Clinical implications of fluorescence in situ hybridization analysis in 13 chronic myeloid leukemia cases: Ph-negative and variant Ph-positive.

Thirteen chronic myeloid leukemia (CML) patients, 10 with variant Philadelphia (Ph) translocations and 3 Ph negative cases, were analyzed by fluorescence in situ hybridization (FISH) with the use of BCR and ABL cosmid probes and a chromosome 22 painting probe. In the variant Ph translocations, the BCR-ABL fusion gene was located on the Ph chromosome; in 1 CML Ph-negative patient, the BCR-ABL fusion gene was located on the Ph chromosome; and, in 2 patients, it was located on chromosome 9. The chromosome 22 painting probe was detected on the third-party chromosome of the variant translocation, and in none of the variant translocations was there any detectable signal on chromosome 9. In CML patients with clonal evolution of a simple Ph, a signal of the chromosome 22 painting probe was detected on the der(9) of the Ph translocation. It was concluded that the variant Ph translocations evolved simultaneously in a three-way rearrangement. The clinical parameters of the 13 patients were similar to those of a large group of CML patients with a simple Ph translocation. It is suggested that, to determine the prognosis of CML patients with a complex karyotype, FISH analysis with a chromosome 22 painting probe be performed.     

Interphase fluorescence in situ hybridization studies for the detection of 9q34 deletions in chronic myelogenous leukemia: a practical approach to clinical diagnosis

Chronic myelogenous leukemia (CML) is characterized by the Philadelphia chromosome (Ph) in more than 90% of cases. Recent studies using fluorescence in situ hybridization (FISH) have shown that in a subset of patients with CML, deletions of 9q34 involving the argininosuccinate synthetase region occur at the time of the Philadelphia translocation and are associated with a poor prognosis. We performed interphase FISH studies in 152 cases of CML using a dual-color, dual-fusion probe system with a third probe directed at 9q34. Cytogenetic studies showed a simple (typical) Ph in 124/152 (82%), a cryptic Ph in 11/152 (7%), and a variant Ph chromosome with a complex translocation in 17/152 (11%) of cases. Interphase FISH studies showed single BCR/ABL fusion patterns in 48/152 (32%) of cases. Deletions of 9q34 were observed in 14% of all the cases and were present in 46% of cases with single BCR/ABL fusion pattern. All the 9q34 deletions occurred in cases with single BCR/ABL fusion signal. However, a single-fusion pattern is not specific for 9q34 deletions, and cases should be routinely screened for the presence of this prognostically significant abnormality by using a third probe directed specifically at 9q34.     

Amplification of BCR-ABL and t(3;21) in a patient with blast crisis of chronic myelogenous leukemia

The Philadelphia (Ph) chromosome, or t(9;22), is the hallmark of chronic myelogenous leukemia (CML). It results in juxtaposition of the 5' part of the BCR gene on chromosome 22 to the 3' part of the ABL1 gene (previously ABL) on chromosome 9. CML is clinically characterized by three distinct phases: chronic, accelerated, and blast phase. Blast crisis is characterized by the rapid expansion of a population of differentiation arrested blast cells (myeloid or lymphoid cells population), with secondary chromosomal abnormalities present. We report a case of myeloid blast crisis of CML resistant to imatinib mesylate and chemotherapy. By use of cytogenetic, fluorescence in situ hybridization, and comparative genomic hybridization methods, we identified a cluster of BCR-ABL amplification on inverted duplication of the Ph chromosome with t(3;21)(q26;q22) and increased genomic levels of the RUNX1 gene (previously AML1). The t(3;21)(q26;q22) is a recurrent chromosomal abnormality in some cases of CML blast phase and in treatment-related myelodysplastic syndrome and acute myeloid leukemia. Amplification or copy number increase of RUNX1 has been reported in childhood acute lymphoblastic leukemia. Our study indicated that the progenitor of CML was BCR-ABL dependent through the amplification of Ph chromosome as a mechanism of resistance to imatinib therapy. The coexistence of BCR-ABL and t(3;21)(q26;q22) with RUNX1 rearrangement might play a pivotal role in the CML blast transformation.     

