Disease Progression In Chronic Myelogenous Leukemia Research Articles

Prognostic Implications of Derivative Chromosome 9 Deletions in Patients with Advanced-Stage Chronic Myelogenous Leukemia.

Elucidation of cryptic BCR/ABL1 gene rearrangement is exceptionally important in the clinical diagnosis and prognosis of chronic myelogenous leukemia (CML). Previous reports indicated an adverse prognostic effect of atypical BCR/ABL1 gene rearrangements with submicroscopic ABL1-BCR deletions on derivative chromosome 9 [der(9)] in CML patients. Dual color dual fusion locus-specific BCR/ABL1 fluorescent in situ hybridization (FISH) analysis together with G-banding using trypsin and Giemsa (GTG banding) was performed in 489 patients at different stages of CML to investigate the spectrum of BCR/ABL1 gene rearrangements. Among the study group analyzed, a significantly higher frequency of BCR/ABL1 gene rearrangements that is consistent with der(9) deletion were observed in the blast crisis (BC) phase at 41.67%, followed by the accelerated phase (AP) at 36.84%, the imatinib mesylate (IM)-resistant chronic phase (CP) at 23.08%, and the lowest incidence was found in de novo CP at 16.61%. 1R1G1F (1 red, 1 green, 1 fusion) with concurrent loss of ABL1-BCR fusion gene on der(9) chromosome was the major signal pattern identified in each group. The results from the current study show that this unusual BCR/ABL1 gene rearrangement is one of the steering forces toward disease progression in CML. Patients in AP/BC of CML with der(9) deletion showed poor response to IM therapy; however, patients with der(9) deletion in the early phases of CML responded well to IM treatment. Therefore, the establishment of an atypical FISH signal pattern in CML is of paramount important because it is associated with adverse clinical prognostic implications in advanced stages of the disease.

Expression of SHP-1 mRNA in Patients with Myelogenous Leukemia and Its Clinical Significance

To investigate the expression and clinical significance of SHP-1 mRNA in patients with myelogenous leukemia. The SYBR Green-based qRT-PCR was used to assess SHP-1 mRNA levels in 54 patients with chronic myelogenous leukemia (CML), 30 cases of de novo acute myelogenous leukemia (AML) and 10 persons without malignancy as controls. The relative expression levels of SHP-1 mRNA in control group (CG), chronic phase CML (CP-CML) group, advanced phase of CML (including accelerated phase CML and blastic phase CML) group and AML group were 1.15±0.62, 4.96±1.76, 2.60±0.90 and 0.45±0.20, respectively. The expression of SHP-1 mRNA in patients with CML significantly increased in comparison with that in CG(P<0.05). Meanwhile, the expression of SHP-1 mRNA in CP-CML group very significantly increased as compared with that in advanced stage of CML group(P<0.0001). The expression of SHP-1 mRNA in AML group significantly decreased as compared with that in CG group(P=0.0442). In CP-CML group, statistical analysis showed that SHP-1 mRNA expression at baseline in optimal responders (5.712±0.4476) was significantly higher than that in the suboptimal or failed responders (4.044±0.3701)(P=0.0090). Meanwhile, the SHP-1 mRNA expression in AML patients was higher than that in CR group (0.4984±0.05164) and non-CR group (0.3537±0.02388)(P=0.0017). The SHP-1 mRNA levels in CML patients are higher than that in AML patients, and probably correlats with disease progression of CML. The mRNA expression level of SHP-1 may be a molecular marker to predict early response to inatinib treatment in CP-CML and AML.

Role of amino acid metabolism in cancer progression

Changes in cellular metabolism are common properties observed in various cancers. However it remains poorly understood whether metabolic changes directly affect cancer development and progression. In chronic myelogenous leukemia (CML), disease can progress from an indolent chronic phase to an aggressive blast crisis phase in which cellular differentiation is arrested and extensive self-renewal of cancer cells occur. By studying mouse CML models, we identified an amino transferase that mediates CML disease progression.

MEF2C and CEBPA: Possible co-regulators in chronic myeloid leukemia disease progression

Chronic myelogenous leukemia (CML), a hematopoietic malignancy, characterized initially by a chronic phase (CP) progresses into blast crisis (BC) with the accumulation of secondary abnormalities. We have reported earlier that MEF2C, a target of miR-223, was significantly up regulated in CML and also showed a negative correlation with miR-223. In this study, gene expression arrays were used to identify the genes regulated by MEF2C during myelopoiesis. Statistical tools were used to understand the correlation between MEF2C and the targets in different phases of CML. Different CML cell lines and CML patient samples were treated with imatinib to study the effect of MEF2C on the target genes. We observed that MEF2C targets a set of myeloid genes including the myeloid transcription factor CEBPA. MEF2C and CEBPA expression patterns are negatively correlated in CML patient samples. We further show that the expression of MEF2C and CEBPA along with CSF3R is sufficient to molecularly classify different stages of CML. Imatinib, the drug of choice for CML, abrogates MEF2C expression and reverses CEBPA repression both in the cell line and the primary cells. We report the existence of a MEF2C and CEBPA correlation in CML disease progression.

