Using multiple anchor- and distribution-based estimates to evaluate clinically meaningful change on the Functional Assessment of Cancer Therapy-Biologic Response Modifiers (FACT-BRM) instrument

OBJECTIVE

The interpretation of health-related quality of life (HRQL) data from clinical trials can be enhanced by understanding the degree of change in HRQL scores that is considered meaningful. Our objectives were to combine distribution-based and two anchor-based approaches to identify minimally important differences (MIDs) for the 27-item Trial Outcome Index (TOI), the seven-item Social Well-Being (SWB) subscale, and the six-item Emotional Well-being (EWB) subscale from the Functional Assessment of Cancer Therapy-Biological Response Modifiers (FACT-BRM) instrument.

METHODS

Distribution-based MIDs were based on the standard error of measurement. Anchor-based approaches utilized patient-reported global rating of change (GRC) and change in physician-reported performance status rating (PSR). Correlations and weighted kappa statistics were used to assess association and agreement between the two anchors. FACT-BRM changes were evaluated for three time periods: baseline to month 1, month 2 to month 3, and month 5 to month 6.

RESULTS

Association between GRC and change in PSR was poor. Correlation between the anchors and HRQL change scores was largest at month 1 and decreased through month 6. Combining results from all approaches, the MIDs identified were 5-8 points for the TOI, 2 points for the SWB subscale, and 2-3 points for the EWB subscale.

CONCLUSIONS

We combined patient-reported estimates, physician-reported estimates, and distribution-based estimates to derive MIDs for HRQL outcomes from the FACT-BRM. These results will enable interpretation of treatment group effects in a clinical trial setting, and they can be used to estimate sample size or power when designing future studies.

Spontaneous regression of aleukemia congenital leukemia cutis

A full-term 2-week-old boy was referred to the pediatric dermatology clinic with numerous blue to violaceous nodules present since birth. TORCH titers (against toxoplasmosis, cytomegalovirus, herpes simplex virus, rubella, and syphilis) were negative. Complete blood count and peripheral smear were normal. A skin biopsy specimen showed an atypical cellular infiltrate suspicious for leukemia or lymphoma. A bone marrow biopsy specimen demonstrated acute myelogenous leukemia (M4 subtype). Following consultation with pediatric oncology and the recognition of the potential for spontaneous regression, chemotherapy for the infant's condition was not recommended. He remained otherwise healthy and was followed-up with biweekly to monthly complete blood counts and physical examinations, which were repeatedly normal. By 3 months of age, the nodules had completely resolved and there was no evidence of recurrence at 8 months of follow-up. We report this instance of aleukemic congenital leukemia with spontaneous regression of leukemia cutis without therapeutic intervention.

Properties of Mg2+-dependent cation channels in human leukemia K562 cells

The endogenous Mg(2+)-inhibited cation (MIC) current was recently described in different cells of hematopoietic lineage and was implicated in the regulation of Mg2+ homeostasis. Here we present a single channel study of endogenously expressed Mg(2+)-dependent cation channels in the human myeloid leukemia K562 cells. Inwardly directed unitary currents were activated in cell-attached experiments in the absence of Ca2+ and Mg2+ in the pipette solution. The current-voltage (I-V) relationships displayed strong inward rectification and yielded a single channel slope conductance of approximately 30 pS at negative potentials. The I-V relationships were not altered by patch excision into divalent-free solution. Channel open probability (P(o)) and mean closed time constant (tau(C)) were strongly voltage-dependent, indicating that gating mechanisms may underlie current inward rectification. Millimolar concentrations of Ca2+ or Mg2+ applied to the cytoplasmic side of the membrane produced slow irreversible inhibition of channel activity. The Mg(2+)-dependent cation channels described in this study differ from the MIC channels described in human T-cells, Jurkat, and rat basophilic leukemia (RBL) cells in their I-V relationships, kinetic parameters and dependence on intracellular divalent cations. Our results suggested that endogenously expressed Mg(2+)-dependent cation channels in K562 cells and the MIC channels in other hematopoietic cells might be formed by different channel proteins.

