The addition of arsenic trioxide to low-dose Ara-C in older patients with AML does not improve outcome

Most patients with acute myeloid leukaemia (AML) are older, with many unsuitable for conventional chemotherapy. Low-dose Ara-C (LDAC) is superior to best supportive care but is still inadequate. The combination of arsenic trioxide (ATO) and LDAC showed promise in an unrandomised study. We report a randomised trial of LDAC versus LDAC+ATO. Patients with AML according to WHO criteria or myelodysplastic syndrome with >10% blasts, considered as unfit for conventional chemotherapy, were randomised between subcutaneous Ara-C (20 mg b.d. for 10 days) and the same LDAC schedule with ATO (0.25 mg/kg) on days 1-5, 9 and 11, for at least four courses every 4 to 6 weeks. Overall 166 patients were entered; the trial was terminated on the advice of the DMC, as the projected benefit was not observed. Overall 14% of patients achieved complete remission (CR) and 7% CRi. Median survival was 5.5 months and 19 months for responders (CR: not reached; CRi: 14 months; non-responders: 4 months). There were no differences in response or survival between the arms. Grade 3/4 cardiac and liver toxicity, and supportive care requirements were greater in the ATO arm. This randomised comparison demonstrates that adding ATO to LDAC provides no benefit for older patients with AML.

The cyclin-dependent kinase inhibitor SNS-032 has single agent activity in AML cells and is highly synergistic with cytarabine

SNS-032 (BMS-387032) is a selective cyclin-dependent kinase (CDK) inhibitor. In this study, we evaluated its effects on primary acute myeloid leukemia (AML) samples (n=87). In vitro exposure to SNS-032 for 48 h resulted in a mean LD(50) of 139±203 nM; Cytarabine (Ara-C) was more than 35 times less potent in the same cohort. SNS-032-induced a dose-dependent increase in annexin V staining and caspase-3 activation. At the molecular level, SNS-032 induced a marked dephosphorylation of serine 2 and 5 of RNA polymerase (RNA Pol) II and inhibited the expression of CDK2 and CDK9 and dephosphorylated CDK7. Furthermore, the combination of SNS-032 and Ara-C showed remarkable synergy that was associated with reduced mRNA levels of the antiapoptotic genes XIAP, BCL2 and MCL1. In conclusion, SNS-032 is effective as a single agent and in combination with Ara-C in primary AML blasts. Treatment with Ara-C alone significantly induced the transcription of the antiapoptotic genes BCL2 and XIAP. In contrast, the combination of SNS-032 and Ara-C suppressed the transcription of BCL2, XIAP and MCL1. Therefore, the combination of SNS-032 and Ara-C may increase the sensitivity of AML cells to the cytotoxic effects of Ara-C by inhibiting the transcription of antiapoptotic genes.

Identification of patients with acute myeloblastic leukemia who benefit from the addition of gemtuzumab ozogamicin: results of the MRC AML15 trial

PURPOSE

Antibody-directed chemotherapy for acute myeloid leukemia (AML) may permit more treatment to be administered without escalating toxicity. Gemtuzumab ozogamicin (GO) is an immunoconjugate between CD33 and calicheamicin that is internalized when binding to the epitope. We previously established that it is feasible to combine GO with conventional chemotherapy. We now report a large randomized trial testing the addition of GO to induction and/or consolidation chemotherapy in untreated younger patients.

PATIENTS AND METHODS

In this open-label trial, 1,113 patients, predominantly younger than age 60 years, were randomly assigned to receive a single dose of GO (3 mg/m(2)) on day 1 of induction course 1 with one of the following three induction schedules: daunorubicin and cytarabine; cytarabine, daunorubicin, and etoposide; or fludarabine, cytarabine, granulocyte colony-stimulating factor, and idarubicin. In remission, 948 patients were randomly assigned to GO in course 3 in combination with amsacrine, cytarabine, and etoposide or high-dose cytarabine. The primary end points were response rate and survival.

RESULTS

The addition of GO was well tolerated with no significant increase in toxicity. There was no overall difference in response or survival in either induction of consolidation. However, a predefined analysis by cytogenetics showed highly significant interaction with induction GO (P = .001), with significant survival benefit for patients with favorable cytogenetics, no benefit for patients with poor-risk disease, and a trend for benefit in intermediate-risk patients. An internally validated prognostic index identified approximately 70% of patients with a predicted benefit of 10% in 5-year survival.

