Daniela Cilloni

Cardiovascular Events and Intensity of Treatment in Polycythemia Vera

BACKGROUND Current treatment recommendations for patients with polycythemia vera call for maintaining a hematocrit of less than 45%, but this therapeutic strategy has not been tested in a randomized clinical trial. METHODS We randomly assigned 365 adults with JAK2-positive polycythemia vera who were being treated with phlebotomy, hydroxyurea, or both to receive either more intensive treatment (target hematocrit, <45%) (low-hematocrit group) or less intensive treatment (target hematocrit, 45 to 50%) (high-hematocrit group). The primary composite end point was the time until death from cardiovascular causes or major thrombotic events. The secondary end points were cardiovascular events, cardiovascular hospitalizations, incidence of cancer, progression to myelofibrosis, myelodysplasia or leukemic transformation, and hemorrhage. An intention-to-treat analysis was performed. RESULTS After a median follow-up of 31 months, the primary end point was recorded in 5 of 182 patients in the low-hematocrit group (2.7%) and 18 of 183 patients in the high-hematocrit group (9.8%) (hazard ratio in the high-hematocrit group, 3.91; 95% confidence interval [CI], 1.45 to 10.53; P=0.007). The primary end point plus superficial-vein thrombosis occurred in 4.4% of patients in the low-hematocrit group, as compared with 10.9% in the high-hematocrit group (hazard ratio, 2.69; 95% CI, 1.19 to 6.12; P=0.02). Progression to myelofibrosis, myelodysplasia or leukemic transformation, and bleeding were observed in 6, 2, and 2 patients, respectively, in the low-hematocrit group, as compared with 2, 1, and 5 patients, respectively, in the high-hematocrit group. There was no significant between-group difference in the rate of adverse events. CONCLUSIONS In patients with polycythemia vera, those with a hematocrit target of less than 45% had a significantly lower rate of cardiovascular death and major thrombosis than did those with a hematocrit target of 45 to 50%. (Funded by the Italian Medicines Agency and others; ClinicalTrials.gov number, NCT01645124, and EudraCT number, 2007-006694-91.).

Quantitative assessment of WT1 expression by real time quantitative PCR may be a useful tool for monitoring minimal residual disease in acute leukemia patients.

In order to verify if quantitative assessment of the WT1 transcript amount by the real time quantitative PCR (RQ-PCR) can be used as a marker for minimal residual disease detection, the WT1 transcript amount was determined in BM and PB samples of patients with myeloid and lymphoid acute leukemia, in normal controls, in regenerating bone marrow samples and in purified CD34-positive cells from normal subjects. In 10 patients bearing a fusion gene transcript suitable for minimal residual disease quantitative assessment, we performed a simultaneous analysis of the WT1 and of the fusion-gene transcript at sequential time intervals during follow-up. Sequential WT1 analysis was also performed in five AML patients lacking additional molecular markers. The data obtained show that normal and regenerating BM samples and purified CD34-positive cells consistently express minimal amounts of WT1 transcript and that this is extremely low and frequently undetectable in normal PB. By contrast, high levels of WT1 expression are present in the BM and PB samples of all acute leukemia (AL) cases at diagnosis. The WT1 levels during follow-up were found to follow the pattern of the other molecular markers (fusion gene transcripts) used for MRD monitoring and increased WT1expression in the BM and/or PB during follow-up of AL patients was always found to be predictive of an impending hematological relapse.

Identification and molecular characterization of recurrent genomic deletions on 7p12 in the IKZF1 gene in a large cohort of BCR-ABL1-positive acute lymphoblastic leukemia patients: on behalf of Gruppo Italiano Malattie Ematologiche dell'Adulto Acute Leukemia Working Party (GIMEMA AL WP)

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 (Delta4-7) and by removal of exons 2 through 7 (Delta2-7). 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 Delta4-7 deletion correlated with the expression of a dominant-negative isoform with cytoplasmic localization and oncogenic activity, whereas the Delta2-7 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.

The efficacy of imatinib mesylate in patients with FIP1L1-PDGFRα-positive hypereosinophilic syndrome. Results of a multicenter prospective study

Background and Objectives The hypereosinophilic syndrome (HES) may be associated with the fusion of the platelet derived growth factor receptor α (PDGFRα) gene with the FIP1L1 gene in chromosome 4 coding for a constitutively activated PDGFRα tyrosine kinase. These cases with FIP1L1-PDGFRα 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-PDGFRα 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-PDGFRα rearrangement. For all patients with this rearrangement, chronic imatinib treatment at doses as low as 100 mg daily ensures complete and durable responses.