Functionally Deregulated AML1/RUNX1 Cooperates with BCR-ABL to Induce a Blastic Phase-Like Phenotype of Chronic Myelogenous Leukemia in Mice

Patients in the chronic phase (CP) of chronic myelogenous leukemia (CML) have been treated successfully following the advent of ABL kinase inhibitors, but once they progress to the blast crisis (BC) phase the prognosis becomes dismal. Although mechanisms underlying the progression are largely unknown, recent studies revealed the presence of alterations of key molecules for hematopoiesis, such as AML1/RUNX1. Our analysis of 13 BC cases revealed that three cases had AML1 mutations and the transcript levels of wild-type (wt.) AML1 were elevated in BC compared with CP. Functional analysis of representative AML1 mutants using mouse hematopoietic cells revealed the possible contribution of some, but not all, mutants for the BC-phenotype. Specifically, K83Q and R139G, but neither R80C nor D171N mutants, conferred upon BCR-ABL-expressing cells a growth advantage over BCR-ABL-alone control cells in cytokine-free culture, and the cells thus grown killed mice upon intravenous transfer. Unexpectedly, wt.AML1 behaved similarly to K83Q and R139G mutants. In a bone marrow transplantation assay, K83Q and wt.AML1s induced the emergence of blast-like cells. The overall findings suggest the roles of altered functions of AML1 imposed by some, but not all, mutants, and the elevated expression of wt.AML1 for the disease progression of CML.

Inactivation of RIZ1 Gene by Promoter Hypermethylation is Associated with Disease Progression and Resistance to Imatinib in Indian Chronic Myelogenous Leukemia Patients, First Study from India

Background: The epigenetic impact of DNA methylation in chronic myelogenous leukemia (CML) is not completely understood. RIZ1 expression and activity are reduced in many cancers. In CML, blastic transformation is associated with loss of heterozygosity in the region where RIZ1 is located. RIZ1 is a PR domain methyltransferase that methylates histone H3 lysine 9, a modification important for transcriptional repression. In CML blast crisis cell lines RIZ1 represses insulin-like growth factor-1 expression and autocrine signaling. Together these observations suggest that RIZ1 may have a role in the chronic phase to blast crisis transition in CML. Methods: To examine whether promoter methylation is involved in the disease development and progression of CML, we investigated promoter methylation status of RIZ1 gene in 100 chronic myeloid leukemia’s (CML) patients and 50 controls by MSP method. Results: The RIZ1 methylation was studied in 100 CML patients, 9 were cases were methylation positive cases, six of nine were in blastic phase, 2 in chronic phase and one patient in accelerated phase. It was seen that RIZ1 methylation was increased significantly from early to advanced phase. The higher frequency of RIZ1 methylation was reported in haematologically resistant cases (42% vs 2%) and molecularly resistant cases (16.77% vs 1.92%) than the responders. The higher frequency of RIZ1 methylation was found in CML patients who were treated with interferon initially followed by imatinib treatment. Also RIZ1 hypermethylation was associated with faster disease progression p<0.003 than the non methylated cases. No correlation was found between RIZ1 gene methylation with age, thrombocytopenia, types of bcr/abl transcripts of CML patients. Conclusion: We conclude that epigenetic silencing of RIZ1 gene is associated with CML progression and imatinib resistance. Early detection of RIZ1 methylation could be a predictive marker for imatinib resistance and disease progression in CML.

The BCR-ABL1-Regulated hnRNP A1, hnRNP E2, and hnRNP K Are Differentially Expressed Between CD34+ and CD34+/CD38- Ph+ Cells, and After Blastic Transformation of CML.

