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Dasatinib is a potent BCR-ABL inhibitor effective in chronic myeloid leukemia and Ph+ acute lymphoblastic leukemia (ALL) resistant/intolerant to imatinib. In the GIMEMA LAL1205 protocol, patients with newly diagnosed Ph+ ALL older than 18 years (with no upper age limit) received dasatinib induction therapy for 84 days combined with steroids for the first 32 days and intrathecal chemotherapy. Postremission therapy was free. Fifty-three patients were evaluable (median age, 53.6 years). All patients achieved a complete hematologic remission (CHR), 49 (92.5%) at day 22. At this time point, 10 patients achieved a BCR-ABL reduction to < 10−3. At 20 months, the overall survival was 69.2% and disease-free survival was 51.1%. A significant difference in DFS was observed between patients who showed at day 22 a decrease in BCR-ABL levels to < 10−3 compared with patients who never reached these levels during induction. In multivariate analysis, BCR-ABL levels of < 10−3 at day 85 correlated with disease-free survival. No deaths or relapses occurred during induction. Twenty-three patients relapsed after completing induction. A T315I mutation was detected in 12 of 17 relapsed cases. Treatment was well tolerated; only 4 patients discontinued therapy during the last phase of the induction when already in CHR. In adult Ph+ ALL, induction treatment with dasatinib plus steroids is associated with a CHR in virtually all patients, irrespective of age, good compliance, no deaths, and a very rapid debulking of the neoplastic clone. This trial was registered at [www.clinicaltrials.gov][1] as #[NCT00391989][2]. [1]: http://www.clinicaltrials.gov [2]: /lookup/external-ref?link_type=CLINTRIALGOV&access_num=NCT00391989&atom=%2Fbloodjournal%2F118%2F25%2F6521.atom

For almost 10 years imatinib has been the therapeutic standard of chronic myeloid leukemia. The introduction of other tyrosine kinase inhibitors (TKIs) raised a debate on treatment optimization. The debate is still heated: some studies have protocol restrictions or limited follow-up; in other studies, some relevant data are missing. The aim of this report is to provide a comprehensive, long-term, intention-to-treat, analysis of 559 newly diagnosed, chronic-phase, patients treated frontline with imatinib. With a minimum follow-up of 66 months, 65% of patients were still on imatinib, 19% were on alternative treatment, 12% died and 4% were lost to follow-up. The prognostic value of BCR-ABL1 ratio at 3 months (⩽10% in 81% of patients) was confirmed. The prognostic value of complete cytogenetic response and major molecular response at 1 year was confirmed. The 6-year overall survival was 89%, but as 50% of deaths occurred in remission, the 6-year cumulative incidence of leukemia-related death was 5%. The long-term outcome of first-line imatinib was excellent, also because of second-line treatment with other TKIs, but all responses and outcomes were inferior in high-risk patients, suggesting that to optimize treatment results, a specific risk-adapted treatment is needed for such patients.

The timing and developmental sequence of events for BCR-ABL1+ acute lymphoblastic leukemia (ALL), usually associated with IKAROS (IKZF1) deletions, are unknown. We assessed the status of BCR-ABL1 and IKZF1 genes in 2 pairs of monozygotic twins, one pair concordant, the other discordant for Philadelphia chromosome positive (Ph+) ALL. The twin pair concordant for ALL shared identical BCR-ABL1 genomic sequence indicative of monoclonal, in utero origin. One twin had IKZF1 deletion and died after transplantation. The other twin had hyperdiploidy, no IKZF1 deletion, and is still in remission 8 years after transplantation. In the twin pair discordant for ALL, neonatal blood spots from both twins harbored the same clonotypic BCR-ABL1 sequence. Low level BCR-ABL1+ cells were present in the healthy co-twin but lacked the IKZF1 deletion present in the other twin's leukemic cells. The twin with ALL relapsed and died after transplantation. The co-twin remains healthy and leukemia free. These data show that in childhood Ph+ ALL, BCR-ABL1 gene fusion can be a prenatal and possibly initiating genetic event. In the absence of additional, secondary changes, the leukemic clone remains clinically silent. IKZF1 is a secondary and probable postnatal mutation in these cases, and as a recurrent but alternative copy number change is associated with poor prognosis.

The main reason for the unfavorable clinical outcome of BCR-ABL1-positive acute lymphoblastic leukemia (ALL) is genetic instability. However, how normal B-cell precursors acquire the genetic changes that lead to transformation has not yet been completely defined. We investigated the expression of the activation-induced cytidine deaminase (AID) and its role in clinical outcome in 61 adult BCR-ABL1-positive ALL patients. AID expression was detected in 36 patients (59%); it correlated with the BCR-ABL1 transcript levels and disappeared after treatment with tyrosine kinase inhibitors. Different AID splice variants were identified: full-length isoform; AIDDeltaE4a, with a 30-bp deletion of exon 4; AIDDeltaE4, with the exon 4 deletion; AIDins3, with the retention of intron 3; AIDDeltaE3-E4 isoform without deaminase activity. AID-FL predominantly showed cytoplasmic localization, as did the AID-DeltaE4a and AID-DeltaE3E4 variants, whereas the C-terminal-truncated AID-DeltaE4 showed a slightly increased nuclear localization pattern. AID expression correlated with a higher number of copy number alterations identified in genome-wide analysis using a single-nucleotide polymorphism array. However, the expression of AID at diagnosis was not associated with a worse prognosis. In conclusion, BCR-ABL1-positive ALL cells aberrantly express different isoforms of AID that may act as mutators outside the immunoglobulin (Ig) gene loci in promoting genetic instability.

The BCR-ABL1 fusion gene defines the subgroup of acute lymphoblastic leukemia (ALL) with the worst clinical prognosis. To identify oncogenic lesions that combine with BCR-ABL1 to cause ALL, we used Affymetrix Genome-Wide Human SNP arrays (250K NspI and SNP 6.0), fluorescence in situ hybridization, and genomic polymerase chain reaction to study 106 cases of adult BCR-ABL1–positive ALL. The most frequent somatic copy number alteration was a focal deletion on 7p12 of IKZF1, which encodes the transcription factor Ikaros and was identified in 80 (75%) of 106 patients. Different patterns of deletions occurred, but the most frequent were those characterized by a loss of exons 4 through 7 (Δ4-7) and by removal of exons 2 through 7 (Δ2-7). A variable number of nucleotides (patient specific) were inserted at the conjunction and maintained with fidelity at the time of relapse. The extent of the Δ4-7 deletion correlated with the expression of a dominant-negative isoform with cytoplasmic localization and oncogenic activity, whereas the Δ2-7 deletion resulted in a transcript lacking the translation start site. The IKZF1 deletion also was identified in the progression of chronic myeloid leukemia to lymphoid blast crisis (66%) but never in myeloid blast crisis or chronic-phase chronic myeloid leukemia or in patients with acute myeloid leukemia. Known DNA sequences and structural features were mapped along the breakpoint cluster regions, including heptamer recombination signal sequences recognized by RAG enzymes during V(D)J recombination, suggesting that IKZF1 deletions could arise from aberrant RAG-mediated recombination.

BACKGROUND AND OBJECTIVES: The hypereosinophilic syndrome (HES) may be associated with the fusion of the platelet derived growth factor receptor a (PDGFRalpha) gene with the FIP1L1 gene in chromosome 4 coding for a constitutively activated PDGFRalpha tyrosine kinase. These cases with FIP1L1-PDGFRalpha rearrangement have been reported to be very sensitive to the tyrosine kinase inhibitor imatinib mesylate. DESIGN AND METHODS: A prospective multicenter study of idiopathic or primary HES was established in 2001 (Study Protocol Registration no. NCT 0027 6929). One hundred and ninety-six patients were screened, of whom 72 where identified as having idiopathic or primary HES and 63 were treated with imatinib 100 to 400 mg daily. RESULTS: Twenty-seven male patients carried the FIP1L1-PDGFRalpha rearrangement. All 27 achieved a complete hematologic remission (CHR) and became negative for the fusion transcripts according to reverse transcriptase polymerase chain reaction (RT-PCR) analysis. With a median follow-up of 25 months (15-60 months) all 27 patients remain in CHR and RT-PCR negative, and continue treatment at a dose of 100 to 400 mg daily. In three patients imatinib treatment was discontinued for few months, the fusion transcript became rapidly detectable, and then again undetectable upon treatment reassumption. Thirty-six patients did not carry the rearrangement; of these, five (14%) achieved a CHR, which was lost in all cases after 1 to 15 months. INTERPRETATION AND CONCLUSIONS: All patients meeting the criteria for idiopathic or primary HES should be screened for the FIP1L1-PDGFRalpha rearrangement. For all patients with this rearrangement, chronic imatinib treatment at doses as low as 100 mg daily ensures complete and durable responses.