The t(4;22)(q12;q11) in atypical chronic myeloid leukaemia fuses BCR to PDGFRA

Chronic myeloid leukaemia (CML) is characterized by the presence of the BCR-ABL fusion gene, usually in association with the t(9;22)(q34;q11) translocation. We report here the identification and cloning of a rare variant translocation, t(4;22)(q12;q11), in two patients with a CML-like myeloproliferative disease (MPD). RT-PCR indicated that both patients were negative for BCR-ABL, but FISH analysis suggested that the BCR gene was rearranged. Since other translocations in MPDs frequently involve tyrosine kinases, we designed a multiplex PCR to search for mRNA fusions between BCR and three potential partner genes at 4q12: KIT, KDR and PDGFRA. An unusual inframe BCR-PDGFRA fusion mRNA was identified in both patients, with either BCR exon 7 or exon 12 fused to short BCR intron-derived sequences, which were in turn fused to part of PDGFRA exon 12. Sequencing of the genomic breakpoint junctions showed that the chromosome 22 breakpoints fell in BCR introns whereas the chromosome 4 breakpoints were within PDGFRA exon 12. This is the first report of a fusion gene that involves PDGFRA. Our findings indicate that apparently simple cytogenetic variants of t(9;22) do not always mask a cryptic BCR-ABL fusion, even when found in association with clinical and haematological indications of CML.     

荧光原位杂交检测慢性粒细胞白血病

目的 探讨对慢性粒细胞白血病进行荧光原位杂交(fluorescence in situ hybridization,FISH)检测的意义.方法 对158例慢性粒细胞白血病标本采用24 h短期培养法制备染色体,然后应用双色双融合BCR/ABL探针进行FISH检测,部分标本同时采用R显带技术进行染色体核型分析.结果 158例中共检出Ph阳性标本98例,其中69例(70.4%)为典型双色双融合BCR/ABL探针信号模式(1R1G2F),其余29例(29.6%)为3类12种非典型模式.各种非典型信号模式中出现频率较高的依次为:1R1G1F7例(7.1%)、2R1G1F 5例(5.1%)、1R1G2F&1R1G3F 4例(4.1%)、2R2G1F 3例(3.1%).对18例有核型资料的非典型信号的病例分析显示:其中3例特殊信号系由变异Ph易位引起;2例中出现的3个融合信号来源于附加的Ph染色体;4例核型与FISH结果不吻合,提示染色体分析存在错漏之处;3例染色体为典型Ph易位,而FISH结果为单个融合信号,系由der(9)号的部分缺失所致;3例核型中未发现Ph染色体.但FISH显示40%～64%的细胞中存在一个融合信号,从而明确慢性粒细胞白血病诊断;3例是移植或经格列卫治疗后的患者,染色体均为正常核型,而FISH检测到极小比例的阳性细胞.结论 FISH在慢性粒细胞白血病诊断、判断变异易位、隐匿Ph易位、衍生9号缺失、干扰素及格列卫的疗效观察以及移植后监测等诸多方面均具有重要价值.     

BCR/ABL fusion located on chromosome 9 in chronic myeloid leukemia with a masked Ph chromosome

A reciprocal translocation, t(10; 22) (q22; q11), resulting in a masked Ph chromosome was identified in a patient diagnosed with chronic myeloid leukemia (CML). Both homologs of chromosome 9 were of the normal pattern. Two signals for the ABL probe, both of them hybridized to chromosome 9, were demonstrated via fluorescence in situ hybridization (FISH). Furthermore, cohybridization with two differently labeled BCR/ABL translocation DNA probes indicated a BCR/ABL fusion apparently located on 9q34. Molecular studies revealed a rearrangement of the BCR region and expression of a chimeric BCR/ABL mRNA of CML configuration. These findings indicate that the BCR/ABL fusion resulted from an unusual relocation of the BCR gene from its normal position on 22ql I to 9q34 adjacent to the ABL gene.     

High-resolution analysis of acquired genomic imbalances in bone marrow samples from chronic myeloid leukemia patients by use of multiple short DNA probes

