Effect of priming with granulocyte colony-stimulating factor on the outcome of chemotherapy for acute myeloid leukemia

Time from diagnosis to treatment initiation predicts survival in younger, but not older, acute myeloid leukemia patients

Acute myeloid leukemia (AML) is considered an oncologic emergency. Delaying induction chemotherapy until molecular testing results return, may benefit some patients but harm others. We examined the effect of time from AML diagnosis to treatment (TDT) on complete remission (CR) and overall survival (OS), using patient characteristics available at diagnosis. Regression models were applied to older (> or = 60 years) and younger (< 60 years) adults, controlling for age, baseline white blood cell count, secondary AML (sAML), and performance status. Median patient age was 60 years (range, 17-87 years), TDT 4 days (range, 1-78 days), and 45% had sAML. Cytogenetic risk distribution was: favorable, 8%; intermediate, 66%; unfavorable, 26%. CR rate was 67% and median OS was 68 weeks in patients younger than 60 years; 55% and 33 weeks in older patients, respectively. In univariate and multivariate analyses, longer TDT was associated with worse CR and OS in younger (univariate: P < .001 in both; multivariate: P < .001 and P = .001, respectively), but not older patients (univariate: P = .45, P = .19; multivariate: P = .63, P = .30, respectively). Results did not change with inclusion of cytogenetic data or in risk group subsets. AML therapy should be initiated immediately in younger patients. Delaying treatment does not seem harmful in older patients, allowing individualized approaches.

Acute myeloid leukemia in the elderly

The incidence of acute myeloid leukemia (AML) is increasing with age. As the results associated with standard intensive chemotherapy remain particularly disappointing in older patients, they represent an ideal target population for clinical and therapeutic investigations. Current attempts are to better define those who may draw a significant benefit from intensive chemotherapy, in order to test new less intensive approaches in the remaining patients. Hopefully, a lot of promising alternative therapies are emerging, including hypomethylating agents, histone deacetylase inhibitors, monoclonal antibodies, or chemotherapeutic agents such as cloretazine or clofarabine. Reduced-intensity conditioning stem cell transplantation or other various immunological approaches represent another way of investigation.

Somatic CEBPA mutations are a frequent second event in families with germline CEBPA mutations and familial acute myeloid leukemia

PURPOSE

The transcription factor CCAAT/enhancer binding protein-alpha (CEBPA) is crucial for normal myeloid differentiation. Mutations in the CEBPA gene are found in subsets of patients with acute myeloid leukemia (AML). Recently, three families were reported in whom several family members had germline CEBPA mutations and subsequently developed AML. Whereas familial AML is considered a rare event, the frequency of CEBPA germline mutations in AML is not known.

PATIENTS AND METHODS

In this study, we screened 187 consecutive AML patients for CEBPA mutations at diagnosis. We detected 18 patients (9.6%) with CEBPA mutations. We then analyzed remission samples and constitutive DNA from these patients.

RESULTS

We found that two (11.1%) of 18 AML patients with CEBPA mutations carried a germline N-terminal frameshift CEBPA mutation. Interestingly, additional members in the families of both of these patients have been affected by AML, and the germline CEBPA mutations were also observed in these patients. Additional somatic mutations in AML patients with germline CEBPA mutations in the two families comprised in-frame C-terminal CEBPA mutations in two patients, two nonsilent CEBPA point mutations in one patient, and monosomy 7 in one patient.

CONCLUSION

This study shows, for the first time to our knowledge, that germline CEBPA mutations are frequently observed among AML patients with CEBPA mutations. Including the families with germline CEBPA mutations reported previously, additional somatic CEBPA mutations represent a frequent second event in AML with germline CEBPA mutations. Our data strongly indicate that germline CEBPA mutations predispose to AML and that additional somatic CEBPA mutations contribute to the development of the disease.

Long-term follow-up of allogeneic hematopoietic stem cell transplantation for de novo acute myelogenous leukemia with a conditioning regimen of total body irradiation and granulocyte colony-stimulating factor-combined high-dose cytarabine

We retrospectively evaluated the efficacy and safety of total body irradiation (TBI) and granulocyte colony-stimulating factor (G-CSF)-combined high-dose cytarabine as a conditioning regimen for allogeneic hematopoietic stem cell transplantation (HSCT) in patients with de novo acute myelogenous leukemia (AML). The conditioning regimen consisted of 12 Gy of TBI followed by high-dose cytarabine (3 g/m(2)) every 12 hours for 4 days in combination with the continuous administration of G-CSF. Stem cell sources included bone marrow or peripheral blood stem cells (PBSC) from human leukocyte antigen (HLA)-identical siblings (n = 24), or bone marrow from HLA serologically matched unrelated donors (n = 26). Fifty patients (median age, 38 years) were evaluated. At HSCT, 35 patients were in the first or second complete remission (CR1/2), and 15 patients were not in remission (n = 14) or in the third CR (n = 1). Thirty-six of 50 patients are currently alive, with a median follow-up period of 5.6 years (range: 1.1-12.1 years). The 5-year estimated overall survival (OS) and disease-free survival (DFS) rates were 85.5% (95% confidence interval [CI], 73.7%-97.3%) and 82.1% (95% CI, 69.0%-95.2%) in patients with AML in the first or second CR, 46.7% (95% CI, 21.4%-72.0%), and 40.0% (95% CI, 15.3%-64.7%) in patients with AML in other stages. The 2-year cumulative incidence of treatment-related mortality (TRM) of all patients was 10.4% (95% CI, 1.8%-18.6%). The only factors affecting the OS and DFS were disease status at transplant and cytogenetics by multivariate analysis. These results suggest that G-CSF-combined high-dose cytarabine could be a promising component of the conditioning regimen for allogeneic HSCT for AML, providing a high DFS and low TRM.

Monosomal karyotype in acute myeloid leukemia: a better indicator of poor prognosis than a complex karyotype

PURPOSE

To investigate the prognostic value of various cytogenetic components of a complex karyotype in acute myeloid leukemia (AML).

PATIENTS AND METHODS

Cytogenetics and overall survival (OS) were analyzed in 1,975 AML patients age 15 to 60 years.

RESULTS

Besides AML with normal cytogenetics (CN) and core binding factor (CBF) abnormalities, we distinguished 733 patients with cytogenetic abnormalities. Among the latter subgroup, loss of a single chromosome (n = 109) conferred negative prognostic impact (4-year OS, 12%; poor outcome). Loss of chromosome 7 was most common, but outcome of AML patients with single monosomy -7 (n = 63; 4-year OS, 13%) and other single autosomal monosomies (n = 46; 4-year OS, 12%) did not differ. Structural chromosomal abnormalities influenced prognosis only in association with a single autosomal monosomy (4-year OS, 4% for very poor v 24% for poor). We derived a monosomal karyotype (MK) as a predictor for very poor prognosis of AML that refers to two or more distinct autosomal chromosome monosomies (n = 116; 4-year OS, 3%) or one single autosomal monosomy in the presence of structural abnormalities (n = 68; 4-year OS, 4%). In direct comparisons, MK provides significantly better prognostic prediction than the traditionally defined complex karyotype, which considers any three or more or five or more clonal cytogenetic abnormalities, and also than various individual specific cytogenetic abnormalities (eg, del[5q], inv[3]/t[3;3]) associated with very poor outcome.