BACKGROUND: The incidence of chronic myeloid leukemia (CML) increases with age, but it is unclear how the characteristics of the disease vary with age. In children, where CML is very rare, it presents with more aggressive features, including huge splenomegaly, higher cell count and higher blast cell percentage. PATIENTS AND METHODS: To investigate if after childhood the disease maintains or loses these characteristics of aggressiveness, we analyzed 2784 adult patients, at least 18 years old, registered by GIMEMA CML WP over a 40-year period. RESULTS: Young adults (YAs: 18-29 years old) significantly differed from adults (30-59 years old) and elderly patients (at least 60 years old) particularly for the frequency of splenomegaly (71%, 63% and 55%, P < 0.001), and the greater spleen size (median value: 4.5, 3.0 and 1.0 cm, P < 0.001). According to the EUTOS score, that is age-independent, high-risk patients were more frequent among YAs, than among adult and elderly patients (18%, 9% and 6%, P < 0.001). In tyrosine kinase inhibitors-treated patients, the rates of complete cytogenetic and major molecular response were lower in YAs, and the probability of transformation was higher (16%, 5% and 7%, P = 0.011). CONCLUSIONS: The characteristics of CML or the host response to leukemia differ with age. The knowledge of these differences and of their causes may help to refine the treatment and to improve the outcome. CLINICAL TRIAL NUMBERS: NCT00510926, NCT00514488, NCT00769327, NCT00481052. © The Author 2014. Published by Oxford University Press on behalf of the European Society for Medical Oncology. All rights reserved. For permissions, please email: journals.permissions@oup.com.

Imatinib mesylate (STI571), a specific Bcr-Abl inhibitor, has shown a potent antileukemic activity in clinical studies of chronic myeloid leukemia (CML) patients. Early prediction of response to imatinib cannot be anticipated. We used a standardized quantitative reverse-transcriptase polymerase chain reaction (QRT-PCR) for BCR-ABL transcripts on 191 out of 200 late-chronic phase CML patients enrolled in a phase II clinical trial with imatinib 400 mg/day. Bone marrow samples were collected before treatment, after 12, 20 and at the end of study treatment (52 weeks) while peripheral blood samples were obtained after 2, 3, 6, 10, 14, 20 and 52 weeks of therapy. The amount of BCR-ABL transcript was expressed as the ratio of BCR-ABL to beta2-microglobulin (beta2M). We show that, following initiation of imatinib, the early BCR-ABL level trends in both bone marrow and peripheral blood samples made it possible to predict the subsequent cytogenetic outcome and response. We propose this method as the method of choice for monitoring patients on imatinib therapy. QRT-PCR studies may be able to identify degrees of molecular response that predict both complete cytogenetic response and long term stability, as well as patterns of response that provide an early indication of relapse and imatinib resistance.

Background Imatinib has so far been the first-choice treatment in chronic myeloid leukemia with excellent results. However, only a proportion of patients achieve major molecular response – hence the need to find biological predictors of outcome to select the optimal therapeutic strategy now that more potent inhibitors are available. Design and methods We investigated a panel of 20 polymorphisms in 7 genes, potentially associated with the pharmacogenetics of imatinib, in a subset of 189 newly diagnosed chronic myeloid leukemia patients enrolled in the TOPS trial. Included in this analysis were polymorphisms in the transporters hOCT1, MDR1, ABCG2, OCTN1, and OATP1A2, and in the metabolizing genes CYP3A4 and CYP3A5. Results In the overall population, the OCTN1 C allele (rs1050152), a simple combination of polymorphisms in the hOCT1 gene and in the genes involved in imatinib uptake were significantly associated with major molecular response. The combination of polymorphisms in imatinib uptake was also significantly associated with complete molecular response. Analyses restricted to Caucasians highlighted the significant association of MDR1 CC (rs60023214) genotype with complete molecular response. Conclusions We demonstrate the usefulness of a pharmacogenetic approach for stratification of chronic myeloid leukemia patients in terms of likelihood to achieve major or complete molecular response on imatinib. This represents an attractive opportunity for therapy optimization, worth testing in clinical trials.

BACKGROUND: Recently, in genome-wide analyses of DNA copy number abnormalities using single nucleotide polymorphism microarrays, genetic alterations targeting PAX5 were identified in over 30% of pediatric patients with acute lymphoblastic leukemia. So far the occurrence of PAX5 alterations and their clinical correlation have not been investigated in adults with BCR-ABL1-positive acute lymphoblastic leukemia. DESIGN AND METHODS: The aim of this study was to characterize the rearrangements on 9p involving PAX5 and their clinical significance in adults with BCR-ABL1-positive acute lymphoblastic leukemia. Eighty-nine adults with de novo BCR-ABL1-positive acute lymphoblastic leukemia were enrolled into institutional (n=15) or GIMEMA (Gruppo Italiano Malattie EMatologiche dell'Adulto) (n=74) clinical trials and, after obtaining informed consent, their genome was analyzed by single nucleotide polymorphism arrays (Affymetrix 250K NspI and SNP 6.0), genomic polymerase chain reaction analysis and re-sequencing. RESULTS: PAX5 genomic deletions were identified in 29 patients (33%) with the extent of deletions ranging from a complete loss of chromosome 9 to the loss of a subset of exons. In contrast to BCR-ABL1-negative acute lymphoblastic leukemia, no point mutations were found, suggesting that deletions are the main mechanism of inactivation of PAX5 in BCR-ABL1-positive acute lymphoblastic leukemia. The deletions were predicted to result in PAX5 haploinsufficiency or expression of PAX5 isoforms with impaired DNA-binding. Deletions of PAX5 were not significantly correlated with overall survival, disease-free survival or cumulative incidence of relapse, suggesting that PAX5 deletions are not associated with outcome. CONCLUSIONS: PAX5 deletions are frequent in adult BCR-ABL1-positive acute lymphoblastic leukemia and are not associated with a poor outcome.

Before the introduction of imatinib, interferon alpha-based regimens were the gold standard for treatment of early chronic phase chronic myeloid leukemia patients. The combination of IFN-alpha with imatinib is currently being investigated in at least two large clinical trials, the German CML Study IV and the French SPIRIT trial. We reviewed the cytogenetic and molecular responses of 76 early chronic phase chronic myeloid leukemia patients who were treated with imatinib and interferon-alpha and of 419 early chronic phase chronic myeloid leukemia patients treated with imatinib alone front-line. The complete cytogenetic response rate was higher in the IM+IFN-alpha group than in the imatinib group at six months (60% vs. 42%; P=0.003), but not at 48 months (88% vs. 88%). The durability of the complete cytogenetic response was similar in the two groups with 94% and 91% of complete cytogenetic responders in continuous complete cytogenetic response at 48 months (P=0.56). The major molecular response rate was higher in the IM+IFN-alpha group at six months (58% vs. 34%; P=0.0001) and 12 months (67% vs. 47%; P=0.001) but not later on (65% vs. 57% at 48 months; P=0.25). Overall and progression free survival were comparable in the two groups; a significant trend to a better event free survival was observed in patients treated with PegIFNalpha (91% vs. 78%; P=0.02). These data suggest that the response to the combination treatment is more rapid. It is not yet known how much a rapid reduction will influence the longer-term overall and progression free survival, and the cure rate.

To assess the effect of age on response and compliance to treatment in patients with chronic myeloid leukemia (CML) we performed a sub-analysis within a phase II trial of the GIMEMA CML Working Party (CML/002/STI571). Since the WHO cut-off age to define an older patient is 65 years, among the 284 patients considered, we identified 226 (80%) younger patients (below 65 years) and 58 (20%) older patients (above 65 years) before starting imatinib. Response rates (hematologic and cytogenetic) were lower in the older age group but the probabilities of progression-free survival and overall survival (median observation time 3 years) were the same. Moreover, among complete cytogenetic responders, no differences were found in the level of molecular response between the two age groups. As might be expected, older patients experienced more adverse events, both hematologic and non-hematologic: this worsened compliance did not, however, prevent a long-term outcome similar to that of younger patients.