Leukemia-Associated Fusion Proteins: Multiple Mechanisms of Action to Drive Cell Transformation

Leukemic cells are defined by two main biological features: arrest of differentiation at a specific stage compatible with continued proliferation, and enhanced resistance to stress. Recent work shows that the leukemia-associated fusion protein PML-RAR can mediate both biological effects targeting independent pathways, through a unifying mechanism. Differentiation block is achieved through transcriptional silencing of genes physiologically regulated by RAR, which are involved in hematopoietic differentiation. In contrast, enhanced resistance to stress is due to the capacity of the fusion protein to cause degradation of the tumor suppressor p53, thus explaining the puzzling observation that mutations of p53 are remarkably rare in acute myeloid leukemias (AMLs). Interestingly, this latter phenomenon depends on expression of wild-type PML, acting as a molecular bridge between p53 and the fusion protein. Strikingly, both effects require a unifying molecular mechanism: aberrant recruitment of histone deacetylases (HDACs). Therefore, the study of this form of leukemia appears also of interest for a better understanding of the action of HDAC inhibitors, potential antitumor drugs that are at the early stages of clinical studies.

Identification of cooperative genes for NUP98-HOXA9 in myeloid leukemogenesis using a mouse model

The chromosomal translocation t(7; 11)(p15;p15), observed in human myeloid leukemia, results in a NUP98 and HOXA9 gene fusion. We generated a transgenic mouse line that specifically expressed the chimeric NUP98-HOXA9 gene in the myeloid lineage. While only 20% of the transgenic mice progressed to leukemia after a latency period, myeloid progenitor cells from nonleukemic transgenic mice still exhibited increased proliferative potential. This suggested that the NUP98-HOXA9 fusion induced a preleukemic phase, and other factors were required for complete leukemogenesis. NUP98-HOXA9 expression promoted the onset of retrovirus-induced BXH2 myeloid leukemia. This phenomenon was used to identify cooperative disease genes as common integration sites (CISs). Meis1, a known HOX cofactor, was identified as a CIS with a higher integration frequency in transgenic than in wild-type BXH2 mice. By the same means we identified further 4 candidate cooperative genes, Dnalc4, Fcgr2b, Fcrl, and Con1. These genes cooperated with NUP98-HOXA9 in transforming NIH 3T3 cells. The system described here is a powerful tool to identify cooperative oncogenes and will assist in the clarification of the multistep process of carcinogenesis.

Unanswered questions in acute myeloid leukaemia

Acute myeloid leukaemia (AML) is a heterogeneous disease that presents with a range of morphological, cytogenetic, immunophenotypic, and biomolecular features. Over the past 20 years, application of new cytogenetic and molecular techniques has greatly improved knowledge of the pathophysiology of AML, resulting in new potential therapeutic applications. However, the results of current therapy are still unsatisfactory, especially in patients who have adverse prognostic factors at the time of diagnosis. Furthermore, some pivotal questions about the procedures of induction and postinduction therapy of AML remain unanswered, and substantial controversy exists on the optimum therapeutic approach for the disorder.

Domains involved in ETO and human N-CoR interaction and ETO transcription repression

The (8;21) translocation between the AML1 and ETO genes is seen in approximately 12-15% of all acute myeloid leukemia (AML) and is a frequently observed nonrandom genetic alteration associated with AML. The ETO moiety was shown to interact with the nuclear receptor co-repressor (N-CoR) complex, which includes mSin3A and the histone deacetylase, HDAC1. Repression of AML1-responsive hematopoietic genes by AML1-ETO and the N-CoR complex may play a mechanistic role in t(8;21) leukemogenesis. In order to characterize the interaction between ETO and N-CoR, mutants of either protein were constructed and tested for binding in both yeast two-hybrid and immunoprecipitation assays. We found that two domains of human N-CoR, amino acid residues 988-1126 and 1551-1803, were necessary for interaction with ETO. Previously, we and other investigators had reported that two unusual zinc finger motifs at the C-terminus of ETO mediated binding to N-CoR. Here, using mammalian two-hybrid assays, we found that transcription repression by ETO was substantially decreased when either zinc finger motif of ETO is deleted or mutated. In addition, we identified a second transcription repression domain located between residues 275 and 487. Characterization of the ETO interaction domains within human N-CoR and of the transcription domains of ETO is a first step in designing targeted molecular therapy for t(8;21) AML.

