High reliability and sensitivity of the BCR/ABL1 D-FISH test for the detection of BCR/ABL rearrangements

The BCR/ABL1 fusion gene is mainly caused by the t(9; 22)(q34; q11.2) translocation, which results in the Philadelphia (Ph) chromosome. The Ph chromosome is the typical hallmark in chronic myeloid leukemia (CML), but can also be present in acute lymphoblastic leukemia (ALL) and acute myeloid leukemia (AML). The BCR/ABL1 rearrangement is an important tumor classification marker and a useful prognostic factor allowing an adequate therapy management. Ph chromosome detection by conventional cytogenetics (CC) can be hampered by low quantity and quality of metaphases from tumor cells. Furthermore, BCR/ABL1 rearrangements may be hidden due to cryptic rearrangements or complex aberrations. Therefore, molecular cytogenetic methods turned out to be useful tools for the detection of BCR/ABL1 rearrangements. We performed fluorescent in situ hybridization (FISH) with the recently developed BCR/ABL1 D-FISH probe (QBIOgene, Illkirch, F) on cultured bone marrow and peripheral blood cells of 71 patients with CML, ALL, AML, and myeloproliferative disorder (MPD). FISH results and the results of banding methods were directly compared. Based on the analyses of >200 nuclei per patient, D-FISH correlated closely with CC and allowed an accurate quantification of BCR/ABL1 rearrangements even in a low percentage of aberrant cells. No false-positive or false-negative results were obtained. Furthermore, the D-FISH probe detected three cryptic and one complex BCR/ABL1 rearrangement, which were not visible by CC. We conclude that D-FISH reliably detects standard Ph chromosomes as well as its variant translocations and accurately quantifies BCR/ABL1 rearrangements prior and during cancer treatment as well as in the phase of remission, in daily routine tumor cytogenetic diagnostics.     

Molecular response of CML patients treated with interferon-α monitored by quantitative Southern blot analysis

We analysed 459 samples from 206 chronic myeloid leukaemia (CML) patients at diagnosis and during or after treatment with interferon-α (IFN-α) by quantitative Southern blot analysis for BCR rearrangement. In a minority (2%) of Ph-positive patients, no BCR rearrangement was detectable due to breakpoints outside the major breakpoint cluster region (M-bcr) or possibly due to M-bcr deletions. Results from 235 samples were compared with the proportion of Ph-positive metaphases found in contemporaneous bone marrow specimens analysed by conventional cytogenetics. The rank correlation between both methods was 0.82 ( P <0.001). The proportion of CML cells in samples determined by Southern blot analysis (BCR ratio) was significantly different between cytogenetically-defined minor, partial, and complete response groups ( P <0.001). Empirically-derived cut-off points in the BCR ratio were introduced in order to define molecular response groups for comparison to standard cytogenetic response groups: a BCR ratio of 0% was defined as complete molecular response and ratios of 1–24%, 25–50%, and >50% were defined as partial, minor, and no molecular response, respectively. Using these cut-off points the concordance between both methods was 67% ( P <0.0001), a major cytogenetic response could be predicted or excluded in more than 90% of cases ( P <0.0001). Our findings demonstrated that quantitative Southern blot was as sensitive as cytogenetics and as peripheral blood samples are suitable for this technique it should be considered as the method of choice for routine monitoring IFN-α therapy in CML patients.     

Use of alpha interferon for the treatment of relapse of chronic myelogenous leukemia in chronic phase after allogeneic bone marrow transplantation.