CONCLUSION

MK enables (in addition to CN and CBF) the prognostic classification of two new aggregates of cytogenetically abnormal AML, the unfavorable risk MK-negative category (4-year OS, 26% +/- 2%) and the highly unfavorable risk MK-positive category (4-year OS, 4% +/- 1%).

Ligand-induced Flt3-downregulation modulates cell death associated proteins and enhances chemosensitivity to idarubicin in THP-1 acute myeloid leukemia cells

Sustained ligand stimulation of the receptor tyrosine kinase Flt3 resulted in its downregulation and a refractory signaling phase in primary acute myeloid leukemia (AML) cells and in the AML cell line THP-1. Stable isotope amino acid labeling in cell culture and mass spectrometry were used to compare protein expression patterns in THP-1 before and after Flt3-downregulation. 375 distinct proteins were identified where ATP-dependent RNA helicase DDX3, HNRPU, Matrin-3, Importin-7 and Bax were among the 25 most upregulated proteins and Hausp/UBP7, UBE2N and ERp29 among the 17 most downregulated. THP-1 cells with receptor downregulation were sensitized to idarubicin-induced apoptosis but not cytarabine. We hypothesize that FL-induced receptor modulation may chemosensitize selected AML subsets.

Is it important to decipher the heterogeneity of "normal karyotype AML"?

Almost half of adult acute myelogenous leukemia (AML) is normal cytogenetically, and this subgroup shows a remarkable heterogeneity of genetic mutations at the molecular level and an intermediate response to therapy. The finding of recurrent cytogenetic abnormalities has influenced, in a primary way, the understanding and treatment of leukemias. Yet "normal karyotype AML" lacks such obvious abnormalities, but has a variety of prognostically important genetic abnormalities. Thus, the presence of a FLT3-ITD (internal tandem duplication), MLL-PTD (partial tandem duplication), or the increased expression of ERG or EVI1 mRNAs confer a poor prognosis, and an increased risk of relapse. In contrast, the presence of cytoplasmic nucleophosmin or C/EBPA mutations is associated with lower relapse rates and improved survival. Although resistance to treatment is associated with specific mutations, the degree to which the leukemia resembles a stem cell in its functional properties may provide greater protection from the effects of treatment. Although usually all of the circulating leukemia cells are cleared following treatment, a small residual population of leukemic cells in the bone marrow persists, making this disease hard to eradicate. Increased understanding of the biological consequences of at least some of these mutations in "normal karyotype AML" is leading to more targeted approaches to develop more effective treatments for this disease.

Continuous drip infusion of low dose cytarabine and etoposide with granulocyte colony-stimulating factor for elderly patients with acute myeloid leukaemia ineligible for intensive chemotherapy

BACKGROUNDS AND OBJECTIVES

The optimal strategy for the management of elderly patients with acute myeloid leukaemia (AML) is still controversial. We previously reported the effectiveness of low dose cytarabine (Ara-C) and etoposide (VP-16) (AV therapy) for those elderly AML patients ineligible for intensive chemotherapy. We initiated the present feasibility study to improve the efficacy by using glanulocyte-colony stimulating factor (G-CSF) with AV therapy (AVG therapy).

PATIENTS AND METHODS

The eligibility for enrolment was AML patients according to the World Health Organization (WHO) criteria who were over 60 years of age and who had difficulty in tolerating intensive chemotherapy due to their poor performance status (PS) or some comorbidities. They were given continuous drip infusion of Ara-C (20 mg/body) and VP-16 (50 mg/body) for 7-14 days, and were also simultaneously administered G-CSF (150 microg/m2) once daily.

RESULTS

The median age of consecutively enrolled 25 patients was 73 years. Eighteen (72%) patients achieved complete remission (CR). The 1-year overall survival (OS) and the 3-year OS rates were 69% and 22%, respectively. The 1-year disease free survival (DFS) rate in CR patients was 44%. The major regimen related toxicities of grade 3 or 4 were only febrile neutropenia in 15 patients (60%). No regimen-related mortality was observed.

CONCLUSION

AVG therapy was therefore found to be an effective and well-tolerated regimen for remission induction in elderly AML patients with poor PS or comorbidity.

The role of timed sequential chemotherapy in adult acute myelogenous leukemia

Consecutive trials of timed sequential chemotherapy (TSC) have been conducted in adults with acute myelogenous leukemia. The rationale for TSC was based on the observation that leukemic cells can be recruited synchronously into the cell cycle after initial intensive therapy, at which time they may become more susceptible to killing by chemotherapeutic agents. Achieving complete remission is essential for prolonged disease-free survival and may affect long-term outcome. TSC has led to higher rates of complete remission and has improved long-term outcomes. This article reviews the results of important trials in which TSC was used as an induction regimen in de novo, relapsed, or refractory acute myelogenous leukemia or as postremission therapy.

MicroRNA expression profiling in relation to the genetic heterogeneity of acute myeloid leukemia

Acute myeloid leukemia (AML) is a highly diverse disease characterized by various cytogenetic and molecular abnormalities. MicroRNAs are small noncoding RNAs that show variable expression during myeloid differentiation. MicroRNA expression in marrow blasts in 215 cases of newly diagnosed and (cyto)genetically defined AML was assessed using quantitative reverse-transcription-polymerase chain reaction (RT-PCR) for 260 human microRNAs. In the same series, mRNA gene expression profiles were established, allowing a direct comparison between microRNA and mRNA expression. We show that microRNA expression profiling following unsupervised analysis reveals distinctive microRNA signatures that correlate with cytogenetic and molecular subtypes of AML (ie, AMLs with t(8;21), t(15;17), inv(16), NPM1, and CEBPA mutations). Significantly differentially expressed microRNAs for genetic subtypes of AML were identified. Specific microRNAs with established oncogenic and tumor suppressor functions, such as microRNA-155, microRNA-21, and let-7, appear to be associated with particular subtypes. Combinations of selected sets of microRNAs could predict cytogenetically normal AML with mutations in the genes of NPM1 and CEBPA and FLT3-ITD with similar accuracy as mRNA probe set combinations defined by gene expression profiling. MicroRNA expression apparently bears specific relationships to the heterogeneous pathobiology of AML. Distinctive microRNA signatures appear of potential value in the clinical diagnosis of AML.

Combination chemotherapy with low-dose cytarabine, homoharringtonine, and granulocyte colony-stimulating factor priming in patients with relapsed or refractory acute myeloid leukemia

As sensitization of leukemic cells with granulocyte colony-stimulating factor (G-csf) can enhance the cytotoxicity of chemotherapy in acute myeloid leukemia (AML), a pilot study was conducted in order to evaluate the effect of G-csf priming combined with low-dose chemotherapy in patients with relapsed and refractory AML. The regimen, G-HA, consisted of cytarabine 7.5 mg/m2/12 hr by subcutaneous injection, days 1-14, homoharringtonine 1.5 mg/m2/day by intravenous continuous infusion, days 1-14, and G-csf 150 microg/m2/day by subcutaneous injection, days 0-14. Thirty-six AML patients were enrolled, 23 refractory and 13 relapsed. Eighteen patients (50%, 95% confidence interval: 33-67%) achieved complete remission (CR) with a median CR duration of 7.2 months, and two elderly patients continued a regimen of maintenance therapy and remained in remission for 26.3 and 14.1 months, respectively, as of last follow-up. Eight patients (22%) experienced neutropenia (median duration: 6 days; range: 2-22 days). Thirteen of the 36 (36%) developed severe infections. Grade 1-2 nonhematologic toxicities were documented, including nausea and vomiting (20%), liver function abnormality (6%), and heart function abnormality (6%). No central nervous system and kidney toxicity was observed. The G-HA regimen is effective in remission induction for refractory and relapsed AML patients and well tolerated in maintenance therapy in some subgroups of elderly patients. Further studies are necessary to elucidate optimum dose and schedule for this regimen to enhance the treatment efficacy of relapsed or refractory AML patients.