Relation between CXCR-4 expression, Flt3 mutations, and unfavorable prognosis of adult acute myeloid leukemia

Recently it was shown that, analogous to normal hematopoietic cells, the level of CXC chemokine receptor 4 (CXCR-4) expression on acute myeloid leukemia (AML) cells correlates with stromal cell derived factor-1 alpha (SDF-1)-induced chemotaxis. As we speculated that an anomalous organ distribution of AML cells could affect cell survival and thus result in an altered fraction surviving chemotherapy, we examined a possible correlation between patient prognosis and CXCR-4 expression in AML patients. We found that patients with a high CXCR-4 expression in the CD34(+) subset had a significantly reduced survival and a higher probability of relapse, resulting in a median relapse-free survival (RFS) of only 8.3 months. CXCR-4 expression was significantly higher in fetal liver tyrosine kinase-3 (Flt3)/internal tandem duplication (ITD) AML than in Flt3/wild-type (wt) AML. Covariate analysis indicated that the prognostic significance of Flt3/ITDs with respect to RFS was no more apparent when analyzed in conjunction with the expression of CXCR-4 in the CD34(+) subset, suggesting that the poor prognosis of Flt3/ITD AML might be subordinate to the increased CXCR-4 expression. Using a granulocyte colony-stimulating factor receptor (G-CSF-R)-expressing 32D cell line, we observed that SDF-1/CXCR-4 interaction is required for the survival of myeloid differentiating cells, and it also induces a block in G-CSF-induced myeloid differentiation. These data suggest that the SDF-1/CXCR-4 axis may influence therapy responsiveness and defines unfavorable prognosis in AML.

The peripheral cannabinoid receptor Cb2, frequently expressed on AML blasts, either induces a neutrophilic differentiation block or confers abnormal migration properties in a ligand-dependent manner

Cb2, the gene encoding the peripheral cannabinoid receptor, is located in a common virus integration site and is overex-pressed in retrovirally induced murine myeloid leukemias. Here we show that this G protein-coupled receptor (GPCR) is also aberrantly expressed in a high percentage of human acute myeloid leukemias. We investigated the mechanism of transformation by Cb2 and demonstrate that aberrant expression of this receptor on hematopoietic precursor cells results in distinct effects depending on the ligand used. Cb2-expressing myeloid precursors migrate upon stimulation by the endocannabinoid 2-arachidonoylglycerol and are blocked in neutrophilic differentiation upon exposure to another ligand, CP55940. Both effects depend on the activation of G(alphai) proteins and require the mitogen-induced extracellular kinase/extracellular signal-regulated kinase (MEK/ERK) pathway. Down-regulation of cyclic adenosine monophosphate (cAMP) levels upon G(alphai) activation is important for migration induction but is irrelevant for the maturation arrest. Moreover, the highly conserved G protein-interacting DRY motif, present in the second intracellular loop of GPCRs, is critical for migration but unimportant for the differentiation block. This suggests that the Cb2-mediated differentiation block requires interaction of G(alphai) proteins with other currently unknown motifs. This indicates a unique mechanism by which a transforming GPCR, in a ligand-dependent manner, causes 2 distinct oncogenic effects: altered migration and block of neutrophilic development.