Background: Deletions of IKAROS (IKZF1) frequently occur in B-cell precursor acute lymphoblastic leukemia (B-ALL) but the mechanisms by which they influence pathogenesis are unclear. To address this issue, a cohort of 144 adult B-ALL patients (106 BCR-ABL1-positive and 38 B-ALL negative for known molecular rearrangements) was screened for IKZF1 deletions by single nucleotide polymorphism (SNP) arrays; a sub-cohort of these patients (44%) was then analyzed for gene expression profiling. Principal Findings: Total or partial deletions of IKZF1 were more frequent in BCR-ABL1-positive than in BCR-ABL1-negative B-ALL cases (75% vs 58%, respectively, p = 0.04). Comparison of the gene expression signatures of patients carrying IKZF1 deletion vs those without showed a unique signature featured by down-regulation of B-cell lineage and DNA repair genes and up-regulation of genes involved in cell cycle, JAK-STAT signalling and stem cell self-renewal. Through chromatin immunoprecipitation and luciferase reporter assays we corroborated these findings both in vivo and in vitro, showing that Ikaros deleted isoforms lacked the ability to directly regulate a large group of the genes in the signature, such as IGLL1, BLK, EBF1, MSH2, BUB3, ETV6, YES1, CDKN1A (p21), CDKN2C (p18) and MCL1. Conclusions: Here we identified and validated for the first time molecular pathways specifically controlled by IKZF1, shedding light into IKZF1 role in B-ALL pathogenesis.

Although the pathogenesis of BCR-ABL1-positive acute lymphoblastic leukemia (ALL) is mainly related to the expression of the BCR-ABL1 fusion transcript, additional cooperating genetic lesions are supposed to be involved in its development and progression. Therefore, in an attempt to investigate the complex landscape of mutations, changes in expression profiles and alternative splicing (AS) events that can be observed in such disease, the leukemia transcriptome of a BCR-ABL1-positive ALL patient at diagnosis and at relapse was sequenced using a whole-transcriptome shotgun sequencing (RNA-Seq) approach. A total of 13.9 and 15.8 million sequence reads was generated from de novo and relapsed samples, respectively, and aligned to the human genome reference sequence. This led to the identification of five validated missense mutations in genes involved in metabolic processes (DPEP1, TMEM46), transport (MVP), cell cycle regulation (ABL1) and catalytic activity (CTSZ), two of which resulted in acquired relapse variants. In all, 6390 and 4671 putative AS events were also detected, as well as expression levels for 18 315 and 18 795 genes, 28% of which were differentially expressed in the two disease phases. These data demonstrate that RNA-Seq is a suitable approach for identifying a wide spectrum of genetic alterations potentially involved in ALL.

Monitoring of minimal residual disease (MRD) by quantification of BCR-ABL1 transcript levels has become a main part of the management of patients with BCR-ABL1-positive acute lymphoblastic leukemia (ALL) in treatment with tyrosine kinase inhibitors (TKIs). The failure to achieve molecular negativity shortly after starting TKI has been demonstrated to be predictive of relapse, suggesting that an accurate measurement of low BCR-ABL1 levels may have a role in preventing hematological relapse. Despite the big efforts made by many European laboratories within the European Study Group, at the time of writing a standardized procedure to quantify and express results is still missing for BCR-ABL1-positive ALL. In this study, in order to detect with high sensitivity low levels of BCR-ABL1 transcripts, we used a new technology and a new molecular approach based on microfluidic digital polymerase chain reaction (dPCR) using Taqman chemistry and we compared obtained results with those generated by the conventional method based on reverse transcriptase PCR reaction (RQ-PCR) for BCR-ABL1 and total ABL1, with TaqMan chemistry and with Applied Biosystems instrument. We demonstrated the dPCR is high-sensitive (able to detect a single copy of BCR-ABL1) and reliable (results are comparable to those obtained by BCR-ABL1 quantification with conventional technology), allowing an accurate monitoring of BCR-ABL1-positive ALL patients in complete remission.

During the last decade a tremendous technologic progress based on genome-wide profiling of genetic aberrations, structural DNA alterations, and sequence variations has allowed a better understanding of the molecular basis of pediatric and adult B/T- acute lymphoblastic leukemia (ALL), contributing to a better recognition of the biological heterogeneity of ALL and to a more precise definition of risk factors. Importantly, these advances identified novel potential targets for therapeutic intervention. This review will be focused on the cytogenetic/molecular advances in pediatric and adult ALL based on recently published articles.

Expression of c-Myb is required for normal hematopoiesis and for proliferation of myeloid leukemia blasts and a subset of T-cell leukemia, but its role in B-cell leukemogenesis is unknown. We tested the role of c-Myb in p190(BCR/ABL)-dependent B-cell leukemia in mice transplanted with p190(BCR/ABL)-transduced marrow cells with a c-Myb allele (Myb(f/d)) and in double transgenic p190(BCR/ABL)/Myb(w/d) mice. In both models, loss of a c-Myb allele caused a less aggressive B-cell leukemia. In p190(BCR/ABL)-expressing human B-cell leukemia lines, knockdown of c-Myb expression suppressed proliferation and colony formation. Compared with c-Myb(w/f) cells, expression of Bmi1, a regulator of stem cell proliferation and maintenance, was decreased in pre-B cells from Myb(w/d) p190(BCR/ABL) transgenic mice. Ectopic expression of a mutant c-Myb or Bmi1 enhanced the proliferation and colony formation of Myb(w/d) p190(BCR/ABL) B-cells; by contrast, Bmi1 downregulation inhibited colony formation of p190(BCR/ABL)-expressing murine B cells and human B-cell leukemia lines. Moreover, c-Myb interacted with a segment of the human Bmi1 promoter and enhanced its activity. In blasts from 19 Ph(1) adult acute lymphoblastic leukemia patients, levels of c-Myb and Bmi1 showed a positive correlation. Together, these findings support the existence of a c-Myb-Bmi1 transcription-regulatory pathway required for p190(BCR/ABL) leukemogenesis.

Little is known about alterations of cyclin dependent kinase inhibitors p15INK4B, p16INK4A and of MDM2 inhibitor p14ARF due to single nucleotide polymorphisms (SNPs) located within the CDKN2A/B genes and/or neighbouring loci. In order to investigate the potential involvement of such common DNA sequence variants in leukemia susceptibility, an association study was performed by genotyping 23 SNPs spanning the MTAP, CDKN2A/B and CDKN2BAS loci, as well as relative intergenic regions, in a case-control cohort made up of 149 leukemia patients, including Philadelphia positive (Ph+) acute lymphoblastic leukemia (ALL) and acute myeloid leukemia (AML) samples, and 183 healthy controls. rs564398, mapping to the CDKN2BAS locus that encodes for ANRIL antisense non-coding RNA, showed a statistically significant correlation with the ALL phenotype, with a risk pattern that was compatible with an overdominant model of disease susceptibility and a OR of 2 (95% CI, 1.20–3.33; p = 7.1 × 10−3). We hypothesized that this association reflects the capability of some ANRIL polymorphisms to contribute to its transcription changes responsible for alterations of CDKN2A/B expression profiles, thus leading to abnormal proliferative boosts and consequent increased ALL susceptibility.

We read with interest a series of manuscripts,1, 2, 3, 4, 5, 6 reporting somatic mutations of the isocitrate dehydrogenase 1 and 2 enzyme isoforms (IDH1, IDH2) in patients with de novo acute myeloid leukemia (AML), in patients with chronic and blast phase Philadelphia chromosome-negative (Ph–) myeloproliferative neoplasms (MPNs) and in patients with early and accelerated phase myelodysplastic syndromes (MDSs).We have recently screened, by massively parallel sequencing, the transcriptome of a Philadelphia chromosome-positive (Ph+) chronic myeloid leukemia (CML) patient

Chronic myeloid leukemia (CML) is caused by the BCR-ABL hybrid gene. The molecular mechanisms leading from chronic phase (CP) to blast crisis (BC) are not understood. However, both the presence and the levels of BCR-ABL seem to be important for CML progression. BCR-ABL is under the transcriptional control of BCR promoter. Here we focused on the gene expression control of BCR and BCR-ABL upon myeloid differentiation in healthy donors (HDs), CP and BC patients. As previously reported, BCR-ABL is downregulated during myeloid maturation in CP patients. A similar pattern was detected for BCR (but not for ABL) in CP-CML and in HD, thus suggesting that the two genes may be under a similar transcriptional control. In BC this mechanism is similarly impaired for both BCR-ABL and BCR. These data indicate the presence of an 'in trans' deregulated transcription of both BCR and BCR-ABL promoters, associated with CML progression.