Eighteen patients with relapse of chronic myelogenous leukemia (CML) after allogeneic bone marrow transplantation (BMT) were treated with recombinant human alpha 2a interferon (IFN). Relapse was defined as greater than 90% metaphases containing the Philadelphia chromosome (Ph) and hematologic abnormalities consistent with chronic-phase (CP) CML. There were 11 males and seven females, with a median age of 38 years (range, 3 to 55). Three patients relapsed after second BMT. Only one patient had received T-cell-depleted marrow initially. The initial IFN dose of 3 x 10(6) U/m2/d was escalated to the maximum tolerated dose or to a maximum of 6 x 10(6) U/m2/d. IFN controlled the white blood cell (WBC) counts in 14 of 16 patients who had abnormal counts, and in all six patients with an elevated platelet count. Six patients (33%) have had a complete disappearance of the Ph and two have had a partial response (less than 35% Ph+ metaphases). One patient has a decrease in Ph+ metaphases after 9 months of IFN. Five patients had no significant cytogenetic response after 9 to 12 months, and four developed clinical accelerated phase or blast crisis after 3 to 6 months on therapy. Of four patients with a sex marker, the Ph- population was of donor origin in three and of host origin in one. Clonal cytogenetic abnormalities other than Ph were present in 13 patients and did not predict for lack of response to IFN. IFN is effective in suppressing the Ph clone in some patients who relapse with CML after allogeneic BMT and controls the blood counts in the majority.     

Southern technique and cytogenetics are complementary and must be used together in the evaluation of Ph1, M-BCR positive chronic myeloid leukemia (CML) patients treated with alpha interferon (IFN-ALPHA)

Cytogenetic analysis is the gold standard for the follow-up of CML patients. The sensitivity of cytogenetics is fairly similar to that of Southern detection of M-BCR rearrangement (5%); this last technique has the potential advantage of being independent of cell division and yield of metaphases. IFN alpha treatment can induce lack of growth of hemopoietic precursors and poor yield of metaphases has been observed. For this reason we decided to study the grade of concordance and complementarity between analysis of karyotype and detection of M-BCR rearrangement of Southern blot. We studied 43 Ph1 positive, M-BCR positive pre-BMT CML patients (48 samples) treated with IFN alpha 2a. Karyotype was done on bone marrow cells by direct method, culture, and banding. Southern technique was performed onto DNA from peripheral blood leukocytes treated with Bgill (and Xbal if necessary) and hybridized with the universal probe (Ph1/bcr-3, Transprobe 1) labelled with dCTP32. A highly significant association between both tests was obtained. Of 48 samples analyzed, 34 were evaluable by both methods and 28 gave the same result for both tests. The concordance between the tests was good (kappa index: 0.63). Of total samples 27.1% was not evaluable by cytogenetics; this figure was 31.2% in samples from patients who were previously in complete cytogenetic response. All of the specimens not evaluable by karyotyping were evaluable by Southern. One sample was not analyzable by Southern but it was evaluable by cytogenetic analysis. The Information obtained by Southern technique was clinically relevant, and decisions were made according to its results. We conclude that both tests show a significant association and a good concordance, although they are not interchangeable. Cytogenetic and molecular studies are complementary and must be employed together in CML patients treated with alpha-interferon. © 1996 Wiley-Liss, Inc.     

Therapy-induced Ph1 suppression in chronic myeloid leukemia: molecular and cytogenetic studies in patients treated with alpha-2b IFN, high-dose chemotherapy and autologous stem cell infusion

In this study, cytogenetic and molecular analyses were employed to assess the response to therapy in 29 chronic myeloid leukemia patients undergoing high dose chemotherapy followed by autologous stem cell infusion. Of these, 11 had previously achieved hematologic remission and cytogenetic improvement after alpha-2b interferon (IFN) treatment, whereas 18 underwent autografting in an early phase of the disease. In each case bone marrow samples were examined pre-treatment and at +2, +6 and +12 months in order to verify the degree of Ph1 suppression. In addition, the position of the breakpoint within the BCR region was mapped with multiple restriction enzymes. In 17 cases (59%) a significant Ph1 reduction was observed at +60 days (0-57% residual Ph1+ cells). In three of these cases, a complete cytogenetic response was confirmed at the DNA level by Southern blotting, but specific amplification of the BCR/ABL junction by the polymerase chain reaction (PCR), performed in two cases, still showed residual disease. The remaining 12 patients (41%) revealed a substantial persistence of Ph1+ metaphases (90-100%). Nine of 17 responding patients (53%) showed an increase of Ph1+ cells at 6 months, and five of 20 evaluated had a further increase at 12 months. With the exception of the results seen by PCR, comparison of molecular and cytogenetic techniques did not show significant differences. The variable degrees of Ph1 suppression observed did not appear to be associated with the position of BCR breakpoints. The factors predicting cytogenetic response to IFN and stem cell autograft and long-term durability of cytoconversion should be elucidated in further studies and with longer follow-up.     