Chronic myeloid leukemia (CML) is a biphasic hematopoietic malignancy associated with a single cytogenetic aberration, the Philadelphia translocation t(9;22)(q34;q11), resulting in the BCR-ABL1 fusion oncogene. Molecular heterogeneity was recently demonstrated in the form of extensive deletion of chromosomes 9 and 22 material from the der(9)t(9;22) in 15% of CML patients. The deletions were associated with a worse disease prognosis. Further genetic heterogeneity is seen during the terminal blast crisis stage of CML, in the form of additional non-random chromosome abnormalities. These include most frequently an extra copy of the Ph chromosome, trisomy 8, and isochromosome 17q. We used the genetic heterogeneity of CML as a framework to explore a new technique for high-throughput assessment of locus copy number in malignancy. Multiplex amplifiable probe hybridization (MAPH) relies on the ability of numerous short (100-300 bp) DNA probes to be recovered quantitatively by use of a common primer pair after hybridization to genomic DNA. Derivative chromosome 9 deletions were successfully mapped in a CML cell line (MC3) and nine patient bone marrow samples by simultaneous hybridization of 10 MAPH probes. All results were confirmed by fluorescence in situ hybridization. MAPH was found to be informative in the presence of up to 50% of normal cells, thus establishing the sensitivity of the technique in clonal tumor cell populations. MAPH was performed effectively on DNA samples extracted from fresh or methanol/acetic acid-fixed clonal cell populations. Amplifications of BCR-ABL1 were also detected and quantified in four CML cell lines by use of MAPH probes specific for ABL1 exon 11 and BCR exon 1. Our results demonstrate that MAPH is a reproducible high-throughput method suitable for the assessment of genomic imbalances of multiple loci in tumor DNA samples with heterogeneous cell populations at a resolution of 100-300 bp.     

荧光原位杂交技术在诊断变异Ph易位及Ph(一)慢性髓细胞白血病中的应用

目的 探讨荧光原位杂交(fluorescence in situ hybridization,FISH)技术在诊断变异Ph易位及Ph(-)慢性髓细胞白血病(chronic myelocytic leukemia,CML)中的应用价值.方法 应用常规R显带方法,对9例伴有变异Ph易位和2例Ph(-)CML患者采用双色双融合bcr/abl探针进行FISH检测.结果 9例变异Ph易位CML患者异常核型除涉及9和22号染色体外,还涉及1、3、5、12、13、15、17、21号染色体,且部分类型为重现性异常,FISH结果均为阳性,信号特征为2R2G1Y;2例Ph(-)CML患者核型正常,FISH结果阳性,信号特征分别为1R1G2Y和1R1G1Y.结论 FISH技术对伴有变异Ph易位及Ph(-)CML患者的诊断更具有优势,可根据阳性细胞信号特征分析其异常核型,判断标记基因异常改变情况,是常规染色体显带分析的有益补充.     

双色双融合与额外信号探针在BCR/ABL融合基因检测中的比较及其意义

目的 探讨DCCF(dual color dual fusion)探针与ES(extra signal)探针在BCR/ABL融合基因检测中信号表现的特点,并明确其信号特征与染色体核型的相互关系.方法 对初治65例慢性粒细胞白血病(chronic myelocytic leukemia,CML)及50例急性淋巴细胞白血病(acute lymphoblastic leukemia,ALL)患者骨髓标本进行BCR/ABL的DCDF探针的荧光原位杂交(fluorescence in situ hybridization,FISH)检测,FISH阳性标本则使用ES探针再次进行荧光原位杂交进行BCR断裂点的检测,同时对其中47例CML和40例ALL进行了核型分析.结果 FISH结果示65例CML均为BCR/ABL阳性,DCDFFISH中有17例为非典型信号表现,ES-FISH有12例为非典型信号表现;50例ALL中7例BCR/ABL阳性,ES探针显示5例BCR断裂点位于m-bcr,2例位于M-bcr.核型分析CML检出Ph阳性98%(43/44),ALL检出Ph阳性22%(7/32).结论 DCDF-FISH、ES-FISH以及核型分析各有其特性.根据每种方法的特性,对实验结果进行综合分析可对遗传学特征作出更准确判断.

Abstract：

Objective To investigate the signal patterns of dual color dual fusion (DCDF) probe and extra signal (ES) probe in the detection of BCR/ABL fusion gene, and illustrate the relation between the fluorescence in situ hybridization (FISH) pattern and the karyotype. Methods Sixty-five cases of chronic myelocytic leukemia(CML) and 50 cases of acute lymphoblastic leukemia (ALL) were detected by FISH with DCDF probe, the BCR/ABL positive samples were detected by FISH with ES probe. Among these cases, 47 cases of CML and 40 cases of ALL perform conventional cytogenetics simultaneously. Results All 65 cases of CML were all BCR/ABL positive by FISH. 17 cases showed the atypical pattern by DCDFFISH, and 12 cases showed the atypical pattern by ES-FISH. There were 7 cases of BCR/ABL positive in 50 cases of ALL by FISH. By ES-FISH, there were 5 cases in which the break-point of BCR gene was located in m-bcr, 2 cases in which the break-point of BCR gene was located in M-bcr. Conventional cytogenetics demonstrated that 43/44(98 %) cases of CML and 7/32(22 %) cases of ALL were Ph positive.Conclusion The features of DCDF-FISH, ES-FISH and conventional eytogenetic are different from each other. According to the features of these method, it can increase the precision of the adjustment of genetic feature to analyze these results comprehensively.     