High EVI1 levels predict adverse outcome in acute myeloid leukemia: prevalence of EVI1 overexpression and chromosome 3q26 abnormalities underestimated

Inappropriate expression of EVI1 (ecotropic virus integration-1), in particular splice form EVI1-1D, through chromosome 3q26 lesions or other mechanisms has been implicated in the development of high-risk acute myeloid leukemia (AML). To validate the clinical relevance of EVI1-1D, as well as of the other EVI1 splice forms and the related MDS1/EVI1 (ME) gene, real-time quantitative polymerase chain reaction was performed in 534 untreated adults with de novo AML. EVI1-1D was highly expressed in 6% of cases (n = 32), whereas 7.8% were EVI1(+) (n = 41) when all splice variants were taken into account. High EVI1 predicted a distinctly worse event-free survival (HR = 1.9; P = .002) and disease-free survival (HR = 2.1, P = .006) following multivariate analysis. Importantly, we distinguished a subset of EVI1(+) cases that lacked expression of ME (EVI1(+)ME(-); n = 17) from cases that were ME(+) (EVI1(+)ME(+); n = 24). The atypical EVI1(+)ME(-) expression pattern exhibited cytogenetically detectable chromosomal 3q26 breakpoints in 8 cases. Fluorescence in situ hybridization revealed 7 more EVI1(+)ME(-) cases that carried cryptic 3q26 breakpoints, which were not found in the EVI1(+)ME(+) group. EVI1(+)ME(-) expression predicts an extremely poor prognosis distinguishable from the general EVI1(+) AML patients (overall survival [OS]: P < .001 and event-free survival [EFS]: P = .002). We argue that EVI1/ME quantitative expression analysis should be implemented in the molecular diagnostic procedures of AML.

Canadian supportive care recommendations for the management of neutropenia in patients with cancer

Hematologic toxicities of cancer chemotherapy are common and often limit the ability to provide treatment in a timely and dose-intensive manner. These limitations may be of utmost importance in the adjuvant and curative intent settings. Hematologic toxicities may result in febrile neutropenia, infections, fatigue, and bleeding, all of which may lead to additional complications and prolonged hospitalization. The older cancer patient and patients with significant comorbidities may be at highest risk of neutropenic complications. Colony-stimulating factors (csfs) such as filgrastim and pegfilgrastim can effectively attenuate most of the neutropenic consequences of chemotherapy, improve the ability to continue chemotherapy on the planned schedule, and minimize the risk of febrile neutropenia and infectious morbidity and mortality. The present consensus statement reviews the use of csfs in the management of neutropenia in patients with cancer and sets out specific recommendations based on published international guidelines tailored to the specifics of the Canadian practice landscape. We review existing international guidelines, the indications for primary and secondary prophylaxis, the importance of maintaining dose intensity, and the use of csfs in leukemia, stem-cell transplantation, and radiotherapy. Specific disease-related recommendations are provided related to breast cancer, non-Hodgkin lymphoma, lung cancer, and gastrointestinal cancer. Finally, csf dosing and schedules, duration of therapy, and associated acute and potential chronic toxicities are examined.

Acute Myeloid Leukemia: Epidemiology and Etiology

Although acute leukemias are infrequent diseases, they are highly malignant neoplasms responsible for a large number of cancer-related deaths. Acute myeloid leukemia (AML) is the most common type of leukemia in adults, yet continues to have the lowest survival rate of all leukemias. While results of treatment have improved steadily in younger adults over the past 20 years, there have been limited changes in survival among individuals of age >60 years [1, 2].

Acute Myeloid Leukemia: The Challenge of Capturing Disease Variety

The difference between success and failure of treatment of acute myeloid leukemia (AML) is largely determined by genotypic leukemia-specific differences among patients. The diversity of AML genotypes result from somatic genetic alterations settling down in succession in an individual’s leukemia clone during the development of the disease. Gene mutations, gene expression abnormalities and other molecular alterations (e.g., microRNA variations) affect critical functions in AML cells, and may exert profound effects on the therapeutic response and outcome of the disease. Prototypes of common clinically significant gene aberrations involve transcription factors, signaling molecules and growth factor receptors. The expanding knowledge in this area allowing for risk stratified therapy decisions and the development of targeted drug therapy, is becoming an increasingly important part of the modern individualized clinical management of AML. This chapter highlights recent insights into the diagnostic, prognostic and therapeutic impact of chromosomal (e.g., the so-called monosomal karyotype) as well as particular genomic abnormalities, and presents examples of decision algorithms for individualized therapy.

Gemtuzumab ozogamicin, cytosine arabinoside, G-CSF combination (G-AraMy) in the treatment of elderly patients with poor-prognosis acute myeloid leukemia

BACKGROUND

Gemtuzumab ozogamicin (GO) is effective as single agent in the treatment of acute myeloid leukemia (AML). We evaluated efficacy and safety of a chemotherapy including growth factors, cytarabine, and GO (G-AraMy) in the treatment of poor-prognosis AML in elderly patients.

PATIENTS AND METHODS

In three Italian hematology departments from September 2003 to September 2006, 53 elderly patients [median age 69 years (range 65-77)] with untreated or primary refractory/relapsed AML were enrolled on the combination G-AraMy administered according to two consecutive schedules (G-AraMy1 and G-AraMy2), with intensified consolidation in the second. Twenty-three of 53 patients had a secondary acute myeloid leukemia (sAML).

RESULTS

The overall response rate was 57%. The most common adverse event was myelosuppression. Seven patients died in induction (13%). No differences for response rate and toxicity profile were observed between untreated and primary resistant/relapsed patients, de novo AML and sAML, and in the two treatment trials. Median disease-free survival and overall survival were 8 months (range 2-23+) and 9 months (range 2-24+).

CONCLUSIONS

G-AraMy therapy may be considered an useful treatment approach for poor-risk elderly AML patients, with a complete remission rate comparable to literature data with reduced side-effects, also in a poor-prognosis population.

Review of the value of colony stimulating factors for prophylaxis of febrile neutropenic episodes in adult patients treated for haematological malignancies

Chemotherapy-induced neutropenia is a major dose-limiting toxicity of systemic cancer chemotherapy that can lead to fever and infection, requiring prompt analysis and in-patient treatment with broad-spectrum antibiotics. Complicated neutropenia may lead to reduction and/or delay of systemic anti-cancer treatment, which may compromise outcome. Haematopoietic growth factors have the ability to augment haematopoietic cell cycling and are used to facilitate more dose-intense treatments and to decrease treatment-related complications. This review focuses on randomised trials that investigated the use of colony-stimulating factors (CSF) to prevent treatment-related febrile complications in haematological malignancies in (younger) adult patients. In general, these studies demonstrated that CSF reduced the duration of severe neutropenia but not always its febrile complications; therefore inconsistent results regarding clinically relevant reduction of hospitalisation, duration of therapeutic antibiotics, infection-related or disease-related mortality and economic effects were reported. Current developments in treatment of haematological malignancies will pose new challenges as a shift in infectious pathogens can be expected.