AbstractAbstract 1222The molecular mechanism leading to disease progression of chronic myelogenous leukemia (CML) still remains to be identified although enhanced BCR/ABL expression and activity seems to play an important role in controlling genomic stability, differentiation, and self renewal of the leukemic cell clone undergoing blastic tranformation by affecting expression and function of RNA binding proteins (RBPs) like hnRNP A1, hnRNP E2, and hnRNP K (Perrotti D. et al. J. Clin Invest. 2010).We previously reported (Harb J. et al., ASH 2009) that a BCR-ABL1 dosage-dependence and hierarchical organization exists for the expression of hnRNP A1, hnRNP E2, and hnRNP K in cell line models of CML. In fact, as BCR/ABL levels increase, upregulated expression of hnRNP A1 is observed, followed by increased expression of hnRNP E2 and hnRNP K. HnRNP A1 and hnRNP K were also temporally expressed within Lineage- Sca-1+ c-kit+ (LSK), common myeloid progenitors (CMP), and granulocyte macrophage progenitors (GMP) in a mouse model (SCLtTA TRE-BCR/ABL) of chronic myeloid leukemia. Interestingly, hnRNP A1 and hnRNP K levels in BCR/ABL+ mouse progenitors correlated with disease severity as mice with higher levels of these RBPs presented a more progressed phenotype characterized by increased mixed lineage B220+/Mac-1+ progenitors in bone marrow and spleen when compared with mice that developed a CML-CP-like phenotype.Here we show that hnRNP A1, hnRNP E2, and hnRNP K expression levels, as well as BCR/ABL activity are different in HSC (CD34+/CD38-), CMP (CD34+/CD38+/CD45+/IL-3Ra-), and GMP (CD34+/CD38+/CD45+/IL-3Ra+) isolated from peripheral blood of patients in chronic phase (CML-CP) at diagnosis, untreated accelerated phase (CML-AP), and blast crisis (CML-BC). Interestingly, in CML-CP, the highest expression of hnRNP A1 was found in the CD34+/CD38- stem cell fraction and it gradually decreased in the more mature CMP and GMP progenitors (55% and 65% lower, respectively). By contrast, consistent with the role of hnRNP A1 as regulator of progenitor cell proliferation and survival, hnRNP A1 expression progressively increased in the HSC, CMP and GMP fractions isolated from patients in CML-AP and CML-BC. Unlike hnRNP A1, hnRNP E2 and hnRNP K were barely detected in the CD34+/CD38- from CML-CP patients but their expression was markedly pronounced in the HSC fraction of progressed CML patients. In agreement with our cell line data, expression of hnRNP A1 and hnRNP E2 in advanced CML (CML-AP and CML-BC) increases when CD34+/CD38- stem cells undergo maturation toward CMP. Conversely, it appears that hnRNP K expression is the last to increase in CML-BC, suggesting a hierarchical regulation of RBP expression during differentiation and lineage commitment. Expectedly, levels of hnRNP A1 in CMPs increase during disease progression (CP<AP<BC). Because of the highest expression of hnRNP A1 in the CD34+/CD38- fraction in CML-CP, and its previously described role in regulating survival and proliferation of Ph+ CD34+ cells (Iervolino et al., Mol Cell Biol 2002; Neviani et al. Cancer Cell 2005), we lentivirally transduced a hnRNP A1 shRNA into the CD34+/CD38- and CD34+/CD38+ cell fractions in CML-CP and assessed the role played by this RBP in survival of primitive and committed CML-CP progenitors. Western blot analysis demonstrated that hnRNP A1 was efficiently knockdown (≥ 80% reduction) in both compartments. Due to its ability to regulate BCR-ABL1 expression/function through the SET-PP2A axis, downregulation of hnRNP A1 led to reduced BCR/ABL activity in both stem and progenitor cells. However, cell survival and cytokine-dependent proliferation were severely compromised in committed progenitors transduced with the hnRNP A1 shRNA but not in the shRNA hnRNP A1-expressing CD34+/CD38- cells, consistent with the notion that progenitors but not stem cells are BCR-ABL1 oncogene addicted. Colony forming assays performed with empty vector- and hnRNP A1 shRNA-transduced CD34+/CD38- cells showed a 50% reduction in the number of CFCs upon hnRNP A1 downregulation. Accordingly, levels of the hnRNP A1-regulated anti-apoptotic Bcl-xL were substantially reduced in CD34+/CD38- cells.Taken together, these data further implicate RBPs hnRNP A1, hnRNP E2, and hnRNP K in CML disease progression and suggest their possible role in the control of survival of stem and primitive CML-CP progenitors. Disclosures:No relevant conflicts of interest to declare.

A Multinational Study of Health State Preference Values Associated with Chronic Myelogenous Leukemia

Objectives Chronic myelogenous leukemia (CML) is a progressive, largely fatal cancer. Emerging treatments may prolong life; however, these result in additional monetary costs. Accurate estimation of their economic impact requires reliable estimates on preferences for health states. The purpose was to estimate preference weights from the general population in four developed countries for standardized health states experienced by persons with CML. Methods Time trade-off preferences with a 10-year time horizon were elicited for CML-related health states using an interviewer-administered survey from convenience samples in Canada (n = 103), the United States (n = 74), the UK (n = 97), and Australia (n = 79). Standardized descriptions of seven CML-related health states (characterizing chronic, accelerated and blast phases, each with responding and nonresponding state, and adverse events of treatment) were derived in consultation with oncologists. Generalized linear models were used to estimate whether utilities, adjusted for age and sex, differed by country. Results The mean age of the sample (n = 357) was 45 years and 46% were male. Mean unadjusted preference values of CML-related health states ranged from 0.84 for “Chronic phase responding to treatment” to 0.21 for “Blast phase, not responding to treatment.” For each phase, preferences were lower for the nonresponding state. After adjustment for age and sex, considerable variability was observed in mean preference values between countries. Conclusion These data quantify the deteriorating impact of CML disease progression and the impact of nonresponse to treatment. The study results add to evidence from other disease areas that systematic differences exist in preference values between countries.

MicroRNAs Act as Decoy Molecules To Restore Granulocytic Maturation of Differentiation-Arrested BCR/ABL+ Myeloid Precursors.