CONCLUSION

A substantial proportion of younger patients with AML have improved survival with the addition of GO to induction chemotherapy with little additional toxicity.

The topoisomerase II inhibitor voreloxin causes cell cycle arrest and apoptosis in myeloid leukemia cells and acts in synergy with cytarabine

BACKGROUND

Topoisomerase II is essential for the maintenance of DNA integrity and the survival of proliferating cells. Topoisomerase II poisons, including etoposide and doxorubicin, inhibit enzyme-mediated DNA ligation causing the accumulation of double-stranded breaks and have been front-line drugs for the treatment of leukemia for many years. Voreloxin is a first-in-class anti-cancer quinolone derivative that intercalates DNA and inhibits topoisomerase II. The efficacy and mechanisms of action of voreloxin in acute myeloid leukaemia were addressed in this study.

DESIGN AND METHODS

Primary acute myeloid leukemia blasts (n = 88) and myeloid cell lines were used in vitro to study voreloxin through viability assays to assess cell killing and synergy with other drugs. Apoptosis and cell cycling were assessed by flow cytometry. DNA relaxation assays were utilized to determine that voreloxin was active on topoisomerase II.

RESULTS

The mean lethal dose 50% (LD(50)) (± standard deviation) of voreloxin for primary acute myeloid leukemia blasts was 2.30 μM (± 1.87). Synergy experiments between voreloxin and cytarabine identified synergism in 22 of 25 primary acute myeloid leukemia samples tested, with a mean combination index of 0.79. Apoptosis was shown to increase in a dose-dependent manner. Furthermore, voreloxin was active in the p53-null K562 cell line suggesting that the action of voreloxin is not affected by p53 status. The action of voreloxin on topoisomerase II was confirmed using a DNA relaxation assay.

CONCLUSIONS

Voreloxin may provide an interesting addition to the cache of drugs available for the treatment of acute myeloid leukemia, a disease with a poor long-term survival. In addition to its potent action as a single agent in dividing cells, the synergy we demonstrated between voreloxin and cytarabine recommends further investigation of this topoisomerase II inhibitor.

Phase I/II Clinical Study of Tosedostat, an Inhibitor of Aminopeptidases, in Patients With Acute Myeloid Leukemia and Myelodysplasia

Purpose

To identify the maximum-tolerated dose (MTD) and to evaluate the antileukemic activity of tosedostat (formerly CHR-2797), an orally bioavailable aminopeptidase inhibitor.

Patients and Methods

In phase I, the MTD of once daily oral doses of tosedostat in hematologic malignancies was defined. In phase II, the therapeutic activity of the maximum-acceptable dose (MAD) of tosedostat was evaluated in elderly and/or relapsing patients with acute myeloid leukemia (AML) or myelodysplastic syndrome.

Results

In phase I, 16 patients were treated in four cohorts with tosedostat (60 mg to 180 mg) for 28 days. Three patients reported dose-limiting toxicities: two with reversible thrombocytopenia (> 75% reduction in platelet count) at 180 mg (MTD) and one with a Common Toxicity Criteria (CTC) grade 3 ALT elevation at 130 mg (MAD). In phase II, 41 patients were treated with 130 mg tosedostat. In phases I and II, the most common severe (CTC grades 3 to 5) adverse event was a reduction in the platelet count. Of the 51 AML patients in this study, seven reached complete marrow response (< 5% marrow blasts), with three achieving complete remission, and a further seven patients reaching a partial marrow response (between 5% and 15% marrow blasts). The overall response rate was therefore 27%. All responders were age > 60 years, and 79% had either relapsed or refractory AML.

Conclusion

This phase I/II study demonstrates that oral once daily dosing with 130 mg tosedostat is well tolerated and has significant antileukemic activity. The favorable risk-benefit profile suggests that further clinical trials are warranted.

Prognostic Significance of CEBPA Mutations in a Large Cohort of Younger Adult Patients With Acute Myeloid Leukemia: Impact of Double CEBPA Mutations and the Interaction With FLT3 and NPM1 Mutations

Purpose

To determine the clinical relevance of mutations in the CCAAT/enhancer binding protein α (CEBPA) gene in acute myeloid leukemia (AML) and to examine factors that might modify prognostic impact.