Philadelphia-positive patients who already harbor imatinib-resistant Bcr-Abl kinase domain mutations have a higher likelihood of developing additional mutations associated with resistance to second- or third-line tyrosine kinase inhibitors.

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).

Significant Correlation Between the Degree of WT1 Expression and the International Prognostic Scoring System Score in Patients With Myelodysplastic Syndromes

PURPOSE To determine whether pattern of WT1 gene expression is a useful marker for establishing prognosis and tracking disease progression in patients with myelodysplastic syndromes (MDS). PATIENTS AND METHODS We performed a quantitative assessment of the WT1 transcript amount by real-time quantitative polymerase chain reaction (RQ-PCR) in 173 samples (131 bone marrow samples and 42 peripheral-blood samples) from 131 patients with MDS (79 patients with refractory anemia [RA], 31 with RA with excess blasts [RAEB], 18 with secondary acute myeloid leukemia [s-AML] evolved from MDS, and three with deletion of 5q as the sole cytogenetic abnormality). Values obtained were correlated with the blast percentage and International Prognostic Scoring System (IPSS) score. RESULTS Sixty-five percent of BM and 78% of PB samples for RA and 100% of BM and PB samples of RAEB and s-AML expressed WT1 transcript amounts greater than the level observed in healthy volunteers. The degree of WT1 expression was highly correlated with the type of MDS, was much higher in RAEB and s-AML compared with RA, and increased during disease progression. Moreover, a significant correlation was found between WT1 expression levels, blast cell percentage, and the presence of cytogenetic abnormalities. Therefore, we found a significant correlation between the amount of WT1 transcripts and the IPSS score, which currently represents the most reliable risk index of disease progression available for MDS patients. CONCLUSION WT1 is a useful molecular marker for risk assessment in MDS patients.

Molecular Pathways: BCR-ABL

Aberrant tyrosine kinase activity plays a critical role in many hematologic disorders, including chronic myeloid leukemia characterized by the constitutive activity of BCR-ABL. ABL therefore represents a crucial target for new therapeutic strategies. Here, we summarize the molecular pathways that are abnormally activated by the oncoprotein. Such pathways may provide additional opportunities to develop new drugs to overcome the resistance to tyrosine kinase inhibitors. In particular, the phosphoinositide 3-kinase (PI3K)/AKT pathway can be effectively blocked by mTOR inhibitors, and several compounds can hit the RAS pathway and the resulting mitogen-activated protein (MAP) extracellular signal-regulated kinase (ERK)1/2 (MEK) and MAP kinase activation. Furthermore, mitotic kinases can be blocked by Aurora kinase inhibitors, and Pim kinases can be blocked by selective serine-threonine kinase inhibitors. Finally, the abnormal pathways that sustain the self-renewal of leukemic stem cells are described as possible targets to completely eradicate leukemic clones. Such pathways include the Hedgehog pathway, which can be blocked by Smoothened inhibitors, and the CXCR4/SDF1 axis, which can be targeted by specific antagonists. Clin Cancer Res; 18(4); 930–7. ©2011 AACR.

Assessment of minimal residual disease (MRD) in CBFbeta/MYH11 -positive acute myeloid leukemias by qualitative and quantitative RT-PCR amplification of fusion transcripts