Altered microRNA (miR) expression contributes to aberrant post-transcriptional regulation of gene expression in different type of cancers; however, their role in the pathogenesis and progression of chronic myelogenous leukemia (CML) from chronic phase (CML-CP) to blast crisis (CML-BC) is still largely unknown. Microarray analysis of miR expression reveals that a discrete number of miRs are significantly upregulated (∼ 6.7% of the total 505 miRs present on the chip; 34 miRs) or downregulated (∼2.8% of the miRs present on the chip; 14 miRs) in an imatinib-sensitive manner in CML-BCCD34+ compared to CML-CPCD34+ progenitors and in BCR/ABL-expressing hematopoietic cell lines compared to untransformed parental cells. Among them, we focused our attention on miR-223, miR-15a/16-1 and miR-328, a microRNA with no currently known function, because of their importance in myelopoiesis, potential role as tumor suppressors and sequence homology with the 5'UTR of CEBPA mRNA, respectively. In 32D-BCR/ABL and K562 cells, Northern blot and TaqMan RT-PCR analyses revealed that expression of miR-223, miR-328, miR-15a and miR-16-1 was markedly suppressed (50–75% inhibition) by p210-BCR/ABL kinase activity and that imatinib treatment (1mM; 24h) restored the expression of these miRs to levels similar to those detected in non-transformed 32Dcl3 cells. Interestingly, sequence analysis of both miR-223 and miR-328 revealed homology with the hnRNP E2-binding site contained in the CEBPA uORF/spacer mRNA, a known target of the negative regulator of myeloid differentiation hnRNP E2. Accordingly, REMSA and UV-crosslinking experiments showed that synthetic miR-223 and to a greater extent miR-328 bind efficiently to recombinant hnRNP E2 protein and compete for its binding to an oligoribonucleotide containing the CEBPA uORF/spacer region, which is required for hnRNP E2-mediated translational inhibition of CEBPA in CML-BCCD34+ progenitors. Furthermore, both miR-223 and miR-328 bind endogenous hnRNP E2 from lysates of BCR/ABL-expressing but not parental cells, and from lysates of parental 32Dcl3 myeloid precursors ectopically expressing a Flag-tagged hnRNP E2 protein, suggesting that miR-223 and miR-328 may act as decoy molecules that interfere with the translation-inhibitory activity of hnRNP E2. Indeed, ectopic expression of miR-223 restored G-CSF-driven granulocytic maturation of differentiation-arrested 32D-BCR/ABL cells and restored C/EBPα expression, whereas it did not have any effect on cytokine-independent growth and clonogenic potential. Consistent with its ability to bind hnRNP E2, miR-328 also rescued C/EBPα expression and differentiation of cytokine-independent BCR/ABL-expressing myeloid precursor 32Dcl3 cells. By contrast, BCR/ABL-dependent colony formation was markedly reduced by overexpression of miR-15a and miR-16-1 (65–75% inhibition, P<0.001) and slightly decreased (40–50% inhibition, P<0.01) by ectopic miR-328 expression. Altogether, these data not only reinforce the importance of BCR/ABL-dependent post-transcriptional regulation of gene expression during CML disease progression but also suggest a new function for microRNAs as functional regulators of RNA binding proteins involved in the control of malignant cell growth, survival and differentiation.

Role of BCR/ABL Gene Expression Levels in Determining the Phenotype and Imatinib Sensitivity of Transformed Human Hematopoietic Cells.

Increased levels of BCR/ABL expression in chronic myelogenous leukemia (CML) cells is associated with disease progression from chronic phase (CP) to blast crisis (BC), and resistance to imatinib mesylate (IM) treatment. However, it is not clear if these associations directly result from elevated BCR/ABL expression levels or reflect coincidental occurrence of additional abnormalities. Here we used an experimental model of human CML based on ectopic expression of the BCR/ABL gene in human CD34+ cells to directly investigate the role of increased BCR/ABL expression levels in determining the phenotype of transformed hematopoietic cells and their IM response. CD34+ cells were transduced with retroviral vectors expressing BCR/ABL and GFP. Cells with low and high levels of GFP and BCR/ABL expression (BAlo and BAhi) were selected by flow cytometry. We confirmed increased expression of BCR/ABL in GFP high cells by quantitative RT-PCR and Western blot analysis. The average BCR/ABL expression levels in BAlo cells (0.51 ± 0.19, n=3) were consistent with those observed in CD34+ cells from CML CP (0.36 ± 0.11, n=4) and accelerated phase (AP) patients (0.62 ± 0.08, n=3), and in BAhi (0.95 ± 0.09, n=3) cells with those observed in CML BC patients (0.98 ± 0.09, n=3). BAhi cells demonstrated significantly higher expansion after growth factor (GF) culture compared with BAlo cells (expansion of control cells: 14.3 ± 3.7, BAlo: 33.7 ± 9.3 and BAhi: 65.4 ± 16.4, n=4). Increased expansion was related to both increased cell division and reduced apoptosis. The proliferation rate of BAhi cells, measured by labeling cells with the fluorescent dye SNARF-1, was significantly increased compared with BAlo cells (proliferation index for controls: 5.3 ± 1.0, BAlo: 24.3 ± 8.1, and BAhi: 41.8 ± 11.9, n=4). BAhi cells demonstrated increased resistance to apoptosis upon GF deprivation, (28 ± 6.7%, n=5) compared with BAlo (45 ± 8%, n=5) or control cells (56 ± 9.3%, n=5). Interestingly, increased BCR/ABL expression levels in human hematopoietic cells was associated with enhanced IM sensitivity rather than with IM resistance (IC50 for BAhi = 0.025 μM; BAlo = 0.2 μM), related to both increased inhibition of proliferation (% inhibition of 55 ± 4.3% for BAhi, vs. 35.5 ± 4.4% for BAlo cells with 0.1 μM IM, n=4) as well as increased induction of apoptosis (% increase in apoptosis with 0.1μM IM for BAhi 26.4 ± 4% vs. BAlo 8.4 ± 3 %, n=5). We did not observe a significant difference in phosphorylation of AKT and MAPK between BAhi and BAlo cells, but did observe significantly increased STAT5 phosphorylation in BAhi CD34+ cells compared to BAlo cells (pSTAT5:STAT5 for BAlo = 0.41 ± 0.21, BAhi = 1.01 ± 0.1). Furthermore, electromobility shift assays (EMSA) confirmed increased STAT5 promoter activity in BAhi cells compare to BAlo cells. In conclusion, increased levels of BCR/ABL expression in human CD34+ cells results in increased expansion in hematopoietic cell numbers related to enhanced proliferation and increased resistance to apoptosis. However expression of high levels of BCR/ABL was associated with enhanced rather than reduced sensitivity to IM. These observations suggest that BCR/ABL overexpression may contribute to disease progression in CML but may not play a direct role in IM resistance in cells overexpressing BCR/ABL. Our results suggest a role of increased STAT5 activity in abnormal growth of BCR/ABL overexpressing cells.