Patients and Methods

The entire CEBPA coding sequence was screened in 1,427 young adult patients with AML, excluding acute promyelocytic leukemia, using denaturing high-performance liquid chromatography and direct sequencing.

Results

Of 107 patients (7%) with CEBPA mutations, 48 patients (45%) had one mutation (CEBPA-single), and 59 patients (55%) had two mutations (CEBPA-double). The incidence of CEBPA-double patients was similar in intermediate cytogenetic risk patients with and without a normal karyotype (6% and 5%, respectively). CEBPA-double patients had evidence of a lower coincidence with FLT3/ITDs (P = .04) and were highly unlikely to have an NPM1 mutation (P < .0001). CEBPA-double but not CEBPA-single patients had a significantly better overall survival (OS) at 8 years (34%, 31%, and 54% for CEBPA–wild-type [WT], CEBPA-single, and CEBPA-double, respectively, P = .004). This benefit was lost in the presence of a FLT3/ITD (OS for CEBPA-WT, CEBPA-single, and CEBPA-double FLT3/ITD-negative patients: 36%, 35%, 59%, respectively, P = .002; OS for CEBPA-WT, CEBPA-single, and CEBPA-double FLT3/ITD-positive patients: 26%, 21%, 14%, respectively, P = .05). There was no evidence of any additional favorable benefit for a CEBPA-single mutation in the presence of an NPM1 mutation (OS, 45%, 44%, and 56%, P = .2, for NPM1-positive/CEBPA-WT, NPM1-positive/CEBPA-single, and NPM1-negative/CEBPA-double patients, respectively).

Conclusion

Screening for CEBPA mutations can be restricted to patients with intermediate-risk cytogenetics lacking an FLT3/ITD or NPM1 mutation. Only the presence of a CEBPA-double mutation should be used for therapy risk stratification.

Cytogenetics of Childhood Acute Myeloid Leukemia: United Kingdom Medical Research Council Treatment Trials AML 10 and 12

Purpose

Karyotype is an independent indicator of prognosis in acute myeloid leukemia (AML) that is widely applied to risk-adapted therapy. Because AML is rare in children, the true prognostic significance of individual chromosomal abnormalities in this age group remains unclear.

Patients and Methods

This cytogenetic study of 729 childhood patients classified them into 22 subgroups and evaluated their incidence and risk.

Results

Rearrangements of 11q23 were the most frequent abnormality found in approximately 16% of patients, with 50% of these in infants. The outcome for all patients with 11q23 abnormalities was intermediate; no difference was observed for those with t(9;11)(p21-22;q23). The core binding factor leukemias with the translocations t(8;21)(q22;q22) and inv(16)(p13q22) occurred at incidences of 14% and 7%, respectively, predominantly in older children, and their prognosis was favorable. An adverse outcome was observed in patients with monosomy 7, abnormalities of 5q, and t(6;9)(p23;q34). Abnormalities of 3q and complex karyotypes, in the absence of favorable-risk features, have been associated with an adverse outcome in adults, but the results were not significant in this childhood series. However, the presence of 12p abnormalities predicted a poor outcome.

Conclusion

Because the spectrum of chromosomal changes and their risk association seem to differ between children and adults with AML, biologic differences are emerging, which will contribute to the redefinition of risk stratification for different age groups in the future.

The NF-kappaB inhibitor LC-1 has single agent activity in multiple myeloma cells and synergizes with bortezomib

Multiple myeloma remains incurable with conventional therapeutics. Thus, new treatments for this condition are clearly required. In this study we evaluated the novel NF-kappaB inhibitor LC-1 in multiple myeloma cell lines and plasma cells derived from multiple myeloma patients. LC-1 was cytotoxic to multiple myeloma cell lines H929, U266, and JJN3, and induced apoptosis in a dose-dependent manner with an overall LD(50) of 3.6 micromol/L (+/-1.8) after 48 hours in culture. Primary multiple myeloma cells, identified by CD38 and CD138 positivity, had a mean LD(50) for LC-1 of 4.9 micromol/L (+/-1.6); normal bone marrow cells were significantly less sensitive to the cytotoxic effects of LC-1 (P = 0.0002). Treatment of multiple myeloma cell lines with LC-1 resulted in decreased nuclear localization of the NF-kappaB subunit Rel A and the inhibition of NF-kappaB target genes. In addition, LC-1 showed synergy with melphalan, bortezomib, and doxorubicin (combination indices of 0.72, 0.61, and 0.78, respectively), and was more effective when cells were cultured on fibronectin. These data show that LC-1 has activity in multiple myeloma cell lines and primary multiple myeloma cells, and its ability to inhibit NF-kappaB seems important for its cytotoxic effects. Furthermore, LC-1-induced transcriptional suppression of survivin and MCL1 provides a potential explanation for its synergy with conventional agents.