The inv(16)(p13q22) chromosomal rearrangement associated with FAB M4Eo acute myeloid leukemia (AML) subtype is characterized by the presence of the CBFbeta/MYH11 fusion transcript that can be used to detect minimal residual disease (MRD). However, qualitative RT-PCR studies of MRD have so far produced conflicting results and seem of limited prognostic value. We have evaluated retrospectively MRD in a large series of CBFbeta/MYH11-positive patients employing both qualitative and quantitative (real-time PCR) approaches. 186 bone marrow samples from 36 patients were examined with a median follow-up of 27.5 months; 15 patients relapsed during follow-up. In qualitative studies, carried out by ‘nested’ RT-PCR assay, all patients in complete remission (CR) immediately after induction/consolidation therapy were found to be PCR positive. However, follow-up samples at later time points were persistently negative (except one case) in patients remaining in continuous CR (CCR) for more than 12 months. 16 patients were evaluated by quantitative real-time PCR assay: CBFbeta/MYH11 transcript copy number was normalized for expression of the housekeeping gene ABL, expressed as fusion gene copy number per 104 copies of ABL. A 2–3 log decline in leukemic transcript copy number was observed after induction/consolidation therapy. After achieving CR, the mean copy number was significantly higher in patients destined to relapse compared to patients remaining in CCR (151 vs 9, P < 0.0001 by Mann–Whitney test). Moreover, in CCR patients, the copy number dropped below the detection threshold after the treatment protocol was completed and remained undetectable in subsequent MRD analysis in accordance with results obtained by qualitative RT-PCR. On the contrary, in the seven patients who relapsed, the copy number in CR never declined below the detection threshold; thus a cut-off value discriminating these two groups of patients could be established. The findings of our study, if confirmed, might confer an important predictive value to quantitative real-time PCR determinations of MRD in patients with inv(16) leukemia.

Achieving a Major Molecular Response at the Time of a Complete Cytogenetic Response (CCgR) Predicts a Better Duration of CCgR in Imatinib-Treated Chronic Myeloid Leukemia Patients

Purpose: Most patients with chronic-phase chronic myeloid leukemia (CML) who receive imatinib achieve a complete cytogenetic remission (CCgR) and low levels of BCR-ABL transcripts. CCgR is durable in the majority of patients but relapse occurs in a subset. Experimental Design: To determine the potential of quantitative reverse transcription-PCR of BCR-ABL to predict cytogenetic relapse, we serially monitored residual disease in 97 CML patients with an imatinib-induced CCgR. Patients with late chronic phase CML after IFN-α failure were treated with imatinib (400 mg daily). Results: During the imatinib median follow-up time of 36 months (range, 12-54 months), disease monitoring occurred by cytogenetics and quantitative PCR. Twenty percent of patients experienced cytogenetic relapse at a median of 18 months after CCgR and a median of 24 months after starting imatinib. None of the possible prognostic factors studied in univariate and multivariate analyses seemed to predict for loss of cytogenetic response but the reduction of BCR-ABL transcript levels at the time of CCgR is an important prognostic factor. Conclusions: In our study, we showed not only that achieving a major molecular remission at 12 months is predictive of a durable cytogenetic remission but also that patients who achieved a major molecular remission (expressed both as the BCR-ABL/β2 microglobulin ratio % <0.0005 and as a 3-log reduction from median baseline value) already at the time of first achieving a CCgR have significantly longer cytogenetic remission durations than those without this magnitude of molecular response (P < 0.05).

Expression of spliced oncogenic Ikaros isoforms in Philadelphia-positive acute lymphoblastic leukemia patients treated with tyrosine kinase inhibitors: implications for a new mechanism of resistance

Ikaros plays an important role in the control of differentiation and proliferation of all lymphoid lineages. The expression of short isoforms lacking DNA-binding motifs alters the differentiation capacities of hematopoietic progenitors, arresting lineage commitment. We sought to determine whether molecular abnormalities involving the IKZF1 gene were associated with resistance to tyrosine kinase inhibitors (TKIs) in Ph+ acute lymphoblastic leukemia (ALL) patients. Using reverse-transcribed polymerase chain reaction, cloning, and nucleotide sequencing, only the non-DNA-binding Ik6 isoform was detected in 49% of Ph+ ALL patients. Ik6 was predominantly localized to the cytoplasm versus DNA-binding Ik1 or Ik2 isoforms, which showed nuclear localization. There was a strong correlation between nonfunctional Ikaros isoforms and BCR-ABL transcript level. Furthermore, patient-derived leukemia cells expressed oncogenic Ikaros isoforms before TKI treatment, but not during response to TKIs, and predominantly at the time of relapse. In vitro overexpression of Ik6 strongly increased DNA synthesis and inhibited apoptosis in TKI-sensitive cells. Genomic sequence and computational analyses of exon splice junction regions of IKZF1 in Ph+ ALL patients predicted several mutations that may alter alternative splicing. These results establish a previously unknown link between specific molecular defects that involve alternative splicing of the IKZF1 gene and the resistance to TKIs in Ph+ ALL patients.