Molecular diagnosis of Philadelphia chromosome-positive chronic myeloid leukemia.

BACKGROUND. In virtually all Ph1 chromosome-positive CML patients, the breakpoint on chromosome 22 maps in a very restricted area of 5.8 Kb, which has been named "breakpoint cluster region" or "bcr". Several molecular probes of this region are presently available, and this makes the molecular diagnosis of CML a useful approach which can be particularly important in those cases in which cytogenetic analysis does not reveal the presence of a Ph1 chromosome. Here we report the problems and our experience during the molecular analysis of the 478 patients examined so far. METHODS. Molecular analyses were performed after digestion of the DNA with 2 to 4 restriction enzymes and hybridization with different probes. Individual samples were subjected to PCR since no rearrangements had been obtained with Southern blotting. RESULTS. Rearrangement bands were detected in all the samples examined. In 473 cases the breakpoint was located within the bcr. In one of these cases, it was detected only after PCR analysis, and in two cases only after the use of the PHL/BCR probe. In 5 cases the breakpoint was localized either 5' or 3' with respect to the bcr. CONCLUSIONS. In this paper, the criteria for a correct molecular diagnosis of CML are presented. The "PHL/BCR" probe appeared to be very specific and time-saving, since it required only one digestion to evidence the rearrangement. Our results confirm the high specificity of the breakpoint on chromosome 22 in CML and the relatively rare incidence of molecular variants.     

Cytogenetic and molecular aspects of Ph-positive leukemia

Cytogenetic and molecular aspects of Ph-positive leukemia are described in comparison with those of Ph-positive CML. Chromosomal characteristics of Ph+AL are; 1) mixture of a normal karyotype at diagnosis, 2) frequent combination with +Ph, +21, +6, +8, or -7, 3) recovery of a normal karyotype at remission. Additional chromosome changes at myeloid blast crisis (BC) of CML are characterized by +Ph, i(17q), +8, or +19. Meanwhile, lymphoid BC exhibits +Ph, +21, but not i(17q) or +19. There seems no cytogenetic difference between Ph+AL and lymphoid BC of CML, but i(17q) may be specific for CML BC. Eight patients with Ph+AL were studied with pulsed-field gel electrophoresis (PFGE) to examine the break site within ABL and BCR genes. One case had a M-BCR rearrangement and the remainder a rearrangement upstream of M-BCR. Minor-BCR rearrangement occurs seldom in CML but is detected in approximately a half of the reported cases of Ph+AL. ABL was rearranged within 1st or 2nd intron in all 8 cases. ABL breakpoints appear randomly distributed between exons 1b and 2 in both Ph+AL and CML.     

Philadelphia chromosome-negative chronic myeloid leukaemia: a report of 14 new cases

Summary. The Philadelphia chromosome (Ph) is the cytogenetic hallmark of chronic myeloid leukaemia (CML) and is used to confirm the diagnosis of CML based on clinical and morphological criteria. We investigated 14 patients with features of CML but without detectable Ph chromosome. In seven patients, referred to as BCR⁺, M-bcr/abl rearrangement was detected by polymerase chain reaction (PCR). The seven remaining patients did not have M-bcr/abl rearrangement and are described as BCR. BCR patients were younger, had lower white blood cell counts (WBC) and lower basophilia. Four BCR^- and four BCR⁺ patients underwent blastic transformation (BT), Response to therapy was fairly similar in both populations. According to French-American-British (FAB) Cooperative Leukaemia Group guidelines, all BCR? patients were classified as having classic form CML or‘chronic granulocytic leukaemia’(CGL) when based only on morphological data. This study further confirms the existence of true CML cases without Ph chromosome or M-bcr/abl rearrangement and shows that this entity differs only slightly from classic form Ph⁺ CML. The Ph^-BCR^- subgroup raises two problems. First, the differential diagnosis with atypical CML or CMML, based on morphological data, and secondly, the therapeutic follow-up in the absence of a specific marker. In contrast, the residual disease of Ph?BCR? patients can be monitored by PCR. More advanced molecular and biochemical techniques will be required to understand which molecular mechanisms underlie Ph^-BCR^- CML, resulting in phenotypes sometimes indistinguishable from Ph⁺ CML.     