Loss of p53 impedes the antileukemic response to BCR-ABL inhibition

Targeted cancer therapies exploit the continued dependence of cancer cells on oncogenic mutations. Such agents can have remarkable activity against some cancers, although antitumor responses are often heterogeneous, and resistance remains a clinical problem. To gain insight into factors that influence the action of a prototypical targeted drug, we studied the action of imatinib (STI-571, Gleevec) against murine cells and leukemias expressing BCR-ABL, an imatinib target and the initiating oncogene for human chronic myelogenous leukemia (CML). We show that the tumor suppressor p53 is selectively activated by imatinib in BCR-ABL-expressing cells as a result of BCR-ABL kinase inhibition. Inactivation of p53, which can accompany disease progression in human CML, impedes the response to imatinib in vitro and in vivo without preventing BCR-ABL kinase inhibition. Concordantly, p53 mutations are associated with progression to imatinib resistance in some human CMLs. Our results identify p53 as a determinant of the response to oncogene inhibition and suggest one way in which resistance to targeted therapy can emerge during the course of tumor evolution.

Deletion of any part of the BCR or ABL gene on the derivative chromosome 9 is a poor prognostic marker in chronic myelogenous leukemia

To evaluate the prognostic significance of submicroscopic deletions of the ABL or BCR gene associated with t(9;22) in chronic myelogenous leukemia (CML), we investigated the incidence of an ABL or BCR deletion on derivative chromosome 9 using fluorescence in situ hybridization (FISH). FISH was performed using the LSI BCR/ABL dual-fusion translocation probe on bone marrow cells of 86 patients with CML. Of 86 patients, ABL deletion was detected in 13 (15.1%) patients and BCR deletion in 8 patients (9.3%). Patients with ABL deletion showed shorter event-free survival time (EFS) than those without ABL deletion ( P = 0.020). Patients with BCR deletion showed significantly short overall survival time (OS; P = 0.039). Patients with ABL and/or BCR deletion (14/86 patients, 16.3%) showed significantly short OS and EFS (median OS, 43.0 months; median EFS, 40.0 months), compared to the patients without any BCR or ABL gene deletions (median OS, 94.0 months; median EFS, 90.0 months; P = 0.041 for OS, P = 0.008 for EFS). All the patients with BCR deletion, except for one, had a concomitant ABL deletion, suggesting that BCR deletion occurs in conjunction with ABL deletion. In patients with ABL deletion only, BCR/ABL rearrangement with b2a2 mRNA type tended to be more frequent than in patients without any deletion of the two genes ( P = 0.073). Deletion of any of the BCR or ABL genes on derivative chromosome 9 was associated with both short OS and EFS. We conclude that deletion of not only the ABL gene, but also of the BCR gene, is a poor prognostic marker that indicates rapid disease progression in CML.

Genomewide screening of DNA copy number changes in chronic myelogenous leukemia with the use of high‐resolution array‐based comparative genomic hybridization

Chronic myelogenous leukemia (CML) evolves from an indolent chronic phase (CP) characterized by the Philadelphia chromosome. Without effective therapy, it progresses to an accelerated phase (AP) and eventually to a fatal blast crisis (BC). To identify the genes involved in stage progression in CML, we performed a genomewide screening of DNA copy number changes in a total of 55 CML patients in different stages with the use of the high-resolution array-based comparative genomic hybridization (array CGH) technique. We constructed Human 1M arrays that contained 3,151 bacterial artificial chromosome (BAC) DNAs, allowing for an average resolution of 1.0 Mb across the entire genome. In addition to common chromosomal abnormalities, array CGH analysis unveiled a number of novel copy number changes. These alterations included losses in 2q26.2-q37.3, 5q23.1-q23.3, 5q31.2-q32, 7p21.3-p11.2, 7q31.1-q31.33, 8pter-p12(p11.2), 9p, and 22q13.1-q13.31 and gains in 3q26.2-q29, 6p22.3, 7p15.2-p14.3, 8p12, 8p21.3, 8p23.2, 8q24.13-q24.21, 9q, 19p13.2-p12, and 22q13.1-q13.32 and occurred at a higher frequency in AP and BC. Minimal copy number changes affecting even a single BAC locus were also identified. Our data suggests that at least a proportion of CML patients carry still-unknown cryptic genomic alterations that could affect a gene or genes of importance in the disease progression of CML. This article contains Supplementary Material available at http://www.interscience.wiley.com/jpages/1045-2257/suppmat.

