based on Bcl-2, CD10 and MUM1 expression improves risk stratification in patients with primary nodal diffuse large B cell lymphoma

Clinical outcome in patients with diffuse large B cell lymphomas (DLBCL) is poorly predictable. Expression of proteins related to germinal centre B (GCB) cell or activated B cells (ABC) and expression of apoptosis-regulating proteins Bcl-2 and XIAP have been found previously to be strongly associated with clinical outcome. In this study we aimed to develop an algorithm based on expression of GCB/ABC-related proteins CD10, Bcl-6 and MUM1 and apoptosis-inhibiting proteins Bcl-2, XIAP and cFLIP for optimal stratification of DLBCL patients into prognostically favourable and unfavourable groups. Expression of CD10 and cFLIP was associated with better overall survival (both p = 0.03), whereas expression of MUM1, Bcl-2 and XIAP was associated with poor clinical outcome (p = 0.01, p = 0.0007 and p = 0.03, respectively). Multivariate analysis revealed that Bcl-2 was the strongest prognostic marker followed by CD10 and MUM1. Stratification of patients according to a new algorithm based on expression of these three markers improved patient risk stratification into low and particularly high clinical risk groups (p = 0.04 and p < 0.0001, respectively). We conclude that, in our group of primary nodal DLBCLs, a new algorithm, based on expression of the apoptosis-inhibiting protein Bcl-2 and the GCB/ABC-related proteins CD10 and MUM1, strongly predicts outcome in International Prognostic Index (IPI)-low and -high patients. Its predictive power is stronger than previously published algorithms based on only GCB/ABC- or apoptosis-regulating proteins.

Apoptosis resistance and response to chemotherapy in primary nodal diffuse large B-cell lymphoma

Diffuse large B-cell lymphomas (DLBCL) represent the most common type of adult malignant lymphoma in western countries and are treated with high dose combination chemotherapy. Although initially the majority of patients respond to this therapy, many do not achieve complete remission and others experience an early relapse. Several studies have shown that prediction of the clinical response to chemotherapy is possible before the start of chemotherapy treatment. Apparently, DLBCL are intrinsically either resistant or sensitive to chemotherapy-induced cell death. Differences in functional integrity of the apoptosis cascade are an important factor predicting outcome in DLBCL. In this review we discuss the possible mechanisms leading to intrinsic resistance to apoptosis and provide an explanation why strong differences in apoptosis sensitivity between DLBCL are observed. Subsequently we will focus on how differences in this intrinsic apoptosis resistance provide an explanation for the variable response to combination chemotherapy and how this can be used for further therapy tailoring.

Immunologic purging of autologous peripheral blood stem cell products based on CD34 and CD133 expression can be effectively and safely applied in half of the acute myeloid leukemia patients

PURPOSE

Several studies have shown survival benefit by autologous stem cell transplantation in acute myeloid leukemia (AML) after purging of grafts. This has, however, not been confirmed in randomized studies due to high toxicity of purging modalities for normal progenitor/stem cells. In this study, we investigated whether positive selection for CD34+ and/or CD133+ cells, which results in high recovery of normal progenitor/stem cells, is applicable for purging AML grafts.

EXPERIMENTAL DESIGN

Positive selections of normal stem cells using CD34 and/or CD133 can be done if one or both markers are absent or have dim expression and remain so during the course of the disease. Marker expressions in newly diagnosed AML were measured with flow cytometry using a cutoff value for positivity of 1%. Stability of marker expression was studied by pairwise comparison of material at diagnosis and relapse. Leukemia associated phenotype expression was used to measure the efficacy of tumor cell reduction.

RESULTS

In newly diagnosed AML (n = 165), we found no CD34 and/or CD133 expression in 32% of the cases and dim expression in 20% of the cases. No increase in the percentage of CD34+ cells (n = 44) and CD133+ cells (n = 29) was found in corresponding relapses. Positive selection using grafts contaminated with AML blasts, showing either no or dim expression of CD34 or CD133, resulted in a 3 to 4 log tumor cell reduction (n = 11) with median 50% recovery of normal stem cells.