MN1 overexpression induces acute myeloid leukemia in mice and predicts ATRA resistance in patients with AML

Overexpression of wild-type MN1 is a negative prognostic factor in patients with acute myeloid leukemia (AML) with normal cytogenetics. We evaluated whether MN1 plays a functional role in leukemogenesis. We demonstrate using retroviral gene transfer and bone marrow (BM) transplantation that MN1 overexpression rapidly induces lethal AML in mice. Insertional mutagenesis and chromosomal instability were ruled out as secondary aberrations. MN1 increased resistance to all-trans retinoic acid (ATRA)–induced cell-cycle arrest and differentiation by more than 3000-fold in vitro. The differentiation block could be released by fusion of a transcriptional activator (VP16) to MN1 without affecting the ability to immortalize BM cells, suggesting that MN1 blocks differentiation by transcriptional repression. We then evaluated whether MN1 expression levels in patients with AML (excluding M3-AML) correlated with resistance to ATRA treatment in elderly patients uniformly treated within treatment protocol AMLHD98-B. Strikingly, patients with low MN1 expression who received ATRA had a significantly prolonged event-free (P = .008) and overall (P = .04) survival compared with patients with either low MN1 expression and no ATRA, or high MN1 expression with or without ATRA. MN1 is a unique oncogene in hematopoiesis that both promotes proliferation/self-renewal and blocks differentiation, and may become useful as a predictive marker in AML treatment.

The criteria for bone marrow recovery post-myelosuppressive therapy for acute myelogenous leukemia: a quantitative study

CONTEXT

Although the early post-myelosuppressive chemotherapy pathologic changes of the marrow have been described, the rate and the histologic definition of recovery are not defined.

OBJECTIVE

To study the rate of recovery of bone marrow in patients given myelosuppressive therapy for acute myelogenous leukemia, establish the histologic criteria of recovered marrow, and correlate the recovery pattern with those patients who received a bone marrow transplant by using histology, peripheral blood, immunophenotyping, and computerized morphometry and mathematical slope equation.

DESIGN

We studied the post-myelosuppression recovery of the bone marrow to determine patterns and rate of recovery in 135 serial bone marrow biopsies of 51 patients. These patients were divided into 2 groups: 1 group of 28 cases diagnosed with acute myeloid leukemia, the majority treated with cytarabine (Ara-C) infusion for 7 days and daunorubicin intravenously daily for 3 days (7+3 regimen), and the other control group of 23 cases treated with chemotherapy or allogeneic bone marrow transplantation for a variety of hematologic malignancies. All biopsies during the recovery period were obtained before consolidation regimen. We used morphometry to calculate the cellularity and myeloid to erythroid ratio and quantified megakaryocytes CD10 versus time from day 14 onward. The absolute neutrophil and platelet counts for 28 cases were related to histologic recovery.

RESULTS

From day 14, we noted a differential slope of recovery of these patients with no difference in male and female patients, P = .45, but a difference between younger and older patients (>58.5 years), P = .03. After regenerative hyperplasia, the cellularity plateaus, the myeloid to erythroid ratio, and the megakaryocytes even out with platelet normalization, and the early CD10+ B cells rise from day 40 onward, P = .01. The patterns of recovery after day 60 of postchemotherapy and posttransplantation patients are similar. Complete histologic and peripheral blood recovery is noted at day 38 and thereafter.

CONCLUSIONS

By linear equation using at least 2 trephine biopsy specimens, the projected rate of cellular recovery may be determined, and 5 histologic features are associated with complete histologic recovery.

Current status of growth factors in the treatment of acute myeloid and lymphoblastic leukemia

The safety of granulocyte colony-stimulating factor (G-CSF) and granulocyte-macrophage colony-stimulating factor (GM-CSF) in patients with acute leukemia has been well established in numerous clinical trials. The primary aim of these studies was to determine whether CSFs, when used as adjuncts to intensive chemotherapy, reduced the duration of neutropenia, prevented febrile neutropenia, infections, and hospitalization rates, and improved response and overall outcome in patients with acute myeloid leukemia (AML) or acute lymphoblastic leukemia (ALL). Despite considerable efforts in divers clinical settings, the potential advantages of hematopoietic growth factors in the management of these leukemias remain inconclusive. In general, individual published trials have shown declines in the incidence and/or duration of neutropenia but have not consistently demonstrated a reduction in the overall frequency of infectious complications or the duration of hospitalization. Most protocols also have failed to show a benefit in terms of disease-free or overall survival. Nevertheless, improvements in "soft" clinical end points, such as incidence of severe infections, may be clinically important and contribute, even if only incrementally, to the patient's quality of life. Selection of those patients likely to benefit from growth factors in a specific clinical setting is a worthwhile endeavour.

Therapeutic targets in chronic myeloid leukaemia

Chronic myeloid leukaemia (CML) is a clonal disorder of the haemopoietic stem cell arising as a consequence of the formation of the bcr-abl oncogene. The particular molecular basis of this condition has enabled the development of therapies that selectively target diseased cells. The success of the rationally designed first-line therapy imatinib mesylate (IM) is tempered by the problems of disease persistence and resistance. Novel strategies have been identified to take forward therapy in CML and these will be discussed in this review. This work is generated from a review of published literature and contains particular insight into the work performed by our group in this field.

CTLA-4 expressed by chemoresistant, as well as untreated, myeloid leukaemia cells can be targeted with ligands to induce apoptosis

We have previously reported that about 80% of acute myeloid leukaemia (AML) samples tested at diagnosis constitutively expressed cytotoxic T-lymphocyte-associated antigen-4 (CTLA-4). The present study compared CTLA-4 expression and function of leukaemic cells from AML patients at diagnosis with those from AML patients resistant to conventional chemotherapy. We also explored the possibility of targeting CTLA-4 for apoptosis induction in chemoresistant AML cells. AML cells either from untreated patients (n = 15) or in chemoresistant phase (n = 10) were analysed for CTLA-4 protein and transcript expression by flow cytometry and reverse transcription-polymerase chain reaction respectively. CTLA-4 expression was similar in untreated and in chemoresistant samples and was not associated with patients' clinical features. In chemoresistant AML cells, CTLA-4 transduced an apoptotic signal on engagement with its recombinant ligands r-CD80 and r-CD86, which induced an average of 71% and 62% apoptotic cells, respectively, at highest concentration. Apoptosis was equally induced in untreated leukaemic cells accompanied by cleavage of procaspase-8 and -3. Thus, this study provides the first evidence that killing of leukaemic cells from AML patients may be obtained by the engagement of CTLA-4 with its ligands, opening the way to a novel potential therapeutic approach based on triggering the CTLA-4 molecule to circumvent chemoresistance in AML.