Secondary Leukemia after Imatinib Mesylate (IM) Therapy for Chronic Myelogenous Leukemia (CML).

Disease progression in CML is often marked by the acquisition of cytogenetic abnormalities beyond the Philadelphia chromosome (Ph), referred to as clonal evolution (CE). In contrast, some patients (pts) develop chromosomal abnormalities in Ph-negative cells while on various therapies for CML, including IM. These abnormalities are frequently transient and their clinical consequence is unclear. Although some reports have suggested these abnormalities might be associated with secondary myelodysplastic syndrome (MDS), the diagnosis has not been established using standard criteria, usually only with megaloblastoid changes and, rarely with increased blasts. We report 2 cases of pts treated with imatinib for CML who subsequently developed chromosomal abnormalities in Ph negative cells, one of whom later developed MDS (RAEB II) and the other acute myelogenous leukemia (AML), a clinical consequence as yet unreported in the literature.Patient #1: A 51-year-old woman presented to MDACC in January 2001 having been diagnosed with CML in October 1999. Her only treatment in the preceding 14 months had been hydroxyurea. She was begun on treatment with imatinib at a dose of 400 mg daily. With no evidence of a major cytogenetic response after six months, the dose was increased to 600mg daily. She developed pancytopenia, requiring the use of filgrastim (G-CSF), erythropoietin and frequent red cell and platelet transfusions. Bone marrow biopsy showed significant dysplasia with 4% blasts and no evidence of CML. Cytogenetic analysis showed 4/20 (20%) of Ph-negative cells with monosomy 7, and no cells with Ph. IM was held for 6 weeks with no improvement in pancytopenia. Repeat bone marrow biopsy showed 14% blasts and cytogenetic analysis continued to show the presence of 20% Ph-negative cells with monsomy 7. Fluorescence in situ hybridization (FISH) performed on the blasts showed only the presence of monosomy 7 with no Ph thus confirming the diagnosis of a secondary MDS (RAEB II).Patient 2: A 64-year-old man presented in January 2001 with CML. He was initially treated with hydroxyurea followed by interferon and cytarabine. Treatment related toxicities dictated a change to IM 400 mg daily. With no major cytogenetic response after 12 months, the dose was increased to 600 mg daily with filgrastim and erythropoietin to support suppressed cell counts. Twenty months later, a repeat bone marrow biopsy showed 12% blasts, suggesting a transformation to accelerated phase. Cytogenetics showed a dual population of cells, 2/10 (10%) Ph-positive with -Y and 3/20 (15%) with monosomy 7 and no Ph. Sixteen days later, after initiation of therapy with the experimental compound, AMN-107, the bone marrow showed 38% blasts. Repeat bone marrow biopsy 2 weeks later showed 62% blasts which by FISH showed monosomy 7 and no Ph confirming a secondary AML. To our knowledge these are the first cases of secondary high-risk MDS (RAEB II) and AML after imatinib mesylate therapy occurring in pts with chromosomal abnormalities in Ph-hegative metaphases. Interestingly, both patients had monsomy 7. This is a rare phenomenon as these represent 2 of 1186 pts (0.1%; 95CI 0.00, 0.01) treated with IM at our institution over more than 5 years. This underscores the need to monitor periodically with cytogenetic analysis pts. with CML treated with imatinib.

The tumor suppressor PP2A is functionally inactivated in blast crisis CML through the inhibitory activity of the BCR/ABL-regulated SET protein

The oncogenic BCR/ABL kinase activity induces and maintains chronic myelogenous leukemia (CML). We show here that, in BCR/ABL-transformed cells and CML blast crisis (CML-BC) progenitors, the phosphatase activity of the tumor suppressor PP2A is inhibited by the BCR/ABL-induced expression of the PP2A inhibitor SET. In imatinib-sensitive and -resistant (T315I included) BCR/ABL+ cell lines and CML-BC progenitors, molecular and/or pharmacological activation of PP2A promotes dephosphorylation of key regulators of cell proliferation and survival, suppresses BCR/ABL activity, and induces BCR/ABL degradation. Furthermore, PP2A activation results in growth suppression, enhanced apoptosis, restored differentiation, impaired clonogenic potential, and decreased in vivo leukemogenesis of imatinib-sensitive and -resistant BCR/ABL+ cells. Thus, functional inactivation of PP2A is essential for BCR/ABL leukemogenesis and, perhaps, required for blastic transformation.