CONCLUSIONS

Purging by positive selection of CD34+ and/or CD133+ cells can safely, effectively, and reproducibly be applied in about 50% of AML cases.

High stem cell frequency in acute myeloid leukemia at diagnosis predicts high minimal residual disease and poor survival

PURPOSE

In CD34-positive acute myeloid leukemia (AML), the leukemia-initiating event originates from the CD34(+)CD38(-) stem cell compartment. Survival of these cells after chemotherapy may lead to minimal residual disease (MRD) and subsequently to relapse. Therefore, the prognostic impact of stem cell frequency in CD34-positive AML was investigated.

EXPERIMENTAL DESIGN

First, the leukemogenic potential of unpurified CD34(+)CD38(-) cells, present among other cells, was investigated in vivo using nonobese diabetic/severe combined immunodeficient mice transplantation experiments. Second, we analyzed whether the CD34(+)CD38(-) compartment at diagnosis correlates with MRD frequency after chemotherapy and clinical outcome in 92 AML patients.

RESULTS

In vivo data showed that engraftment of AML blasts in nonobese diabetic/severe combined immunodeficient mice directly correlated with stem cell frequency of the graft. In patients, a high percentage of CD34(+)CD38(-) stem cells at diagnosis significantly correlated with a high MRD frequency, especially after the third course of chemotherapy. Also, it directly correlated with poor survival. In contrast, total CD34(+) percentage showed no such correlations.

CONCLUSIONS

Both in vivo data, as well as the correlation studies, show that AML stem cell frequency at diagnosis offers a new prognostic factor. From our data, it is tempting to hypothesize that a large CD34(+)CD38(-) population at diagnosis reflects a higher percentage of chemotherapy-resistant cells that will lead to the outgrowth of MRD, thereby affecting clinical outcome. Ultimately, future therapies should be directed toward malignant stem cells.

Allogeneic stem cell transplantation for patients with acute myeloid leukemia or myelodysplastic syndrome who have chromosome 5 and/or 7 abnormalities

BACKGROUND AND OBJECTIVES

Chromosome 5 and/or 7 abnormalities are cytogenetic findings indicative of a poor prognosis in patients with acute myeloid leukemia (AML) or myelodysplastic syndrome (MDS). The only potential cure for such patients is allogeneic stem cell transplantation (SCT). As data on allogeneic SCT in this context are limited we did a retrospective study of allogeneic SCT in patients with AML or MDS who had chromosome 5 and/or 7 abnormalities.

DESIGN AND METHODS

This was a retrospective study of 65 patients (16 children, 49 adults) with AML (n=33) or MDS (n=32) who had chromosome 5 and/or 7 abnormalities and who underwent allogeneic SCT in six Dutch Centers between 1983 and 2001. Data on all these patients are recorded in the Netherlands Stem Cell Transplant Registry (Typhon).

RESULTS

The 3-year overall survival rate among all patients was 25%. Patients below the age of 40 years had significantly fewer relapses (40%) and better survival (38%) than those above the age of 40 (86% and 8%, respectively). Relapses were less frequent in recipients of unrelated grafts than in those whose grafts were from HLA-identical siblings (30% versus 69%). The development of acute graft-versus-host disease (GVHD) grades II-IV was independently associated with significantly higher transplant-related mortality (TRM). Patients with either chromosome 5 or chromosome 7 abnormalities had a significantly better survival than patients with both chromosome 5 and 7 abnormalities. These patients with poor-risk chromosome 5 and/or 7 abnormalities were compared with a group of patients with a secondary AML/MDS and normal cytogenetics and were found to have significantly more relapses and significantly worse survival but a similar TRM.