European development of clofarabine as treatment for older patients with acute myeloid leukemia considered unsuitable for intensive chemotherapy

PURPOSE

Treatment options for older patients with acute myeloid leukemia (AML) who are not considered suitable for intensive chemotherapy are limited. We assessed the second-generation purine nucleoside analog, clofarabine, in two similar phase II studies in this group of patients.

PATIENTS AND METHODS

Two consecutive studies, UWCM-001 and BIOV-121, recruited untreated older patients with AML to receive up to four or six 5-day courses of clofarabine. Patients in UWCM-001 were either older than 70 years or 60 to 69 years of age with poor performance status (WHO > 2) or with cardiac comorbidity. Patients in BIOV-121 were >or= 65 years of age and deemed unsuitable for intensive chemotherapy.

RESULTS

A total of 106 patients were treated in the two monotherapy studies. Median age was 71 years (range, 60 to 84 years), 30% had adverse-risk cytogenetics, and 36% had a WHO performance score >or= 2. Forty-eight percent had a complete response (32% complete remission, 16% complete remission with incomplete peripheral blood count recovery), and 18% died within 30 days. Interestingly, response and overall survival were not inferior in the adverse cytogenetic risk group. The safety profile of clofarabine in these elderly patients with AML who were unsuitable for intensive chemotherapy was manageable and typical of a cytotoxic agent in patients with acute leukemia. Patients had similar prognostic characteristics to matched patients treated with low-dose cytarabine in the United Kingdom AML14 trial, but had significantly superior response and overall survival.

CONCLUSION

Clofarabine is active and generally well tolerated in this patient group. It is worthy of further evaluation in comparative trials and might be of particular use in patients with adverse cytogenetics.

Attempts to Optimize Induction and Consolidation Treatment in Acute Myeloid Leukemia: Results of the MRC AML12 Trial

Purpose

To optimize treatment for younger patients with acute myeloid leukemia and high-risk myelodysplastic syndrome by comparing induction options and the number of consolidation courses and whether consolidation should include transplantation.

Patients and Methods

We randomly assigned 1,658 patients younger than age 60 years to receive mitoxantrone/cytarabine/etoposide versus cytarabine/daunorubicin/etoposide and subsequently 1,193 patients to daunorubicin/cytarabine/thioguanine (DAT) where the cytarabine dose was standard (S-DAT) versus double the standard dose (H-DAT). Patients in this randomization were randomly assigned to all-trans-retinoic acid or not. In consolidation, 992 patients were randomly assigned between a total of four courses versus five courses, and 324 patients who were not good risk were randomly assigned to transplantation or chemotherapy as the final course.

Results

Complete remission (CR) was achieved in 74% of patients and CR without recovery was achieved in an additional 11%; overall survival (OS) at 8 years was 38%. No differences in CR, relapse-free survival, relapse, or OS were seen between any of the induction randomizations except for a reduction in relapse risk (RR) on the mitoxantrone arm, which was offset by increased myelosuppression and deaths in CR. The addition of a fifth course did not improve OS and may be detrimental in older patients. Although transplantation reduced RR, it did not improve OS for the intermediate-risk group but was probably of benefit in high-risk patients.

Conclusion

Several chemotherapy schedules achieved similar remission rates and OS. Four courses of chemotherapy are adequate, but the addition of transplantation as a final course does not improve OS. New agents are required to enhance conventional chemotherapy.