DETECTION OF REARRANGEMENT WITHIN THE BREAKPOINT CLUSTER REGION OF CHROMOSOME 22 IN THE DIAGNOSIS OF CHRONIC MYELOID LEUKEMIA

Chronic myeloid leukemia (CML) is characterised by the presence of a Philadelphia (Ph) chromosome in approximately 95% of patients. Molecular analysis has shown that the Ph chromosome translocation breakpoints are clustered within 5.8kb on chromosome 22 (breakpoint cluster region or bcr). This has facilitated the diagnosis of CML by nucleic acid hybridisation using probes specific for the bcr to detect DNA rearrangement in this region. Forty patients diagnosed with CML, including four with variant Ph chromosome translocations and three with normal karyotypes were analysed for rearrangement within the bcr. All except one patient with Ph negative CML had rearrangement within the bcr. In contrast, none of the patients diagnosed with other hematological disorders such as the myelodysplastic or myeloproliferative syndromes (16 patients), acute myeloid leukemia (AML) (six patients), acute lymphoblastic leukemia (ALL) (five patients), including Ph positive ALL (two patients), showed rearrangement within the bcr. Analysis for rearrangement within the bcr is useful in the diagnosis of CML, especially when cytogenetic analysis is unsuccessful or in patients with normal karyotypes or variant Ph chromosome translocations.     

Significance and correlations of molecular analysis results in patients with Philadelphia chromosome-negative chronic myelogenous leukemia and chronic myelomonocytic leukemia

PURPOSE: Several investigators have documented a rearrangement of the breakpoint cluster region (bcr) in selected patients with a morphologic diagnosis of chronic myelogenous leukemia (CML) but no abnormality of the Philadelphia chromosome (Ph) by cytogenetic studies. Our intention was to systematically investigate the incidence of the bcr rearrangement in such patients, and to correlate the findings with patient characteristics, response to therapy (especially alpha interferon treatment), and overall prognosis. PATIENTS AND METHODS: Molecular analysis studies were performed in 40 patients with Ph-negative CML (23 patients) and myelomonocytic leukemia (CMML; 17 patients). RESULTS: Rearrangement of the breakpoint cluster region (bcr) was detected in 11 of the 23 patients with Ph-negative CML (48 percent), indicating the presence of the abnormal molecular events in Ph-positive CML without documentation of the Ph cytogenetic abnormality. None of the 17 patients with CMML had the bcr rearrangement. Patients with Ph-negative CML and the bcr rearrangement had characteristics similar to those of patients with Ph-positive disease. These included a younger age, higher white blood cell counts, a higher incidence of thrombocytosis and basophilia, and a lower occurrence of thrombocytopenia. The leukocyte alkaline phosphatase score was not a helpful distinguishing feature. Among 21 patients receiving alpha interferon-based regimens, response to therapy was significantly better among patients with Ph-negative disease and the bcr rearrangement (seven of seven, 100 percent), compared with those without the bcr rearrangement (one of six, 17 percent), or patients with CMML (two of eight, 25 percent) (p less than 0.01). At this time of follow-up, only one of the 11 patients with Ph-negative CML and the bcr rearrangement had died from complications of allogeneic bone marrow transplantation, compared with three deaths among the 12 patients with Ph-negative CML and no bcr rearrangement, and 11 deaths among the 19 patients with CMML. CONCLUSION: We conclude that molecular studies help in better understanding the nosology of Ph-negative CML, and define a subgroup of patients with clinical, therapeutic, and prognostic correlations similar to those of patients with Ph-positive CML.     