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In 2004, we reported the short-term results of a multicentric, phase 2 study of imatinib 400 mg daily and pegylated interferon-alpha in the treatment of 76 early chronic phase Philadelphia-positive chronic myeloid leukemia patients. In this report, we update the results with an observation time of five years. After two years of treatment, all but 10 patients (13%) had discontinued pegylated interferon-alpha. The complete cytogenetic response rate at five years was 87%, and 94% of complete cytogenetic responders maintained the complete cytogenetic response after five years. All but one complete cytogenetic response also achieved a major molecular response. These data confirm the excellent response to imatinib front-line and the stability of the complete cytogenetic response. Any possible additional benefit of the combination with interferon-alpha remains uncertain, due to low patient compliance.

PAX5 encodes for a transcription factor essential for B-lymphoid cell commitment and is rearranged in 30% of B-cell precursor acute lymphoblastic leukemia pediatric patients (BCP-ALL). Since the first characterization of PAX5/ETV6, an increasing number of PAX5 fusion genes have been described in both adult and pediatric BCP-ALL patients. As reported in our recent review, PAX5 fusion partners encode a variety of proteins involved in cell structure (ELN, POM121), transcriptional regulation (ETV6, PML, FOXP1, MLLT3), phosphorylation (JAK2), and unknown functions (C20orf112,7AUTS2). Here we report the characterization of three new PAX5 partner genes in BCP-ALL: CHFR (a novel transcript isoform), SOX5 and POM121C. Moreover, we report cases displaying PAX5/AUTS2 and PAX5/MLLT3 fusions.

We report a study of an alternative treatment schedule of imatinib (IM) in chronic myeloid leukemia (CML). Seventy-six Philadelphia-positive (Ph+), BCR-ABL-positive patients aged 65 years or older who had been treated with IM for more than 2 years and who were in stable complete cytogenetic response (CCgR) and major molecular response (MMR) were enrolled in a single-arm study to test the effects of a policy of intermittent IM (INTERIM) therapy for 1 month on and 1 month off. With a minimum follow-up of 4 years, 13 patients (17%) lost CCgR and MMR and 14 (18%) lost MMR only. All these patients resumed continuous IM and all but one (lost to follow-up) regained CCgR and MMR. No patients progressed to accelerated or blastic phase or developed clonal chromosomal abnormalities in Ph+ cells or BCR-ABL mutations. In elderly Ph+ CML patients carefully selected for a stable CCgR (lasting >2 years), the policy of INTERIM treatment affected the markers of residual disease, but not the clinical outcomes (overall and progression-free survival). This trial was registered at www.clinicaltrials.gov as NCT 00858806.

PAX5, located on 9p13, belongs to the PAX gene family and encodes for a transcription factor essential for B lymphoid cell commitment. It functions both as a transcriptional activator and repressor of different target genes involved in lineages development. PAX5 has been recently reported to be target of aberrancies (including point mutation, deletions, and gene fusions), in approximately 30% of pediatric patients affected by BCP-ALL, the most frequent leukemia subset in children. Translocations are estimated to occur at an incidence of 2-3%, with a variety of partner genes, encoding for transcription factors (TEL, PML, FOXP1), kinases (JAK2), structural proteins (ELN, POM121) or molecules of unknown function (C20orf112, AUTS2). We performed a FISH-based study on an Italian cohort of BCP-ALL patients having 9p13 chromosomal rearrangement (as a hallmark of PAX5 rearrangement), and we identified novel PAX5 partner genes. Two pediatric patients were harboring a t(7;9)(q11.2;p13.2) with a PAX5/AUTS2 fusion transcript, thus confirming its recurrent alteration in pediatric B-ALL. Three novel partner genes of PAX5 were identified by FISH. SOX5 was found as a PAX5 partner in a pediatric patient harboring a dic(9;12)(p13;p13) chromosome. A further patient, showing a t(9;12)(p13;q34) translocation, revealed PAX5 as fused to a novel transcript isoform of CHFR, a gene widely expressed in a library of normal tissues. A third partner was identified in an adult B-ALL case, which showed a deletion within the short arm of chromosome 9, leading to the fusion of PAX5 to MLLT3. A fourth PAX-rearranged case, involving POM121C (different from the already described POM121) as fused to PAX5 in a t(7;9)(q11;p13) translocation, was identified by a RNAseq approach on BCP-ALL cases without known prognostic features. The breakpoint on chromosome 7q11 is similar to the one associated with PAX5/AUTS2. An accurate FISH analysis was performed on bone marrow cells of all cases to dissect the genomic breakpoints and the structure of the rearrangements. The fusion genes were cloned by 5’ and/or 3’ RACE PCR, confirmed by sequencing and verified by RT-PCR with specific primers on the source material. PAX5-translocated cases were further characterized by genome-wide Single Nucleotide Polymorphism array. Interestingly, Copy Number Variation analysis showed that a limited number of cooperative genetic lesions were present in addition to the translocation event, thus suggesting a primary role of the PAX rearrangement in leukemogenesis. We therefore hypothesize that PAX5 alterations may represent single genetic aberration events in a simple background, rather than being part of a complex scenario of cooperating genetic lesions involved in leukemogenesis. A common pathway for all PAX5 genomic lesions still need to be elucidated. Disclosures: No relevant conflicts of interest to declare.

We describe a case of acute myeloid leukemia M5 showing a balanced t(2;10)(q31;p12) translocation. This has never been described before as the sole cytogenetic abnormality in a bone marrow cell clone at onset. Using fluorescence in situ hybridization with properly designed bacterial artificial chromosome probes, we mapped the breakpoint regions on both derivative chromosomes 2 and 10:der(2) and der(10), respectively. The MPP7 gene, disrupted by the breakpoint on chromosome 10, was juxtaposed upstream of both HNRNA3 and NFE2L2 genes on chromosome 2, without the formation of any fusion gene. Using real-time quantitative polymerase chain reaction, we tested the possible disregulation of any of the breakpoint-associated genes as a consequence of the translocation, but we found no statistically significant alteration. Considering the potential role of this clonal cytogenetic abnormality in leukemogenesis, we speculate that this translocation could have an impact on additional genes mapping outside the breakpoint regions. However, the limited amount of RNA material available prevented us from testing this hypothesis in this present case.

The mammalian target of rapamycin (mTOR) serine/threonine kinase is the catalytic subunit of two multi-protein complexes, referred to as mTORC1 and mTORC2. Signaling downstream of mTORC1 has a critical role in leukemic cell biology by controlling mRNA translation of genes involved in both cell survival and proliferation. mTORC1 activity can be down-modulated by upregulating the liver kinase B1/AMP-activated protein kinase (LKB1/AMPK) pathway. Here, we have explored the therapeutic potential of the anti-diabetic drug, metformin (an LKB1/AMPK activator), against both T-cell acute lymphoblastic leukemia (T-ALL) cell lines and primary samples from T-ALL patients displaying mTORC1 activation. Metformin affected T-ALL cell viability by inducing autophagy and apoptosis. However, it was much less toxic against proliferating CD4(+) T-lymphocytes from healthy donors. Western blot analysis demonstrated dephosphorylation of mTORC1 downstream targets. Unlike rapamycin, we found a marked inhibition of mRNA translation in T-ALL cells treated with metformin. Remarkably, metformin targeted the side population of T-ALL cell lines as well as a putative leukemia-initiating cell subpopulation (CD34(+)/CD7(-)/CD4(+)) in patient samples. In conclusion, metformin displayed a remarkable anti-leukemic activity, which emphasizes future development of LKB1/AMPK activators as clinical candidates for therapy in T-ALL.

Activation-induced cytidine deaminase (AICDA) initiates somatic hypermutation and class-switch recombination of immunoglobulin (Ig) genes and induces mutations also in non-Ig genes. AICDA aberrant expression was detected in B-lineage acute lymphoblastic leukaemia (B-ALL), particularly BCR/ABL1+ B-ALL; patients expressing AICDA carried more copy number alterations than 'AICDA-negative' cases. To determine the role of AICDA, AICDA expression and gene expression profiling were studied in adult BCR/ABL1+ B-ALL. Patients displaying the full-length isoform AICDA are characterized by up-regulation of DNA repair/replication and cell cycle genes, suggesting their involvement in the genetic instability of BCR/ABL1+ B-ALL.