Large-scale identification of disease genes involved in acute myeloid leukemia

Acute myeloid leukemia (AML) is a heterogeneous group of diseases in which chromosomal aberrations, small insertions or deletions, or point mutations in certain genes have profound consequences for prognosis. However, the majority of AML patients present without currently known genetic defects. Retroviral insertion mutagenesis in mice has become a powerful tool for identifying new disease genes involved in the pathogenesis of leukemia and lymphoma. Here we have used the Graffi-1.4 strain of murine leukemia virus, which causes predominantly AML, in a screen to identify novel genes involved in the pathogenesis of this disease. We report 79 candidate disease genes in common integration sites (CISs) and 15 genes whose family members previously were found to be affected in other studies. The majority of the identified sequences (60%) were not found in lymphomas and monocytic leukemias in previous screens, suggesting a specific involvement in AML. Although most of the virus integrations occurred in or near the 5' or 3' ends of the genes, suggesting deregulation of gene expression as a consequence of virus integration, 18 CISs were located exclusively within the genes, conceivably causing gene disruption.

p53 alterations in myeloid leukemia

Although most solid tumors contain inactivating mutations of the p53 tumor suppressor, hematological malignancies do not contain frequent alterations in the p53 gene (<20%). How these tumors arise in the presence of a super tumor suppressor like p53 remains to be elucidated. Given the number of downstream effectors of p53, it is likely that critical targets of p53 are inactivated in leukemia, bypassing the requirement for p53 gene mutations in these tumors. This review describes new biochemical and transcriptional activities of p53 as well as the status of p53 in acute myelogenous leukemia and chronic myelogenous leukemia.

Pathogenic pathways in acute myeloid leukemias

Despite the common clinical, hematological and prognostic features that define acute myeloid leukemia (AML) there is considerable heterogeneity among individual cases, suggesting different pathogenic pathways. Based on a simple theoretical model, according to the vital characteristics of the leukemic clone (proliferative rate and resistance to apoptosis) we propose a classification of AML into two broad categories: a) high leukemic clone vitality (HLV) AML, corresponding roughly to the World Health Organization (WHO) classification group of entities "AML with recurrent cytogenetic abnormalities" and b) low leukemic clone vitality (LLV) or "opportunistic" AML corresponding to the WHO groups "AML with multilineage dysplasia" and "therapy-related AML". HLV-AML leukemic clones are characterized by rate-limiting genomic mutations capable of conferring proliferation/survival advantage over a normal hematopoietic environment while in LLV-AML, the leukemic clones are not particularly proliferative or apoptosis-resistant, but are nevertheless selected against an impaired, previously damaged hematopoietic environment. Such a pathogenesis-oriented classification might have therapeutic and prognostic implications, providing a theoretical basis for a further adaptation of the current standard treatment strategies to the individual characteristics of the AML patients.

Childhood and adolescent lymphoid and myeloid leukemia

Remarkable progress has been made in the past decade in the treatment and in the understanding of the biology of childhood lymphoid and myeloid leukemias. With contemporary improved risk assessment, chemotherapy, hematopoietic stem cell transplantation and supportive care, approximately 80% of children with newly diagnosed acute lymphoblastic leukemia and 50% of those with myeloid neoplasm can be cured to date. Current emphasis is placed not only on increased cure rate but also on improved quality of life. In Section I, Dr. Ching-Hon Pui describes certain clinical and biologic features that still have prognostic and therapeutic relevance in the context of contemporary treatment programs. He emphasizes that treatment failure in some patients is not due to intrinsic drug resistance of leukemic cells but is rather caused by suboptimal drug dosing due to host compliance, pharmacodynamics, and pharmacogenetics. Hence, measurement of minimal residual disease, which accounts for both the genetic (primary and secondary) features of leukemic lymphoblasts and pharmacogenomic variables of the host, is the most reliable prognostic indicator. Finally, he contends that with optimal risk-directed systemic and intrathecal therapy, cranial irradiation may be omitted in all patients, regardless of the presenting features. In Section II, Dr. Martin Schrappe performs detailed analyses of the prognostic impact of presenting age, leukocyte count, sex, immunophenotype, genetic abnormality, early treatment response, and in vitro drug sensitivity/resistance in childhood acute lymphoblastic leukemia, based on the large database of the Berlin-Frankfurt-Münster consortium. He also succinctly summarizes the important treatment components resulting in the improved outcome of children and young adolescents with this disease. He describes the treatment approach that led to the improved outcome of adolescent patients, a finding that may be applied to young adults in the second and third decade of life. Finally, he believes that treatment reduction under well-controlled clinical trials is feasible in a subgroup of patients with excellent early treatment response as evidenced by minimal residual disease measurement during induction and consolidation therapy. In Section III, Dr. Raul Ribeiro describes distinct morphologic and genetic subtypes of acute myeloid leukemia. The finding of essentially identical gene expression profiling by DNA microarray in certain specific genetic subtypes of childhood and adult acute myeloid leukemia suggests a shared leukemogenesis. He then describes the principles of treatment as well as the efficacy and toxicity of various forms of postremission therapy, emphasizing the need of tailoring therapy to both the disease and the age of the patient. Early results suggest that minimal residual disease measurement can also improve the risk assessment in acute myeloid leukemia, and that cranial irradiation can be omitted even in those with central-nervous-system leukemia at diagnosis. In Section IV, Dr. Charlotte Niemeyer describes a new classification of myelodysplastic and myeloproliferative diseases in childhood, which has greatly facilitated the diagnosis of myelodysplastic syndromes and juvenile myelomonocytic leukemia. The recent discovery of somatic mutations in PTPN11 has improved the understanding of the pathobiology and the diagnosis of juvenile myelomonocytic leukemia. Together with the findings of mutations in RAS and NF1 in the other patients, she suggests that pathological activation of RAS-dependent pathways plays a central role in the leukemogenesis of this disease. She then describes the various treatment approaches for both juvenile myelomonocytic leukemia and myelodysplastic syndromes in the US and Europe, emphasizing the differences between childhood and adult cases for the latter group of diseases. She also raises some controversial issues regarding treatment that will require well-controlled international clinical trials to address.