OGG1 is a novel prognostic indicator in acute myeloid leukaemia

OGG1 (8-oxoguanine DNA glycosylase) constitutes a key component of the DNA base excision repair pathway, catalysing the removal of 8-oxoguanine nucleotides from DNA, thereby suppressing mutagenesis and cell death. We found that OGG1 expression was significantly downregulated by the RUNX1-ETO fusion protein product of the t(8;21) chromosome translocation in normal haematopoietic progenitor cells and in patients with acute myeloid leukaemia (AML). Further examination of OGG1 expression in 174 AML trial patients using Affymetrix microarrays showed that the prevalence rate of OGG1 expression was 33% and correlated strongly with adverse cytogenetics. OGG1-expressing patients had a worse relapse-free survival and overall survival and an increased risk of relapse at 5-years of follow-up. There remained a trend towards increased relapse rate among OGG1-expressing patients, even after adjusting for other known risk factors in comprehensive stratified analyses. We also determined a trend for OGG1 expression to have a more adverse impact on disease outcome in the context of the FLT3-ITD mutation. This study highlights OGG1 as a valuable prognostic marker that could be used to sub-stratify AML patients to predict those likely to fail conventional chemotherapies but those likely to benefit from novel therapeutic approaches that modulate DNA repair activity.

Prospective Minimal Residual Disease Monitoring to Predict Relapse of Acute Promyelocytic Leukemia and to Direct Pre-Emptive Arsenic Trioxide Therapy

Purpose

Molecular diagnostics and early assessment of treatment response that use methodologies capable of detecting submicroscopic disease can distinguish subgroups of patients with leukemia at differing relapse risk. Such information is being incorporated into risk-stratified protocols; however, there are few data concerning prospective use of sequential minimal residual disease (MRD) monitoring to identify more precisely those patients destined to experience relapse, which would allow more tailored therapies.

Methods

Real-time quantitative polymerase chain reaction (RQ-PCR) assays to detect leukemia-specific transcripts (ie, PML-RARA, RARA-PML) were used to prospectively analyze 6,727 serial blood and marrow samples from 406 patients with newly diagnosed acute promyelocytic leukemia (APL) who were receiving all-trans-retinoic acid and anthracycline-based chemotherapy.

Results

MRD monitoring according to the recommended schedule successfully identified the majority of patients subject to relapse and provided the most powerful predictor of relapse-free survival (RFS) in multivariable analysis (hazard ratio, 17.87; 95% CI, 6.88 to 46.41; P < .0001); MRD monitoring was far superior to presenting WBC (hazard ratio, 1.02; 95% CI, 1.00 to 1.03; P = .02), which is currently widely used to guide therapy. In patients who were predicted to experience relapse on the basis of MRD monitoring, early treatment intervention with arsenic trioxide prevented progression to overt relapse in the majority, and the RFS rate at 1 year from molecular relapse was 73%. By using this strategy, 3-year cumulative incidence of clinical relapse was only 5% in the Medical Research Council AML15 trial.

Conclusion

Rigorous sequential RQ-PCR monitoring provides the strongest predictor of RFS in APL and, when coupled with pre-emptive therapy, provides a valid strategy to reduce rates of clinical relapse. This provides a model for development of a more individualized approach to management of other molecularly defined subtypes of acute leukemia.

Randomized placebo-controlled trial of granulocyte colony stimulating factor (G-CSF) as supportive care after induction chemotherapy in adult patients with acute myeloid leukaemia: a study of the United Kingdom Medical Research Council Adult Leukaemia Working Party

The role of granulocyte colony stimulating factor (G-CSF) as supportive therapy following intensive induction chemotherapy for acute myeloid leukaemia (AML) in adults was investigated in a randomized trial. G-CSF (Lenograstim, 263 microg/d) or placebo was administered from day 8 after the end of chemotherapy until neutrophil recovery to 0.5 x 10(9)/l (or for up to 10 d). Eight hundred and three patients were entered. Neutrophil recovery was quicker with G-CSF (P < 0.0001), but this did not lead to differences in the number, severity or duration of infections. There were no substantial supportive care savings, although G-CSF patients spent 2 d less in hospital (P = 0.01). Complete remission (CR) rates were similar between arms (73% G-CSF, 75% placebo, P = 0.5), as were reasons for failure (induction death: P = 0.7; resistant disease: P = 0.5) and, for remitters, 5-year disease-free survival (34% vs. 38%, P = 0.3). Overall survival at 5 years was 29% with G-CSF vs. 36% with placebo (P = 0.10). Both CR rate (P = 0.006) and overall survival (P = 0.006) were worse with G-CSF in patients aged <40 years, but this may be a chance effect. There is some evidence from this trial of an adverse effect of G-CSF but these data need to be viewed in the context of the evidence from the other trials.