甲磺酸伊马替尼治疗120例慢性髓性白血病的临床研究

目的观察甲磺酸伊马替尼（IM）治疗Ph染色体阳性和（或）BCR／ABL基因阳性的慢性髓性白血病（CML）的疗效和安全性。方法对90例Ph染色体阳性和（或）BCR／ABL基因阳性CML慢性期（CP）患者,持续口服IM,400mg／d;30例CML疾病进展期（加速期／急变期）患者,持续口服IM,600mg／d。服药期间定期复查血常规、骨髓细胞学、染色体和（或）BCR／ABL基因等指标,并随访观察。结果（1）CML—CP患者总的完全血液学缓解率（CHR）、完全细胞遗传学缓解率（CCyR）和完全分子遗传学疗效（CMR）分别为73．3％（66／90）、66．7％（60／90）、54．4％（49／90）;治疗前是否接受过干扰素治疗对CHR、CCyR和CMR均无明显影响;服药前病程≤6个月的CMR优于〉6个月者。初次达到CHR的时间与首次达CCyR的时间、首次达CCyR的时间与BCR／ABL首次转阴时间之间均存在相关性,而初次达CHR的时间与BCR／ABL首次转阴时间则无明显相关性。（2）进展期CML患者的CHR、CCyR、CMR分别为43．3％（13／30）、25．9％（7／27）、25．0％（7／28）,总病死率为30．0％（9／30）。（3）年龄≤25岁患者的病死率高于〉25岁者,差异有统计学意义（P〈0．05）。（4）白细胞减少达Ⅲ级者有19例（16．0％）,发生于治疗后5～20周。血小板减少达Ⅲ级者有21例（18．0％）,发生于治疗后3～16周。主要的非血液系统毒性为双下肢水肿、骨痛和皮疹等,但均程度轻微。结论IM对初治CML及经干扰素治疗失败的CML有较高的CHR及CCyR且起效迅速,对CML—CP疗效显著优于进展期;不良反应程度轻微,患者易于耐受。     

Ph1-positive acute lymphocytic leukemia with chromosome 7 abnormalities.

A 56-yr-old woman with acute lymphocytic leukemia showed the presence of a Philadelphia chromosome in 90% of the bone marrow metaphases and in 10% of the peripheral blood metaphases. Part of the long arm of a G22 chromsome was translocated to the long arm of a C9 chromosome. A second cytogenetic abnormality was found in chromosome 7. Monosomy 7 was found in 60% of the marrow and in 20% of the peripheral blood metaphases. Chromosome 7q- was also found in a small percentage of the metaphases examined. Three months later, when the patient was in partial remission, only 10% of the marrow cells showed chromosome 7 monosomy and a Ph1 chromosome. During complete remission, no chromosomal abnormalities were found, except for a high breakage rate. The finding of a Ph1 chromosome in acute lymphocytic leukemia indicates that different precursors, both granulocytic and lymphocytic, may be involved in the Ph1 process.     

Dual rearrangement of immunoglobulin and T-cell receptor genes in blast crisis of CML

Dual rearrangement of immunoglobulin and T-cell antigen receptor (beta, delta) genes was demonstrated in a case of Philadelphia chromosome-positive chronic myeloid leukemia (CML) in blast crisis. The blast cells, showing L2 morphology and high activity of TdT, expressed pre-B cell (CD19+, Ia+) and myeloid (CD13+, CD34+) surface antigens but lacket T-cell antigens (CD2-, CD7-). Cytogenetic studies on bone marrow and peripheral blood revealed the Phl chromosome in all metaphases analyzed, majority of which also had the additional chromosome changes, +8, +10, +21. Furthermore, molecular analysis of the breakpoint cluster region (bcr) on chromosome 22 showed a rearrangement, confirming the CML origin of the blast cells.