[Abnormal reaction for anaesthetics in a critically ill child with acute myeloid leukemia--case report]

The authors present a case report of an abnormal reaction for anaesthetics correlated with cytostatic therapy in the course of preparation time for bone marrow transplantation due to acute myeloid leukemia. Problems of pharmacological interaction of ketamine and benzodiazepines are emphasized. Special attention was paid to the risk of abnormal drug reactions during general anaesthesia in children with leukemia.

Telomerase is limiting the growth of acute myeloid leukemia cells

Telomeres play an important role in the proliferation and senescence of normal and malignant cells. To test the role of telomerase in acute myeloid leukemia (AML), we expressed the telomerase reverse transcriptase (hTERT) gene, a dominant-negative hTERT (DN-hTERT) (D868A, D869A) gene, or a gene encoding green fluorescence protein (GFP) in the leukemia cell line K562 and in primary AML cells from different patients, using retroviral vectors. Cells transduced with hTERT exhibited elevated levels of telomerase activity compared to GFP controls, whereas cells expressing DN-hTERT had decreased telomerase activity. K562 populations transduced with DN-hTERT showed reduced clonogenicity, telomere dysfunction and increased numbers of apoptotic cells compared to GFP- or hTERT-transduced cells. Two of four clones transduced with DN-hTERT died after 30 and 53 population doublings, respectively. Transduced AML cells were tested in primary colony-forming unit (CFU) and suspension culture assays. Relative to hTERT- and GFP-transduced controls, AML cells transfected with DN-hTERT produced fewer CFU and showed lower engraftment after transplantation into sublethally irradiated beta(2)-m(-/-) nonobese diabetic/severe combined immunodeficient mice. We conclude that telomerase is limiting the growth of the leukemic cell line K562 and primary AML progenitor cells. Our data warrant further studies of the therapeutic use of telomerase inhibitors in AML.

Caffeine induces G2/M arrest and apoptosis via a novel p53-dependent pathway in NB4 promyelocytic leukemia cells