INTERPRETATION AND CONCLUSIONS

We conclude that patients with AML or MDS with chromosome 5 and/or 7 abnormalities do rather poorly after allogeneic SCT, mainly because of the very high relapse rate. Nevertheless, this is the only approach that can cure some of these patients.

Employing the immunological synapse in AML: Development of leukemic dendritic cells for active specific immunization

Cytotoxic T cells directed against leukemic blasts have been observed in patients with acute myeloid leukemia (AML). However, generation of efficient T-cell responses is hampered due to several factors that enable AML blasts to protect themselves from the patients immune system. Improved immune responses can be established by the differentiation of AML blasts into AML-derived dendritic cells (DC) thereby conserving their intrinsic leukemia specific antigens and obtaining full capacity to present these antigens to naive T cells. This review discusses increased immunogenicity of AML blasts by differentiation into AML-DC and describes ways to augment the AML-DC vaccination approach.

The value of the MDR1 reversal agent PSC-833 in addition to daunorubicin and cytarabine in the treatment of elderly patients with previously untreated acute myeloid leukemia (AML), in relation to MDR1 status at diagnosis

To determine whether MDR1 reversal by the addition of the P-glycoprotein (P-gp) inhibitor PSC-833 to standard induction chemotherapy would improve event-free survival (EFS), 419 untreated patients with acute myeloid leukemia (AML) aged 60 years and older were randomized to receive 2 induction cycles of daunorubicin and cytarabine with or without PSC-833. Patients in complete remission were then given 1 consolidation cycle without PSC-833. Neither complete response (CR) rate (54% versus 48%; P = .22), 5-year EFS (7% versus 8%; P = .53), disease-free survival (DFS; 13% versus 17%; P = .06) nor overall survival (OS; 10% in both arms; P = .52) were significantly improved in the PSC-833 arm. An integrated P-gp score (IPS) was determined based on P-gp function and P-gp expression in AML cells obtained prior to treatment. A higher IPS was associated with a significantly lower CR rate and worse EFS and OS. There was no significant interaction between IPS and treatment arm with respect to CR rate and survival, indicating also a lack of benefit of PSC-833 in P-gp-positive patients. The role of strategies aimed at inhibitory P-gp and other drug-resistance mechanisms continues to be defined in the treatment of patients with AML.

Identification of genes potentially involved in disease transformation of CML

In patients with chronic myeloid leukemia (CML) who do not reach a (near) complete cytogenetic response, the disease progresses over several years from an indolent, chronic phase into a rapidly fatal blast crisis. Events that are responsible for this transformation process are largely unknown. To identify changes in gene expression that occurred during the course of the disease, we performed cDNA subtraction on sequentially stored peripheral blood mononuclear cell pellets, collected throughout the course of disease of a single CML patient. In total, 32 differentially expressed sequences were identified, of which 27 corresponded to known genes. On quantitative PCR, eight of these genes, YWHAZ, GAS2, IL8, IL6, PBEF1, CCL4, SAT and MMRN, showed comparable differential expression in additional CML patient samples. This set of genes can be considered as a starting point for further research on causes of disease transformation in CML and may lead to new targets in the treatment of resistant CML.

Sequential organ failure predicts mortality of patients with a haematological malignancy needing intensive care

OBJECTIVES

Poor survival of patients with a haematological malignancy admitted to the intensive care unit (ICU) prompts for proper admission triage and prediction of ICU treatment failure and long-term mortality. We therefore tried to find predictors of the latter outcomes.

METHODS

A retrospective analysis of charts and a prospective follow-up study were done, of haemato-oncological patients, admitted to our ICU in a 7-year period with a follow-up until 2 yr thereafter. Clinical parameters during the first four consecutive days were taken to calculate the simplified acute physiology (SAPS II) and the sequential organ failure assessment (SOFA) scores, of proven predictive value in general ICU populations.