Deregulated expression of microRNAs is associated with neoplasia. Here, we show that mature miR-16 levels are abnormally increased in CD34+ cells of patients with polycythemia vera as a consequence of preferential expression of miR-16-2 on chromosome 3 rather than of miR-16-1 on chromosome 13. Forced expression of miRNA-16 in normal CD34+ cells stimulated erythroid cell proliferation and maturation. Conversely, exposure of polycythemia vera CD34+ cells to small interfering RNA against pre-miR-16-2 reduced erythroid colonies and largely prevented formation of erythropoietin-independent colonies; myeloid progenitors remained unaffected. Experiments with knock down of JAK2 indicated that overexpression of miR-16 was independent of JAK/STAT pathway activation. Mice injected with an miR-16 antagomir showed a blunted erythroid response to exogenous erythropoietin, which indicates a role of miR-16 in normal erythropoiesis. These data suggest that deregulation of miR-16-2 contributes to abnormal expansion of erythroid lineage in polycythemia vera. However, the mechanisms for miR-16-2 overexpression remain to be elucidated, because no genetic abnormalities at the miR-16-2 locus were discovered.

We investigated whether low-level Bcr–Abl kinase domain mutations can be detected in patients who have stable responses to first-line nilotinib–like it is known to happen in patients receiving imatinib. We screened for mutations twelve such patients by cloning and sequencing. Only one case was found to harbor mutations at low levels (including a T315I). However, major molecular response (MMR) was maintained and it even improved to complete molecular response. Our results suggest that a) Bcr–Abl mutations, even at low level, seem to be very rare in patients in MMR on first-line nilotinib; b) low-level mutations do not always predict for subsequent relapse.

Abstract 112 BCR-ABL kinase domain (KD) mutation analysis may be an useful tool for physicians and is being performed in a growing number of laboratories. Recommendations aimed to rationalize the use of mutation testing in chronic myeloid leukemia (CML) have recently (Blood 2011) been compiled by a panel of experts appointed by European LeukemiaNet (ELN) – including specific recommendations as to when mutation analysis should be performed. They came from the expert opinion of the panel members whenever published data were insufficient or contradictory. In order to provide further data to validate or refine these recommendations, we have analyzed the GIMEMA CML WP database recording the results of mutation analyses performed in CML pts (n=1301) receiving imatinib and/or 2nd generation TKIs between January 2004 and July 2011. At dagnosis, mutation analysis was recognized to be useful in the few pts who present in accelerated phase or blast crisis (BC), while it was not recommended in chronic phase (CP) pts. Interrogating our database, we could retrieve 58 mutation analyses in newly diagnosed pts in CP and 12 in newly diagnosed pts in BC. Imatinib-resistant mutations were detected in 0 and 2 pts, respectively. In pts receiving 1st-line imatinib, mutation analysis was recommended both in case of failure and in case of suboptimal response. We have analyzed 399 chronic phase (CP) CML pts receiving first-line imatinib because they were found to meet one of the criteria for failure or suboptimal response. Overall, 45/166 (27.1%) failures were found to be positive for one or more BCR-ABL KD mutations. In particular, mutations were detected in 3/16 (18.8%) pts with less than CHR at 3 months, 1/9 (11.1%) pts with no CyR at 6 months, 4/24 (16.7%) pts with less than PCyR at 12 months, 6/36 (16.7%) pts with less than CCyR at 18 months, 15/49 (30.6%) pts who lost CCyR and 16/32 (50%) pts who lost CHR. More interestingly, only 11/233 (4.7%) suboptimal responders we analyzed were positive for mutations. Among ‘cytogenetic' suboptimal responders, mutations were detected in 1/15 (6.7%) pts with no CyR at 3 months, 1/20 (5.0%) pts with less than PCyR at 6 months, 5/51 (8.2%) pts with less than CCyR at 12 months. Among ‘molecular' suboptimal responders, mutations were detected in 0/52 pts with less than MMR (but having achieved CCyR) at 18 months and in 4/95 (4.2%) pts who lost MMR (but not CCyR). Which rise in Bcr-Abl transcript level should trigger a mutation analysis was the most difficult issue to provide recommendations upon, given the lack of convincing and reproducible data in the literature. It was finally agreed to recommend mutation analysis only in case of MMR loss. In 159 of the CP pts we have analyzed, mutation analysis was specifically requested because of a transcript increase at a single RQ-PCR assessment: 29 pts had less than 1-log increase and 41 pts had a 1-log increase or more – but with no loss of MMR. None of these pts was found to have mutations. Another 36 pts had less than 1-log increase and 53 had a 1-log increase or more, leading to loss of MMR. Mutations were detected in 1 (2.8%) and 3 (5.7%) pts, respectively. In pts receiving dasatinib or nilotinib as 2nd-line agents, mutation analysis was recommended at baseline and then in case of failure according to the provisional definitions proposed by Baccarani et al (J Clin Oncol 2009). Nineteen among the pts we analyzed met these criteria; overall, mutations were detected in 11 (57.8%), including 5/7 pts with no CyR at 3 months, 6/9 pts with minimal CyR at 6 months, 1/4 pts with less than PCyR at 12 months. In addition, newly acquired mutations were detected in 93/131 (71%) pts who lost a previously achieved HR or CyR. We also tested 19 pts who met the provisional definitions for suboptimal response to dasatinib or nilotinib 2nd-line. Mutations were detected in 4/19 pts (21%), including 2/5 pts with minor CyR at 3 months, 1/7 pts with PCyR at 6 months, 1/7 pts with less than MMR at 12 months. Our data indicate that: a) pts harbouring mutations can more frequently be found among cytogenetic suboptimal responders than among molecular suboptimal responders; b) any Bcr-Abl transcript increase that is not associated with MMR loss shouldn't indeed trigger a mutation analysis; c) although definitions of response to dasatinib or nilotinib 2nd-line are still provisional and might soon be refined, not only failures but also suboptimal responses are frequently associated with mutations. Supported by AIL, AIRC, PRIN and FIRB. Disclosures: Soverini: Novartis: Consultancy; ARIAD: Consultancy; Bristol-Myers Squibb: Consultancy. Rosti:Novartis: Consultancy; Bristol Myers Squibb: Consultancy; Novartis: Research Funding; Novartis: Honoraria; Bristol Myers Squibb: Honoraria. Baccarani:Pfizer Oncology: Consultancy; Novartis: Consultancy; BMS: Consultancy; Ariad: Consultancy; Novartis: Research Funding; Pfizer Oncology: Honoraria; Novartis: Honoraria; BMS: Honoraria; Ariad: Honoraria; Novartis: Membership on an entity's Board of Directors or advisory committees; BMS: Membership on an entity's Board of Directors or advisory committees; Ariad: Membership on an entity's Board of Directors or advisory committees. Martinelli:Bristol-Myers Squibb: Consultancy; Novartis: Consultancy, Research Funding.

No abstract available.

We retrospectively analyzed the data of 337 patients with cytogenetically normal (CN) acute myeloid leukemia (AML), aged ≤ 65 years (training set). A prognostic index score (PIS) was calculated by totaling the score derived from the regression coefficients of each clinical variable, significantly associated with prognosis by multivariate analysis. The variables that were independent prognostic factors for event-free survival (EFS) and overall survival (OS) in the training set were: age ≥ 50 years, secondary AML and white blood cell count (WBC) ≥ 20 × 10(9)/L. The patients of the training set were stratified into three groups: low-, intermediate- and high-risk. The median EFS was 25, 12 and 7 months in the low-, intermediate- and high-risk groups (p < 0.0001), respectively. The median OS was not reached in the low-risk group and was 19 and 10 months in the intermediate- and high-risk groups (p < 0.0001). This PIS was validated in a series of 193 patients with CN-AML. The median EFS was 66, 16, and 3 months (p < 0.0001) and the median OS was 66, 16, and 5 months in the three risk groups, respectively (p < 0.0001). This PIS may be useful for clinical decision-making in CN-AML and may be prospectively integrated with the newest biological markers which at present are not routinely assessed and need prognostic validation.