Oncogenic interaction between BCR-ABL andNUP98-HOXA9 demonstrated by the use of an in vitro purging culture system

Chronic myelogenous leukemia (CML) is a clonal stem cell disease caused by the BCR-ABL oncoprotein and is characterized, in its early phase, by excessive accumulation of mature myeloid cells, which eventually leads to acute leukemia. The genetic events involved in CML's progression to acute leukemia remain largely unknown. Recent studies have detected the presence of the NUP98-HOXA9 fusion oncogene in acute leukemia derived from CML patients, which suggests that these 2 oncoproteins may interact and influence CML disease progression. Using in vitro purging of BCR-ABL-transduced mouse bone marrow cells, we can now report that recipients of bone marrow cells engineered to coexpress BCR-ABL with NUP98-HOXA9 develop acute leukemia within 7 to 10 days after transplantation. However, no disease is detected for more than 2 months in mice receiving bone marrow cells expressing either BCR-ABL or NUP98-HOXA9. We also provide evidence of high levels of HOXA9 expressed in leukemic blasts from acute-phase CML patients and that it interacts significantly on a genetic level with BCR-ABL in our in vivo CML model. Together, these studies support a causative, as opposed to a consequential, role for NUP98-HOXA9 (and possibly HOXA9) in CML disease progression.

Telomere length dynamics in normal individuals and in patients with hematopoietic stem cell-associated disorders.

The telomere length in nucleated peripheral blood (PB) cells indirectly reflects the mitotic history of their precursors: the hematopoietic stem cells (HSCs). The average length of telomeres in PB leukocytes can be measured using fluorescence in situ hybridization and flow cytometry (flow FISH). We previously used flow FISH to characterize the age-related turnover of HSCs in healthy individuals. In this review, we describe results of recent flow FISH studies in patients with selected hematopoietic stem cell-associated disorders: chronic myelogenous leukemia (CML) and several bone marrow failure syndromes. CML is characterized by a marked expansion of myeloid Philadelphia chromosome positive (Ph+) cells. Nevertheless, nonmalignant (Ph-) HSCs typically coexist in the bone marrow of CML patients. We analyzed the telomere length in > 150 peripheral blood leukocytes (PBLs) and bone marrow samples of patients with CML as well as samples of Ph- T-lymphocytes. Compared to normal controls, the overall telomere fluorescence in PBLs of patients with CML was significantly reduced. However, no telomere shortening was observed in Ph- T-lymphocytes. Patients in late chronic phase (CP) had significantly shorter telomeres than those assessed earlier in CP. Our data suggest that progressive telomere shortening is correlated with disease progression in CML. Within the group of patients with bone marrow failure syndromes, we only found significantly shortened telomeres (compared to age-adjusted controls) in granulocytes from patients with aplastic anemia (AA). Strikingly, the telomere length in granulocytes from AA patients who had recovered after immunosuppressive therapy (recAA) did not differ significantly from controls, whereas untreated patients and nonresponders with persistent severe pancytopenia (sAANR) showed marked and significant telomere shortening compared to healthy donors and patients with recAA. Furthermore, an inverse correlation between age-adjusted telomere length and peripheral blood counts was found in support of a model in which the degree of cytopenia and the amount of telomere shortening are correlated. These results support the concept of extensive proliferation of HSCs in subgroups of AA patients and suggest a potential use of telomere-length measurements as a prognostic tool in this group of disorders as well.

Expression of apoptosis proteins in chronic myelogenous leukemia: associations and significance.

The mechanisms favoring the growth advantage of Philadelphia chromosome positive cells over normal cells in chronic myelogenous leukemia (CML) are not fully elucidated but could be due partly to altered apoptosis and longer survival of CML clones. Also, little is known about the biologic characteristics of disease progression in CML. Bcl-2 expression has been demonstrated to exert an antiapoptotic effect resulting in increased cell survival. Other proteins such as Bax and Bad are proapoptotic proteins. Fas, a cell surface protein, can be triggered by an appropriate death-promoting ligand (FasL) to activate downstream caspases pivotal in initiation of programmed cell death. Although the mechanisms underlying cellular proliferative and apoptotic pathways are complex, with involvement of multiple interlocking proteins, the relative expression of pro- and antiapoptotic proteins may have an influence on disease progression. This study aimed to determine whether the changes in the cellular expression of Bcl-2, Bax, and Fas correlate with caspase-3 activity and disease progression in CML, or with response to interferon (IFN)-alpha therapy and prognosis in early chronic phase CML. Bcl-2, Bax, and Fas expression were measured on whole cell lysates from bone marrow mononuclear cell fractions by Western blot analysis and quantitative radioimmunoassay. Caspase-3 activity was determined using the DEVD system. Specimens from 203 patients with CML were examined. These included 130 patients in early chronic phase disease (ECP; diagnosis to therapy, < or =12 months), 33 patients in late chronic phase (diagnosis to therapy, > 12 months), 27 patients in accelerated phase, and 13 patients in blastic phase. Correlations between apoptosis proteins and CML phases, risk groups in ECP, and response to IFN-alpha therapy and survival in ECP were investigated by standard statistical methods, and positive findings were assessed by multivariate analysis. Levels of Bcl-2, Fas, Bax, and caspase-3 activity did not correlate with disease progression. Among patients in ECP, higher Fas levels correlated with poorer risk groups (P = 0.05) and higher caspase-3 activity correlated with better risk groups (P = 0.048). With IFN-alpha therapy, major cytogenetic responses were noted in 30% of patients with high Fas and 53% with low Fas (P = 0.016) and failure to achieve a complete hematologic response (CHR) in 25% versus 2% (P = 0.0001). Survival was shorter with high Fas levels (5-year rates, 71% vs. 52%; P = 0.002), and the independent poor prognostic significance of high Fas levels was confirmed by multivariate analysis (P = 0.014). Response to IFN-alpha therapy and survival were not significantly different by different levels of Bcl-2, Bax, or caspase-3 activity. High Fas levels were associated with intrinsically worse disease at diagnosis, whereas high caspase-3 activity was associated with good risk disease. In ECP CML, high Fas levels were associated with significantly worse response to IFN-alpha therapy and with significantly worse survival. The influence of these cellular proteins and caspase-3 activity on apoptosis in CML is complex and merits further investigation.