RESULTS

From a total of 58 patients (n = 47 with acute myelogenous leukaemia or non-Hodgkin lymphoma), admitted into ICU mostly because of respiratory insufficiency, sepsis, shock or combinations, 36 patients had died during their stay in the ICU. Of ICU survivors (n = 22), 20 patients died during follow-up so that the 1-year survival rate was only 12%. The SAPS II and particularly the SOFA scores were of high predictive value for ICU and long-term mortality.

CONCLUSIONS

Patients with life-threatening complications of haematological malignancy admitted to ICU ran a high risk for death in the ICU and on the long-term, and the risk can be well predicted by SOFA. The latter may help us to decide on intensive care in individual cases, in order to avoid potentially futile care for patients with a SOFA score of 15 or higher.

Minimal Residual Disease in Acute Myeloid Leukemia Is Predicted by an Apoptosis-Resistant Protein Profile at Diagnosis

PURPOSE

Apoptosis is an important mechanism regulating survival of acute myeloid leukemia cells. The apoptosis-related protein profile at diagnosis is important for achieving complete remission thereby affecting survival variables such as disease-free survival (DFS) and overall survival (OS).To investigate the role of the apoptosis protein profile in further response to therapy and outgrowth of disease.

EXPERIMENTAL DESIGN

We studied whether Bcl-2, Bcl-xL, Mcl-1, Bax as well as the Bcl-2/Bax ratio and a combination of all (antiapoptosis index, AAI) are related to the frequency of malignant cells surviving the chemotherapy (i.e., minimal residual disease, MRD). MRD cells were identified by leukemia-associated aberrant phenotypes established at diagnosis by flow cytometry.

RESULTS

We found that Bcl-2 (R = 0.55, P = 0.002), Bcl-2/Bax (R = 0.42, P = 0.02), and AAI (R = 0.47, P = 0.01) at diagnosis directly correlated with MRD after the first cycle of chemotherapy. In turn, MRD frequency after first cycle correlated with DFS (P = 0.04). Taken together, these results directly explain why Bcl-2/Bax and especially AAI (P = 0.007) at diagnosis correlate with DFS.

CONCLUSION

Our results show that apoptosis resistance plays an important role in the first stage of the therapy (i.e., to eliminate the bulk of malignant cells), in terms of achievement of complete remission and frequency of MRD after first cycle of therapy.

Immunohistochemical profiling of caspase signaling pathways predicts clinical response to chemotherapy in primary nodal diffuse large B-cell lymphomas

We used biopsy specimens of primary nodal diffuse large B-cell lymphoma (DLBCL) to investigate whether the inhibition of caspase 8 and/or 9 apoptosis signaling pathways predicts clinical outcome. Expression levels of cellular FLICE inhibitory protein (c-Flip) and numbers of active caspase 3-positive lymphoma cells were used to determine the status of the caspase 8-mediated pathway. Expression levels of Bcl-2 and X-linked inhibitor of apoptosis (XIAP) were used to determine the status of the caspase 9-mediated pathway. Expression of c-Flip, XIAP, Bcl-2, and caspase 3 activity all provided prognostic information. According to these immunohistochemical parameters, inhibition of either or both caspase signaling pathways was detected in all patients. Three groups of patients were identified, one with a caspase 8 inhibition profile, one with caspase 8 and 9 inhibition profiles, and one with a caspase 9 inhibition profile. Caspase 9 inhibition was strongly associated with poor response to chemotherapy and usually with fatal outcome, whereas caspase 8 inhibition was associated with excellent clinical outcome. Thus, our data strongly suggest that inhibition of the caspase 9-mediated pathway, but not the caspase 8-mediated pathway, is a major cause for therapy resistance in patients with nodal DLBCL.