Effect of low-dose cytarabine and aclarubicin in combination with granulocyte colony-stimulating factor priming (CAG regimen) on the outcome of elderly patients with acute myeloid leukemia

The aim of this study was to evaluate the efficacy and toxicity of low-dose cytarabine and aclarubicin in combination with granulocyte colony-stimulating factor (G-CSF) protocol in elderly patients with acute myeloid leukemia (AML). A total of 50 elderly patients including 8 aged over 70 years were enrolled. All patients were treated with CAG regimen including low-dose cytarabine (10mg/m(2) every 12h, days 1-14), aclarubicin (10mg every day, days 1-8), and G-CSF (200 microg/m(2) every day, days 1-14) priming. The overall response rate was 72.0%, and 29 of 50 (58.0%) patients achieved complete remission, including 23 of 35 (65.8%) with previously untreated AML, 6 of 15 (40.0%) with refractory, relapsed or secondary AML, 4 of 8 (50.0%) aged over 70 years, 4 of 10 (40.0%) with unfavorable cytogenetic aberrations. The early death rate was 7.6%. The median overall survival was 14 months. Myelosuppression was mild to moderate, severe nonhematologic toxicity was not observed. Thus CAG priming regimen as the induction therapy is well tolerated and effective in elderly patients with AML.

Novel therapeutic agents in acute myeloid leukemia

Acute myeloid leukemia (AML) is an intrinsically resistant disease. Prognosis is poor for the majority of AML patients, based on age and/or adverse biologic features. Standard therapy for AML is highly toxic and poorly tolerated, particularly by the group of older patients for whom few useful therapies exist. Allogeneic hematopoietic stem cell transplantation is an important option for patients with high-risk AML during first remission, as well as for any patient in second or subsequent remission. Use of reduced intensity conditioning transplantations has made allogeneic stem cell transplantation available for a wider group of individuals, but the impact of this novel procedure on the natural history of AML is unknown. The major thrust of novel therapeutics in AML is development of so-called targeted therapies, which are based on exploitation of newly understood pathophysiological events critical for leukemogenesis. Such events include unbridled proliferation, failure to differentiate, stromal cell-mediated survival factors, and failure to undergo normal programmed cell death. Therapies developed to deal with these problems include inhibitors of ras physiology and activated tyrosine kinases, such as fms-like tyrosine kinase 3; histone deacetylase inhibitors, and DNA-hypomethylating agents, which promote transcription of silenced genes; angiogenesis inhibitors; and anti-bcl-2 agents, respectively. Challenges in therapeutic development include the likelihood that only a subset of AML patients will respond to any of these therapies, based on the patient's intrinsic pathophysiology as well as the fact that many of these agents will only work in conjunction with chemotherapy or other viable antileukemic therapies.

Targeted agents in AML: much more to do

To what degree has targeted therapy succeeded in acute myeloid leukemia (AML)? Targeted therapy has become a buzzword, with its meaning lost from overuse. In chronic myeloid leukemia (CML), gastrointestinal stromal cell tumor, and a small subset of patients with non-small cell lung cancer, a validated target has been identified and a highly specific therapeutic agent has been developed. Targeted therapy generally requires a pathophysiological Achilles heel in a tumor that can be exploited by nontoxic therapy. In most cases, the validated target has been a tyrosine kinase enzyme critical for tumor growth and survival. Are similar "drugable" targets available in AML? While our understanding of the pathophysiology of AML has advanced over the past decade, and some potential targets have been identified, no single agent will likely produce a significant proportion of remissions. On the other hand, nascent attempts with mild success have been achieved, yielding hope that this strategy will bear real fruit in the future.

Effect of priming with granulocyte-macrophage colony-stimulating factor in younger adults with newly diagnosed acute myeloid leukemia: a trial by the Acute Leukemia French Association (ALFA) Group

In a multicenter trial, 259 young adults (15-49 years) with newly diagnosed acute myeloid leukemia (AML) were first randomized to receive a timed-sequential induction regimen given either alone (135 patients) or concomitantly with granulocyte-macrophage colony-stimulating factor (GM-CSF) (124 patients). Patients reaching complete remission (CR) were then randomized to compare a timed-sequential consolidation to a postremission chemotherapy including four cycles of high-dose cytarabine followed by maintenance courses. In the appropriate arm, GM-CSF was given concurrently with chemotherapy during all cycles of consolidation. CR rates were significantly better in the GM-CSF arm (88 vs 78%, P<0.04), but did not differ after salvage. Patients receiving GM-CSF had a higher 3-year event-free survival (EFS) estimate (42 vs 34%), but GM-CSF did not impact on overall survival. Patients with intermediate-risk cytogenetics benefited more from GM-CSF therapy (P=0.05) in terms of EFS than patients with other cytogenetics. This was also confirmed when considering only patients following the second randomization, or subgroups defined by a prognostic index based on cytogenetics and the number of courses required for achieving CR. Priming of leukemic cells with hematopoietic growth factors is a means of enhancing the efficacy of chemotherapy in younger adults with AML.

Total body irradiation and granulocyte colony-stimulating factor-combined high-dose cytarabine as a conditioning regimen in allogeneic hematopoietic stem cell transplantation for advanced myelodysplastic syndrome: a single-institute experience

In this study, we retrospectively evaluated the efficacy and safety of total body irradiation (TBI) and granulocyte colony-stimulating factor (G-CSF)-combined high-dose cytarabine as a conditioning regimen for allogeneic hematopoietic stem cell transplantation (HSCT) in patients with advanced myelodysplastic syndrome (MDS). We evaluated 22 patients with advanced MDS, including refractory anemia with excess blasts (RAEB; n=10), RAEB in transformation (n=2), acute myelogenous leukemia transformed from MDS (n=6) and chronic myelomonocytic leukemia (n=4). The conditioning regimen consisted of 12 Gy of TBI and high-dose cytarabine (3 g/m(2)) every 12 h for 4 days, and the cytarabine was combined with continuous administration of G-CSF. The stem cell sources were bone marrow or peripheral blood stem cells from human leukocyte antigen (HLA)-identical siblings (n=12) and bone marrow from HLA serologically matched unrelated donors (n=10). Three patients experienced disease relapse, two of whom died of disease progression. Of 22 patients, 16 are currently alive and disease-free. The 5-year estimated overall survival, disease-free survival, relapse and non-relapse mortality rates are 76.7, 72.2, 16.6 and 14.1%, respectively. These results suggest that G-CSF-combined high-dose cytarabine could be a promising component of the conditioning regimen of allogeneic HSCT for advanced MDS, providing a low incidence of both relapse and treatment-related mortality.

Results of a HOVON/SAKK donor versus no-donor analysis of myeloablative HLA-identical sibling stem cell transplantation in first remission acute myeloid leukemia in young and middle-aged adults: benefits for whom?