Abstract 2596 Although intensive combination chemotherapy is effective in inducing complete remission in most patients with AML, the majority of responders subsequently relapse and ultimately die of the disease. This is particularly true of elderly (>60 years old) patients. The development of new therapies is therefore vital and, in this regard, targeting signaling pathways that are upregulated in AML represents a rapidly expanding research field. Constitutive activation of the phosphoinositide 3-kinase (PI3K) pathway is a common finding in AML and preclinical studies have highlighted a critical role for PI3K and its downstream effectors, Akt and mammalian target of rapamycin (mTOR), for leukemic cell survival. Especially mTOR complex 1 (mTORC1) represents a highly attractive target for cancer therapy, as it controls cap-dependent mRNA translation, a process frequently deregulated in tumor cells and that strongly contributes to oncogenesis. Preclinical data suggest that allosteric mTORC1 inhibition with rapamycin impairs leukemia initiating cell (LIC) function in AML. While PI3K/Akt inhibitors are just beginning to be tested in the clinic, mTORC1 inhibitors have already been investigated as antileukemic agents. Recently, a phase II clinical trial combining temsirolimus (an mTORC1 inhibitor) and clofarabine has been performed in elderly patients with relapsed or refractory AML (NCT007755903). Clofarabine is a nucleoside analogue with potent inhibitory effects on both ribonucleotide reductase and DNA polymerase. Here, we report the results of our pre-clinical evaluation of the efficacy of such a drug combination on AML cells. The combination of clofarabine and temsirolimus (CLO-TOR; drug concentration range: 6.125 nM–100 nm; ratio 1:1) was cytotoxic to a panel of AML cell lines (U937, OCI-AML3, HL60, THP1), as documented by MTT assays. The combination was highly synergistic, with combination indexes (CIs) ranging from 0.05 at the lowest drug concentration to 0.79 at the highest concentration. Treatment with CLO-TOR induced a G1 phase cell cycle arrest and apoptotic cell death of leukemic cells, as demonstrated by Annexin V/propidium iodide staining and cytofluorimetric analysis. Western blot analysis documented a dose-dependent cleavage of caspase-3, -8, -9. The combined treatment inhibited phosphorylation of Ser 473 p-Akt and of mTORC1 downstream targets (S6RP and 4E-BP1) more than either drug alone. Moreover, CLO-TOR affected the MEK/ERK pathway, as documented by dephosphorylation of p-ERK 1/2 and 90-kDa ribosomal S6 kinase. The effectiveness of the CLO-TOR treatment was not influenced by overexpression of 170-kDa P-glycoprotein (P-gp, one of the main determinants of drug-resistance), as documented by MTT assays performed on drug-sensitive and drug-resistant (i.e. overexpressing P-gp) CEM leukemic cells. The CLO-TOR combination, when employed at the same concentrations as for AML cell lines, was also cytotoxic to primary cells from AML patients (CIs: 0.11–0.25). CLO-TOR was highly effective in inducing apoptosis in an AML patient cell subpopulation (CD34+/CD38−/CD123+) which is enriched in putative LIC, as documented by quadruple staining and flow cytometric analysis of Annexin V-positive cells. The percentage of apoptotic cells in the CD34+/CD38−/CD123+ cell subset treated with CLO-TOR ranged between 90% and 97%, and was much higher than in samples treated with TOR alone (about 45%) or CLO alone (about 70%). The combined treatment also resulted in Akt, S6RP, and 4E-BP1 dephosphorylation in this cell subpopulation. In summary, the CLO-TOR combination could represent a valuable innovative treatment for AML patients, also in light of its efficacy against putative LIC. Disclosures: No relevant conflicts of interest to declare.

Abstract 1429 The development of resistance against chemotherapy remains one of the major challenges in the clinical management of leukemia. The Sonic Hedgehog (Hh) pathway is an essential regulator of multidrug resistance (MDR) in leukemia by exerting it's effect on leukaemia stem cells (LSC). PF-04449913 is a selective and potent small molecule inhibitor of the Hh pathway and leukemia self-renewal and is currently being evaluated in Phase I clinical trials. In order to evaluate the activity of PF-0444913 in overcoming the drug resistance of leukemia stem cells, we studied leukemia stem cell population (CD34+ subpopulation) collected before and after 28 days treatment in a phase I dose escalation protocol (Clinical Trial Gov. NTC00953758) enrolling selected hematological malignancies including Myelofibrosis (MF), MDS, Chronic Myeloid Leukemia (CML), Chronic Myelomonocytic leukemia (CMML) and Acute Myeloid Leukemia (AML) patients. We were able to collect and separate highly purified (98%) bone marrow hematopoietic progenitor cells (CD34+ populations) in 5 AML, 1 MF and 2 CML patients, by immunomagnetic separation, and analyze them for gene expression profile (GEP) using Affimetrix HG-U133 Plus 2.0 platform. We have observed that 1197 genes were differentially expressed between CD34+ cells collected before and after 28 days of PF-04449913 dose finding oral therapy. Among these genes, we demonstrated a down regulation of Bcl2 (fold change −1.03004; p value= 0.01), ABCA2 (fold change −1.08966; p value=0.03), Bcl2l13 (fold change −1,04259; p-value=0,027642), Bcl2l2 (fold change −1,17214; p-value=0,000768), Casp4 (fold change −1,06551; p-value=0,032428), Casp7 (fold change −1,01569; p-value=0,006688), Casp10 (fold-change −1,3076; p-value=0,050431), ABCF1 (fold change −1,04999; p-value=0,07213). On the contrary, ABCB1 (fold change 1,46592) and ABCG2 (fold change −1,16103) are respectively up and down regulated, with a not statistically significant p-value (0,35375 and 0,288194 respectively). Bcl2 (B-cell lymphoma 2), Bcl2l2 (Bcl2-like protein 2) and Bcl2l13 (Bcl2-like 13) are the founding members of the Bcl-2 family of apoptosis regulator proteins. Recent studies showed that Hh signals upregulate Bcl2 to promote cellular survival. Casp 4,7,10 (Caspases, or c ysteine-asp artic proteases) are a family of cysteine proteases that play essential roles in apoptosis, necrosis, and inflammation. ABCA2 (ATP-binding cassette sub-family A member 2), ABCF1 (ATP-binding cassette sub-family F member 1), ABCB1 (ATP-binding cassette sub-family B member 1, MDR1), ABCG2 (ATP-binding cassette sub-family G member 2) belong to the superfamily of adenosine triphosphate-binding cassette (ABC) transporters. ABC proteins transport various molecules across extra- and intracellular membranes. One mechanism of MDR is the increased expression of ABC drug transporters that mediate energy-dependent transport of drugs out of the cells against a concentration gradient, resulting in low intracellular drug concentrations. This is a common finding in LSC, and represents an important clinical problem for disease eradication. Furthermore, we evaluated Gli1, Gli2 and Smo expression by GEP, comparing data before and after 28 days of treatment with PF-04449913 and, as expected, we observed a down regulation of Gli1 (fold change −1.0775), Smo (fold change −1.07702), and an up regulation of Gli2 (fold change 1.08191). Our results suggest that PF-04449913 is able to revert MRD mechanisms of LSC by a strong down regulation of genes (Bcl-2, Bcl-2l13, Bcl-2l2, ABCA2, and ABCF1), which are critical for chemoresistance in acute and chronic leukemia patients. Therefore, the combination of PF-04449913 with Tyrosine Kinase inhibitors or conventional chemotherapy could represent a valid new therapeutic approach in these haematological malignancies. Acknowledgments. Work supported by Pfizer, European LeukemiaNet, FIRB 2008, PRIN 2009, AIRC, AIL, COFIN, University of Bologna and BolognAIL. Disclosures: Levin: Pfizer Oncology: Employment; Pfizer Oncology: Equity Ownership. Courtney:Pfizer Oncology: Employment; Pfizer Oncology: Equity Ownership. Baccarani:Novartis: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Bristol-Meyers Squibb: Honoraria, Membership on an entity's Board of Directors or advisory committees. Jamieson:Wintherix: Equity Ownership; Pfizer Oncology: Research Funding; Celgene: Research Funding; Novartis: Honoraria. Cortes:Novartis: Consultancy; Novartis: Research Funding; BMS: Consultancy, Research Funding; Ariad: Consultancy, Research Funding; Pfizer: Consultancy, Research Funding. McLachlan:Pfizer: Employment. Van Arsdale:Pfizer: Employment. Martinelli:Novartis: Consultancy, Honoraria; BMS: Consultancy, Honoraria.