Short intensive sequential therapy followed by autologous stem cell transplantation in adult Burkitt, Burkitt-like and lymphoblastic lymphoma

The feasibility and efficacy of up-front high-dose sequential chemotherapy followed by autologous stem cell transplantation (ASCT) in previously untreated adults (median age 33 years; range 15-64) with Burkitt lymphoma (BL), Burkitt-like lymphoma (BLL) or lymphoblastic lymphoma (LyLy), both without central nervous system or extensive bone marrow involvement was investigated in a multicenter phase II study. Treatment consisted of two sequential high-dose chemotherapy induction courses incorporating prednisone, cyclophosphamide, doxorubicin, etoposide and mitoxantrone, without high-dose methotrexate or high-dose cytarabine. Patients with at least PR went on with BEAM and ASCT. Protocol treatment was completed by 23/27 (85%) BL/BLL and 13/15 (87%) LyLy patients. Median treatment duration until BEAM was 70 (range: 50-116) days. No toxic deaths occurred. Response to treatment was complete response (CR) 81% and partial response (PR) 11% for BL/BLL, CR 73% and PR 20% for LyLy. At a median follow-up of 61 months of patients still alive, six BL/BLL and eight LyLy patients have died. The actuarial 5-year overall and event-free survival estimates are 81 and 73% for BL/BLL vs 46 and 40% for LyLy patients. In conclusion, this short up-front high-dose sequential chemotherapy regimen, followed by ASCT is highly effective in adults with BL/BLL with limited bone marrow involvement, but less so in patients with LyLy.

Prognostic Index for Adult Patients With Acute Myeloid Leukemia in First Relapse

Purpose

The treatment of acute myeloid leukemia (AML) in first relapse is associated with unsatisfactory rates of complete responses that usually are short lived. Therefore, a clinically useful prognostic index can facilitate therapeutic decision making and evaluation of investigational treatment strategies at relapse of AML.

Patients and Methods

A prognostic score is presented based on the multivariate analysis of 667 AML patients in first relapse among 1,540 newly diagnosed non-M3 AML patients (age 15 to 60 years) entered onto three successive Dutch-Belgian Hemato-Oncology Cooperative Group and the Swiss Group for Clinical Cancer Research Collaborative Group trials.

Results

Four clinically relevant parameters are included in this index (ie, length of relapse-free interval after first complete remission, cytogenetics at diagnosis, age at relapse, and whether previous stem-cell transplantation was performed). Using this stratification system, three risk groups were defined: a favorable prognostic group A (overall survival [OS] of 70% at 1 year and 46% at 5 years), an intermediate-risk group B (OS of 49% at 1 year and 18% at 5 years), and a poor-risk group C (OS of 16% at 1 year and 4% at 5 years).

Conclusion

The prognostic index estimates the outcome of AML patients in first relapse using four commonly applied clinical parameters and might identify patients who are candidates for salvage and investigational therapy.

C-type lectin-like molecule-1: a novel myeloid cell surface marker associated with acute myeloid leukemia

Acute myeloid leukemia (AML) has a poor prognosis due to treatment-resistant relapses. A humanized anti-CD33 antibody (Mylotarg) showed a limited response rate in relapsed AML. To discover novel AML antibody targets, we selected a panel of single chain Fv fragments using phage display technology combined with flow cytometry on AML tumor samples. One selected single chain Fv fragment broadly reacted with AML samples and with myeloid cell lineages within peripheral blood. Expression cloning identified the antigen recognized as C-type lectin-like molecule-1 (CLL-1), a previously undescribed transmembrane glycoprotein. CLL-1 expression was analyzed with a human anti-CLL-1 antibody that was generated from the single chain Fv fragment. CLL-1 is restricted to the hematopoietic lineage, in particular to myeloid cells present in peripheral blood and bone marrow. CLL-1 is absent on uncommitted CD34(+)/CD38(-) or CD34(+)/CD33(-) stem cells and present on subsets of CD34(+)/CD38(+) or CD34(+)/CD33(+) progenitor cells. CLL-1 is not expressed in any other tissue. In contrast, analysis of primary AMLs demonstrated CLL-1 expression in 92% (68 of 74) of the samples. As an AML marker, CLL-1 was able to complement CD33, because 67% (8 of 12) of the CD33(-) AMLs expressed CLL-1. CLL-1 showed variable expression (10-60%) in CD34(+) cells in chronic myelogenous leukemia and myelodysplastic syndrome but was absent in 12 of 13 cases of acute lymphoblastic leukemia. The AML reactivity combined with the restricted expression on normal cells identifies CLL-1 as a novel potential target for AML treatment.