The Dutch-Belgian Hemato-Oncology Cooperative Group and the Swiss Group for Clinical Cancer Research (HOVON-SAKK) collaborative study group evaluated outcome of patients (pts) with acute myeloid leukemia (AML) in first remission (CR1) entered in 3 consecutive studies according to a donor versus no-donor comparison. Between 1987 and 2004, 2287 pts were entered in these studies of whom 1032 pts (45%) without FAB M3 or t(15;17) were in CR1 after 2 cycles of chemotherapy, received consolidation treatment, and were younger than 55 years of age and therefore eligible for allogeneic hematopoietic stem cell transplantation (allo-SCT). An HLA-identical sibling donor was available for 326 pts (32%), whereas 599 pts (58%) lacked such a donor, and information was not available in 107 pts. Compliance with allo-SCT was 82% (268 of 326). Cumulative incidences of relapse were, respectively, 32% versus 59% for pts with versus those without a donor (P < .001). Despite more treatment-related mortality (TRM) in the donor group (21% versus 4%, P < .001), disease-free survival (DFS) appeared significantly better in the donor group (48% +/- 3% versus 37% +/- 2% in the no-donor group, P < .001). Following risk-group analysis, DFS was significantly better for pts with a donor and an intermediate- (P = .01) or poor-risk profile (P = .003) and also better in pts younger than 40 years of age (P < .001). We evaluated our results and those of the previous MRC, BGMT, and EORTC studies in a meta-analysis, which revealed a significant benefit of 12% in overall survival (OS) by donor availability for all patients with AML in CR1 without a favorable cytogenetic profile.

Prognostic Factors in Elderly Patients with AML and the Implications for Treatment

The outcome of older patients with acute myeloid leukemia (AML) has not improved in the last three decades. These patients are more likely to have comorbid illness, poor performance status, and impaired organ function. These clinical features limit their ability to tolerate intensive cytotoxic chemotherapy and result in greater early mortality. The AML seen in elderly patients is also more likely to have evolved from a prior hematologic disorder, and the leukemic blasts are more likely to have poor-risk structural and numeric cytogenetic abnormalities and expression of multidrug resistance protein (MDR1). These blast features have been associated with greater resistance to therapy. Attempts to improve outcome have generally been unsuccessful. Priming of leukemic blasts with granulocyte colony-stimulating factors during cytarabine therapy, granulocyte colony-stimulating factor support to speed neutrophil recovery following induction therapy, inhibition of the MDR1 p-glycoprotein efflux pump, the use of alternative anthracyclines, and the addition of high-dose cytarabine have all been investigated in the last three decades. Further manipulation of standard cytotoxic chemotherapy alone is unlikely to improve the outcome for the majority of patients with AML. Incorporation of molecularly targeted therapies may prove to be less toxic and/or more efficacious. However, patient selection for clinical trials will continue to confound the interpretation of treatment outcomes on clinical trials of older patients with AML.

Acute myeloid leukemia: epidemiology and etiology

Acute myeloid leukemias (AMLs) are infrequent, yet highly malignant neoplasms responsible for a large number of cancer-related deaths. The incidence has been near stable over the last years. It continuously shows 2 peaks in occurrence in early childhood and later adulthood. With an incidence of 3.7 per 100,000 persons and an age-dependent mortality of 2.7 to nearly 18 per 100,000 persons, there is a rising awareness in the Western world of AML's special attributes resulting from an ever-aging population. To objectively describe epidemiologic data on this patient population, recent publications were evaluated to make transparent the current trends and facts. A review of the literature is presented, reflecting highlights of current research with respect to AML etiology. To estimate outcome and discuss informed treatment decisions with AML patients of different age groups and different biologic risk categories, it is mandatory to consider that the outcome results reported in clinical trials were until now heavily biased toward younger patients, whereas the overall dismal prognosis documented in population-based studies most likely reflects the exclusion of older patients from aggressive treatment. The etiology for most cases of AML is unclear, but a growing knowledge concerning leukemogenenic agents within chemotherapy regimens for other malignancies is already available. This includes specific associations of the most frequent balanced translocations in AML, including the "good-risk" abnormalities comprised by the core binding factor leukemias (i.e., AML with the translocation (8;21) and inversion of chromosome 16, and acute promyelocytic leukemia with the translocation (15;17)). In contrast to these genetic alterations, epigenetic lesions, e.g., promoter silencing by hypermethylation of the p15/INK4b and other genes, are increasingly recognized as important in the pathogenesis of AML.

Pilot remission induction therapy with idarubicin, plus an intensified dose of ara-C and priming with granulocyte colony-stimulating factor for acute myeloid leukemia

BACKGROUND

The sensitization of leukemic cells with hematopoietic growth factors can enhance the cytotoxicity of chemotherapy in acute myeloid leukemia (AML). Intensified remission induction (RI) therapy can also improve the treatment results for AML. Therefore, the current trial attempted to evaluate the efficacy and toxicity of granulocyte colony-stimulating factor (G-CSF) priming and a dose intensification of Ara-C in RI chemotherapy for AML.

METHODS

A total of 29 patients with newly diagnosed AML received G-CSF-priming RI chemotherapy consisting of idarubicin (12 mg/m2, days 1-3), G-CSF (150 microg/m2, days 3-8) and Ara-C (500 mg/m2, b.i.d., days 4-8), and the outcomes were compared with those of a historical group treated with a standard regimen consisting of idarubicin (12 mg/m2, days 1-3) and Ara-C (100 mg/m2, days 1-7).

RESULTS

There was no difference in sex, age, subtype and cytogenetic risk between the two groups. The complete remission rate and treatment-related mortality were 72 and 17% for the G-CSF-primed group (p = 0.89) and 71 and 10% for the historical group (p = 0.32), respectively. The time to neutrophil recovery (25 vs. 24 days, p = 0.17) and platelet recovery (24 vs. 23 days, p = 0.23) did not differ significantly between the two groups. Similarly, the duration of fever was not significantly different (5 vs. 7 days, p = 0.58). Thirteen patients (45%) experienced fever and 5 patients (17%) manifested skin rashes during the G-CSF priming. After a median follow-up of 336 days, the 1-year overall survival, disease-free survival and event-free survival rates were 72 vs. 63% (p = 0.83), 74 vs. 56% (p = 0.059) and 53 vs. 38% (p = 0.32), respectively.

CONCLUSION

The sensitization of leukemic cells with growth factors and dose intensification seem to be clinically applicable means to enhance the efficacy of RI chemotherapy only in selected patients with AML, thereby warranting further studies focusing on specific subgroups of AML patients.

Acute myeloid leukaemia

Acute myeloid leukaemia (AML) is a heterogeneous clonal disorder of haemopoietic progenitor cells and the most common malignant myeloid disorder in adults. The median age at presentation for patients with AML is 70 years. In the past few years, research in molecular biology has been instrumental in deciphering the pathogenesis of the disease. Genetic defects are thought to be the most important factors in determining the response to chemotherapy and outcome. Whereas significant progress has been made in the treatment of younger adults, the prospects for elderly patients have remained dismal, with median survival times of only a few months. This difference is related to comorbidities associated with ageing and to disease biology. Current efforts in clinical research focus on the assessment of targeted therapies. Such new approaches will probably lead to an increase in the cure rate.

Current therapeutic strategies for acute myeloid leukaemia

Improvements in survival in adult acute myeloid leukaemia (AML) have yet to be gleaned from either refinements in the understanding of the pathophysiology of the disease or from the expanding pool of targeted therapies. Outcomes have remained particularly dismal in older patients. Ongoing and planned trials will assess the effects of drugs targeting biological pathways whose clinical importance may vary as a function of the unique genotype and phenotype of each case of AML. The success of these ventures will ultimately require well-designed clinical trials in subsets of patients with risk being dependent not only on age and cytogenetics, but on additional, increasingly quantifiable biological variables. Inhibitors of fms-like tyrosine kinase-3, farnesyl transferase, apoptotic and angiogenic pathways are being studied alone and in combination with chemotherapy. Biological therapies, including monoclonal antibodies, peptide vaccines and interleukin-2, are undergoing evaluation. The role of autologous as well as allogeneic myeloablative and reduced-intensity transplantation continues to be defined. Several potentially useful new cytotoxic agents are being introduced. Critically important to advancing the field in light of such an increasing number of choices is a reassessment of traditional phase II trial designs so that more efficient evaluation of new therapies may take place, even as well-designed phase III trials continue to be performed.