双色双融合与额外信号探针在BCR/ABL融合基因检测中的比较及其意义

目的 探讨DCCF(dual color dual fusion)探针与ES(extra signal)探针在BCR/ABL融合基因检测中信号表现的特点,并明确其信号特征与染色体核型的相互关系.方法 对初治65例慢性粒细胞白血病(chronic myelocytic leukemia,CML)及50例急性淋巴细胞白血病(acute lymphoblastic leukemia,ALL)患者骨髓标本进行BCR/ABL的DCDF探针的荧光原位杂交(fluorescence in situ hybridization,FISH)检测,FISH阳性标本则使用ES探针再次进行荧光原位杂交进行BCR断裂点的检测,同时对其中47例CML和40例ALL进行了核型分析.结果 FISH结果示65例CML均为BCR/ABL阳性,DCDFFISH中有17例为非典型信号表现,ES-FISH有12例为非典型信号表现;50例ALL中7例BCR/ABL阳性,ES探针显示5例BCR断裂点位于m-bcr,2例位于M-bcr.核型分析CML检出Ph阳性98%(43/44),ALL检出Ph阳性22%(7/32).结论 DCDF-FISH、ES-FISH以及核型分析各有其特性.根据每种方法的特性,对实验结果进行综合分析可对遗传学特征作出更准确判断.     

A fluorescence in situ hybridization study of complex t(9;22) in two chronic myelocytic leukemia cases with a masked Philadelphia chromosome

The t(9;22)(q34;q11) is evident in more than 90% of patients with chronic myelocytic leukemia (CML) and gives rise to the Philadelphia chromosome (Ph). Approximately 5%-10% of CML patients show variant translocations involving other chromosomes in addition to chromosomes 9 and 22. In some variant translocations, additional material is transferred on der(22), resulting in a masked Ph chromosome. In this paper, we report two apparently Ph-negative (Ph-) CML cases showing a t(7;9;22)(q22;q34;q11) and a t(8;9;22)(q12;q34;q11), respectively. A detailed molecular cytogenetic characterization was performed by fluorescence in situ hybridization (FISH), which disclosed the presence of the 5'BCR/3'ABL fusion gene on the der(7) and der(8) chromosomes, respectively. Derivative (22) appeared as a masked Ph chromosome in both cases. FISH analysis with appropriate BAC/PAC clones allowed us to precisely characterize the complex chromosomal rearrangements that were not detected by conventional cytogenetic analysis.     

Fluorescence in situ hybridization: a highly efficient technique of molecular diagnosis and predication for disease course in patients with myeloid leukemias.

The accuracy of cytogenetic diagnosis in the management of hematological malignancies has improved significantly over the past 10 years. Fluorescence in situ hybridization (FISH), a technique of molecular cytogenetics, has played a pivotal role in the detection of unique sub-microscopic chromosomal rearrangements that helped in the identification of chromosomal loci, which contain genes involved in leukemogenesis. We studied the feasibility and sensitivity of the FISH technique for molecular analysis of translocations markers, t(9;22) and t(15;17) for accurate molecular diagnosis and for monitoring the disease in 21 patients with chronic myeloid leukemia (CML) who received interferon-alpha and/or chemotherapy (7 patients), bone marrow transplantation (14 patients), and 14 patients with acute promyelocytic leukemia (APL) who received all-trans-retinoic acid (ATRA) and/or chemotherapy. We also applied conventional karyotyping (CK) for identification of t(9;22) and t(15;17) at diagnosis. All CML cases had a Ph; t(9;22) and except for two cases all APL had t(15;17). The FISH studies on CML marrows in complete cytogenetic remission (CCR) (100% Ph- by CK) achieved by IFN-alpha, showed 0-2.5% of cells with BCR-ABL fusion in first cytogenetic remission (Controls, range 0.5-1.5%). Repeat follow-up FISH studies could be done in two cases in remission, which demonstrated 0-10% of cells with BCR-ABL fusion. Evaluation of Ph positive status of CML marrow at diagnosis by CK (100% Ph+ cells) and FISH (80-92% BCR-ABL fusion) pointed the existence of dormant clone of normal residual hematopoietic cells along with actively proliferating clones of Ph positive cells. Fluorescence in situ hybridization analysis of post-BMT CML marrows in CCR (0% Ph+ mitoses) could detect MRD with range of 1-6%. Among 14 patients, 9 who showed percentage of BCR-ABL positive cells (0.0-1.5%) almost similar to normal controls, 6 patients had comparatively good prognosis (disease-free survival 7-14 months). Of five patients with residual leukemic cells in the range of 2-6%, 4 relapsed within a period of 3-24 months. Fourteen APL patients in CCR [100% t(15;17) negative cells by CK] were evaluated by FISH to check the presence of residual leukemic cells. In these patients FISH could efficiently detect 1-14.5% of residual cells with PML-RARA (patients mean MRD 5%, controls mean MRD 3.5%, P=.02). Since the time of FISH analysis, 5 to 7 patients with higher fraction of leukemic cells (5-11%) relapsed within a short period (1-7 months). On the contrary, 5 of 7 patients with either absence or low percentage of PML-RARA positive cells remained in complete remission for 11-24 months. Our data show that FISH has a potential to detect and measure the fraction of aberrant malignant cells in remission marrows, induced by BMT in CML and chemotherapy in APL. These findings encourage the investigations on a large scale to merit its potential for identification of patients at high risk. In the present studies, FISH on interphase cells also demonstrated its efficiency in the molecular diagnosis by its ability to detect BCR-ABL and PML-RARA fusion in CML with masked/variant Ph and t(15;17) negative APL, respectively. The efficiency of technique in molecular diagnosis was also proved in one of the CML patients who progressed to myeloid blastic phase where interphase FISH could identify an extra BCR-ABL fusion on both chromosomes 9 indicating insertion of BCR into ABL and its duplication.     