Health related quality of life in patients with multiple myeloma undergoing a double transplantation

OBJECTIVES

To investigate the subjective well-being of patients with newly diagnosed multiple myeloma who were treated in a tandem transplantation programme.

METHODS

Fifty-one patients participated in the prospective, longitudinal questionnaire study. The EORTC QLQ-C30 and the EuroQol-5D were administered 2 wk after completion of vincristine, adriamycin and dexamethason/vincristine, adriamycin and methyl prednison (VAD/VAMP) chemotherapy, both at hospital discharge after treatment with high-dose melphalan (HDM) and 1 month after this hospital discharge, at hospital admission, at the day of hospital discharge for peripheral stem cell transplantation (PSCT) and at 6 and 12 months following discharge after PSCT.

RESULTS

Overall, patients' functioning improved during treatment and follow-up, with significant decreases shortly following PSCT. Shortly after HDM and PSCT, patients reported a considerable increase in levels of soreness in the mouth (+26/+36 points on a scale ranging form 0 to 100; P < 0.01), change of taste (+23/+21 points; P < 0.05/NS), nausea/vomiting (+26/+27 points; P < 0.01/< 0.05), appetite loss (+40/+43 points; P < 0.001) and diarrhoea (+25/+36 points; P < 0.01). However, none of these symptoms persisted during follow-up.

CONCLUSION

The intensive treatment programme was subjectively being well tolerated by the majority of patients. The duration of declined quality of life after administration of HDM seemed to be short. The duration of subjective recovery after PSCT remained uncertain, but in any case was present at the 6 month follow-up. Together with the rather good results in survival, the evaluation of quality of life invites further exploration of double transplantations in multiple myeloma.

Purging of peripheral blood stem cell transplants in AML: a predictive model based on minimal residual disease burden

OBJECTIVE

Minimal residual disease (MRD) present in peripheral blood stem cell (PBSC) products of AML patients may contribute to relapse. Our goal was to 1) predict leukemia recurrence based on the frequency of MRD present in PBSC products, 2) establish the efficacy of different purging procedures, and 3) integrate this into a model that enables to predict whether or not to purge.

METHODS

Minimal residual disease was measured with flow cytometry using leukemia-associated phenotypes as established at diagnosis. Toxicity of purging procedures was established using clonogenic assays. Purging procedures used were cryopreservation, hyperthermia, ether lipid ET-18-OCH3, and combinations.

RESULTS

Minimal residual disease in PBSC products correlated significantly with relapse-free survival (n=24, p=0.003). At a cut-off value of 0.05% MRD the relative risk of relapse was 4.6 times lower in the group with less than 0.05% MRD. As measured in 54 PBSC products, the MRD level was less than 0.05% in 17 of 54 cases, between 0.05% and 0.5% in 19 of 54 cases, and higher than 0.5% in 18 of 54 cases. Based on the MRD cut-off of 0.05%, the log tumor reduction needed to achieve this threshold is zero for the 17 of 54 cases in which MRD was below 0.05%, less than or equal to 1 log in 19 of 54 cases, and greater than 1-2 log in 18 of 54 cases. When applying purging with 25 mug/mL ET-18-OCH3 combined with cryopreservation at 10% DMSO and hyperthermia at 42 degrees C combined with cryopreservation at 10% or 4% DMSO, there was greater than or equal to 1 log depletion of AML blasts.

CONCLUSION

This study establishes (1) a threshold level for MRD above which prognosis is worse, (2) that stem cell products from 69% of patients have higher than this "safe" MRD level, and (3) that ET-18-OCH3 and hyperthermia may be used to purge products in part of these patients.