Philadelphia chromosome–negative myeloproliferative neoplasms (MPNs) are clonal myeloid disorders with increased production of terminally differentiated cells. The disease course is generally chronic, but some patients show disease progression (secondary myelofibrosis or accelerated phase) and/or leukemic transformation. We investigated chromosomal aberrations in 408 MPN samples using high-resolution single-nucleotide polymorphism microarrays to identify disease-associated somatic lesions. Of 408 samples, 37.5% had a wild-type karyotype and 62.5% harbored at least 1 chromosomal aberration. We identified 25 recurrent aberrations that were found in 3 or more samples. An increased number of chromosomal lesions was significantly associated with patient age, as well as with disease progression and leukemic transformation, but no association was observed with MPN subtypes, Janus kinase 2 (JAK2) mutational status, or disease duration. Aberrations of chromosomes 1q and 9p were positively associated with disease progression to secondary myelofibrosis or accelerated phase. Changes of chromosomes 1q, 7q, 5q, 6p, 7p, 19q, 22q, and 3q were positively associated with post-MPN acute myeloid leukemia. We mapped commonly affected regions to single target genes on chromosomes 3p (forkhead box P1 [FOXP1]), 4q (tet oncogene family member 2 [TET2]), 7p (IKAROS family zinc finger 1 [IKZF1]), 7q (cut-like homeobox 1 [CUX1]), 12p (ets variant 6 [ETV6]), and 21q (runt-related transcription factor 1 [RUNX1]). Our data provide insight into the genetic complexity of MPNs and implicate new genes involved in disease progression.

Abstract 4261 Background Acute lymphoblastic leukemia (ALL) shows different outcome in children and adults, with event-free-survival (EFS) rates of 70–80% and 30–40% at 5 years, respectively. Results improved in young adults/adolescents with de novo ALL, when treated with pediatric intensive regimens rather than with adult regimens. Clinical studies are ongoing in older patients, toxicity related-therapy seeming the limiting issue. Aims We report a single centre experience on adult ALL patients treated with an intensive pediatric-inspired schedule, aiming to assess its tolerability and efficacy. Methods From 11/07 to 03/11 we treated 24 ALL patients (M/F=17/7) according to modified AIEOP-LAL2000 regimen. Treatment consisted of 7 days steroid pre-treatment, and four drugs 78-days induction (phase IA and IB) after which high risk (HR) patients were treated with three polychemotherapy blocks, while intermediate (IR) and standard risk (SR) patients went on 8-weeks consolidation and subsequent intensification. A 2 cycle consolidation therapy with nelarabine was planned for T-ALL patients. Patients with HLA-matched donor underwent allo-SCT; 2-years maintenance therapy was given to the others. Median age was 30 years (17–47). Results 22/24 patients completed the phase IA, 2 being out for grade IV toxicity (intestinal occlusion and sepsis). 17 (70.8%) obtained a complete remission (CR), 5 (21%) were refractory. One of the resistant patients achieved CR after polychemotherapy blocks, two after phase IB. Median induction duration (IA+IB) was 95 days (82–136); delays were mostly experienced after phase IB, hematologic toxicity being an important cause of delay, with median time to neutrophil count recovery of 28 days (18–34) and 39 days (16–62) for phase IA and IB respectively. A higher absolute number of adverse events during phase IA than during IB was registered (infections and gastrointestinal), without a significant prolongation of phase IA. After induction, 3 of the 19 CR patients received consolidation therapy, then 2/3 underwent allo-SCT. 6 patients received blocks: 3/6 undewent allo-SCT, 2/6 dropped out after the first and the second block for reversible grade II-III renal toxicity and one relapsed. 5 patients were treated with nelarabine, then 2/5 underwent allo-SCT. 3/19 directly underwent allo-SCT, while 1 patient completed the whole therapeutic program because no suitable donors for allo-SCT were found. One patient died after phase IB for pulmonary infection. With a median follow up of 12 months (3–50), 14/24 (58,3%) patients are alive, 8 in CR (5 underwent allo-SCT). 10 patients died, 5 for relapsed/refractory disease, 5 in CR (3 after allo-SCT). Conclusions A pediatric-inspired therapeutic regimen demonstrated a significant hematologic and a subsequent infective toxicity in adult ALL patients, this causing a lack in dose-intensity maintenance. The overall outcome seemed to be comparable to the one reached in other studies conducted on larger population but a longer follow-up and a larger population are needed to draw definitive conclusions. Acknowledgments. BolognAIL, European LeukemiaNet, AIRC, Fondazione Del Monte di Bologna e Ravenna, FIRB 2006, PRIN 2008, Ateneo RFO, Project of Integrated Program (PIO), Programma di Ricerca Regione - Università 2007–2009. Disclosures: No relevant conflicts of interest to declare.

BACKGROUND: In patients with Philadelphia-positive acute lymphoblastic leukemia, resistance to treatment with tyrosine kinase inhibitors is frequent and most often associated with the development of point mutations in the BCR-ABL kinase domain. We aimed to assess: (i) in how many patients BCR-ABL kinase domain mutations are already detectable at relatively low levels at the time of diagnosis, and (ii) whether mutation detection correlates with subsequent response to therapy. DESIGN AND METHODS: We retrospectively analyzed samples collected at diagnosis from 15 patients with Philadelphia-positive acute lymphoblastic leukemia who subsequently received tyrosine kinase inhibitor therapy (dasatinib) by cloning the BCR-ABL kinase domain in a bacterial vector and sequencing 200 independent clones per sample. RESULTS: Mutations at relatively low levels (2-4 clones out of 200) could be detected in all patients--eight who relapsed and seven who achieved persistent remission. Each patient had evidence of two to eight different mutations, the majority of which have never been reported in association with resistance to tyrosine kinase inhibitors. In two patients out of six who relapsed because of a mutation, the mutation (a T315I) was already detectable in a few clones at the time of diagnosis. On the other hand, a patient who was found to harbor an F317L mutation is in persistent remission on dasatinib. CONCLUSIONS: Our results suggest that the BCR-ABL kinase domain is prone to randomly accumulate point mutations in Philadelphia-positive acute lymphoblastic leukemia, although the presence of these mutations in a relatively small leukemic subclone does not always preclude a primary response to tyrosine kinase inhibitors.

We report gene expression and other analyses to elucidate the molecular characteristics of acute lymphoblastic leukemia (ALL) in children with Down syndrome (DS). We find that by gene expression DS-ALL is a highly heterogeneous disease not definable as a unique entity. Nevertheless, 62% (33/53) of the DS-ALL samples analyzed were characterized by high expression of the type I cytokine receptor CRLF2 caused by either immunoglobulin heavy locus (IgH@) translocations or by interstitial deletions creating chimeric transcripts P2RY8-CRLF2. In 3 of these 33 patients, a novel activating somatic mutation, F232C in CRLF2, was identified. Consistent with our previous research, mutations in R683 of JAK2 were identified in 10 specimens (19% of the patients) and, interestingly, all 10 had high CRLF2 expression. Cytokine receptor-like factor 2 (CRLF2) and mutated Janus kinase 2 (Jak2) cooperated in conferring cytokine-independent growth to BaF3 pro-B cells. Intriguingly, the gene expression signature of DS-ALL is enriched with DNA damage and BCL6 responsive genes, suggesting the possibility of B-cell lymphocytic genomic instability. Thus, DS confers increased risk for genetically highly diverse ALLs with frequent overexpression of CRLF2, associated with activating mutations in the receptor itself or in JAK2. Our data also suggest that the majority of DS children with ALL may benefit from therapy blocking the CRLF2/JAK2 pathways.

At present, there are no compounds in clinical development in the field of chronic myeloid leukemia (CML) or Philadelphia-positive (Ph+) acute lymphoblastic leukemia (ALL) that have been documented to harbor significant activity against the imatinib-resistant T315I mutation. Recent reports on the pre-clinical activity of some emerging tyrosine kinase inhibitors such as ON012380, VX-680 and PHA-739358 promise possible clinical efficacy against this specific Bcr-Abl mutant form. Here, we focus on the role of aurora kinase inhibitor VX-680 and PHA-739358 in blocking the leukemogenic pathways driven by wild-type and T315I-Bcr-Abl in CML or Ph+ ALL by reviewing recent research evidence. We also discuss the possibility of employing aurora kinase inhibitors as a promising new therapeutic approach in the treatment of CML and Ph+ ALL patients resistant to first and second generation TK inhibitors.