Prognostic factor analysis of the survival of elderly patients with AML in the MRC AML11 and LRF AML14 trials

This analysis, of 2483 patients with acute myeloid leukaemia (AML) aged 60+ years entered into two UK trials, was performed to determine the baseline parameters related to survival and to develop a risk index. The Medical Research Council (MRC) AML11 trial (n = 1071) was used to develop the index; this was validated using data from the Leukaemia Research fund (LRF) AML14 trial on 1137 intensively (AML14I) and 275 non-intensively (AML14NI) treated patients. In AML11, cytogenetic group, age, white blood count, performance status and type of AML (de novo, secondary) were all highly significantly related to prognosis in multivariate analysis. The regression coefficients were used to define good, standard and poor risk groups, with 1-year survival of 53%, 43% and 16% respectively (P < 0.0001). The risk index showed very good discrimination in both AML14I and AML14NI (both P < 0.0001), thereby providing validation, although survival in all groups was very poor in AML14NI. The risk factors for survival in older AML patients were similar to those in younger ones and discrimination of patient groups with relatively good to very poor prognosis was possible. These risk groups apply to both intensively and non-intensively treated patients. Randomized trials of intensive versus non-intensive therapy are needed to determine which types of patient should be given which type of treatment.

The novel nuclear factor-kappaB inhibitor LC-1 is equipotent in poor prognostic subsets of chronic lymphocytic leukemia and shows strong synergy with fludarabine

PURPOSE

We have recently shown that the novel nuclear factor-kappaB (NF-kappaB) inhibitor LC-1 is effective in primary chronic lymphocytic leukemia (CLL) cells. Here we elucidated the mechanism of action of LC-1, evaluated its relative cytotoxicity in prognostic subsets, and investigated its potential synergistic interaction with fludarabine.

EXPERIMENTAL DESIGN

Ninety-six fully characterized CLL cases were assessed for in vitro sensitivity to LC-1 and fludarabine. In selected cases, caspase activation, inhibition of Rel A DNA binding, and the transcription of CFLAR, BIRC5, and BCL2 were measured before and after exposure to LC-1. In addition, the efficacy of LC-1 was assessed in the presence of the survival factors CD154 and interleukin-4, and the potential synergistic interaction between LC-1 and fludarabine was evaluated.

RESULTS

Cell death was associated with caspase-3 activation mediated via activation of both caspase-8 and caspase-9. Apoptosis was preceded by a reduction of nuclear Rel A DNA binding and inhibition of CFLAR, BIRC5, and BCL2 transcription. Importantly, LC-1 overcame the cytoprotective effects by interleukin-4 and CD40 ligand and was equipotent in CLL cells derived from good and bad prognostic subsets. LC-1 exhibited strong synergy with fludarabine, and the combination produced a highly significant mean dose reduction index for fludarabine of > 1,000.

CONCLUSIONS

In view of imminent first-in-man study of LC-1 in Cardiff, these data show an important mechanistic rationale for the use of LC-1 in this disease. Furthermore, it validates the concept of targeting nuclear factor-kappaB in CLL and identifies the therapeutic potential of LC-1 in combination with fludarabine even in patients with fludarabine resistance.

Optimized Retroviral Transduction Protocol Which Preserves the Primitive Subpopulation of Human Hematopoietic Cells

Though both low-speed centrifugation and the use of fibronectin (Retronectin) fragments increase gene transduction efficiency, they still do not overcome the adverse effects of the presence of virus-containing medium (VCM). In this study, we improved transduction efficiency of primitive human hematopoietic cells by optimizing the conditions for preadsorbing culture dishes with retrovirus using a centrifugation protocol allowing subsequent infection to be carried out in the absence of VCM. We also demonstrate that preadsorbing tissue culture plates with retrovirus is dependent on the volume of VCM used for preadsorption and the length of centrifugation and the type of plasticware used but not on the temperature of centrifugation (4-33 degrees C). Direct exposure of CD34+ target cells to VCM depletes the primitive CD34+CD38neg subpopulation by more than 30%, whereas the optimized VCM-free infection protocol targets this population with equivalent efficiency but had no detrimental effects on CD34+CD38neg frequency. In summary, we demonstrate a high-frequency transduction protocol which preserves the therapeutically relevant primitive subpopulation of human hematopoietic cells.