Antibody-targeted therapy: a paradigm of innovative treatment strategies in indolent and aggressive B-cell non-Hodgkin lymphoma

PURPOSE OF REVIEW

This review outlines the principles of treatment of indolent and aggressive B-cell lymphoma based on current knowledge on the classification of hematologic malignancies and the rationale to implement new antibody-targeted immunotherapeutic approaches.

RECENT FINDINGS

An update is provided on the use of antibody-targeted therapies in clinical trials, with emphasis on new, emerging strategies of immunotherapy in B-cell non-Hodgkin lymphoma.

SUMMARY

The success of immune-mediated therapies has encouraged studies on antibody-targeted therapy in B-cell non-Hodgkin lymphoma. Promising new approaches combine classical dose-intense chemotherapy with "tumor-specific" antibody targeting during several phases of the disease. The safety and efficacy of anti-CD20 in the treatment of indolent and aggressive B-cell non-Hodgkin lymphoma at any stage of disease, either as a single agent or as part of multimodality regimes, as an unconjugated antibody or as radioimmunoconjugate have changed dramatically our treatment strategies. Increasing insights into basic molecular biology and immunology of B-cell non-Hodgkin lymphoma may identify subgroups of patients categorized in current classification systems who may benefit from tailored approaches with new modality antibody-targeted therapy in near future.

Gene expression profiling of minimal residual disease in acute myeloid leukaemia by novel multiplex-PCR-based method

In acute myeloid leukaemia (AML), alterations in apoptotic pathways are crucial for treatment outcome, resulting either in refractoriness or in minimal residual disease (MRD). The apoptosis characteristics of MRD cells may differ from those at diagnosis and thereby determine the adequacy of further treatment. Such characteristics are largely unknown, since studies hereto are hampered by minimal cell availability. This study explores the applicability of the recently described RT-Multiplex Ligation-dependent Probe Amplification (RT-MLPA) for gene expression analysis of small amounts of RNA obtained from MRD cells. Reproducibility and dilution experiments showed that the relative expression of 37 apoptosis-related genes starting with only 1000 cells could be measured with 12% variation; for 100 cells, 31/37 genes could still be quantified, though expression variation increased. In practice 100-1000 leukemic cells can be obtained from bone marrow samples with clinically relevant MRD percentages of 0.01-0.1. Procedures often necessary to obtain AML blasts, that is, FACS-sorting, freeze-thawing or combinations are possible, provided that selected viable nonapoptotic cells are used. Concluding, RT-MLPA allows accurate gene expression profiling of MRD cells. This method will help to gain insight into the processes of MRD emergence and persistence in AML, which may ultimately guide new therapeutic strategies in AML.

MRD parameters using immunophenotypic detection methods are highly reliable in predicting survival in acute myeloid leukaemia

Outgrowth of minimal residual disease (MRD) in acute myeloid leukaemia (AML) is responsible for the occurrence of relapses. MRD can be quantified by immunophenotyping on a flow cytometer using the expression of leukaemia-associated phenotypes. MRD was monitored in follow-up samples taken from bone marrow (BM) of 72 patients after three different cycles of chemotherapy and from autologous peripheral blood stem cell (PBSC) products. The MRD% in BM after the first cycle (n=51), second cycle (n=52) and third cycle (n=30), as well as in PBSC products (n=39) strongly correlated with relapse-free survival. At a cutoff level of 1% after the first cycle and median cutoff levels of 0.14% after the second, 0.11% after the third cycle and 0.13% for PBSC products, the relative risk of relapse was a factor 6.1, 3.4, 7.2 and 5.7, respectively, higher for patients in the high MRD group. Also, absolute MRD cell number/ml was highly predictive of the clinical outcome. After the treatment has ended, an increase of MRD% predicted forthcoming relapses, with MRD assessment intervals of < or =3 months. In conclusion, MRD parameter assessment at different stages of disease is highly reliable in predicting survival and forthcoming relapses in AML.