Ex vivo modulation of response to prednisolone in childhood acute lymphoblastic leukaemia

We hypothesised that the intensity of mechanisms of glucocorticoid resistance in childhood acute lymphoblastic leukaemia might be decreased by concurrent ex vivo use of compounds with specific blocking or activating properties at different steps of the glucocorticoid intracellular pathway. The following modifiers were used: ciclosporin A, rifampicin, doxycycline, meta-iodobenzylguanidine, buthionine sulfoximine, ethacrinic acid, pentoxifylline, indomethacin, rotenone, forskolin, olomoucin, 5-aza-2'-deoxycytidine, 3-aminobenzamide, O(6)-benzylguanidine and nitroprusside sodium. All modulators sensitised lymphoblasts and potentiated prednisolone cytotoxicity in most cases indicating that various compounds, which can influence the antileukaemic effect of prednisolone during anticancer therapy, might modulate some mechanisms of glucocorticoid resistance.

Rate of Infectious Complications during Interferon-Based Therapy for Hepatitis C Is Not Related to Neutropenia

The relationship between infectious complications and neutropenia was evaluated in recipients of interferon-based therapy for hepatitis C followed at The Ottawa Hospital Viral Hepatitis Clinic from June 2000 to May 2005. One hundred ninety-two patients received 211 courses of therapy (5707 person-weeks of therapy). No patients received granulocyte colony-stimulating factor. Sixty-seven infectious complications occurred in 57 patients (1.17 infections per 100 person-weeks of therapy). The median time to infection was 17 weeks after the start of therapy. Age, sex, weight, race, human immunodeficiency virus status, stage and grade of biopsy, and type of interferon were not correlated with infection rate by Cox regression analysis. The rates of total, fungal, viral, and bacterial infections did not correlate with nadir neutrophil count or magnitude of decrease from baseline. Neutrophil count is not correlated with infection rate in recipients of interferon-based therapy for hepatitis C. Reduction in interferon dose and/or dosing with granulocyte colony-stimulating factor in those with neutropenia is not supported by this analysis.

Double Induction Containing Either Two Courses or One Course of High-Dose Cytarabine Plus Mitoxantrone and Postremission Therapy by Either Autologous Stem-Cell Transplantation or by Prolonged Maintenance for Acute Myeloid Leukemia

Purpose

Intensification by high-dose cytarabine in postremission or induction therapy and prolonged maintenance are established strategies to improve the outcome in patients with acute myeloid leukemia (AML). Whether additional intensification can add to this effect has not yet been determined.

Patients and Methods

A total of 1,770 patients (age 16 to 85 years) with de novo or secondary AML or high-risk myelodysplastic syndrome (MDS) were randomly assigned upfront for induction therapy containing one course with standard dose and one course with high-dose cytarabine, or two courses with high-dose cytarabine, and in the same step received postremission prolonged maintenance or busulfan/cyclophosphamide chemotherapy with autologous stem-cell transplantation.

Results

The complete remission rate in patients younger than 60 and ≥ 60 years of age was 70% and 53%, respectively. The overall survival at 3 years in the two age groups was 42% and 19%, the relapse-free survival was 40% and 19%, and the ongoing remission duration was 48% and 22%, respectively. There were no significant differences in these results between the two randomized induction arms or between the two postremission therapy arms. There was no significant difference in any prognostic subgroup according to secondary AML/MDS, cytogenetics, WBC, lactate dehydrogenase, and early blast clearance.

Conclusion

The regimen of one course with standard-dose cytarabine and one course with high-dose cytarabine for induction, and prolonged maintenance for postremission chemotherapy in patients with AML is not improved by additional escalation in cytotoxic treatment.

2006 update of recommendations for the use of white blood cell growth factors: an evidence-based clinical practice guideline

PURPOSE

To update the 2000 American Society of Clinical Oncology guideline on the use of hematopoietic colony-stimulating factors (CSF).

UPDATE METHODOLOGY

The Update Committee completed a review and analysis of pertinent data published from 1999 through September 2005. Guided by the 1996 ASCO clinical outcomes criteria, the Update Committee formulated recommendations based on improvements in survival, quality of life, toxicity reduction and cost-effectiveness.

RECOMMENDATIONS

The 2005 Update Committee agreed unanimously that reduction in febrile neutropenia (FN) is an important clinical outcome that justifies the use of CSFs, regardless of impact on other factors, when the risk of FN is approximately 20% and no other equally effective regimen that does not require CSFs is available. Primary prophylaxis is recommended for the prevention of FN in patients who are at high risk based on age, medical history, disease characteristics, and myelotoxicity of the chemotherapy regimen. CSF use allows a modest to moderate increase in dose-density and/or dose-intensity of chemotherapy regimens. Dose-dense regimens should only be used within an appropriately designed clinical trial or if supported by convincing efficacy data. Prophylactic CSF for patients with diffuse aggressive lymphoma aged 65 years and older treated with curative chemotherapy (CHOP or more aggressive regimens) should be given to reduce the incidence of FN and infections. Current recommendations for the management of patients exposed to lethal doses of total body radiotherapy, but not doses high enough to lead to certain death due to injury to other organs, includes the prompt administration of CSF or pegylated G-CSF.

Critically short telomeres in acute myeloid leukemia with loss or gain of parts of chromosomes

Telomeres, nucleoprotein complexes at chromosome ends, protect chromosomes against end-to-end fusion. Previous in vitro studies in human fibroblast models indicated that telomere dysfunction results in chromosome instability. Loss of telomere function can result either from critical shortening of telomeric DNA or from loss of distinct telomere-capping proteins. It is less clear whether telomere dysfunction has an important role in human cancer development in vivo. Acute myeloid leukemia (AML) is a good model to study mechanisms that generate chromosome instability in human cancer development because distinct groups of AML are characterized either by aberrations that theoretically could result from telomere dysfunction (terminal deletions, gains/losses of chromosome parts, nonreciprocal translocations), or aberrations that are unlikely to result from telomere dysfunction (e.g., reciprocal translocations or inversions). Here we demonstrate that AML with multiple chromosome aberrations that theoretically could result from telomere dysfunction is invariably characterized by critically short telomeres. Short telomeres in this group are not associated with low telomerase activity or decreased expression of essential telomeric capping proteins TRF2 and POT1. In contrast, telomerase activity levels are significantly higher in AML with short telomeres. Notably, short telomeres in the presence of high telomerase may relate to significantly higher expression of TRF1, a negative regulator of telomere length. Our observations suggest that, consistent with previous in vitro fibroblast models, age-related critical telomere shortening may have a role in generating chromosome instability in human AML development.

Intermittent exposure of primitive quiescent chronic myeloid leukemia cells to granulocyte-colony stimulating factor in vitro promotes their elimination by imatinib mesylate

PURPOSE

Primitive quiescent chronic myeloid leukemia (CML) cells are biologically resistant to imatinib mesylate, an inhibitor of the p210(BCR-ABL) kinase. The present study was designed to investigate whether either continuous or intermittent exposure of these cells to granulocyte-colony stimulating factor (G-CSF) in vitro can overcome this limitation to the effectiveness of imatinib mesylate therapy.