Methylxantine derivative, caffeine, is known to prevent the p53-dependent apoptosis pathway via inhibition of ATM (ataxia telangiectasia mutated) kinase, which activates p53 by phosphorylation of the Ser-15 residue. In contrast, it has been reported that caffeine induces p53-mediated apoptosis through Bax protein in non-small-cell lung cancer cells. Therefore, the effects of caffeine on cellular growth in malignant cells are controversial. We investigated the effects of caffeine on cell proliferation, cell cycle progression, and induction of apoptosis in NB4 promyelocytic leukemia cells containing wild-type p53. Caffeine suppressed the cellular growth of NB4 cells in a dose- and time-dependent manner. Caffeine induced G(2)/M phase cell cycle arrest in NB4 cells in association with the induction of phosphorylation at the Ser-15 residue of p53 and induction of tyrosine phosphorylation of cdc2. Expression of Bax protein was increased in NB4 cells after treatment with caffeine. Interestingly, the antisense oligonucleotides for p53 significantly reduced p53 expression and caffeine-induced G(2)/M phase cell cycle arrest in NB4 cells. These results suggest that caffeine induces cell cycle arrest and apoptosis in association with activation of p53 by a novel pathway to phosphorylate the Ser-15 residue and induction of phosphorylation of cdc 2 in leukemic cells with normal p53.

The final phase in acute myeloid leukaemia (AML). A study on bleeding, infection and pain

To increase the knowledge of the final phase of acute myeloid leukaemia (AML) a retrospective review of the medical and nursing records of 106 adult patients with AML who had died in 1995-1997 was made. A total of 27 patients were treated with curative intent at the time of death and 79 patients were prescribed palliative care. From the documentation, an evaluation of the frequency and severity of bleeding and pain episodes was made during their last week in life, and the occurrence of infection criteria was studied. Notations on bleeding were found in 44%, infection in 71% and pain in 76% of the patients. In 54% of the morphine administration days, no information on the effect of given morphine treatment was registered. To give AML patients in the final phase, the best possible treatment, skills in palliative medicine and palliative care are important.

The role of a Runt domain transcription factor AML1/RUNX1 in leukemogenesis and its clinical implications

A Runt domain transcription factor AML1/RUNX1 is essential for generation and differentiation of definitive hematopoietic stem cells. AML1 is the most frequent target of chromosomal translocations in acute leukemias. Several chimeric proteins such as AML1-MTG8 and TEL-AML1 have transdominant properties for wild-type AML1 and acts as transcriptional repressors. The transcriptional repression in AML1 fusion proteins is mediated by recruitment of nuclear corepressor complex that maintains local histone deacetylation. Inhibition of the expression of AML1-responsive genes leads to a block in hematopoietic cell differentiation and consequent leukemic transformation. On the other hand, mutations in the Runt domain of the AML1 are identified in both sporadic acute myeloblastic leukemia (AML) without AML1 translocation and familial platelet disorder with predisposition to AML. These observations indicate that a decrease in AML1 dosage resulting from chromosomal translocations or mutations contributes to leukemogenesis. Furthermore, dysregulated chromatin remodeling and transcriptional control appears to be a common pathway in AML1-associated leukemias that could be an important target for the development of new therapeutic agents.

The interaction of daunorubicin and mitoxantrone with the red blood cells of acute myeloid leukemia patients

The effect of DNR and MIT on erythrocyte membrane structure was examined using Electron Spin Resonance spectroscopy and the fluorimetric technique. The results suggest that the in vivo interaction of the drugs with the RBCs of AML patients led to a perturbation in the structure of plasma membrane components. Differences between DNR and MIT were only noted in the interaction of the drugs with deeper regions of the lipid bilayer

Karyotype instability between diagnosis and relapse in 117 patients with acute myeloid leukemia: implications for resistance against therapy