Imatinib mesylate has become the treatment of choice for chronic myeloid leukemia (CML): the standard dose for chronic- phase (CP) CML is 400 mg daily. Response rates are different according to Sokal score, being significantly lower in intermediate and high Sokal risk patients. Phase 1 and 2 trials have shown a dose-response effect and high-dose imatinib trials in early CP CML showed better results compared with standard dose. Our study is the first prospective trial planned to evaluate the efficacy and tolerability of high-dose imatinib in previously untreated intermediate Sokal risk CML patients. Seventy-eight patients were treated with 400 mg imatinib twice daily: complete cytogenetic response (CCgR) rates at 12 and 24 months were 88% and 91%; moreover, at 12 and 24 months 56% and 73% of CCgR patients achieved a major molecular response. The incidence of adverse events was slightly higher than reported by the most important standard-dose trials. With a median follow-up of 24 months, 3 patients progressed to advanced phase. In intermediate Sokal risk newly diagnosed CML patients, high-dose imatinib induced rapid and high response rates, apparently faster than those documented in the International Randomized Study of IFN and Imatinib for the same risk category. These clinical trials are registered at www.clinicaltrials.gov as no. NCT00510926.

Abstract 1890 Poster Board I-913 Background. Primary myelofibrosis (PMF) is a clonal myeloproliferative neoplasm (MPN) characterised by a proliferation of predominantly megakaryocytes and granulocytes in bone marrow that in fully developed disease is replaced by fibrous tissue. At molecular level, no specific defect has been identified yet. Cytogenetic abnormalities occur in up to 30% of patients, the commonest including del(13)(q12-22), der(6)t(1;6)(q21-23;p21.3), del (20q), and partial trisomy 1q. In addition, approximately 50% of patients with PMF exhibit a single, recurrent, somatic mutation in the gene encoding the cytoplasmic tyrosine kinase Janus kinase 2 (JAK2). However, such mutation is not specific, also occurring in other MPN. Recently a couple of reports dealt with single-nucleotide polymorphism (SNP) array karyotyping of MPD, including some PMF. Importantly, such studies could identify previously uncovered genetic lesions, highlighting the importance of novel high resolution technologies for the detection of formerly unknown, cryptic aberrations. In this study we performed high resolution karyotyping by SNP oligonucleotide microarray by using the most updated Affymetrix array (Genome-Wide Human SNP Array 6.0) in 20 cases of myelofibrosis (MF) in order to identify novel cryptic genomic aberrations. Methods. DNA (500 ng) was extracted from peripheral blood cells (PBMNC) of 14 primary and 6 secondary MF patients. PBMNC were depleted from lymphocytes by magnetic beads. Briefly, CD3+ cells were labeled with anti-CD3 MoAb directly coupled to magnetic microbeads (Miltenyi Biotech), washed and subsequently purified using Mini-MACS technology. After selection, cell present in the positive (CD3) and negative (PBMNC) fractions were counted and submitted to flow cytometry analysis. DNA was processed and hybridized to the Affymetrix SNP arrays 6.0 as for manufacturer instruction. A whole-genome copy number variation (CNV), genotyping, loss of heterozygosity (LOH) and uniparental disomy (UPD) analyses were performed using the Partek Suite 6.0. Ten lab-specific as well as 90 HapMap samples relative to Caucasian healthy donor were used as control reference. Genomic abnormalities were defined as recurrent when occurring in at least 25% of cases. JAK2 mutational status was assessed as reported, by alle-specific PCR. Clinical information and complete follow up were retrieved for all cases. Direct sequencing, FISH, qPCR and immunohistochemistry (IHC) has been chosen for validation. Results. In all patients we could detect several CNV. The median number of CNV was 60 (range, 34-72), including 46 amplifications (A) and 14 deletions (D). All commonest previously described abnormalities were detected. In addition, several formerly uncovered recurrent lesions were identified, mainly involving 1p, 1q, 2p, 4p, 4q, 5q, 6p, 6q, 7q, 8p, 9q 10q, 11p 11q, 12p, 14q, 15q, 16p, 16q, 17q, 18q, 19q, 20p, 22q. The median size of such CNV was 424,582 Kbp (1,379 Kbp-71,277 Mbp). We then compared JAK2+ vs. JAK2− cases. Of note, we found numerous definite aberrations (A or D) distinguishing the two groups and specifically affecting 16q23.1, 1p36.13, 3q26, 14q13.2, 5q33.2, 6q14.1, 7q33, 8p23.1, and 9p11.2. Grippingly, several genes of potential interest for PMF pathogenesis were identified within the involved loci, including RET, SCAPER, WWOX and SIRPB1. Among others, the product of such genes has been selected for validation by IHC. Similarly, many miRNA were recognized, which may deserve further investigation. Conclusions. By using a newly developed highly sensitive array we identified novel cryptic lesions in patients affected by MF. Future studies on larger series, as well as functional analyses will definitely assess their role in the pathogenesis of the disease. Of note, consistent differences were recorded in JAK2+ vs. JAK2−, supporting the hypothesis of different genetic mechanisms occurring in the two sub-groups. Acknowledgments: this work was supported by AIL Pesaro Onlus, Centro Interdipartimentale per la Ricerca sul Cancro “G. Prodi”, BolognAIL, AIRC, FIRB, RFO, Fondazione Cassa di Risparmio in Bologna, Fondazione della Banca del Monte e Ravenna, Progetto Strategico di Ateneo 2006.*GV and MRS equally contributed to this work. Disclosures: No relevant conflicts of interest to declare.

The outcome for adults and children with Philadelphia chromosome acute lymphoblastic leukemia (ALL) has been improved dramatically with the use of tyrosine kinase inhibitors but relapse is an expected event in the majority of patients. We reviewed recent findings obtained from both gene-expression profiling analysis and single nucleotide polymorphism arrays and characterized by the identification of multiple novel genetic alterations targeting key cellular pathways, including lymphoid differentiation, cell cycle, tumor suppression, apoptosis and drug responsiveness. By gene-expression profiling analysis a new subtype known as 'BCR-ABL1-like' was identified, which includes 15-20% of all precursor B-ALL cases and is associated with an unfavorable outcome. By single nucleotide polymorphism array analysis, deletions of genes such as IKAROS, PAX5 and CDKN2A-CDKN2B were frequently identified. New therapeutic approaches are now available, such as dasatinib, nilotinib and bosutinib, and we highlight those that may be applicable to the treatment of adult BCR-ABL1-positive ALL.

International audience; Despite relevant advances in survival rates of pediatric acute lymphoblastic leukemia (ALL), in adult patients the outcome is still dismal, due to a greater drug resistance, a poorer compliance with treatment, and less effective current therapies. The need for more active agents has identified a novel purine nucleoside analogue, clofarabine, which has been approved for the treatment of children with relapsed and refractory ALL, showing also promising clinical benefit in phase I-II studies in adult patients.

Dasatinib and nilotinib are tyrosine kinase inhibitors (TKIs) developed to overcome imatinib resistance in Philadelphia-positive leukemias. To assess how Bcr-Abl kinase domain mutation status evolves during sequential therapy with these TKIs and which mutations may further develop and impair their efficacy, we monitored the mutation status of 95 imatinib-resistant patients before and during treatment with dasatinib and/or nilotinib as second or third TKI. We found that 83% of cases of relapse after an initial response are associated with emergence of newly acquired mutations. However, the spectra of mutants conferring resistance to dasatinib or nilotinib are small and nonoverlapping, except for T315I. Patients already harboring mutations had higher likelihood of relapse associated with development of further mutations compared with patients who did not harbor mutations (23 of 51 vs 8 of 44, respectively, for patients who relapsed on second TKI; 13 of 20 vs 1 of 6, respectively, for patients who relapsed on third TKI).

Mutations in nucleophosmin (NPM) exon 12 and the resulting delocalization of NPM into the cytoplasm are the most specific and frequent cellular events in acute myeloid leukemia patients (AML) with normal karyotype. Cytoplasmatic NPM (NPMc+) is associated with responsiveness to chemotherapy and better prognosis. The activation of nuclear factor-kappaB (NF-kappaB) has been demonstrated to occur in a subset of AML patients and is thought to induce resistance to many chemotherapeutical agents. In this study, we demonstrate the increased in vitro sensitivity of NPMc+ cells to chemotherapeutical agents and their reduced NF-kappaB activity. Furthermore, we provide evidence of the interaction between NPMc+ and NF-kappaB in the cytoplasm, resulting in the sequestration and inactivation of NF-kappaB. The cytosolic localization and consequent inactivation of NF-kappaB justifies the reduced NF-kappaB DNA-binding activity observed in NPMc+ patients. These data, taken together, may provide a possible explanation for the increased rate of chemosensitivity observed among the NPMc+ patients.