Evidence for deletion of 9q as a two-step process in chronic myeloid leukemia

Evidence for deletion of 9q as a two-step process in chronic myeloid leukemia.Chronic myeloid leukemia (CML) is characterized by the Philadelphia translocation t(9;22)(q34;q11) resulting in the BCR/ABL fusion gene. Submicroscopic deletion of the derivative chromosome 9 occurs in a subset of these patients and is associated with poor prognosis. In the current study, we present two unusual cases of CML selected from a series of 54 consecutive cases. A detailed study using classical cytogenetics and fluorescence in situ hybridization (FISH) analysis was done using dual color extra signal FISH and whole chromosome paint in order to elucidate the mechanism of 9q deletion. One case had two clones on interphase FISH, one with and one without chromosome 9q deletion. The other case had two clones on both cytogenetic and FISH analyses, one with and one without a marker chromosome carrying chromosome 9q sequences. In this latter case, the clone with deletion of the derivative chromosome 9 comprised 21.1% at diagnosis, increasing to 36.8% after 11 months, suggesting a growth advantage. We report here evidence that deletions on 9q in CML may occur through breakage and rearrangement of chromosomes resulting in derivative chromosomes and either a marker chromosome or fragment/episome, followed by loss of chromosome material from the cell.     

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.     

Molecular cytogenetic characterization of deletions on der(9) in chronic myelocytic leukemia

The t(9;22)(q34;q11), generating the Philadelphia chromosome, is found in more than 90% of patients with chronic myelocytic leukemia (CML). Deletions adjacent to the translocation breakpoint on the derivative chromosome 9 have been described by several groups. These studies revealed two primary points: (1) genomic microdeletions were concomitant with the t(9;22) rearrangement; and (2) the location of the deleted sequence was centromeric to ABL and telomeric to BCR genes. We report on a detailed molecular cytogenetic characterization of chromosomal rearrangements in two CML patients bearing a complex variant t(9;22) and insertions of chromosome 22 sequences in 9q34. Our study shows that the location of the deleted sequences was downstream of the ABL gene and that genomic microdeletions were concomitant with the ins(9;22)(q34;q11q11) rearrangement.     

Fluorescence in situ hybridization analysis of complex translocations in two newly diagnosed Philadelphia chromosome-positive chronic myelogenous leukemia patients.

Two different complex translocations from newly diagnosed cases of Philadelphia chromosome-positive chronic myelogenous leukemia (CML) were characterized by G-banding and fluorescence in situ hybridization (FISH) analysis. In one case, a unique balanced t(9;22;9;11) (q34;q11;p22;q23) was identified by G-banding, and confirmed by FISH using MBCR/ABL and painting probes. In the second case, an apparently balanced t(19;22) was identified by G-banding analysis. FISH using MBCR/ABL probe detected the fusion gene on the derivative chromosome 22, indicating the involvement of chromosome 9. Further FISH analysis with selected painting probes showed that the t(19;22) was a result of a complex translocation involving chromosomes 9, 19, 21, and 22.