EXPERIMENTAL DESIGN

CD34(+) leukemic cells were isolated from six newly diagnosed chronic phase CML patients and cultured for 12 days in serum-free medium with or without G-CSF and/or imatinib mesylate present either continuously or intermittently (three cycles of G-CSF for 0, 1, or 4 days +/- imatinib mesylate for 0, 3, or 4 days). Every 4 days, the number of residual undivided viable cells and the total number of viable cells present were measured.

RESULTS

Intermittent but not continuous exposure to G-CSF significantly accelerated the disappearance in vitro of initially quiescent CD34(+) CML cells. This resulted in 3- and 5-fold fewer of these cells remaining after 8 and 12 days, respectively, relative to continuous imatinib mesylate alone (P < 0.04). Cultures containing imatinib mesylate and intermittently added G-CSF also showed the greatest reduction in the total number of cells present after 12 days (5-fold more than imatinib mesylate alone).

CONCLUSION

Intermittent exposure to G-CSF can enhance the effect of imatinib mesylate on CML cells by specifically targeting the primitive quiescent leukemic elements. A protocol for treating chronic-phase CML patients with imatinib mesylate that incorporates intermittent G-CSF exposure may offer a novel strategy for obtaining improved responses in vivo.

Role of cytokines in the treatment of acute leukemias: a review

Myeloid growth factors, such as granulocyte colony-stimulating factor and granulocyte-macrophage colony-stimulating factor, have been used to decrease the duration of chemotherapy-induced neutropenia and thereby reduce the incidence and severity of infections in various regimens used to treat acute myeloid leukemia and acute lymphoblastic leukemia. These growth factors have also been used to recruit dormant myeloid leukemia cells into the S phase of cell cycle in order to increase their susceptibility to the antileukemic effects of agents such as cytarabine. Multiple prospective randomized trials have examined the benefit and safety of the addition of growth factors before, during, and after chemotherapy. A reduction in the duration of neutropenia has been the most consistent finding; this has not been associated with stimulation of leukemia cells, the main concern of using this strategy. Unfortunately, few studies have reported a benefit in prolonging the duration of disease-free survival or overall survival. Other cytokines, including interleukins and thrombopoietin, have also been evaluated for their theoretical ability to recruit immune mechanisms to eradicate residual leukemia burden after chemotherapy, and to stimulate platelet production. In this review, we summarize the clinical experience with these growth factors in treating acute leukemias.

Fludarabine and cytosine are less effective than standard ADE chemotherapy in high-risk acute myeloid leukemia, and addition of G-CSF and ATRA are not beneficial: results of the MRC AML-HR randomized trial

The optimum chemotherapy schedule for reinduction of patients with high-risk acute myeloid leukemia (relapsed, resistant/refractory, or adverse genetic disease) is uncertain. The MRC AML (Medical Research Council Acute Myeloid Leukemia) Working Group designed a trial comparing fludarabine and high-dose cytosine (FLA) with standard chemotherapy comprising cytosine arabinoside, daunorubicin, and etoposide (ADE). Patients were also randomly assigned to receive filgrastim (G-CSF) from day 0 until neutrophil count was greater than 0.5 x 10(9)/L (or for a maximum of 28 days) and all-trans retinoic acid (ATRA) for 90 days. Between 1998 and 2003, 405 patients were entered: 250 were randomly assigned between FLA and ADE; 356 to G-CSF versus no G-CSF; 362 to ATRA versus no ATRA. The complete remission rate was 61% with 4-year disease-free survival of 29%. There were no significant differences in the CR rate, deaths in CR, relapse rate, or DFS between ADE and FLA, although survival at 4 years was worse with FLA (16% versus 27%, P = .05). Neither the addition of ATRA nor G-CSF demonstrated any differences in the CR rate, relapse rate, DFS, or overall survival between the groups. In conclusion these findings indicate that FLA may be inferior to standard chemotherapy in high-risk AML and that the outcome is not improved with the addition of either G-CSF or ATRA.

Granulocyte colony-stimulating factor enhances the in vitro cytotoxicity of gemtuzumab ozogamicin against acute myeloid leukemia cell lines and primary blast cells

OBJECTIVE

To evaluate the effects of granulocyte colony-stimulating factor (G-CSF) on the in vitro sensitivity of acute myeloid leukemia (AML) cell lines and primary AML blast cells to gemtuzumab ozogamicin (GO).

MATERIALS AND METHODS

AML cell lines and primary blasts from 10 patients with AML were first incubated for 72 hours in the presence of G-CSF (5 or 100 ng/mL) and then exposed to increasing concentrations of GO (1-1,000 ng/mL) for an additional 72 hours.

RESULTS

Pretreatment with G-CSF translated into significant enhancement of GO-induced cytotoxicity in the GO-sensitive HL-60 and NB-4 cells. Conversely, the response of GO-insensitive KG-1a, TF-1, and K562 cells was unaffected by in vitro priming with G-CSF. In vitro exposure to G-CSF augmented GO-induced apoptosis in 7 of 10 primary AML samples and rendered blast cells from three refractory patients sensitive to killing effect of GO. The G-CSF-induced increase of the cytocidal activity of GO was independent of effects on the cell cycle and on the expression levels of CD33 antigen. Of potential interest, G-CSF induced dose-dependent inhibition of P-glycoprotein (P-gp/ABCB1) function in the GO-sensitive HL-60 and NB-4 cells and in blasts from three patients with AML that we tested.

CONCLUSION

Collectively, our findings point to G-CSF as a potential sensitizing agent that can be exploited therapeutically to improve the clinical efficacy of GO.

Enhanced CML stem cell elimination in vitro by bryostatin priming with imatinib mesylate

OBJECTIVE

In chronic myeloid leukemia (CML), imatinib mesylate (IM; Gleevec, Glivec) induces a G0/G1 cell-cycle block in total CD34(+) cells without causing significant apoptosis. Bryostatin-1 (bryo), a protein kinase C (PKC) modulator, was investigated for its ability to increase IM-mediated apoptosis either through induction of cycling of G0/G1 Ph(+) cells or antagonism of the IM-induced cell-cycle block.

METHODS

The Ph(+) K562 cell line and primary CD34(+) CML cells were studied for cell-cycle progression (PI staining), proliferation ((3)H thymidine uptake), and survival (dye exclusion).

RESULTS

Following 48 hours exposure to IM, on average more than 80% of surviving K562 cells were in G0/G1 as compared to approximately 50% for untreated control cultures (p < 0.001). After accounting for IM-induced cell kill, the absolute number of viable G0/G1 cells was significantly increased, confirming its anti-proliferative effect. However, pretreatment for 24 hours with bryo both increased K562 total cell kill and normalized the percentage of cells recovered in G0/G1, thus reducing their absolute number. For primary CML CD34(+) cells, pretreatment with bryo prior to IM significantly enhanced cell death of both total and, critically, G0/G1 populations.

CONCLUSION

These results suggest that carefully scheduled drug combinations that include an agent to antagonize the anti-proliferative effect of IM may prove more efficacious within the Ph(+) stem cell compartment than IM monotherapy.