Telomere length shortening is associated with disease evolution in chronic myelogenous leukemia.

We studied telomere length in the peripheral blood leukocyte samples of a large group of patients with chronic myelogenous leukemia (CML) by Southern blot hybridization using the (TTAGGG)4 probe. The average telomere length expressed as the peak telomere repeat array (TRA) of the peripheral blood samples obtained from a group of 34 healthy age-matched controls ranged between 7.6 and 10.0 kb and the mean peak TRA was 8.7 kb. Forty-one patients in the chronic phase of CML were studied; 32/41 (78%) showed telomere reduction (<7.6 kb) relative to age-matched controls and the mean peak TRA was 6.4 kb (range 4.0-10.6 kb). Serial samples were analysed from 12 patients at both chronic phase and during disease progression. The leukocyte DNA of all 12 patients in accelerated phase and/or blast crisis showed telomere reduction relative to age-matched controls and the mean peak TRA was 4.1 kb (range 3.0-5.4 kb). The peak TRA in the accelerated or blast phase was reduced compared with the corresponding paired sample in the chronic phase in all cases studied. These data show that a marked reduction in telomere length is associated with disease progression in CML.

Autologous Activated Natural Killer Cells Suppress Primitive Chronic Myelogenous Leukemia Progenitors in Long-Term Culture

A graft-versus-leukemia effect has been well documented to prevent relapse in chronic myelogenous leukemia (CML) after allogeneic marrow transplantation. One type of lymphocytes that may contribute to this effect are natural killer cells (NK), which after activation with interleukin (IL)-2, exhibit a broad range of cytolytic activity against allogeneic and autologous cells. We have previously demonstrated that IL-2-activated NK (ANK) can be generated from blood of patients with CML and are benign in origin. Their proliferation and function, however, diminish with disease progression in CML, suggesting a role in tumor surveillance. We studied the effect of IL-2-activated NK (ANK) on normal and malignant primitive and committed progenitors in a novel long-term bone marrow culture (LTBMC) assay. Because ANK destroy marrow stromal layers, the use of classic stroma-dependent long-term cultures is not possible. Therefore, we used the stroma noncontact LTBMC system developed in our laboratory to analyze the effect of autologous ANK cells on primitive hematopoietic progenitors. Autologous ANK (CD56+/CD3-) were generated from the peripheral blood of 10 patients with chronic phase CML and from six normal individuals by culturing CD5/CD8-depleted mononuclear cells for 14 days in 1,000 U/mL IL-2. At the same time ANK cultures were initiated, sorted normal (CD34+/DR+) marrow populations were plated in Transwell inserts of the stroma noncontact culture. On day 15, hydrocortisone, which rapidly inhibits ANK function, was removed, and autologous ANK were added to the Transwell inserts with fresh LTBMC medium without hydrocortisone but supplemented with 1,000 U/mL IL-2. After 48 hours, the number of colony-forming cells (CFC) was enumerated in methylcellulose culture. To determine the effect of ANK on more primitive long-term culture-initiating cells (LTCIC), the IL-2-supplemented LTBMC medium was replaced with fresh hydrocortisone containing LTBMC medium, and cultures were maintained for an additional 5 weeks. We demonstrate that autologous ANK did not suppress normal CFC or LTCIC. In contrast, ANK from eight patients with CML with potent cytotoxicity against NK-sensitive (K562) NK-resistant (Raji) tumor targets exhibited an ANK dose-dependent suppression of both CFC and LTCIC. Interestingly, ANK from two patients with CML who exhibited diminished cytotoxicity also did not suppress autologous CFC and LTCIC. These studies indicate that ANK with potent major histocompatibility complex unrestricted cytotoxic activity suppress malignant hematopoiesis. This effect was not mediated by soluble factors and was absolutely dependent on direct cell-to-cell contact. We further demonstrate that the beta2 integrin receptor is involved in ANK recognition of CML targets. These observations support the use of autologous ANK therapy to prevent relapse of CML after autologous marrow transplantation or use of ANK to purge CML marrow for autologous transplantation.