The instability of the karyotype may play a role in the development of refractoriness of acute myeloid leukemia (AML) to anti-leukemic therapy. Therefore, in the current study cytogenetic analyses were performed in 117 patients with AML both at diagnosis and at relapse. Changes in karyotype were observed in 38% (36% of initially normal karyotypes, 39% of initially aberrant karyotypes). An evolution of karyotype, ie the acquisition of further aberrations in addition to those present at diagnosis, occurred more frequently in patients with unfavorable karyotypes at diagnosis as compared to all others (60% vs 32%, P = 0.0095). The duration from initial diagnosis to relapse was significantly shorter in cases with an evolution of the aberrant karyotype as compared to cases with no changes in the aberrant karyotype between diagnosis and relapse or with solely regression of aberrations at relapse (9.2 +/- 4.4 vs14.0 +/- 8.5 months, P = 0.0081). In an additional analysis, another cohort of 120 patients with refractory and relapsed AML who were treated uniformly within the respective trial of the German AML Cooperative Group was analyzed cytogenetically at diagnosis and at relapse to further prove the prognostic impact of karyotype aberrations at relapse. Karyotypes were prognostically favorable, intermediate, unfavorable and not available in 8%, 50%, 17% and 25% at diagnosis and in 8%, 49%, 21% and 22% at relapse, respectively. Karyotype aberrations at diagnosis had no impact on response to therapy (P = 0.32) but influenced survival and event-free survival significantly (P = 0.03 and P = 0.02). In contrast, karyotype aberrations at relapse strongly influenced response to therapy (P = 0.05), survival (P = 0.01), and event-free survival (P = 0.002). These data suggest that the instability of the karyotype between diagnosis and relapse and thus karyotype aberrations at relapse in particular contribute to the refractoriness of AML to anti-leukemic therapy.

Characteristics and outcome of t(8;21)-positive childhood acute myeloid leukemia: a single institution's experience

To elucidate the clinical and biological features of childhood acute myeloid leukemia (AML) with the t(8;21), we reviewed the records of patients with AML treated at St Jude Children's Research Hospital over a 17-year period (1980 to 1996). Of 298 patients with AML, 40 (13%) had blast cells that contained the t(8;21). This translocation was associated with a high frequency of French-American-British M2 morphology (82%) and the presence of granulocytic sarcoma (23%). Molecular analysis detected the AML1-ETO fusion transcript in all 25 cases with the t(8;21) tested, but failed to identify additional cases with AML1-ETO among the 127 cases with other cytogenetic findings. Compared to patients with other genetic abnormalities, those with the t(8;21) were less likely to have internal tandem duplications of the FLT3 gene (none of 10 vs 16 of 68). The 6-year overall survival estimate was 55% +/- 9% and the event-free survival estimate, 33% +/- 7%. Of the clinical and biological features examined, only gender was prognostically significant: the 6-year overall survival estimate for males was 68% +/- 10%, compared to 33% +/- 11 for female patients (P = 0.03). Treatment outcome was not influenced by the chemotherapy regimen used or by the use of autologous hematopoietic stem cell transplantation. These results suggest that t(8;21)-positive AML represents a heterogeneous disease with variable outcome. The reported favorable outcome for t(8;21)-positive AML in other studies may be due to the use of high-dose cytarabine.

CD133 (AC133) expression on AML cells and progenitors

BACKGROUND

AML blasts differ in their functional capability, creating a hierarchy of progenitors. CD133 (AC133) is a newly described transmembrane protein expressed on CD34(+) and CD34(-) normal progenitors. We characterized the prognostic significance of CD133 expression in AML and expression of CD133 on AML progenitors thought to be responsible for maintaining this disease.

METHODS

AML cells from 102 patients were analyzed for CD133 and CD34 expression, and correlated with outcome in 92 treated patients. AML cells were also FACS sorted into CD34(+)/CD133(+), CD34(+)/CD133(-), CD34(-)/CD133(+) and CD34(-)/CD133(-) subfractions, and assayed in vitro in colony-forming assay (CFU) and in suspension culture (SC) assay for up to 8 weeks, and in vivo in non-obese diabetic (NOD)/SCID mice to determine the phenotype of progenitors detected in these assays.

RESULTS

CD133 expression was not correlated with event-free or overall survival, FAB subtype, cytogenetic abnormality or WBCC, but was correlated with CD34 expression. Primary AML CFU were present in all four sorted fractions. After an increasing period of time in SC, a higher proportion of cells capable of forming leukemic CFU were found in the CD34(+)/CD133(+) subfraction. Cells capable of producing leukemic engraftment in NOD/SCID mice were found in all subfractions, including the CD34(-)/CD133(-) subfraction in many patients.

DISCUSSION

CD133 is not useful as a prognostic marker in AML. CD133 is expressed with CD34 on most primitive leukemic progenitors detected in vitro, however, in vivo progenitors could not be purified using CD133 in these patients.