Tipifarnib in acute myeloid leukemia

Treatment of older patients with acute myeloid leukemia (AML) represents a significant challenge. There is little evidence that outcomes are improving for patients subjected to conventional intensive treatment. In addition, there is a large population of patients who are not considered fit for a more intensive treatment approach, and treatment options are limited for these patients. As molecular mechanisms and characteristics of the disease become clearer, they represent potential targets for therapy. One such mechanism is the process of farnesylation, which is required for the activation of RAS proteins and potentially other deranged pathways. The first farnesyltransferase inhibitor (FTI) to undergo assessment in AML is tipifarnib, which has achieved a complete remission in 4% of patients who have relapsed and in 15% of untreated elderly patients. Responses were not restricted to patients with RAS protein mutations and the treatment was well tolerated in general. Several randomized comparative and combination trials have been set up that will establish the position of tipifarnib in the treatment of AML.

Progress in the treatment of acute myeloid leukemia

Significant progress in understanding the mechanisms leading to the development of acute myeloid leukemia (AML) has led to the identification of numerous molecular abnormalities that may be responsible for leukemogenesis. Over the same period, large trials have established standard regimens combining cytotoxic agents for the treatment of patients with AML. Current research is attempting to better stratify patients by identifying risk factors responsible for resistance, and to discern ways for incorporating newer agents with specific and targeted activity into our standard regimens, Herein the recent developments in the diagnosis and treatment of AML are reviewed.

Transcriptional dysregulation mediated by RUNX1-RUNX1T1 in normal human progenitor cells and in acute myeloid leukaemia

The t(8;21)(q22;q22) occurs frequently in acute myelogenous leukaemia and gives rise to the transcription factor fusion protein, RUNX1-RUNX1T1 (also known as AML1-ETO). To identify the genes dysregulated by the aberrant transcriptional activity of RUNX1-RUNX1T1, we used microarrays to determine the effect of this mutation on gene expression in human progenitor cells and during subsequent development. Gene signatures of these developmental subsets were very dissimilar indicating that effects of RUNX1-RUNX1T1 are highly context dependent. We focused on gene changes associated with the granulocytic lineage and identified a clinically relevant subset of these by comparison with 235 leukaemia patient transcriptional signatures. We confirmed the overexpression of a number of significant genes (Sox4, IL-17BR, CD200 and gamma-catenin). Further, we show that overexpression of CD200 and gamma-catenin is also associated with the inv(16) abnormality which like RUNX1-RUNX1T1 disrupts core binding factor activity. We investigated the functional significance of CD200 and gamma-catenin overexpression in normal human progenitor cells. The effect of IL17 on growth was also assessed. Individually, none of these changes were sufficient to recapitulate the effects of RUNX1-RUNX1T1 on normal development. These data provide the most comprehensive and pertinent assessment of the effect of RUNX1-RUNX1T1 on gene expression and demonstrate the highly context-dependent effects of this fusion gene.

The emerging role of targeted therapy for hematologic malignancies: update on bortezomib and tipifarnib

As therapy for hematologic malignancy evolves, new regimens and novel agents that target specific cellular processes allow a more optimistic prognosis for many patients. Bortezomib and tipifarnib are two new, targeted treatments for hematologic malignancies. Bortezomib, a proteasome inhibitor, has shown impressive efficacy in patients with relapsed multiple myeloma and as initial treatment, including before autologous stem cell transplantation. It has been studied as monotherapy and in combination with standard treatments such as dexamethasone, and with newer agents such as the immunomodulators thalidomide and lenalidomide; response is encouraging, even in patients who have relapsed after previously receiving components of a regimen as single agents. Bortezomib is generally well tolerated, including in combination with novel and conventional agents. Tipifarnib is a specific inhibitor of farnesyltransferase. Clinical trials in patients with high-risk acute leukemias and myelodysplastic syndromes have demonstrated good efficacy with tipifarnib. Continued investigation with these new, targeted treatments will further define their use as treatment options in patients with hematologic cancer.